All-Trans-Retinoic Acid

Handbook 1

1. Chemical and Physical Solubility Characteristics Soluble in most organic solvents, fats and oils; sparingly soluble in water (0.21 mmol/L) (Szuts 1.1 Nomenclature & Harosi, 1991). See General Remarks, section 1.4 Spectroscopy 1 1.2 Name: all-trans-Retinoic acid UV and visible: max 350 (ethanol), E i , 1510, Chemical Abstracts Services Registry Number EM 45 300 (Frickel, 1984; Barua & Furr, 1998). 302-79-4 Nuclear magnetic resonance

) IUPAC Systematic Name 1HNMR (CDCI3, 220 MHz): ô 1.02 (1-CH3 1 1.47 ) (all-E)-9, 13-Dimethyl-7(1, 1,5-trimethylcyclohex- (2-CH2 1 1.62 (3-CH), 1.72 (5-CH3), 2.01 (9-CH), 5-en-6-yl)nona-7,9, 11, 13-tetraen-15-oic acid (see 2.02 (4-CH2), 2.37 (13-CH), 5.79 (14-H), 6.14 (8- 1.3), or (all-E)-3, 7-dimethyl-9-(2,2,6-trimethylcy- H), 6.15 (10-H), 6.29 (7-H), 6.31 (12-H), 7.03 (11- clohex-1-en-1-yl)nona-2,4,6,8-tetraen-1-oic acid H); J78 (16 Hz), J1011 (11.5 Hz), J 112 (15 Hz) (Schweiter et al., 1969; Vetter et al., 1971; Frickel, Synonyms 1984; Barua & Furr, 1998). Vitamin A acid, vitamin A1 acid, trans-retinoic acid, tretinoin; Retin-A, Aberel, Airol, Aknoten, 13C-NMR (CDCI3, 68 MHz) ô 12.9 (9-CH3), 13.9 Atra, Cordes Vas, Dermairol, Epi-Aberol, Eudyna, (13-CH3), 19.5 (3-C), 21.6 (5-CH3), 29.0 (1,1- Vesanoid. CH,), 33.3 (4-C), 34.5 (1-C), 40.0 (2-C), 118.5 (14-C), 128.7 (7-C), 129.8 (5-C, 10-C), 131.1 (11- 1.3 Structural and molecular formulae and C), 135.5 (12-C), 137.6 (8-C), 138.0 (6-C), 139.3 relative molecular mass (9-C), 153.2 (13-C), 168.6 (15-C) (Englert, 1975; Frickel, 1984; Barua & Furr, 1998). 19 20 16 17 Resonance Raman, infrared and mass spectrometly 7 15 11 COO H (Frickel, 1984; Barua & Fun, 1998).

X-Ray analysis 4 18 (Stam & MacGillavry, 1963; Frickel, 1984).

Composition: C20H2802 Stability Relative molecular mass: 300.45 Unstable to light, oxygen and heat, protected in solution by the presence of antioxidants, such 1.4 Physical and chemical properties as butylated hydroxytoluene and pyrogallol. A variety of factors influence the stability of Description all-trans-retinoic acid in tissue culture media. Yellow crystals from ethanol Degradation and isomerization are minimized by storing under an inert gas, e.g. argon, at -20 °C or Melting-point lower temperatures in the dark (Frickel, 1984; Barua 180-182°C (Budavari et al., 1996) & Fun, 1998).

IARC Handbooks of Cancer Prevention

2. Occurrence, Production, Use, most efficacious oral doses are 1-2 mg/kg bw per Human Exposure and Analysis day (Peck & DiGiovanna, 1994; Vahlquist, 1994), although such doses often induce adverse side- 2.1 Occurrence effects, as discussed in section 2.4. Daily topical The concentration of all-trans-retinoic acid in the doses of up to 0.1% all-trans-retinoic acid in creams plasma of fasting individuals is 4-14 nmol/L or gels are effective in treating acne and photoage- (Blaner & Olson, 1994). Most other tissues of the ing, but adverse side-effects are again common. body also contain all-trans-retinoic acid, at concen- Both the efficacy of all-trans-retinoic acid and the trations of 40-6000 pmol/g wet weight (Napoli, incidence of side-effects are dose-dependent. Thus, 1994; Zhuang et al., 1995). The concentration of retinoids with therapeutic efficacy but little if any all-trans-retinoic acid is < 1% that of all-trans- toxicity are being sought avidly. retinol in human plasma and < 5% that of total Some of the precancerous conditions and can- vitamin A in the tissues of healthy animals and cers treated with all-trans-retinoic acid are summa- humans, and all-trans-retinoic acid is present only rized in Table 2. Oral doses of 0.5-2 mg/kg bw per in traces in plants, if at all. Thus, all-trans-retinoic day have commonly been used, but oral doses of acid is a very minor constituent of the diet. Some 5-10 mg/day have also been given. all-trans- foods, such as dairy products, sugar and comestible Retinoic acid has been approved for use in the oils, have been fortified with vitamin A but not with treatment of acute prornyelocytic leukaemia at a all-trans-reiinoic acid, which, unlike vitamin A and dose of 45 mg/m2 per day, and patients with cervi- carotenoids, is not available as a dietary supplement. cal dysplasia were treated topically with 0.37% all- trans-retinoic acid in a sponge or gel (Hong & Itri, 2.2 Production 1994). Attempts to synthesize retinol were initiated soon after its structure was determined by von Euler and Karrer in 1931. all-trans-Retinoic acid was synthesized by Arens and van Dorp in 1946. The first successful industrial synthesis of all-trans-retinol was devised by Isler in 1947 with the Lindlar cata- lyst. In the 1960s, Pommer and his colleagues used Acne vuigaris the Wittig reaction involving phosphonium salts Cystic acne to devise an elegant new industrial method for the Keloids synthesis of retinol, retinoic acid and 13-carotene in Lichen planus the 1960s. In the early 1970s, Julia and Arnoud Photoaged skin devised an effective synthesis of all-trans-retinoic Psoriasis acid by using the C-15 sulfone as an intermediate a (Frickel, 1984). Other synthetic procedures have Modified from Vahlquist (1994) and from Peck & since been developed which have been used in the DiGiovanna (1994) formation of a large number of related compounds (Frickel, 1984; Dawson & Hobbs, 1994).

2.3 Use all-trans-Retinoic acid is used primarily for treating dermatological disorders (Peck & DiGiovanna, 1994; Vahlquist, 1994), but it has also been used to Actinic keratosis treat several types of human cancer (Hong & Itri, Acute promyelocytic leukemia 1994), both in experimental animals and in Basal-cell carcinoma humans, and to reduce elastase-induced emphy- Cervical dysplasia sema in rats (Massaro & Massaro, 1997). Oral leukoplakia The skin disorders that have been treated with all-trans-retinoic acid are listed in Table 1. The Cited by Hong & Itri (1994)

All- trans- Retinoic acid

2.4 Human exposure butylated hydroxytoluene is also added at the out- As indicated above, the amount of retinoic acids in set to minimize oxidation of the retinoids. the diet is very small, probably in the range of A large number of chromatographic systems 10-100 pg/day. Because all-trans-retinoic acid is have been devised for the separation and quantifi- rapidly metabolized in the body and is not stored cation of all-trans-retinoic acid (Frolik & Olson, in the liver or other organs, it does not accumulate 1984; Furr et al., 1992, 1994; Barua & Furr, 1998; over time (Blaner & Olson, 1994). The amount of Barua etal., 1999). all-trans-retinoic acid ingested in the diet therefore all-trans-Retinoic acid can also be separated as poses neither a benefit nor a risk. As a conse- its methyl or pentafluorobenzyl ester by gas-liquid quence, exposure to all-trans-retinoic acid is or liquid-liquid chromatography and quantified limited, for all practical purposes, to the oral or by mass spectrometry. New ionization methods topical treatment of medical disorders. As indi- and tandem mass spectrometry have further cated in section 2.3, the maximum oral dose is enhanced the sensitivity and selectivity with which approximately 2 mg/kg bw per day. The many retinoic acid can be measured (Barua et al., 1999). adverse side-effects observed at such doses (Kamm et al., 1984; Armstrong et al., 1994) are described in section 7.1. 3. Metabolism, Kinetics and Genetic Topical treatment of acne and photoaged skin Variation with creams or gels containing up to 0.1% all-trans- retinoic acid is common (Peck & DiGiovanna, Information on the metabolism, plasma transport 1994; Vahlquist, 1994). Previously, higher concen- and tissue distribution of all-trans-retinoic acid in trations (0.3-0.4%) were used. humans and animal models after administration of pharmacological doses is summarized below. More 2.5 Analysis information is given in the General Remarks on all-trans-Retinoic acid in plasma and tissues is com- the endogeneous (physiological) metabolism of monly measured by high-performance liquid chro- all-trans-retinoic acid. matography (HPLC) (Barua & Furr, 1998). The plasma is collected in heparinized tubes, and either 3.1 Humans plasma or a tissue homogenate is acidified and 3.1.1 Metabolism then extracted several times with a suitable volume Muindi et al. (1992) studied the metabolism of all- of an organic solvent, such as chloroform and trans-retinoic acid in 13 patients with acute methanol, diethyl ether, dichioromethane, ace- prornyelocytic leukaemia who were receiving the tonitrue, 2-propanol or ethyl acetate. After the drug orally at a dose of 45 Mg/M2.- The only combined extract has been dried with anhydrous metabolite of all-trans-retinoic acid measured in sodium sulfate, the solvent is evaporated to plasma before treatment was all-trans-4-oxo- dryness under yellow light (to avoid isomerization) retinoic acid, which accounted for < 10% of the cir- in nitrogen or argon. The dried powder is immedi- culating all-trans-retinoic acid. The urine of these ately dissolved in the HPLC solvent and injected patients was found to contain all-trans-4-oxo- onto the HPLC column. In some cases, a solid- retinoyl-3-glucuronide, but urinary excretion of phase extraction or elution step is introduced to this compound accounted for < 1% of the admin- remove contaminants. istered dose. No drug was found in the cere- A reversed-phase C18 column is usually used brospinal fluid. for the separation, and the compound is usually detected by measuring the absorption at 350 nm 3.1.2 Kinetics and quantified by measuring the area under the Muindi et al. (1992) also assessed the pharmacoki- absorption peak with an integrator. A known netics of all-trans-retinoic acid. The peak plasma amount of a reference standard, usually all-trans- concentration (347 ± 266 ng/ml) was reached 1-2 retinyl acetate, is added to the tissue, plasma or h after ingestion of the drug, and this decayed in a serum sample to correct for losses during mono-exponential fashion with a half-life of 0.8 ± extraction and analysis. An antioxidant such as 0.1 h. Continued oral administration of all-trans-

97 ARC Handbooks of Cancer Prevention retinoic acid for an additional 2-6 weeks was was available about variations in the metabolism associated with a significant decrease in both the and/or plasma clearance of all-trans-retinoic acid in peak plasma concentration and the integrated area other human populations. under the curve of concentration-time (AUC). For a subset of the patients, this decrease occurred 3.2 Experimental models within the first 7 days after the start of treatment. 3.2.1 Metabolism The decrease was associated with a 10-fold increase After female cynomolgus monkeys were given all- in urinary excretion of a11-trans-4-oxoretinoy1-- trans-retinoic acid orally at a dose of 6.7 pmol/kg glucuronide, suggesting that the accelerated clear- bw per day for 10 days, the concentration of all- ance of all-trans-retinoic acid from plasma was trcins-retinoyl-f3-glucuronide in the plasma rose to a associated with increased drug catabolism. maximum of 231 nmol/L (Creech Kraft et al., In patients with either squamous- or large-cell 1991a). When 13-cis-retinoic acid was similarly carcinomas of the lung, the mean plasma AUC administered, the maximal concentration of value calculated after administration of a single 13-cis-retinoyl-f3-glucuronide was 42 nmol/L. The oral dose of 45 mg/ml was significantly lower than two isomers also partly interconverted, e.g. all- that of patients with adenocarcinomas (p = 0.0001) trans-retinoic acid to 13-cis-retinoic acid and to or control subjects (p = 0.01). Individuals with 13-cis-retinoyl-3-glucuronide and 13-cis-retinoic an AUC value < 250 ng-h/mL had a greater likeli- acid to all-trans-retinoic acid (Creech Kraft et al., hood of having squamous- or large-cell carcinoma 1991b). Creech Kraft et al. (1991a) indicated that (odds ratio = 5.9) (Rigas et al., 1996). [It is unclear the extent of retinoyl-f3-glucuronide formation from these studies whether the phenotype from retinoic acid, as assessed pharmacokineti- for rapid clearance of all-trans-retinoic acid is a cally, is dependent both on the isomer adminis- cause or an effect of the squamous- or large-cell tered and the species studied. lung cancer.] In pregnant females of most but not all species, After administration of all-trans-retinoic acid at all-trans-retinoyl-f3-glucuronide is a major metabo- a dose of 30 Mg/M2 to four children with acute lite in the plasma after administration of all-trans- promyelocytic leukaemia, the peak plasma con- retinoic acid (Creech Kraft et al., 1987, 1991b; centration was 20-741 ng/mL and was reached Eckhoff & Nau, 1990; Eckhoff et al., 1991). In preg- within 60-120 min of administration. The patient nant mice treated with 13-cis-retinoic acid, 13-cis- with the lowest peak plasma concentration did not retinoyl-f3-glucuronide was the most abundant achieve complete remission and had a much plasma metabolite (Creech Kraft et al., 1991b). In higher concentration of all-trans-4-oxoretinoic this study, all-trans-retinoic acid was transferred to acid in plasma than the other three children, who the embryo 10 times more efficiently than 13-cis- underwent remission. The authors concluded that retinoic acid and 100 times more efficiently than accelerated metabolism of all-trans-retinoic acid to 13-cis-retinoyl-f3-glucuronide. When retinoids all-trans-4-oxoretinoic acid plays an important role were injected into the amnion of rat embryos on in its failure to induce remission in cancer patients day 10 of gestation, the concentrations of ail-b-ans- (Takitani et al., 1995a,b). 4-oxoretinoic acid, 13-cis-4-oxoretinoic acid and all-trans-retinoyl-J3-glucuronide required to pro- 3.1.3 Tissue distribution duce the same dysmorphogenic effects as all-trans- No information was available on the tissue distrib- retinoic acid (250 ng/mL) were twofold, 10-fold ution of all-trans-retinoic acid in humans after its and 16-fold higher, respectively (Creech Kraft & administration as a drug. Juchau, 1992). The lack of teratogenicity of all- b-ans-retinoyl-3-glucuronide after oral administra- 3.14 Variations within human populations tion of very high doses to pregnant rats seems to be The studies of Rigas et al. (1996) and Takitani et al. due to its relatively slow absorption from the (1995a,b) suggest that healthy individuals and intestine, its slow hydrolysis to all-trans-retinoic patients with various types of cancers may have acid, its relatively inefficient transfer across the different capacities for the metabolism and plasma placenta and its inherently low toxicity (Gunning clearance of all-trans-retinoic acid. No information et al., 1993). all-trans-Retinoyl-13-glucuronide was

98 All-trans-Retinoic acid more teratogenic at equimolar doses than 37% after phenobarbital. Pretreatment with 3- all-trans-retinoic acid after subcutaneous applica- methylcholanthrene did not affect the disposition tion to mice on day 11 of gestation. This effect of all-trans-retinoic acid (Kahn et al., 1984) appears to be due to the extensive hydrolysis of all- A dose of 25 mg of all-trans-retinoic acid was trans-retinoy1--glucuronide after subcutaneous administered by intravenous infusion over 30 s and intravenous administration, suggesting that it into the cephalic vein of four anaesthetized male is a precursor of all-trans-retinoic acid when dogs with bile-duct cannulae. The concentration administered by these routes (Nau et al., 1996). of all-buns-retinoic acid in blood over time was biphasic, with an estimated elimination half-life of 3.2.2 Kinetics 4.5 h, an apparent volume of distribution of 1 L/kg After intravenous administration of all-buns- bw and a blood clearance rate of 23 mL/min. The retinoic acid to male DBA mice at a dose of 10 mean AUC was 1190±330 pg-min/mL. At 4 h after mg/kg bw, the serum concentrations showed a dis- administration, only 0.63% of the dose was tribution phase that decreased rapidly over 30 min recovered in the bile, about 25% of which was and was followed by a non-exponential phase. The unconjugated, the remainder occurring as a mean serum concentration of all-buns-retinoic conjugated derivative. Only 0.04% of the dose was acid was 17 ± 1.1 pg/mL 5 min after treatment and recovered in the bile as 13-cis-retinoic acid in the 4 <0.1 pg/mL 6h after injection. The concentrations h after infusion of all-trans-retinoic acid (Patel et of all-trans-retinoic acid in liver, kidney, lung, brain al., 1982). and small intestine were generally higher than Cynomolgus monkeys were given all-trans- those in serum throughout the study. By 8 h after retinoic acid at doses of 2 or 10 mg/kg bw for 10 injection, the brain still contained relatively high days. The maximum mean plasma concentration concentrations of all-trans-retinoic acid (1.8 ± 0.2 of animals receiving 2 mg/kg bw was 420 ± 100 pg/g tissue), even though the dose had been effec- ng/ml on day 1 and 210 ± 10 ng/ml on day 10, tively cleared from the circulation (Wang et al., while that of animals receiving 10 mg/kg bw was 1980). 1200 ± 345 ng/ml on day 1 and 460 ± 125 ng/ml Fasted female B6D2F1 mice received all-buns- on day 10. The mean plasma AUC value was 928 ± retinoic acid intragastrically at a dose of 10 mg/kg 233 ng-h/mL on day 1 and 432 ± 196 ng-h/mL by bw, and clearance was followed for up to 12 h. all- day 10 in animals at 2 mg/kg bw and 4607 ± 1194 trans-Retinoic acid was detected in the plasma by a ng-h/mL on day 1 and 1557 ± 484 ng-h/mlL on more sensitive HPLC procedure within 30 min of day 10 for animals given 10 mg/kg bw. Thus, the administration; the plasma concentration was AUC values were proportional to the dose adminis- essentially constant for the first 4 h but decreased tered (Creech Kraft et al., 199 la). exponentially from 5-9 h after dosing. Sub- sequently, the compound was not detected at con- 3.2.3 Tissue distribution centrations higher than those present endoge- In mice, significant quantities of all-trans-retinoic nously in mouse plasma. The authors estimated acid were observed in all tissues examined (liver, that the half-life of all-trans-retinoic acid was 0.5 h kidney, lung, brain, testis and small intestine) after (McPhillips et al., 1987). administration of 10 mg/kg bw intravenously. In a study of the effects of pretreatment of male The highest concentrations were found in liver at BDF1 mice with phenobarbital (80 mg/kg bw each time studied between 5 and 480 mm, fol- intraperitoneally for 3 days), 3-methylcholan- lowed by kidney, in which the concentrations were threne (40 mg/kg intraperitoneally for 3 days) or about 70% of those in liver. The testis took up the all-buns-retinoic acid (10 mg/kg intragastrically for least, accounting for 5-15% of the concentration 3 days) on the disposition of an orally adminis- observed in liver (Wang et al., 1980). tered dose of 10 mg/kg bw of all-trans-retinoic acid, The AUC values in mice after an oral dose of all- the AUC values for serum and for liver, lung, small trans-retinoic acid were reported for liver, lung, intestine, kidney, spleen, large intestine, fat, heart, small intestine, kidney, spleen, large intestine, fat, brain, muscle, testis and bladder were reduced rela- heart, brain, muscle, testis and urinary bladder. All tive to those of controls by an average of 54% after tissues took up the retinoid (Kahn et al., 1984). pretreatment with all-trans-retinoic acid and by 99 IARC Handbooks of Cancer Prevention

3.2.4 Intra- and inter-species variation received the vehicle. Treatment with 0.05% As discussed in section 3.2.1, different species have retinoid resulted in a rate of regression of 42%, very different capacities for the metabolism and whereas the rate in the controls was 34% (not sig- clearance of pharmacological doses of all-trans- nificant). At the higher dose, a statistically signifi- retinoic acid. No one species appears to reflect the cantly higher rate of regression of lesions was seen situation in humans. among patients receiving all-trans-retinoic acid (55%) than among those given the vehicle (41%; p <0.001) (Kligman & Thorne, 1991). [The Working 4. Cancer-preventive Effects Group noted the inadequate reporting of the study, that the rate of spontaneous regression in 4.1 Humans the control group was high and that actinic 4.1.1 Epidemiological studies keratoses may regress spontaneously.] No data were available to the Working Group. The effects of all-trans-retinoic acid in patients with dysplastic naevi have been evaluated in two 4.1.2 Intervention trials studies. In one trial (Edwards & Jaffe, 1990), eight No data were available to the Working Group. patients were randomly assigned to topical treatment with 0.05% all-trans-retinoic acid and 13 received 4.1.3 Intermediate end-points placebo. Five treated patients and 11 given placebo 4.1.3.1 Skin completed the four-month intervention, and their The use of all-trans-retinoic acid and etretinate was lesions were biopsied. The authors reported marked studied in the treatment of patients who had changes in the clinical and histological appearance received renal transplants and who had more than of naevi in three of the five evaluable treated patients 50 skin lesions, consisting of actinic keratosis, and in none of the 11 controls (p < 0.001). [The squamous-call carcinomas of the skin and warts. Working Group noted that losses from the treatment Seven patients received all-trans-retinoic acid topi- group and the unspecified methods of statistical cally plus etretinate systemically (10 mg/day), and analyses complicate interpretation of this report]. four patients received it alone. After three months A second trial (Halpern et al., 1994) involved of therapy, six of seven patients receiving ail-trans- five male patients with multiple dysplastic naevi retinoic acid plus etretinate and three of four of who received applications of a 0.005% solution of those receiving all-bans-retinoic acid alone showed ail-trans-retinoic acid on the right or left half of the clinical improvement, on the basis of at least a 25% back, the side being chosen at random. Treatment decrease in the number of apparent actinic ker- was continued for six months, at which time all atoses and a reduction in the size of warts. After six naevi were assessed clinically and four naevi were months of therapy, three of four evaluable patients excised from each side and examined for histolog- receiving the two retinoids and two of three receiving ical appearance. A statistically significant (p < all-trans-retinoic acid alone showed at least a 50% 0.0001) improvement in the clinical appearance of decrease in the number of lesions or in the number naevi on the treated side of the back was reported. of new actinic keratoses or squamous-call carcinomas Four of the 16 excised treated and 13 of the of the skin (Rook etal., 1995). [The Working Group 16 untreated naevi met histological criteria for dys- noted that no control group was included and that plasia. The histological results for naevi from one actinic keratoses may regress spontaneously.] patient who did not finish the course of treatment Two randomized trials were conducted of the were not reported. use of topical all-trans-retinoic acid to reverse actinic keratoses. In both studies, patients were 4.1.3.2 Uterine cervix assigned randomly to the retinoid or to the vehicle, In a randomized trial, ail-trans-retinoic acid or and treatment was continued for six months. In placebo was given topically to 301 patients with one study, 266 patients were given 0.05% ail-trans- moderate cervical intra-epithelial neoplasia (n = retinoic acid and compared with 261 patients 151), or severe cervical intra-epithelial neoplasia or given the vehicle; in the second study, 226 patients dysplasia (n = 150) as a 0.372% solution on a colla- were given 0.1% all-trans-retinoic acid and 229 gen sponge in a cervical cap daily for four days and

100 All-trans-Retinoic acid then daily for two days after three and six months. log rank analysis). In the same study, 25 mice The patients were evaluated by serial colposcopy, received all-trans-retinoic acid topically at a con- cytology and cervical biopsy. The dose, schedule centration of 30 nmol twice weekly for 28 weeks. and delivery system were determined in prior sin- The incidence of papillomas was enhanced from gle-arm phase I and II trials (Meyskens et al., 1983; 4% in controls to 58% (p < 0.01, log rank analysis) Graham et al., 1986). A total of 52 patients were (McCormick et al., 1987). lost to follow-up. Among the 141 patients with Groups of 30 male and 30 female hairless albino moderate dysplasia, a higher rate of complete mutant mice received daily topical treatment with response was observed in those receiving all-trans- 0.001% or 0.01% all-trans-retinoic acid from 7 to retinoic acid (43%) than in the group given 30 weeks of age. From day 15 of treatment, the placebo (27%; p = 0.041). No significant difference mice were exposed daily for 2 h to simulated sun- in the rates of regression of dysplasia were seen light from a 6000-W Xenon-arc lamp for 28 weeks. among treated and untreated patients with severe At the end of the experiment at 55 weeks, the dysplasia. Signs of acute toxicity were infrequent, tumour multiplicity was 1.2 carcinomas per mouse mild and reversible, consisting primarily of local in controls and 6.1 and 10 in the two groups given (vaginal and vulvar) irritation and occurring in less all-trans-retinoic acid. The cumulative tumour than 5% of treated subjects (Meyskens et al., 1994). incidence (% tumour-bearing animals) was 45% in [The Working Group noted the uncertain compli- controls, 100% at the low dose and 94% at the ance of the patients lost to follow-up, which limits high dose (Forbes et al., 1979). [The Working the interpretation of the results of this trial.] Group noted the lack of statistical analysis.] Groups of 30 female Sencar mice, six weeks of 4.2 Experimental models age, received a single topical application of 10 4.2.1 Cancer and preneoplastic lesions nmol/L DMBA in acetone, a dose that does not These studies are summarized in Table 3. induce skin papillomas. Subsequently, the mice received twice weekly applications of 2 [tg of 12-0- 4.2.1.1 Skin tetradecanoylphorbol 13-acetate (TPA) and Female Swiss albino mice weighing 20-22 g were all-trans-retinoic acid at doses of 1 and 10 tg for treated with 150 pg of 7,12-dimethylbenz[a]- the remainder of the experiment of 18 weeks. The anthracene (DMBA) by local application for initia- incidence of papillomas was 100% in controls and tion of skin papillomas. After three weeks, croton 76% and 50% at the low and high doses of oil (0.5 mg in acetone) was applied twice weekly all-trans-retinoic acid, respectively. The multiplic- for three to eight months as a promoter. This treat- ity of papillomas was reduced from 7.4 per mouse ment induced four to eight papillomas per mouse. in controls to 3.5 and 1.4 per mouse, respectively. all-trans-Retinoic acid was given at a dose of 200 or In a second part of the study, all-trans-retinoic acid 400 mg/kg bw by intraperitoneal injection or gav- had no effect on two-stage tumour promotion, age once a week for two weeks. The sum of the tested by treating initiated skin with 2 pg of TPA diameters of the papilloma was determined for twice a week for two weeks and subsequently with each mouse and the average value calculated for 2 pg of mezerein twice a week for 18 weeks. The each group. Treatment with all-trans-retinoic acid mice receiving both TPA and mezerein had a reduced the average of the papilloma diameters per papilloma incidence of 92%, with 4.2 papillomas animal from 25 to 16 mm and from 22 to 11 mm per mouse. Treatment with 10 pg of all-trans- at the two doses, respectively (p < 0.05, Student's t retinoic acid during TPA application (stage I pro- test) (Bollag, 1974). motion) had little or no effect (88% papilloma Groups of 25 female Sencar mice, seven to eight incidence and 4 papillomas per mouse), whereas weeks of age, were treated topically with 5 pg of treatment with all-trans-retinoic acid during mez- DMBA for initiation and two weeks later received erein application (stage II promotion) inhibited either basal diet (controls) or a diet supplemented papilloma development (34% papilloma incidence with 40 mg/kg all-trans-retinoic acid. The tumour and 0.8 papillomas per mouse) (Slaga et al., 1980). incidence 30 weeks after initiation was 4% in con- [The Working Group noted that no statistical trois and 68% with all-trans-retinoic acid (p < 0.01, analysis was given.]

