title: Polymorphisms in human CYP2C8 decrease metabolism of the anticancer drug paclitaxel and arachidonic acid.
abstract: Cytochrome P450 (CYP) 2C8 is the principal enzyme responsible for the metabolism of the anti-cancer drug paclitaxel (Taxol). It is also the predominant P450 responsible for the metabolism of arachidonic acid to biologically active epoxyeicosatrienoic acids (EETs) in human liver and kidney. In this study, we describe two new CYP2C8 alleles containing coding changes: CYP2C8*2 has an Ile269Phe substitution in exon 5 and CYP2C8*3 includes both Arg139Lys and Lys399Arg amino acid substitutions in exons 3 and 8. CYP2C8*2 was found only in African-Americans, while CYP2C8*3 occurred primarily in Caucasians. Neither occurred in Asians. The frequency of the CYP2C8*2 allele was 0.18 in African-Americans, and that of CYP2C8*3 was 0.13 in Caucasians. CYP2C8*1 (wild-type), CYP2C8*2 and CYP2C8*3 cDNAs were expressed in Escherichia coli, and the ability of these enzymes to metabolize both paclitaxel and arachidonic acid was assessed. Recombinant CYP2C8*3 was defective in the metabolism of both substrates. The turnover number of CYP2C8*3 for paclitaxel was 15% of CYP2C8*1. CYP2C8*2 had a two-fold higher Km and two-fold lower intrinsic clearance for paclitaxel than CYP2C8*1. CYP2C8*3 was also markedly defective in the metabolism of arachidonic acid to 11,12- and 14,15-EET (turnover numbers 35-40% that of CYP2C8*1). Thus, CYP2C8*3 is defective in the metabolism of two important CYP2C8 substrates: the anticancer drug paclitaxel and the physiologically important compound arachidonic acid. This polymorphism has important clinical and physiological implications in individuals homozygous for this allele.
authors.affiliation: Laboratories of Pharmacology and Chemistry and Pulmonary and Pathobiology, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA.
authors.forename: D
authors.initials: D
authors.lastname: Dai
authors.forename: D C
authors.initials: DC
authors.lastname: Zeldin
authors.forename: J A
authors.initials: JA
authors.lastname: Blaisdell
authors.forename: B
authors.initials: B
authors.lastname: Chanas
authors.forename: S J
authors.initials: SJ
authors.lastname: Coulter
authors.forename: B I
authors.initials: BI
authors.lastname: Ghanayem
authors.forename: J A
authors.initials: JA
authors.lastname: Goldstein
mesh_terms: D000483:Alleles; D000972:Antineoplastic Agents, Phytogenic / Q000493:pharmacokinetics*; D016718:Arachidonic Acid / Q000493:pharmacokinetics*; D001189:Aryl Hydrocarbon Hydroxylases; D002460:Cell Line; D065727:Cytochrome P-450 CYP2C8; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D005838:Genotype; D006801:Humans; D008657:Metabolic Clearance Rate; D017239:Paclitaxel / Q000493:pharmacokinetics*; D011110:Polymorphism, Genetic / Q000235:genetics*; D011994:Recombinant Proteins / Q000235:genetics / Q000493:pharmacokinetics; D017422:Sequence Analysis, DNA / Q000379:methods; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000235:genetics*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D011994:Recombinant Proteins; D016718:Arachidonic Acid; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C450259:CYP2C8 protein, human; D065727:Cytochrome P-450 CYP2C8; D039181:Steroid 16-alpha-Hydroxylase; D017239:Paclitaxel