CYP2C9 polymorphism analysis in Han Chinese populations: building the largest allele frequency database

Abstract

Genetic polymorphisms of CYP2C9 significantly influence the pharmacokinetics and pharmacodynamics of some drugs, which might result in adverse drug effects and therapeutic failure. Several studies have been performed on CYP2C9 genetic polymorphisms in Han Chinese populations. However, these studies only focused on two commonly investigated alleles, *2 and *3, in relatively small sample sizes. To scale up the gene-scanning region and determine relatively precise data on the genetic distribution pattern in Chinese populations, unrelated healthy Han Chinese volunteers from Zhejiang Province (n=1127) and Hebei (n=1000) Province were recruited as subjects for the direct sequencing of all exons of CYP2C9. As a result, 14 previously reported alleles were detected in this work, and 8 of these alleles (*14, *16, *19, *23, *27, *29, *33 and *34) were described for the first time in Chinese populations. In addition, 37 novel mutations were also detected, of which 22 variants were non-synonymous, and 21 new alleles, *36-*56, were designated by the Human CYP Allele Nomenclature Committee. In vitro functional analysis of these 22 novel CYP2C9 variants revealed that 17 mutations had a significant influence on the protein's catalytic activity. Our study provides the most accurate data on CYP2C9 polymorphisms in Han Chinese populations and detects the largest number of novel allelic variants existing to date. These new alleles will greatly enrich the current knowledge of naturally occurring CYP2C9 variants in Chinese populations.

In Vitro Functional Assessment of 22 Newly Identified CYP2D6 Allelic Variants in the Chinese Population

“…Regarding the typical allelic variants CYP2D6.2 and CYP2D6.10, our data strongly accord with the majority of the previously reported results [15][16][17], although we have not provided the kinetic parameters of these variants. Similarly, previous reports have been revealed that the results obtained for another CYP member, CYP2C9, also are in well agreement with those from other expression systems [13]; thus, data of the present study might be constructive for the functional prediction of these newly found CYP2D6 variants.…”

“…Four different cDNA expression systems have been successfully used for the in vitro drug metabolism studies, including bacteria [22], yeast [23], insect cells [24] and mammalian cells [13]. Compared with other expression systems, mammalian cells have adequate endogenous OR and cytochrome b 5 to support CYP activities and are much closer to the inherent environment of human proteins; thus, it is much more relevant to assess the potential effects of recombinant human CYP variant proteins in the mammalian cell system [21].…”

“…The drug metabolic ability of each allelic variant was calculated according to the previously reported formula [13].…”

“…To express CYP proteins in mammalian cells, the dual-expression plasmid pIRES was used to simultaneously express the internal control protein Gluc and the target CYP protein. Similar to the previous reports [13,14], the open reading frame (ORF) of each CYP2D6 variants was obtained via the overlap extension PCR method using wild-type CYP2D6 as the amplification template. In detail, the upper part of the ORF region was amplified using…”

Identification and Functional Assessment of a New CYP2C9 Allelic Variant CYP2C9*59

“…This study was approved by the Institutional Ethical Committee of Beijing Hospital and informed written consent was obtained from the patient during blood sample collection. The genomic DNA extracted from the peripheral blood cells of the subject, using the TIANamp Blood DNA Midi Kit (TIANGEN, Beijing, China), was used for the polymerase chain reaction amplification of the promoters or exons of the CYP2C9, VKORC1, and CYP4F2 genes according to the methods reported previously (Yuan et al, 2005;Burmester et al, 2011;Dai et al, 2014). To avoid sequencing errors, bidirectional sequencing was performed for the putatively mutated sites.…”