Expression and significance of mismatch repair genes hMLH1 and hMSH2 in sporadic colorectal carcinoma

Objective To investigate the expression and clinical significance of mismatch repair genes hMLH1 and hMSH2 in sporadic colorectal carcinoma tissues. Methods The expression of hMLH1and hMSH2 proteins was detected in the 63 sporadic colorectal carcinoma samples by immunohistochemical staining, including tumor tissue,adjacent tissue at 3 cm from the carcinoma, and normal tissue at 10 cnm away from the tumor. Results The positive rate of hMLH1 protein expression in the 63 normal colorectal tissues, adjacent tissues and sporadic colorectal carcinoma tissues was 95.2%, 85.7% and 81.0%,respectively. The positive rate of hMLH1 protein expression was significantly lower in the tumor than in normal colorectal tissues （ P 〈 0.05 ）. The positive rate of hMSH2 protein in the 63 normal colorectal tissues, adjacent tissues and sporadic colorectal carcinoma tissues were 76.2%, 66.7% and 52.4%,respectively. The positive rate of hMSH2 protein expression was significantly lower in the tumor than in normal colorectal tissues （P 〈 0.01 ）. The positive rate of hMLH1 protein expression was significantly higher in the tumor tissue of patients aged younger than 60 years （ 100% ） than that in patients ≥ 60 years（75.0%,P 〈0.05） . The positive rate of hMLH1 protein expression in the tumor tissue accompanied by lymphatic metastasis was 50.0%, significantly lower than that （ 93.3% ） in tumors without lymphatic metastasis （ P 〈0.05）. The positive rate of hMSH2 protein expression in the tumor tissue of patients aged younger than 60years was 80. 0%, significantly higher than that （43.8%） in the cases ≥ 60 years （ P 〈 0.05 ）. The positive rate of hMSH2 protein expression in the tumor tissues with invasion reaching to the intestinal serosa （61.5%） was significantly higher than that （ 37.5% ） in the tumors invading to submucosa or muscular layer （P 〈 0.05 ）. There was a positive correlation between the expressions of hMLH1 and hMSH2 proteins in the sporadic colorectal carcinomas. Conclusion There is a certain loss of expression of hMLH1 and hMSH2 proteins in sporadic colorectal carcinoma,and is correlated with the age of patients, lymphatic metastasis and different depth of cancer invasion. HMLH1 and hMSH2 may be used as a useful laboratory marker in clinical judgement of occurance and development of sporadic colorectal carcinoma. Key words: Sporadic colorectal carcinoma;  hMLH1 gene;  hMSH2 gene; Immunohistochemistry