Abstract
Purpose. This study aims to evaluate a cytochrome P450-based tamoxifen-isoflavone interaction and to determine the mechanisms responsible for inhibitory effects of isoflavones (e.g., genistein) on the formation of α-hydroxytamoxifen.
Methods. Metabolism studies were performed in vitro using female rat liver microsomes. The effects of genistein and an isoflavone mixture on tamoxifen metabolism and the inhibition mechanism were determined using standard kinetic analysis, preincubation, and selective chemical inhibitors of P450.
Results. Metabolism of tamoxifen was saturable with K m values of 4.9 ± 0.6, 14.6 ± 2.2, 25 ± 5.9 μM and V max values of 34.7 ± 1.4, 297.5 ± 19.2, 1867 ± 231 pmol min−1 mg−1 for α-hydroxylation, N-desmethylation, and N-oxidation, respectively. Genistein (25 μM) inhibited α-hydroxylation at 2.5 μM tamoxifen by 64% (p < 0.001) but did not affect the 4-hydroxylation, N-desmethylation, and N-oxidation. A combination of three (genistein, daidzein, and glycitein) to five isoflavones (plus biochanin A and formononetin) inhibited tamoxifen α-hydroxylation to a greater extent but did not decrease the formation of identified metabolites. The inhibition on α-hydroxylation by genistein was mixed-typed with a K i , value of 10.6 μM. Studies using selective chemical inhibitors showed that tamoxifen α-hydroxylation was mainly mediated by rat CYP1A2 and CYP3A1/2 and that genistein 3`-hydroxylation was mainly mediated by rat CYP1A2, CYP2C6 and CYP2D1.
Conclusions. Genistein and its isoflavone analogs have the potential to decrease side effects of tamoxifen through metabolic interactions that inhibit the formation of α-hydroxytamoxifen via inhibition of CYP1A2.
Similar content being viewed by others
References
V. C. Jordan, S. Gapstur, and M. Morrow. Selective estrogen receptor modulation and reduction in risk of breast cancer, os-teoporosis, and coronary heart disease. J. Natl. Cancer Inst. 93: 1449–1457 (2001).
J. L Perez-Gracia and E. M Carrasco. Tamoxifen therapy for ovarian cancer in the adjuvant and advanced settings: systematic review of the literature and implications for future research. Gy-necol. Oncol. 84:201–209 (2002).
R. C Bergan, E. Reed, C. E Myers, D. Headlee, O. Brawley, H. K. Cho, W. D. Figg, A. Tompkins, W. M. Linehan, D. Kohler, S. M Steinberg, and M. V. Blagosklonny. A Phase II study of high-dose tamoxifen in patients with hormone-refractory prostate can-cer. Clin. Cancer Res. 5:2366–2373 (1999).
E. Pukkala, P. Kyyronen, R. Sankila, and K. Holly. Tamoxifen and toremifene treatment of breast cancer and risk of subsequent endometrial cancer: a population-based case-control study. Int. J. Cancer 100:337–341 (2002).
S. Shibutani, A. Ravindernath, N. Suzuki, I. Terashima, and S. M. Sugarman. A. P Grollman, M. L. Pearl. Identification of tamoxi-fen-DNA adducts in the endometrium of women treated with tamoxifen. Carcinogenesis 21:1461–1467 (2000).
D. H. Phillips. Understanding the genotoxicity of tamoxifen? Carcinogenesis 22:839–849 (2001).
I. N. White. Anti-oestrogenic drugs and endometrial cancers. Toxicol. Lett. 120:21–29 (2001).
A. Umemoto, K. Komaki, Y. Monden, M. Suwa, Y. Kanno, M. Kitagawa, M. Suzuki, C. X. Lin, Y. Ueyama, M. A. Momen, A. Ravindernath, and S. Shibutani. Identification and quantification of tamoxifen-DNA adducts in the liver of rats and mice. Chem. Res. Toxicol 14:1006–1013 (2001).
S. Shibutani, P. M. Shaw, N. Suzuki, L. Dasaradhi, M. W. Duffel, and I. Terashima. Sulfation of alpha-hydroxytamoxifen catalyzed by human hydroxysteroid sulfotransferase results in tamoxifen-DNA adducts. Carcinogenesis 19:y2007–2011 (1998).
G. Milano, M. C. Etienne, M. Frenay, R. Khater, J. L. Formento, N. Renee, J. L. Moll, M. Francoual, M. Berto, and M. Namer. Optimized analysis of tamoxifen and its main metabolites in the plasma and cytosol of mammary tumors. Br. J. Cancer 55:509–512 (1987).
R. R. Reddel, L. C. Murphy, and R. L. Sutherland. Effects of biologically active metabolites of tamoxifen on the proliferation kinetics of MCF-7 human breast cancer cells in vitro. Cancer Res. 43:4618–4624 (1983).
S. M. Langan-Fahey, D. C. Tormey, and V. C. Jordan. Tamoxifen metabolites in patients on long-term adjuvant therapy for breast cancer. Eur. J. Cancer 26:883–888 (1990).
