Relative Carcinogenic Activity of Various Synthetic and Natural Estrogens in the Syrian Hamster Kidney1

[CANCER RESEARCH 43, 5200-5204, November 1983]

Jonathan J. Li,2 Sara Antonia Li, John K. Klicka, Jonathan A. Parsons,3 and Luke K. T. Lam

Medical Research Laboratories, Veterans Administration Medical Center [J. J. L], and Departments of Urological Surgery [J. J. L, S. A. L, J. K. K.], Anatomy [J. A. P.], and Laboratory Medicine and Pathology [L K. T. L], University of Minnesota Medical School, Minneapolis, Minnesota 55455

ABSTRACT motive effects on cellular differentiation, there is a growing awareness of the carcinogenic potential of both natural and Both synthetic and natural estrogens have been studied for synthetic estrogens (4, 14, 18, 21). At present, there are no their ability to induce renal carcinomas in castrated male ham detailed studies demonstrating the relative carcinogenic activity sters after 9.0 months of treatment. Tumor foci were detected of various estrogens within a given animal tumor system. in frozen serial sections stained histochemically for esterase The hamster renal adenocarcinoma has provided a unique activity. Both diethylstilbestrol (DES) and 17.^-estradiol had equal model to investigate both hormonal and carcinogenic aspects of ability (100%) to induce renal tumors [~20.5 Â±3 (S.E.) tumor estrogen-induced tumorigenesis (5). Early studies in our labora foci] in these animals. Hexestrol induced the same incidence and tory strongly support a hormonal role for the induction of these number of renal carcinoma foci as DES or 17/3-estradiol. How tumors by estrogen. The demonstration of a specific high-affinity ever, a-dienestrol and DES 3,4-oxide showed an 86 to 88% estrogen receptor in renal cytosols of castrated hamsters which incidence of renal tumors in hamsters (~10.8 Â±3). When equilin is enhanced nearly 3.5-fold after prolonged estrogen administra and d-equilenin, components of therapeutic conjugated estro tion supports this contention (8). Pertinent also is the finding that gens, were tested, only equilin had a 76% incidence of renal estrogen-induced renal tumorigenesis in the hamster can be tumor foci (5.5 Â±0.9). The ability of these stilbene and steroidal completely blocked by those antiestrogens which inhibit mark estrogens to compete for renal tumor estrogen receptor gener edly estrogen receptor-binding activity (8). Moreover, estrogen ally correlated well with their ability to cause renal tumorigenesis treatment resulted in at least a 10-fold rise in cytosolic proges in the hamster with one notable exception. Although ethinyl terone receptor concentration in the untransformed kidney, and estradiol competed as well as did DES or 17/3-estradiol for this elevated receptor can be modulated by antiestrogens, an- estrogen receptor, had similar ability to induce renal progester drogens, and some synthetic progestins (11,15). However, our one receptor, and led to similar high serum prolactin levels as recent result concerning the inhibition of estrogen-induced kidney either DES or 17/3-estradiol, it had only weak carcinogenic activity transformation by Â»-naphthoflavone cannot be readily explained (21%) in the hamster kidney (0.6 Â± 0.5 foci). These data by hormonal mechanisms alone (12). In addition, the marked represent the first detailed analysis of the relative carcinogenic suppression of kidney aryl hydrocarbon hydroxylase activity, not activity of different estrogens within a given tumor-inducing evident in the liver, supports a pertinent role for P-450 multisub- system, and based on the carcinogenicity data of hexestrol and strate monooxygenases in effecting the tumorigenic response of a-dienestrol presented herein, they suggest that epoxidation of the hamster to estrogens (14). the olefinic double bond and the p-quinone metabolite of DES In an effort to discern the structural and hormonal require probably are not involved significantly in its carcinogenic activity. ments for estrogen carcinogenicity in the hamster kidney and to Moreover, the poor carcinogenic activity of ethinyl estradiol in elucidate the significance of particular intermediates in a path this system, despite strong estrogenicity. suggests that estronic way, we have undertaken to determine the carcinogenic potential activity alone may not be sufficient to effect renal tumorigenesis of various synthetic and natural estrogens to transform the in the hamster. hamster kidney. These data are correlated with the ability of these estrogens to compete for estrogen receptor binding, their INTRODUCTION ability to induce renal progesterone receptor in the untrans formed kidney, and in some instances their ability to elevate For over a decade, evidence has continued to accumulate serum PRL4 levels as determined by the Nb2 rat lymphoma cell indicating a causal link between estrogens and a variety of human bioassay. cancers involving vaginal, hepatic, breast, endometrial, and cer vical organ sites (1-3,17, 23). Although some of the tumorigenic effects of estrogen exposure are due undoubtedly to their pro- MATERIALS AND METHODS

