Lipoxygenase Inhibitors As Potential Cancer Chemopreventives

Home , Leukotriene B4, Pranlukast, Zafirlukast, Zileuton

Vol. 8, 467–483, May 1999 Cancer Epidemiology, Biomarkers & Prevention 467

Review Lipoxygenase Inhibitors as Potential Cancer Chemopreventives

Vernon E. Steele,1 Cathy A. Holmes, Ernest T. Hawk, potential, particularly in the lung, where topical Levy Kopelovich, Ronald A. Lubet, James A. Crowell, application of such formulations is feasible. Caroline C. Sigman, and Gary J. Kelloff Chemoprevention Branch, Division of Cancer Prevention, National Cancer Introduction Institute, Bethesda, Maryland 20892 [V. E. S., E. T. H., L. K., R. A. L., J. A. C., G. J. K.], and CCS Associates, Mountain View, California 94043 Eicosanoids derived from the arachidonic acid cascade have [C. A. H., C. C. S.] been implicated in the pathogenesis of a variety of human diseases, including cancer, and are now believed to play important roles in tumor promotion, progression, and metastatic 2 Abstract disease. Although most attention has focused on PGs and other Mounting evidence suggests that lipoxygenase (LO)- COX-derived metabolites, mounting evidence suggests that catalyzed products have a profound influence on the LO-catalyzed products, LTs, and HETEs also exert profound development and progression of human cancers. biological effects on the development and progression of hu- Compared with normal tissues, significantly elevated man cancers. For example, 12-LO mRNA expression has been levels of LO metabolites have been found in lung, well-documented in many types of solid tumor cells, including those of prostate, colon, and epidermoid carcinoma (1, 2). Also, prostate, breast, colon, and skin cancer cells, as well as in 3 cells from patients with both acute and chronic 12(S)-HETE production by some tumor cells, including pros- leukemias. LO-mediated products elicit diverse biological tate cells, has been positively correlated to their metastatic activities needed for neoplastic cell growth, influencing potential (3, 4). Also, studies show that 12(S)-HETE is a critical growth factor and transcription factor activation, intracellular signaling molecule, stimulating PKC and eliciting oncogene induction, stimulation of tumor cell adhesion, the biological actions of many growth factors and cytokines that and regulation of apoptotic cell death. Agents that block regulate transcription factor activation and induction of onco- LO-catalyzed activity may be effective in preventing genes or other gene products needed for neoplastic cell growth cancer by interfering with signaling events needed for (5–7). Some of these include EGF, FGF, PDGF, tumor necrosis tumor growth. In fact, in a few studies, LO inhibitors factor, granulocyte-macrophage colony-stimulating factor, and have prevented carcinogen-induced lung adenomas and both IL-1 and IL-3 (8–12). Additionally, PKC activation by rat mammary gland cancers. 12(S)-HETE mediates the release and secretion of cathepsin B, During the past 10 years, pharmacological agents a cysteine protease involved in tumor metastasis and invasion, that specifically inhibit the LO-mediated signaling particularly in colon cancer cells (13). Furthermore, tumor cell pathways are now commercially available to treat synthesis of 12(S)-HETE stimulates adhesion by increasing the inflammatory diseases such as asthma, arthritis, and surface expression of integrin receptors (14, 15). Besides 12(S)- psoriasis. These well-characterized agents, representing two general drug effect mechanisms, are considered good candidates for clinical chemoprevention studies. One 2 mechanism is inhibition of LO activity (5-LO and The abbreviations used are: PG, prostaglandin; COX, cyclooxygenase; LO, lipoxygenase; LT, leukotriene; HETE, hydroxyeicosatetraenoic acid; PKC, pro- associated enzymes, or 12-LO); the second is leukotriene tein kinase C; EGF, epidermal growth factor; FGF, fibroblast growth factor; receptor antagonism. Although the receptor antagonists PDGF, platelet-derived growth factor; IL, interleukin; PLA2, phospholipase A2; have high potential in treating asthma and other diseases FLAP, 5-LO activating protein; PMN, polymorphonuclear neutrophil; HODE, where drug effects are clearly mediated by the hydroxyoctadecadienoic acid; GRP, gastrin-releasing peptide; IGF, insulin-like growth factor; NDGA, nordihydroguaiaretic acid; BHPP, N-benzyl-N-hydroxy- leukotriene receptors, enzyme activity inhibitors may be 5-phenylpentanamide; TGF, transforming growth factor; MNU, N-nitrosomethy- better candidates for chemopreventive intervention, lurea; DMBA, 7,12-dimethylbenz(a)anthracene; TPA, phorbol 12-myristate 13- because inhibition of these enzymes directly reduces fatty acetate; ODC, ornithine decarboxylase; FDA, Food and Drug Administration; acid metabolite production, with concomitant damping of ZD2138, 6-((fluoro-5-(tetrahydro-4-methoxy-2H-pyran-4-yl)phenoxy)methyl)-1- methyl-2(1H)-quinolinone; MK-886, 3-(1(9p-chlorobenzyl)-5-(isopropyl)-3-tert- the associated inflammatory, proliferative, and metastatic butylthioindol-2-yl)-2,2-dimethylpropanoic acid; MK0591, 3-(1((4-chloro- activities that contribute to carcinogenesis. However, phenyl)methyl)-3-((1,1-dimethylethyl)thio)-5-(quinolin-2-ylmethyloxy)-1H- because receptor antagonists have aerosol formulations indol-2yl)-2,2-dimethyl-propanoate; BAY-X1005, (R)-2-(4-(quinolin-2-yl- and possible antiproliferative activity, they may also have methoxy)phenyl)-2-cyclopentyl acetic acid; SC 41930, 7-(3-(4-acetyl-3methoxy- 2-propylphenoxy)propoxy)-3,4-dihydro-8-propyl-2H-1-benzopyran-2-carboxylic acid; f-MLP, N-formyl-l-methionyl-l-leucyl-l-phenylalanine; SC 53228, 7-(3-(2- (cyclopropylmethyl)-3-methoxy-4-((methylamino)carbonyl)phenoxy)propoxy)- 3,4-dihydro-8-propyl-2H-1-benzopyran-2-propanoic acid; esculetin, 6,7- dihydroxy-2H-1-benzopyran-2-one; MAC, murine colon adenocarcinoma; Received 10/16/98; revised 3/2/99; accepted 3/10/99. baicalein, 5,6,7-trihydroxy-2-phenyl-4H-1-benzopyran-4-one; ACF, aberrant The costs of publication of this article were defrayed in part by the payment of crypt foci. page charges. This article must therefore be hereby marked advertisement in 3 Throughout this manuscript, references are made to studies of 12-HETE. If it is accordance with 18 U.S.C. Section 1734 solely to indicate this fact. clear from the published study report that the form is 12(S)-HETE, it is so 1 To whom requests for reprints should be addressed, at National Cancer Institute, designated. If the form is not specified or cannot otherwise be determined, the Division of Cancer Prevention, Chemoprevention Branch, EPN 201E, MSC 7322, compound is cited simply as 12-HETE. Probably many of the 12-HETEs cited are 9000 Rockville Pike, Bethesda, MD 20892-7322. actually 12(S)-HETE. We apologize for this unavoidable lack of clarity.

Table 1 LO inhibition: Potential chemopreventive mechanisms

Chemopreventive mechanism Specific activity Antiproliferation 12-LO inhibition Modulate signal transduction (5) 2PKC (5–7, 91, 213), cAMP (214, 215), tyrosine kinase (216, 217) Modulate growth factor activity (8–10, 71, 119, 218, 219) 2EGF, FGF, PDGF, tumor necrosis factor, GRP, K-ras,c-myc, int-2 Inhibit oncogene expression (94, 137, 220) Apoptosis induction (155, 221, 222) 5-LO, 12-LO inhibition Antioxidant activity (145) 2Free radical production Block metabolic activation (72, 73) Angiogenesis inhibition 12-LO inhibition Inhibit membrane degradation (13) 2Cathepsin B Decrease tumor cell adhesion (7, 9) 2Endothelial cell growth Decrease tumor cell motility (223) Inhibit metastasis (2, 4) Antiinflammatory 5-LO/FLAP inhibition Prevent tissue damage (224–226) 2PMN activation Modulate immune response (227) 2T-lymphocyte activation

HETE, other LO metabolites, particularly the 5-LO products either PLA2, or by the combined actions of phospholipase C (5-HETEs), have been implicated in cancer development. For and diacylglycerol kinase or phospholipase D and PLA2 (18). example, data published recently show that 5-HETE directly In leukocytes, cytokines including IL-1 and tumor necrosis

stimulates prostate cancer cell growth (16). Like 12(S)-HETE, factor can activate PLA2 by stimulating a phospholipase-acti- these molecules are capable of exerting pleiotropic effects on vating protein (20). Once released, arachidonic acid is either normal and malignant cells through autocrine- and paracrine- converted by catalytic action of 5-, 12-, or 15-LOs into the mediated mechanisms. Taken together, these data imply that corresponding HETEs or is metabolized into LTs or lipoxins LO products, particularly those of 5- and 12-LO, may play through additional sequential reactions, which depend on the important roles in modulating cancer development. On the basis biosynthetic capacity of each specific cell type (see below). of this information, pharmaceutical agents that directly interfere LT production proceeds via 5-LO, which catalyzes the with the production of LO metabolites or antagonize the sig- first two steps in the metabolic cascade. 5-LO in the presence naling functions of LO products may be effective in preventing of FLAP catalyzes the oxygenation of arachidonic acid into cancer. Table 1 lists potential chemopreventive mechanisms 5-hydroperoxyeicosatetraenoic acid, followed by a second re- associated with inhibition of the LO pathway. action in which 5-hydroperoxyeicosatetraenoic acid is dehy- Over the past 10 years, pharmacological agents that spe- drated to form the epoxide LTA4. Once formed, LTA4 is further cifically inhibit the LO metabolic pathway have been developed metabolized to either LTB4 via stereoselective hydration by to treat inflammatory diseases such as asthma, ulcerative colitis, LTA4 hydrolase or to LTC4 through glutathione conjugation arthritis, and psoriasis. As inflammatory mediators, LTs elicit a catalyzed by LTC4 synthase. Sequential metabolic reactions, number of reactions, including vessel wall adhesion, smooth catalyzed by ␥-glutamyl transferase and a specific membrane- muscle contraction, granulocyte degranulation, chemotaxis, bound dipeptidase, convert LTC4 into LTD4 and LTE4, respec- and increased mucous secretion and vascular permeability (17). tively. These three sulfidopeptide LTs are commonly referred These agents include 5-LO inhibitors of the N-hydroxyurea to as the slow-reacting substances of anaphylaxis (21). In the series developed by Abbott [Leutrol, Zyflo (Zileuton), and lung, sulfidopeptide LTs are known to act on a single high- ABT-761] and, among others, the redox inhibitor AA-861 affinity, smooth muscle receptor, the cys-LT1 receptor (22), (Takeda Chemical), the non-redox inhibitor ZD2138 (Zeneca), resulting in bronchoconstriction and alterations in vascular per- agents that interact with the FLAP, including MK-0591 meability and mucous secretion in this tissue (23). Important (Merck) and BAY-X1005 (Bayer), and LTB4 receptor antago- cellular sources of these LTs include eosinophils, mast cells, nists SC 41930 (Searle), Accolate (zafirlukast; Zeneca), Singu- and basophils (24). lair(montelukast; Merck), and Ultair (pranlukast; Ono/Smith- The intracellular localization of 5-, 12-, and 15-LO pro- Kline Beecham). Baicalein and esculetin are among several teins varies depending on the enzyme and specific cell type experimental compounds demonstrating 12-LO inhibitory ac- (25). In human PMNs, 5-LO was initially reported to be a tivity that may show promise as antiproliferative agents. This soluble, cytosolic protein (26, 27). However, later studies report discusses the current clinical status of these and other showed that, upon activation with Ca2ϩ, 5-LO translocates agents and methods to assess their cancer chemopreventive from the cytosol to the nuclear membrane (28), where it inter- potential and offers an overview of the LO biosynthetic path- acts with FLAP, an M 18,000 protein that resides in the nuclear way, its metabolic products, and their significance in human r envelope (29, 30). Indeed, reversible shifting of 5-LO protein disease and the development of cancer. between soluble and membrane-bound forms has been confirmed by other investigators (28, 31), although with differ- LO Biochemistry and Molecular Biology ences in distribution patterns and trafficking in various cell The LOs comprise a family of non-heme iron-containing di- types (32–35). Subcellular localization studies suggest that oxygenases that catalyze the stereospecific oxygenation of the translocation of 12-LO protein from the cytosol to membrane 5-, 12-, or 15-carbon atoms of arachidonic acid (17–19). In also occurs upon activation (36, 37), whereas 15-LO appears to cells, arachidonic acid is esterified to membrane phospholipids exist only in cytosol (38, 39). in the sn2 position. As depicted in Fig. 1, the reaction begins Metabolic products of the 5-, 12-, or 15-LO biosynthetic with the intracellular release of arachidonic acid, mediated by pathways modulate the growth of several normal human cells

LO Metabolites in Carcinogenesis Evidence from studies in human cancer cells shows that the LO pathways are involved in carcinogenesis in several major tissues. More importantly, a few studies in animal carcinogenesis models show that inhibition of the LO pathways also may inhibit carcinogenesis. Lung. Two recent studies found that LO inhibitors (specifically of the 5-LO pathway) have chemopreventive activity in animal lung carcinogenesis. Moody et al. (69) and Rioux and Castonguay (70) showed that the FLAP inhibitor MK 886 (25 mg/kg diet) and 5-LO inhibitor A 79175 (75 mg/kg diet) significantly reduced the multiplicity of NNK-induced tumors in strain A/J mice; A 79175 also reduced tumor incidence. In the same study, aspirin (294 mg/kg diet) reduced tumor mul- Fig. 1. LOs and arachidonic acid metabolism. tiplicity; the combination of aspirin and A 79175 (i.e., inhibit- ing both the COX and LO pathways) synergistically lowered tumor incidence and multiplicity. These results strongly suggest that 5-LO pathway inhibitors may have chemopreventive ac- types, including T lymphocytes (40), skin fibroblasts (41), tivity in lung. epidermal keratinocytes (42), and glomerular epithelial cells Supporting evidence links LO metabolites with lung cancer cell growth. Studies conducted by Avis et al. (71) in several (43). Both LTB4 and LTC4 increase in vitro growth of arterial smooth muscle cells (44), airway epithelial cells (45), and human lung cancer cell lines (small cell and non-small cell) mitogen-stimulated lymphocytes (46). Besides these cells, LTs found that 5-LO is stimulated by two autocrine growth factors, play important roles in regulating both human and murine GRP and IGF, both of which stimulate production of 5-HETE. 5-HETE stimulated the growth of lung cancer cells, whereas hematopoiesis (47–50). cells treated with 5-LO inhibitors NDGA, AA-861, and MK- The 5-, 12-, and 15-LO genes have been cloned and 886 showed decreased proliferation; the COX inhibitor aspirin sequenced in several mammalian species (25, 51). Several had little effect. Expression of 5-LO and FLAP mRNA by lung isoforms of 12-LO have been characterized, each with distinct cancer cell lines was confirmed using reverse transcription- genomic sequences, gene structure, immunogenicity, and sub- PCR, and the presence of 5-LO mRNA was identified in sam- strate specificity (51–53). These include human platelet-type ples of primary lung cancer tissue, including both small cell and 12-LO, referred to as P-12-LO, which metabolizes arachidonic non-small cell lung carcinomas. acid into 12(S)-HETE (54); the leukocyte type, or L-12-LO, Also relevant to lung cancer development are studies dem- which converts arachidonic acid or linoleic acid into 12(S)- onstrating that LOs mediate oxidation of potent carcinogens HETE and also produces small quantities of 15(S)-HETE (55); such as benzidine, o-dianisidine, and others; this activation can and 12-LO, a unique epithelial type first isolated from bovine be blocked by adding the LO inhibitors NDGA and esculetin tracheal epithelial cells, which catalyzes the synthesis of both (72). Rat lung LO also oxidizes benzo(a)pyrene (73); LOs have 12(S)- and 15(S)-HETE from arachidonic acid (56, 57). How- been found in human lung tissue by other investigators (74, 75). ever, these classifications are not precise. P-12-LO has also Prostate Cancer. Altered eicosanoid biosynthesis in relation been identified in human keratinocytes and epidermal carci- to prostate cancer development has been documented. Initial noma cells lines, and L-12-LO has been found in peritoneal studies found dramatically reduced levels of arachidonic acid; macrophages, trachea epithelium, whole brain, and other 10-fold greater turnover in malignant versus benign prostatic sources, although it is not expressed in mouse leukocytes (25). tissue suggested a possible increase in metabolism via the LO Yamamoto et al. (58) recently reviewed the molecular struc- and COX pathways in this tissue (76, 77). Linoleic acid stim- ture, catalytic properties, and biological activities of the 12-LO ulated cell growth in experiments conducted in human prostate isoenzymes. cancer cells, whereas indomethacin, esculetin, and piroxicam Mapped to chromosome 10, the human 5-LO gene appears inhibited it, substantiating the involvement of eicosanoids in the least related to LO genes such as P-12-LO and 15-LO, prostate cancer cell proliferation (78). Although attention has which are located on chromosome 17 (59). In cDNA compar- focused on COX-derived products (79–81), particularly PGE2 isons, L-12-LO shows greater sequence homology (80–90%) to (77), COX inhibitors indomethacin and aspirin failed to reduce 15-LO than does P-12-LO (60–70%; Ref. 60). Genetic analysis human prostate PC3 cell DNA synthesis, although arachidonic found that all LOs contain a highly conserved region of five acid antagonist eicosatetraynoic acid did reduce synthesis (82, histidine residues, possible binding sites for non-heme iron 83), suggesting that LO products are essential in modulating (61). Site-directed mutagenesis experiments with human 5-LO prostate DNA synthesis. However, until 5-LO products are further showed that two of the five histidine residues are nec- recovered from prostate tissue and their synthesis directly essary for LO catalytic activity (62, 63). To date, no genetic shown to be inhibited by 5-LO inhibitory agents, other possible defects at the 5- or 12-LO locus have been described. Several mechanisms cannot be ruled out. reports identified P-12-LO deficiency in myeloproliferative Additional studies by Anderson et al. (84) show reduced bleeding disorders (64, 65). DNA synthesis and growth inhibition of prostate cancer cells Specific factors that regulate LO gene expression have with specific 5-LO inhibitors (A63162; Abbott), further sup- been identified. Glucose, EGF, and angiotensin II stimulate porting involvement of the LO metabolic pathway in prostate 12-LO mRNA expression, production of HETEs and HODEs cancer growth. Likewise, recent work by Ghosh and Myers (16) (35, 66), and both IL-4 and IL-13 are positive regulators of using PC-3 cells provides convincing evidence that the 5-LO monocyte 15-LO gene expression (67, 68). metabolic pathway stimulates prostate cancer cell growth. More