G. K. Poon, Y. C. Chui, R. McCague, P. E. Linning, R. Feng, M. G. Rowlands, and M. Jarman. Analysis of phase I and phase II metabolites of tamoxifen in breast cancer patients. Drug Metab. Dispos. 21:1119–1124 (1993).
C. Mani, H. V. Gelboin, S. S. Park, R. Pearce, A. Parkinson, and D. Kupfer. Metabolism of the antimammary cancer antiestro-genic agent tamoxifen. I. Cytochrome P-450-catalyzed N-demethylation and 4-hydroxylation. Drug Metab. Dispos. 21:645–656 (1993a).
C. Mani, E. Hodgson, and D. Kupfer. Metabolism of the anti-mammary cancer antiestrogenic agent tamoxifen. II. Cytochrome P-450-catalyzed N-demethylation and 4-hydroxylation. Drug Metab. Dispos. 21:657–661 (1993b).
D. J. Boocock, J. L. Maggs, I. N. White, and B. K. Park. α-hy-droxytamoxifen, a genotoxic metabolite of tamoxifen in the rat: identification and quantification in vivo and in vitro. Carcinogen-esis 20:153–160 (1999).
H. K. Crewe, L. M. Notley, R. M. Wunsch, M. S. Lennard, and E. M. Gillam. Metabolism of tamoxifen by recombinant human cy-tochrome P450 enzymes: formation of the 4-hydroxy, 4'-hydroxy and N-desmethyl metabolites and isomerization of trans-4-hydroxytamoxifen. Drug Metab. Dispos. 30:869–874 (2002).
M. Kurzer and X. Xu. Dietary Phytoestrogens. Annu. Rev. Nutr. 17:353–381 (1997).
D. F. Birt, S. Hendrich, and W. Wang. Dietary agents in cancer prevention: flavonoids and isoflavonoids. Pharmacol. Ther. 90: 157–177 (2001).
C. S. Yang, J. M. Landau, M. T. Huang, and H. L. Newmark. Inhibition of carcinogenesis by dietary polyphenolic compounds. Annu. Rev. Nutr. 21:381–406 (2001).
H. Wiseman. The therapeutic potential of phytoestrogens. Expert Opin. Investig. Drugs 9:1829–1840 (2000).
Y. Liu and M. Hu. Absorption and metabolism of flavonoids in the Caco-2 cell culture model and a perfused rat intestinal model. Drug Metab. Dispos. 30:370–377 (2002).
J. Chen, H. Lin, and M. Hu. Metabolism of flavonoids via enteric recycling: role of intestinal disposition. J. Pharmacol. Exp. Therap 304:1228–1235 (2003).
K. D. Setchell, N. M. Brown, P. Desai, L. Zimmer-Nechemias, B. E. Wolfe, W. T. Brashear, A. S. Kirschner, A. Cassidy, and J. E. Heubi. Bioavailability of pure isoflavones in healthy humans and analysis of commercial soy isoflavone supplements. J. Nutr. 131: 1362S–1375S (2001).
M. Hu, K. Krausz, J. Chen, X. Ge, J. Q. Li, H. L. Gelboinl, and F. J. Gonzalez. Identification of CYP1A2 the main isoform for the phase I hydroxylated metabolism of genistein and a prodrug converting enzyme of methylated isoflavones. Drug Metab. Dis-pos. 31:924–931 (2003).
S. E. Kulling, D. M. Honig, and M. Metzler. Oxidative metabo-lism of the soy isoflavones daidzein and genistein in humans in vitro and in vivo. J. Agric. Food Chem. 49:3024–3033 (2001).
E. S. Roberts-Kirchhoff, J. R. Crowley, P. F. Hollenberg, and H. Kim. Metabolism of genistein by rat and human cytochrome P450s. Chem. Res. Toxicol. 12:610–616 (1999).
S. E. Kulling, D. M. Honig, T. J. Simat, and M. Metzler. Oxidative in vitro metabolism of the soy phytoestrogens daidzein and genis-tein. J. Agric. Food Chem. 48:4963–4972 (2000).
K. M. Newton, D. S. Buist, N. L. Keenan, L. A. Anderson, and A. Z. LaCroix. Use of alternative therapies for menopause symp-toms: results of a population-based survey. Obstet. Gynecol. 100: 18–25 (2002).
M. J. Messina and C. L. Loprinzi. Soy for breast cancer survivors: a critical review of the literature. J. Nutr. 131:3095S–3108S (2001).
A. Brzezinski and A. Debi. Phytoestrogens: the “natural” selec-tive estrogen receptor modulators? Eur. J. Obstet. Gynecol. Re-prod. Biol. 85:47–51 (1999).
D. Carusi. Phytoestrogens as hormone replacement therapy: an evidence-based approach. Care Update Ob. Gyns 7:253–259 (2000).