1This investigation was supported by Grant CA 22008 from the National Cancer Chemicals and Reagents. 17/3-[2,4,6,7-3H]Estradiol (115 Ci/mmol), Institute, NIH. Department of Health and Human Services, and the General Medical [1,2,6,7-3H]progesterone (103 Ci/mmol), and [17a-mef/?y/-3H]R5020 (86 Research Fund of the Veterans Administration. Presented in part at the 24th Ci/mmol) were obtained from New England Nuclear, Boston, Mass. Congress of the European Society of Toxicology, Satellite Symposium on the Radioinert estradiol and progesterone, Chromatographie grade, were Mechanisms of Estrogen Carcinogenicity: Rote of Metabolites, Rome, Italy, March obtained from Calbiochem-Behring, San Diego, Calif., and all other 31,1983. 2To whom requests for reprints should be addressed, at the Medical Research nonlabeled steroids were purchased from Sigma Chemical Co., St. Louis, Laboratories, Veterans Administration Medical Center, 54th Street and 48th Avenue Mo. DES 3,4-oxide was synthesized by a procedure modified from that South, Minneapolis, Minn. 55417. 3 Recipient of Grant AM 26962 of the NIH, Department of Health and Human Services. 4 The abbreviations used are: PRL, prolactin; DES, diethylstilbestrol; FM, Fisch Received May 6, 1983; accepted August 2. 1983. er's medium.