specifically, 5-HETE, particularly the 5-oxo-eicosatetraenoic Additional evidence implicating eicosanoids in human form, stimulates PC-3 cell growth similarly to arachidonic acid; breast carcinogenesis stems from analysis of benign and ma- LTs had no effect. 5-HETEs also effectively reversed growth lignant breast tissue. Markedly elevated levels of both COX and inhibition produced by MK-886 (Merck), a FLAP inhibitor. LO metabolites have been documented in human breast cancer Both MK-886 and AA-861 effectively blocked prostate tumor tissue compared with tissue from patients with benign disease proliferation induced by arachidonic acid, whereas the COX (102). Recently, Natajaran et al. (103) studied 12-LO mRNA inhibitor ibuprofen and 12-LO inhibitors baicalein and BHPP expression in matched, normal, nontumorous and cancerous were ineffective. breast tissue from a small group of patients. In cancerous tissue, Besides 5-LO products, other LO metabolites have been 12-LO mRNA expression increased 3–30-fold compared with implicated in prostate tumor growth. The 12-LO metabolite normal tissue, which contained barely detectable levels. Simi- 12(S)-HETE plays a critical role in prostate tumor metastasis larly, greater 12-LO mRNA amounts were documented in two and invasion (1). In 122 matched normal and cancerous prostate breast cancer cell lines (MCF-7 and COH-BR1) compared with tissues, 12-LO mRNA expression was confined to prostate a noncancerous breast epithelial cell line (MCF-10). epithelial cells and elevated in malignant cells (3). Also, ele- Stimulation of breast cancer cell growth by linoleic acid vated levels of 12(S)-HETE mRNA significantly correlated has further been substantiated in vitro in several human breast with advanced stage, poor differentiation, and invasive poten- cancer cell lines (MDA-MB-231, MDA-MB-435, and MCF-7; tial of prostate cancer cells. Indeed, addition of 12(S)-HETE to Refs. 104–106); the inhibitory action of other n-3 fatty acids, rat Dunning R3327 and human prostate adenocarcinoma cells including docosahexaenoic acid (22:6) and eicosapentaenoic significantly increased their cellular motility and ability to acid (20:5), have also been reported in these cells (104–106). invade basement membrane and correlated with their metastatic Likewise, increased secretion of both LO and COX products, potential (85–87). Additional biochemical evidence demon- including 12- and 15-HETE and PGE2, has been documented in ␮ strated that 12(S)-HETE stimulates secretion of cathepsin B, human breast cancer cells (MDA-MB-435) treated with 2.7 M which is involved in tumor metastases and integrin expression linoleic acid (104). In the same study, linoleic acid enhanced in other tumor cells (13), providing support for the importance the invasive capacity of breast cancer cells; this effect could be ␮ of LO products in the development and spread of prostate and completely blocked by adding esculetin (20 M), an inhibitor of other human cancers. More recently, Liu et al. (6) have shown 5- and 12-LO, but not by adding the COX-specific inhibitor ␮ that enhancement of prostate tumor cell invasion by 12(S)- piroxicam. Interestingly, adding 0.1 M 12-HETE mimicked HETE involves selective activation of membrane-associated the stimulatory effect of linoleic acid on cell invasion, whereas PKC␣. Furthermore, the ability of PKC inhibitor calphostin C PGE2 and 5-HETE had no effect. Collectively, these data to block the 12-HETE-stimulated release of cathepsin B lends support the concept that enhanced 12-HETE, not PG, is in- credence to the observation that 12(S)-HETE acts via activation volved in the etiology of breast cancer cell metastasis. of PKC (7, 88). Conflicting reports on the relative importance of LO and Among several possible mechanisms by which LO inhi- COX in breast cancer have been published. For example, some bition may reduce prostate PC-3 cell proliferation is by altering investigators found that COX inhibitors such as indomethacin the concentration of second messengers needed for continued and flurbiprofen suppress mammary tumor development in rodent models of mammary carcinogenesis (107–109); other cell growth by shunting other arachidonic acid metabolites into studies conducted with these agents, particularly indomethacin, alternate pathways linked to signal transduction mechanisms yielded inconsistent results (110) or reported no correlatable (89, 90). For example, agents that inhibit 12-LO and block effect of COX inhibition to tumor growth (111). Consistent 12-HETE production may result in widespread interference in with these findings, in vitro studies have not conclusively signal transduction by preventing PKC activation (91, 92). LO associated COX inhibition with reduced mammary tumor cell inhibition may further affect the expression of proto-oncogenes growth (106, 112, 113). The LO inhibitors such as NDGA or their products, including EGF, FGF, TGF-␣ and ␤,N-and (0.1% diet; Ref. 114) and esculetin (0.03% diet; Ref. 115–117) K-ras,c-myc, int-2, IGF, and the retinoblastoma gene, also inhibit rat mammary tumor development induced in vivo by directly or indirectly associated with normal or transformed MNU or DMBA, lending credence to the hypothesis that LO prostate epithelial cell growth (93, 94). Whether inhibitors of products are important in mammary tumor development. COX- LO biosynthesis can influence expression of these factors, specific inhibitors produced mixed results in these studies. For however, has not yet been determined. example, the relatively selective COX-2 inhibitor nabumetone Breast. Reports published over the past two decades support a (0.03% diet) inhibited MNU-induced mammary tumor inci- growth-regulatory role for fatty acid metabolites and particu- dence and multiplicity (105, 117), whereas the COX-1-specific larly for the arachidonic acid-derived eicosanoids in the etiol- inhibitor piroxicam (0.03% diet) did not inhibit DMBA- ogy of mammary carcinogenesis (95). Feeding studies con- induced tumors (116). ducted in rodent models of mammary tumorigenesis showed Additional support for the role of LO products in breast that diets rich in linoleic acid, n-6 polyunsaturated fatty acid, cancer development includes recently published data on the and arachidonic acid precursor, stimulate mammary tumor ability of 12-HETE to mediate the proliferative effects of es- growth induced by either MNU or DMBA (96–99). Con- trogen and linoleic acid in a human breast cancer cell line (118). versely, dietary supplementation with n-3 polyunsaturated fatty In this study, MCF-7 breast cancer cells, estrogen dependent acid, particularly fish oils, retarded mammary tumor growth and unresponsive to growth stimulation with linoleic acid, were and metastasis in a variety of animal tumor models (100). transfected with 12-LO cDNA and grew in the absence of Studies by Abou-El-Ela et al. (101) using the DMBA mammary estrogen, showing reduced expression of estrogen receptor gland tumor model found that mammary tissue of rats fed 20% mRNA and protein compared with the parental cell line. More- menhaden oil produced lower levels of LTB4 and PGE2 com- over, 12-LO-transfected cells grew more rapidly than the pa- pared with groups receiving 20% corn oil or primrose oil, rental cells (36.2 Ϯ 3.0 ϫ 104 versus 12.4 Ϯ 1.1 ϫ 104) when supporting the theory that PGs and LTs may be involved in cultured in media containing linoleic acid. Injection of 12-LO- mammary carcinogenesis. transfected MCF-7 cells into mammary fat pads of ovariecto-

mized mice produced small solid tumors in 100% of estrogen- limited capacity to synthesize LTs. The low recovery of LO supplemented mice and 43% of unsupplemented mice. enzyme transcripts is consistent with the theory that LTs serve However, additional studies will be needed to explain the as intracellular messengers rather than inflammatory mediators amplified response to estrogen in cells overexpressing 12-LO in this tissue. More recently, platelet-type 12-LO mRNA has and to further determine whether 12-LO transfection increases been recovered from a human colon carcinoma cell line (2); the metastatic potential of these cells. treatment of these cells with 12(S)-HETE resulted in up-regu- More recently, using reverse transcription-PCR and North- lation of 12-LO mRNA and protein (133). Collectively, these ern blot analysis, identification and characterization of a 15-LO data strongly suggest that LO metabolism may play a role in identical to the 15-LO gene product present in human pulmo- colon tumor proliferation. nary tissue has been reported in BT-20 human breast carcinoma Skin. Considerable evidence suggests that LOs are involved in cells (119). BT-20 cells overexpress both the EGF receptor and epidermal tumor development. Compared with normal epider- the homologous erbB-2 (neu) oncogene product, two factors mis, large quantities of 12(S)-HETE (50–60-fold greater) were identified as possible adverse prognostic indicators in human found in papillomas and carcinomas induced by DMBA and breast cancer (120, 121). Adding indomethacin to these cells TPA in a mouse skin tumor model (134). In the same study, had no effect on EGF and TGF-␣-stimulated DNA synthesis, 12-LO enzyme activity was elevated 6-fold in papillomas and nor did it block the LO-mediated metabolism of linoleic acid 3-fold in carcinomas compared with normal tissue. Moreover, into 13-HODE. NDGA, on the contrary, inhibited production of expression of platelet-type 12-LO has been confirmed in both 13-HODE and attenuated TGF-␣-induced DNA synthesis, sup- normal human epidermis (135) and human epidermoid A431 porting a role for LO metabolites in regulating the EGF receptor carcinoma cells (66). 12(S)-HETE overproduction in papillo- signaling pathway. Thus, increased production of 13-HODE as mas may be a mechanism for progression to malignant carci- a result of high dietary levels of linoleic acid may up-regulate noma. Recent studies found that EGF and TPA up-regulate and amplify the EGF mitogenic signaling pathway, resulting in expression of 12-LO mRNA in the human A431 cell line (35, enhanced cell growth in cancerous breast tissue. On the other 66, 136). Overexpression of Ha-ras in these cells increased the hand, reducing 13-HODE via LO inhibition may potentially transcription of 12-LO in a dose- and time-dependent manner inhibit the mitogenic response and block further proliferation of that correlated to the cellular expression of ras protein (137). breast cancer tissue. Although this study provides evidence that ras can activate Other in vitro studies postulated that LO metabolism may 12-LO gene transcription directly, it did not determine whether be involved in modulating tumor cell adhesion. In one study agents that inhibit 12-LO would be effective in preventing conducted in the human breast carcinoma cell line MDA-MB- ras-mediated stimulation of intracellular signaling pathways. 435, exogenous NDGA dramatically inhibited adhesion to col- Other Sites. In squamous epithelial carcinomas of the head lagen IV induced by either A23187 or arachidonic acid, and neck, 12- and 15-HETE are major arachidonic acid metab- whereas indomethacin had no effect, implying that COX is not olites (138). Also, 12(S)-HETE is the predominant metabolic involved in this process (122). Consistent with these findings, product of metastatic B16 melanoma cells (139). Additionally, previous reports showed that linoleic acid potentiates the met- excess LT production, specifically LTC4, has been documented astatic potential of this cell line both in vitro and in vivo (123, in cells from patients with both acute and chronic leukemias 124) and also stimulates cell adhesion to fibronectin in another (140–142). Adding 5-LO inhibitors SC 41661A (Searle) and human breast cancer cell line (125). A63162 (Abbott) to these cells reduced DNA labeling and Colon. Besides overwhelming data linking PGs to the etiology decreased cell numbers within 72 h (140, 143). Likewise, of colon carcinogenesis (126), several recent lines of evidence growth inhibition with other LO inhibitors, including piriprost, suggest that LO products may also be involved in this process. NDGA, and BW755C, has been demonstrated in several ma- Specifically, in vitro studies conducted in two colon cancer lignant human hematopoietic cell lines; the COX inhibitor cells lines (HT-29 and HCT-15) reported time- and dose-de- indomethacin lacked a suppressive effect (47, 144). These data pendent stimulation of cell proliferation by LTB4 and 12(R)- imply that LO products are essential for the in vitro growth of HETE, a P450-derived product (127). In the same study, malignant hematopoietic cells.