F. Shen, X. Xue, and G. Weber. Tamoxifen and genistein syner-gistically down-regulate signal transduction and proliferation in estrogen receptor-negative human breast carcinoma MDA-MB-435 cells. Anticancer Res. 19:1657–1662 (1999).
V. Tanos, A. Brzezinski, O. Drize, N. Strauss, and T. Peretz. Synergistic inhibitory effects of genistein and tamoxifen on hu-man dysplastic and malignant epithelial breast cells in vitro. Eur. J. Obstet. Gynecol. Reprod. Biol. 102:188–194 (2002).
J. R. Okita, P. J. Castle, and R. T. Okita. Characterization of cytochromes P450 in liver and kidney of rats treated with di-(2-ethylhexyl) phthalate. J. Biochem. Toxicol. 8:135–144 (1993).
I. H. Segel. Enzyme Kinetics: Behavior and Analysis of Rapid Equilibrium and Steady-State Enzyme Systems. John Wiley and Sons, New York, 1975.
H. K. Crewe, S. W. Ellis, M. S. Lennard, and G. T. Tucker. Variable contribution of cytochromes P450 2D6, 2C9 and 3A4 to the 4-hydroxylation of tamoxifen by human liver microsomes. Biochem. Pharmacol. 53:171–178 (1997).
C. K. Lim, Z. X. Yuan, J. H. Lamb, I. N. White, F. De Matteis, and L. L. Smith. A comparative study of tamoxifen metabolism in female rat, mouse and human liver microsomes. Carcinogenesis 15:589–593 (1994).
C. Mani, R. Pearce, A. Parkinson, and D. Kupfer. Involvement of cytochrome P4503A in catalysis of tamoxifen activation and co-valent binding to rat and human liver microsomes. Carcinogenesis 15:2715–2720 (1994).
H. Doi, H. Iwasaki, Y. Masubuchi, R. Nishigaki, and T. Horie. Chemiluminescence associated with the oxidative metabolism of salicylic acid in rat liver microsomes. Chem. Biol. Interact. 140: 109–119 (2002).
W. G. Chung, C. S. Park, H. K. Roh, W. K. Lee, and Y. N. Cha. Oxidation of ranitidine by isozymes of flavin-containing mono-oxygenase and cytochrome P450. Jpn. J. Pharmacol. 84:213–220 (2000).
J. Schmider, D. J. Greenblatt, S. M. Fogelman, L. L. von Moltke, and R. I. Shader. Metabolism of dextromethorphan in vitro: in-volvement of cytochromes P450 2D6 and 3A3/4, with a possible role of 2E1. Biopharm. Drug Dispos. 18:227–240 (1997).
V. A. Eagling, J. F. Tjia, and D. J. Back. Differential selectivity of cytochrome P450 inhibitors against probe substrates in human and rat liver microsomes. Br. J. Clin. Pharmacol. 45:107–114 (1998).
Y. Masubuchi, E. Masuda, and T. Horie. Multiple mechanisms in indomethacin-induced impairment of hepatic cytochrome P450 enzymes in rats. Gastroenterology 122:774–783 (2002).
K. Kobayashi, K. Urashima, N. Shimada, and K. Chiba. Selec-tivities of human cytochrome P450 inhibitors toward rat P450 isoforms: study with cDNA-expressed systems of the rat. Drug Metab. Dispos. 31:833–836 (2003).
R. W. Wang, P. H. Kari, A. Y. Lu, P. E. Thomas, F. P. Guengerich, and K. P. Vyas. Biotransformation of lovastatin. IV. Identification of cytochrome P450 3A proteins as the major en-zymes responsible for the oxidative metabolism of lovastatin in rat and human liver microsomes. Arch. Biochem. Biophys. 290: 355–361 (1991).
Y. Ando, E. Fuse, and W. D. Figg. Thalidomide metabolism by the CYP2C subfamily. Clin. Cancer Res. 8:1964–1973 (2002).
M. G. Busby, A. R. Jeffcoat, L. T. Bloedon, M. A. Koch, T. Black, K. J. Dix, W. D. Heizer, B. F. Thomas, J. M. Hill, J. A. Crowell, and S. H. Zeisel. Clinical characteristics and pharmacokinetics of purified soy isoflavones: single-dose administration to healthy men. Am. J. Clin. Nutr. 75:126–136 (2002).
G. K. Poon, B. Walter, P. E. Lonning, M. N. Horton, and R. McCague. Identification of tamoxifen metabolites in human HepG2 cell line, human liver homogenate, and patients on long-term therapy for breast cancer. Drug Metab. Dispos. 23:377–382 (1995).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Chen, J., Halls, S.C., Alfaro, J.F. et al. Potential Beneficial Metabolic Interactions Between Tamoxifen and Isoflavones via Cytochrome P450-mediated Pathways in Female Rat Liver Microsomes. Pharm Res 21, 2095–2104 (2004). https://doi.org/10.1023/B:PHAM.0000048202.92930.61
Issue Date:
DOI: https://doi.org/10.1023/B:PHAM.0000048202.92930.61