5200 CANCER RESEARCH VOL. 43

Downloaded from cancerres.aacrjournals.org on September 25, 2021. © 1983 American Association for Cancer Research. Carcinogenic Activity of Estrogens in Hamster Kidneys of Metzler and McLachlan (22) using m-chloroperbenzoic acid. Trizma and some lower-affinity binding components. Protein concentration of base, Norit A, dextran 80, dithiothreitol, and 2-mercaptoethanol were the tumor cytosols (5 mg/ml) was determined by the method of Lowry supplied by Sigma. Ultrapure sucrose (RNase free) was obtained from et al. (16) using bovine serum albumin as a standard. Radioactivity Schwarz/Mann, Orangeburg, N. Y. Ovine PRL (NIAMDD-o-PRL-14, 31 sample measurements were assessed in a Packard Tri-Carb liquid scin ID/mg) was a gift of the National Hormone and Pituitary Program, tillation spectrometer (Model 3375; Packard Instrument Co., Inc., Down Baltimore Md. FM for leukemic cells of mice, fetal bovine serum, L- ers Grove, III.) with a counting efficiency for tritium of about 43% (10). glutamine, and antibioticiantimycotic (1OOx) were purchased from Grand Bioassay of Hamster PRL. The Mb, node rat lymphoma cells were Island Biological Co., Grand Island, N. Y. Horse serum was supplied by generously provided by Dr. R. L. Nobel and Dr. C. T. Beer, University of Sterile Systems, Logan, Utah. British Columbia, Vancouver, British Columbia, Canada. Cells were main TED (0.01 M Tris-HCI, 0.0015 M EDTA, and 0.001 M dithiothreitol) and tained in suspension culture and were conditioned and distributed for TEDG (TED plus 5% glycerol) buffers, pH 7.4, were prepared at room bioassay as has been described previously in detail (25). Ovine PRL was temperature as indicated previously (8,11,13). diluted with FM to give a final concentration of 0.05 to 5.0 ng/ml, sterilized Animals and Renal Tumor Induction. Adult castrated-male Syrian by filtration (Acrodisc, 0.22 Mm; Gelman Sciences, Inc.), and added to golden hamsters (LAK:LVG, outbred strain) were obtained from Charles 24-well tissue culture plates (Flow Laboratories, Inc., McLean, Va.) in River Lakeview Hamster Colony, Wilmington, Mass. Similar hypophysec- duplicate in aliquots of 100 Â¿ilorless. Hamster serum samples, obtained tomized male hamsters were also supplied from the same source. All from the orbit of the eye, were diluted 1:10 with FM containing 10% animals weighed between 85 and 95 g (50 to 55 days old) and were horse serum, filtered as above, and added to wells in aliquots of 50 and acclimated at least 1 to 2 weeks prior to treatment or use. Pure estrogen 100 n\. The plates were incubated at 37Â° for 72 hr in a humidified pellets, prepared without binder, were implanted in the shoulder region incubator in an atmosphere of 95% air:5% CO2. Determination of cell as described earlier (9). All animals were exposed to different estrogens number was made on a Coulter Counter. During the course of these for 9.0 to 9.2 months for induction of renal carcinomas. To maintain experiments, the dose of ovine PRL which induced a 50% inhibition of constant estrogen levels in these hamsters, hormone pellets were reim- cell ranged between 0.45 and 1.0 ng/ml and averaged 0.56 Â±0.15 ng/ planted at 3-month intervals. Ethmyl estradici pellets, however, were ml (8 assays). Within assay coefficient of variation based upon replicate absorbed more rapidly and were therefore reimplanted every 2 months. determination of standards ranged from 1.0 to 8.0%, and between-assay For progesterone receptor induction, hamsters were treated for 3.0 coefficient of variation was 20% (24). Since bioassay of the serum months with various estrogens as reported in detail elsewhere (11,15). samples was performed shortly after being drawn, representative sam The estrogen pellets used weighed 20 Â±1.4 (S.E.) mg. The mean daily ples spanning all of the assays were redetermined in a single assay at absorption expressed in /ug for the estrogens used was: DES, 170 Â±20 the end of the experiment. Potencies of these samples, which included (S.E.); a-dienestrol, 160 Â±10; hexestrol, 185 Â±10; DES 3,4-oxide, 101 sera of low (~20 ng/ml), medium (~100 ng/ml), and high (>200 ng/ml) Â±5; 170-estradiol, 112 Â±15; estrone, 100 Â±10; ethinyl estradici, 210 levels of PRL activity, were all similar