Cell proliferation and colonic neoplasia.

The preneoplastic events occurring in the mucosa of patients at risk of developing colonic cancer are described and correlate well with the histogenesis of an adenoma. Confirmatory evidence from experimental carcinogenesis systems is provided. Among individuals at 50% risk of colon cancer, proliferative abnormalities relating to the distribution of S-phase cells are present. Aging, whether among the high-risk or the unaffected control population, appears to bring about enhancement of the percentage of DNA-synthesizing cells in the crypts, indicating a similar response of colonic epithelial cells to environmental conditions over time. The combination of an already existing defect in cell proliferation among those at high risk of familial colon cancer along with an elevated rate of cell renewal increases the probability that a neoplasm will arise in this population.