101 Table 3. Effects of all-trans-retinoic acid on carcinogenesis in animals

Cancer Species, sex, No. of Carcinogen, dose, route all-trans- Duration in Incidence Multiplicity Efficacy Reference site age at animals Retinoic acid relation to Control Treated Control Treated carcinogen per group dose, route carcinogen Cn treatment o a

Skin Swiss albino mice, 11 150 ig DMBA + 0.5 200 mg/kg For 2 wks after 100 100 NA NA Reduced Bollag (1974) female ig croton oil 2 x wk bw, i.p. papillomas tumour size for 3-8 months 400 mg/kg developed 100 100 NA NA CD bw, orally

Skin Hairless albino mice, 60 2 h/day UVR exposure 0.001%, —2 to + 30 45 100 1.2 6.1 Tumour Forbes et al. male and female for 28 As 0.01% wks 45 94 1.2 10.0 enhancing (1979) topically effect

Skin SENCAR mice, 30 10 nmol DMBA + 1 ig + 1 wk to end 100 76 7.4 3.5 Effective Slaga etal. female, 6 wks TPA for 18 wks 10 Ag 100 50 7.4 1.4 Effective (1980) TPA (2 wks) + 10 tg + 1 wk to +3 92 90 4.2 4.5 Ineffective mezerein 18 wks TPA (2 wks) + 10 ig + 3 wks to end 92 38 4.2 1.0 Effective mezerein 16 wks topically

Skin SENCAR mice, 30 10 nmol DMBA + 5 ig + 1 wk to end 100 90 10.0 6* Effective Fischer et at. female, 7 As 2 lag TPA 3 x/wk/13 20 [tg 100 90 10.0 6 Effective (1985) wks topically

30 10 nmol DMBA 5 ILg + 2 to 24 wks 0 25 0 0.5 Tumour 20 ig 0 50 0 0.9 enhancing topically effect

30 10 nmol DMBA 5 lag + 2 tg + 1 t 3 wks 17 37 0.3 1.3 Tumour mezerein enhancing 10fig+2.tg + ito3 wks 17 43 0.3 1.6 effect mezerein

Skin CD-i, female, 5-7 30 200 nmol DMBA + 1.7 nmol + 2 wks to end 64 41 1.5 NA Effective Dawson et al. As 444 nmol anthralene 17 nmol 64 34* 1.5 NA Effective (1987) daily/32 wks 170 nmol 64 28* 1.5 NA Effective for 32 wks % (conte

Skin SENCAR mice, 25 5 gg DMBA 40 mg/kg diet + 2 AS to end 4 68* NA NA Tumour McCormick et at female, 7-8 wks 30 nmol enhancing (1987) topically effect 2 x wk + 2 wks to end 4 58* NA NA Tumour enhancing effect Skin SENCAR mice, 24 20 nmol DMBA + 17 nmol + 2 wks to end 67 38* 5.3 0.7* Effective Verma (1988) female, 6 wks 3.3 nmol TPA 2 wks topical as Inhibitor + 2 mmol diacyl- of 2nd-stage glycerol for 17 wks promotion

Effective* Skin SENCAR mice 30-40 20 ixg DMBA + TPA 3 jig/kg diet O to 45 wks 50 07 Chen eta! (1994) 3 wks, male and 2 jig once a wk 30 jig/kg diet 18.5 0.2* female for 20 wks 3/30 jig/kg diet 23.1 0.2* 30/3 jig/kg diet 23.1 02 Liver B6D2F1/Hsd 35 50 mg NDEA ip 30 mg/kg diet + 1 week to 37 86 NA NA Tumour McCormick et al mice female 4 As 100 mg NDEAip end at 6 mths 44 90 NA NA enhancing (1990) effect Mammary Srague Dawley rats 12-24 MNIU 50 mg/kg bw 60 mg/kg diet + ito 45 mths 100 91 3.6 33 Ineffective Anzano eta! gland female, 50 days 120 mg/kg diet 100 83 3.6 2.8 (1994) wk, week; DMBA, 7,12-dimethylbenz[a]anthracene; TPA, 12-0-tetradecanoylphorbol 13-acetate; NDEA, N-nitrosodiethylamlne; ip, intraperitoneal; NA, not available; MNU N-methyl N nitrosourea * Statistically significant (see text) * Conversion of papilloma to carcinoma was inhibited [ARC Handbooks of Cancer Prevention

In similar studies, Sencar mice received topical high doses of all-b-ans-retinoic acid (p < 0.01, applications of a single dose of 10 nmol/L DMBA Student's t test) (Dawson et al., 1987). and then 5 or 20 pg of all-trans-retinoic acid simul- Pregnant Sencar mice were placed on diets con- taneously with 2 pg of TPA thrice weekly for 13 taining all-trans-retinoic acid at 3 or 30 pg/g of weeks. Both doses of all-trans-retinoic acid reduced diet. Their pups were raised on the same diets, were the tumour yield, from approximately 10 per initiated with a single dose of 20 pg DMBA at three mouse in controls to 6 per mouse, and the papil- weeks of age and promoted with 2 pg of TPA once loma incidence was 100% and 90%, respectively. a week for 20 weeks. At that time, half of the ani- The authors reported that papilloma development mals given the diet containing all-trans-retinoic was delayed in the animals given all-trans-retinoic acid at 3 pg/g were switched to the diet containing acid. In the same series of experiments, all-trans- 30 pg/g, and half of those given 30 pg/g were retinoic acid was applied instead of TPA to the skin switched to the diet containing 3 pg/g. The of Sencar mice initiated with 10 nmol/L DMBA. papilloma incidences in the four groups were not After 24 weeks, the papilloma yield was about 0.5 significantly different, but the carcinoma inci- papillomas per mouse at 5 pg of all-trans-retinoic dence and yield were significantly lower in the acid and 0.9 papillomas per mouse at 20 pg, with three groups that were maintained either continu- tumour incidences of about 50% and 25%, respec- ously or for some period on the diet containing all- tively. In another experiment, 2 pg of mezerein trans-retinoic acid at 30 pg/g (p < 0.05, Fisher's were applied to the skin of mice initiated with 10 exact test). When the animals were 26 weeks of nmol/L DMBA both as a first-stage promoter three age, 27-40 in each group were still alive; the exper- times per week for two weeks and as a second-stage iment was terminated when they were 45 weeks promoter three times per week for the subsequent old. The cumulative carcinoma incidence was 50% 15-18 weeks. The papilloma yield per mouse was in animals maintained continuously on the diet 0.3, and the papilloma incidence was 17%. When with the low concentration of all-trans-retinoic 10 pg of all-trans-retinoic acid were applied instead acid and 18-23% in animals kept continuously or of mezerein during the first stage of promotion, for some period on the diet with the high concen- the papilloma yield was 1.6 per mouse and the tration. The carcinoma yield was 0.68 in the mice incidence was 43% per mouse (Fischer etal., 1985). maintained continuously at the low dose and [The Working Group noted that no statistics were 0.19-0.23 in animals maintained continuously or given, and the papilloma yields and incidences intermittently at the high dose (Chen et al., 1994). were gleaned from graphs.] In another two-stage tumour promotion study 4.2.1.2 Liver in female SENCAR mice initiated with DMBA, TPA Groups of 35 female B6D2F1/hsd, mice, four weeks was applied as a stage-I promoter and L-a-dioc- of age, received intraperitoneal injections of 50 or tanoylglycerol (a protein kinase C inducer) as a 100 mg N-nitrosodiethylamine (NDEA) and stage-II promoter. all-trans-Retinoic acid (17 dietary supplements of 0.1 mmol of all-trans- nmol/L) was topically applied 1 h before L-Œ-dioc- retinoic add per kg of diet beginning one week after tanoylglycerol. The papilloma incidence at 17 carcinogen treatment until the end of the study at weeks was 67% in controls and 38% in mice given six months. The combined incidence of benign all-trans-retinoic acid [no statistics given], and the and malignant liver tumours in animals given the tumour multiplicity was 5.3 and 0.3, respectively low dose of NDEA was 37% in controls and 86% in (p < 0.01 [method not given]) (Verma, 1988). those given all-trans-retinoic acid < 0.05; z2 test). Groups of 30 female CD-1 mice, five to seven The incidence of hepatocellular carcinoma in weeks of age, were treated topically with 200 animals at the high dose of NDEA was 44% in con- nmol/L DMBA in acetone; two weeks later, the trols and 90% with all-trans-retinoic acid < 0.01; mice were treated with 444 nmol/L anthralene X2 test). Since all-trans-retinoic acid alone did not alone or with 1.7, 17 or 170 nmol/L all-trans- induce any liver tumours, these results suggest that retinoic acid for 32 weeks. The incidences of skin it enhanced the hepatocarcinogenicity of NDEA papillomas were 64% in the control group and (McCormick et al., 1990). 41%, 34% and 28% at the low, intermediate and

104 All-trans-Retinoic acid

4.2.1.3 Mammary gland are often serum-free, have been developed to cul- Groups of 24 control and 12 treated female ture epithelial cells and exclude mesenchymal Sprague-Dawley rats, 50 days of age, received intra- (stromal) cells. Investigations of the effects of venous injections of 50 mg/kg bw N-methyl-N- retinoids on normal cells included studies on nitrosourea and, one week later, all-trans-retinoic changes in cell growth and differentiation and on acid at 60 or 120 mg/kg of diet for 4.5 months. The the prevention of malignant transformation. incidences of mammary adenocarcinoma were Because many of the cells in epithelial tissues in 100% in controls and 83% and 91% at the high vivo are quiescent, adaptation of culture conditions and low concentrations of all-trans-retinoic acid, to maximize cell proliferation may select for cells respectively. The tumour multiplicity was 3.6 in of higher proliferative capacity or allow the cells to controls and 3.3 and 2.8 with all-trans-retinoic exhibit an acquired proliferative potential. Pro- acid, respectively. The differences were not statisti- liferating normal cells in culture can be considered cally significant (Anzano et al., 1994). to be hyperplastic cells.

4.2.2 Intermediate biomarkers (a) Inhibition of carcinogen-induced neoplastic Omithine decarboxylase is considered to be a use- transformation ful biomarker in experimental studies of skin car- In studies with immortalized murine C3H/10 T1/2 cinogenesis. Mice were given 0.2 mmol of DMBA murine fibroblasts, all-trans-retinoic acid inhibited in 0.2 mL of acetone as an initiator followed by 3-methylcholanthrene-induced neoplastic trans- twice weekly applications of 17 nmol/L TPA topi- formation when it was added to the medium seven cally 1 h after application of 1.7 or 17 nmol of all- days after removal of the carcinogen and weekly trans-retinoic acid in 0.2 ml of acetone. The mice treatments were given for the four-week duration were killed 4.5 h after the last of seven treatments of the experiment. Activity was thus expressed in with TPA, and ornithine decarboxylase was mea- the promotion phase of transformation and sured. all-trans-Retinoic acid suppressed the TPA- required a concentration of about 104 mol/L induced ornithine decarboxylase activity almost (Bertram, 1980). The low activity was explained by completely (Verma et al., 1979). the finding that these cells rapidly catabolized all-trans-retinoic acid. When this was blocked by 4.2.3 In-vitro models liarazole, an inhibitor of a cytochrome P450 4.2.3.1 Models of carcinogenesis 4-hydroxylase, all-trans-retinoic acid inhibited Studies with cells in culture have provided impor- transformation at concentrations as low as 10-10 tant information on the pleiotropic effects of mol/L, in the absence of cytoxicity (Acevedo & all-trans-retinoic acid that may be relevant for Bertram, 1995). understanding the mechanisms of its chemopreventive effects. The types of cell that have been (b) Rat tracheal epithelial cells used to study the effects of retinoids include Primary rat tracheal epithelial cells grown in an normal cells in short-term culture, cells immortal- air—liquid interface in the presence of all-buns- ized spontaneously or by viral genes such as HPV retinoic acid differentiate into normal mucociliary 16 E6 and SV40 large T antigen or oncogenes such epithelium and produce large amounts of mucin as H-ras, and cells derived from solid tumours or glycoproteins (Kaartinen et al., 1993). The differen- haematological malignancies and used in primary tiated cultures were shown to express the mucin cultures or established as cell lines. Although some genes MUGi and MUGS (Guzman et al., 1996). important information was gained from each of After removal of all-trans-retinoic acid from the these cell systems, that obtained with non-malig- medium, the cells assumed a stratified squamous nant cells is more relevant to chemoprevention of morphology and developed a cornified apical cancer. A wide range of concentrations (10-11_104 layer. Biochemical analysis revealed loss of expres- mol/L) was used in these studies. sion of transglutaminase type II, keratin 18 and Normal epithelial cells can be maintained in both MUC1 and MUC5 and aberrant expression of culture for a limited number of cell divisions, as the squamous markers transglutaminase type I and they usually senesce and die. Specific media, which keratin 13 (Kaartinen et al., 1993; Guzman et al.,

105 IARC Handbooks of Cancer Prevention

1996). Addition of all-trans-retinoic acid to squa- that constrain proliferation, and most of their mous differentiated rat tracheal epithelial cultures descendants differentiate and do not express trans- resulted in a rapid (24 h) down-regulation of formed characteristics. These are the cells that prostaglandin H synthase-1 (PGHS-1) mRNA respond to all-trans-retinoic acid. Progression of expression and a slower (three days) up-regulation the MNNG-initiated cells to the second stage of of the expression of cytosolic phospholipase A2 transformation, when the cells are immortalized, is and PGHS-2 genes coincident with re-differentia- accompanied by loss of responsiveness to the tion of the culture to a mucociliary phenotype growth inhibitory effects of all-trans-retinoic acid. (Hill et al., 1996). In this model, early stages of transformation are The rat tracheal epithelial cell system is useful likely to respond better than later stages (Fitzgerald for identifying potential chemopreventive agents et al., 1986; Nettesheim et al., 1987). because the cells can be transformed by exposure Rat tracheal epithelial cells can also be trans- to chemical carcinogens such as the directly acting formed by benzo[a]pyrene. Inhibition of transfor- N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). mation by this carcinogen was developed as an Exposure of primary rat tracheal epithelial cells in assay for screening chemopreventive agents that vitro to MNNG led to the appearance of initiated act by altering metabolism or by inhibiting early stem cells that grew under selective conditions in stages of carcinogenesis. all-trans-Retinoic acid was culture and differed from normal stem cells in that active in this assay when added simultaneously their probability of self-renewal was increased with benzo[a]pyrene, due either to increased (Nettesheim et al., 1987). When all-trans-retinoic cytochrome P450 activity or restoration of differ- acid was included in the medium for only three entiation (Steele et al., 1990). days at concentrations that did not affect cell sur- Immortalized rat tracheal epithelial 2C5 cells vival (3-33 nmol/L), it inhibited transformation by cultured in serum-free medium undergo squamous 65-75% in a dose-dependent manner. Longer differentiation after the addition of serum. treatment at higher concentrations caused more Concentrations of 0.1-1 nmol/L all-trans-retinoic than 90% inhibition, with no cytotoxicity. When acid inhibited this differentiation, as evidenced by treatment was delayed for three weeks after expo- suppression of several markers, including cross- sure to MINNG, 60% inhibition of transformation linked envelope formation and keratin K13 expres- frequency was still achieved. all-trans-Retinoic acid sion (Denning & Verma, 1994). inhibited the growth of normal rat tracheal epithelial cells. It was suggested that the mechanism of (c) Immortalized and transformed human the preventive effect of all-trans-retinoic acid on bronchial epithelial cells tracheal cell transformation was inhibition of cell Normal bronchial epithelial cells were immortal- proliferation. Exposure of the rat tracheal epithe- ized by SV40 large T antigen by Reddel et al. (1988) lial cells to MNNG for more than five weeks and designated BEAS-213 cells. The cells were then resulted in loss of sensitivity to the growth used to develop transformed and tumorigenic inhibitory effect of all-trans-retinoic acid. This was derivatives by culturing them on de-epithelialized deduced from the finding that the concentration rat tracheas, transplanting them into rats and of all-trans-retinoic acid required to cause 50% exposing the rats to cigarette smoke condensate. inhibition of colony formation increased from Cell lines were derived from tumours which 0.1-0.3 nmol/L for cells isolated from 3-5-week- developed in the transplanted tissue in some old transformed colonies to over 100-times higher animals. Certain cell lines were considered to be concentrations for cells isolated from 12-week-old premalignant, while others, such as 1170-I cultures. Rat tracheal epithelial cell lines cells, were tumorigenic and considered to be established from cells in advanced stages of trans- malignant (Klein-Szanto et al., 1992). The effects of formation also showed increased resistance to all- retinoids were compared in primary cultures of trans-retinoic acid, and two of five cell lines even normal bronchial epithelial cells, the immortalized formed more colonies in its presence (Fitzgerald et BEAS-2B cell line and premalignant and malignant al., 1986). In this model, cells in early stages of cell lines in a model of multistage tracheo- transformation retain responsiveness to factors bronchial carcinogenesis. The sensitivity to the

106 All-trans-Retinoic acid growth inhibitory effects of all-trans-retinoic acid of the keratinocyte cell line 308, derived from diminished with progression in this cell system: adult mouse skin, to DMBA. These cells behaved the most advanced cell line 1170-I was resistant, like initiated cells in that they formed papillomas whereas the growth of normal and immortalized when grafted onto the backs of athymic mice. cells was inhibited (Kim et al., 1995; Lee et al., Normal keratinocytes can normally inhibit the 1997). colony-forming ability of these cells in a medium In another model for carcinogen-induced trans- containing a high concentration of Ca, but expo- formation in vitro (Langenfeld et al., 1996), SV40-T- sure to TPA for several weeks allowed initiated immortalized human bronchial epithelial BEAS-2B colonies to form. This action of TPA could be cells are exposed to the carcinogenic agents present blocked by all-trans-retinoic acid at 10 mol/L in cigarette smoke condensate or to the purified (Hennings et al., 1990). tobacco carcinogen N-nitrosamino-4-(methylni- In another model, treatment of the murine epi- trosamino)-1-(3-pyridyl)-1-butanone (NNK), and dermal cell line JB6 with the tumour promoter TPA transformation is scored as increased anchorage- resulted in transformation into anchorage-inde- independent growth or acquired tumorigenicity in pendent tumorigenic cells, which was blocked by immune-compromised mice. When the BEAS-2B all-trans-retinoic acid at doses of 10_10_10_6 mol/L cells were treated with all-trans-retinoic acid during (De Benedetti et al., 1991). exposure to the transforming agents, the ability of the cells to form colonies in semi-solid media (e) Human papillomavirus type 16-immortalized and to form tumours was inhibited. all-trans- human epidermal keratinocytes Retinoic acid inhibited DNA synthesis in immor- The transforming ability of human papillomavirus talized BEAS-2B cells and in their carcinogen- (HPV) type 16 (HPV16), which has been implicated transformed derivative BEAS-2BNNK (Boyle et al., in the development of cervical cancer, resides in 1999). the oncogenes E6 and E?. HPV-16 DNA was used to In human tracheal gland epithelial cells immor- transfect human foreskin epidermal keratinocytes talized by adenovirus 12-simian virus 40 (Ad12- and thus obtain several immortalized cell lines. SV40) hybrid, all-trans-retinoic acid inhibited both Treatment of normal keratinocytes with all-trans- cell proliferation and anchorage-independent retinoic acid at 1 nmol/L, during or immediately growth in a dose-dependent manner when applied after transfection with HPV-16 DNA, inhibited at concentrations of 1 nmol/L to 1 pmol/L. all- immortalization by about 95% (Khan et al., 1993). trans-Retinoic acid up-regulated p53 but had no If the cells were first immortalized, all-trans- effect on the expression of TGF-a or TGF-f3 1 genes. retinoic acid inhibited their growth by reducing These results suggest that all-trans-retinoic acid the expression of the HPV-16 early genes (E2, ES, regulates the growth of human tracheal gland E6 and E7) at the level of mRNA and epithelial cells by up-regulating the expression of protein (Pirisi et al., 1992; Khan et al., 1993). The p53 (Joiakim & Chopra, 1993). HPV-16-immortalized cells were about 100 times [The Working Group noted that the relevance more sensitive than their normal counterparts to of these cell culture models is uncertain, since growth inhibition by all-trans-retinoic acid in both the original immortalizing agent, SV40 large T clonal and mass culture growth assays. They were antigen, is not an etiological agent for human lung also more sensitive to modulation of keratin cancer. Since one of the main effects of the large T expression than normal cells. antigen is to decrease p53 levels, the findings may This model was developed further to include be relevant only to carcinogenesis that involves more advanced stages of transformation by contin- defects in the p53 pathway. The immortalized uous culture, which resulted in the selection of cells expressed only low levels of wild-type p53 and variants that acquired independence from not mutated p53 as many human lung cancers do.] epidermal growth factor and growth factors present in bovine pituitary extract, which are required (d) Mouse epidermal keratinocytes at early stages of transformation. The advanced A cell culture model system analogous to initiated stage cells could be transformed into tumorigenic mouse epidermis was established by exposing cells cells by transfection with viral Harvey ras or herpes

107 ARC Handbooks of Cancer Prevention

simplex virus type II DNA. all-trans-Retinoic acid ectocervical cells (Sizemore & Rorke, 1993). It inhibited the early stages of this progression, but suppressed the differentiation markers keratins KS the cells lost their sensitivity as they progressed in and K16 and transglutaminase type 1 more effec- culture (Creek et al., 1995). all-trans-Retinoic acid tively in HPV-immortalized cells than in normal induced TGFI31 and 132 expression in these cells. ectocervical cells (Choo et al., 1995). TGF13 was a potent inhibitor of the growth of early HPV-immortalized keratinocytes can grow in stages of progression in this model but the organotypic cultures on a collagen gel substratum later-stage cells were resistant to this negative that contains fibroblasts, and a three-dimensional growth factor, which the authors concluded is the tissue-like growth is obtained, which can be basis for the accompanying loss of response to viewed as a cervical carcinoma in situ. In such cul- all-trans-retinoic acid. tures, the expression of squamous markers can be suppressed by all-trans-retinoic acid, although (19 Spontaneously immortalized human higher concentrations of all-trans-retinoic acid keratinocytes and their las-transformed were required to block terminal differentiation in derivatives these cultures than in control organotypic cultures Although spontaneous immortalization is a rare of normal cells in which 30 times higher concen- event, it occurred in a human keratinocyte culture trations were required to suppress Ki mRNA which gave rise to a cell line designated HaCaT. (Merrick et al., 1993). The reason for the difference These cells have been also transformed with c-Ha- between the normal and immortalized cells is ras oncogene, and benign and malignant clones unknown, nor is it known why in another labora- have been isolated. The various cell types have tory (Agarwal et al., 1991, 1996) the immortalized maintained their ability to differentiate into strati- cells were more sensitive than normal cells to all- fied epithelium and in their response to regulation trans-retinoic acid. [The Working Group noted that of keratins by all-trans-retinoic acid. The immortal- the two groups of investigators used different cul- ized and ras-transformed cells expressed keratins ture methods.] Ki and K10 in medium depleted of retinoids, but In HPV-16-immortalized endocervical cell lines the expression of these keratins was fully grown in organotypic culture, all-trans-retinoic suppressed when the concentration of all-trans- acid prevented the dysplastic morphology and retinoic acid was increased (Breitkreutz et al., cytokeratin differentiation markers of carcinoma in 1993). Lotan (1993) suggested that all-trans- situ (Shindoh et al., 1995). Tumorigenic variants of retinoic acid can regulate differentiation of HPV-immortalized cervical cells derived by treat- normal, premalignant and malignant human ment with cigarette smoke condensate were less keratinocytes and can suppress the expression of sensitive to all-trans-retinoic acid than normal and squamous differentiation markers in malignant immortalized non-tumorigenic cells. They formed squamous-cell carcinomas. organotypic epithelium resembling severe dysplasia which was persistent even in the presence of all- (g) Human papillomavirus-immortalized trans-retinoic acid, whereas the immortalized cells human cervical cells formed only a thin epithelium. The investigators Because 90% of human cervical tumours contain predicted that similar resistance to all-trans-retinoic HPV DNA, it is assumed that the virus plays a role acid may occur clinically (Sarma et al., 1996). in the development of this cancer, especially since In a comparison of the sensitivity of cell lines the DNA can immortalize epithelial cells in vitro derived from cervical intraepithelial neoplasia through the E6 and E7 oncogenes. In several (CIN), HPV DNA-transfected cell lines and cervical immortalized ectocervical epithelial cell lines carcinoma cell lines to all-trans-retinoic acid, the derived with HPV-16 DNA, all-trans-retinoic acid retinoid had comparable effects on growth, and other retinoids suppressed the expression of detected as a decrease in DNA synthesis, in all but squamous differentiation markers like keratins two carcinoma cell lines, which were resistant. (Agarwal et al., 1991). all-trans-Retinoic acid all-trans-Retinoic acid inhibited growth in cervical inhibited the growth of the immortalized cells, neoplastic cell lines, including cervical carcinoma although it had no effect on the growth of normal cells (Behbakht et al., 1996).

