Mutational analysis of transforming growth factor beta receptor type II and DNA mismatch repair genes in sporadic endometrial carcinomas with microsatellite instability.

To clarify how microsatellite instability (MI) is involved in carcinogenesis of sporadic endometrial carcinoma, we examined mutations of the transforming growth factor beta receptor type II (TGF beta RII) gene in 32 patients with MI-positive sporadic endometrial carcinoma. Moreover, mutations of 4 DNA mismatch repair (MMR) genes (hPMS1, hPMS2, hMLH1, hMSH2), which are considered to cause MI, were investigated as well. With respect to the TGF beta RII gene, mutations in the 10-bp polyadenine repeat sequence were observed in 7 of 29 informative cases (24%). Concerning MMR genes, a T to C point mutation at the -6 intronic splice acceptor site of exon 13 of hMSH2 was detected in 43% (6/14). However, there was no mutation in any exon of these 4 MMR genes. These results suggest that there is a carcinogenic mechanism via mutation of the TGF beta RII gene in some cases of MI-positive sporadic endometrial carcinoma. It seems unlikely that the unknown MMR genes are responsible for MI. The implication of the mutation at the intronic splice acceptor site in hMSH2 remains to be clarified.