to their initial potency estimates Â±10; equilin, 147 Â±22; and d-equilenin, 145 Â±15 (8). with a second determination to the first with a ratio of 1.16 Â±0.11 (S.E., High-Performance Liquid Chromatography Analyses of the Estro n = 16). gens. High-performance liquid Chromatography analyses were per formed on the estrogens investigated following pellet preparation and RESULTS after implantation for 3 to 6 months in the hamster to determine whether chemical integrity of the hormones was maintained. Estrogen samples Induction of Renal Tumors by Various Estrogens. The ability (10 ;/g) were dissolved in tetrahydrofuran (10 /Â¿I)and injected into a of different synthetic and natural estrogens to induce renal Hewlett-Packard Model 1084B liquid Chromatograph equipped with a adenocarcinomas in hamsters is summarized in Table 1. Both variable UV detector set at 284 nm. Separation was accomplished using DES and 17/3-estradiol induced a 100% incidence of bilateral and a reverse-phase column (0.46 x 25 cm; IBM Instruments, Inc., Danbury, Conn.) eluted with a linear gradient of 45 to 58% methanol in water over multiple renal tumors in castrated male hamsters treated for 9.0 60 min at a flow rate of 2.0 ml/min. The column temperature was months. Of the stilbene estrogens, hexestrol was equally effec maintained at 35Â°. The retention times of the estrogen samples were tive as either DES or 17/8-estradiol in producing renal carcinomas compared to authentic standards. No apparent changes in chemical following the same treatment period with a similar number of purity were observed following either pellet preparation or after prolonged combined tumor foci in each animal. On the other hand, the pellet implantation. synthetic estrogens, a-dienestrol and DES 3,4-oxide, produced Detection of Renal Tumor Foci. Analyses of the frequency of different a slightly lower renal tumor incidence and correspondingly de synthetic and natural estrogens to induce renal tumor foci were deter creased number of tumor foci compared to either DES or hex mined by a method described previously (8). Briefly, serial frozen kidney estrol for the same time period. Although estrone treatment sections (10 Â¿imthick) were prepared immediately after excision using a resulted in a reduced incidence (80%) of renal tumors as well as CTF Microtome cryostat (Damon, International Equipment Company) maintained at -18Â°. At least 25 to 30 unfixed frozen sections were taken a lower number of renal tumor foci compared to either DES- or 17/3-estradiol-treated animals, this latter difference was not sta from each kidney and subsequently stained for esterase activity using a-naphthyl butyrate as a substrate (8, 9). Microscopic examinations of tistically significant. Estrone tumor-inducing ability, however, was tumor foci were ascertained by the reduced esterase activity in the tumor notably slower when examined at an earlier treatment period compared to surrounding normal kidney tissue and by morphological (8.0 months) compared to the above-cited estrogens (data not criteria. shown). Of the 2 nonprimate natural estrogens, equilin treatment Competitive Binding Studies. Pure renal adenocarcinoma was ob resulted in a 75% incidence of renal tumors in male hamsters tained from either hamsters treated with DES for 9 to 11 months or first with a significantly lower number of combined renal tumor foci, to third serially transplanted primary renal tumors according to methods whereas no detectable tumor foci were found after prolonged d- reported previously (10,13). Renal carcinomas were homogenized in 8.0 equilenin treatment. Remarkably, ethinyl estradici resulted in only volumes of TED buffer, pH 7.4, and centrifuged at 100,000 x g. Estrogen receptor competitive binding studies were carried out on filtered cytosols a 20% incidence of renal tumors in hamsters and a markedly by a procedure presented earlier using 5 nM [3H]estradiol and various diminished number of tumor foci in these animals. Moreover, the concentrations (1- to 100-fold excess) of radioinert synthetic or natural renal carcinoma foci were considerably smaller than all other estrogens (10,13). Dextran:charcoal was used to remove free hormone effective estrogens when administered for the same time period.