108 All- trans- Retinoic acid

[See the comment of the Working Group in sec- Retinoic acid dissolved in dimethyl sulfoxide tion (c), above.] inhibited metaplasia, with a median effective dose (ED50) of 3 x 10_11 mol/L when applied over a 10- 4.2.3.2 Effects on differentiation of normal cells day period. Control cultures showed over 90% metaplasia (Newton et al., 1980). (a) Normal human tracheobronchial epithelial cells 4.2.3.3 Cell lines established from tumours Normal human tracheobronchial epithelial cells The effects of all-trans-retinoic acid have been stud- cultured on collagen gels in medium containing ied in numerous cell lines established from various all-trans-retinoic acid and triiodothyronine malignancies. Many of these cancer cell lines expressed a mucociliary phenotype. Removal of maintained responsiveness to some of the the retinoid from the medium caused the cultures pleiotropic effects of retinoids, including suppres- to differentiate into a squamous epithelium, sion of proliferation in monolayer culture, inhibi- accompanied by decreased mucin secretion and tion of colony formation in semi-solid media and reduced expression of the mucin genes MUC2 and induction of differentiation, sometimes including MUCSAC, indicating that all-trans-retinoic acid complete suppression of tumorigenic potential. plays a major role in differentiation of the mucocil- The results of many of these studies have been iary epithelium (Yoon et al., 1997). In normal reviewed (Gudas et al., 1994; Lotan, 1995; and human tracheobronchial epithelial cell cultures, General Remarks to this volume). They are not all-trans-retinoic acid down-regulated the squa- included here because their relevance to cancer mous marker cornifin a and upregulated MUC2, prevention is indirect. MUC5AC and MUCSB mRNAs sequentially at 24, 48 and 72 h, respectively (Koo et al., 1999a). It has 4.2.3.4 Antimutagenicity in short-term tests for been suggested that nuclear RARa and, to a lesser mutagenicitl/ extent, RARy play a role in the control of mucin Although most studies have focused on the role of gene expression, since RARa- and RARy-selective all-trans-retinoic acid in the promotion and agonists strongly induced mucin mRNAs in a dose- progression of cancer, the results of a few studies dependent manner, whereas an RAR3-selective have indicated that it may sometimes act as an retinoid only weakly induced mucin gene expres- anti-initiator. It has been shown to modulate sion at the high concentration of 1 pmol/L. chemically-induced genotoxicity in a number of Furthermore, an RARa antagonist inhibited mucin short-term assays, in both bacteria (Table 4) and gene induction and mucous cell differentiation mammalian cells (Table 5). [The Working Group caused by all-trans-retinoic acid and by RARa- and, noted that many of the reports do not give the iso- surprisingly, by RARy-selective retinoids (Koo et al., mer designation for the retinoic acid used. When 1999b). the source of the retinoic acid was shown, the com- Treatment of primary cultures of human pany was contacted and asked about the availabil- bronchial epithelial cells with all-trans-retinoic ity of different isomers at different times; for exam- acid caused accumulation of cells in the GI phase ple, retinoic acid obtained from Sigma before 1988 of the cell cycle and inhibition of DNA synthesis was all-trans-retinoic acid, since it was the only (Boyle et al., 1999). all-trans-Retinoic acid also sup- form available at that time. In other cases, the pressed epidermal growth factor signalling in nor- author was contacted.] mal human tracheobronchial epithelial cells grown on collagen gels (Moghal & Neel, 1998). (a) Salmonella typhimurium Of the studies in which the ability of all-trans- (b) Hamster trachea explants retinoic acid to inhibit the action of standard Explants of hamster trachea prepared from vitamin mutagens was tested in Salmonella typhimurium A-deficient animals have been used to measure the (Table 4), only one examined indirect DNA dam- ability of retinoids to prevent the squamous meta- age by assaying umu C gene expression in S. plasia which normally results when this tissue is typhimurium TA1535/pSK1002; the others followed cultured in the absence of vitamin A. all-buns- the standard assay of Ames. all-trans-Retinoic acid

109 PARC Handbooks of Cancer Prevention

Table 4. Inhibition by all-trans-retinoic acid of standard mutagens in the Salmonelia(microsome test

Retinoid Mutagen S. typhimurium S9 mix Result' LED/HID° Reference (tested dose)8 (tested dose)" strain

all-trans-RA 3-Amino-3,4- TA1 535/pSK1 002 + + 0.54 jimol/plate Okai at at (1996) (00003-300 dimethyl-5H- (ID50) jimol/plate) pyrido[4,3-b]indole (Trp-P-1) (0.2 jig/ml)

all-trans-HA Adriamycin TA1535/pSK1 002 - - 30 jimol/plate Okai at at (1996) (0.003-30 (3 jig/ml) jimol/plate) all-trans-HA Mitomycin C lAI 535/pSK1 002 - - 30 jirnoVplate Okai at al. (1996) (0.003-30 (llmol! (0.3 jig/ml) plate)

RA (Sigma)d Hydrogen peroxide TA104 - - 10 Ltmol/plate Han (1992) (0.1-10 (5 iimol/plate) itmol/plate) all-trans-RA Cigarette smoke TA98 + - 500 nmol/plate Wilmer & (25-500 condensate Spit (1986) nmol/plate) (100-400 jig/plate) RA (Sigma)e Benzo[a]pyrene TA98 + - 40 jig/plate Qin & Huang (2.5-40 jig/plate) (5 jig/plate) (1985)

RA (Sigma)8 Aflatoxin B1 TA98 + + 2.5 jig/plate Qin & Huang (2.5-40 jig/plate) (0.5 jig/plate) (1985)

all-trans-HA Aflatoxin B1 TA98 + + 26 nmol/plate Whong at at (0.26-2600 (50 ng/plate) LED; 860 (1988) nmol/plate) nmol/plate; 55% decrease in revertants

RA (Sigma)8 Aflatoxin B1 TA98 + + 0.2 nmollplate; Raina & (0.2-2000 nmol/ (200 ng/plate) 70% decrease in Gurtoo (1985) plate) revertants

RA (Sigma)8 Aflatoxin B1 TAt 00 + - 2000 nmol/plate Raina & Gurtoo (02-2000 nmol/ (200 ng/plate) (1 9M) plate)

RA (Sigma)e Aflatoxin B1 TA1 00 + + 0.1 jimol/plate; Bhattacharya (0.1, 0.5 (400 ng/plate) 50% decrease at at (1987) Rmol/plate) in revertants

RA, retinoic acid; S9 mix, 9000 x g microsomal fraction used as exogenous metabolic system; PD = dose of retinol required to inhibit umu C gene expression by 50% a Doses of retinoids and mutagens are given as reported by the authors. b +, inhibition of genotoxicity; -, no inhibition of genotoxicity C LED, lowest effective (inhibitory) dose; HID, highest ineffective dose dprobably all-trans-RA but could be 13-cis-RA, since, 13-cis-RA was listed in Sigma catalogue from 1988 and 9-cis-RA from 1996 8 Presumed to be all-trans-HA since 13-cis-RA was listed in Sigma catalogue only from 1988 and 9-cis-RA from 1996.

110 All-trans-Retinoic acid

Table 5. Inhibition by all-trans-retinoic acid of genetic and related effects in cultured mammalian cells

Retinoid Genotoxic agent Cells/system Investigated Result" LED/HID° Reference (tested dose)9 (tested do8e)9 effect all-trans-RA Mitomycin C Chinese hamster Sister chromatid - 4 rig/ml Sirianni et al. (0.25-4 1kg/mI) (0.03 ig/ml) V79 cells exchange (1981) all-trans-RA" Cyclophosphamide Chinese hamster Sister chromatid + (25 nmoVml) Cozzi et al. (25-50 nmol/ml) (1 mmol/plate) epithelial liver cells exchange (1990) all-trans-RA" 7,12-Dimethylbenz- Chinese hamster Sister chromatid + 37 nmol/ml Cozzi et al. (25-50 nmol/ml) [a]anthracene epithelial liver cells exchange (1990) (0.078 mol/plate) all-trans-HA Aqueous extract of Chinese hamster Sister chromatid + 0.2 1g/ml Patel etal. (0.2-0.8 gg/ml) pan masala (13.5, ovary cells exchange (1998) 12.5 ig/ml water- soluble macala with and without tobacco, respectively) all-trans-RA Aqueous extract of Chinese hamster Chromosomal + 0.4 gg/ml Patel eta]. (0.2-0.8 ig/ml) pan masa!a (135, ovary cells aberrations (1998) 12.5 ig/ml water- soluble masaia with and without tobacco, respectively) all-trans-HA" None Cl 27 mouse cells Chromosomal + 5 nmol/ml Stich et al. (0.1-10 mol/mI) transformed by instability (1990) bovine papilloma- (chromatid bridges virus DNA and fragments)

RA (Sigma)9 Ethyl methane- Chinese hamster Hprt mutation + 25 nmoVml Budroe et al. (1-25 nmol/ml) sulfonate (100 ovary cells (1988) g/ml)

RA (Sigma)9 7,12-Dimethylbenz- Chinese hamster Hprt mutation - 5 nmol/ml Budroe et aL (1-25 nmol/ml) [a]anthracene ovary cells (1988) (1.25-5 1kg/mi)

RA (Sigma)9 Ethyl methanesul- Rat primary Unscheduled - 50 nmol/ml Budroe et al. (1-50 nmol/ml) fonate (200 1g/ml) hepatocytes DNA synthesis (1987)

RA (Sigma)9 Ultraviolet light Rat primary Unscheduled - 25 nmoVml Budroe et al. (1-25 nmol/ml) (32 J/m2) hepatocytes DNA synthesis (1987)

RA (Sigma)9 7,1 2-Dimethyl- Rat primary Unscheduled + 1 nmoVml Budroe et ai, (1-50 nmol/ml) benz[aanthracene hepatocytes DNA synthesis (1987) (2.5, 5 gg/ml) all-trans-RA Dimethyibenz[a]- Mouse epidermal Binding to DNA + 10 Rg/ml Shoyab (1981) (1-100 Rg/ml) anthracene cells in vitro 22% (71 nmol/ml) decrease

111 ARC Handbooks of Cancer Prevention

able 5. (cnntt

Retinoid Genotoxic agent Cella'system Investigated ResultL LED/HIDC Reference (tested dose)a (tested close)" effect

all-trans-RA 3H-Benzo[ajpyrene Cultured human Binding to DNA + 100 [Lg/MI; Bodo at al. (50,100 ig/ml) bronchial explants decreased (1989) binding all-trans-RA Aflatoxin B, None Binding to + 60 nmoVml; Firozi etal. k 500 nmol/rnl) (2 nmoVml) calf thymus DNA In 500/0 (1987) presence of micro- inhibition (see also somes Bhattacharya etaL, 1984) all-trans-RA Aflatoxin B, None Metabolism of + 75 nmoVml; Firozi at al., (~ 500 nmoVml) (43 nmol/ml) at latoxin B1 to 50% (1987) Tris-diol complex inhibition in presence of microsomes

all-trans-RA (!s Benzo[a]pyrene None Binding to + 84 nmoVml; Shah at al. 200 nmol/ml) (60 nmoVml) calf thymus DNA 50% (1992) inhibition

all-trans-HA < Benzo[ajpyrene None B[a]P-7,8-diol j 200 nmol/ml; Shah eta], 200 nmol/ml) (60 nmol/ml) formation (1992)

all-trans-RA None Primary rat Cytochrome # 0.1 nmoVml Westin at al. (0.1-30 nmol/ml) hepatocytes p45007 mRNA (1993) expression

all-trans-HA None Primary rat Cytochrome Jurima- (40 nmol/ml) hepatocytes P450 RNA activity Hornet at al. CyplAl # 40 nmol/ml (1997)

CyplA2 - 40 nmol/ml Cyp3A # 40 nmol/ml

RA, retinoic acid; B[a]P, benzo[a]pyrene a Doses of retinoids and mutagens are given as reported by the authors. "+, inhibition of the investigated end-point; —, no effect on the investigated end-point; #, enhancement of the investigated end-point "LED, lowest effective dose that inhibits or enhances the investigated effect; HID, highest ineffective dose dPersonal communication from author 8 Presumed to be all-trans-HA since 13-cis-RA was listed In Sigma catalogue only from 1988 and 9-ois-RA from 1996

112 All-trans-Retinoic acid inhibited the induction of the umu C gene by the (b) Mammalian cells heterocyclic amine 3-amino-3,4-dimethyl-SH- The ability of all-trans-retinoic acid to inhibit sister pyrido[4,3-blindole (Trp-P-1) in the presence of chromatid exchange and chromosomal breakage hepatic metabolizing enzymes derived from a 9000 has been tested in carcinogen-treated cultures of x g liver supernatant (S9), but it did not prevent the mammalian cells (Table 5). all-trans-Retinoic acid induction of umu C expression by two directly act- did not affect the induction of sister chromatid ing mutagens, adriamycin and mitomycin C (Okai exchange by the directly acting carcinogen mito- et ai., 1996). mycin C in Chinese hamster V79 cells (Sirianni et Four of the studies conducted with the standard al., 1981). [The Working Group noted that the Ames' Salmonelia/microsome test tested the ability retinoid was not present concomitantly with the of all-trans-retinoic acid to inhibit the effects of carcinogen in this study but was added after the directly acting mutagens. It did not prevent the carcinogen.], whereas another study showed that induction of reverse mutation by hydrogen perox- all-trans-retinoic acid protected against the induc- ide in S. typhimurium TA104, a strain sensitive to tion of sister chromatid exchange when present at oxidative mutagens (Han, 1992), and it had no the same time as cyclophosphamide or DMBA, effect on the mutagenic action of MNNG in strain which are indirect mutagens or carcinogens. In the TA100 or of 4-nitroquinoline 1-oxide in strain latter study an epithelial liver cell line of Chinese TA98 (Shetty et ai., 1988; Camoirano et al., 1994). hamster cells was used which is known to activate It significantly inhibited the mutagenicity of three promutagens and procarcinogens (Cozzi et al., nitroarenes: 2-nitrofluorene, 3-nitrofluoranthene 1990). In Chinese hamster ovary cells exposed to and 1-nitropyrene in S. typhimurium TA98 (Tang & aqueous extracts of pan masala, a complex mixture Edenharder, 1997). of areca nut, catechu, lime and cardamom, with or The other studies, conducted with compounds without tobacco, a lower frequency of sister chro- and mixtures that require the presence of S9, matid exchange was observed in the presence of showed mixed results. all-trans-Retinoic acid did all-trans-retinoic acid. The frequencies of chro- not affect the mutagenicity of unfractionated matid-type and chromosome-type aberrations cigarette smoke (Camoirano et al., 1994) or of were also reduced (Patel et ai., 1998). cigarette-smoke condensate in S. typhimurium TA98 C127 mouse cell lines created by transformation (Wilmer & Spit, 1986) and did not affect the induc- with bovine papillomavirus DNA carry 20-160 tion of mutation by benzo[a]pyrene, but it signifi- copies of the DNA and increased frequencies of cantly reduced reverse mutation induced by chromatid bridges and fragments (27-59%) and of aflatoxin B1 in the same tester strain (Qin & micronuclei (6.6-35%). Three-day exposure to all- Huang, 1985). The ability of all-trans-retinoic acid tTans-retinoic acid significantly reduced this insta- to inhibit aflatoxin 131-induced mutation in strain bility, but the effect was transient since the insta- TA98 has been reported in two other studies bility reappeared after cessation of treatment with (Whong et ai., 1988; Raina & Gurtoo, 1985), while the retinoid (Stich et al., 1990). contradictory results were reported with TA100, The effect of all-trans-retinoic acid on mutation one showing a protective effect (Bhattacharya et in mammalian cells has been addressed in only ai., 1987) and the other no inhibition (Raina & one study. It had no effect on cytotoxicity or muta- Gurtoo, 1985). [The Working Group noted that the tion expression at the hypoxanthine-guanine protocol used by Raina and Gurtoo was different phosphoribosyl transferase (Hprt) locus in Chinese from that in the other five studies with Ames' hamster ovary cells exposed to the directly acting test, in that a 5-min preincubation assay was used mutagen ethyl methanesulfonate, but it signifi- rather than the standard plate incorporation cantly reduced DMBA-induced cytotoxicity and approach as described by Maron and Ames (1983). mutation when metabolic activation was provided In addition, the S9 mixtures were prepared from by either uninduced Sprague rat liver S9, Arochlor the livers of C57BL/6Ha mice or Wistar rats 1254-induced Sprague-Dawley rat liver S9 or without pretreatment, whereas in the other studies co-cultivation with primary Sprague-Dawley rat S9 liver fractions were prepared from Arochior hepatocytes (Budroe et al., 1988). This retinoid also 1254-induced rats.] inhibited unscheduled DNA synthesis in primary

113 ]ARC Handbooks of Cancer Prevention

rat hepatocytes induced by the procarcinogen Both of the studies of the effect of all-trans- DMBA, but not that induced by two directly acting retinoic acid on the binding of carcinogens to calf mutagens, ethyl methanesulfonate and ultraviolet thymus DNA showed a protective effect. Binding light. The inhibitory effect on DMBA activity of [3H]aflatoxin B1 to calf thymus DNA, activated occurred at nontoxic concentrations, and the by liver microsomes from phenobarbital-induced authors hypothesized that the effect was due to a Wistar rats, was significantly reduced by all-trans- reduction in DMBA-induced DNA damage through retinoic acid. This effect was ascribed to a reduc- alterations of the DNA adduct load in cells treated tion in the formation of the reactive intermediate concurrently with retinoid and carcinogen (Budroe aflatoxin B1-8,9-epoxide in the presence of the etal., 1987). retinoid, measured by quantifying its hydrolysis This hypothesis is supported by the results of product aflatoxin B1-8,9-dihydrodiol as Tris-diol five studies of the effect of all-trans-retinoic acid on complex in the reaction mixtures (Firozi et al., the formation of carcinogen-DNA adducts. Three 1987). all-trans-Retinoic acid suppressed the forma- were carried out with cultured cells and the tion of adducts on calf thymus DNA by the car- remaining two with calf thymus DNA co-incu- cinogen benzo[a]pyrene in a reaction catalysed by bated with rat liver microsomes (Table 5). When liver microsomes from Arochlor 1254-treated rats. murine epidermal cells from newborn NIH Swiss The inhibitory effect did not appear to be associ- mouse skin were exposed to [3HIDMBA in the pres- ated with the enzymatic activation step (i.e. gener- ence of all-trans-retinoic acid, a significant reduc- ation and further activation of the proximate car- tion was observed in the binding of the carcinogen cinogen, benzo[a]pyrene-7,8-diol in reaction mix- to DNA, in the absence of a significant effect on tures). Instead, the retinoid accelerated the rate at the number of cells. This finding was particularly which the ultimate carcinogenic metabolite, striking because the actual uptake of the radiola- benzo[a]pyrene-7,8-diol-9, lO-epoxide, disappeared belled carcinogen was higher in retinoid-treated from the reaction mixture containing all-frans- cultures (Shoyab, 1981). In a similar study of the retinoic acid (Shah et al., 1992). uptake and binding of [3H]benzo[a]pyrene to DNA In studies of the role of all-trans-retinoic acid in in cultured bronchial mucosa explants from 10 controlling the expression of genes involved in patients (all smokers) with bronchial cancer, the metabolism, a 19-fold induction of cytochrome amount of DNA-bound carcinogen was signifi- P450 (CYP) 20 mRNA levels was found in pri- cantly reduced when all-trans-retinoic acid was mary rat hepatocytes exposed to all-trans-retinoic added. As in the previous study, binding to DNA acid, this effect being exerted at the transcriptional was decreased even though the actual uptake of level, as shown in nuclear run-on experiments the carcinogen was increased in retinoid-treated (Westin et al., 1993). In a similar study, CYP3A cells. The authors concluded that since incorpora- mRNA levels were shown to increase by approxi- tion of [3H]thymidine into DNA (as an index of the mately eightfold in primary hepatocytes exposed number of cells) did not change during treatment to all-trans-retinoic acid. The levels of CYP1A1 in with the retinoid and the carcinogen, the increased messenger RNA were nonsignificantly increased, cellular uptake of the carcinogen was not due to an whereas no effect was observed on CYP1A2 levels increase in the number of cells in the explants (Jurima-Romet et al., 1997). (Bodo et al., 1989). [The Working Group noted that incorporation of [3H]thymidine into DNA was (c) Experimental animals found to be altered in other studies with retinoids.] These studies are summarized in Table 6. The ability of all-trans-retinoic acid to potenti- In rats, the activity of enzymes involved in the ate the action of the chemotherapeutic drug, cis- metabolism of N-acetylaminofluorene and platin, was assessed in human ovarian carcinoma N-hydroxyacetylaminofluorene was enhanced by cell lines. The number of DNA adducts formed was feeding all-trans-retinoic acid. The glucuronyl increased in NIHOVCAR3 cells, a line known to be transferase activity in microsomal preparations sensitive to all-trans-retinoic acid, but not in prepared from the livers of treated animals was IGROV1 cells, which are insensitive to this retinoid enhanced by 37%, thus increasing detoxification (Caliaro etal., 1997). of the carcinogen, and the activity of para-nitro-

114 All-trans-Retinoic acid

Table 6. Effect of exposure to all-trans-retinoic acid on metabolic activity in rodents in vivo

Retinoid (tested Carcinogen (tested Animal strain Investigated effect Resu1tL LED/HIDC Reference dose and adminis- dose and adminis- and species tratlon roule)a tration route)a

RA (025% in Acetylaminofluorene Sprague-Dawley Liver enzyme Daoud & diet for 3 days)d or N-hydroxyacetyl- rats activity: Griffin (1978) aminofluorene • glucuronyltransferase # 37% increase (17 mg/kg bw ip • suif otransferase + 50% decrease for 3 days) • AAF-deacylase - No effect

AAF-deacylase all-trans-IRA None Male Sprague- Liver cytochrome Howell eta[. (30 mg/kg bwper Dawley rats P450 levels (1998) day oy gavage ror UT rni. - 4 days) CYP2BI/2 - CYP2C11 + CYP2E + CYP3A - CYP4A - P450 metabolism (+) Glucuronidation + all-trans-RA None Human P450-mediated # 0.1%(4.5- Duell et aL (single topical dose mediated metabolism fold increase) (1992) of 0.1% applied to of all-trans-HA to 4- skin) hydroxyretlnoic acid all-trans-RA None Human Basal P4501A1 + 0.05% U eta]. (single topical expression (68% decrease (1995) dose of 0.05% in P4501 Al applied to skin) mRNA levels; 75% decrease In P4501A1 protein levels) all-trans-RA None Human Basal P4501 A2 + 0.05% U eta]. (single topical expression (93% reduc- (1995) dose of 0.05% tion in P4501A2 applied to skin) mRNA levels) all-trans-HA 10% crude coal- Human Induced P4501A1 + 0.05% Li et al. (single topical dose tar expression (46% decrease (1995) of 0.05% applied in P4501A1 to skin) mRNA levels) all-trans-RA 0.025% clobetasol Human Induced P4501A1 + 0.05%(69% Li et al. (single topical propionate expression decrease in (1995) dose of 0.05% P4501A1 aoolied to skin) mRNA levels)

RA, retinoic acid; ip, intraperitoneally; AAF, acetylaminofluorene a Doses of retinoids and carcinogens and routes of administration are given as reported by the authors. b , inhibition of the investigated end-point; (+), weak inhibition of the investigated end-point, not significantly different; -, no effect on the investigated end-point, #, enhancement of investigated end-point; (#) enhancement but statistically only approaching significance, p < 0.06 a LED, lowest effective dose that inhibits or enhances the investigated effect; HID, highest Ineffective dose dSource and type not given; presumed to be all-trans-RA because of date

