Do polymorphisms in MDR1 and CYP3A5 genes influence the risk of cytogenetic relapse in patients with chronic myeloid leukemia on imatinib therapy?

Influence of polymorphisms in the genes coding for imatinib transporters and metabolizing enzymes on cytogenetic relapse in patients with chronic myeloid leukemia (CML) is not known. One hundred and four patients (52 cases with cytogenetic relapse and 52 controls without relapse) with chronic-phase CML on imatinib therapy and have completed 5 years of follow-up were enrolled. The following single nucleotide polymorphisms (SNPs) were genotyped; C1236T, C3435T, G2677T/A in MDR1 gene and A6986G in CYP3A5 gene, using PCR-RFLP method and validated by direct gene sequencing. Imatinib trough levels were measured using LC-MS/MS. Patients with CC genotype for MDR1-C1236T polymorphism were at significantly higher risk for cytogenetic relapse [OR =4.382, 95% CI (1.145, 16.774), p = .022], while those with TT genotype for MDR1-C3435T polymorphism had significantly lower risk of relapse [OR =0.309, 95% CI (0.134, 0.708), p = .005]. Imatinib trough levels were lower in patients with relapse compared to those without relapse (1551.4 ± 1324.1 vs. 2154.2 ± 1358.3 ng/mL; p = .041). MDR1-C3435T genotype [adjusted-OR: 0.266; 95% CI (0.111, 0.636); p = .003] and trough levels (p = .014) were independent predictors of relapse in multivariate analysis. To conclude, C1236T and C3435T polymorphisms in MDR1 gene and trough levels significantly influence the risk of cytogenetic relapse. MDR1-C3435T genotype might emerge as a potential biomarker to predict the risk of cytogenetic relapse in patients with CML.