title: CYP2C8 polymorphisms in Caucasians and their relationship with paclitaxel 6alpha-hydroxylase activity in human liver microsomes.
abstract: Published cDNA sequences suggest the existence of non-synonymous single nucleotide polymorphisms in the cytochrome P450 CYP2C8. To determine whether these polymorphisms could be confirmed in a Caucasian population and to investigate whether additional polymorphisms occur in the coding and upstream regions of this gene, we screened for previously described and for novel polymorphisms using PCR-RFLP and SSCP analysis. We confirmed the existence of two of the previously detected polymorphisms which give rise to the amino acid substitutions I264M and K399R, respectively, but failed to detect three others in our population. We also confirmed that a recently identified polymorphism (R139K) is linked to K399R (CYP2C8*3) in our study population. The allele frequencies for the I264M (CYP2C8*4 allele) and the CYP2C8*3 allele were 0.075 and 0.15, respectively. Three novel polymorphisms (T-370G, C-271A and T1196C/L390S) were also detected with the upstream polymorphisms showing allele frequencies of 0.061 and 0.196, respectively, but the L390S polymorphism detected only in a single subject. An additional single subject was heterozygous for a polymorphism recently described in African-Americans (A805T; CYP2C8*2 allele). The functional significance of the two upstream polymorphisms and the CYP2C8*3 and CYP2C8*4 alleles was investigated in human liver microsomes. Samples heterozygous for CYP2C8*3 showed significantly lower paclitaxel 6alpha-hydroxylase activity compared with wild-type samples. Median activity associated with CYP2C8*4 also appeared lower than the wild-type but the difference was not significant. There was no evidence that either upstream polymorphism gave rise to altered CYP2C8 expression.
authors.affiliation: Department of Pharmacological Sciences, University of Newcastle Medical School, Framlington Place, NE2 4HH, Newcastle upon Tyne, UK.
authors.forename: Namrata
authors.initials: N
authors.lastname: Bahadur
authors.forename: Julian B S
authors.initials: JB
authors.lastname: Leathart
authors.forename: Elaine
authors.initials: E
authors.lastname: Mutch
authors.forename: Dorothy
authors.initials: D
authors.lastname: Steimel-Crespi
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Dunn
authors.forename: Ron
authors.initials: R
authors.lastname: Gilissen
authors.forename: Jos Van
authors.initials: JV
authors.lastname: Houdt
authors.forename: Jan
authors.initials: J
authors.lastname: Hendrickx
authors.forename: Geert
authors.initials: G
authors.lastname: Mannens
authors.forename: Hilde
authors.initials: H
authors.lastname: Bohets
authors.forename: Faith M
authors.initials: FM
authors.lastname: Williams
authors.forename: Martin
authors.initials: M
authors.lastname: Armstrong
authors.forename: Charles L
authors.initials: CL
authors.lastname: Crespi
authors.forename: Ann K
authors.initials: AK
authors.lastname: Daly
mesh_terms: D000595:Amino Acid Sequence; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics* / Q000378:metabolism; D065727:Cytochrome P-450 CYP2C8; D018076:DNA, Complementary / Q000032:analysis; D006801:Humans; D008862:Microsomes, Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D017239:Paclitaxel / Q000378:metabolism*; D020641:Polymorphism, Single Nucleotide; D018807:Polymorphism, Single-Stranded Conformational; D017386:Sequence Homology, Amino Acid; D044465:White People / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D001189:Aryl Hydrocarbon Hydroxylases; C450259:CYP2C8 protein, human; D065727:Cytochrome P-450 CYP2C8; D017239:Paclitaxel