Screening for carcinogens by the DNA synthesis inhibition test using human fibroblasts

The Ames test has probably been the most common prescreening test for potential carcinogens. This system, however, occasionally presents false-positive or false-negative results for certain kinds of chemicals. We chose 24 agents, most of which showed a discrepancy in their results with the animal carcinogenicity test and the Ames test, and screened them by the DNA synthesis inhibition test using human fibroblasts. Among 22 agents, 13 (59%) showed consistent results, 6 (27%) showed discrepant results with those obtained by animal tests and 3 (14%) showed ambiguous results. The majority of the DNA synthesis inhibition test results for these chemicals were consistent with the results obtained by whole animal tests, suggesting that the DNA synthesis inhibition test with mammalian cells in culture is a reasonably reliable prescreening test for potential carcinogens.