SC41930, a competitive LTB4 antagonist, inhibited LTB4-induced growth stimulation in HT-29 cells. Similar inhibition occurred in murine colon adenocarcinoma cell lines MAC16, Pharmacological Agents MAC13, and MAC26 treated with other 5-LO inhibitors, in- As suggested in the discussions above, two general classes of cluding BWA4C and BWB70C at micromolar concentrations agents inhibit LO pathways. First are the (usually) specific Ͻ ␮ ␮ (IC50, 10 M), whereas Zileuton (IC50,40 M) was less inhibitors of 5-LO and FLAP, and (usually) nonspecific inhib- effective (128). The same study further analyzed in vivo activ- itors of 12-LO; second are LT receptor antagonists. Although ities of these agents in male NMRI mice transplanted with the latter class of agents has high potential to treat asthma and fragments of MAC26 or MAC16 colon tumors. At 25 mg/kg other diseases where drug effects are clearly mediated by LT body weight, BWA4C was the most effective inhibitor, signif- receptors, inhibitors of specific enzymes in the LO pathway icantly decreasing both growth rate and tumor volume after may be better candidates for chemopreventive intervention. 8–13 days of treatment. Unlike receptor antagonism, inhibition of these enzymes results Additional evidence supporting LT biosynthesis in colon directly in reducing the production of fatty acid metabolites cancer development stems from biochemical and genetic stud- with concomitant damping of the associated inflammatory, ies. The ability of colonic epithelial cell lines to synthesize proliferative and metastatic activities that contribute to carci- some LTs, including LTB4 and LTA4, has been confirmed in nogenesis. In the following paragraphs, both enzyme and re- human HT-29 (129, 130) and CaCo-2 cells (131) and in rat ceptor inhibitors are described. However, because they are colonic crypt epithelial cells (132). Northern blot analysis of commercially available and, hence, well characterized, and total RNA revealed low levels of mRNA transcripts for both because they have aerosol formulations and possible antipro- 5-LO and FLAP (129), suggesting that intestinal cells have a liferative activity, the receptor antagonists may also have che-

Table 2 LO inhibitory agents

LO and other Status LO inhibitory Antiproliferative activity Agent (developer) Target inhibitory activities (indication) activity (in vitro,IC50) (in vitro,IC50) (in vivo,ED50) ␮ Zileuton Leutrol Zyflo 5-LO FDA approved 12/96, RBL-1 (0.5 M) and rat Rat pleural effusion LTB4 Murine colon a (Abbott) launched in the United PMNL (0.3 ␮M) 5-HETE inhibition 1–3 mg/kg p.o. adenocarcinoma cells States January 1997 synthesis (146) (228); 70% decrease in ex (43–58 ␮M) (128) ␮ (asthma) Human whole blood (0.9 M) vivo whole-blood LTB4 ␮ and PMNL (0.4 M) LTB4 synthesis in humans given (146) 600 mg q.i.d. p.o. ϫ 14 days (229) Plasma half-life 2.5–3 h p.o. (230)

ABT-761 (Abbott) 5-LO Phase III (asthma) LTB4 inhibition: RBL-1, and A single 200-mg p.o. dose Not reported 12-LO human PMNL (23 nM), gave 95% inhibition of human whole blood (150 LTB4 in human ex vivo nM) (149) blood for up to 18 h (149) Human whole blood 12- Human plasma half-life 200 HETE synthesis (11 ␮M) mg p.o. 15 (149) (149) AA-861 (Takeda) 5-LO Discontinued Phase II Guinea pig peritoneal PMNL 30 mg/kg i.p. inhibited TPA- Human leukemia cells (6–20 12-LO (asthma, allergy) 5-LO (0.8 ␮M) (231); induced ODC activity in ␮M) (153) Mouse epidermal 12-LO mouse liver, spleen, and Lung cancer cells stimulated (1.9 ␮M) (150, 151) kidney (152); TPA- with IGF and GRP (5–10 induced neutrophil ␮M) (71) infiltration blocked at 10 ␮mol/mouse (232)

ZD2138 (Zeneca) 5-LO Discontinued Phase II LTB4 inhibition in human Rat inflammatory exudate Not reported (asthma) (0.024 ␮M), rat (0.033 model (0.3 mg/kg p.o.) ␮M), and dog (0.02 ␮M) (233) blood (233) At 350 mg p.o., complete inhibition of LTB4 in ex vivo human whole blood; human plasma half-life 12–16 h (234) MK-886 (Merck) FLAP Discontinued Phase I Human and rat neutrophil LT Rat pleurisy model (0.2–2.3 DNA synthesis inhibition in (asthma) biosynthesis (3–5 nM), mg/kg p.o.), rat paw acute myelogenous intact human PMNs edema (0.8 mg/kg), rat leukemia cells at 100 nM (2.5 nM) (157) bronchospasm assay (235) (0.036 mg/kg) (157); 750 Growth inhibition of chronic mg p.o. produced 50% myelogenous leukemia inhibition in ex vivo (10–20 ␮M) (141) and human whole-blood LTB4 lung cancer cells (5–10 (159) ␮M) (71) MK-0591 (Merck) FLAP Discontinued Phase I LT synthesis in human 750 mg p.o. daily reduced Not reported (asthma, ulcerative colitis) PMNLs (3 nM) and rat bronchoconstriction and neutrophils (6 nM); decreased LT synthesis by leukocyte FLAP binding 98% in human ex vivo assay (23 nM) (236) stimulated whole blood (237)

BAY-X1005 (Bayer) FLAP Discontinued Phase II Human (0.22 ␮M) and rat Arachidonic ear edema (49 Not reported (asthma, cardiac failure) PMNLs (0.026 ␮M); mg/mouse) (238) mouse macrophage (0.021 LTB inhibition in rat ex vivo ␮ 4 M) LTB4 synthesis (162) whole blood (11.8 mg/kg p.o.) (162) Oral half-life at 50–750 mg 4–8 h (239)

SC 41930 (Searle) LTB4 receptor Discontinued Phase II Human PMN LTB4-induced PMA-induced ear edema in Not reported (asthma, colitis) neutrophil degranulation rodents (4.2 ␮M/ear) (168) (1080 nM), human PMN Inhibits fMLP-induced chemotaxis assay (832 nM) superoxide release (167) (168)

SC 53228 (Searle) LTB4 receptor Phase I (asthma, ulcerative Human PMN LTB4 receptor LTB4-induced neutrophil Not reported colitis) binding (1.3 nM), LTB4- chemotaxis in guinea pig induced neutrophil skin (70 ␮g/kg body chemotaxis (32 nM) (168) weight); guinea pig p.o. half-life 9 h (240)

Table 2 Continued

LO and other Status LO inhibitory Antiproliferative activity Agent (developer) Target inhibitory activities (indication) activity (in vitro,IC50) (in vitro,IC50) (in vivo,ED50)

Ultair Pranlukast ONO-1078 LTD4 receptor Approved and launched in 26-fold shift in LTD4- Not reported (SmithKline Beecham/Ono Japan 1995 (asthma, induced Pharmaceuticals) allergy, pruritus); Phase III bronchoconstriction (asthma) and Phase I response curve at 450 mg (pediatric asthma) in p.o. twice daily (241) United Kingdom and Significant improvement in United States lung function at 225–450 mg twice daily in chronic asthmatics (241, 242) ϭ Zafirlukast Accolate LTD4 receptor Approved for marketing LTD4 binding (K1 0.3 nM) A single 40-mg oral dose in Not reported (Zeneca) September 1996 in United (170) health volunteers produced States (asthma) a 117-fold shift in the LTD4-induced bronchoconstriction response curve (243) a PMNL, polymorphonuclear lymphocyte.

mopreventive potential, particularly in lung, where topical ap- MAC26; Ref. 128). All three compounds effectively reduced plication of such formulations is feasible. cell proliferation in all cell lines tested; Zileuton showed 10- ␮ Initial 5-LO inhibitors were nonspecific antioxidants that fold higher IC50s (43–58 M) than the other compounds (2–5 lacked oral bioavailability, produced adverse physiological ef- ␮M). Because of toxicity demonstrated by both BWA4C and fects, or interfered with biological processes. Early 5-LO in- BWB70, further clinical development of these agents has been hibitory compounds, such as phenidone, and various analogues terminated (147). Additional testing is needed to fully evaluate including BW755C, A53612, and ICI 207968, induced methe- the antiproliferative action of Zileuton and to determine its moglobinemia, precluding their further clinical development potential as a chemopreventive agent. (145). Identifying natural products with LO inhibitory activity, Second Generation N-Hydroxyurea Compounds. The pri- such as caffeic acid, NDGA, and vignafuran, inspired pharma- mary drawbacks of Zileuton are its relatively short activity ceutical researchers to develop other compounds and analogues duration and high effective dose, both likely resulting from of greater potency and enzyme specificity. These efforts led to extensive glucuronidation and subsequent rapid excretion. The development of specific 5-LO inhibitors, FLAP inhibitors, pep- search for similar compounds with greater potency and reduced tidyl LT receptor antagonists, and LTB4 receptor antagonists glucuronidation rate led to the discovery of a number of struc- (Table 2 and Figs. 1-5). Experimental agents demonstrating turally different moieties, including the (R)-1-methoxypropynyl 12-LO inhibitory activity (Table 3) are shown in Fig. 6. The series represented by Abbott’s A78773 and A79175 (ABT- following discussion addresses each class of compounds and 175). A78773 proved to be more potent than Zileuton both in includes some agents that have undergone clinical evaluation. vitro and in vivo (148). A78773 was ϳ30-fold more potent than Zileuton in the ionophore-stimulated neutrophil assay. Ex vivo 5-LO Inhibitors evaluation of A78773 after a single oral dose of 0.5 mg/kg body First Generation N-Hydroxyurea Derivatives. Zileuton weight revealed complete inhibition of LTB4 production (95%) [Leutrol, N-(1-benzo(b)-thien-2yl) ethyl-N-hydroxyurea], a for up to 5 h and 70% inhibition for 12 h. At the same dose specific 5-LO inhibitor of the N-hydroxyurea series developed level, Zileuton showed 70% inhibition for 2 h but steadily by Abbott, represents the first p.o. active LT inhibitor to show declined thereafter (148). The antiproliferative activity of clinical efficacy in humans (145). Zileuton reportedly inhibits A78773 has not been determined. ϩ 5-LO via iron chelation but is devoid of 12- and 15-LO inhib- A79175, the (R ) racemate of A78773, exhibited similar itory activity (146). After extensive clinical evaluation, Zileu- potency to A78773 but showed greater resistance to glucu- ton received FDA approval in December 1996 for treating ronidation. A79175 entered Phase I clinical trials but was bronchial asthma in patients 12 years and older and was suspended after the discovery of synthetic intermediates of the launched in the United States in January 1997. At oral doses of ((4-fluoro-phenyl)methyl)-2-thienyl series represented by 600 mg four times daily, Zileuton produces moderate airway A85761 (ABT-761), which showed greater stability. In a Phase function improvement in asthmatics within 30 min. An ex- I study of ABT-761, a single oral dose of 200 mg produced a tended release formulation (Zyflo) with reduced twice-daily plasma half-life of 15 h with plasma levels of 1 ␮g/ml for up to dosing frequency is also available. In addition to asthma, Zileu- 72 h after dosing (149). The extended duration of action dem- ton has also been evaluated to treat ulcerative colitis. However, onstrated by ABT-761 may be therapeutically beneficial in work on this indication was halted in 1993 after a Phase III chemoprevention trials where sustained 5-LO inhibition is de- clinical trial that found that Zileuton, although effective, had no sirable. significant advantage over other conventional therapies. Redox Inhibitors. One of the most widely studied redox in- The antiproliferative properties of Zileuton have not yet hibitors is docebenone or 2,3,5-trimethyl-6-(12-hydroxy-5,10- been investigated extensively. One study compared the growth- dodecadiynyl)-1,4-benzoquinone (AA-861), a lipophilic qui- suppressive effects of Zileuton and two hydroxamate inhibitors, none structurally resembling coenzyme Q developed by Takeda BWA4C and BWB70C (Wellcome) in three different murine Chemical Industries, Ltd. (Osaka, Japan). AA-861 is a potent colon adenocarcinoma cell lines (MAC16, MAC13, and competitive inhibitor of 5-LO but has no effect on either 12-LO

Fig. 3. FLAP inhibitors.

Non-Redox Inhibitors. ZD2138 by Zeneca, a selective, p.o.- active 5-LO inhibitor of the methoxytetrahydropyran series, is devoid of redox and iron ligand-binding properties (156). De- spite its promising anti-inflammatory profile, Phase II clinical trials carried out in asthmatics had mixed results (145), halting further clinical development of this compound. Whether ZD2138 exerts antiproliferative activity remains to be determined. Fig. 2. 5-LO inhibitors. FLAP Inhibitors, Indole Series. Extensive screening of indole compounds derived from COX inhibitors indomethacin and sulindac led to development of MK-886 by Merck (157), or COX at concentrations Ͻ10 ␮M. In epidermal homogenates the first FLAP inhibitor to reach clinical evaluation. MK-886 is of CD-1 mice, AA-861 is a potent inhibitor of epidermal 12-LO believed to work by binding to an arachidonic acid binding site ␮ on FLAP, facilitating the transfer of the substrate to 5-LO (IC50 1.9 M; Refs. 150 and 151). In addition to its anti-inflammatory properties, AA-861 (158). Asthmatics administered 750 mg of MK-886 p.o. (15 ␮M/mouse) strongly suppressed skin tumor formation in- showed only 50% inhibition of LTB4 in ex vivo-stimulated duced by DMBA and TPA (10 nmol/mouse) and produced whole blood and in urinary LTE4 levels (159). On the basis of dose-dependent inhibition of TPA-stimulated ODC activity in these data, further clinical development of MK-886 was dis- the mouse at concentrations of 1–30 ␮M (151). Additional in continued. However, antiproliferative effects of MK-886 were vivo studies further showed that at 30 mg/kg body weight observed recently at micromolar concentrations in malignant administered i.p., AA-861 prevented TPA-induced increase in cells from patients with chronic myelogenous leukemia (141) ODC activity in liver, spleen, and kidneys of CD-1 mice (152). and in human lung cancer cells (71). On the basis of these Tsukada et al. (153) first reported the antiproliferative preliminary findings, MK-886 may have some therapeutic po- activity of AA-861 in a study of three human leukemia cell tential as a chemopreventive agent. lines, K562, Molt4B, and HL60, and the human cervical cell MK0591 represents a novel 2-indolealkanoic acid deriv- line HeLa. In this study, AA-861 (6.7 and 20 ␮M) markedly ative and second-generation FLAP inhibitor developed by reduced the growth of leukemia cells but had no effect on Merck (160). Like MK-886, MK0591 blocks 5-LO activity by cervical HeLa cells. Similarly, at 5–50 ␮M, AA-861 produced binding to FLAP, thereby preventing 5-LO translocation and dose-dependent growth inhibition in murine mastocytoma cells activation. Despite its promising biochemical profile, develop- (P815; Ref. 154). More recently, AA-861 at concentrations of ment of MK0591 was discontinued after results from further ϳ5–10 ␮M significantly reduced the growth and proliferation of clinical testing were below anticipated values. human small cell lung cancer (NCI-H209, H345, H82, and FLAP Inhibitors, Quinoline Series. Optimization of the N417) and non-small cell lung cancer (NCI-H1155, H23) cell 2-quinolylmethyloxy phenyl residue of Revlon’s REV 5901 led lines stimulated by either of two autocrine growth factors, IGF to BAY-X1005, a potent, p.o. active inhibitor of 5-LO devel- and GRP (71). Profiles of arachidonic acid metabolism in oped by Bayer AG to treat asthma (161, 162). BAY-X1005 AA-861-treated cells showed consistent inhibition of 5-HETE, reportedly lacks 12-LO or COX inhibitory activity and is de-

LTD4, and arachidonic acid metabolism. Another study in- void of antioxidant activity (163). The binding of BAY-X1005 duced apoptosis in rat Walker (W256) carcinosarcoma cells to FLAP has been reported to directly correlate with the degree Ն ␮ with AA-861 at concentrations of 20 M (155). of LTB4 inhibition (164). Development of BAY-X1005 for

Fig. 5. Peptidyl LT antagonists.

ICI-204,219; Zeneca), an LTD4 receptor antagonist, was cleared in September 1996 for marketing as an asthma treat- Fig. 4. LTB4 receptor antagonists. ment in the United States. Accolate has demonstrated potent activity both in vitro and in vivo (170). Upon receiving FDA approval, the Pulmonary-Allergy Drug Advisory Committee treating asthma was discontinued after a Phase III clinical has declared Accolate safe and effective in patients older than evaluation. The antiproliferative capacity of BAY-X1005 has 12 years of age with mild to moderate asthma (171). The not been reported in the literature. chemopreventive efficacy of this agent, however, has not been

LTB4 Receptor Antagonists. SC 41930, a potent first gener- investigated. ation LTB4 receptor antagonist developed by Searle (Mon- Esculetin and Other Experimental 12-LO Inhibitors (Non- santo; Refs. 165 and 166) has demonstrated potency in a variety specific). Esculetin, a coumarin derivative extracted from the of inflammatory models. However, the discovery that SC bark of Aesculus hippocastanum, is a well-known competitive 41930 inhibits f-MLP-induced superoxide release (167) inhibitor of both the LO and COX metabolic pathways (172– prompted further research to develop agents with greater po- 175). At concentrations of 0.1–1 ␮M, esculetin exerts LO in- tency and selectivity. hibitory activity; levels Ͼ10 ␮M are required for COX inhibi- Second-generation agents derived from structural ana- tion (172, 175). Acute toxicity testing of esculetin in the mouse logues of SC 41930 include monomethyl amide SC 53228 (168, produced an LD50 of 1450 mg/kg body weight i.p. and 2000 169) and thiazole analogue SC 50605 (7-(3-(2-(cyclopropyl- mg/kg when given p.o. (176). methyl)-3-methoxy-4-(thiazol-4-yl)phenoxy)propoxy)-3,4-di- The antiproliferative action of esculetin has been demon- hydro-8-propyl-2H-1-benzopyran-2-carboxylic acid) (167). strated in several in vitro models. At concentrations of 3–30 Potent antagonists of LTB receptors both demonstrate sub- ␮ 4 g/ml, it significantly reduced LTB4 secretion and produced stantially improved pharmacological profiles compared with growth suppression in the MDA-MB-231 human breast cancer SC 41930. SC 50605 and SC 53228 have been selected for cell line (177). Likewise, esculetin at 20 ␮M completely sup- further clinical evaluation. pressed production of 12-HETE in estrogen-independent hu-

