Objective To investigate the correlation between the expression of MLH1 and p53 proteins and KRAS gene mutation status in colorectal cancer.

Methods The clinical data of 60 CRC patients diagnosed by pathology were selected, and the patients underwent KRAS gene testing. The expression levels of MLH1 and p53 were detected by immunohistochemistry, and the correlation between the expression of MLH1 and p53 proteins and KRAS gene mutation status were analyzed.

Results Among the 60 patients, the mutation rate of KRAS gene was 50.00% (30/60), and the risk of mutation in exon 2 was the highest, accounting for 41.67%. The negative expression rate of MLH1 index in CRC tissues was 51.67% (31/60), and the positive expression rate of p53 index in CRC tissues was 66.67% (40/60). Among them, the expressions of MLH1 and p53 were related to the lymph node metastasis and tumor differentiation degree of CRC (P ＜ 0.05). The KRAS gene mutation status in CRC patients was positively correlated with the negative expression of MLH1 protein (P ＜ 0.05), but the correlation with the expression of p53 protein was not statistically significant (P ＞ 0.05). The correlation in the GEPIA database showed that the expression of MLH1 mRNA in CRC tissues was positively correlated with that of KRAS mRNA (P ＜ 0.05). The survival rate after disease progression in patients with negative expression of CRC MLH1 was significantly lower than that in patients with positive expression (P ＜ 0.05).

Conclusions The negative expression of MLH1 protein is related to the progression and poor prognosis of CRC, and is expected to become a target for CRC treatment and a prognostic evaluation indicator.