MDM2 and colorectal carcinoma: Significant heterogeneity was observed in the association analysis between the MDM2 SNP309 polymorphism and CRC risk in the overall populations in all comparisons (GG vs. TT: PQ = 0.000; GT vs. TT: PQ = 0.000; GG+ GT vs. TT: PQ = 0.000; GG vs. GT+ TT: PQ = 0.000; Table 3).