title: Non-synonymous single nucleotide alterations found in the CYP2C8 gene result in reduced in vitro paclitaxel metabolism.
abstract: By sequencing genomic DNA from 73 established cell lines derived from Japanese individuals, we detected 9 single nucleotide polymorphisms (SNPs) in the CYP2C8 gene. Of them, 3 exonic SNPs resulted in amino acid alterations (g416a, R139K; a1196g, K399R; c1210g, P404A). The first two alterations were detected concurrently in one cell line and thought to be the same as CYP2C8*3. To examine the effects of these amino acid alterations on CYP2C8 function, wild-type and four types of variant CYP2C8 cDNA constructs (R139K, K399R, R139K/K399R and P404A) were transfected into Hep G2 cells and their paclitaxel 6a-hydroxylase activities were determined in vitro. Km values were not significantly different from that of the wild-type in any of the variants studied. The variant R139K/K399R showed reduced values for Vmax and clearance (Vmax/Km) similar to those of its single variant, R139K. The variant P404A also showed a significantly lowered clearance due to reduced level of protein expression. These results suggest that not only the double variant (R139K/K399R, CYP2C8*3) but also our novel variant P404A in the CYP2C8 gene are less efficient in paclitaxel metabolism.
authors.affiliation: Project Team for Pharmacogenetics, National Institute of Health Sciences, Tokyo, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Soyama
authors.forename: Y
authors.initials: Y
authors.lastname: Saito
authors.forename: N
authors.initials: N
authors.lastname: Hanioka
authors.forename: N
authors.initials: N
authors.lastname: Murayama
authors.forename: O
authors.initials: O
authors.lastname: Nakajima
authors.forename: N
authors.initials: N
authors.lastname: Katori
authors.forename: S
authors.initials: S
authors.lastname: Ishida
authors.forename: K
authors.initials: K
authors.lastname: Sai
authors.forename: S
authors.initials: S
authors.lastname: Ozawa
authors.forename: J I
authors.initials: JI
authors.lastname: Sawada
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D000972:Antineoplastic Agents, Phytogenic / Q000378:metabolism; D001189:Aryl Hydrocarbon Hydroxylases; D002460:Cell Line; D065727:Cytochrome P-450 CYP2C8; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D017239:Paclitaxel / Q000378:metabolism*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000972:Antineoplastic Agents, Phytogenic; 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