Genomic structure of the transforming growth factor beta type II receptor gene and its mutations in hereditary nonpolyposis colorectal cancers.

To characterize the tumorigenetic role of the transforming growth factor beta type II receptor (RII) gene, we defined its genomic structure, which consists of seven exons. The sequences of exon-intron junctions were determined to facilitate mutation analysis of each exon. Twenty-five carcinomas and five adenomas from hereditary nonpolyposis colorectal cancer patients were analyzed for mutations in the entire coding region. Four missense mutations (two in adenomas and two in carcinomas) were found in the 10 cases carrying the polyadenine deletions in one allele. These results indicate that RII shares the two-hit inactivation mechanism with tumor suppressor genes and that mutations of it may occur in the early stage of tumorigenesis.