115 IARC Handbooks of Cancer Prevention

phenol-sulfotransferase, the enzyme involved in adducts, thought to be derived from a CYP-inde- activation of N-acetylaminofluorene and N-hydroxy- pendent pathway that probably involves peroxyl acetylaminofluorene to reactive states, was inhib- radical-dependent epoxidation. When all-trans- ited; however, it had no effect on N-acetylamino- retinoic acid was administered with the second fluorene-deacylase activity (Daoud & Griffin, 1978). TPA treatment, formation of the (-)-anti-BPDE- In a comprehensive study of the effect of five DNA adducts was significantly inhibited. retinoids, one of which was all-trans-retinoic acid, Administration of the retinoid with the first TPA on hepatic microsomal metabolism and CYP activ- treatment had no effect. The authors speculated ity in Sprague-Dawley rats, the animals received that the first TPA dose recruited neutrophils to the daily oral doses of 30 mg/kg bw for 4 days, and treatment site and the second dose triggered the liver microsomes were prepared on day 5. The release of oxidants from these neutrophils. They activity of CYP isoenzymes was assayed by western further suggested that the retinoic acid acts as a blot immunoanalysis. The activities of CYP1A2, radical scavenger, thus preventing peroxyl radical- CYP2131/2 and CYP3A were reduced by roughly dependent epoxidation (Marnett & Ji, 1994). 27%, 20% and 27% respectively, in animals receiv- There have been few studies of the effect of ing all-trans-retinoic acid, although these effects all-trans-retinoic acid on metabolism in humans, were not statistically significant. The activity of but there is some indication that metabolic activity CYP2E was reduced by 30% and that of CYP2C11 and the CYP enzyme profiles in tissues are altered by 40% (both p < 0.05), whereas that of CYP4A by all-trans-retinoic acid. A single topical dose of remained unchanged. The effect of this drug on 0.1% all-trans-retinoic acid cream or cream vehicle metabolic activity was limited to a study of its own was applied to adult human skin and the region phase I and II metabolism. A decrease was observed was occluded for four days with Saranwrap. After in the CYP-mediated metabolism of all-trans- four days, the test area was washed and sliced off, retinoic acid by microsomal preparations from and microsomal fractions were prepared and treated animals, although the effect only assayed for their capacity to metabolize [31flall- approached significance (p = 0.06). In contrast, a trans-retinoic acid in vitro. Microsomes from significant decrease was found in the glucuronida- treated sites had a 4.5-fold increase in their capac- tion capacity of the microsomal preparation. The ity to form 4-hydroxyretinoic acid in comparison authors noted that the patterns of alterations in with microsomes from vehicle-treated sites. This metabolism and isozyme profiles differed signifi- metabolism appeared to be CYP-mediated since cantly among the retinoids studied and suggested the inclusion of ketoconazaole, an inhibitor of that the effect could be related to binding selectiv- CYP-mediated activity, in the reaction mixtures ity of the different retinoids for either RAR or RXR resulted in inhibition of metabolism in microso- receptors, although the data are not conclusive mal fractions isolated from retinoic acid-treated (Howell etal., 1998). sites (Duell et al., 1992). In a similar study, the basal Retinoids may also modulate the metabolism of level of expression of CYP1A1 and CYP1A2 carcinogens in CYP-independent pathways. In a was quantified in skin samples from volunteers study of the effect of all-trans-retinoic acid on DNA receiving topical 0.05% all-trans-retinoic acid in adduct formation, female CD-1 mice were given a cream or cream without retinoic acid. The authors topical application of the proximate carcinogen also examined the effect of all-trans-retinoic acid (7S,8S)-dihydroxy-7,8-dihydrobenzo[a]pyrene ((-t-)- on the expression of these two isoenzymes in BP-7,8-diol), which is further metabolized by epox- patients receiving the cream with either 10% crude idation to 7,8-dihyroxy-9, 10-epoxy-7,8,9, 10 tetra- coal-tar or 0.025% clobetasol proprionate, a potent hydrobenzo[a]pyrene (BPDE). When the BP-7,8- glucocorticoid. all-trans-Retinoic acid reduced the diol was applied by itself to the animals, it was basal activities of CYP1A1 mRNA and protein by metabolized mainly by CYP systems, resulting in 68% and 75% respectively, and the basal activity of (+)-syn-BPDE-DNA adducts; however, when the CYP1A2 mRNA by 93%. Coal-tar and clobetasol animals were pretreated with TPA 24 h before increased the activity of CYP1A1 but not that of administration of TPA and (+)-BP-7,8-diol, the pat- CYP1A2 mRNA expression. all-trans-Retinoic acid tern of adducts changed to include (-)-anti-BPDE inhibited the CYP1A1 mRNA expression induced

116 All-trans-Retinoic acid by coal-tar by 46% and that induced by clobetasol Retinoic acid can also affect other down-stream by 69% (Li etal., 1995). events of TPA signalling. TPA activates protein kinase C and eventually activates the transcription 4.3 Mechanisms of cancer prevention activator protein 1 (AP-1). all-trans-Retinoic acid all-trans-Retinoic acid may prevent or delay car- can exert anti-AP-1 activity by trans-repressing the cinogenesis by several mechanisms, which depend AP-1 function and thereby inhibiting TPA-induced on the cell type used in vitro, on the carcinogen transformation of mouse epidermal JB6 cells (Li et and animal strain in vivo and on the tissue affected. al., 1996). Furthermore, in DMBA-initiated skin of Most of the studies indicate that retinoids inhibit transgenic mice carrying an AP-1-luciferase the promotion step of the multistage carcinogene- transgene, inhibition of papilloma formation by sis process, although there are indications that it all-trans-retinoic acid and by retinoids with anti- also affects initiation. Several reports described in AP-1 activity appeared to be mediated by suppres- section 4.2.3.2 support the hypothesis that sion of AP-1 activation. Retinoids capable of RAR retinoids such as all-trans-retinoic acid can inhibit element trans-activation but devoid of anti-AP-1 initiation induced by carcinogens that require activity failed to inhibit papilloma formation metabolic activation, whereas they have little (Huang et al., 1997). effect on directly acting carcinogens. The mechanisms of the suppression of initiation include: 4.3.2 Inhibition of cell proliferation induction of the transcription of certain CYP The formation of a premalignant lesion requires enzymes that can detoxify carcinogens, decreased that initiated cells proliferate to expand the initi- binding of carcinogens to DNA and decreased ated clone. Clearly, inhibition of such proliferation carcinogen-induced DNA damage. The activity of would be an important mechanism for cancer several CYP enzymes was found to be regulated at prevention. There is no direct evidence that all- the level of transcription by direct binding of trans-retinoic acid can block the proliferation of nuclear RARs to retinoic acid response elements in initiated cells in vivo because they cannot be iden- the gene promoters, as shown for CYP1A1 tified at an early stage as such, but there is ample (Vecchini etal., 1994). evidence that all-trans-retinoic acid can inhibit cell Most studies on the effects of all-trans-retinoic proliferation in a number of settings. It inhibited acid on carcinogenesis indicate that the main cell proliferation by regulating cell cycle progres- mechanism is inhibition of promotion, which is sion from Gi to S phase by altering the levels of related to the ability of retinoids to antagonize the cell cycle controlling proteins. activity of tumour promoters and affect the proliferation, differentiation and apoptosis of premalig- 4.3.2.1 Cyc!ins and cyclin-dependent kinase nant and malignant cells. The ability of all-trans- inhibitors retinoic acid to alter intercellular adhesion and The inhibition of DNA synthesis and the Gi arrest inhibit host responses such as angiogenesis may in SV-40-T-immortalized human bronchial epithe- also play a role in its chemopreventive activity. lial BEAS-2B cells and their NNK-transformed derivative cell lines was found to occur as a result 4.3.1 Antagonism of tumour promotion and of suppression of the protein levels of cyclins Dl activator protein I activity and E at a post-translational level. all-trans- all-trans-Retinoic acid inhibits the action of Retinoic acid promoted the degradation of cyclin tumour promoters by antagonizing tumour pro- Dl by targeting it for proteolysis in proteasomes moter signalling. For example, it inhibited the via increased ubiquitinylation which depended on induction of omithine decarboxylase by TPA in the C-terminal PEST[proline (P), glutamate (E), ser- cultured tracheal cells (Jetten & Shirley, 1985) and ine (S) and threonine (T)I sequence (Langenfeld et mouse skin (Connor et al., 1983). The mechanism al., 1996, 1997; Boyle et al., 1999). Specific nuclear by which ornithine decarboxylase expression is EARs have been implicated in this effect because controlled by all-trans-retinoic acid appears to be the receptor-selective retinoids that activated RARI3 suppression of gene transcription and involves or RXR pathways caused a greater decrease in the liganded nuclear RAR (Mao et al., 1993). all-trans- amount of cyclin Dl protein and corresponding

117 IARC Handbooks of Cancer Prevention inhibition of DNA synthesis (Boyle et al., 1999). suppressed the expression of TGF-a and EGFR Studies with lymphoblastoid B cell lines immortal- mRNA in head-and-neck squamous-cell carcinoma ized with Epstein-Barr virus have shown that all- cells by decreasing gene transcription (Grandis et trans-retinoic acid-induced accumulation in the al., 1996). GO/GI phase is associated with multiple effects on HPV immortalization increased EGF receptor Gi regulatory proteins, including p27Kipl up-reg- levels in ectocervical cells, increasing their sensitiv- ulation, decreased levels of cyclins DZ, D3 and A ity to growth stimulation by EGF. all-trans-Retinoic and inhibition of cyclin-dependent kinase (CDK)2, acid reduced both EGF binding and EGF receptor CDK4 and CDK6 activity, which ultimately protein levels in immortalized cells but not in nor- resulted in reduced pRb phosphorylation and mal ectocervical cells. Thus, it can attenuate the GO/G1 growth arrest (Zancai et al., 1998). p21, increased responsiveness to EGF by decreasing the which has been shown to induce GI arrest by EGFR level (Sizemore & Rorke, 1993). all-trans- inhibiting CDK and proliferating cell nuclear anti- Retinoic acid inhibition of the growth of HPV- gen dependent DNA replication, was recently immortalized ectocervical cells and cervical carci- found to possess an RAR element in its promoter noma cell lines has been proposed to result from and to be regulated by retinoic acid. This could be an increase in insulin-like growth factor binding another mechanism for cell cycle regulation (Liu et protein 3 mRNA and protein levels and a reduced al., 1996). extracellular concentration of free insulin-like growth factor I (Andreatta-Van Leyen et al., 1994). 4.3.2.2 trans-Repression of activator protein 1 Transforming growth factor-p (TGF-0) plays a As activated AP-1 is the ultimate mediator of complex role in the regulation of proliferation and signalling by many mitogens, the antagonistic differentiation of many cell types, including cells effects of all-trans-retinoic acid on AP-1 may sup- of epithelial origin, for which TGF-13 is usually a press growth. This was found to occur in normal growth inhibitory factor. In the immortal mouse bronchial epithelial cells in which growth had epidermal cell line JB6, TPA caused progression to been inhibited by all-trans-retinoic acid but not in anchorage independence and tumorigenicity, the all-trans-retinoic acid-resistant, tumorigenic partly by decreasing the level of TGF-0 receptor derivatives of SV-40-T-immortalized BEAS-2B cells expression. all-trans-Retinoic acid counteracted (Lee et al., 1997). both the promoting effect of TPA and its suppression of TGF-f3 receptor (De Benedetti et al., 1991). 4.3.2.3 Suppression of the human papillomavirus oncogenes E6 and E7 4.3.3 Restoration of normal differentiation HPV-16 immortalized keratinocytes were very sen- Carcinogenesis is characterized by aberrant differ- sitive to growth inhibition by all-bans-retinoic acid entiation, which is manifested by either blockage because the retinoid inhibited the expression of of cells at an early stage of differentiation or HPV-16 E6 and E7 oncogenes, which are required redirection of differentiation towards an abnormal for maintenance of the continuous proliferation of pathway. Several reports described in the General these immortalized cells (Pirisi et al., 1992). Remarks (section 4) have demonstrated the ability of all-trans-retinoic acid to suppress squamous-cell 4.3.2.4 Modulation of autocrine and paracrine loops differentiation and enhance mucociliary differen- Premalignant cells often have a growth advantage tiation in epithelial cells as well as stimulate differ- over normal cells, as they overexpress growth fac- entiation of numerous tumour cell lines. It is tor receptors that can mediate paracrine or thought that restoration by all-trans-retinoic acid autocrine growth stimulation. One example of of normal differentiation in premalignant cells such a receptor is the epidermal growth factor might be accompanied by restoration of normal receptor (EGFR) which is overexpressed in various growth control mechanisms as well, but there is no premalignant lesions and can enhance cell growth clear experimental evidence that the effect of all- by autocrine or paracrine routes in conjunction trans-retinoic acid on differentiation of premalig- with epidermal growth factor (EGF) or transform- nant cells is the cause of either cell growth inhibi- ing growth factor a (TGF-(x). all-trans-Retinoic acid tion or cell apoptosis.

118

All-trans-Retinoic acid

The clear demonstration that all-trans-retinoic (Cx43) in C3H/1OT1/2 cells at the levels of mRNA acid can induce terminal differentiation in vivo and protein (Rogers et al., 1990); the resulting even in a fully malignant condition, acute promye- increase in gap-junctional communication is locytic leukaemia, lends strong support to this con- highly correlated with the ability of all-trans- cept (Castaigne etal., 1990; Warrel etal., 1993). retinoic acid to inhibit neoplastic transformation in these cells (Hossain et al., 1989) and the 4.3.4 Inhibition of prostaglandin production suppression of proliferation in normal and trans- An excessive production of prostaglandins has formed cells (Mehta et al., 1989). Inhibition of been correlated with tumour promotion. More proliferation by all-trans-retinoic acid was depen- recently, it was found that expression of the dent on cell-cell contact and was not seen in enzyme cyc-looxygenase-2 (Cox-2), which catalyses sparsely seeded cells, again implicating gap-junc- the synthesis of prostaglandins, can be induced by tional communication in this response (Hossain & growth factors and tumour promoters and is up- Bertram, 1994). The relevance of induced gap- regulated in transformed cells and tumours. junctional communication to the chemopreven- Therefore, it has become a target for chemopreventive activity of all-trans-retinoic acid in vivo is sug- tion. Treatment of oral epithelial cells with either gested by the demonstration that the retinoid EGF or TPA enhanced transcription of Cox-2 and upregulates Cx43 expression in human skin after increased production of prostaglandin-2. These topical application (Guo et al., 1992). The mecha- effects were inhibited by all-trans-retinoic acid nism by which it increases Cx43 expression is not (Mestre et al., 1997). [The Working Group noted clear, as the promoter region does not contain a that the molecular mechanism of this effect of all- known RAR element. In one study, stabilization of trans-retinoic acid has not been elucidated.] Cx43 mRNA by all-trans-retinoic acid was suggested (Clairmont et al., 1996). 4.3.5 Induction of apoptosis Several studies summarized in the General 4.3.7 Modulation of cell adhesion and motility Remarks (section 4) demonstrated the ability of all- Cell invasion through the basement membrane is trans-retinoic acid to induce apoptosis in various the ultimate step that distinguishes a carcinoma tumour cell lines. The mechanism by which apop- in situ from a malignant tumour. As this process tosis is induced is not clear, but several studies have requires changes in cell adhesion and detachment, implicated nuclear RARs and RXRs in the process local proteolysis and migration, inhibition of on the basis of the results of experiments with invasion may suppress malignant conversion. It is receptor-selective retinoids and transfection (Nagy noteworthy that all-trans-retinoic acid can up-reg- et al., 1995; Melino et al., 1997; Monczak et al., ulate the function of the invasion-suppressor 1997). It is still not clear which target genes are complex E-cadherin/catenin (Vermeulen et al., induced that trigger apoptosis. It has been sug- 1995) and inhibit the expression of various gested that induction of tissue transglutaminase by enzymes that degrade the basement membrane, all-trans-retinoic acid may be related to apoptosis such as collagenase and stromelysine, at the level induction (Melino et al., 1997). of transcription by antagonizing AP-1 (Nicholson et al., 1990; SchUle et al., 1991). In addition, 4.3.6 Increased gap-junctional communication all-trans-retinoic acid suppressed the level of Most normal cells are directly coupled via intercel- autocrine motility factor receptor and decreased lular gap junctions formed by the assembly of cell motility (Lotan et al., 1992). These findings connexin proteins. Loss of gap-junctional commu- suggest that if it can suppress the expression of the nication is an early event in neoplasia both in vitro invasive phenotype in carcinoma in situ, it may and in vivo. Restoration of this communication by prevent the progression of a premalignant lesion transfection of connexin genes into tumour cells to a malignant one. results in enhanced growth control and/or suppression of the neoplastic phenotype (Trosko & 4.3.8 Inhibition of angiogenesis Ruch, 1998). all-trans-Retinoic acid has been The progressive growth of solid tumours depends shown to increase the expression of connexin 43 on the development of new blood vessels, a

119 IARC Handbooks of Cancer Prevention

process known as neovascularization or angiogen- 7. Other Toxic Effects esis. Tumour cells secrete factors that induce the directed migration and proliferation of endothelial 7.1 Adverse effects cells from capillaries in normal tissue, which even- 7.1.1 Humans tually differentiate and form vessels around and At the recommended oral dose of all-trans-retinoic within tumours. It is likely that some premalignant acid, 45 mg/m2 per day as two evenly divided lesions also depend on angiogenesis for conversion doses, virtually all patients experience some into invasive cancer. all-trans-Retinoic acid has drug-related toxicity. The most frequent adverse demonstrated antiangiogenic effects in several events are similar to those described in patients systems. In one study, it caused the endothelial taking high doses of retinol and its esters (IARC, cells of large and small vessels to become refractory 1998), especially headache, fever, weakness and to stimulation of migration by tumour-condi- fatigue. Rare adverse events associated with use of tioned media or purified angiogenic factors (a- all-trans-retinoic acid in patients with acute fibroblast growth factor, basic fibroblast growth promyelocytic leukaemia include hypercalcaemia, factor, vascular endothelial growth factor, platelet- bone-marrow necrosis, bone-marrow fibrosis, derived growth factor, TGFI3-1, and interleukin-8) acute pancreatitis, thromboembolic events, acute without affecting cell proliferation (Lingen et ai., neutrophilic dermatosis, erythema nodosum, 1996). Rats given all-trans-retinoic acid were basophilia, hyperhistaminaemia, granulomatous unable to mount a neovascular response to proliferation and necrotizing vasculitis (reviewed tumours implanted in their corneas. These results byHatake etal., 1997; Paydas etal., 1998). The tox- indicated that all-trans-retinoic acid can affect icity associated with topically applied all-trans- directly both tumour cells and endothelial cells retinoic acid at 0.025% or 0.01% is generally local- and thereby suppress the formation of new blood ized, dermal and reversible after discontinuation of vessels in vivo. Treatment of mice xenotransplanted treament (Arky, 1998). with a human squamous-cell carcinoma reduced the level of a binding protein for fibroblast growth 7.1.1.1 Retinoic acid syndrome factor. This inhibited angiogenesis and led to a About 25% of patients with acute promyelocytic decrease in the tumour growth rate. leukaemia who have been treated with the recommended oral dose of all-trans-retinoic acid 5. Other Beneficial Effects have experienced 'retinoic acid syndrome', a life-threatening disorder reported to be related to all-trans-Retinoic acid is of benefit to patients suf- leukocyte activation (Fenaux & De Botton, 1998). fering from a variety of dermatological disorders The syndrome usually occurs within the first (see section 2.3). month of treatment, sometimes after the first dose, and is characterized by fever, dyspnoea, weight 6. Carcinogenicity gain, radiographic pulmonary infiltrates and pleural or pericardial effusion. The syndrome has 6.1 Humans occasionally been accompanied by impaired No data were available to the Working Group. myocardial contractility, and episodic hypotension and has been observed with or without concomi- 6.2 Experimental models tant leukocytosis. Glucocorticoids given at high No studies of the carcinogenicity of all-trans- doses when symptoms of the syndrome appear retinoic acid were available to the Working Group, may reduce the morbidity and mortality; in the but all-trans-retinoic acid can act as a tumour absence of prevention by chemotherapy, 60% or promoter in mouse skin and can enhance liver car- more of patients taking oral all-trans-retinoic acid cinogenesis induced by NDEA in mice (for details, may require this treatment (Arky, 1998). see section 4.2.1). Retinoic acid syndrome has been ascribed to infiltration of leukaemic or maturing myeloid cells

120 All-trans-Retinoic acid into the lung parenchyma. Diffuse alveolar haem- Kentos et al., 1997; Yutsudo et al., 1997; Arky, orrhage with pulmonary capillaritis was reported 1998). Hypercalcaemia has also been observed in one woman who was treated with all-trans- after oral administration of all-trans-retinoic acid; retinoic acid for acute promyelocytic leukaemia in one case, the hypercalcaemia was controlled (Nicolls et al., 1998). Thromboembolic complica- and complete remission of acute promyelocytic tions have also been reported, including acute leukaemia was achieved after the dose of all-trans- renal failure due to occlusion of renal vessels retinoic acid was reduced from 45 to 27 Mg/M2 per (Pogliani et al., 1997). A study of the development day (Lemez, 1995). of retinoic acid syndrome showed that clinical A phase-I trial of orally administered all-trans- signs generally develop within a median of seven retinoic acid was conducted to establish the maxi- days. Respiratory distress (89%), fever (81%), mum tolerated dose when given once daily to pulmonary infiltrates (81%), weight gain (50%), patients with solid tumours. In 49 patients who pleural effusion (47%), renal failure (39%), pericar- received doses ranging from 45 to 309 mg/rn2 per dial effusion (19%), cardiac failure (17%) and day, hypertriglyceridaemia was the dose-limiting hypotension (12%) were the main clinical signs, effect at 269 mg/m2 per day; grade 3 hypertriglyc- and almost all subjects with the syndrome experi- eridaemia developed in one patient each at 110, enced at least three of these events. Nine of 64 138 and 269 mg/m2 per day, and grade 4 hyper- cases of retinoic acid syndrome resulted in death. triglyceridaemia developed in one patient each at No significant predictive factors of the syndrome 88, 215 and 269 mg/m2 per day. Grade 3 hyper- were found, but its occurrence was associated with cholesterolaemia was seen in one patient at 269 shorter event-free survival and shorter overall Mg/M2 per day. Grade 3 transient elevations of survival (De Botton et al., 1998). transaminase activity were seen in four patients treated at doses ~! 56 mg/m2 per day. Toxic effects at 7.1.1.2 Relapse of acute promyelocytic leukaemia at grade 3 and 4 occurred sporadically and included unusual sites thrombocytopenia, dehydration and transient Although the combination of all-trans-retinoic acid renal failure, localized desquamous rash, staphylo- and chemotherapy with daunorubicin and cyto- coccal bacteraemia, probable pseudotumour sine arabinoside has become the standard therapy cerebri, shortness of breath, severe cough, rnyalgia, for acute promyelocytic leukaemia, concern has severe exacerbation of neck pain, headache, been raised that all-trans-retinoic acid in combina- anorexia, fatigue, dysphagia, scierai haemorrhage, tion with the other agents may increase the risk for anaemia, nausea and vomiting. Severe toxicity relapse at unusual sites. Myelodysplastic syndrome tended to occur when the initial peak plasma con- and central nervous system relapse, although rare, centration of all-trans-retinoic acid was 0.5 pg/mI, have been seen after treatment of acute promyelo- and the frequency of toxicity did not change as the cytic leukaemia with all-trans-retinoic acid. Whether plasma concentration decreased. The daily dose of the frequency of such events is truly increased all-trans-retinoic acid in patients with solid among these patients is being addressed in clinical tumours recommended on the basis of these find- trials (Bseiso et al., 1997; Evans et al., 1997). ings is 215 Mg/M2 (Conley et al., 1997). [The Working Group noted that the symptoms were not 7.1.1.3 Metabolic, nutritional and haetnatological necessarily related to treatment.] toxicity In a clinical study of the treatment of chronic Up to 60% of patients given the prescribed oral myeloid leukaemia, 18 patients were given 12 dose of all-trans-retinoic acid experience hypercho- courses of 80 Mg/M2 per day, divided into two lesterolaemia and/or hypertriglyceridaemia, and equal doses, each course consisting of one week of 50-60% show increased activity of liver enzymes. drug followed by one week's rest. Eleven patients These abnormalities can sometimes lead to more left the study before the sixth course because of severe complications such as acute pancreatitis, progressive hyperleukocytosis, thrombocytosis or hepatotoxicity, hyperleukocytosis, worsening of refusal. Five additional subjects were withdrawn coagulopathy, renal dysfunction, myocardial before the twelfth course because of elevated infarct and thrombocytosis (Cull et al., 1997; leukocyte counts, and one withdrew for other

121 ARC Handbooks of Cancer Prevention

reasons. Hepatic toxicity of grades 1-2 was observed subsequent study, 1 mL of 0.3 75% all-ti-ans-retinoic in 5% of participating subjects (Russo et al., 1998). acid induced only local, mild side-effects consist- Conversely, there were no documented instances ing primarily of increased vulvar burning, itching of increased liver function or triglyceride concen- and irritation; again, no systemic side-effects were tration in 13 patients with chronic myeloid observed (Meyskens et al., 1994). leukaemia who carried the Philadelphia chromosomal translocation and were treated for a median (b) Oral dosing duration of 56 days with 175 Mg/M2 per day, Mucocutaneous reactions are also common after divided into two equal daily doses (Cortes et al., treatment with oral all-trans-retinoic acid and 1997). include mucocutaneous dryness, xerostomia, dry skin, xerophthahnia, erythema and pruritis 7.1.1.4 Mucocutaneous toxicity (Conley etal., 1997; Sutton etal., 1997; Budd etal., (a) Topical application 1998; Russo et al., 1998). An oral dose of 230 The most frequent adverse effects of topically Mg/M2 in combination with 20 mg/day tamoxifen applied all-trans-retinoic acid are dermal. Local resulted in unacceptable dermatological toxicity peeling, dry skin, burning, stinging, erythema and (moist desquamation) in patients with advanced pruritus were reported by almost all of 179 patients breast cancer (Budd et al., 1998). Six of 13 patients who applied 0.05% all-trans-retinoic acid cream to with chronic myeloid leukaemia experienced dry their faces. The reactions were usually of mild to skin or dry mucous membranes after administra- moderate severity, occurred early during therapy tion of 175 mg/m2 per day in two equal doses and recurred after an initial 24-week decline. (Cortes etal., 1997). Patients using topical all-trans-retinoic acid have a heightened sensitivity to sunlight and extreme 7.1.1.5 Headache and general toxicity wind or cold. Temporary hyper- or hypopigmenta- Moderate to severe headaches are commonly expe- tion has also been reported (Arky, 1998). Skin rienced during oral therapy with all-trans-retinoic irritation caused by topically applied ail-b-ans- acid. Cases of pseudotumour cerebri with clinical retinoic acid does not appear to involve injury to signs of headache, nausea, double vision and bilat- the skin barrier but may be caused by dilatation of eral papilloedema have been reported (Sano et al., the cutaneous vasculature (Fullerton & Serup, 1998). General pain, bone pain, malaise and myal- 1997). Modified delivery systems such as polymer gia are also associated with such therapy (Conley et complexes and microsponge particles have been al., 1997; Budd et al., 1998; Russo et al., 1998). developed to reduce the irritating effects of topical Headache was the most common side-effect all-trans-retinoic acid (Leyden, 1998). (54%) in a pilot study of orally administered all- The effectiveness of topical all-trans-retinoic trans-retinoic acid in patients with chronic myel- acid (0.05%) in reversing signs of photoageing was ogenous leukaemia who carried the Philadelphia investigated under conditions of extended use (48 chromosome and were given a dose of 175 mg/ml weeks). As expected, the adverse events were per day in two equal doses (Cortes et al., 1997). generally mild and were essentially dermal (dry In a phase-II trial in patients with metastatic breast skin, peeling, burning/stinging, erythema, irritation, cancer, all-trans-retinoic acid was given orally at a pruritis and papules). The frequency of the adverse dose of 50 mg/ml three times a day for 14 days of a effects decreased with time (Olsen et al., 1997). 21-day cycle, which was repeated until progression Topically applied all-trans-retinoic acid has of the disease, unacceptable toxicity or patient been investigated as an intravaginal treatment for withdrawal. Of 17 subjects, 14 completed at least cervical intraepithelial neoplasia. In one study, one course of therapy; the median time to progres- doses of 0.05-0.2% applied to a sponge and sion for the remaining 14 subjects was six weeks. inserted in a cervical cap for four days produced Two patients experienced grade 3 headache during vaginal irritation, ulceration and discharge, with the first cycle; the symptoms resolved after no evidence of systemic toxicity (Surwit et al., discontinuation of the drug, and returned after 1982). A study of doses increasing from 0.05% for re-challenge. Six other subjects experienced grade four days showed that the maximum tolerated 2 headache during treatment (Sutton et al., 1997). dose was 0.372% (Meyskens et al., 1983). In a 122 All-trans-Retinoic acid

