Short-term tests and long-term prospects for colon cancer prevention.

Five assay systems that have been used for identifying possible carcinogenic factors responsible for human colon cancer are described. These are: Salmonella, colonic micronuclei, colonic epithelial proliferation and aberrant crypt assays, and polyp recurrence trials. The assays have led to the development and testing of 7 hypotheses. A review of this process points to the importance of specificity in the assay system.