Colon-cancer defect found.

Colon-cancer defect found

A genetic defect may be responsible for a large number of cases of colon and rectal cancers, according to British and Israeli scientists, who say the discovery could lead to improved diagnosis. Led by Walter F. Bodmer of the Imperial Cancer Research Fund Laboratories in London, the researchers reported this week that the loss of certain genes through mutations "may be a critical step in the progression of a relatively high proportion of colorectal cancers.'

When comparing cancerous material from the colon and rectum with normal tissue from similar sites, the scientists found that some genetic material was missing from chromosome 5 in at least 20 percent of the tumors. In a parallel study, the group located the gene for familial adenomatous polyposis (FAP) on the same chromosome. Found in certain families, FAP is characterized by the formation of numerous polyps in the colon, which frequently become malignant if not removed. On the basis of these two studies, the scientists suggest in the Aug. 13 NATURE that mutations in the FAP gene may be involved in both familial and nonfamilial forms of colorectal cancer. They also say that further research should provide methods for prenatal and presymptomatic diagnosis of a predisposition to colorectal cancers, which will add an estimated 145,000 new cases to U.S. cancer figures this year.