CYP3A4 and CYP3A5 are metabolizing enzymes abundantly expressed in liver and involved in the metabolism of xenobiotics as well as clinically used drugs. Genetic polymorphisms in CYP3A4 and CYP3A5 may alter the metabolic ability of individuals. Thus, CYP3A4 and CYP3A5 might play an important role in the aetiology of chronic myeloid leukaemia (CML) and as modulators of cancer therapy response. In this study, the impact of two single nucleotide polymorphisms (SNPs) CYP3A4*18 (878T>C) and CYP3A5*3 (6986A>G) on CML susceptibility risk was investigated. This case-control study involved a total of 520 study subjects comprising 270 CML patients and 250 normal healthy controls. Genotyping of CYP3A4*18 and CYP3A5*3 was performed by polymerase chain reaction – restriction fragment length polymorphism (PCR-RFLP) technique. The association between allelic variants and CML susceptibility risk was assessed by logistic regression analysis, deriving odds ratio (OR) with 95% confident intervals. The results showed that heterozygous (*1/*1*8) genotype of CYP3A4*18 was significantly associated with CML susceptibility risk (OR 3.387; 95% CI: 1.433–8.007, p = 0.005). No homozygous variant (*18/*18) genotype was detected in this study. On the contrary, homozygous variant (*3/*3) and heterozygous (*1/*3) genotypes of CYP3A5*3 were associated with significantly lower risk for CML susceptibility (OR 0.140; 95% CI: 0.079–0.246’ p < 0.001 and OR 0.310; 95% CI: 0.180–0.535, p < 0.001, respectively). The results prompt us to conclude that genetic variation in CYP3A4*18 may contribute to a higher risk whereas CYP3A5*3 polymorphism confers a lower susceptibility risk in Malaysian CML patients.

Chronic myeloid leukaemia (CML) provides an illustrative disease model for both molecular pathogenesis of cancer and rational drug therapy. Imatinib mesylate (IM), a BCR-ABL1 targeted tyrosine kinase inhibitor (TKI) drug, is the first line gold standard drug for CML treatment. Conventional cytogenetic analysis (CCA) can identify the standard and variant Philadelphia (Ph) chromosome, and any additional complex chromosome abnormalities at diagnosis as well as during treatment course. Fluorescence in situ hybridization (FISH) is especially important for cells of CML patients with inadequate or inferior quality metaphases or those with variant Ph translocations. CCA in conjunction with FISH can serve as powerful tools in all phases of CML including the diagnosis, prognosis, risk stratification and monitoring of cytogenetic responses to treatment. Molecular techniques such as reverse transcriptase-polymerase chain reaction (RT-PCR) is used for the detection of BCR-ABL1 transcripts at diagnosis whereas quantitative reverse transcriptase-polymerase chain reaction (qRTPCR) is used at the time of diagnosis as well as during TKI therapy for the quantitation of BCR-ABL1 transcripts to evaluate the molecular response and minimal residual disease (MRD). Despite the excellent treatment results obtained after the introduction of TKI drugs, especially Imatinib mesylate (IM), resistance to TKIs develops in approximately 35% - 40% of CML patients on TKI therapy. Since point mutations in BCR-ABL1 are a common cause of IM resistance, mutation analysis is important in IM resistant patients. Mutations are reliably detected by nested PCR amplification of the translocated ABL1 kinase domain followed by direct sequencing of the entire amplified kinase domain. The objective of this review is to highlight the importance of regular and timely CCA, FISH analysis and molecular testing in the diagnosis, prognosis, assessment of therapeutic efficacy, evaluation of MRD and in the detection of BCR-ABL1 kinase mutations which cause therapeutic resistance in adult CML patients.