Clues to the pathogenesis of familial colorectal cancer.

A predisposition to colorectal cancer is shown to be linked to markers on chromosome 2 in some families. Molecular features of "familial" cancers were compared with those of sporadic colon cancers. Neither the familial nor sporadic cancers showed loss of heterozygosity for chromosome 2 markers, and the incidence of mutations in KRAS, P53, and APC was similar in the two groups of tumors. Most of the familial cancers, however, had widespread alterations in short repeated DNA sequences, suggesting that numerous replication errors had occurred during tumor development. Thirteen percent of sporadic cancers had identical abnormalities and these cancers shared biologic properties with the familial cases. These data suggest a mechanism for familial tumorigenesis different from that mediated by classic tumor suppressor genes.