Somatic alterations of the DPC4 gene in human colorectal cancers in vivo

Background & Aims: The chromosome region 18q21 has been shown to be frequently deleted in colorectal cancers, and such frequent allelic loss is a hallmark of the presence of a tumor-suppressor gene. The DPC4 gene, which is located at 18q21, has been identified as a tumor-suppressor gene from examination of pancreatic cancers. The aim of the present study was to determine if it might also be altered in colorectal cancers. Methods: Mutation analyses of the DPC4 gene were performed on complementary DNA samples from 31 primary colorectal cancer specimens using a combination of polymerase chain reaction, single-strand conformation polymorphism, and DNA sequencing. Results: Four missense mutations producing amino acid substitutions and a somatic 12-base pair deletion in the coding region of the DPC4 gene were detected in the 31 cancers (16%; 5 of 31). Conclusions: The DPC4 gene may play a role as a tumor-suppressor gene in a fraction of colorectal cancers; however, while allelic loss at 18q21 is very often seen in colorectal cancers, only a minority show DPC4 mutations, suggesting that there might be another tumor-suppressor gene in this chromosome region.