LTD4 Receptor Antagonists. Ultair (Pranlukast, ONO-1078, man MDA-MB-435 breast cancer cells stimulated with linoleic SB205312) or N-(4-oxo-2-(1H-tetrazol-5-yl)-4H-1-benzopy- acid (104). In the same study, 2 or 20 ␮M of esculetin com- ran-8-yl)-4-(4-phenylbutoxy)-benzamide, licensed from Ono pletely blocked the invasiveness of cells stimulated by linoleic

Pharmaceuticals by Smithkline Beecham, is the first LTD4 acid while completely suppressing type IV collagenase (met- antagonist to be introduced in the world, having been approved alloproteinase-9) mRNA expression. Similar growth-suppres- to treat asthma in Japan in 1995; it is now in Phase III clinical sive effects of esculetin have been reported in human T-lymph- Ϯ ␮ trials in the United Kingdom and United States. Whether this oid leukemia cells (IC50, 3.6 0.3 M; Ref. 178) and in Ϯ ␮ pharmacological agent or other LTD4 antagonists exert anti- vascular smooth muscle cells (IC50, 10.9 2.8 M) stimulated proliferative activity has not been determined. with 5% FCS (179). Zafirlukast or cyclopentyl 3-(2-methoxy-4-((o-tolylsulfo- In vivo studies have further shown that esculetin signifi- nyl)carbamoyl)benzyl)-1-methylindole-5-carbamate (Accolate, cantly inhibits the development of mammary tumors induced

Table 3 Experimental compounds demonstrating 12-LO inhibitory activity

Compound Activity (in vitro) Antiproliferative activity Chemopreventive activities

Esculetin (coumarin derivative) Inhibits 5-LO at 0.1–1 Decreased LTB4 and produced growth suppression 0.03% in diet reduced incidence of DMBA-induced ␮M, COX at 10 ␮M in human T-cell leukemia (177), vascular mammary tumors in SD rats (115, 116) (172, 175); smooth muscle (179), and breast cancer cells Pretreatment with 50 ␮M reduced metastasis and mastocytoma 12-LO (177) at 3–30 ␮M invasiveness of melanoma cells injected into ϭ ␮ IC50 2.5 M (173) Antiinflammatory and analgesic activity reported syngeneic mice (180) (176)

Baicalein (flavonoid) Rat platelet 12-LO IC50 Reduced DNA synthesis and produced growth Induced dose-dependent apoptosis in vitro in rat ϭ 0.12 ␮M (181), rat inhibition in human liver cells (183), breast carcinosarcoma cells at 5–100 ␮M (155) ␣ PMN 5-LO (IC50, cancer (187), and T-lymphoid leukemia (178) Reduced PDGF-A and TGF- mRNA in leukemia 9.5 ␮M) (182) Antiinflammatory activity reported in arthritis cells (178) (182) and other models (244) BHPP (hydroxamic acid) Inhibits porcine leukocyte Growth inhibition in rat Walker carcinosarcoma 40–50% reduction in lung colony formation in and Lewis lung cells at 0.01–100 ␮M (190) mice given 50 mg/kg body weight p.o. or i.p. carcinoma 12-LO at and injected with metastatic HM340 cells (2) micromolar levels (189) and rat leukocyte 5-LO (188)

by DMBA in female Sprague Dawley rats fed either a high-fat (20% soybean oil) or low-fat (0.5% soybean oil) diet (115, 116). Rats administered diets containing 0.03% esculetin showed significant reduction in mammary tumor incidence, tumor growth, and cell kinetics in both the high- and low-fat dietary groups. More recently, esculetin has been effective in reducing the invasive and metastatic activity of malignant tumor cells (180). Murine melanoma cells pretreated with 50 ␮M esculetin and injected into syngeneic mice produced significantly lower numbers of melanoma colonies on the lung surface and fewer tumor metastases. Thus, esculetin may be an effective chemopreventive agent on the basis of these data; however, additional studies will be needed to assess its efficacy in other tumor models. Baicalein, a low molecular weight flavonoid isolated from Scutellaria baicalensis Georgy roots, is a key component of Japanese herbal medicine Sho-saiko-to, commonly used to treat chronic liver diseases in Japan. Early studies conducted in rat platelets showed that nanomolar concentrations of baicalein exert potent 12-LO inhibitory activity, whereas much higher levels are required for COX inhibition (181). In rat PMNs,

baicalein also reportedly blocks 5-LO and production of LTC4 (182). The antiproliferative effects of baicalein have been reported in several in vitro models. Mooto et al. (183) showed ␮ that baicalein (IC50,50 g/ml) reduced DNA synthesis and inhibited growth in two human hepatoma cell lines (phospholipase C/PRF/5 and Hep-G2). Similar growth-suppressive effects of baicalein have been reported by other investigators in various hepatocellular cancer cell lines, particularly HuH-7 cells (184–186). Likewise, treating human breast cancer cells (MCF-7) with baicalen at microgram levels produced potent Fig. 6. 12-LO inhibitors. ␮ antiproliferative activity (IC50, 5.3 g/ml; Ref. 187). In human T-lymphoid leukemia cells (CEM) stimulated with 10% FCS,

baicalein dose dependently reduced cell proliferation (IC50, in vivo, however, remains to be determined. Nevertheless, these 4.7 Ϯ 0.5 ␮M), exhibiting maximal inhibition (91.5 Ϯ 1.4%) at initial data suggest that baicalein may be an effective chemo- Ϫ4 10 M (178). In the same study, baicalein reduced the expres- preventive agent. sion of PDGF-A mRNA, and to a lesser degree also affected Another select 12-LO inhibitor is BHPP, one of a series of ␤ TGF- 1 mRNA expression, suggesting that baicalein may exert hydroxamic acids originally developed by Rorer that was found its antiproliferative action via inhibition of growth factor-me- to exert 5-LO inhibitory activity in rat leukocytes (188). Ad- diated signaling pathways. Additional studies found that 5–100 ditional studies demonstrated 12-LO inhibitory activity in ␮M concentrations of baicalein in rat Walker (W256) carcino- Lewis lung carcinoma cells and porcine leukocytes (189) and in sarcoma cells induced apoptosis in a dose-dependent manner murine B16a melanoma cells (7). (155). Whether baicalein exerts similar antiproliferative activity The antiproliferative action of BHPP has recently been

Table 4 Representative Leukotriene Inhibitors/Antagonists Not Included in Text

Agent (developer) Target Indication Clinical status

CGS-25019C (Novartis/Ciba-Geigy) LTB4 antagonist Asthma, bronchitis, rheumatoid arthritis Phase II ONO-4057 (Ono Pharmaceutical) LTB4 antagonist Psoriasis, ulcerative colitis, Behcet’s disease, Phase II inflammatory bowel disease

SB-201993 (SmithKline Beecham) LTB4 antagonist Inflammation, psoriasis Discontinued Phase II SB-209247 (SmithKline Beecham) LTB4 antagonist Psoriasis, eczema Phase II SC 52798 (Searle) LTB4 antagonist Inflammation, psoriasis, ulcerative colitis Discontinued VML-295/LY29311 (Vanguard/Eli Lilly) LTB4 antagonist Asthma, inflammation, inflammatory bowel Phase II disease, psoriasis, rheumatoid arthritis, ulcerative colitis WY-50295 (Wyeth-Ayerst) 5-LO/LT antagonist Arthritis, asthma, psoriasis, inflammation Discontinued Phase II Ն Montelukast/MK-476 (Merck Frosst) LTD4 antagonist Asthma (patients 6 years of age) New Drug Application filed first quarter 1997, approved in Finland September 1997

BAY-X7195 (Bayer) LTD4 antagonist Asthma Phase II Iralukast/CGP-45715A (Novartis/Ciba Geigy) LTD4, LTE4 antagonist Asthma Phase II

reported in rat Walker (W256) carcinosarcoma cells. At con- detection. In a similar fashion, 12-LO can be assessed in lysates centrations of 0.01–100 ␮M, BHPP demonstrated dose-depen- of human platelets or in partially purifed preparations available dent growth inhibition; at 10 ␮M, it produced DNA fragmen- through commercial sources. Likewise, purified forms of rabbit tation and induced apoptosis in treated cells (190). BHPP has reticulocyte or soybean 15-LO can be obtained through local been studied in vitro to assess the role of 12-LO and 12(S)- suppliers. HETE production in tumor cell matrix interactions and analyze In addition to these sources, methods have been developed integrin ␣IIb␤3 expression and in vivo in an experimental to purify 5-LO from human leukocytes using ATP-agarose model of tumor metastasis (2). In these studies, murine B16a affinity chromatography (191–193). According to this protocol, HM340 cells of high metastatic potential were exposed to ϳ500 ␮g of protein can be recovered from 8 ϫ 108 cells. Ϫ5 Ϫ8 increasing concentrations of BHPP (10 –10 M). Cells Additionally, glycogen-induced rat peritoneal PMNs are an treated with BHPP showed decreased adhesion to fibronectin alternate source of 5-LO when cells are harvested and lysed, and subendothelial matrix and reduced surface expression of then centrifuged. The resulting supernatant is used to measure ␣IIb␤3. Oral and i.p. administration of BHPP (50 mg/kg body 5-LO activity as above. Using 105,000 ϫ g supernatant frac- weight) 30 min before tail vein injection of HM340 cells tion, the major arachidonic acid metabolites produced are LTB4 produced a 40–50% reduction in lung colony formation in and 5-HETE. syngeneic C57BL/6J mice. Additional testing will be needed to Once activity profiles are determined in cell-free assays, verify the potency of BHPP in models of chemoprevention. each agent is further evaluated in whole-cell models, further Representative LT inhibitory agents that have been clini- verifying LO biosynthesis and establishing the inhibitory effi- cally evaluated but not specifically addressed in this report are cacy of each agent. Examples of intact cell models used in listed in Table 4. These include WY50295 (Wyeth-Ayerst), assessing eicosanoid biosynthesis include human whole blood Montelukast or MK-476 (Merck), LY29311 (Lilly), CGS- or PMNs, washed platelets (12-LO), and rat peritoneal leuko- 25019C and Iralukast or CGP-45715A (Ciba Geigy/Novartis), cytes. In these experiments, cells are preincubated in the pres- ONO-4057 (Ono Pharmaceuticals), SB-210993 and SB-209247 ence and absence of varying concentrations of inhibitors, then (SmithKline Beecham), SC-53228 and SC-52798 (Searle), and stimulated with ionophore. LO metabolites are extracted and BAY-X7195 (Bayer). Because these agents have also demon- measured using either enzyme immunoassay or RIA or prela- strated LO inhibitory potency, their potential as chemopreven- beled with radiolabeled arachidonic acid before separation by tive agents cannot be ruled out. However, additional studies TLC or high-performance liquid chromatography. will be needed to verify the therapeutic utility of LO inhibitors in chemoprevention. Cell Proliferation and DNA Synthesis Assays Once inhibitory potency has been established in whole-cell Assessing LT Inhibitory Activity models, each agent is further subjected to a series of antipro- To assess potency and enzyme specificity, pharmacological liferative screens using established cell culture cancer assay profiles of each agent are established based on screening data systems. These assays should include representative human cell obtained from both cell-free assays and in vitro model systems. lines for breast, colon, prostate, and lung cancer. Experiments For this purpose, each compound is subjected to a series of determine LT or HETE-mediated growth stimulation and con- enzymatic screens to determine 5-, 12-, and 15-LO inhibitory centration-dependent inhibition of cell proliferation and DNA activities. 5-LO measurement is typically conducted in cell synthesis for each agent. Cell proliferation can be measured by lysates from rat (RBL-1) cells. According to this protocol, the colorimetric method of Mosmann (194) using tetrazolium RBL-1 cells are harvested and lysed by sonication and centri- salt 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bro- fuged, and the supernatant fraction was used as a source of the mide. Briefly, cells are plated at a uniform density and allowed enzyme (146). Activity (5-HETE production) is then measured to incubate for a given time period (usually several days) in the by either RIA or enzyme immunoassay. Alternately, activity presence or absence of inhibitors, then processed according to can be determined by using [14C]arachidonic acid as substrate, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide followed by extraction and separation via TLC or reverse-phase protocol. For DNA synthesis analysis, cells are plated at a high-performance liquid chromatography with on-line radiation uniform density, then exposed to [3H]thymidine and allowed to

