Purpose: We studied the relation of breast cancer to common deletion mutations in GSTM1 and GSTT1 and the functional Ile(105)Val polymorphism in GSTP1 in a large, population-based case-control study conducted in China and performed a meta-analysis to summarize the literature.
Experimental design: In the case-control study, a total of 1144 breast cancer cases and 1221 community controls were genotyped for GSTM1, GSTP1, and GSTT1 using PCR-based methods. Associations of genotypes and breast cancer were evaluated in logistic regression models. Meta-analysis odds ratios (ORs) were estimated using a fixed effects model.
Results: In the case-control study, associations were null for GSTM1 [age-adjusted OR 0.97, 95% confidence interval (CI): 0.82-1.14] and GSTT1 (OR 0.97, 95% CI: 0.83-1.15). A significant increase in risk was observed among homozygotes for the variant Ile(105)Val polymorphism (OR 1.92, 95% CI: 1.21-3.04). No combined effects of GSTM1, GSTP1, and GSTT1 genotypes or interactions with potential effect modifiers were detected. All results were similar in pre- and postmenopausal women and for early versus advanced stage breast cancer. The meta-analysis, based predominantly on Caucasian women, supported null results for the homozygous deletion variant in GSTM1 (summary OR 1.05; combining 19 studies) and GSTT1 (summary OR 1.11; 15 studies). Meta-analysis results for the homozygous GSTP1 variant indicated no overall association (summary OR 1.04; 10 studies), although results varied significantly across studies (P = 0.009).
Conclusions: This large case-control study provides strong support for earlier studies showing no overall association of the GSTM1 and GSTT1 deletion polymorphisms with breast cancer risk. The GSTP1 variant may be relevant to breast cancer risk in Asian populations.