Null polymorphism of the GSTM1 and GSTT1 genes in susceptibility to colorectal tumorigenesis: systematic review with meta-analysis

Objective: To assess if GSTT1 and GSTM1 null polymorphisms increase susceptibility to colorectal cancer. Methods: A search was conducted in PubMed, SciELO, BVS, and Medline databases. Forty articles were selected, totaling 12,698 cases and 19,517 controls. Odds ratios with 95% confidence intervals were used, and p-values <0.05 were considered significant. The Dersimonian-Laird method was applied for p-values <0.05, and the Mantel-Haenszel method was used otherwise. All p-values were two-tailed with an alpha value of 0.05 determined a priori. STATA 16.0 software was utilized. Result: A higher risk of colorectal cancer was shown in the general population for the GSTM1 null genotype (OR=1.11; 95%CI [1.03, 1.19]; P<0.01). No significant risk was observed for GSTT1 or the GSTM1/GSTT1 null combination (OR=1.09; 95%CI [0.98, 1.22]; P<0.01 and OR=1.13; 95%CI [0.89, 1.43]; P<0.01, respectively). In subgroup analysis, increased colorectal cancer risk was found for Asians with the GSTM1 null genotype (OR=1.10; 95%CI [1.02, 1.20]; P=0.02) and GSTM1/GSTT1 null combination (OR=1.49; 95%CI [1.03, 2.15]; P<0.01). Conclusion: The findings suggest that the GSTM1 null polymorphism and the GSTM1/GSTT1 null combination are potential susceptibility factors for colorectal cancer, particularly in the Asian population.