incubate for 1–4 h in the presence and absence of inhibitors. References After incubation, the cells are washed, and residual label is 1. Honn, K. V., Tang, D. G., Gao, X., Butovich, I. A., Liu, B., Timar, J., and assessed by scintillation counting. Cell viability is determined Hagmann, W. 12-Lipoxygenases and 12(S)-HETE: role in cancer metastasis. in the presence of inhibitors to rule out any agent-induced toxic Cancer Metastasis Rev., 13: 365–396, 1994. effects by either trypan blue exclusion methodology or by the 2. Chen, Y. Q., Duniec, Z. M., Liu, B., Hagmann, W., Gao, X., Shimoji, K., Marnett, L. J., Johnson, C. R., and Honn, K. V. Endogenous 12(S)-HETE colorimetric method of Mosmann (194) described above. production by tumor cells and its role in metastasis. Cancer Res., 54: 1574–1579, In Vivo Testing. The chemopreventive efficacy of select in- 1994. hibitory agents can be further tested in well-established in vivo 3. Gao, X., Grignon, D. J., Chbihi, T., Zacharek, A., Chen, Y. Q., Sakr, W., carcinogen models (195). These include MNU- and DMBA- Porter, A. T., Crissman, J. D., Pontes, J. E., Powell, I. J., and Honn, K. V. Elevated 12-lipoxygenase mRNA expression correlates with advanced stage and poor induced mammary carcinogenesis assays conducted in female differentiation of human prostate cancer. Urology, 46: 227–237, 1995. Sprague Dawley rats (196–198). Both models require a single 4. Tang, D. G., and Honn, K. V. 12-Lipoxygenase, 12(S)-HETE, and cancer administration of the carcinogen; mammary tumors are pro- metastasis. Ann. NY Acad. Sci., 744: 199–215, 1994. duced within 65–80 days. The strain A/J mouse lung adenoma 5. Timar, J., Raso, E., Fazakas, Z. S., Silletti, S., Raz, A., and Honn, K. V. model is generally used to evaluate the chemopreventive ac- Multiple use of a signal transduction pathway in tumor cell invasion. Anticancer tivity of agents against lung cancer (199). It may be advanta- Res., 16: 3299–3306, 1996. geous to administer the LO inhibitors by aerosol inhalation to 6. Liu, B., Maher, R. J., Hannun, Y. A., Porter, A. T., and Honn, K. V. 12(S)-HETE enhancement of prostate tumor cell invasion: selective role of avert systemic toxicity (200). PKC␣. J. Natl. Cancer Inst., 86: 1145–1151, 1994. Potential inhibitors of colon carcinogenesis have been 7. Liu, B., Timar, J., Howlett, J., Diglio, C. A., and Honn, K. V. Lipoxygenase assessed using rat (F344) and mouse (CF1) species (201, 202). metabolites of arachidonic and linoleic acids modulate the adhesion of tumor cells For example, according to established protocols, a single dose to endothelium via regulation of protein kinase C. Cell Regul., 2: 1045–1055, of azoxymethane administered s.c. to male F344 rats causes 1991. colon adenoma and adenocarcinoma formation in about 70% of 8. Liu, Y-W., Chen, B-K., Chen, C-J., Arakawa, T., Yoshimoto, T., Yamamoto, S., and Chang, W-C. Epidermal growth factor enhances transcription of human treated animals by 40 weeks (202). Short-term colon tumor arachidonate 12-lipoxygenase in A431 cells. Biochim. Biophys. Acta, 1344: models include measurement of ACF in portions of rat colon 38–46, 1997. stained with methylene blue (203, 204). ACF, thought to be 9. Dethlefsen, S. M., Shepro, D., and D’Amore, P. A. Arachidonic acid metab- preneoplastic lesions that eventually give rise to colon tumors, olites in bFGF-, PDGF-, and serum-stimulated vascular cell growth. Exp. Cell. are used frequently as intermediate biomarkers of colon cancer Res., 212: 262–273, 1994. (205). Test agents are generally administered p.o., either before, 10. Schade, U. F., Ernst, M., Reinke, M., and Wolter, D. T. Lipoxygenase inhibitors suppress formation of tumor necrosis factor in vitro and in vivo. during, or after a single or multiple dose of azoxymethane. Biochem. Biophys. Res. Commun., 159: 748–754, 1989. Efficacy is evaluated as a reduction in the number of ACF after 11. Stenke, L., Mansour, M., Reizenstein, P., and Lindgren, J. A. Stimulation of histological analysis. human myelopoiesis by leukotrienes B4 and C4: interactions with granulocyte- Several models have been described for evaluating effects macrophage colony-stimulating factor. Blood, 81: 352–356, 1993. on prostate carcinogenesis. These include the Noble rat model 12. Denzlinger, C., Walther, J., Wilmanns, W., and Gerhartz, H. H. Interleukin-3 in which male rats are treated with testosterone and estradiol enhances the endogenous leukotriene production. Blood, 81: 2466–2468, 1993. (206, 207), and a second, more recent model developed by 13. Honn, K. V., Timar, J., Rozhin, J., Bazaz, R., Sameni, M., Ziegler, G., and Sloane, B. F. A lipoxygenase metabolite, 12-(S)-HETE, stimulates protein kinase Bosland, whereby Wistar rats are given cyproterone acetate, C-mediated release of cathepsin B from malignant cells. Exp. Cell Res., 214: MNU, and testosterone (208, 209). Evaluation of skin tumor 120–130, 1994. inhibition will be conducted according to a two-stage skin 14. Tang, D. G., Grossi, I. M., Chen, Y. Q., Diglio, C. A., and Honn, K. V. tumorigenesis protocol (210) in which DMBA and TPA induce 12(S)-HETE promotes tumor-cell adhesion by increasing surface expression of ␣ ␤ skin papillomas and squamous cell carcinomas (211, 212). V 3 integrins on endothelial cells. Int. J. Cancer, 54: 102–111, 1993. Before initiation with DMBA or after promotion with TPA, test 15. Chopra, H., Timar, J., Chen, Y. Q., Rong, X., Grossi, I. M., Fitzgerald, L. A., Taylor, J. D., and Honn, K. V. The lipoxygenase metabolite 12(S)-HETE induces agents are applied topically to the back of SENCAR or CD-1 a cytoskeleton-dependent increase in surface expression of integrin ␣IIb␤3on mice, which are highly susceptible to skin tumor induction. melanoma cells. Int. J. Cancer, 49: 774–786, 1991. Once the most appropriate studies are completed, activity 16. Ghosh, J., and Myers, C. E. Arachidonic acid stimulates prostate cancer cell profiles of the agents will be compared to identify compounds growth: critical role of 5-lipoxygenase. Biochem. Biophys. Res. Commun., 235: suitable for chemoprevention trials in human subjects. Note that 418–423, 1997. 17. Samuelsson, B., Dahlen, S-E., Lindgren, J. A., Rouzer, C. A., and Serhan, some test compounds have already demonstrated activity in C. N. Leukotrienes and lipoxins: structures, biosynthesis, and biological effects. lung and breast. Agents that can be obtained through commer- Science (Washington DC), 237: 1171–1176, 1987. cial or other reliable sources and for which pharmacological 18. Needleman, P., Turk, J., Jakschik, B. A., Morrison, A. R., and Lefkowith, and preclinical safety data already exist will be recommended J. B. Arachidonic acid metabolism. Annu. Rev. Biochem., 55: 69–102, 1986. initially for further safety evaluation and clinical testing. 19. Lewis, R. A., Austen, K. F., and Soberman, R. J. Leukotrienes and other Because LO inhibitors are antiasthmatics, conducting fu- products of the 5-lipoxygenase pathway. Biochemistry and relation to pathobi- ture chemoprevention studies and applications in the lung has a ology in human diseases. N. Engl. J. Med., 323: 645–655, 1990. high priority. Although approved pharmaceuticals in this class 20. Clark, M. A., Ozgur, L. E., Conway, T. M., Dispoto, J., Crooke, S. T., and Bomalaski, J. S. Cloning of a phospholipase A2-activating protein. Proc. Natl. are bioavailable p.o., as noted above, it could be beneficial to Acad. Sci. USA, 88: 5418–5422, 1991. explore the use of inhalant formulations, which would deliver 21. Piper, P. J. Leukotrienes. Potent mediators of airway constriction. Int. Arch. agent locally to the lung, potentially reducing toxicity and Allergy Immunol., 76: 43–48, 1985. allowing higher, more efficacious doses. The prostate is also a 22. Coleman, R. A., Eglen, R. M., Jones, R. L., Narumiya, S., Shimizu, T., Smith, cancer target of high interest, because LO inhibitors demon- W. L., Dahlen, S-E., Drazen, J. M., Gardiner, P. J., Jackson, W. T., Jones, T. R., strate a high rate of arachidonic acid metabolism and antipro- Krell, R. D., and Nicosia, S. Prostanoid and leukotriene receptors: a progress report from the IUPHAR working parties on classification and nomenclature. liferative activity in prostate cancer cells. If these agents prove Adv. Prostaglandin Thromboxane Leukotriene Res., 23: 283–285, 1995. to be low-toxicity inhibitors of oxidative fatty acid metabolism, 23. O’Byrne, P. M. Exercise-induced bronchoconstriction: elucidating the roles the breast will be a potential target for further study. of leukotrienes and prostaglandins. Pharmacotherapy, 17: 31S–38S, 1997.

24. Drazen, J. M., and Austen, K. F. Leukotrienes and airway responses. Am. 47. Snyder, D. S. Antiproliferative effects of lipoxygenase inhibitors on human Rev. Respir. Dis., 136: 985–998, 1987. leukemia cells. Adv. Prostaglandin Thromboxane Leukotriene Res., 21B: 921– 25. Funk, C. D. The molecular biology of mammalian lipoxygenases and the 924, 1991. quest for eicosanoid functions using lipoxygenase-deficient mice. Biochim. Bio- 48. Snyder, D. S., and Desforges, J. F. Lipoxygenase metabolites of arachidonic phys. Acta, 1304: 65–84, 1996. acid modulate hematopoiesis. Blood, 67: 1675–1679, 1986. 26. Ochi, K., Yoshimoto, T., Yamamoto, S., Taniguchi, K., and Miyamoto, T. 49. Miller, A. M., Weiner, R. S., and Ziboh, V. A. Evidence for the role of Arachidonate 5-lipoxygenase of guinea pig peritoneal polymorphonuclear leuko- leukotrienes C4 and D4 as essential intermediates in CSF-stimulated human cytes. J. Biol. Chem., 258: 5754–5758, 1983. myeloid colony formation. Exp. Hematol., 14: 760–765, 1986. 27. Rouzer, C. A., and Samuelsson, B. On the nature of the 5-lipoxygenase 50. Ziboh, V. A., Wong, T., Wu, M-C., and Yunis, A. A. Modulation of colony reaction in human leukocytes: enzyme purification and requirement for multiple stimulating factor-induced murine myeloid colony formation by S-peptido-li- stimulatory factors. Proc. Natl. Acad. Sci. USA, 82: 6040–6044, 1985. poxygenase products. Cancer Res., 46: 600–603, 1986. 28. Rouzer, C. A., and Kargman, S. Translocation of 5-lipoxygenase to the 51. Yamamoto, S. Mammalian lipoxygenases: molecular structures and func- membrane in human leukocytes challenged with ionophore A23187. J. Biol. tions. Biochim. Biophys. Acta, 1128: 117–131, 1992. Chem., 263: 10980–10988, 1988. 52. Takahashi, Y., Ueda, N., and Yamamoto, S. Two immunologically and 29. Wood, J. W., Evans, J. F., Ethier, D., Scott, S., Vickers, P. J., Hearn, L., catalytically distinct arachidonate 12-lipoxygenases of bovine platelets and leu- Heibein, J. A., Charleson, S., and Singer, I. I. 5-Lipoxygenase and 5-lipoxyge- kocytes. Arch. Biochem. Biophys., 266: 613–621, 1988. nase-activating protein are localized in the nuclear envelope of activated human leukocytes. J. Exp. Med., 178: 1935–1946, 1993. 53. Walstra, P., Verhagen, J., Vermeer, M. A., Veldink, G. A., and Vliegenthart, J. F. G. Demonstration of a 12-lipoxygenase activity in bovine polymorphonu- 30. Peters-Golden, M., and McNish, R. W. Redistribution of 5-lipoxygenase and clear leukocytes. Biochim. Biophys. Acta, 921: 312–319, 1987. cytosolic phospholipase A2 to the nuclear fraction upon macrophage activation. Biochem. Biophys. Res. Commun., 196: 147–153, 1993. 54. Funk, C. D., Furci, L., and Fitzgerald, G. A. Molecular cloning, primary structure, and expression of the human platelet/erythroleukemia cell 12-lipoxy- 31. Wong, A., Hwang, S. M., Cook, M. N., Hogaboom, G. K., and Crooke, S. T. genase. Proc. Natl. Acad. Sci. USA, 87: 5638–5642, 1990. Interactions of 5-lipoxygenase with membranes: studies on the association of soluble enzyme with membranes and alterations in enzyme activity. Biochemis- 55. Hada, T., Ueda, N., Takahashi, Y., and Yamamoto, S. Catalytic properties of try, 27: 6763–6769, 1988. human platelet 12-lipoxygenase as compared with the enzymes of other origins. Biochim. Biophys. Acta, 1083: 89–93, 1991. 32. Brock, T. G., McNish, R. W., and Peters-Golden, M. Translocation and leukotriene synthetic capacity of nuclear 5-lipoxygenase in rat basophilic leuke- 56. De Marzo, N., Sloane, D. L., Dicharry, S., Highland, E., and Sigal, E. Cloning mia cells and alveolar macrophages. J. Biol. Chem., 270: 21652–21658, 1995. and expression of an airway epithelial 12-lipoxygenase. Am. J. Physiol., 262: L198–L207, 1992. 33. Woods, J. W., Coffey, M. J., Brock, T. G., Singer, I. I., and Peters-Golden, M. 5-Lipoxygenase is located in the euchromatin of the nucleus in resting human 57. Watanabe, T., Medina, J. F., Haeggstrom, J. Z., Radmark, O., and Samuels- alveolar macrophages and translocates to the nuclear envelope upon cell activa- son, B. Molecular cloning of a 12-lipoxygenase cDNA from rat brain. Eur. tion. J. Clin. Invest., 95: 2035–2046, 1995. J. Biochem., 212: 605–612, 1993. 34. Mahmud, I., Suzuki, T., Yamamoto, Y., Suzuki, H., Takahashi, Y., Yoshi- 58. Yamamoto, S., Suzuki, H., and Ueda, N. Arachidonate 12-lipoxygenases. moto, T., and Yamamoto, S. Induction of cyclooxygenase and suppression of Prog. Lipid Res., 36: 23–41, 1997. 12-lipoxygenase in human erythroleukemia cells upon phorbol ester-induced 59. Funk, C. D., Funk, L. B., FitzGerald, G. A., and Samuelsson, B. Character- differentiation. Biochim. Biophys. Acta, 1166: 211–216, 1993. ization of human 12-lipoxygenase genes. Proc. Natl. Acad. Sci. USA, 89: 3962– 35. Chang, W-C., Ning, C-C., Lin, M. T., and Huang, J-D. Epidermal growth 3966, 1992. factor enhances a microsomal 12-lipoxygenase activity in A431 cells. J. Biol. 60. Yoshimoto, T., and Yamamoto, S. Arachidonate 12-lipoxygenase. J. Lipid Chem., 267: 3657–3666, 1992. Mediat. Cell Signal., 12: 195–212, 1995. 36. Baba, A., Sakuma, S., Okamoto, H., Inoue, T., and Iwata, H. Calcium induces 61. Toh, H., Yokoyama, C., Tanabe, T., Yoshimoto, T., and Yamamoto, S. membrane translocation of 12-lipoxygenase in rat platelets. J. Biol. Chem., 264: Molecular evolution of cyclooxygenase and lipoxygenase. Prostaglandins, 44: 15790–15795, 1989. 291–315, 1992. 37. Hagmann, W., Kagawa, D., Renaud, C., and Honn, K. V. Activity and protein 62. Nguyen, T., Falgueyret, J-P., Abramovitz, M., and Riendeau, D. Evaluation distribution of 12-lipoxygenase in HEL cells: induction of membrane-association of the role of conserved his and met residues among lipoxygenases by site- by phorbol ester TPA, modulation of activity by glutathione and 13-HPODE, and ϩ directed mutagenesis of recombinant human 5-lipoxygenase. J. Biol. Chem., 266: Ca2 -dependent translocation to membranes. Prostaglandins, 46: 471–477, 1993. 22057–22062, 1991. 38. Nadel, J. A., Conrad, D. J., Ueki, I. F., Schuster, A., and Sigal, E. Immuno- 63. Zhang, Y. Y., Radmark, O., and Samuelsson, B. Mutagenesis of some cytochemical localization of arachidonate 15-lipoxygenase in erythrocytes, leu- conserved residues in human 5-lipoxygenase: effects on enzyme activity. Proc. kocytes, and airway cells. J. Clin. Invest., 87: 1139–1145, 1991. Natl. Acad. Sci. USA, 89: 485–489, 1992. 39. Narumiya, S., Salmon, J. A., Cottee, F. H., Weatherley, B. C., and Flower, R. J. Arachidonic acid 15-lipoxygenase from rabbit peritoneal polymorphonuclear 64. Schafer, A. I. Deficiency of platelet lipoxygenase activity in myeloprolifer- leukocytes. J. Biol. Chem., 256: 9583–9592, 1981. ative disorders. N. Engl. J. Med., 306: 381–386, 1982. 40. Atluru, D., and Goodwin, J. S. Leukotriene B4 causes proliferation of 65. Matsuda, S., Murakami, J., Yamamoto, Y., Konishi, Y., Yokoyama, C., interleukin 2-dependent T cells in the presence of suboptimal levels of interleukin Yoshimoto, T., Yamamoto, S., Mimura, Y., and Okuma, M. Decreased messenger 2. Cell. Immunol., 99: 444–452, 1986. RNA of arachidonate 12-lipoxygenase in platelets of patients with myeloproliferative disorders. Biochim. Biophys. Acta, 1180: 243–249, 1993. 41. Baud, L., Perez, J., Denis, M., and Ardaillou, R. Modulation of fibroblast proliferation by sulfidopeptide leukotrienes: effect of indomethacin. J. Immunol., 66. Chang, W-C., Liu, Y-W., Ning, C-C., Suzuki, H., Yoshimoto, T., and 138: 1190–1195, 1987. Yamamoto, S. Induction of arachidonate 12-lipoxygenase mRNA by epidermal growth factor in A431 cells. J. Biol. Chem., 268: 18734–18739, 1993. 42. Kragballe, K., Desjarlais, L., and Voorhees, J. J. Leukotrienes B4, C4 and D4 stimulate DNA synthesis in cultured human epidermal keratinocytes. Br. J. 67. Conrad, D. J., Kuhn, H., Mulkins, M., Highland, E., and Sigal, E. Specific Dermatol., 113: 43–52, 1985. inflammatory cytokines regulate the expression of human monocyte 15-lipoxygenase. Proc. Natl. Acad. Sci. USA, 89: 217–221, 1992. 43. Baud, L., Sraer, J., Perez, J., Nivez, M-P., and Ardaillou, R. Leukotriene C4 binds to human glomerular epithelial cells and promotes their proliferation in 68. Nassar, G. M., Morrow, J. D., Roberts, L. J., II, Lakkis, F. G., and Badr, K. F. vitro. J. Clin. Invest., 76: 374–377, 1985. Induction of 15-lipoxygenase by interleukin-13 in human blood monocytes. J. Biol. Chem., 269: 27631–27634, 1994. 44. Palmberg, L., Lindgren, J. A., Thyberg, J., and Claesson, H-E. On the mechanism of induction of DNA synthesis in cultured arterial smooth muscle 69. Moody, T. R., Leyton, J., Martinez, A., Hong, S., Malkinson, A., and cells by leukotrienes. Possible role of prostaglandin endoperoxide synthase pro- Mulshine, J. L. Lipoxygenase inhibitors prevent lung carcinogenesis and inhibit ducs and platelet-derived growth factor. J. Cell Sci., 98: 141–149, 1991. non-small cell lung cancer growth. Exp. Lung Res., 24: 617–628, 1998. 45. Leikauf, G. D., Claesson, H-E., Doupnik, C. A., Hybbinette, S., and Graf- 70. Rioux, N., and Castonguay, A. Inhibitors of lipoxygenase: a new class of strom, R. C. Cysteinyl leukotrienes enhance growth of human airway epithelial cancer chemopreventive agents. Carcinogenesis (Lond.), 19: 1393–1400, 1998. cells. Am. J. Pathol., 259: L255–L261, 1989. 71. Avis, I. M., Jett, M., Boyle, T., Vos, M. D., Moody, T., Treston, A. M., 46. Yamaoka, K. A., Claesson, H-E., and Rosen, A. Leukotriene B4 enhances Martinez, A., and Mulshine, J. L. Growth control of lung cancer by interruption activation, proliferation, and differentiation of human B lymphocytes. J. Immu- of 5-lipoxygenase-mediated growth factor signaling. J. Clin. Invest., 97: 806– nol., 143: 1996–2000, 1989. 813, 1996.