The combination of all-trans-retinoic acid and 7.1.2 Experimental models interferon-cc was investigated in a phase-I trial in The LD50 of orally administered all-trans-retinoic children with refractory cancer. Pseudotumour acid is approximately 2200 mg/kg bw in mice and cerebri or dose-limiting headache was observed in 2000 mg/kg bw in rats (Kamm, 1982). The maxi- two of five patients over 12 years of age who had mum tolerated dose in athymic nude mice was been treated at a dose of 120 Mg/M2 per day, and in 20 mg/kg bw per day when given five times per one of six patients under 12 years who had been week for four weeks. The dose was selected on the given 90 mg/ml per day (Adamson et al., 1997). basis of acceptable weight loss and symptoms of A phase-I/Il trial of all-trans-retinoic acid and hypervitaminosis A; a weight loss of 10-20% and tamoxifen was conducted in patients with poten- mild to severe rnucocutaneous reactions, such as tially hormone-responsive advanced breast cancer. dry or red skin, were seen at doses ~! 30 mg/kg bw The patients received 20 mg/day tamoxifen and per day (Shalinsky et al., 1995). all-trans-retinoic acid on alternating weeks at doses Rats given all-trans-retinoic acid orally at 5 or of 70-230 Mg/M2 per day, divided into two equal 50 mg/kg bw per day for 13 weeks showed hair doses per day. At all doses, headache, nausea, bone loss, dermal and mucosal alterations, inhibition of pain and skin changes were noted. The headaches spermatogenesis and weight loss at the low dose, were most severe during the first week of therapy and increased serum transaminase and alkaline and peaked at the end of the first week. The symp- phosphatase activities at the high dose. Similar toms recurred in subsequent weeks of all-trans- signs were seen in dogs, but 50% of those at the retinoic acid therapy, although their severity high dose died. In mice, doses of 150-250 mg/kg tended to wane with each subsequent cycle. bw per day caused alopecia, weight loss and skin all-trans-Retinoic acid at a dose of 230 Mg/M2 and membrane changes after five days (Kamm et produced unacceptable headache. Grade 3 al., 1984). In other studies in mice, the main headache, grade 2 nausea and vomiting and der- dose-related findings included bone rarefaction, matological effects also occurred in some bone fracture, elevated serum alkaline phosphatase subjects given all-trans-retinoic add at 190 Mg/M2. activity, testicular degeneration, dermal and epi- The rnaxirnurn tolerated dose that could be given dermal inflammation and hyperkeratosis. In rats, in alternating weeks with 20 mg/day tamoxifen decreases in plasma albumin and in haemoglobin was 190 mg/ml per day (Budd et al., 1998). concentration and an increase in serum alkaline phosphatase activity were seen. In a comparative 7.1.1.6 Gastrointestinal toxicity study of all-trans-retinoic acid, etretinate and Gastrointestal toxicity ranging from constipation retinol palmitate/retinol acetate in rats, doses of to severe nausea has been reported after oral 15, 7.5 and 40 mg/kg bw per day, respectively, had administration of all-trans-retinoic acid. A dose of about the same negative effect on body weight. 80 Mg/M2 per day divided into two equal doses After four weeks of administration at these doses, produced constipation (11%) and nausea (5%) in bone fractures and increased serum alkaline patients with chronic myeloid leukaemia (Russo et phosphatase activity were observed with all agents, al., 1998). When all-trans-retinoic acid at doses of but all-trans-retinoic acid and retinol palmi- 70-230 Mg/M2 per day was combined with 20 tate/retinol acetate were more lethal than etretinate. mg/day tamoxifen, grade 1 nausea and vomiting Retinol palmitate/retinol acetate resulted in the low- were observed in most subjects; grade 2 nausea and est frequency of bone fractures, and the increase in vomiting occurred in some subjects receiving doses serum alkaline phosphatase activity was greatest ~t 190 Mg/M2 per day (Budd et al., 1998). Two of 17 with all- trans-retinoic acid, indicating that patients with metastatic breast cancer experienced retinoids are not equipotent with respect to their grade 3 nausea and vomiting at a dose of 50 Mg/M2 short-term toxicity (reviewed by Kamm, 1982). three times a day (Sutton et al., 1997). Nausea was In male mice treated topically with 0.1% all- also experienced by four of 13 patients with trans-retinoic acid in gel microspheres for 90 days chronic rnyelogenous leukaemia given 175 mg/m2 at 2 or 5 mg/kg bw per day, testicular weight was per day in two equal doses; one of the cases was reduced, with no pathological changes. This effect described as severe (Cortes et al., 1997). was not seen at 0.5 mg/kg bw per day. Females

123 IARC Handbooks of Cancer Prevention

showed a reduction in ovarian weight at 5 mg/kg embryopathy, such as small or absent ears. The bw per day, with no pathological changes. A authors reviewed data to 1988 and concluded dose-related increase in the plasma concentration that any effect of topical all-ti-ans-retinoic acid of all-trans-retinoic acid was seen 4 h after the first on human development would be weak (Rosa, dose. Male and female dogs treated for 90 days 1992). with 0.1% all-trans-retinoic acid in gel micros- At least two other cases of congenital malforma- pheres at 0.2, 0.5 or 1 mg/kg bw per day showed no tion have been associated with cosmetic or thera- evidence of reduced testicular or ovarian weights peutic topical application of all-trans-retinoic acid, or other pathological changes. The systemic expo- which have features in common with retinoid sure observed in preclinical studies of toxicity with embryopathy (Camera & Pregliasco, 1992; Lipson topically applied all-trans-retinoic acid is probably etal., 1993). the result of incidental ingestion (Arky, 1998). [The Working Group noted that topical administration (b) Percutaneous absorption of high doses of all-trans-retinoic acid gives rise to The absence of teratogenic effects after topical severe skin irritation, which is dose-limiting.] application of all-trans-retinoic acid is compatible with its limited percutaneous absorption. Classical 7.2 Reproductive and developmental effects pharmacokinetics analyses were used to compare 7.2.1 Humans the circulating concentrations of all-bans-retinoic 7.2.1.1 Reproductive effects acid and its metabolites after topical application of Oral administration of all-bans-retinoic acid at 0.05% all-trans-retinoic acid cream. Topical appli- 20-30 mg/day (- 0.4 mg/kg bw per day) to 12 cation of all-trans-retinoic acid did not appreciably patients with acne for 90-300 days was associated alter the endogenous plasma concentration of with dry oral and nasal mucous membranes. The retinoids (Nau, 1993; Johnson, 1997). A physiolog- treatment had no measurable effect on sperm ically based pharmacokinetics method for inter- count, sperm density; total and progressive motil- species scaling of internal dose showed that the ity or morphology other than an increase in total effective concentration of parent all-trans-retinoic ejaculate volume (Plewig et al., 1979). acid and its metabolites across species was of the same order of magnitude (Clewell et al., 1997). 7.2.1.2 Developmental effects After topical application of 0.05% all-trans-retinoic acid to the face, arms and chest, the circulating (a) Topical exposure levels of the compound and its metabolites were The available case reports and epidemiological unchanged (Clewell et al., 1997; Wilihite & studies do not provide evidence for developmental Clewell, 1999). The low dose that was absorbed, effects after administration of the standard dose of metabolized and delivered after topical application all-trans-retinoic acid (Rosa, 1992). In a retrospec- to intact human skin is consistent with the find- tive study of 215 pregnant women with a history ings in vivo in humans (Jensen et al., 1991; Buchan of dermal use of all-trans-retinoic acid, no evidence etal., 1994; Latriano et al., 1997), rodents (Wilihite was found for an increased risk of major malfor- et al., 1990) and lagomorphs (Christian et al., mations (Jick et al., 1993). In United States 1997). Medicaid data on 1120 cases of topical use of all-trans-retinoic acid during pregnancy, the (c) Oral exposure frequency distribution of abnormal outcomes was Although all-trans-retinoic acid is an isomer of no different from that expected for the country as 13-cis-retinoic acid, which is responsible for a whole (Rosa, 1992). retinoid embryopathy (Creech-Kraft & Wilhite, Eighteen case reports of anomalies in children 1997), clinical experience with all-trans-retinoic of mothers who had used all-trans-retinoic acid acid at the customary dose of 45 mg/ml per day as during pregnancy included four cases of treatment for acute promyelocytic leukaemia in holo-prosencephaly but which did not share all or early or in late gestation has shown no evidence of most of the characteristic features of retinoid fetotoxicity.

124 All-trans-Retinoic acid

Three case reports have been published of oral 7.22 Experimental models administration of all-trans-retinoic acid during 7.2.2.1 Reproductive effects early pregnancy. Treatment at 45 mg/m2 per day In rats given all-trans-retinoic acid by dietary with prednisone at 1 mg/kg bw per day from day supplementation at 0.03-0.75 mg/kg bw per day or 36 through week 30 did not induce terata, and the by oral intubation at 0.4, 5, 10 or 50 mg/kg bw per infant showed neither retinoid dermatitis nor day for 12 or 13 weeks, decreased testicular weights cheilitis, although it developed jaundice and were observed, and there was histological evidence respiratory distress shortly after delivery. These of decreased spermatogenesis. Similar results were conditions resolved without sequelae after found in dogs fed all-trans-retinoic acid by capsule supporting therapy, at 7 and 11 days, respectively, at a dose of 5 or 50 mg/kg bw per day for 13 weeks and were considered not to be treatment-related. (Kamm, 1982). At 15 months, the child's growth and development were normal (Simone et al., 1995). Similar treat- 7.2.2.2 Developmental effects ment beginning at week 13 had no adverse effect Numerous studies have shown that embryos of on delivery, survival or early neonatal develop- mammalian species are susceptible to the embryo- ment (Morton et al., 1995), and no effects were toxic effects of excess all-trans-retinoic acid seen of treatment beginning at 14 weeks of gesta- (Table 7) at doses that do not cause overt maternal tion and continued for 60 days (Lin et al., 1996). toxicity (Geelen, 1979; Agnish & Kochhar, 1993). Exposure late in pregnancy (week 30 until The embryotoxic effects of retinoids can also be parturition) was not associated with fetotoxicity in induced in other vertebrate classes, such as birds four case reports. Oral administration of all-trans- (Tickle et al., 1982), amphibians (Durston et al., retinoic acid at 45 mg/m2 per day to patients at 1989) and fish (Holder & Hill, 1991). 23-28 weeks' gestation and continued for 30 days Since the initial studies, more than 70 types of (Harrison et al., 1994; Watanabe et al., 1995) or anomalies affecting almost every organ system reduced after remission of the leukaemia had been related to excess intake of all-trans-retinoic acid achieved after 28 days to 22 mg/m2 per day for 14 have been described in more than 100 reports days (Stentoft et al., 1994) produced treatment- (Soprano & Soprano, 1995). The anomalies related changes in the mothers (gingival hypertro- described in mammalian embryos (monkeys, rab- phy and increased activity of circulating liver bits, rats, mice and hamsters) are microcephaly, enzymes). Spontaneous delivery at weeks 30-32 in holoprosencephaly, spina bifida, encephalocele, each case was uneventful; evaluation of the chil- exencephaly, hydrocephaly, facial nerve palsy, cra- dren at five to eight months gave no evidence of nial abnormalities, maxillary hypoplasia, ophthalmological or neurological abnormalities; mandibular hypoplasia, cleft palate, cleft lip, growth and development were considered normal micrognathia, absent or deformed ear, exophthal- (Harrison et al., 1994; Stentoft et al., 1994; mus, microphthalmus, anophthalmus, coloboma, Watanabe et al., 1995). Treatment with all-trans- nasal defects, facial clefting, oesophageal atresia, retinoic acid at 45 Mg/M2 per day from week 34 cardiovascular malformations, hypoplastic aorta, through week 38 increased the concentration of rib fusions, vertebral transformations, omphalo- 13-cis-retinoic acid in cord blood to 0.44 ng/mL coele, multiple limbs, shortened limbs, ectro- and that of its 4-oxo metabolite to 1.3 ng/mL, but dactyly, syndactyly, anal atresia, thymic hypopla- neither all-trans-retinoic acid nor all-trans-4-oxo- sia, amastia and defects of the uterus, testis, kidney, retinoic acid was detected. Exposure to all-trans- thyroid and pituitary. The important features of retinoic acid did not induce fetotoxicity, and deliv- the teratogenicity of all-trans-retinoic acid are the ery was uneventful; follow-up at nine months wide spectrum of its effects on virtually every showed no complications (Lipovsky et al., 1996). organ system of the body and the impressive stage- Physical and mental development were normal specificity of the induced effects, as described clas- in eight infants born to mothers given all-tnins- sically by Shenefelt (1972). For example, treatment retinoic acid orally at 70 mg/kg bw from week 30 of mice embryos before implantation (days 4.5-5.5 until birth for treatment of acute promyelocytic of gestation) resulted in a bizarre multiple leukaemia (Maeda et al., 1997). hindlimb phenotype in which the pelvic girdle is

125 IARC Handbooks of Cancer Prevention

Table 7. Teratogenic effects of all-trans-retinoic acid

Species Dose (ma/k bw) Effects Reference

Mouse 70; GD 12 100% cleft palate; alteration Degitz et aL (1998) of mesenchyme

Thymie defects, increased Mulder et aL (1998) expression of Hoxa 3 Chick embryo Soaked bead, stage 20 Face and wing patterning; Helms et aI. (1997) Sonic hedgehog expression

Cynomolgus 5; GD 16-26 No teratogenic effects Tzlmas et al. (1996) monkey 2x5; GD 26-31

Rat 20-30; GD 10 Cranial facial defects Tembe et al. (1996)

Rabbit 5-25; GD 10 Cranial facial detects; deformed tail

NMII mouse 20 mmcilkg bw all- trans-Retinyl--D- Nau et aI. (1996) GD 11 glucuronide more teratogenic than all-trans-retinoic acid

C57BL mouse 7.5; GD 7 Holoprosencephaly, Sulik eta[. (1995) 1.25; GD 7 anophthalmia, microphthalmia

COl mouse 2.5; GD 7 Exencephaly Sulik et al. (1995)

CDI mouse 20; GD 9 Fused ribs and vertebrae tail; Rasco & Hood (1995a,b) spina biflda increased by stress

Rat 40; GO 13,14 Cleft palate Ikemi et al. (1995)

Rat, rabbit 6; GD 12 Decreased concentrations and Collins et al. (1995) 6; GD 7-12 effects after multiple applications

Rat 6; GD 6-15 Axial skeletal defects Collins at al. (1994)

Rabbit 6; GD 6-18 Low teratogenic response Tzimas et al. (1994a)

C57BL mouse 28; GD 8 (3 x) Spina bifida aperta Ailes & Sulik (1990)

Cynomolgus 10; GD 10-20 Ear defects, mandibular Hendrlckx & Hummler (1992) monkey 2 x 10; GD 21-24 cleft palate

Rat 10; GD 6-15 Not specified Kamm (1982)

Rabbit 6; GD 6-18 Not specified

Mouse 3; GD 6-15 Not specified

NMRI mouse 10; GD 11 Cleft palate, limb defects Creech Kraft et al. (1989)

C57BL mouse 0-200; GD 10, 12 Cleft palate, synergistically Birnbaum et al. (1989) increased by TCDD

Xenopus embryo Stage 10; 10-5 moLIL Microcephaly Durston et al. (1989) GD, gestation day; TCDD, 2,3,7,8-tetrachlordibenzo-para-dioxin

126 All-trans-Retinoic acid duplicated (Rutledge et ai., 1994; Niederreither et in the serum of embryos than dams (Dencker et ai., ai., 1996). Exposure of postimplantation embryos 1987, 1990). (days 7-9.5 of gestation) typically results in the The duration of exposure to retinoids is craniofacial, central nervous system, ear, cardiovas- another major determinant of teratogenic out- cular and thymus defects listed above; and expo- come. For example, when 5 mg/kg bw of all-trans- sure at later stages of development (days 9.5-12 of retinoic acid were administered orally to rats on gestation) is associated with defects of the limbs, gestation day 9, no specific embryotoxicity was palate and genitourinary tract (Kalter & Warkany, seen, whereas subcutaneous treatment induced a 1961; Shenefelt, 1972; Kistler, 1981; Sulik et ai., high incidence of embryolethality and skeletal 1995). Even during the later phase, forelimb anomalies. The AUC but not the C ç in maternal defects appear at slightly earlier times of treatment plasma correlated with the embryonic outcome than hindlimb defects. (Tzimas et al., 1997). Importantly, teratogenic out- Studies have also been conducted on the effects comes in mice are observed at doses (10 mg/kg bw) of all-trans-retinoic acid on the viability and behav- well below those at which metabolism is saturated iour of offspring. For example, after administration (100 mg/kg bw) (Tzimas et ai., 1995). of all-trans-retinoic acid on days 8-10, 11-13 and A common characteristic of the pharmacoki- 14-16 of gestation in rats, hyperactivity in the netics of all-trans-retinoic acid in rats, rabbits and open field and in running wheels was observed at cynomolgus monkeys is a diminution of the doses > 4 mg/kg bw. Performance in the Morris plasma concentrations after repeated dosing, maze was poorer than in the controls after a dose although the extent and the time course of this of 2.5 mg/kg bw on days 11-13. The scores on phenomenon vary among species. In pregnant rats active avoidance tests were lower after a dose of 6 given all-trans-retinoic acid at a single oral dose of mg/kg bw. It was concluded that all-trans-retinoic 6 mg/kg bw on day 12 of gestation or the last of six acid induced functional defects at doses that did daily doses of 6 mg/kg bw on days 7-12 of not cause morphological defects (Nolen, 1986). gestation, multiple dosing resulted in a pro- The pharmacokinetics of all-trans-retinoic acid nounced reduction in the exposure to this com- in pregnant animals has been studied extensively, pound and to all-trans-4-oxoretinoic acid, since the and the findings shed light on the concentrations plasma AUG values were ninefold and fivefold of this retinoid and its metabolites at the target site higher for the two compounds, respectively, after that are necessary to induce effects, the critical the single than after multiple administrations. In pharmacokinetics and the reasons for the species rabbits treated in the same way, the effect on the similarity in teratogenic responses. all-tians- plasma concentration of all-trans-retinoic acid after Retinoic acid is rapidly eliminated from the circu- repeated dosing was also evident, although it was lation of mice, rats, hamsters, rabbits, monkeys less marked than in rats (Collins et ai., 1994). and humans, with apparent half-lives < 3 h Similar results were found after rats were given all- (Siegenthaler & Saurat, 1989; Allenby et al., 1993; trans-retinoic acid at 17 mg/kg bw three times at 3- Fiorella et ai., 1993). The authors suggested that h intervals (Tembe et al., 1996) and in rats and rab- the presence of CRABPs in tissues of all species bits given either a single dose of all-ti-ans-retinoic examined to date and their capacity to facilitate acid on day 12 of gestation or multiple daily doses the metabolism of all-trans-retinoic acid may on days 7-12 (Collins et al., 1995), although the explain why it is rapidly eliminated. Studies in change was smaller in rabbits. The decrease in mice, rats and rabbits revealed that the embryonic plasma concentrations after repeated dosing has concentrations of all-trans-retinoic acid and all- been attributed to up-regulation of all-trans- trans-4-oxoretinoic acid were similarly high or retinoic acid metabolism and excretion (Adamson higher than those in plasma after administration et ai., 1993). of all-trans-retinoic acid (Tzimas et ai, 1994b; Kochhar et al., 1995). Binding of all-trans-retinoic 7.3. Genetic and related effects acid to embryonic CRABPs or other as yet uniden- 7.3.1 Humans tified retinoid binding proteins in the embryo is No data were available to the Working Group. likely to contribute to the greater concentrations

127 IARC Handbooks of Cancer Prevention

7.3.2 Experimental models 8. Summary of Data Most of the information on the mutagenicity of all-trans-retinoic acid in the Salmonella/microsome 8.1 Chemistry, occurrence and human test was generated in studies of the ability of this exposure compound to modulate the mutagenic activity of all-trans-Retinoic acid is derived from retinol by known carcinogens (Table 8). The number of tester oxidation of the C-15 alcohol group to a carboxylic strains, the range of doses and the use of S9 mix is acid. Like all members of the vitamin A family, it is therefore somewhat incomplete. When the lipohilic, sensitive to light, heat and oxygen and compound was tested at 2 and 4 pmol/plate in readily isomerized to a mixture of cis and trans Salmonella strains TA101 and TA100 without S9 isomers. Because of its acidic nature, it is slightly and TA98 with S9, no effect was observed on muta- more soluble in water than retinol or retinal but tion frequencies (De Flora et al., 1994). Treatment still poorly so. Because of its conjugated tatraene of S. typhimurium at doses of 2.5-40 jig/plate had structure, all-trans-retinoic acid has characteristic no toxic effect and did not increase the mutation absorption spectra in the ultraviolet and visible, frequencies in TA98, TA100, TA102 and TA1535, infrared and resonance Raman portions of the with or without the addition of S9; however, the elctromagnetic spectrum. actual data were not shown (Qin & Huang, 1985). all-trans-Retinoic acid is normally present in All the other studies were restricted to single tester blood and tissues of animal species in smaller strains. No effect was reported on the spontaneous amounts than retinol and retinyl ester and is essen- mutation frequencies of TA104 tested only in the tially absent from plant tissues. Human exposure absence of S9 (Han, 1992), and the mutation fre- occurs during topical or oral treatment for medical quencies in TA100 (Bhattacharya et al., 1987) and or cosmetic purposes. TA98 (Wilmer & Spit, 1986; Whong et al., 1988) all-trans-Retinoic acid has been used to treat were unchanged, in all cases tested only in the dermatological disorders and several forms of can- presence of S9. cer. The efficacious doses are 0.5-2 mg/kg of body In cultured mammalian cells, all-trans-retinoic weight per day when given orally and 0.1% as a acid did not induce unscheduled DNA synthesis in cream or gel when administered topically. rat primary hepatocytes (Bhattacharya et al., 1987), all-trans-Retinoic acid is usually separated by It did not alter the spontaneous mutation high-performance liquid chromatography and frequency at the Hprt locus in Chinese hamster detected by its absorption at 350 run. After ovary cells (Budroe et al., 1988) and did not change chemical formation of a suitable ester, it can also be chromosomal aberration frequencies in Chinese separated and detected by gas—liquid chromato- hamster ovary or human embryonic palatal mes- graphy and can be quantified by mass spectro- enchymal cells (Patel et al., 1998; Watanabe & metry. Pratt, 1991). Although no effect on spontaneous sister chromatid exchange frequency was reported 8.2 Metabolism and kinetics in three studies (Sirianni et al., 1981; Cozzi et al., The metabolism, kinetics and distribution of all- 1990; Watanabe & Pratt, 1991), two other studies trans-retinoic acid are complex but relatively well showed an effect. Juhl etal. (19 78) reported a dose- understood. It is present in most tissues of healthy dependent increase in sister chromatid exchange animals, albeit at low concentrations. Most of the frequency in human diploid fibroblasts exposed to all-trans-retinoic acid in tissues is synthesized in this retinoid. More recently, Patel et al. (1998) situ from all-trans-retinol through the actions of reported a statistically significant increase in sister two oxidoreductases (dehydrogenases) that catal- chromatid exchange frequency in Chinese ham- yse the sequential oxidation of all-trans-retinol to ster ovary cells, but only after continuous all-trans-retinal and of all-trans-retinal to all-trans- treatment for 20 h and not after exposure for 3 h retinoic acid. The identities and characteristics of and only at the highest dose tested (0.8 pg/ml). S9 these enzymes have not been established unequiv- was used in neither of the latter two studies. ocally. The low concentrations of all-trans-retinoic No reports were found of studies of the geno- acid present in plasma (4-14 nmol/L) may be taken toxicity of all-trans-retinoic acid in vivo. up by tissues.

