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CYP3A5 phenotype‐genotype correlations in a British population

2003; Wiley; Volume: 55; Issue: 6 Linguagem: Inglês

10.1046/j.1365-2125.2003.01798.x

1365-2125

Barry P. King, Julian Leathart, Elaine Mutch, Faith M. Williams, Ann K. Daly,

Drug Transport and Resistance Mechanisms

Aims To develop a polymerase chain reaction (PCR)‐restriction fragment length polymorphism (RFLP)‐based assay to genotype for hepatic CYP3A5 expression and to use this assay to study a British population. Methods CYP3A5‐specific PCR primers were designed with one including a base‐pair mismatch to create a Rsa I site in samples positive for A6986 ( CYP3A5 * 1 allele). Following PCR and Rsa I digestion, different band patterns on electrophoresis were predicted for individuals positive for CYP3A5 ( CYP3A5 * 1 allele) compared with those who do not express the gene ( CYP3A5 * 3 homozygotes). The assay was validated by DNA sequencing. DNA samples from a human liver bank consisting of 22 livers whose CYP3A5 expression had been determined by immunoblotting and a group of random individuals ( n = 100) from the North‐east of England were genotyped by the new assay. Results In the liver bank, five out of 22 samples expressed CYP3A5 at significant levels (>20 pmol mg −1 protein) and were found to have the genotype CYP3A5 * 1 / CYP3A5 * 3 by the PCR‐RFLP assay. All other liver DNA samples were CYP3A5 * 3 homozygotes. In the group of 100 random individuals, 13 had the genotype CYP3A5 * 1 / CYP3A5 * 3 and all others were CYP3A5 * 3 homozygotes, predicting that 13% (95% confidence interval (CI) 6%, 20%) would show significant hepatic CYP3A5 expression. The frequency for the CYP3A5 * 1 allele was 0.065 (95% CI 0.032, 0.097). Conclusions We have developed a simple assay for the detection of the CYP3A5 * 1 / CYP3A5*3 alleles and shown that in a British population their frequency is similar to that reported previously. We have also shown a good correlation between hepatic CYP3A5 expression and genotype for a British Caucasian liver bank.