72. Kulkarni, A. P., Cai, Y., and Richards, I. S. Rat pulmonary lipoxygenase: 97. Welsch, C. W. Relationship between dietary fat and experimental mammary dioxygenase activity and role in xenobiotic metabolism. Int. J. Biochem., 24: tumorigenesis: a review and critique. Cancer Res., 52: 2040S–2048S, 1992. 255–261, 1992. 98. Dao, T. L., and Hilf, R. Dietary fat and breast cancer: a search for mecha- 73. Nemoto, N., and Takayama, S. Arachidonic acid-dependent activation of nisms. Adv. Exp. Med. Biol., 322: 223–237, 1992. benzo[a]pyrene to bind to proteins with cytosolic and microsomal fractions from 99. Cohen, L. A., Thompson, D. O., Maeura, Y., Choi, K., Blank, M. E., and rat liver and lung. Carcinogenesis (Lond.), 5: 961–964, 1984. Rose, D. P. Dietary fat and mammary cancer. I. Promoting effects of different 74. Hunter, J. A., Finkbeiner, W. E., Nadel, J. A., Goetzl, E. J., and Holtzman, dietary fats on N-nitrosomethylurea-induced rat mammary tumorigenesis. J. Natl. M. J. Predominant generation of 15-lipoxygenase metabolites of arachidonic acid Cancer Inst., 77: 33–42, 1986. by epithelial cells from human trachea. Proc. Natl. Acad. Sci. USA, 82: 4633– 100. Cave, W. T., Jr. Dietary n-3 (␻-3) polyunsaturated fatty acid effects on 4637, 1985. animal tumorigenesis. FASEB J., 5: 2160–2166, 1991. 75. Kumlin, M., and Dahlen, S-E. Characteristics of formation and further 101. Abou-El-Ela, S. H., Prasse, K. W., Carroll, R., Wade, A. E., Dharwadkar, metabolism of leukotrienes in the chopped human lung. Biochim. Biophys. Acta, S., and Bunce, O. R. Eicosanoid synthesis in 7,12-dimethylbenz(a)anthracene- 1044: 201–210, 1990. induced mammary carcinomas in Sprague-Dawley rats fed primrose oil, menha- 76. Chaudry, A., McClinton, S., Moffat, L. E. F., and Wahle, K. W. J. Essential den oil or corn oil diet. Lipids, 23: 948–954, 1988. fatty acid distribution in the plasma and tissue phospholipids of patients with 102. Kort, W. J., Bijma, A. M., van Dam, J. J., van der Ham, A. C., Hekking, benign and malignant prostatic disease. Br. J. Cancer, 64: 1157–1160, 1991. J. M., van der Ingh, H. F., Meijer, W. S., van Wilgenburg, M. G. M., and Zijlstra, 77. Chaudry, A. A., Wahle, K. W. J., McClinton, S., and Moffat, L. E. F. F. J. Eicosanoids in breast cancer patients before and after mastectomy. Prostag- Arachidonic acid metabolism in benign and malignant prostatic tissue in vitro: landins Leukotrienes Essent. Fatty Acids, 45: 319–327, 1992. effects of fatty acids and cyclooxygenase inhibitors. Int. J. Cancer, 57: 176–180, 103. Natarajan, R., Esworthy, R., Bai, W., Gu, J-L., Wilczynski, S., and Nadler, 1994. J. Increased 12-lipoxygenase expression in breast cancer tissues and cells. Reg- 78. Rose, P., and Connolly, J. M. Effects of fatty acids and eicosanoid synthesis ulation by epidermal growth factor. J. Clin. Endocrinol. Metab., 82: 1790–1798, inhibitors on the growth of two human prostate cancer cell lines. Prostate, 18: 1997. 243–254, 1991. 104. Liu, X-H., Connolly, J. M., and Rose, D. P. Eicosanoids as mediators of 79. Drago, J. R., and Al-Mondhiry, H. A. B. The effect of prostaglandin mod- linoleic acid-stimulated invasion and type IV collagenase production by a met- ulators on prostate tumor growth and metastasis. Anticancer Res., 4: 391–394, astatic human breast cancer cell line. Clin. Exp. Metastasis, 14: 145–152, 1996. 1984. 105. Rose, D. P., and Connolly, J. M. Stimulation of growth of human breast 80. Tazume, S., and Pollard, M. The relationship between natural killer cells and cancer cell lines in culture by linoleic acid. Biochem. Biophys. Res. Commun., drugs that modify metastasis of PA-III cells. Cancer Lett., 29: 323–329, 1985. 164: 277–283, 1989. 81. Ablin, R. J., and Shaw, M. W. Prostaglandin modulation of prostate tumor 106. Rose, D. P., and Connolly, J. M. Effects of fatty acids and inhibitors of growth and metastases. Anticancer Res., 6: 327–328, 1986. eicosanoid synthesis on the growth of a human breast cancer cell line in culture. 82. Anderson, K. M., Wygodny, J. B., Ondrey, F., and Harris, J. Human PC-3 Cancer Res., 50: 7139–7144, 1990. prostate cell line DNA synthesis is suppressed by eicosatetraynoic acid, an in vitro 107. Hubbard, N. E., Chapkin, R. S., and Erickson, K. L. Inhibition of growth and inhibitor of arachidonic acid metabolism. Prostate, 12: 3–12, 1988. linoleate-enhanced metastasis of a transplantable mouse mammary tumor by 83. Anderson, K. M., Seed, T. M., Wilson, D. E., and Harris, J. E. 5,8,11,14- indomethacin. Cancer Lett., 43: 111–120, 1988. Eicosatetraynoic acid-induced destruction of mitochondria in human prostate 108. Fulton, A. M. In vivo effects of indomethacin on the growth of murine cells (PC-3). In Vitro Cell. Dev. Biol., 28A: 410–414, 1992. mammary tumors. Cancer Res., 44: 2416–2420, 1984. 84. Anderson, K. M., Seed, T., Ondrey, F., and Harris, J. E. The selective 109. McCormick, D. L., and Moon, R. C. Inhibition of mammary carcinogenesis 5-lipoxygenase inhibitor A63162 reduces PC3 proliferation and initiates morpho- by flurbiprofen, a non-steroidal antiinflammatory agent. Br. J. Cancer, 48: 859– logic changes consistent with secretion. Anticancer Res., 14: 1951–1960, 1994. 861, 1983. 85. Mohler, J. L. Cellular motility and prostatic carcinoma metastases. Cancer 110. Feldman, J. M., and Hilf, R. Failure of indomethacin to inhibit growth of the Metastasis Rev., 12: 53–67, 1993. R3230AC mammary tumor in rats. J. Natl. Cancer Inst., 75: 751–756, 1985. 86. Mohler, J. L., Partin, A. W., and Coffey, D. S. Prediction of metastatic 111. Abou-El-Ela, S. H., Prasse, K. W., Farrell, R. L., Carroll, R. W., Wade, potential by a new grading system of cell motility: validation in the Dunning A. E., and Bunce, O. R. Effects of DL-2-difluoromethylornithine and indometha- R-3327 prostatic adenocarcinoma model. J. Urol., 138: 168–170, 1987. cin on mammary tumor promotion in rats fed high n-3 and/or n-6 fat diets. Cancer 87. Albini, A., Iwamoto, Y., Kleinman, H. K., Martin, G. R., Aaronson, S. A., Res., 49: 1434–1440, 1989. Kozlowski, J. M., and McEwan, R. N. A rapid in vitro assay for qantitating the 112. Buckman, D. K., Hubbard, N. E., and Erickson, K. L. Eicosanoids and invasive potential of tumor cells. Cancer Res., 47: 3239–3245, 1987. linoleate-enhanced growth of mouse mammary tumor cells. Prostaglandins Leu- 88. Timar, J., Tang, D., Bazaz, R., Haddad, M. M., Kimler, V. A., Taylor, J. D., kotrienes Essent. Fatty Acids, 44: 177–184, 1991. and Honn, K. V. PKC mediates 12(S)-HETE-induced cytoskeletal rearrangement 113. Fulton, A. M. Effects of indomethacin on the growth of cultured mammary in B16a melanoma cells. Cell Motil. Cytoskeleton, 26: 49–65, 1993. tumors. Int. J. Cancer, 33: 375–379, 1984. 89. Crooke, S. T., Mattern, M., Sarau, H. M., Winkler, J. D., Balcarek, J., Wong, 114. McCormick, D. L., and Spicer, A. M. Nordihydroguaiaretic acid suppres- A., and Bennett, C. F. The signal transduction system of the leukotriene D4 sion of rat mammary carcinogenesis induced by N-methyl-N-nitrosourea. Cancer receptor. Trends Pharmacol. Sci., 10: 103–107, 1989. Lett., 37: 139–146, 1987. 90. Sumida, C., Graber, R., and Nunez, E. Role of fatty acids in signal trans- 115. Noguchi, M., Kitagawa, H., Miyazaki, I., and Mizukami, Y. Influence of duction: modulators and messengers. Prostaglandins Leukotrienes Essent. Fatty esculetin on incidence, proliferation, and cell kinetics of mammary carcinomas Acids, 48: 117–122, 1993. induced by 7,12-dimethylbenz[a]anthracene in rats on high- and low-fat diets. 91. Hansson, A., Serhan, C. N., Haeggstrom, J., Ingelman-Sundberg, M., and Jpn. J. Cancer Res., 84: 1010–1014, 1993. Samuelsson, B. Activation of protein kinase C by lipoxin A and other eicosanoids. 116. Kitagawa, H., and Noguchi, M. Comparative effects of piroxicam and Intracellular action of oxygenation products of arachidonic acid. Biochem. Bio- esculetin on incidence, proliferation, and cell kinetics of mammary carcinomas phys. Res. Commun., 134: 1215–1222, 1986. induced by 7,12-dimethylbenz[a]anthracene in rats on high- and low-fat diets. 92. Murakami, K., and Routtenberg, A. Direct activation of purified protein Oncology, 51: 401–410, 1994. kinase C by unsaturated fatty acids (oleate and arachidonate) in the absence of ϩ 117. Matsunaga, K., Yoshimi, N., Yamada, Y., Shimizu, M., Kawabata, K., phospholipids and Ca2 . FEBS Lett., 192: 189–193, 1985. Ozawa, Y., Hara, A., and Mori, H. Inhibitory effects of nabumetone, a cyclooxy- 93. Ware, J. L. Growth factors and their receptors as determinants in the prolif- genase-2 inhibitor, and esculetin, a lipoxygenase inhibitor, on N-methyl-N-nitro- eration and metastasis of human prostate cancer. Cancer Metastasis Rev., 12: sourea-induced mammary carcinogenesis in rats. Jpn. J. Cancer Res., 89: 496– 287–301, 1993. 501, 1998. 94. Thompson, T. C. Growth factors and oncogenes in prostate cancer. Cancer 118. Liu, X-H., Connolly, J. M., and Rose, D. P. The 12-lipoxygenase gene- Cells, 2: 345–354, 1990. transfected MCF-7 human breast cancer cell line exhibits estrogen-independent, 95. Karmali, R. A. Eicosanoids in breast cancer. Eur. J. Cancer Clin. Oncol., 23: but estrogen and omega-6 fatty acid-stimulated proliferation in vitro, and en- 5–7, 1987. hanced growth in athymic nude mice. Cancer Lett., 109: 223–230, 1996. 96. Fischer, S. M., Conti, C. J., Locniskar, M., Belury, M. A., Maldve, R. E., Lee, 119. Reddy, N., Everhart, A., Eling, T., and Glasgow, W. Characterization of a M. L., Leyton, J., Slaga, T. J., and Bechtel, D. H. The effect of dietary fat on the 15-lipoxygenase in human breast carcinoma BT-20 cells: stimulation of 13- rapid development of mammary tumors induced by 7,12-dimethylbenz(a)anthra- HODE formation by TGF␣/EGF. Biochem. Biophys. Res. Commun., 231: 111– cene in SENCAR mice. Cancer Res., 52: 662–666, 1992. 116, 1997.