128 Table 8. Genetic and related effects of retinoids in short-term tests in vitro and in vivo

End- Code Test system Resulta LED/H 1Db Reference point Without exo- With exogenous genous metabolic metabolic system system

G SAO TA100, reverse mutation - - 40 tg/plate Qin & Huang (1985) G SAO TA100, reverse mutation O + 0.5 1mol/pIate Bhattacharya etal. (1987) G SA2 TA102, reverse mutation - - 40 pig/plate Qin & Huang (1985) G SM lAi 04, reverse mutation - 0 10 pimol/plate Han (1992) G SA5 TA1535, reverse mutation - - 40 pig/plate Oin & Huang (1985) G SAS TA98, reverse mutation - - 40 pig/plate Qin & Huang (1985) G SA9 TA98, reverse mutation O - 500 nmol/plate Wilmer & Spit (1986 G SA9 TA98, reverse mutation O - 2.6 pimol/plate Whong at al. (1988) D IJRP Unscheduled DNA synthesis, O - 50 mmol/L Budroe etal. (1987) rat primary hepatocytes G GCO Gene mutation, Chinese - - 25 mmoL/L (+S9) Budroe etal. (1988) hamster ovary cells, Hprt 100 mmol/L (-S9) locus C CIC Chromosomal aberrations, - 0 1.6 mg/mI Patel at al. (1998) Chinese hamster ovary cells in vitro C CIH Chromosomal aberrations, - - 68 mmol/L (-99) Watanabe & Pratt human embryonic palatal 140 mmol/L (+S9)(1991) mesenchymal cells in vitro S SIC Sister chromatid exchange, (+) 0 0.8 mg/ml Patel at al. (1988) Chinese hamster ovary cells in vitro S SIC 0 Sister chromatid exchange, - 0 50 pimol/L Cozzi at al. (1990) Chinese hamster epithelial liver cells in vitro S SIS Sister chromatid exchange, - 0 25 mg/ml Sirianni et aL Chinese hamster V79 cells (1981) in vitro S SIH Sister chromatid exchange, - - 68 pimol/L (—S9) Watanabe & human embryonic palatal 140 pimol/L (+S9) Pratt (1991) mesenchymal cells in vitro S SHF dSister chromatid exchange, + 0 1 pig/MI JuhI at ai. (1978) human fibroblasts in vitro a Result: +, positive; (+) weak positive, only one dose showed significant increase; - considered to be negative; 0, not tested b LED, lowest effective dose that inhibits or enhances the investigted effect; HID, highest ineffective dose c Isomer type was all-trans-retìnoic acid, personal communication from author d Presumed to be all-trans-retinoic acid since, exception for JuhI at al., all sources listed as Sigma. 13-cis-Retinoic acid listed only in Sigma catalogue from 1988 and 9-cis-retinoic add from 1996. Budroe etal. (1988) probably used the same retinoic acid source as in 1987. The early study by JuhI etal. (1978) probably also involved all-trans-retinoic acid. dlype of retinoid used most likely all-trans-retinoic acid, but it may have beenl3-cis-retinolc acid since publication date was after 1987.

129 IARC Handbooks of Cancer Prevention

Pharmacokinetic studies indicate that all-trans- enhanced N-nitrosodiethylamine-induced liver retinoic acid is rapidly taken up from the gastroin- carcinogenesis, but in one study in rats it was testinal tract and rapidly cleared from the circula- ineffective against N-methyl-N-nitrosourea- tion. Repeated doses of all-trans-retinoic acid induced mammary carcinogenesis. markedly lower both its maximal concentrations In vitro, all-trans-retinoic acid inhibited the in plasma and the effective concentration in transformation of normal cells by carcinogens and plasma integrated over time, implying that it of immortalized cells by viral oncogenes. ail-b-ans- induces its own catabolism in vivo. The recent Retinoic acid inhibited cell proliferation in mono- identification and cloning of an all-trans-retinoic layer cultures and modulated the differentiation of acid-inducible cytochrome P450 (CYP26) that a large number of immortalized, transformed and catalyses oxidation of this retinoid adds to tumorigenic cell types derived from trachea, skin biochemical understanding of the observation. and cervical epithelia. all-trans-Retinoic acid also Although the metabolism of all-trans-retinoic acid suppressed the anchorage-independent growth of in human beings and animal models is probably a variety of tumour cell lines. It suppressed abnor- similar biochemically, the metabolite profiles and mal squamous differentiation in immortalized and concentrations differ markedly among species. transformed cells and re-regulated growth control Although no animal model can be considered truly mechanisms by blocking cells in the G1 phase of to reflect the human situation, the metabolite the cell cycle. profiles and concentrations in monkeys most The inhibitory effects of all-ti-ans-retinoic acid closely resemble those seen in humans. against carcinogen-induced genotoxicity were most often associated with agents that require 8.3 Cancer-preventive effects bioactivation. Studies in animals and humans 8.3.1 Humans given topical applications of all-trans-retinoic acid No studies have been reported of the use of all- have demonstrated alterations in enzymes that trans-retinoic acid for the prevention of invasive mediate carcinogen metabolism. all-b-ans-Retinoic cancer in humans. acid can also act as a radical scavenger, suggesting The results of one randomized, controlled trial that it acts on initiation by carcinogens. indicate that topically applied all-trans-retinoic Carcinogen-induced neoplastic transformation acid is effective in reversing moderate dysplasia of in vitro was inhibited when all-b-ans-retinoic acid the uterine cervix (cervical intra-epithelial neopla- was added after removal of the carcinogen, while sia-Il) but not against more severe dysplastic most studies in experimental animals in which lesions. It was reported to be efficacious against inhibition of carcinogenesis was demonstrated actinic keratosis of the skin in one randomized trial involved treatment with all-trans-retinoic acid after but not in another at a lower dose; the descriptions exposure to the carcinogen. Thus, it can act in both of the studies were insufficient for detailed evalua- the initiation and post-initiation phases of carcino- tion. Two further trials suggest that topically genesis. applied all-trans-retinoic acid is effective against dysplastic naevi. 8.3.3 Mechanisms of cancer prevention Most studies of the effects of all-trans-retinoic acid 8.3.2 Experimental models on carcinogenesis indicate that inhibition of the The preventive efficacy of all-trans-retinoic acid post-initiation stage is the main mechanism of its was evaluated in models of skin, liver and mam- putative preventive effects. The mechanisms of mary gland carcinogenesis. The results of several action may be related to the ability of retinoids to experiments in mice indicated that all-trans- antagonize tumour promotion by trans-repressing retinoic acid was effective against two-stage skin the activity of AP-1. The ability of all-trans-retinoic carcinogenesis when 7,12 dimethylbenz[a]- acid to inhibit cell proliferation is associated with anthracene was used as the initiator, whereas it multiple effects on G1 regulatory proteins which enhanced skin carcinogenesis induced by this ultimately result in growth arrest in G0 and G1. carcinogen alone or with ultraviolet radiation. One Another possible mechanism is modulation of the study in mice indicated that all-trans-retinoic acid autocrine and paracrine loops that mediate

130

All-trans-Retinoic acid

positive and negative growth signals. Restoration disturbances, bone pain and inflammation, nausea of normal differentiation or enhancement of dif- and vomiting, mucositis, pruritus, increased sweat- ferentiation in cells with aberrant differentiation ing, visual disturbances and alopecia). Transient may contribute to the putative cancer-preventive increases in the concentration of triglycerides and effects of all-trans-retinoic acid. Restoration of con- the activity of transaminases are common and can trols on growth can also be mediated by enhance- sometimes lead to severe complications such as ment of intercellular gap-junctional communica- pancreatitis and hepatotoxicity. Moderate to severe tion and suppression of prostaglandin biosynthe- headaches are commonly experienced during oral sis. Induction of apoptosis provides the ultimate therapy with all-trans-retinoic acid and may limit means for eradicating abnormal clones of prema- the dose that can be given. Cases of pseudotumour lignant cells. Enhancement of cell adhesion and cerebri, with clinical signs of headache, nausea, inhibition of cell motility affect the invasive step double vision and bilateral papilloedema, have in which carcinoma in situ is converted into a been reported. Concern has been raised that all- malignant tumour. Lastly, inhibition of angiogene- trans-retinoic acid may increase the risk for relapses sis may block the growth of advanced premalig- at unusual sites in patients with acute promyelo- nant lesions and locally invasive malignancies. cytic leukaemia. One of the most serious reactions to orally 8.4 Other beneficial effects administered all-trans-retinoic acid is 'retinoic acid all-trans-Retinoic acid has been shown to be of syndrome', an acute, life-threatening respiratory benefit to patients suffering from a variety of der- disorder experienced by about 25% of patients matological disorders. with acute promyelocytic leukaemia who are being treated with all-trans-retinoic acid. The syndrome 8.5 Carcinogenicity is characterized by fever, dyspnoea, weight gain, No data were available to the Working Group. radiographic pulmonary infiltrates and pleural or pericardial effusions and has been observed with 8.6 Other toxic effects and without concomitant leukocytosis. High doses 8.6.1 Humans of glucocorticoids given at the first sign of the The toxic effects associated with topical applica- syndrome appear to reduce the rates of morbidity tion of all-trans-retinoic acid are generally local- and mortality, but as much as 60% of patients with ized, cutaneous and reversible after treatment is acute promyelocytic leukaemia who are taking all- discontinued. The most frequent adverse effects trans-retinoic acid orally require such treatment. include peeling, dry skin, burning, stinging, No signs of reproductive toxicity were seen in erythema and pruritus. The reactions are usually of one study in which 12 fertile men were exposed to mild to moderate severity, occur early during all-trans-retinoic acid for up to 300 days. There therapy and recur after an initial decline. Patients were no reports of adverse pregnancy outcomes using topical all-trans-retinoic acid have height- after oral administration of all-trans-retinoic acid ened sensitivity to sunlight and weather extremes, to one patient with acute promyelocytic leukaemia and temporary hyper- or hypopigmentation has during early pregnancy, and no signs of retinoid been reported. Concentrations of 0.05-0.2% embryopathy were seen in seven such patients applied on a sponge inserted vaginally in a cervical treated with all-trans-retinoic acid later in preg- cap for four days commonly produced vaginal nancy; however, there have been no retrospective irritation, ulceration and discharge, with no evi- or prospective follow-up studies of the childen of dence of systemic toxicity. such patients. The available data do not indicate all-trans-Retinoic acid administered orally at 45 an increased risk for teratogenic effects after der- mg/m2 per day (the recommended daily dose) mal application of all-trans-retinoic acid. results in drug-related toxicity in virtually all patients with acute promyelocytic leukaemia. The 8.6.2 Experimental models most frequent adverse events are similar to those In mice given all-trans-retinoic acid orally, described in patients taking high doses of vitamin the major dose-related findings included bone A (headache, fever, skin and mucous membrane rarefaction, bone fracture, elevated serum alkaline

131

IARC Handbooks of Cancer Prevention

phosphatase activity, testicular degeneration, der- 9. Recommendations for Research mal and epidermal inflammation and hyperkeratosis. In rats, decreased plasma albumin and haemo- 9.1 General recommendations for research globin concentrations and increased serum alka- on all-trans-retinoic acid and other line phosphatase activity were seen. retinoids Few studies of genotoxicity with all-trans- The results of studies in which the protocols dif- retinoic acid in vitro are available, and the results of fered widely or in which proper controls and dif- those that have been reported were largely negative. ferences in the baseline conditions were neglected, The frequency of sister chromatid exchange was omitted or inadequately described are difficult to increased in the presence of this retinoid in two evaluate and compare. Standard protocols are studies but not in three others. No reports were urgently needed to evaluate the cancer-preventive available of the effects of all-trans-retinoic acid on properties of retinoids. Such protocols should mutation or chromosomal changes in animals in vivo. specify continuous quality control of supplements all-trans-Retinoic acid applied topically at doses and the type of formulation to be used. Such a of 2-5 mg/kg of body weight per day for 90 days strategy should be developed for molecular, cellu- reduced testicular and ovarian weights in mice, lar, experimental animal and human studies, in with no pathological changes; no such effect was order to: seen in dogs given doses up to 1 mg/kg of body • understand the role of nuclear retinoid recep- weight per day for 13 weeks. all-trans-Retinoic acid tors in cancer chemoprevention; was a potent teratogen in all experimental species examined; this finding is compatible with its • develop more relevant models of chemopre- extensive placental transfer, with consequent vention with efficacious retinoids, including exposure of embryos, and its interaction with assays based on over-expression of oncogenes retinoic acid receptors. The extent of teratogenicity and ablation of tumour suppressor genes; is similar in different mammalian species, reflect- ing its rate of elimination. The teratogenic effects, • identify suitable biomarkers that can serve as which involve nearly every fetal organ system, surrogate outcome measures of invasive cancer depend on the route and the time of administra- in assessing the efficacy of retinoids in chemo- tion during gestation. In general, administration prevention trials; during early organogenesis results in greater teratogenicity than administration during late organo- • identify more precisely the structural properties genesis, partly because of decreasing placental of retinoids that affect their toxicity; transfer with advancing gestation. Behavioural defects have been observed in rodents exposed to • identify the mechanisms of action by which all-trans-retinoic acid in utero. Topical application retinoids effect their characteristic spectrum of results in low bioavailability and little or no terato- toxicity; genicity. The extensive placental transfer of all-trans- • design and develop retinoids with improved retinoic acid is closely associated with its binding therapeutic ratios for cancer chemoprevention; to the abundant embryonic cellular retinoic acid binding proteins. The effective concentration of • understand better the mechanisms by which all-trans-retinoic acid in plasma integrated over retinoids target specific tissues; time that reaches the embryo during the sensitive stages of organogenesis defines the potency of the • understand the factors that determine homeo- teratogenic effect. Multiple dosing results in a static mechanisms for retinoids in cells and reduction in the concentration of the drug in whether these regulatory mechanisms are maternal and fetal compartments, probably important in cancer chemoprevention; because induction of metabolic enzymes increases 4-oxidation and glucuronidation. • understand better the structural properties of retinoids that influence their pharmacokinetics;

132 All-trans-Retinoic acid

• clarify the reasons underlying the loss of epithelial cell differentiation. Cancer Res., 51, retinoid X receptors in the process of cellular 3982-3989 transformation; and Agarwal, C., Chandraratna, R.A., Teng, M., Nagpal, S., Rorke, E.A. & Eckert, R.L. (1996) Differential regula- • understand the interaction and potential tion of human ectocervical epithelial cell line prolif- chemopreventive efficacy of retinoids in com- eration and differentiation by retinoid X receptor- bination with other drugs. and retinoic acid receptor-specific retinoids. Cell Growth Differ., 7, 521-530 Agnish, N.D. & Kochhar, D.M. (1993) Developmental 10. Evaluation toxicity of retinoids. In: Koren G., ed., Retinoids in Clinical Practice. The Risk-Benefit Ratio. New York, 10.1 Cancer-preventive activity Marcel Dekker, pp. 47-76 10.1.1 Humans Allenby, G., Bocquel, M.T., Saunders, M., Kazmer, S., There is inadequate evidence that all-trans-retinoic Speck, J., Rosenberger, M., Lovey, A., Kastner, P., acid has cancer-preventive activity in humans. Grippo, J.F., Chambon, P. & Levin, A.A. (1993) Retinoic acid receptors and retinoid X receptors: 10.1.2 Experimental animals Interactions with endogenous retinoic acids. Proc. There is inadequate evidence that all-trans-retinoic Nati Acad. Sci. USA, 90, 30-34 acid has cancer-preventive activity in experimental Ailes, A.J. & Sulik, K.K. (1990) Retinoic acid-induced animals. spina bifida: Evidence for a pathogenetic mechanism. Development, 108, 73-81 10.2 Overall evaluation Andreatta-Van Leyen, S., Hembree, J.R. & Eckert, R.L. all-trans-Retinoic acid has not been established to (1994) Regulation of insulin-like growth factor 1 have cancer-preventive activity in humans. binding protein 3 levels by epidermal growth factor Therapy with this retinoid gives rise to significant and retinoic acid in cervical epithelial cells. J. Cell toxic effects, and it is an established teratogen in Physiol., 160, 265-274 experimental animals. Arizano, MA., Byers, S.W., Smith, J.M., Peer, C.W., Mullen, L.T., Brown, CC., Roberts, A.B. & Sporn, M.B. (1994) Prevention of breast cancer in the rat with 9- 11. References cis-retinoic acid as a single agent and in combination Cancer Res., 54, 4614-4617 Acevedo, P. & Bertram, J.S. (1995) Liarozole potentiates with tamoxifen. Physicians' Desk Reference. 52nd Ed. the cancer chemopreventive activity of and the up- Arky, R. (1998) regulation of gap junctional communication and con- Montvale, NJ, Medical Economics Company, pp. nexin43 expression by retinoic acid and beta-carotene 1986-1989,2154-2155,2518-2520 R.B., Ashenfelter, K.O., Eckhoff, C., Levin, in 1011/2 cells. Carcinogenesis, 16, 2215-2222 Armstrong, S.S. (1994) General and reproductive Adamson, P.C., Boylan, J.F., Balis, F.M., Murphy, R.F., A.A. & Shapiro, In: Sporn, M.B., Roberts, A.B. Godwin, K.A., Gudas, U. & Poplack, D.G. (1993) toxicology of retinoids. Retinoids. Biology, Time course of induction of metabolism of all-buns- & Goodman, D.S., eds, The 2nd Ed. New York, Raven retinoic acid and the up-regulation of cellular retinoic Chemistry, and Medicine. acid-binding protein. Cancer Res., 53, 472-476 Press, pp. 545-572 Barua, A.B. & Fun, H.C. (1998) Properties of retinoids: Adamson, P.C., Reaman, G., Finklestein, J.Z., Feusner, J., Structure, handling, and preparation. In: Redfem, Berg, S.L., Blaney, S.M., O'Brien, M., Murphy, R.F. & Retinoid Protocols. Totowa, Humana Balls, F.M. (1997) Phase I trial and pharmacokinetic C.P.E, ed., NJ, study of all-trans-retinoic acid administered on an Press, pp. 3-28 van Breemen, R.B. intermittent schedule in combination with inter- Barua, A.B., Fun, H.C., Olson, J.A. & (1999) Vitamin A and carotenoids. In: DeLeenheer, feron-a2a in pediatric patients with refractory cancer. van Bocxlaer, eds, Modern Clin. Oncol., 15, 3330-3337 A., Lambert, W. & J., J. Chromatographic Analysis of the Vitamins, 3rd Ed. New Agarwal, C., Rorke, E.A., Irwin, J.C. & Eckert, R.L. (1991) York, Marcel Dekker (in press) Immortalization by human papillomavirus type 16 alters retinoid regulation of human ectocervical

133 IARC Handbooks of Cancer Prevention

Behbakht, K., DeGeest, K., Turyk, M.E. & Wilbanks, G.D. Buchan, P., Eckhoff, C., Caron, D., Nau, H., Shroot, B. & (1996) All-trans-retinoic acid inhibits the proliferation Schaefer, H. (1994) Repeated topical administration of cell lines derived from human cervical neoplasia. of all-trans-retinoic acid and plasma levels of retinoic Gynecol. Oncol., 61, 31-39 acids in humans. J. Am. Acad. Dermatol., 30, 428-434 Bertram, J.S. (1980) Structure-activity relationships Budavari, S., O'Neil, M.J., Smith, A., Heckelman, P.E. & among various retinoids and their ability to inhibit Kinneary, J.F. (199 6) The Merck Index. An Encyclopedia neoplastic transformation and to increase cell adhe- of Chemicals, Divgs, and Biologicals, 12th Ed. sion in the C3H/1OT1/2 CL8 cell line. Cancer Res., 40, Whitehouse Station, NJ, Merck & Co., p. 1404 3141-3146 Budd, G.T., Adamson, P.C., Gupta, M., Homayoun, P., Bhattacharya, R.K., Firozi, P.F. & Aboobaker, V.S. (1984) Sandstrom, 5K., Murphy, R.F., McLain, D., Tuason, L., Factors modulating the formation of DNA adduct by Peereboom, D., Bukowski, R.M. & Ganapathi, R. aflatoxin Bi in vitro. Carcinogenesis, 5, 1359-1362 (1998) Phase I/TI trial of all-trans-retinoic acid and Bhattacharya, RK, Francis, A.R. & Shetty, T.K. (1987) tamoxifen in patients with advanced breast cancer. Modifying role of dietary factors on the mutagenicity Clin. Cancer Res., 4, 635-642 of aflatoxin Bi: In vitro effect of vitamins. Mutat. Res., Budroe, J.D., Shaddock, J.G. & Casciano, D.A. (1987) 188,121-128 Modulation of ultraviolet light-, ethyl methanesul- Birnbaum, L.S., Harris, M.W., Stocking, L.M., Clark, A.M. fonate-, and 7,12-dimethylbenz[a]anthracene-induced & Morrissey, R.E. (1989) Retinoic acid and 2,3,7,8- unscheduled DNA synthesis by retinol and retinoic tetrachlorodibenzo-p-dioxin selectively enhance ter- acid in the primary rat hepatocyte. Environ. Mol. atogenesis in C57BL/6N mice. Toxicol. Appi. Mutag., 10, 129-139 PharmacoL, 98, 487-500 Budroe, J.D., Schol, H.M., Shaddock, J.G. & Casciano, Blaner, W.S. & Olson, J.A. (1994) Retinol and retinoic D.A. (1988) Inhibition of 7,12-dimethylbenz[a]- acid metabolism. In: Spom, M.B., Roberts, A.B. & anthracene-induced genotoxicity in Chinese hamster Goodman, D.S., eds, The Retinoids: Biology, Chemistty, ovary cells by retinol and retinoic acid. Carcinogenesis, and Medicine, 2nd Ed. New York, Raven Press, pp. 9,1307-1311 229-255 Caliaro, M.J., Vitaux, P., Lafon, C., Lochon, I., Nehme, A., Bodo, M., Todisco, T., Pezzetti, F., Dottorini, M., Moggi, L. Valette, A., Canal, P., Bugat, R. & Jozan, S. (1997) & Becchetti, E. (1989) Ability of retinoic and ascorbic Multifactorial mechanism for the potentiation of cis- acid to interfere with the binding of benzo(a)pyrene platin (CDDP) cytotoxicity by all-trans-retinoic acid to DNA in explants from donors with bronchial can- (ATRA) in human ovarian carcinoma cell lines. Br. J. cer. Oncology, 46, 178-182 Cancer, 75, 333-340 Bollag, W. (1974) Therapeutic effects of an aromatic Camera, G. & Pregliasco, P. (1992) Ear malformation in retinoic acid analog on chemically induced skin papillo- baby born to mother using tretinoin cream. Lancet, mas and carcinomas of mice. Eur. J. Cancer, 10, 731-737 339,687-687 Boyle, JO., Langenfeld, J., Lonardo, F., Sekula, D., Reczek, Camoirano, A., Balansky, R.M., Bennicelli, C., Izzotti, A., P., Rusch, V., Dawson, M.I. & Dmitrovsky, E. (1999) D'Agostini, R & De Flora, S. (1994) Experimental data- Cydin Di proteolysis: Aretinoid chemoprevention sig- bases on inhibition of the bacterial mutagenicity of 4- nal in normal, immortalized, and transformed human nitroquinoline 1-oxide and cigarette smoke. Mutat. bronchial epithelial cells. J. Natl Cancer Inst., 91, Res., 317, 89-109 3 73-3 79 Castaigne, S., Chomienne, C., Daniel, M.T., Ballerini, P., Breitkreutz, D., Stark, H.J., Plein, P., Baur, M. & Fusenig, Berger, R., Fenaux, P. & Degos, L. (1990) All-trans N.E. (1993) Differential modulation of epidermal ker- retinoic acid as a differentiation therapy for acute atinization in immortalized (HaCaT) and tumorigenic promyelocytic leukemia. I. Clinical results. Blood, 76, human skin keratinocytes (HaCaT-ras) by retinoic 1704-1709 acid and extracellular Ca2*. Differentiation, 54, Chen, L.C., Sly, L. & De Luca, L.M. (1994) High dietary 201-217 retinoic acid prevents malignant conversion of skin Bseiso, A.w., Kantarjian, H. & Estey, E. (1997) papillomas induced by a two-stage carcinogenesis Myelodysplastic syndrome following successful ther- protocol in female SENCAR mice. Carcinogenesis, 15, apy of acute promyelocy-tic leukemia. Leukemia, 11, 2383-2386 168-169