NOVEMBER 1983 5201

Table 1 Carcinogen/city and estrogenici!y of various synthetic and natural estrogens In the Syrian hamster kidney Combined no. of No. of Animals % with tumor nodules in Competitive binding (% of inhibition)0 Estrogens" Structure animals with tumors tumors both kidneys

22.0 Â±3e 90.1 Â±0.9 (7)" DES 10 10 100

OH 10.4 Â±3e Â«-Dienestroi 88 88.6 Â±1.4(6)

OH Hexestrol 100 25.8 Â±6 90.4 Â±0.8(6)

.OH DES 3,4-oxide 86 11.4Â±3 90.0 Â±1.6(6)

OH 170-Estradiol 100 18.0 Â±4 89.8 Â±0.7 (8)

Estrone 10 80 10.4 Â±5 85.2 Â±1.3 (4)

0.6 Â±0.5' Ethinyl estradici 15 20 90.5 Â±1.1 (6)

Equilin 75 5.5 Â±O.sf 78.4 Â±1.7(5)

cf-Equilemn 49.2 Â±5.5(6)

* Duration of estrogen treatment was 8.7 months. After the initial pellet implantation, additional hormone pellets were implanted every 3 months except for ethinyl estradici. Because of the rapid absorption of the ethinyl estradici pellets, this synthetic estrogen was implanted every 2 months. " Competitive binding of radioinert estrogens for estrogen receptor was carried out on cytosols obtained from hamster estrogen-induced renal carcinomas. 13H|- Estradiol concentration in these tumor cytosols (4 to 5 mg/ml protein concentration), without competitor, corresponded to 0% inhibition. ' Mean Â±S.E. of the number of tumor foci per animal in each group. '' Numbers in parentheses, number of individual determinations. "p < 0.05 versus DES treated, p < 0.001 versus DES treated.

It should also be noted that neither the incidence not the com dienestrol also did not exhibit appreciable competition for estro bined number of renal tumor foci was enhanced following contin gen receptor binding at similar low concentrations. In contrast, uous treatment with ethinyl estradici for 10.3 months (data not DES 3,4-oxide, hexestrol, and ethinyl estradici all had nearly shown). identical abilities to displace labeled hormone from renal tumor Competitive Binding for Estrogen Receptor. As an indicator estrogen receptor as either DES or 170-estradtol at all concen of their relative estrogenicity in the hamster, natural and synthetic trations used. At 100-fold excess concentrations, only d-equi- estrogens were compared for their ability to compete with [3H]- lenin was markedly less effective in competing for estrogen estradiol for renal tumor cytosolic estrogen receptor at 1- to 100- receptor in the hamster renal tumor, while all the other estrogens fold excess concentrations. These data are shown in Chart 1. examined showed similar binding capabilities (Table 1; Chart 1). At low competitor concentrations (1- and 5-fold excess), both d- Induction of Progesterone Receptor in Untransformed Kid equilenin and equilin were poor competitors and could easily be neys. Specific progesterone binding was determined in kidneys distinguished from the more potent estrogens. Estrone and a- following in vitro incubation of cytosol fractions derived from

5202 CANCER RESEARCH VOL. 43

Downloaded from cancerres.aacrjournals.org on September 25, 2021. © 1983 American Association for Cancer Research. Carcinogenic Activity of Estrogens in Hamster Kidneys castrated male hamsters treated for 3.2 months with different estrogens. Table 2 summarizes the results of these experiments. Compared to untreated castrate levels, progesterone receptor was elevated about 10-fold after either DES or 17^-estradiol 400 treatment as reported previously (11). Except for d-equilenin, all estrogens studied elicited similar increases in specific progester one receptor using either radiolabeled progesterone or R5020. 300 These results are consistent with the ability of these synthetic and natural estrogens to compete with [3H]estradiol for renal O carcinoma cytosolic estrogen receptor as shown earlier. Â£ 200 Assay of Serum PRL. Using the Nb2 node rat lymphoma s replication bioassay, hamster serum PRL concentration was (C LU assessed in hypophysectomized and castrated hamsters as well UÃ¬ as in estrogenized animals treated for 1 to 4 months. Replication 100 of NÃ’2node rat lymphoma cells has been shown to be a sensitive and specific bioassay for hormonal lactogens derived from both human (25) and animal sources (7) and appears to be effective in assessing serum PRL activities in the hamster as well. Serial 01234

100 -i MONTHS AFTER ESTROGEN TREATMENT Chart 2. Serum PRL levels, determined at monthly intervals, were assayed by the Nbznode rat lymphoma cell bioassay in untreated matecastrated hamsters (O) 90- and in DES (â€¢),17,Â¡-estradici(â€¢),andethinyl estradici (A)-ireated animalsfor 1 to 4 months. Points, mean of 5 to 7 individualdeterminations; bars, S.E.

