[Mutation of hMLH1 and hMSH2 genes in hereditary nonpolyposis colorectal cancer: analysis of 76 probands].

Objective: To investigate the mutations of the mismatch repair genes hMLH1 and hMSH2 in hereditary nonpolyposis colorectal cancer (HNPCC).

Methods: The DNA samples of 76 probands of HNPCC families underwent PCR amplification and sequencing on 35 exons in hMLH1 and hMSH2 genes.

Results: (1) The overall mutation rate of the hMLH1 and hMSH2 genes was 33% (25/76). (2) 22 mutations were found, 16 in the hMLH1 gene and 6 in the hMSH2 gene. (3) The spectrum of mutation type included frame shift, nonsense, splice site, and missense mutations. Missense mutation was the most common mutation type.

Conclusion: The hMLH1 and hMSH2 mutations in Chinese HNPCC families show a wide spectrum. It seems that hMLH1 gene is involved more frequently than hMSH2 gene. A certain number of HNPCC families can be benefited from the genetic screening for mutation of the mismatch repair genes.