134 All-trans-Retinoic acid

Choo, C.K., Rorke, E.A. & Eckert, R.L. (1995) Retinoid 13-cis-retinoic acid and all-trans-retinoyl- -glu- regulation of cell differentiation in a series of human curorilde in rat whole embryo culture. Biochem. papillomavirus type 16-immortalized human cervical Pharmacol., 43, 2289-2292 epithelial cell lines. Carcinogenesis, 16, 375-381 Creech Kraft, J. & Willhite, C.C. (1997) Retinoids in Christian, M.S., Mitala, Jj., Powers, W.J.J., McKenzie, B.E. abnormal and normal embryonic development. In: & Latriano, L. (1997) A developmental toxicity study Kacew, S. & Lambert, G.H., eds, Environmental of tretinoin emollient cream (Renova) applied topi- Toxicology and Pharmacology of Human Development. cally to New Zealand white rabbits. J. Am. Acad. Washington DC, Taylor & Francis, pp. 15-49 Dermatol., 36, S67-S76 Creech Kraft, J., Kochhar, D.M., Scott, W.J. & Nau, H. Clairmont, A., Tessmann, D. & Sies, H. (1996) Analysis of (1987) Low teratogenicity of 13-cis-retinoic acid connexin43 gene expression induced by retinoic acid (isotretinoin) in the mouse corresponds to low in F9 teratocarcinoma cells. FEBS Lett., 397, 22-24 embryo concentrations during organogenesis: Clewell, H.J., Andersen, M.E., Wills, RJ. & Latriano, L. Comparison to the all-trans-isomer. Toxicol. App!. (1997) A physiologically based pharmacokinetic Pharmacol., 87, 474-482 model for retinoic acid and its metabolites. J. Am. Creech Kraft, J., Lofberg, B., Chahoud, I., Bochert, G. & Acad. Dermatol., 36, S77-S85 Nau, H. (1989) Teratogenicity and placental transfer Collins, M.D., Tzimas, G., Hummier, H., Burgin, H. & of all-trans-, 13-cis-, 4-oxo-all-trans-, and 4-oxo-13-cis- Nau, H. (1994) Comparative teratology and transpia- retinoic acid after administration of a low oral dose cental pharmacokinetics of all-trans-retinoic acid, 13- during organogenesis in mice. Toxico!. App!. cis-retinoic acid, and retinyl palmitate following daily Pharmacol., 100, 162-176 administrations in rats. Toxico!. App!. Pharmacol., 127, Creech Kraft, J., Slikker, W., Bailey, JR., Roberts, L.G., 132-144 Fischer, B., Wittfoht, W. & Nau, H. (1991a) Plasma Collins, M.D., Tzimas, G., Burgin, H., Hummler, H. & pharmacokinetics and metabolism of 13-cis- and Nau, H. (1995) Single versus multiple dose adminis- all-trans-retinoic acid in the cynomolgus monkey and tration of all-trans-retinoic acid during organogenesis: the identification of 13-cis- and al1-trans-retinoyl-3- Differential metabolism and transplacental kinetics glucuronides. A comparison to one human case in rat and rabbit. Toxico!. Appl. Pharmacol., 130, 9-18 study with isotretinoin. Drug Metab. Dispos., 19, Conley, B.A., Egorin, MJ., Sridhara, R., Finley, R., 317-324 Hemady, R., Wu, S., Tait, N.S. & Van Echo, D.A. (1997) Creech Kraft, J., Eckhoff, C., Kochhar, D.M., Bochert, G., Phase I clinical trial of all-trans-retinoic acid with cor- Chahoud, I. & Nau, H. (1991b) Isotretinoin (13-cis- relation of its pharmacokinetics and pharmacody- retinoic acid) metabolism, cis-trans isomerization, namics. Cancer Chemother. Pharmacol., 39, 291-299 glucuronidation, and transfer to the mouse embryo: Connor, MJ., Lowe, N.J., Breeding, J.H. & Chalet, M. Consequences for teratogenicity. Teratog. Carcinog. (1983) Inhibition of ultraviolet-B skin carcinogenesis Mutag., 11, 21-30 by all-trans-retinoic acid regimens that inhibit Creek, K.E., Geslani, G., Batova, A. & Pirisi, L. (1995) ornithine decarboxylase induction. Cancer Res., 43, Progressive loss of sensitivity to growth control by 171-174 retinoic acid and transforming growth factor-beta at Cortes, J., Kantarjian, H., O'Brien, S., Beran, M., Estey, E., late stages of human papillomavirus type 16-initiated Keating, M. & Talpaz, M. (1997) A pilot study of all- transformation of human keratinocytes. Adv. Exp. trans-retinoic acid in patients with Philadelphia chro- Med. Bio!., 375, 117-135 mosome-positive chronic myelogenous leukemia. Cull, G.M., Elkelboom, J.W. & Cannell, P.K. (1997) Leukemia, 11, 929-932 Exacerbation of coagulopathy with concurrent bone Cozzi, R., Bona, R., Polani, S. & De Salvia, R. (1990) marrow necrosis, hepatic and renal dysfunction sec- Retinoids as modulators of metabolism: Their ondary to all-trans-retinoic acid therapy for acute inhibitory effect on cyclophosphamide and 7,12- promyelocytic leukemia. Hematol. Oncol., 15, 13-17 dimethylbenz[a]anthracene induced sister chromatid Daoud, A.H. & Griffin, A.C. (1978) Effects of selenium exchanges in a metabolically competent cell line. and retinoic acid on the metabolism of N-acetyl- Mutagenesis, 5, 397-401 aminofluorene and N-hydroxyacetylaminofluorene. Creech Kraft, J. & Juchau, M.R. (1992) Conceptual bio- Cancer Lett., 5, 231-237 transformation of 4-oxo-all-trans-retinoic acid, 4-oxo-

135 ARC Handbooks of Cancer Prevention

Dawson, M.I. & Hobbs, P.D. (1994) The synthetic chem- in vivo compared to concentrations required to stimu- istry of retinoids. In: Sporn, M.B., Roberts, A.B. & late retinoic acid receptor-mediated transcription in Goodman, D.S., eds., The Retinoids: Biology, Chemistiy, vitro. J. Clin. Invest., 90, 1269-1274 and Medicine, 2nd Ed. New York, Raven Press, pp. Durston, AJ., Timmermans, J.P., Hage, W.J., Hendriks, 5-178 H.F., de Vries, NJ., Heideveld, M. & Nieuwkoop, P.D. Dawson, M.I., Chao, W.R. & Helmes, C.T. (1987) (1989) Retinoic acid causes an anteroposterior trans- Inhibition by retinoids of anthralin-induced mouse formation in the developing central nervous system. epidermal ornithine decarboxylase activity and Nature, 340, 140-144 anthralin-promoted skin tumor formation. Cancer Eckhoff, C. & Nau, H. (1990) Identification and quantita- Res., 47, 6210-6215 tion of all-trans- and 13-cis-retinoic acid and 13-cis-4- De Benedetti, F., Falk, L., Ruscetti, EW, Colburn, N.H., oxo-retinoic acid in human plasma. J. Lipid Res., 31, Faltynek, C.R. & Oppenheim, 1.1. (1991) Synergistic 1445-1454 inhibition of phorbol ester-induced transformation of Eckhoff, C., Collins, M.D. & Nau, H. (1991) Human JB6 cells by transforming growth factor-li and retinoic plasma all-trans-, 13-cis- and 13-cis-4-oxoretinoic acid acid. Cancer Res., 51, 1158-1164 profiles during subchronic vitamin A supplementa- De Botton, S., Dombret, H., Sanz, M., San Miguel, J., tion: Comparison to retinol and retinyl ester plasma Caillot, D., Zittoun, R., Gardembas, M., Stamatoulas, levels. J. Nutr., 121, 1016-1025 A., Condé, E., Guerci, A., Gardin, C., Geiser, K., Cony Edwards, L. & Jaffe, P. (1990) The effect of topical Makhoul, D., Reman, O., de la Sema, J., Lefrere, E, tretinoin on dysplastic nevi. A preliminary trial. Arch. Chomienne, C., Chastang, C., Degos, L. & Fenaux, P. Dermatol., 126, 494-499 (1998) Incidence, clinical features, and outcome of Englert, G. (1975) A 13C-NMR. Study of cis-trans isomeric all-trans-retinoic acid syndrome in 413 cases of newly vitamins A, carotenoids and related compounds. Helv. diagnosed acute promyelocytic leukemia. The Chim. Acta, 58, 2367-2390 European APL Group. Blood, 92, 2712-2718 Evans, G., Grimwade, D., Prentice, H.G. & Simpson, N. De Flora, S., Bennicelli, C., Rovida, A., Scatolini, L. & (1997) Central nervous system relapse in acute Camoirano, A. (1994) Inhibition of the 'spontaneous' promyelocytic leukaemia in patients treated with all- mutagenicity in Salmonella Lyphimunum TA102 and trans-retinoic acid. Br. J. Haematol., 98, 437-439 TA104. Mutat. Res., 307, 157-167 Fenaux, P. & De Botton, S. (1998) Retinoic acid syn- Degitz, SJ., Francis, B.M. & Foley, G.L. (1998) drome. Recognition, prevention and management. Mesenchymal changes associated with retinoic acid Drug Saf., 18, 273-279 induced cleft palate in CD-1 mice. J. Cranio fac. Genet. Fiorella, RD., Giguère, V. & Napoli, J.L. (1993) Expression Dey. Biol., 18, 88-99 of cellular retinoic acid-binding protein (type II) in Dencker, L., d'Argy, R., Danielsson, B.R., Ghantous, H. & Escherichia cou. Characterization and comparison to Sperber, G.O. (1987) Saturable accumulation of cellular retinoic acid-binding protein (type I). J. Biol. retinoic acid in neural and neural crest derived cells in Chem., 268, 21545-21552 early embryonic development. Dey. Pharmacol. Ther., Firozi, P.F., Aboobaker, V.S. & Bhattacharya, R.K. (1987) 10,212-223 Action of vitamin A on DNA adduct formation by Dencker, L., Annerwall, E., Busch, C. & Eriksson, U. aflatoxin B1 in a microsome catalyzed reaction. Cancer (1990) Localization of specific retinoid-binding sites Lett., 34, 213-220 and expression of cellular retinoic-acid-binding pro- Fischer, S.M., Klein-Szanto, AJ., Adams, L.M. & Slaga, T.J. tern (CRABP) in the early mouse embryo. (1985) The first stage and complete promoting activ- Development, 110, 343-352 ity of retinoic acid but not the analog RO-10-9359. Denning, MY & Verma, A.K. (1994) The mechanism of Carcinogenesis, 6, 575-578 the inhibition of squamous differentiation of rat tra- Fitzgerald, DJ., Barrett, J.C. & Nettesheim, P. (1986) cheal 2C5 cells by retinoic acid. Carcinogenesis, 15, Changing responsiveness to all-trans-retinoic acid of 503-507 rat tracheal epithelial cells at different stages of neo- Duell, E.A., Aström, A., Griffiths, C.E., Chambon, P. & plastic transformation. Carcinogenesis, 7, 1715-1721 Voorhees, Jj. (1992) Human skin levels of retinoic Forbes, P.D., Urbach, F. & Davies, R.E. (1979) Enhance- acid and cytochrome P-450-derived 4-hydroxy- ment of experimental photocarcinogenesis by topical retinoic acid after topical application of retinoic acid retinoic acid. Cancer Left., 7, 85-90

136 All-trans-Retinoic acid

Frickel, F. (1984) Chemistry and physical properties of Halpern, A.C., Schuchter, L.M., Elder, D.E., Guerry, D., retinoids. In: Sporn, M.B., Roberts, A.B. & Goodman, Elenitsas, R., Trock, B. & Matozzo, I. (1994) Effects of D.S., eds, The Retinoids. Orlando FL, Academic Press, topical tretinoiii on dysplastic nevi. J. Clin. Oncol., 12, PP. 7-145 1028-1035 Frolik, C.A. & Olson, J.A. (1984) Extraction, separation, Han, J.S. (1992) Effects of various chemical compounds and chemical analysis of retinoids. In: Sporn M.B., on spontaneous and hydrogen peroxide-induced Roberts A.B. & Goodman, D.S., eds, The Retinoids. reversion in strain TA104 of Salmonella typhimurium. New York, Academic Press, pp. 181-233 Mutat. Res., 266, 77-84 Fullerton, A. & Serup, J. (1997) Characterization of irri- Harrison, E, Chipping, P. & Fothergill, G.A. (1994) tant patch test reactions to topical D vitamins and all- Successful use of all-trans-retinoic acid in acute trans-retinoic acid in comparison with sodium lauryl promyelocytic leukaemia presenting during the second sulphate. Evaluation by clinical scoring and multi- trimester of pregnancy. Br. J. Haematol., 86, 681-682 parametric non-invasive measuring techniques. Br. J. Hatake, K., Uwai, M., Ohtsuki, T., Tomizuka, H., Izumi, Dermatol., 137, 234-240 T., Yoshida, M. & Miura, Y. (1997) Rare but important Fun, H.C., Barua, A.B. & Olson, J.A. (1992) Retinoids and adverse effects of all-trans-retinoic acid in acute carotenoids. In: De Leenheer A.P., Lambert W.E. & promyelocytic leukemia and their management. mt. Nelis, H.J., Eds. Modem Chromatographic Analysis of J. Hematol., 66, 13-19 Vitamins, 2nd Ed. New York, Marcel Dekker Inc., pp. Helms, J.A., Kim, C.H., Hu, D., Minkoff, R., Thaller, C. & 1-71 Eichele, G. (1997) Sonic hedgehog participates in cran- Fun, H.C., Barua, A.B. & Olson, J.A. (1994) Analytical iofacial morphogenesis and is down-regulated by ter- methods. In: Sporn M.B., Roberts, A.B. & Goodman, atogenic doses of retinoic acid. Dey. Biol., 187, 25-35 D.S., eds, The Retinoids: Biology, Chemistry, and Hendrickx, A.G. & Hummler, H. (1992) Teratogenicity of Medicine, 2' ed. New York, Raven Press, pp. 179-209 all-trans-retinoic acid during early embryonic devel- Geelen, J.A. (19 79) Hypervitaminosis A induced teratoge- opment in the cynomolgus monkey (Macaca fascicu- nesis. CRC Crit. Rev, Toxico!., 6, 351-375 laris). Teratology, 45, 65-74 Graham, V., Surwit, E.S., Weiner, S. & Meyskens, EL., Jr Hennings, H., Robinson, V.A., Michael, D.M., Pettit, (1986) Phase II trial of 3-all-trans-retinoic acid for cer- G.R., Jung, R. & Yuspa, S.H. (1990) Development of vical intraepithelial neoplasia delivered via a collagen an in vitro analogue of initiated mouse epidermis to sponge and cervical cap. West.J. Med., 145, 192-195 study tumor promoters and antipromoters. Cancer Grandis, J.R., Zeng, Q. & Tweardy, DJ. (1996) Retinoic Res., 50, 4794-4800 acid normalizes the increased gene transcription rate Hill, EM., Bader, T., Nettesheim, P. & Eling, T.E. (1996) of TGF-(x and EGFR in head and neck cancer cell lines. Retinoid-induced differentiation regulates prosta- Nat. Med., 2, 237-240 glandin H synthase and cPLA2 expression in tracheal Gudas, L.J., Sporn, M.B. & Roberts, A.B. (1994) Cellular epithelium. Am. J. Physiol., 270, L854-L862 biology and biochemistry of the retinoids. In: Sporn Holder, N. & Hill, J. (1991) Retinoic acid modifies devel- M.B., Roberts, A.B. & Goodman, D.S., eds, The opment of the midbrain-hindbrain border and affects Retinoids. New York, Raven Press, pp. 443-520 cranial ganglion formation in zebrafish embryos. Gunning, D.B., Barua, A.B. & Olson, J.A. (1993) Development, 113,1159-1170 Comparative teratogenicity and metabolism of all- Hong, W.K. & Itri, L.M. (1994) Retinoids and human can- trans-retinoic acid, all-trans-retinoyl 3-glucose, and cer. In: Sporn, M.B., Roberts, A.B. & Goodman, D.S., all-trans-retinoyl -g1ucuronide in pregnant Sprague- eds, The Retinoids: Biology, Chemistry, and Medicine, Dawley rats. Teratology, 47, 29-36 2nd Ed. New York, Raven Press, pp. 597-630 Guo, H., Acevedo, P., Parsa, ED. & Bertram, J.S. (1992) Hossain, M.Z. & Bertram, J.S. (1994) Retinoids suppress Gap-junctional protein connexin 43 is expressed in der- proliferation, induce cell spreading, and up-regulate mis and epidermis of human skin: Differential modula- connexin43 expression only in postconfluent 1OT1/2 tion by retinoids. J. Invest. Dennatol., 99, 460-467 cells: Implications for the role of gap junctional com- Guzman, K., Bader, T. & Nettesheim, P. (1996) Regulation munication. Cell Growth Differ., 5, 1253-1261 of MUC5 and MUC1 gene expression: Correlation Hossain, M.Z., Wilkens, L.R., Mehta, P.P., Loewenstein, with airway mucous differentiation. Am. J. Physiol., W. & Bertram, J.S. (1989) Enhancement of gap junc- 270,L846-L853 tional communication by retinoids correlates with

137 IARC Handbooks of Cancer Prevention

their ability to inhibit neoplastic transformation. Kaartinen, L., Nettesheim, P., Adler, K.B. & Randell, S.H. Carcinogenesis, 10, 1743-1748 (1993) Rat tracheal epithelial cell differentiation in Howell, SR., Shirley, M.A. & Ulm, E.H. (1998) Effects of vitro. In Vitro Cell Dey. Biol. Anim., 29A, 481-492 retinoid treatment of rats on hepatic microsomal Kahn, J.R., Wells, M.J. & Hill, D.L. (1984) Effects of phe- metabolism and cytochromes P450. Correlation nobarbital, 3-methylcholanthrene, and retinoid pre- between retinoic acid receptor/retinoid X receptor treatment on disposition of orally administered selectivity and effects on metabolic enzymes. Drug retinoids in mice. Drug Metab. Dispos., 12, 63-67 Metab. Dispos., 26, 234-239 Kalter, H. & Warkany, J. (1961) Experimental production Huang, C., Ma, WY., Dawson, M.I., Rincon, M., Flavell, of congenital anomalies in strains of inbred mice by R.A. & Dong, Z. (1997) Blocking activator protein-i maternal treatment with hypervitaminosis A. Am. J. activity, but not activating retinoic acid response ele- Pathol., 38, 1-15 ment, is required for the antitumor promotion effect of Kamm, Jj. (1982) Toxicology, carcinogenicity, and ter- retinoic acid. Proc. Nat! Acad. Sci. USA, 94, 5826-5830 atogenicity of some orally administered retinoids. J. IARC (1998) IARC Handbooks of Cancer Prevention, Vol. 3, Am. Acad. Dermatol., 6, 652-659 Vitamin A, Lyon, International Agency for Research Kamm, J.J., Ashenfelter, K.O. & Ehmann, C.W. (1984) on Cancer, pp. 167-170 Preclinical and clinical toxicology of selected Ikemi, N., Kawata, M. & Yasuda, M. (1995) All-trans- retinoids. In: Sporn, MB., Roberts, A.B. & Goodman, retinoic acid-induced variant patterns of palatal rugae D.S., eds, The Retinoids. Orlando, FL, Academic Press, in Crj:SD rat fetuses and their potential as indicators Inc., pp. 287-326 for teratogenicity. Reprod. Toxico!., 9, 369-377 Kentos, A., Le Moine, E, Crenier, L., Capel, P., Meyer, S., Jensen, BK., McGann, L.A., Kachevsky, V. & Franz, T.J. Muus, P., Mandelli, E & Feremans, W. (1997) All-trans- (1991) The negligible systemic availability of retinoic acid induced thrombocytosis in a patient retinoids with multiple and excessive topical applica- with acute promyelocytic leukaemia. Br. J. Haematol., tion of isotretinoin 0.05% gel (Isotrex) in patients with 97,685-685 acne vulgaris. J. Am. Acad. Dermatol., 24, 425-428 Khan, M.A., Jenkins, G.R., Tolleson, W.H., Creek, K.E. & Jetten, A.M. & Shirley, J.E. (1985) Retinoids antagonize Pirisi, L. (1993) Retinoic acid inhibition of human the induction of ornithine decarboxylase activity by papillomavirus type 16-mediated transformation of phorbol esters and phospholipase C in rat tracheal human keratinocytes. Cancer Res., 53, 905-909 epithelial cells. J. Cell Physiol., 123, 386-394 Kim, Y.H., Dohi, D.E, Han, G.R., Zou, C.P., Oridate, N., Jick, S.S., Terris, B.Z. & Jick, H. (1993) First trimester topi- Walsh, G.L., Nesbitt, J.C., Xu, X.C., Hong, W.K., cal tretinoin and congenital disorders. Lancet, 341, Lotan, R. & Kurie, J.M. (1995) Retinoid refractoriness 1181-1182 occurs during lung carcinogenesis despite functional Johnson, E.M. (1997) A risk assessment of topical retinoid receptors. Cancer Res., 55, 5603-5610 tretinoin as a potential human developmental toxin Kistler, A. (1981) Teratogenesis of retinoic acid in rats: based on animal and comparative human data. J. Am. Susceptible stages and suppression of retinoic acid- Acad. Dermatol., 36, S86-S90 induced limb malformations by cycloheximide. Joiakim, A.P. & Chopra, D.P. (1993) Retinoic acid and cal- Teratology, 23, 25-31 cium regulation of p53, transforming growth factor- Klein-Szanto, A.J., lizasa, T., Momilci, S., Garcia, P., I, 01, and transforming growth factor-a gene expression Caamano, J., Metcalf, R., Welsh, J. & Harris, C.C. and growth in adenovirus 12-SV40-transformed (1992) A tobacco-specific N-nitrosamine or cigarette human tracheal gland epithelial cells. Am. J. Respir. smoke condensate causes neoplastic transformation Cell. Mol. Bio!., 8, 408-416 of xenotransplanted human bronchial epithelial Juhi, H.J., Schurer, C.C., Bartram, C.R., Kohl, EV., cells. Proc. NatI Acad. Sci. USA, 89, 6693-669 7 Melderis, H., von-Wichert, P. & RUdiger, H.W. (1978) Kiigman, A.M. & Thorne, E.G. (1991) Topical therapy of Retinoids induce sister-chromatid exchanges in actinic keratoses with tretinoin. In: Marks, R., ed., human diploid fibroblasts. Mutat. Res., 58, 317-320 Retinoids in Cutaneous Malignancy. Oxford Blackwell Jurima-Romet, M., Neigh, S. & Casley, W.L. (1997) Scientific, pp. 66-73 Induction of cytochrome P450 3A by retinoids in rat Kochhar, D.M., Jiang, H., Penner, J.D. & Heyman, R.A. hepatocyte culture. Hum. Exp. Toxicol., 16, 198-203 (1995) Placental transfer and developmental effects of 9-ris retinoic acid in mice. Teratology, 51, 257-265

138 All-trans-Retinoic acid

Koo, J.S., Yoon, J.H., Gray, T., Norford, D., Jetten, A.M. & Lin, C.P., Huang, MJ., Liu, H.J., Chang, I.Y. & Tsai, C.H. Nettesheim, P. (1999a) Restoration of the mucous (1996) Successful treatment of acute promyelocytic phenotype by retinoic acid in retinoid-deficient leukemia in a pregnant Jehovah's Witness with all- human bronchial cell cultures: Changes in mucin trans-retinoic acid, rhG-CSF, and erythropoietin. Am. gene expression. Am. J. Respir. Cell. Mol. Bio!., 20, J. Hernatol., 51, 251-252 43-52 Lingen, MW., Polverini, P.J. & Bouck, N.P. (1996) Koo, J.S., Jetten, A.M., Belloni, P., Yoon, J.H., Kim, Y.D. & Retinoic acid induces cells cultured from oral squa- Nettesheim, P. (1999b) Role of retinoid receptors in mous cell carcinomas to become anti-angiogenic. Am. the regulation of mucin gene expression by retinoic J. Pathol., 149, 247-258 acid in human tracheobronchial epithelial cells. Lipovsky, M.M., Biesma, D.H., Christiaens, G.C. & Biochem. J., 338, 351-357 Petersen, E.J. (1996) Successful treatment of acute Langenfeld, J., Lonardo, E, Kiyokawa, H., Passalaris, T., promyelocytic leukaemia with all-trans-retinoic-acid Ahn, MJ., Rusch, V. & Dmitrovsky, E. (1996) during late pregnancy. Br. J. Haematol., 94, 699-701 Inhibited transformation of immortalized human Lipson, A.H., Collins, F. & Webster, W.S. (1993) Multiple bronchial epithelial cells by retinoic acid is linked to congenital defects associated with maternal use of cyclin E down-regulation. Oncogene, 13, 1983-1990 topical tretinoin. Lancet, 341, 1352-1353 Langenfeld, J., Kiyokawa, H., Sekula, D., Boyle, J. & Liu, M., lavarone, A. & Freedman, L.P. (1996) Dmitrovsky, E. (1997) Posttranslational regulation of Transcriptional activation of the human p21 1IC'1 cyclin Dl by retinoic acid: A chemoprevention mech- gene by retinoic acid receptor. Correlation with anism. Proc. Nat! Acad. Sci. USA, 94, 12070-12074 retinoid induction of U937 cell differentiation. J. Biol. Latriano, L., Tzimas, G., Wong, F. & Wills, R.J. (1997) The Chem., 271, 31723-31728 percutaneous absorption of topically applied Lotan, R. (1993) Retinoids and squamous cell differentia- tretinoin and its effect on endogenous concentrations tion. In: Hong, W.K. & Lotan, R., eds, Retinoids in of tretinoin and its metabolites after single doses or Oncology. New York, Marcel Dekker Inc., pp. 43-72 long-term use. J. Am. Acad. Dermatol., 36, S37-S46 Lotan, R. (1995) Cellular biology of the retinoids. In: Lee, H.Y., Dawson, M.I., Claret, EX., Chen, J.D., Walsh, Degos, L. & Parkinson, D.R., eds, Retinoids in Oncology. G.L. Hong, W.K. & Kurie, J.M. (1997) Evidence of a Berlin, Springer Verlag, pp. 27-42 retinoid signaling alteration involving the activator Lotan, R., Amos, B., Watanabe, H. & Raz, A. (1992) protein 1 complex in tumorigenic human bronchial Suppression of melanoma cell motility factor receptor epithelial cells and non-small cell lung cancer cells. expression by retinoic acid. Cancer Res., 52, Cell Growth Differ., 8, 283-291 4878-4884 Lemez, P. (1995) Hypercalcaemia caused by all-trans- Maeda, M., Tyugu, H., Okubo, T., Yamamoto, M., retinoic acid (ATRA) treatment in a case of acute Nakamura, K. & Dan, K. (1997) A neonate born to a promyelocytic leukaemia was manageable after mother with acute promyelocytic leukemia treated by decreasing the ATRA dose to 27 mg/m2/day. Eur. J. all-trans-retinoic acid. Jpn. J. Clin. Hematol., 38, 770-775 Haematol., 55, 275-276 Mao, Y., Gurr, J.A. & Hickok, N.J. (1993) Retinoic acid Leyden, J.J. (1998) Topical treatment of acne vulgaris: regulates ornithine decarboxylase gene expression at Retinoids and cutaneous irritation. J. Am. Acad. the transcriptional level. Biochem. J., 295, 641-644 Dermatol., 38, S1-S4 Marnett, L.J. & Ji, C. (1994) Modulation of oxidant for- Li, X.Y., Aström, A., Duell, E.A., Qin, L., Griffiths, C.E. & mation in mouse skin in vivo by tumor-promoting Voorhees, J.J. (1995) Retinoic acid antagonizes basal phorbol esters. Cancer Res., 54, 1886s-1889s as well as coal tar and glucocorticoid-induced Maron, D.M. & Ames, B.N. (1983) Revised methods for cytochrome P4501A1 expression in human skin. the Salmonella mutagenicity test. Mutat. Res., 113, Carcinogenesis, 16, 519-524 173-215 Li, J.J., Dong, Z., Dawson, M.I. & Colburn, N.H. (1996) Massaro, G.D. & Massaro, D. (1997) Retinoic acid treat- Inhibition of tumor promoter-induced transforma- ment abrogates elastase-induced pulmonary emphy- tion by retinoids that transrepress AP-1 without trans- sema in rats. Nat. Med., 3, 675-677 activating retinoic acid response element. Cancer Res., McCormick, D.L., Bagg, Bj. & Hultin, T.A. (1987) 56,483-489 Comparative activity of dietary or topical exposure to