dilutions of hamster pituitary extract and pooled hamster sera

O yielded Nb2 node replication curves that were parallel to PRL CD standards. Hypophysectomized hamsters exhibited serum PRL levels of <10 ng/ml (n = 6), which is at the detectable threshold of the bioassay and indistinguishable from zero PRL controls. 0 On the other hand, serum PRL levels in castrated male hamsters

COMPETITOR CONCENTRATION (MOLES/LITER) DISCUSSION Chart 1. Competition of different radioinert estrogens for the binding of 17/3- 13Hlestradioito estrogen receptor in the hamsterrenalcarcinomacytosols. Aliquots At present, it is not known whether the oncogenic effects of of cytosol were incubated with 5 nwtritriated estradici alone or in combination with various concentrations (1- to 100-fold excess) of nonlabetedOES(â€¢),a-dienestrol estrogens are exerted through their hormonal properties or (â€¢),hexestrol(D), DES3,4-oxide (A), 17/3-estradtol(O),estrone (x), ethinylestradici whether they behave as chemical carcinogens. In this initial (A), equilin (â€¢),andtf-equilenin (<>), series, we have attempted to elucidate the structural require ments for estrogen carcinogenicity and to determine whether Table 2 selected estrogens, both stilbene and steroidal types, are capa Induction of progesterone receptor in male hamster kidneys after continuous administration of various estrogens ble of transforming the hamster kidney. Such data should aid in identifying the importance of a given metabolic pathway germane Progesterone receptor concentration for the carcinogenic effect of these hormones. The present Treatment" (fmol/mg cytosol protein) results confirm that both 170-estradiol and DES are equally Untreatedcontrol 3.1 Â±0.3" carcinogenic in the hamster kidney (5). The finding that hexestrol DES 29.5 Â±3.9C Â«i-Dienestrol 20.3 Â±2.9e is a potent tumorigenic agent in this organ demonstrates clearly Hexestrol 27.7 Â±1.6Â° that epoxidation of the olefinic double bond is not necessary for 31.2 Â±2.5e 17,1-Estradiol estrogen carcinogenesis in the hamster kidney, since hexestrol, Estrone 27.6 Â±5.5C Equilin 28.0 Â±6.0Â° lacking the stilbene double bond, is unable to convert to DES d-Equitenin 9.2 Â±1.7 3,4-oxide, a metabolite which has been suggested previously as 35.0 Â±5.0Â° Ethinyl estradici a possible reactive intermediate (19). Consistent with this obser " Castrated malehamsters were treated with estrogensfor 3.2 months; hormone vation is that DES 3,4-oxide possesses a lower ability to effect pellets were withdrawn 24 hr before killing. 0 Mean Â±S.E.of at least 3 separate determinations. renal transformation in this species. Moreover, since both <*- c Statistically significantlydifferent from control (p < 0.001). dienestrol and hexestrol are active tumorigenic agents in this

