Genetic polymorphisms in GSTM1, -P1, -T1, and CYP2E1 and the risk of adult brain tumors
Cytochrome P-450 CYP2E1
GST and CYP2E1 genes are involved in metabolism of several compounds (e.g., solvents) that may play a role in brain cancer etiology. We evaluated associations between polymorphisms in these genes and adult brain tumor incidence. Cases were 782 patients with brain tumors diagnosed from 1994 to 1998 at three United States hospitals. Controls were 799 patients admitted to the same hospitals for nonmalignant conditions. DNA was extracted from blood samples that had been collected from 1277 subjects (80% of all subjects; 604 controls; 422 gliomas, 172 meningiomas, and 79 acoustic neuromas), and genotyping was successfully conducted for GSTM1 null, GSTT1 null, GSTP I105V, GSTP A114V, CYP2E1 RsaI, and CYP2E1 Ins96. The GSTP1 105 Val/Val genotype was associated with increased glioma incidence [odds ratio (OR), 1.8; 95% confidence limits (CLs), 1.2, 2.7], with the estimated effect following a trend of increasing magnitude by number of variant alleles (Ile/Ile: OR, 1.0; Ile/Val: OR, 1.3; Val/Val: OR, 2.1). The CYP2E1 RsaI variant was weakly associated with glioma (OR, 1.4; 95% CL, 0.9, 2.4) and acoustic neuroma (OR, 2.3; 95% CL, 1.0, 5.3), with some indication of stronger associations among younger subjects. Estimated effects of the gene variants differed by glioma subtype. There was evidence of supermultiplicativity of the joint effect of GSTP1 I105V and CYP2E1 RsaI variants on both glioma and acoustic neuroma, even following adjustment of estimates toward a common prior distribution using hierarchical regression models. Previously reported associations between the GSTT1 null genotype and overall glioma incidence were not replicated, but an association with meningioma was observed (OR, 1.5; 95% CL, 1.0, 2.3). These findings may provide clues to both genetic and environmental determinants of brain tumors.