Our results demonstrated that CIMP-high tumors were more likely to lose expression of MMR protein, especially MLH1 and PMS2. In addition, among the 24 CRC patients with MLH1 hypermethylation, 16 patients (66.7%) had loss of expression of MLH1. In the present study, all of the 26 patients (100%) with loss of expression of MLH1 had loss of expression of PMS2. The heterodimeric nature of the MMR proteins is possibly the reason to explain our findings. This evidence concerns the gene PMS2 and colorectal carcinoma.