Identification and characterization of a novel CYP2C9 allelic variant in a warfarin-sensitive patient

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From: Pharmacogenomics(Vol. 16, Issue 13)
Publisher: Future Medicine Ltd.
Document Type: Report
Length: 6,232 words
Lexile Measure: 1670L

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Author(s): Da-Peng Dai aff1 , Chuan-Bao Li aff2 , Shuang-Hu Wang aff3 , Jie Cai aff4 , Pei-Wu Geng aff3 , Yun-Fang Zhou aff3 , Guo-Xin Hu aff4 , Jian-Ping Cai [*] aff1

Keywords:

allelic variants; CYP2C9; drug metabolism; in vitro functional assessment

Warfarin is a commonly prescribed oral anticoagulant used worldwide for the prevention of thromboembolic events. It has been proven effective with a lower cost than other anticoagulant drugs. However, its dosing is complicated and needs constant clinical follow-up to achieve its therapeutic effect due to its narrow therapeutic index and high interindividual variability in the anticoagulation response [1-3 ]. Many clinical and environmental factors, such as age, gender, BMI, vitamin K intake, comorbidities and comedications have been recognized to influence the dose of warfarin necessary for therapeutic anticoagulation. Genetic polymorphisms are estimated to account for approximately 35-50% of the inconsistency in warfarin requirements [4 ]. Polymorphisms of CYP P450 2C9 (CYP2C9 ) and vitamin K epoxide reductase complex subunit 1 (VKORC1 ) are the major genetic determinants involved in the metabolism of warfarin in humans. In addition, nucleotide changes in another CYP member, CYP4F2 , also show a marginally significant effect on warfarin dosing [5 ].

Warfarin is administered as a racemic mixture of R - and S -enantiomers with the S -isomer being three- to five-times more potent than its antipode [6 ]. CYP2C9 is the primary enzyme that metabolizes S -warfarin and two allelic variants, CYP2C9*2 and *3 , that are well known to be greatly responsible for the increased warfarin sensitivity in Caucasians. Individuals who are heterozygous or mutant homozygous (*1/*2, *1/*3, *2/*2, *2/*3, *3/*3 ) are found to require significantly lower doses of warfarin than the dose required for wild-type *1/*1 patients [1,7 ]. Additional variations in the CYP2C9 gene are also important, such as the CYP2C9*5, *6, *8 and *11 alleles occur predominantly in African populations and are known as to necessitate the lower warfarin doses in persons of African ancestry [ 8,9 ]. Recent large scale genetic polymorphism analysis revealed that CYP2C9*3 is the most common defective allele in the Chinese Han population [ 10,11 ], and other CYP2C9 allelic variants are also reported to be related to the low-dose requirement in Chinese populations, such as CYP2C9*13 and CYP2C9*58 [12,13 ]. In this study, we reported a novel variant, CYP2C9*60 , in a warfarin-sensitive patient and performed the functional assessment of its in vitro enzymatic characteristics toward three CYP2C9-specific substrates. Our data suggest that the newly found point mutation in CYP2C9 can not only decrease the protein expression capacity in both yeast and insect cell microsomes but also significantly reduce the enzymatic activity of CYP2C9 protein both in vitro and in vivo .

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Chemicals & materials

The TIANamp Blood DNA Midi Kit was obtained from TIANGEN (Beijing, China). The PrimeSTAR HS DNA polymerase and the restriction enzymes were purchased from Takara Bio, Inc. (Otsu, Shiga, Japan). The CEQ DTCS Quick Start Sequencing Kit was obtained from Beckman Coulter, Inc. (CA, USA). The rabbit polyclonal anti-CYP2C9 antibody was purchased from AbD Serotec (Oxford, UK). The mouse monoclonal anti-OR antibody...

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Gale Document Number: GALE|A428515776