Cell and molecular biology of gastrointestinal tract cancer.

The gene for familial adenomatous polyposis coli (APC or FAP), which has previously been linked to chromosome 5q21 has been identified. The APC gene has been found to be altered by point mutations in the germ line of both adenomatous polyposis coli and Gardner's syndrome patients and somatically in tumors from sporadic colorectal cancer patients. During the hunt for the APC gene, the closely linked MCC (mutated in colorectal cancer) gene was identified and found to be altered somatically in tumors from sporadic cancer patients. These data suggest that more than one gene on chromosome 5q21 may contribute to colorectal carcinogenesis and that mutations at the APC gene can cause both adenomatous polyposis coli and Gardner's syndrome. The identification of these genes should aid in the counseling of patients with genetic predispositions to colorectal cancer. Progress has also been made in identifying specific genetic changes that occur in other gastrointestinal cancers. A mutational "hotspot" in the p53 gene in human hepatocellular carcinomas has been identified that could reflect exposure to a specific carcinogen, one candidate being aflatoxin B1.