120. Jardines, L., Weiss, M., Fowble, B., and Greene, M. neu (c-erbB-2/HER2) 143. Anderson, K. M., Seed, T., Plate, J. M. D., Jajeh, A., Meng, J., and Harris, and the epidermal growth factor receptor (EGFR) in breast cancer. Pathobiology, J. E. Selective inhibitors of 5-lipoxygenase reduce CML blast cell proliferation 61: 268–282, 1993. and induce limited differentiation and apoptosis. Leuk. Res., 19: 789–801, 1995. 121. Fox, S. B., Smith, K., Hollyer, J., Greenall, M., Hastrich, D., and Harris, 144. Snyder, D. S., Castro, R., and Desforges, J. F. Antiproliferative effects of A. L. The epidermal growth factor receptor as a prognostic marker: results of 370 lipoxygenase inhibitors on malignant human hematopoietic cell lines. Exp. He- patients and review of 3009 patients. Breast Cancer Res. Treat., 29: 41–49, 1994. matol., 17: 6–9, 1989. 122. Zhuang, Z-P., Vortmeyer, A. O., Mark, E. J., Odze, R., Emmert-Buck, 145. Brooks, C. D. W., and Summers, J. B. Modulators of leukotriene biosyn- M. R., Merino, M. J., Moon, H., Liotta, L. A., and Duray, P. H. Barrett’s thesis and receptor activation. J. Med. Chem. 39: 2629–2654, 1996. esophagus: metaplastic cells with loss of heterozygosity at the APC gene locus are 146. Carter, G. W., Young, P. R., Albert, D. H., Bouska, J., Dyer, R., Bell, R. L., clonal precursors to invasive adenocarcinoma. Cancer Res., 56: 1961–1964, 1996. Summers, J. B., and Brooks, D. W. 5-Lipoxygenase inhibitory activity of Zileu- 123. Rose, D. P., Connolly, J. M., and Liu, X-H. Effects of linoleic acid on the ton. J. Pharmacol. Exp. Ther., 256: 929–937, 1991. growth and metastasis of two human breast cancer cell lines in nude mice and the 147. Read, N. G., Astbury, P. J., Evans, G. O., Goodwin, D. A., and Rowlands, invasive capacity of these cell lines in vitro. Cancer Res., 54: 6557–6562, 1994. A. Nephrotic syndrome associated with N-hydroxyureas, inhibitors of 5-lipoxy- 124. Rose, D., and Connolly, J. M. Effects of dietary ␻-3 fatty acids on human genase. Arch. Toxicol., 69: 480–490, 1995. breast cancer growth and metastases in nude mice. J. Natl. Cancer Inst., 85: 148. Bell, R. L., Brooks, D. W., Young, P. R., Lanni, C., Stewart, A. O., Bouska, 1743–1747, 1993. J., Malo, P. E., and Carter, G. W. A-78773: a selective, potent 5-lipoxygenase inhibitor. J. Lipid Mediat., 6: 259–264, 1993. 125. Johanning, G. L., and Lin, T-Y. Unsaturated fatty acid effects on human breast cancer cell adhesion. Nutr. Cancer, 24: 57–66, 1995. 149. Brooks, C. D. W., Stewart, A. O., Basha, A., Bhatia, P., Ratajczyk, J. D., Martin, J. G., Craig, R. A., Kolasa, T., Bouska, J. B., Lanni, C., Harris, R. R., 126. Rigas, B., Goldman, I. S., and Levine, L. Altered eicosanoid levels in human Malo, P. E., Carter, G. W., and Bell, R. L. (R)-(ϩ)-N-[3-[5-[(4-fluorophenyl)- colon cancer. J. Lab. Clin. Med., 122: 518–523, 1993. methyl]-2-thienyl]-1-methyl-2-propynyl]-N-hydroxyurea (ABT-761), a second- 127. Bortuzzo, C., Hanif, R., Kashfi, K., Staiano-Coico, L., Shiff, S. J., and generation 5-lipoxygenase inhibitor. J. Med. Chem., 38: 4768–4775, 1995. Rigas, B. The effect of leukotrienes B and selected HETEs on the proliferation of 150. Nakadate, T., Yamamoto, S., Aizu, E., and Kato, R. Inhibition of mouse colon cancer cells. Biochim. Biophys. Acta, 1300: 240–246, 1996. epidermal 12-lipoxygenase by 2,3,4-trimethyl-6-(12-hydroxy-5,10-dodecadiy- 128. Hussey, H. J., and Tisdale, M. J. Inhibition of tumour growth by lipoxy- nyl)-1,4-benzoquinone (AA861). J. Pharm. Pharmacol., 37: 71–73, 1985. genase inhibitors. Br. J. Cancer, 74: 683–687, 1996. 151. Aizu, E., Nakadate, T., Yamamoto, S., and Kato, R. Inhibition of 12-O- 129. Cortese, J. F., Spannhake, E. W., Eisinger, W., Potter, J. J., and Yang, V. W. tetradecanoylphorbol-13-acetate-mediated epidermal ornithine decarboxylase in- The 5-lipoxygenase pathway in cultured human intestinal epithelial cells. Pros- duction and skin tumor promotion by new lipoxygenase inhibitors lacking protein taglandins, 49: 155–166, 1995. kinase C inhibitory effects. Carcinogenesis (Lond.), 7: 1809–1812, 1986. 130. Sjolander, A., Schippert, A., and Hammarstrom, S. A human epithelial cell 152. Uzumaki, H., Yamamoto, S., and Kato, R. Effects of lipoxygenase and line, intestine-407, can produce 5-hydroxyeicosatetraenoic acid and leukotriene cyclooxygenase inhibitors on the induction of ornithine decarboxylase by 12-O- B4. Prostaglandins, 45: 85–96, 1993. tetradecanoylphorbol-13-acetate and isoproterenol in mouse tissues in vivo. Car- cinogenesis (Lond.), 7: 289–294, 1986. 131. Dias, V. C., Wallace, J. L., and Parsons, H. G. Modulation of cellular phospholipid fatty acids and leukotriene B4 synthesis in the human intestinal cell 153. Tsukada, T., Nakashima, K., and Shirakawa, S. Arachidonate 5-lipoxyge- (CaCo-2). Gut, 33: 622–627, 1992. nase inhibitors show potent antiproliferative effects on human leukemia cell lines. Biochem. Biophys. Res. Commun., 140: 832–836, 1986. 132. Craven, P. A., and DeRubertis, F. R. Profiles of eicosanoid production by 154. Ralph, R. K., and Wojcik, S. Inhibitors of lipoxygenase have antiprolifera- superficial and proliferative colonic epithelial cells and sub-epithelial colonic tive effects on P815 murine mastocytoma cells. Cancer Lett., 49: 181–185, 1990. tissue. Prostate, 32: 387–399, 1986. 155. Tang, D. G., Chen, Y. Q., and Honn, K. V. Arachidonate lipoxygenases as 133. Gao, X., and Honn, K. V. Biological properties of 12(S)-HETE in cancer essential regulators of cell survival and apoptosis. Proc. Natl. Acad. Sci. USA, 93: metastasis. Adv. Prostaglandin Thromboxane Leukotriene Res., 23: 439–444, 5241–5246, 1996. 1995. 156. Crawley, G. C., Dowell, R. I., Edwards, P. N., Foster, S. J., McMillan, 134. Krieg, P., Kinzig, A., Ress-Loschke, M., Vogel, S., Vanlandingham, B., R. M., Walker, E. R. H., and Waterson, D. Methoxytetrahydropyrans. A new Stephan, M., Lehmann, W-D., Marks, F., and Furstenberger, G. 12-Lipoxygenase series of selective and orally potent 5-lipoxygenase inhibitors. J. Med. Chem., 35: isoenzymes in mouse skin tumor development. Mol. Carcinog., 14: 118–129, 2600–2609, 1992. 1995. 157. Gillard, J., Ford-Hutchinson, A. W., Chan, C., Charleson, S., Denis, D., 135. Takahashi, Y., Reddy, G. R., Ueda, N., Yamamoto, S., and Arase, S. Foster, A., Fortin, R., Leger, S., McFarlane, C. S., Morton, H., Piechuta, H., Arachidonate 12-lipoxygenase of platelet-type in human epidermal cells. J. Biol. Riendeau, D., Rouzer, C. A., Rokach, J., Young, R., MacIntyre, D. E., Peterson, Chem., 268: 16443–16448, 1993. L., Bach, T., Eiermann, G., Hopple, S., Humes, J., Hupe, L., Luell, S., Metzger, 136. Liu, Y-W., Asaoka, Y., Suzuki, H., Yoshimoto, T., Yamamoto, S., and J., Meurer, R., Miller, D. K., Opas, E., and Pacholok, S. L-663,536 (MK-886) Chang, W-C. Induction of 12-lipoxygenase expression by epidermal growth (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2-dimethylpro- factor is mediated by protein kinase C in A431 cells. J. Pharmacol. Exp. Ther., panoic acid), a novel, orally active leukotriene biosynthesis inhibitor. Can. 271: 567–573, 1994. J. Physiol. Pharmacol., 67: 456–464, 1989. 137. Chen, B-K., Liu, Y-W., Yamamoto, S., and Chang, W-C. Overexpression of 158. Ford-Hutchinson, A. W., Gresser, M., and Young, R. N. 5-Lipoxygenase. Ha-ras enhances the transcription of human arachidonate 12-lipoxygenase pro- Annu. Rev. Biochem., 63: 383–417, 1994. moter in A431 cells. Biochim. Biophys. Acta, 1344: 270–277, 1997. 159. Bel, E. H., Tanaka, W., Spector, R., Friedman, B., von de Veen, H., 138. El Attar, T. M. A., Lin, H. S., and Vanderhoek, J. Y. Biosynthesis of Dijkman, J. H., and Sterk, P. J. MK-886, an effective oral leukotriene biosynthesis prostaglandins and hydroxy fatty acids in primary squamous carcinomas of head inhibitor on antigen-induced early and late asthmatic reactions in man. Am. Rev. and neck in humans. Cancer Lett., 27: 255–259, 1985. Respir. Dis., 141: A31, 1990. 139. Liu, B., Marnett, L. J., Chaudhary, A., Ji, C., Blair, I. A., Johnson, C. R., 160. Prasit, P., Belley, M., Blouin, M., Brideau, C., Chan, C., Charleson, S., Diglio, C. A., and Honn, K. V. Biosynthesis of 12(S)-hydroxyeicosatetraenoic Evans, J. F., Frenette, R., Gauthier, J. Y., Guay, J., Gillard, J. W., Grimm, E., acid by B16 amelanotic melanoma cells is a determinant of their metastatic Ford-Hutchinson, A. W., Hutchinson, J. H., Fortin, R., Jones, T. R., Mancini, J., potential. Lab. Invest., 70: 314–323, 1994. Leger, S., McFarlane, C. S., Piechuta, H., Riendeau, D., Roy, P., Tagari, P., Vickers, P. J., Young, R. N., and Zamboni, R. A new class of leukotriene 140. Anderson, K. M., Levin, J., Jajeh, A., Seed, T., and Harris, J. E. Induction biosynthesis inhibitor: the development of MK-0591. J. Lipid Mediat., 6: 239– of apoptosis in blood cells from a patient with acute myelogenous leukemia by 244, 1993. SC41661A, a selective inhibitor of 5-lipoxygenase. Prostaglandins Leukotrienes 161. Hatzelmann, A., Fruchtmann, R., Mohrs, K. H., Raddatz, S., and Muller- Essent. Fatty Acids, 48: 323–326, 1993. Peddinghaus, R. Mode of action of the new selective leukotriene synthesis 141. Anderson, K. M., Seed, T., Jajeh, A., Dudeja, P., Byun, T., Meng, J., Ou, D., inhibitor BAY X-1005 ((R)-2-[4-(quinolin-2-yl-methoxy)phenyl]-2-cyclopentyl Bonomi, P., and Harris, J. E. An in vivo inhibitor of 5-lipoxygenase, MK886, at acetic acid) and structurally related compounds. Biochem. Pharmacol., 45: 101– micromolar concentration induces apoptosis in U937 and CML cells. Anticancer 111, 1993. Res., 16: 2589–2599, 1996. 162. Muller-Peddinghaus, R., Fruchtmann, R., Ahr, H-J., Beckermann, B., 142. Stenke, L., Samuelsson, J., Palmblad, J., Dabrowski, L., Reizenstein, P., and Buhner, K., Fugmann, B., Junge, B., Matzke, M., Kohlsdorfer, C., Raddatz, S., Lindgren, J. A. Elevated white blood cell synthesis of leukotriene C4 in chronic Theisen-Popp, P., and Mohrs, K-H. BAY X1005, a new selective inhibitor of myelogenous leukaemia but not in polycynthaemia vera. Br. J. Haematol., 74: leukotriene synthesis: pharmacology and pharmacokinetics. J. Lipid Mediat., 6: 257–263, 1990. 245–248, 1993.

163. Fruchtmann, R., Mohrs, K. H., Hatzelmann, A., Raddatz, S., Fugmann, B., 184. Matsuzaki, Y., Kurokawa, N., Terai, S., Matsumura, Y., Kobayashi, N., and Junge, B., Horstmann, H., and Muller-Peddinghaus, R. In vitro pharmacology of Okita, K. Cell death induced by baicalein in hepatocellular carcinoma cell lines. BAY X1005, a new inhibitor of leukotriene synthesis. Agents Actions, 38: Jpn. J. Cancer Res., 87: 170–177, 1996. 188–195, 1993. 185. Okita, K., Li, Q., Murakamio, T., and Takahashi, M. Anti-growth effects 164. Hatzelmann, A., Fruchtmann, R., Mohrs, K. H., Raddatz, S., Matzke, M., with components of Sho-saiko-to (TJ-9) on cultured human hepatoma cells. Eur. Pleiss, U., Keldenich, J., and Muller-Peddinghaus, R. Mode of action of the J. Cancer Prev., 2: 169–176, 1993. leukotriene synthesis (FLAP) inhibitor BAY X 1005: implications for biological 186. Li, Q., Okita, K., Murakami, T., and Takahashi, M. Inhibitory effect of regulation of 5-lipoxygenase. Agents Actions, 43: 64–68, 1994. baicalein on the growth of cultured hepatoma cells (HuH-7). Biotherapy, 4: 165. Djuric, S. W., Collins, P. W., Jones, P. H., Shone, R. L., Tsai, B. S., 1664–1670, 1990. Fretland, D. J., Butchko, G. M., Villani-Price, D., Keith, R. H., Zemaitis, J. M., 187. So, F. V., Guthrie, N., Chambers, A. F., and Carroll, K. K. Inhibition of Metcalf, L., and Bauer, R. F. 7-[3-(4-Acetyl-3-methoxy-2-propylphe- proliferation of estrogen receptor-positive MCF-7 human breast cancer cells by noxy)propoxy]-3,4-dihydro-8-propyl-2H-1-benzopyran-2-carboxylic acid: an flavonoids in the presence and absence of excess estrogen. Cancer Lett., 112: orally active selective leukotriene B4 receptor antagonist. J. Med. Chem., 32: 127–133, 1997. 1145–1147, 1989. 188. Huang, F-C., Shoupe, T. S., Lin, C. J., Lee, T. D. Y., Chan, W-K., Tan, J., 166. Tsai, B. S., Villani-Price, D., Keith, R. H., Zemaitis, J. M., Bauer, R. F., Schnapper, M., Suh, J. T., Gordon, R. J., Sonnino, P. A., Sutherland, C. A., Van Leonard, R., Djuric, S. W., and Shone, R. L. SC-41930: an inhibitor of leukotriene Inwegen, R. G., and Coutts, S. M. Differential effects of a series of hydroxamic B4-stimulated human neutrophil functions. Prostaglandins, 38: 655–674, 1989. acid derivatives on 5-lipoxygenase and cyclooxygenase from neutrophils and 167. Penning, T. D., Djuric, S. W., Miyashiro, J. M., Yu, S., Snyder, J. P., 12-lipoxygenase from platelets and their in vivo effects on inflammation and Spangler, D., Anglin, C. P., Fretland, D. J., Kachur, J. F., Keith, R. H., Tsai, B. S., anaphylaxis. J. Med. Chem., 32: 1836–1842, 1989. Villani-Price, D., Walsh, R. E., and Widomski, D. L. Second-generation leuko- 189. Marnett, L. J., Leithauser, M. T., Richards, K. M., Blair, I., Honn, K. V., triene B4 receptor antagonists related to SC-41930: heterocyclic replacement of Yamamoto, S., and Yoshimoto, T. Arachidonic acid metabolism of cytosolic the methyl ketone pharmacophore. J. Med. Chem., 38: 858–868, 1995. fractions of Lewis lung carcinoma cells. Adv. Prostaglandin Thromboxane Leuk- 168. Tsai, B. S., Keith, R. H., Villani-Price, D., Kachur, J. F., Yang, D. C., otriene Res., 21B: 895–900, 1991. Djuric, S. W., and Yu, S. The in vitro pharmacology of SC-51146: a potent 190. Yaffee, M., Walter, P., Richter, C., and Muller, M. Direct observation of antagonist of leukotriene B4 receptors. J. Pharmacol. Exp. Ther., 268: 1499– iron-induced conformational changes of mitochondrial DNA by high-resolution 1505, 1994. field-emission in-lens scanning electron microscopy. Proc. Natl. Acad. Sci. USA, 169. Djuric, S. W., Docter, S. H., Yu, S. S., and Spangler, D. Synthesis and 93: 5341–5346, 1996. pharmacological activity of SC-53228, a leukotriene B4 receptor antagonist with high intrinsic potency and selectivity. Bioorg. Med. Chem. Lett., 4: 811–816, 191. Denis, D., Falgueyret, J-P., Riendeau, D., and Abramovitz, M. Character- 1994. ization of the activity of purified recombinant human 5-lipoxygenase in the absence and presence of leukocyte factors. J. Biol. Chem., 266: 5072–5079, 1991. 170. Krell, R. D., Aharony, D., Buckner, C. K., Keith, R. A., Kusner, E. J., Snyder, D. W., Bernstein, P. R., Matassa, V. G., Yee, Y. K., Brown, F. J., Hesp, 192. Percival, M. D., Denis, D., Riendeau, D., and Gresser, M. J. Investigation B., and Giles, R. E. The preclinical pharmacology of ICI 204,219: a peptide of the mechanism of non-turnover-dependent inactivation of purified human leukotriene antagonist. Am. Rev. Respir. Dis., 141: 978–987, 1990. 5-lipoxygenase. Inactivation by H2O2 and inhibition by metal ions. Eur. J. Bio- chem., 210: 109–117, 1992. 171. F-D-C Reports. FDA reform should focus on consensus issues first, Rep. Fox urges house leadership. Commerce committee may produce several separate 193. Rouzer, C. A., and Samuelsson, B. Leukocyte arachidonate 5-lipoxygenase: bills. FDC Reports (The Pink Sheet), 58: 3, 1996. isolation and characterization. Methods Enzymol., 187: 312–319, 1990. 172. Sekiya, K., Okuda, H., and Arichi, S. Selective inhibition of platelet lipoxy- 194. Mosmann, T. Rapid colorimetric assay for cellular growth and survival: genase by esculetin. Biochim. Biophys. Acta, 713: 68–72, 1982. application to proliferation and cytotoxicity assays. J. Immunol. Methods, 65: 55–63, 1983. 173. Neichi, T., Koshihara, Y., and Murota, S-I. Inhibitory effect of esculetin on 5-lipoxygenase and leukotriene biosynthesis. Biochim. Biophys. Acta, 753: 130– 195. Steele, V. E., Moon, R. C., Lubet, R. A., Grubbs, C. J., Reddy, B. S., 132, 1983. Wargovich, M., McCormick, D. L, Pereira, M. A., Crowell, J. A., Bagheri, D., Sigman, C. C., Boone, C. W., and Kelloff, G. J. Preclinical efficacy evaluation of 174. Panossian, A. G. Inhibition of arachidonic acid 5-lipoxygenase of human potential chemopreventive agents in animal carcinogenesis models: methods and polymorphonuclear leukocytes by esculetin. Biochim. Biophys. Acta, 43: 1351– results from the NCI Chemoprevention Drug Development Program. J. Cell. 1355, 1984. Biochem., 20: 32–54, 1994. 175. Kimura, Y., Okuda, H., Arichi, S., Baba, K., and Kozawa, M. Inhibition of 196. Gullino, P. M., Pettigrew, H. M., and Grantham, F. H. N-Nitrosomethylurea the formation of 5-hydroxy-6,8,11,14-eicosatetraenoic acid from arachidonic acid as mammary gland carcinogen in rats. J. Natl. Cancer Inst., 54: 401–414, 1975. in polymorphonuclear leukocytes by various coumarins. Biochim. Biophys. Acta, 834: 224–229, 1985. 197. McCormick, D. L., Adamowski, C. B., Fiks, A., and Moon, R. C. Lifetime dose-response relationships for mammary tumor induction by a single adminis- 176. Tubaro, A., Del Negro, P., Ragazzi, E., Zampiron, S., and Loggia, R. D. tration of N-methyl-N-nitrosourea. Cancer Res., 41: 1690–1694, 1981. Anti-inflammatory and peripheral analgesic activity of esculetin in vivo. Phar- macol. Res. Commun., 20: 83–85, 1988. 198. Moon, R. C., and Mehta, R. G. Chemoprevention of experimental carcinogenesis in animals. Prev. Med., 18: 576–591, 1989. 177. Earashi, M., Noguchi, M., Kinoshita, K., and Tanaka, M. Effects of eicosanoid synthesis inhibitors on the in vitro growth and prostaglandin E and 199. Stoner, G. D. Lung tumors in strain A mice as a bioassay for carcinogenicity leukotriene B secretion of a human breast cancer cell line. Oncology, 52: 150– of environmental chemicals. Exp. Lung Res., 17: 405–423, 1991. 155, 1995. 200. Wattenberg, L. W., Wiedmann, T. S., Estensen, R. D., Zimmerman, C. L., 178. Huang, H-C., Hsieh, L-M., Chen, H-W., Lin, Y-S., and Chen, J-S. Effects Steele, V. E., and Kelloff, G. J. Chemoprevention of pulmonary carcinogenesis by of baicalein and esculetin on transduction signals and growth factors expression aerosolized budesonide in female A/J mice. Cancer Res., 57: 5489–5492, 1997. in T-lymphoid leukemia cells. Eur. J. Pharmacol., 268: 73–78, 1994. 201. Boone, C. W., Kelloff, G. J., and Malone, W. E. Identification of candidate 179. Huang, H-C., Lai, M-W., Wang, H-R., Chung, Y-L., Hsieh, L-M., and cancer chemopreventive agents and their evaluation in animal models and human Chen, C-C. Antiproliferative effect of esculetin on vascular smooth muscle cells. clinical trials: a review. Cancer Res., 50: 2–9, 1990. Possible roles of signal transduction pathways. Eur. J. Pharmacol., 237: 39–44, 202. Reddy, B. S., and Maeura, Y. Tumor promotion by dietary fat in azoxymeth- 1993. ane-induced colon carcinogenesis in female F344 rats: influence of amount and 180. Reich, R., and Martin, G. R. Identification of arachidonic acid pathways source of dietary fat. J. Natl. Cancer. Inst., 72: 745–750, 1984. required for the invasive and metastatic activity of malignant tumor cells. Pros- 203. Bird, R. P. Observation and quantification of aberrant crypts in the murine taglandins, 51: 1–17, 1996. colon treated with a colon carcinogen: preliminary findings. Cancer Lett., 37: 181. Sekiya, K., and Okuda, H. Selective inhibition of platelet lipoxygenase by 147–151, 1987. baicalein. Biochem. Biophys. Res. Commun., 105: 1090–1095, 1982. 204. Pereira, M. A., Barnes, L. H., Rassman, V. L., Kelloff, G. V., and Steele, 182. Butenko, I. G., Gladtchenko, S. V., and Galushko, S. V. Anti-inflammatory V. E. Use of azoxymethane-induced foci of aberrant crypts in rat colon to identify properties and inhibition of leukotriene C4 biosynthesis in vitro by flavonoid potential cancer chemopreventive agents. Carcinogenesis (Lond.), 15: 1049– baicalein from Scutellaria baicalensis Georgy roots. Agents Actions, 39: C49– 1054, 1994. C51, 1993. 205. Pretlow, T. P., Barrow, B. J., Ashton, W. S., O’Riordan, M. A., Pretlow, 183. Motoo, Y., and Sawabu, N. Antitumor effects of saikosaponins, baicalin and T. G., Jurcisek, J. A., and Stellato, T. A. Aberrant crypts: putative preneoplastic baicalein on human hepatoma cell lines. Cancer Lett., 86: 91–95, 1994. foci in human colonic mucosa. Cancer Res., 51: 1564–1567, 1991.