NOVEMBER 1983 5203

system, the p-quinone metabolites (4,4"-quinones) are unlikely treatment with synthetic estrogens. N. Engl. J. Med., 285: 390-392,1971. 2. Herbst. A. L. Clear cell adenocarcinoma and current status of DES-exposed to be pertinent, as these stilbene-type estrogens have not been females. Cancer (Phila.), 48: 484-488,1981. shown to form these oxidative intermediates (20,22). In contrast, 3. Hoover, R., Glass, A., Finkie. W. D . Azevedo, D., and Milne, K. Conjugated it should be noted that both hexestrol and Â«-dienestrol have estrogens and breast cancer risk in women. J. Nati. Cancer Inst., 67: 815- 820,1981. been shown to be poor inducers of in vitro neoplastic transfor 4. Homing, E. C., Thenot, J-P., and Helton, E. D. Toxic agents resulting from the mation of Syrian hamster embryo fÂ¡broblasts(18). indicating that oxidative metabolism of steroid hormone and drugs. J. Toxicol. Environ. Health, 4; 341-361,1978. in vitro models in some respects do not adequately mimic in vivo 5. Kirkman, H. Estrogen-induced tumors of the kidney in Syrian hamsters. Nati. tumor-inducing systems. Of the natural estrogens, estrone ap Cancer Inst. Monogr., 7: 1-59, 1959. peared slightly less carcinogenic in its ability to transform the 6. Korach, K. S., Metzler, M., and McLachlan, J. A. Estrogene activity in vivo and in vitro of some diethylstilbestrol metabolites and analogs. Proc. Nati. hamster kidney, and this could be partially due to the lower rate Acad. Sei. U. S. A., 75: 468-471,1978. of absorption of this hormone. Of the nonprimate natural estro 7. Lawson, D. M., Sensui, N., Haisenleder, D. H., and Gala, R. R. Rat lymphoma gens studied, equilin was found to be carcinogenic in the hamster cell bioassay for prolactin: observations on its use and comparison with radioimmunoassay. Life Sci., 37: 3063-3070,1982. kidney, whereas d-equilenin was completely ineffective. It is 8. Li, J. J., Cuthbertson, T. L., and Li, S. A. Inhibition of estrogen carcmogenesis apparent that, to be consistent with the results presented herein, in the Syrian golden hamster kidney by antiestrogens. J. Nati. Cancer Inst., 64: 795-800,1980. the most probable reactive electrophilic intermediates which may 9. U, J. J., Kirkman, H., and Hunter, R. L. Sex difference and gonadal hormone be critical in transformation of the hamster kidney would involve influence on Syrian hamster kidney esterase isozymes. J. Histochem. Cyto- metabolism in the A ring to either arene oxide or o-semiquinone:- chem., 77:386-393,1968. 10. Li, J. J., and Li, S. A. High yield primary serially transplanted hamster renal quinone (or both) of stilbene and steroidal estrogens. It is also carcinoma: histologie and steroid receptor characteristics. Eur. J. Cancer, 76: conceivable that other hydroxylated intermediates in the catechol 1119-1126,1980. pathway which possess these above-mentioned electrophilic 11. Li, J. J., and Li, S. A. Estrogen-induced progesterone receptor in the Syrian hamster kidney. II. Modulation by synthetic progestms. Endocrinology, 108: groups may also be involved in transforming the hamster kidney. 1751-1756,1981. Although the nonprimate natural estrogens as well as estrone 12. Li. J. J., and LI. S. A. Inhibition of estrogen-induced renal tumorigenesis in the and .,-dienestrol can be distinguished easily at low concentra Syrian golden hamster by BHA, .;- and a-naphthoflavone. Proc. Am. Assoc. Cancer Res., 22:11,1981. tions with respect to their competitive binding for estrogen 13. U, J. J., U, S. A., and Cuthbertson, T. L. Nuclear retention of all steroid receptor, at higher excess concentrations (1OOx), except for d- hormone receptor classes in the hamster renal carcinoma. Cancer Res., 39: 2647-2651,1979. equilenin, all estrogens examined exhibited similar ability to com 14. u, S. A., Lam, L. K. T., and U, J. J. Effect of steroid hormone treatment on pete for radiolabeled hormone (6,13) and to induce progesterone aryl hydrocarbon hydroxylase activity in the Syrian hamster kidney. Biochem. receptor. Most interesting, however, is the finding that ethinyl Pharmacol , in press, 1983. 