139 ARC Handbooks of Cancer Prevention

three retinoids in the promotion of skin tumor induc- Morton, J., Taylor, K., Wright, S., Pitcher, L., Wilson, E., tion in mice. Cancer Res., 47, 5989-5993 Tudehope, D., Savage, J., Williams, B., Taylor, D., McCormick, D.L., Hollister, J.L., Bagg, BJ. & Long, R.E. Wiley, J., Tsoris, D. & O'Donnell, A. (1995) Successful (1990) Enhancement of murine hepatocarcinogenesis maternal and fetal outcome following the use of by all-trans-retinoic acid and two synthetic reti- ATRA for the induction of APML late in the first namides. Carcinogenesis, 11, 1605-1609 trimester. Blood, 86 (Suppl. 1), 772a-772a McPhillips, D.M., Kahn, J.R. & Hill, D.L. (1987) The phar- Muindi, J.R., Frankel, SR., Huselton, C., DeGrazia, E, macokinetics of all-trans-retinoic acid and N-(2- Garland, WA., Young, C.W. & Warrell, R.P, Jr (1992) hydroxyethyl)retinamide in mice as determined with Clinical pharmacology of oral all-trans-retinoic acid a sensitive and convenient procedure. Solid-phase in patients with acute promyelocytic leukemia. extraction and reverse-phase high performance liquid Cancer Res., 52, 2138-2142 chromatography. Drug Metab. Dispos., 15, 207-211 Mulder, G.B., Manley, N. & Maggio-Price, L. (1998) Mehta, PP., Bertram, J.S. & Loewenstein, W.R. (1989) The Retinoic acid-induced thymic abnormalities in the actions of retinoids on cellular growth correlate with mouse are associated with altered pharyngeal their actions on gap junctional communication. J. morphology, thymocyte maturation defects, and Cell. Biol., 108, 1053-1065 altered expression of Hoxa3 and Paxi. Teratology, 58, Melino, G., Draoui, M., Bellincampi, L., Bernassola, R, 263-275 Bernardini, S., Piacentini, M., Reichert, U. & Cohen, P. Nagy, L., Thomazy, V.A., Shipley, G.L., Fesus, L., Lamph, (1997) Retinoic acid receptors alpha and gamma W., Heyman, RA., Chandraratna, R.A. & Davies, P.J. mediate the induction of 'tissue' transglutaminase (1995) Activation of retinoid X receptors induces activity and apoptosis in human neuroblastoma cells. apoptosis in HL-60 cell lines. Mol. Cell. Bio!., 15, Exp. Cell Res., 235, 55-61 3540-3551 Merrick, D.T., Gown, A.M., Halbert, C.L., Blanton, R.A. & Napoli, J.L. (1994) Retinoic acid homeostatis. Prospective McDougall, J.K. (1993) Human papillomavirus- roles of j-carotene, retinol, CRBP and CRABP. In: immortalized keratinocytes are resistant to the effects Blomhoff, R., ed., Vitamin A in Health and Disease. of retinoic acid on terminal differentiation. Cell New York, Marcel Dekker, pp. 135-188 Growth Differ., 4, 831-840 Nau, H. (1993) Embryotoxicity and teratogenicity of Mestre, JR., Subbaramaiah, K., Sacks, P.G., Schantz, S.P., topical retinoic acid. Skin Pharmaco!., 6 (Suppl. 1), 3544 Tanabe, T., Inoue, H. & Dannenberg, A.J. (1997) Nau, H., Elmazar, M.M., Ruhl, R., Thiel, R. & Sass, 1.0. Retinoids suppress phorbol ester-mediated induction (1996) All-trans-retinoyl-jl-glucuronide is a potent ter- of cyclooxygenase-2. Cancer Res., 57, 1081-1085 atogen in the mouse because of extensive metabolism Meyskens, EL., Jr, Graham, V., Chvapil, M., Dorr, R.T., to all-trans-retinoic acid. Teratology, 54, 150-156 Alberts, D.S. & Surwit, E.A. (1983) A phase I trial of P- Nettesheim, P., Fitzgerald, D.J., Kitamura, H., Walker, all-trans-retinoic acid delivered via a collagen sponge CL., Gilmer, T.M., Barrett, J.C. & Gray, T.E. (1987) In and a cervical cap for mild or moderate intraepithelial vitro analysis of multistage carcinogenesis. Environ. cervical neoplasia. J. Nat! Cancer Inst., 71, 921-925 Health Perspect., 75, 71-79 Meyskens, FL., Jr, Surwit, E., Moon, TE., Childers, J.M., Newton, D.L., Henderson, W.R. & Sporn, M.B. (1980) Davis, JR., Don, R.T., Johnson, C.S. & Alberts, D.S. Structure-activity relationships of retinoids in hamster (1994) Enhancement of regression of cervical ultra- tracheal organ culture. Cancer Res., 40, 3413-3425 epithelial neoplasia II (moderate dysplasia) with topi- Nicholson, R.C., Mader, S., Nagpal, S., Leid, M., Rochette- cally applied all-trans-retinoic acid: A randomized Egly, C. & Chambon, P. (1990) Negative regulation of trial. J. Natl Cancer Inst., 86, 539-543 the rat stromelysin gene promoter by retinoic acid is Moghal, N. & Neel, B.G. (1998) Integration of growth mediated by an APi binding site. EMBO J., 9,4443-4454 factor, extracellular matrix, and retinoid signals during Nicolls, MR., Terada, L.S., Tuder, R.M., Prindiville, S.A. & bronchial epithelial cell differentiation. Mol. Cell. Schwarz, M.I. (1998) Diffuse alveolar hemorrhage with Bio!., 18, 6666-6678 underlying pulmonary capillaritis in the retinoic acid Monczak, Y., Tmdel, M., Lamph, W.W. & Miller, W.H.J. syndrome. Am. J. Respir. Crit. Care Med., 158, 1302-1305 (1997) Induction of apoptosis without differentiation Niederreither, K., Ward, S.J., Dolle, P. & Chambon, P. by retinoic acid in PLB-985 cells requires the (1996) Morphological and molecular characterization activation of both BAR and RXR. Blood, 90, of retinoic acid-induced limb duplications in mice. 3345-3355 Dey. Biol., 176, 185-198

140 All-trans-Retinoic acid

Nolen, G.A. (1986) The effects of prenatal retinoic acid Rasco, J.F. & Hood, R.D. (1995a) Maternal restraint stress- on the viability and behavior of the offspring. enhanced teratogenicity of all-trans-retinoic acid in Neurobehav. Toxicol. Teratol., 8, 643-654 CD-1 mice. Teratology, 51, 57-62 Okai, Y., Higashi-Okai, K., Nakamura, S., Yano, Y. & Rasco, J.F. & Hood, R.D. (1995b) Enhancement of the Otani, S. (1996) Suppressive effects of retinoids, caro- teratogenicity of all-trans-retinoic acid by maternal tenoids and antioxidant vitamins on heterocyclic restraint stress in mice as a function of treatment tim- amine-induced umu C gene expression in Salmonella ing. Teratology, 51, 63-70 typhimurium (TA 1535/pSK 1002). Mutat. Res., 368, Reddel, R.R., Ke, Y., Gerwin, BI., McMenamin, MG., 133-140 Lechner, J.F., Su, R.T., Brash, D.E., Park, J.B., Rhim, J.S. Olsen, E.A., Katz, H.I., Levine, N., Nigra, T.P., Pochi, P.E., & Harris, C.C. (1988) Transformation of human Savin, R.C., Shupack, J., Weinstein, G.D., Lufrano, L. bronchial epithelial cells by infection with SV40 or & Perry, B.H. (1997) Tretinoin emollient cream for pho- adenovirus-12 SV40 hybrid virus, or transfection via todamaged skin: Results of 48-week, multicenter, dou- strontium phosphate coprecipitation with a plasmid ble-blind studies. J. Am. Acad. Dermatol., 37, 217-226 containing SV40 early region genes. Cancer Res., 48, Patel, I.H., Khoo, K.C. & Colburn, W.A. (1982) 1904-1909 Pharmacokinetics of tretinoin and its in vivo isomeric Rigas, J.R., Miller, V.A., Zhang, Z.E, Klimstra, D.S., Tong, conversion to isotretinoin in the dog. Drug MetaL'. W.P., Kris, M.G. & Warrell, R.P. (1996) Metabolic phe- Dispos., 10, 387-390 notypes of retinoic acid and the risk of lung cancer. Patel, R.K., Trivedi, A.H., Jaju, Rj., Kukreti, M.S., Cancer Res., 56, 2692-2696 Bhatavdekar, J.M., Shah, P.M. & Patel, D.D. (1998) Rogers, M., Berestecky, J.M., Hossain, M.Z., Guo, H.M., Protection from pan masala induced genomic dam- Kadle, R., Nicholson, B.J. & Bertram, J.S. (1990) age by beta-carotene and retinoic acid—An in vitro Retinoid-enhanced gap junctional communication is experience. Neoplasma, 45, 169-175 achieved by increased levels of connexin 43 mRNA Paydas, S., Sahin, B., Zorludemir, S. & Bazar, B. (1998) All and protein. Mol. Carcinog., 3, 335-343 trans-retinoic acid as the possible cause of necrotizing Rook, A.H., Jaworsky, C., Nguyen, T., Grossman, R.A., vasculitis. Leuk. Res., 22, 655-657 Wolfe, J.T., Witmer, W.K. & Kligman, A.M. (1995) Peck, G.L. & DiGiovanna, J.J. (1994) Synthetic retinoids Beneficial effect of low-dose systemic retinoid in com- in dermatology. In: Spom, M.B., Roberts, A.B. & bination with topical tretinoin for the treatment and Goodman, D.S., eds, The Retinoids: Biology, Chemistry, prophylaxis of premalignant and malignant skin and Medicine, 2nd Ed. New York, Raven Press, pp. lesions in renal transplant recipients. Transplantation, 631-658 59,714-719 Pirisi, L., Batova, A., Jenkins, G.R., Hodam, J.R. & Creek, Rosa, F.W. (1992) Retinoid embryopathy in humans. In: K.E. (1992) Increased sensitivity of human Koren, G., ed., Retinoids in Clinical Practice. The keratinocytes immortalized by human papillo- Risk-BenefitRatlo. New York, Marcel Dekker, pp. 77-109 mavirus type 16 DNA to growth control by retinoids. Russo, D., Regazzi, M., Sacchi, S., Visani, G., Lazzarino, Cancer Res., 52, 187-193 M., Avvisati, G., Pelicci, P.G., Dastoli, G., Grandi, C., Plewig, G., Schill, W.B. & Hofmann, C. (1979) Oral treat- lacona, I., Candoni, A., Grattoni, R., Galieni, P., ment with tretinoin: Andrological, trichological, oph- Rupoli, S., Liberati, A.M. & Maiolo, A.T. (1998) All- thalmological findings and effects on acne. Arch. trans-retinoic acid (ATRA) in patients with chronic Dermatol. Res., 265, 37-47 myeloid leukemia in the chronic phase. Leukemia, Pogliani, EM., Rossini, F., Casaroli, I., Maffe, P. & 12,449-454 Corneo, G. (1997) Thrombotic complications in acute Rutledge, J.C., Shourbaji, A.G., Hughes, L.A., Polifka, J.E., promyelocytic leukemia during all-trans-retinoic acid Cruz, Y.P., Bishop, J.B. & Generoso, W.M. (1994) Limb therapy. Acta Haematol., 97, 228-230 and lower-body duplications induced by retinoic acid Qin, S. & Huang, C.C. (1985) Effect of retinoids on car- in mice. Proc. Nat! Acad. Sci. USA, 91, 5436-5440 cinogen-induced mutagenesis in Salmonella tester Sano, F., Tsuji, K., Kunika, N., Takeuchi, T., Oyama, K., strains. Mutat. Res., 142, 115-120 Hasegawa, S., Koike, M., Takahashi, M. & Ishida, M. Raina, V. & Gurtoo, H.L. (1985) Effects of vitamins A, C, (1998) Pseudotumor cerebri in a patient with acute and E on aflatoxin Bi-induced mutagenesis in promyelocytic leukemia during treatment with all- Salmonella typhimurium TA-98 and TA-100. Teratog. trans-retinoic acid. Intern. Med., 37, 546-549 Carcinog. Mutag., 5, 29-40 141 ARC Handbooks of Cancer Prevention

Sarma, D., Yang, X., Jin, G., Shindoh, M., Pater, M.M. & exchange (SCE) and mitomycin-C-induced SCE in Pater, A. (1996) Resistance to retinoic acid and altered cultured Chinese hamster cells. Mutat. Res., 90, cytokeratin expression of human papillomavirus type 175-182 16-immortalized endocervical cells after tumorigene- Sizemore, N. & Rorke, E.A. (1993) Human papillomavirus sis. mt. J. Cancer, 65, 345-350 16 immortalization of normal human ectocervical Schifie, R., Rangarajari, P., Yang, N., Kleiwer, S., Ransone, epithelial cells alters retinoic acid regulation of cell L.J., Bolado, J., Verma, I.M. & Evans, R.M. (1991) growth and epidermal growth factor receptor expres- Retinoic acid is a negative regulator of AP-1-respon- sion. Cancer Res., 53, 4511-4517 sive genes. Proc. Nat! Acad. Sci. USA, 88, 6092-6096 Slaga, T.J., Klein-Szanto, AJ., Fischer, S.M., Weeks, C.E., Schweiter, U., Englert, G., Rigassi, N. & Vetter, W. (1969) Nelson, K. & Major, S. (1980) Studies on mechanism Physical organic methods in carotenoid research. Pure of action of anti-tumor-promoting agents: their speci- App!. Chem., 20, 365-420 ficity in two-stage promotion. Proc. Nati Acad. Sci. Shah, G.M., Goswami, U.C. & Bhattacharya, R.K. (1992) USA, 77, 2251-2254 Action of some retinol derivatives and their provita- Soprano, D.R. & Soprano, KJ. (1995) Retinoids as terato- mins on microsome-catalyzed formation of benzo[a]- gens. Annu. Rev. NuIr., 15, 111-132 pyrene-DNA adduct. J. Biochem. Toxico!., 7, 177-181 Stam, C.H. & MacGillavry; C.H. (1963) The crystal struc- Shalinsky, D.R., Bischoff, ED., Gregory, M.L., Gottardis, ture of the triclinic modification of vitamin-A acid. M.M., Hayes, J.S., Lamph, W.W, Heyman, R.A., Acta Ciystallogr., 16, 62-68 Shirley, M.A., Cooke, TA., Davies, P.J. & Thomazy; V. Steele, V.E., Kelloff, GJ., Wilkinson, B.P. & Arnold, J.T. (1995) Retinoid-induced suppression of squamous (1990) Inhibition of transformation in cultured rat cell differentiation in human oral squamous cell car- tracheal epithelial cells by potential chemopreventive cinoma xenografts (line 1483) in athymic nude mice. agents. Cancer Res., 50, 2068-2074 Cancer Res., 55, 3183-3191 Stentoft, J., Nielsen, J.L. & Hvidman, L.E. (1994) All- Shenefelt, R.E. (1972) Morphogenesis of malformations trans- retinoic acid in acute promyelocytic leukemia in hamsters caused by retinoic acid: Relation to dose in late pregnancy. Leukemia, 8, 1585-1588 and stage at treatment. Teratology, 5, 103-118 Stich, H.F., Tsang, S.S. & Palcic, B. (1990) The effect of Shetty; T.K., Francis, A.R. & Bhattacharya, R.K. (1988) retinoids, carotenoids and phenolics on chromoso- Modifying role of vitamins on the mutagenic action mal instability of bovine papillomavirus DNA-carry- of N-methyl-N'-nitro-N-nitrosoguanidine. Carcino- ing cells. Mutat. Res., 241, 387-393 genesis, 9, 1513-1515 Suilk, K.K., Dehart, D.B., Rogers,J.M. & Chernoff, N. (1995) Shindoh, M., Sun, Q., Pater, A. & Pater, M.M. (1995) Teratogenicity of low doses of all-trans-retinoic acid in Prevention of carcinoma in situ of human papillo- presomite mouse embryos. Teratology, 51, 398403 mavirus type 16-immortalized human endocervical Surwit, E.A., Graham, V., Droegemueller, W., Alberts, D., cells by retinoic acid in organotypic raft culture. Chvapil, M., Dorr, R.T., Davis, J.R. & Meyskens, F.LJ. Obstet. Gynecol., 85, 721-728 (1982) Evaluation of topically applied trans-retinoic Shoyab, M. (1981) Inhibition of the binding of 7,12- acid in the treatment of cervical intraepithelial dimethylbenz[a]anthracene to DNA of murine epider- lesions. Am. J. Obstet. Gynecol., 143, 821-823 mal cells in culture by vitamin A and vitamin C. Sutton, L.M., Warmuth, M.A., Petros, W.P. & Winer, E.P. Oncology, 38, 187-192 (1997) Pharmacokinetics and clinical impact of all- Siegenthaler, G. & Saurat, J.H. (1989) Binding of trans-retinoic acid in metastatic breast cancer: A phase isotretinoin to cellular retinoic acid binding protein: II trial. Cancer Chemother. Pharmacol., 40, 335-341 A reappraisal. In: Marks, R. & Plewig, G., eds, Acne and Szuts, E.Z. & Harosi, El. (1991) Solubility of retinoids in Related Disorders. London, Martin Dunitz, pp. 169-174 water. Arch. Biochem. Biophys., 287, 297-304 Simone, M.D., Stasi, R., Venditti, A., Del Poeta, G., Takitani, K., Tamai, H., Morinobu, T., Kawamura, N., Aronica, G., Bruno, A., Masi, M., Tribalto, M., Papa, G. Miyake, M., Fujimoto, T. & Mino, M. (1995a) & Amadori, S. (1995) All-trans-retinoic acid (ATRA) Pharmacokinetics of all-trans-retinoic acid in pediatric administration during pregnancy in relapsed acute patients with leukemia. Jpn. J. Cancer Res., 86, 400-405 promyelocytic leukemia. Leukemia, 9, 1412-1413 Takitani, K., Tamai, H., Morinobu, T., Kawamura, N., Sirianni, S.R., Chen, H.H. & Huang, C.C. (1981) Effects of Miyake, M., Fujimoto, T & Mino, M. (1995b) 4-Oxo retinoids on plating efficiency; sister-chromatid retinoic acid for refractory acute promyelocytic

142 All-trans-Retinoic acid

leukemia in children with all-trans-retinoic acid ther- retinoid responsive element in the promoter region of apy. J. Nutr. Sci. Vitaminol. Tokyo, 41, 493-498 the human cytochrome P4501A1 gene. Biochem. Tang, X. & Edenharder, R. (1997) Inhibition of the muta- Biophys. Res. Commun., 201, 1205-1212 genicity of 2-nitrofluorene, 3-nitrofluoranthene and Verma, A.K. (1988) Inhibition of tumor promoter 12-0- 1-nitropyrene by vitamins, porphyrins and related tetradecanoylphorbol-13-acetate-induced synthesis compounds, and vegetable and fruit juices and sol- of epidermal ornithine decarboxylase messenger vent extracts. Food Chem. Toxico!., 35, 373-378 RNA and diacylglycerol-promoted mouse skin tumor Tembe, E.A., Honeywell, R., Buss, N.E. & Renwick, A.G. formation by retinoic acid. Cancer Res., 48, 2168-2173 (1996) All-trans-retinoic acid in maternal plasma and Verma, A.K., Shapas, B.G., Rice, H.M. & Boutwell, R.K. teratogenicity in rats and rabbits. Toxico!. App!. (1979) Correlation of the inhibition by retinoids of Pharmacol., 141, 456-472 tumor promoter-induced mouse epidermal ornithine Tickle, C., Alberts, B., Wolpert, L. & Lee, J. (1982) Local decarboxylase activity and of skin tumor promotion. application of retinoic acid to the limb bud mimics Cancer Res., 39, 419-425 the action of the polarizing region. Nature, 296, Vermeulen, SJ., Bruyneel, E.A., van Roy, F.M., Mareel, 564-566 M.M. & Bracke, M.E. (1995) Activation of the E-cadherin/- Trosko, J.E. & Ruch, R.J. (1998) Cell-cell communication catenin complex in human MCF-7 breast cancer cells by in carcinogenesis. Front. Biosci., 3, D208-D236 all-b-ans-retinoic add. Br. J. Cancer, 72, 1447-1453 Tzimas, G., Burgin, H., Collins, M.D., Hummler, H. & Vetter, W., Englert, G., P.igassi, N. & Schwieter, U. (1971) Nau, H. (1994a) The high sensitivity of the rabbit to Spectroscopic methods. In: Isler, O., Gutmann, H. & the teratogenic effects of 13-cis-retinoic acid Solms, U., eds, Carotenoids. Basel, Birkhauser Verlag, (isotretinoin) is a consequence of prolonged exposure pp. 189-266 of the embryo to 13-cis-retinoic acid and 13-cis-4-oxo- Wang, C.C., Campbell, S., Fumer, R.L. & Hill, D.L. (1980) retinoic acid, and not of isomerization to all-trans- Disposition of all-trans- and 13-cis-retinoic acids and retinoic acid. Arch. Toxico!., 68, 119-128 N-hydroxyethylretinamide in mice after intravenous Tzimas, G., Sass, JO., Wittfoht, W., Elmazar, M.M., administration. Drug Metab. Dispos., 8, 8-11 Ehlers, K. & Nau, H. (1994b) Identification of 9,13-di- Warrell, R.P., Jr, de Thé, H., Wang, Z.Y. & Degos, L. (1993) cis-retinoic acid as a major plasma metabolite of 9-ris- Acute promyelocytic leukemia. N. Engl. J. Med., 329, retinoic acid and limited transfer of 9-cis-retinoic acid 177-189 and 9,13-di-cis-retinoic acid to the mouse and rat Watanabe, T. & Pratt, R.M. (1991) Influence of retinoids embryos. Drug Metab. Dispos., 22, 928-936 on sister chromatid exchanges and chromosomes in Tzimas, G., Collins, M.D. & Nau, H. (1995) cultured human embryonic palatal mesenchymal Developmental stage-associated differences in the cells. Teratog. Carcinog. Mutag., 11, 297-304 transplacental distribution of 13-cis- and all-trans- Watanabe, R., Okamoto, S., Moriki, T., Kizaki, M., Kawai, retinoic acid as well as their glucuronides in rats and Y. & Ikeda, Y. (1995) Treatment of acute promyelocytic mice. Toxico!. App!. Pharmacol., 133, 91-101 leukemia with all-trans-retinoic acid during the third Tzimas, G., Nau, H., Hendrickx, A.G., Peterson, P.E. & trimester of pregnancy. Am. J. Hemato!., 48, 210-211 Hummler, H. (1996) Retinoid metabolism and Westin, S., Mode, A., Murray, M., Chen, R. & Gustafsson, transplacental pharmacokinetics in the cynomolgus J.A. (1993) Growth hormone and vitamin A induce monkey following a nonteratogenic dosing regimen P4502C7 mRNA expression in primary rat hepato- with all-trans-retinoic acid. Teratology, 54, 255-265 cytes. Mo!. Pharmacol., 44, 997-1002 Tzimas, G., Thiel, R., Chahoud, I. & Nau, H. (1997) The Whong, W.Z., Stewart, J., Brockman, H.E. & Ong, T.M. area under the concentration-time curve of all-trans- (1988) Comparative antimutagenicity of chloro- retinoic acid is the most suitable pharmacokinetic phyllin and five other agents against aflatoxin Bi- correlate to the embryotoxicity of this retinoid in the induced reversion in Salmonella typhimurium strain rat. Toxico!. App!. Pharmacol., 143, 436-444 TA98. Teratog. Carcinog. Mutag., 8, 215-224 Vahlquist, A. (1994) Role of retinoids in normal and dis- Willhite, C.C. & Clewell, H.J. (1999) Physiologically- eased skin. In: Blomhoff, R., ed., Vitamin A in Health based pharmacokinetic scaling in retinoid develop- and Disease. New York, Marcel Dekker, pp. 365-424 mental toxicity. In: Livrea, M., ed., Vitamin A and Vecchini, F., Lenoir, V.M., Cathelineau, C., Magdalou, J., Retinoids: An Update of Biological Aspects and Clinical Bernard, B.A. & Shroot, B. (1994) Presence of a Applications. Basel, Birkhäuser Verlag, pp. 121-128

143 IARC Handbooks of Cancer Prevention

Willhite, CC., Sharma, R.P., Allen, P.V. & Berry, D.L. Zancai, P., Cariati, R., Rizzo, S., Boiocchi, M. & Dolceffi, (1990) Percutaneous retinoid absorption and embryo- R. (1998) Retinoic acid-mediated growth arrest of toxicity. J. Invest. Dermatol., 95, 523-529 EBV-immortalized B lymphocytes is associated with Wilmer, J.W. & Spit, B.J. (1986) Influence of retinoids on multiple changes in G, regulatory proteins: p27P1 the mutagenicity of cigarette-smoke condensate in up-regulation is a relevant early event. Oncogene, 17, Salmonella typhimurium TA98. Mutat. Res., 173, 9-11 1827-1836 Yoon, J.H., Gray, T., Guzman, K., Koo, J.S. & Nettesheim, Zhuang, Y.H., Sainio, E.L., Sainio, P., Vedeckis, W.V., P. (1997) Regulation of the secretory phenotype of Ylikomi, T. & Tuohimaa, P. (1995) Distribution of all- human airway epithelium by retinoic acid, tri- trans-retinoic acid in normal and vitamin A deficient iodothyronine, and extracellular matrix. Am. J. Respir. mice: Correlation to retinoic acid receptors in differ- Cell. Mol. Biol., 16, 724-731 ent tissues of normal mice. Gen. Compar. Endocrinol., Yutsudo, Y., Imoto, S., Ozuru, R., Kajimoto, K., Itoi, H., 100,170-178 Koizumi, T., Nishimura, R. & Nakagawa, T. (1997) Acute pancreatitis after all-trans-retinoic acid therapy. Ann. Hematol., 74, 295-296

144