206. Leav, I., Ho, S-M., Ofner, P., Merk, F. B., Kwan, P. W-L., and Damassa, D. 228. Rao, T. S., Currie, J. L., Shaffer, A. F., and Isakson, P. C. Evaluation of Biochemical alterations in sex hormone-induced hyperplasia and dysplasia of the 5-lipoxygenase inhibitors, Zileuton, A-78773 and ICI-D-2138 in an ionophore dorsolateral prostates of Noble rats. J. Natl. Cancer Inst., 80: 1045–1053, 1988. (A-23187)-induced pleural inflammation model in the rat. Life Sci., 53: PL147– 207. Noble, R. L. The development of prostatic adenocarcinoma in Nb rats PL152, 1993. following prolonged sex hormone administration. Cancer Res., 37: 1929–1933, 229. Sirois, P., Borgeat, P., Lauziere, M., Dube, L., Rubin, P., and Kesterson, J. 1977. Effect of Zileuton (A-64077) on the 5-lipoxygenase activity of human whole 208. Bosland, M. C., and Prinsen, M. K. Induction of dorsolateral prostate blood ex vivo. Agents Actions, 34: 117–120, 1991. adenocarcinomas and other accessory sex gland lesions in male Wistar rats by a 230. Braeckman, R. A., Granneman, G. R., Rubin, P. R., and Kesterson, J. W. single administration of N-methyl-N-nitrosourea, 7,12-dimethylbenz[a]anthra- Pharmacokinetics and metabolism of the new 5-lipoxygenase inhibitor A-64077 cene, and 3,2Ј-dimethyl-4-aminobiphenyl after sequential treatment with cypro- after single oral administration in man. J. Clin. Pharmacol., 29: 837, 1989. terone acetate and testosterone propionate. Cancer Res., 50: 691–699, 1990. 209. Bosland, M. C., Prinsen, M. K., Dirksen, T. J. M., and Spit, B. J. Charac- 231. Yoshimoto, T., Yokoyama, C., Ochi, K., Yamamoto, S., Maki, Y., Ashida, terization of adenocarcinomas of the dorsolateral prostate induced in Wistar rats Y., Terao, S., and Shiraishi, M. 2,3,5-Trimethyl-6-(12-hydroxy-5,10-dodecadiy- by N-methyl-N-nitrosourea, 7,12-dimethylbenz[a]anthracene, and 3,2Ј-dimethyl- nyl)-1,4-benzoquinone (AA861), a selective inhibitor of the 5-lipoxygenase re- 4-aminobiphenyl, following sequential treatment with cyproterone acetate and action and the biosynthesis of slow-reacting substance of anaphylaxis. Biochim. testosterone. Cancer Res., 50: 700–709, 1990. Biophys. Acta, 713: 470–473, 1982. 210. Warren, B. S., and Slaga, T. J. Mechanisms of inhibition of tumor progres- 232. Nakadate, T., Yamamoto, S., Aizu, E., and Kato, R. Inhibition of 12-O- sion. Basic Life Sci., 61: 279–289, 1993. tetradecanoylphorbol-13-acetate-induced increase in vascular permeability in 211. DiGiovanni, J. Multistage carcinogenesis in mouse skin. Pharmacol. Ther., mouse skin by lipoxygenase inhibitors. Jpn. J. Pharmacol., 38: 161–168, 1985. 54: 63–128, 1992. 233. Walker, E. R. H. The design of therapeutically effective 5-lipoxygenase 212. diGiovanni, J., Slaga, T. J., and Boutwell, R. K. Comparison of the tumor- inhibitors. Eur. J. Med. Chem., 30: S399–S416, 1995. initiating activity of 7,12-dimethylbenz[a]anthracene and benzo[a]pyrene in female SENCAR and CD-1 mice. Carcinogenesis (Lond.), 1: 381–389, 1980. 234. Yates, R. A., McMillan, R. M., Ellis, S. H., Hutchison, M., Gilmore, E., Wilkinson, D., and Williams, A. J. A new non redox 5-lipoxygenase inhibitor ICI 213. Hagerman, R. A., Smith, T. J., and Locniskar, M. F. Lipoxygenase metab- D2138 is well tolerated and inhibits blood leukotriene synthesis in healthy olites activate protein kinase C. FASEB J., 7: A601, 1993. volunteers. Am. Rev. Respir. Dis., 45: A745, 1992. 214. Solano, A. R., Dada, L., and Podesta, E. J. Lipoxygenase products as common intermediates in cyclic AMP-dependent and -independent adrenal ste- 235. Khan, M. A., Hoffbrand, A. V., Mehta, A., Wright, F., Tahami, F., and roidogenesis in rats. J. Mol. Endocrinol., 1: 147–154, 1988. Wickremasinghe, R. G. MK 886, an antagonist of leukotriene generation, inhibits DNA synthesis in a subset of acute myeloid leukaemia cells. Leuk. Res., 17: 215. Wang, X-Q., Otsuka, M., Takagi, J., Kobayashi, Y., Sato, F., and Saito, Y. 759–762, 1993. Inhibition of adenylyl cyclases by 12(S)-hydroxyeicosatetraenoic acid. Biochem. Biophys. Res. Commun., 228: 81–87, 1996. 236. Brideau, C., Chan, C., Charleson, S., Denis, D., Evans, J. F., Ford-Hutchin- 216. Hagmann, W. Cell proliferation status, cytokine action and protein tyrosine son, A. W., Fortin, R., Gillard, J. W., Guay, J., Guevremont, D., Hutchinson, J. H., phosphorylation modulate leukotriene biosynthesis in a basophil leukaemia and a Jones, T. R., Leger, S., Mancini, J. A., McFarlane, C. S., Pickett, C., Piechuta, H., mastocytoma cell line. Biochem. J., 299: 467–472, 1994. Prasit, P., Riendeau, D., Rouzer, C. A., Tagari, P., Vickers, P. J., Young, R. N., and Abraham, W. M. Pharmacology of MK-0591 (3-[1-(4-chlorobenzyl)-3-(t- 217. Lepley, R. A., Muskardin, D. T., and Fitzpatrick, F. A. Tyrosine kinase butylthio)-5-(quinolin-2-yl-methoxy)-indol-2-yl]-2,2-dimethyl propanoic acid), a activity modulates catalysis and translocation of cellular 5-lipoxygenase. J. Biol. potent, orally active leukotriene biosynthesis inhibitor. Can. J. Physiol. Pharma- Chem., 271: 6179–6184, 1996. col., 70: 799–807, 1992. 218. O’Donnell, V. B., Spycher, S., and Azzi, A. Involvement of oxidants and oxidant-generating enzyme(s) in tumour-necrosis-factor-␣-mediated apoptosis: 237. Diamant, Z., Timmers, M. C., van der Veen, H., Friedman, B. S., De Smet, role for lipoxygenase pathway but not mitochondrial respiratory chain. Biochem. M., Depre, M., Hilliard, D., Bel, E. H., and Sterk, P. J. The effect of MK-0591, J., 310: 133–141, 1995. a novel 5-lipoxygenase activating protein inhibitor, on leukotriene biosynthesis and allergen-induced airway responses in asthmatic subjects in vivo. J. Allergy 219. Peppelenbosch, M. P., Tertoolen, L. G. J., den Hertog, J., and de Laat, S. W. Clin. Immunol., 95: 42–51, 1995. Epidermal growth factor activates calcium channels by phospholipase A2/5- lipoxygenase-mediated leukotriene C4 production. Cell, 69: 295–303, 1992. 238. Muller-Peddinghaus, R., Kohlsdorfer, C., Theisen-Popp, P., Fruchtmann, 220. Crawford, D., Zbinden, I., Amstad, P., and Cerutti, P. Oxidant stress induces R., Perzborn, E., Beckermann, B., Buhner, K., Ahr, H-J., and Mohrs, K-H. BAY the proto-oncogenes c-fos and c-myc in mouse epidermal cells. Oncogene, 3: X1005, a new inhibitor of leukotriene synthesis: in vivo inflammation pharma- 27–32, 1988. cology and pharmacokinetics. J. Pharmacol. Exp. Ther., 267: 51–57, 1993. 221. Buttke, T. M., and Sandstrom, P. A. Oxidative stress as a mediator of 239. Hortsmann, R., Beckermann, B., Boettcher, M., Dietrich, H., Lemm, G., apoptosis. Immunol. Today, 15: 7–10, 1994. Seitz, I., and Fauler, J. Clinical pharmacological investigations with the new 222. Anderson, K. M., Seed, T. M., Peng, J., Jajeh, A., Meng, J., and Harris, J. E. leukotriene synthesis inhibitor BAY X1005. Am. J. Respir. Crit. Care Med., 149: Morphologic changes of apoptosis induced in human chronic myelogenous leu- A465, 1994. kemia “blast” cells by SC41661A (Searle), a selective inhibitor of 5-lipoxygen- 240. Yu, S. S., Djuric, S. W., Dygos, J. H., Tsai, B. S., Paulson, S. K., Smith, ase. Scanning Microsc., 8: 675–686, 1994. P. F., and Fretland, D. J. SC-53228. Drugs Future, 19: 1093–1097, 1994. 223. Timar, J., Silletti, S., Bazaz, R., Raz, A., and Honn, K. V. Regulation of 241. O’Shaughnessy, T. C., Georgiou, P., Howland, K., Dennis, M., Compton, C melanoma-cell motility by the lipoxygenase metabolite 12-(S)-HETE. Int. J. H., and Barnes, N. C. Effect of pranlukast, an oral leukotriene receptor antagonist, Cancer, 55: 1003–1010, 1993. on leukotriene D4 (LTD4) challenge in normal volunteers. Thorax, 52: 519–522, 224. Ford-Hutchinson, A. W., Bray, M. A., Doig, M. V., Shipley, M. E., and 1997. Smith, M. J. H. Leukotriene B, a potent chemokinetic and aggregating substance released from polymorphonuclear leukocytes. Nature (Lond.), 286: 264–265, 242. Grossman, J., Bronsky, E., Busse, W., Montanaro, A., Southern, L., Tinkel- 1980. man, D., Dubb, J., and Faiferman, I. A multicenter, double-blind, placebo- controlled study to evaluate the safety, tolerability and clinical activity of oral, 225. Strasser, T., Fischer, S., and Weber, P. C. Inhibition of leukotriene B4 twice-daily LTA, pranlukast (SB 205312) in patients with mild to moderate formation in human neutrophils after oral nafazatrom (Bay g 6575). Biochem. asthma. J. Allergy Clin. Immunol., 95: 352, 1995. Pharmacol., 34: 1891–1894, 1985. 226. Keshavarzian, A., Sedghi, S., Kanofsky, J., List, T., Robinson, C., Ibrahim, 243. Smith, L. J., Geller, S., Ebright, L., Glass, M., and Thyrum, P. T. Inhibition C., and Winship, D. Excessive production of reactive oxygen metabolites by of leukotriene D4-induced bronchoconstriction in normal subjects by the oral inflamed colon: analysis by chemiluminescence probe. Gastroenterology, 103: LTD4 receptor antagonist ICI 204,219. Am. Rev. Respir. Dis., 141: 988–992, 177–185, 1992. 1990. 227. Papadogiannakis, N., and Barbieri, B. Lipoxygenase inhibitors counteract 244. Lin, C-C., and Shieh, D-E. The anti-inflammatory activity of Scutellaria protein kinase C mediated events in human T lymphocyte proliferation. Int. rivularis extracts and its active components, baicalin, baicalein and wogonin. J. Immunopharmacol., 19: 263–275, 1997. Am. J. Chin. Med., 24: 31–36, 1996.

Vernon E. Steele, Cathy A. Holmes, Ernest T. Hawk, et al.

Cancer Epidemiol Biomarkers Prev 1999;8:467-483.

Updated version Access the most recent version of this article at: http://cebp.aacrjournals.org/content/8/5/467

Cited articles This article cites 227 articles, 52 of which you can access for free at: http://cebp.aacrjournals.org/content/8/5/467.full#ref-list-1

Citing articles This article has been cited by 21 HighWire-hosted articles. Access the articles at: http://cebp.aacrjournals.org/content/8/5/467.full#related-urls

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://cebp.aacrjournals.org/content/8/5/467. Click on "Request Permissions" which will take you to the Copyright Clearance Center's (CCC) Rightslink site.