title: Role of human cytochrome P450 3A4 in metabolism of medroxyprogesterone acetate.
abstract: Medroxyprogesterone acetate (MPA) is a drug commonly used in endocrine therapy for advanced or recurrent breast cancer and endometrial cancer. The drug is extensively metabolized in the intestinal mucosa and in the liver. Cytochrome P450s (CYPs) involved in the metabolism of MPA were identified by using human liver microsomes and recombinant human CYPs. In this study, the overall metabolism of MPA was determined as the disappearance of the parent drug from an incubation mixture. The disappearance of MPA in human liver microsomes varied 2.6-fold among the 18 samples studied. The disappearance of MPA in the same panel of 18 human liver microsomes was significantly correlated with triazolam alpha-hydroxylase activity, a marker activity of CYP3A (r = 0.764; P < 0.001). Ketoconazole, an inhibitor of CYP3A4, potently inhibited the disappearance of MPA in 18 human liver microsomes. Anti-CYP3A antibody also inhibited 86% of the disappearance of MPA in human liver microsomes. Although sulfaphenazole (an inhibitor of CYP2C9) and S-mephenytoin (an inhibitor of CYP2C19) partially inhibited the disappearance of MPA, no effect of the anti-CYP2C antibody was observed. The disappearance of MPA did not correlate with either the activity metabolized via CYP2C9 (diclofenac 4'-hydroxylase activity) or the activity metabolized via CYP2C19 (S-mephenytoin 4'-hydroxylase activity). Among the 12 recombinant human CYPs (CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C18, CYP2C19, CYP2D6, CYP2E1, CYP3A4, and CYP3A5) studied, only CYP3A4 showed metabolic activity of MPA. These results suggest that CYP3A4 is mainly involved in the overall metabolism of MPA in human liver microsomes.
authors.affiliation: Laboratory of Biochemical Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, Chiba University, Japan. kaoruk@p.chiba-u.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Kobayashi
authors.forename: N
authors.initials: N
authors.lastname: Mimura
authors.forename: H
authors.initials: H
authors.lastname: Fujii
authors.forename: H
authors.initials: H
authors.lastname: Minami
authors.forename: Y
authors.initials: Y
authors.lastname: Sasaki
authors.forename: N
authors.initials: N
authors.lastname: Shimada
authors.forename: K
authors.initials: K
authors.lastname: Chiba
mesh_terms: D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D018931:Antineoplastic Agents, Hormonal / Q000378:metabolism*; D016367:Baculoviridae / Q000201:enzymology / Q000235:genetics; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007313:Insecta / Q000201:enzymology / Q000821:virology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D007654:Ketoconazole / Q000494:pharmacology; D017258:Medroxyprogesterone Acetate / Q000378:metabolism*; D008617:Mephenytoin / Q000494:pharmacology; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D013426:Sulfaphenazole / Q000494:pharmacology
chemical_list: D000906:Antibodies; D018931:Antineoplastic Agents, Hormonal; D065607:Cytochrome P-450 Enzyme Inhibitors; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D011994:Recombinant Proteins; C400322:cytochrome P-450 CYP2C subfamily; D013426:Sulfaphenazole; D003577:Cytochrome P-450 Enzyme System; D017258:Medroxyprogesterone Acetate; D006899:Mixed Function Oxygenases; C104464:CYP3A protein, human; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D008617:Mephenytoin; D007654:Ketoconazole