CYP3A4, CYP3A5 and POR*28 genotyping in kidney transplantation patients taking Tacrolimus : an insight on the Lebanese population

Abstract

Introduction: Tacrolimus is an immunosuppressive drug belonging to the calcineurin inhibitor group as an important therapeutic alternative to cyclosporine following organ transplantation. Its use is highly efficient at preventing rejection in heart, pancreas, bone marrow, lung, liver, and kidney transplantation. Once absorbed, it is metabolized by different enzymes of the cytochrome P450 family, and mainly CYP3A4 and CYP3A5 in the liver and the intestinal cells. POR gene is also involved in Tacrolimus metabolism since it affects the activity level of CYPs including CYP3A. Differences in immunosuppressive effects on patients taking the same Tacrolimus dose is due to modifications in the pharmacokinetics of the drug. Studies showed the presence of important SNPs like CYP3A4*2,*4,*12 and 4*18. In addition to CYP3A5*2,*4,*6,*7 and POR*28. Their effect on Tacrolimus metabolism and consequently on the dose required to maintain a stable immunosuppression, showed contradicting results. Experimental procedure: The purpose of this study is to find the frequency of genotypes associated with these nine polymorphisms among Lebanese kidney transplant patients, and to compare them with that of the Caucasian population. We also aim to study any possible correlation between these SNPs and Tacrolimus metabolism based on its concentration in blood. Blood samples from 81 patients were collected from St. George Hospital University Medical Center (SGHUMC). DNA was extracted from these samples, and genotyping for these SNPs was performed using PCR-RFLP and TaqMan Real-time q PCR. Statistical analysis was performed to study any correlation between the genotypes and Tacrolimus metabolism. Results: The results showed 100% frequencies for CYP3A4*2 and 4*18 A/A genotype, for CYP3A4*4 and 5*4 T/T genotype and for CYP3A4*12 G/G genotype. Additionally, the frequency of CYP3A5*2 G/G genotype, the one of CYP3A5*6 C/C genotype and the frequency of CYP3A5*7 -/- genotype were 100% (n=81). While the frequency of POR*28 C/C genotype was 52% (n=42), and that of C/T genotype was 48% (n=39). Analysis of Tacrolimus concentrations and daily doses didn't show any significant difference between patients of different genotype groups. Statistical analysis showed that the confounders had no effect on blood Tacrolimus concentrations. Conclusion: The frequency of the mutant alleles in the Lebanese population is similar as in Caucasian population. The nine SNPs of CYP3A4, CYP3A5 and POR genes didnt have any influence on Tacrolimus metabolism or its concentration in blood.