The G<i>⁵¹⁶</i>T <i>CYP2B6</i> Germline Polymorphism Affects the Risk of Acute Myeloid Leukemia and Is Associated with Specific Chromosomal Abnormalities

Abstract

<div><p>The etiology of acute myeloid leukemia (AML) underlies the influence of genetic variants in candidate genes. The CYP2B6 enzyme detoxifies many genotoxic xenobiotics, protecting cells from oxidative damage. The <i>CYP2B6</i> gene is subjected to a single-nucleotide polymorphism (G<i>⁵¹⁶</i>T) with heterozygotes (<i>GT</i>) and homozygotes (<i>TT</i>) presenting decreased enzymatic activity. This case-control study aimed to investigate the association of <i>CYP2B6</i> G<i>⁵¹⁶</i>T polymorphism with the susceptibility of AML and its cytogenetic and clinical characteristics. Genotyping was performed on 619 AML patients and 430 healthy individuals using RCR-RFLP and a novel LightSNip assay. The major finding was a statistically higher frequency of the variant genotypes (<i>GT</i> and <i>TT</i>) in patients compared to the controls (<i>GT</i>:38.8% vs 29.8% and <i>TT</i>:9.3% vs 5.3% respectively) (<i>p</i><0.001). More specifically, a significantly higher frequency of <i>GT+TT</i> genotypes in <i>de novo</i> AML patients (46.6%) and an immensely high frequency of <i>TT</i> in secondary AML (<i>s</i>-AML) (20.5%) were observed. The statistical analysis showed that the variant T allele was approximately 1.5-fold and 2.4-fold higher in <i>de novo</i> and s-AML respectively than controls. Concerning FAB subtypes, the T allele presented an almost 2-fold increased in AML-M2. Interestingly, a higher incidence of the <i>TT</i> genotype was observed in patients with abnormal karyotypes. In particular, positive correlations of the mutant allele were found in patients carrying specific chromosomal aberrations [-7/del(7q), -5/del(5q), +8, +21 or t(8;21)], complex or monosomal karyotypes. Finally, a strikingly higher frequency of <i>TT</i> genotype was also observed in patients stratified to the poor risk group. In conclusion, our results provide evidence for the involvement of the <i>CYP2B6</i> polymorphism in AML susceptibility and suggest a possible role of the <i>CYP2B6</i> genetic background on the development of specific chromosomal aberrations.</p></div