15. Li, S. A., and Li, J. J. Estrogen-induced progesterone receptor in the Syrian estradiol is a relatively poor inducer of renal carcinomas while hamster kidney. I. Modulation by antiestrogens and androgens. Endocrinology, retaining its strong estrogenicity in the hamster kidney in terms 703:2119-2128,1978. 16. Lowry, O. H., Rosebrough, N. J., Fair, A. L., and Randall, R. J. Protein of its competitive binding for estrogen receptor, ability to induce measurements with the Folin phenol reagent. J. Biol. Chem., 793: 265-275, progesterone receptor, and ability to elevate serum PRL concen 1951. trations in the hamster to essentially the same level as either 17. Lyon, F. A. The development of adenocarcinoma of the endometrium in young 17/3-estradiol or DES. While our previous studies have suggested women receiving long term sequential oral contraception. Am. J. Obstet. Gynecol., 723: 299-301,1975. an intimate relationship between hormonal and carcinogenic 18. McLachlan, J. A., Wong, A., Degan, G. H., and Barrett, J. C. Morphological effects of estrogens on the tumorigenic process in this organ and neoplastic transformation of Syrian hamster embryo fibroblasts by dteth- ylstilbestrol and its analogs. Cancer Res., 42: 3040-3045,1982. site, this observation indicates that these 2 effects are partially 19. Metzter, M. Metabolic activation of diethylstilbestrol: indirect evidence for the dissociable. It also further suggests that, while hormonal activity formation of a stilbene oxide intermediate in the hamster and rat. Biochem. may be necessary for renal tumorigenesis, it may not itself be Pharmacol., 24:1449-1453,1975. 20. Metzler, M. Studies on the mechanism of carcinogemcity of diethylstilbestrol: sufficient to cause transformation of the hamster kidney. rote of metabolic activation. Food Cosmet. Toxicol., 79: 611-615,1981. 21. Metzler, M., and McLachlan, J. A. Oxidative metabolites of diethylstilbestrol in fetal, neonatal, and adult mouse. Biochem. Pharmacol., 27:1087-1094,1978. ACKNOWLEDGMENTS 22. Metzter, M., and McLachlan, J. A. Oxidative metabolism of the synthetic We are grateful for the technical assistance of Michele C. Olson and Richard estrogens hexestrol and dienestrol indicates reactive intermediates. Adv. Exp. Kempt in these studies. We are also grateful to Kathy Ensrud and Margaret Hartfel Med. Biol., 736: 829-837,1981. for carrying out the PRL bioassays. 23. Nissen, E. D., and Kent, D. R. Liver tumors and oral contraceptives. Obstet. This paper is dedicated to Dr. Thaddeus Domanski, Chief of the Chemical and Gynecol., 46: 460-467,1975. 24. Parsons, J. A., Jones, C. A., and Hartfel, M. A. Studies on the binding of 125I- Physical Carcinogenesis Branch, Division of Cancer Cause and Prevention, National Cancer Institute, NIH, DHHS, upon his retirement and in appreciation for his service ovine prolactin to Nt>2node rat lymphoma cells (abstract). Proc. Endocr. Soc., to the cancer research effort. 338,1982. 25. Tanaka, T., Shiu, R. P. C., Gout, P. W., Beer, C. T., Noble. R. L., and Friesen, H. G. A new sensitive and specific bioassay for lactogenic hormones: mea REFERENCES surement of prolactin and growth hormone in human serum. J. Clin. Endocrino! Metab.. 57: 1058-1063,1980. 1. Greenwaid, P., Barolorn. J. j.. and Nasca, P. C. Vaginal cancer after maternal

5204 CANCER RESEARCH VOL. 43

Downloaded from cancerres.aacrjournals.org on September 25, 2021. © 1983 American Association for Cancer Research. Relative Carcinogenic Activity of Various Synthetic and Natural Estrogens in the Syrian Hamster Kidney

Jonathan J. Li, Sara Antonia Li, John K. Klicka, et al.

Cancer Res 1983;43:5200-5204.

Updated version Access the most recent version of this article at: http://cancerres.aacrjournals.org/content/43/11/5200

E-mail alerts Sign up to receive free email-alerts related to this article or journal.

Reprints and To order reprints of this article or to subscribe to the journal, contact the AACR Publications Subscriptions Department at [email protected].

Permissions To request permission to re-use all or part of this article, use this link http://cancerres.aacrjournals.org/content/43/11/5200. Click on "Request Permissions" which will take you to the Copyright Clearance Center's (CCC) Rightslink site.