Quantitative analysis of BRCA1, BRCA2 and Hmsh2 mRNA expression in colorectal Lieberkühnien adenocarcinomas and matched normal mucosa: relationship with cellular proliferation.

The human DNA mismatch repair gene hMSH2 is involved in the development of sporadic and hereditary nonpolyposis colorectal cancer. An increased risk of colorectal cancer has also been suggested in BRCA1 and BRCA2 mutation carriers. To address the relationship between the expression level of these genes and colorectal tumorigenesis, we studied BRCA1, BRCA2 and hMSH2 mRNA expression by real-time quantitative RT-PCR in 72 colorectal Lieberkühnien adenocarcinomas and matched normal mucosa. We investigated the relationship between mRNA levels and various clinicopathological parameters. The mean expression of BRCA1 3' and BRCA2 3' (mRNA pool), BRCA1 ex11 (with exon 11), BRCA2 ex12 (with exon 12) and hMSH2 mRNAs were increased in tumor samples. BRCA1 and BRCA2 mRNAs expressions were altered according to colon tumor site: BRCA1 3' and BRCA2 3' mRNAs levels were highest, respectively, in the right colon and left colon. No difference in hMSH2 mRNA levels was detected in relation to clinicopathological parameters. The mean SPF value was significantly higher in tumor than in non-tumor colonic tissue, and a high SPF value was correlated with high BRCA2 mRNA levels. BRCA2 3' mRNA levels tended to decrease as the Dukes' stage increased. In conclusion, the mechanisms of colorectal carcinogenesis seem to differ according to the right or left position of the tumor.