Evaluation of chemopreventive agents for genotoxic activity.

We conducted genetic toxicity evaluations of 11 candidate chemopreventive agents with the potential for inhibiting carcinogenesis in humans at increased risk of cancer. The compounds were evaluated for bacterial mutagenesis in the Salmonella-E. coli assay, for mammalian mutagenesis in mouse lymphoma cells, for chromosome aberrations in Chinese Hamster Ovary (CHO) cells, and for micronucleus induction in mouse bone marrow. Tested agents were indole 3-carbinol (I3C), bowman-birk inhibitor concentrate (BBIC), black tea polyphenols (BTP), farnesol, geraniol, l-Se-methylselenocysteine (SeMC), 5,6-dihydro-4H-cyclopenta[1,2]-dithiol-3-thione(DC-D3T), 4'-bromoflavone, 2,5,7,8-tetramethyl-(2R-[4R,8R,12-trimethyltridecyl] chroman-6-yloxy) acetic acid (alpha-TEA), SR13668 (2,10-dicarbethoxy-6-methoxy-5,7-dihydro-indolo[2,3-b] carbazole and SR16157 (3-O-sulfamoyloxy-7alpha-methyl-21-(2-N,N-diethylaminoethoxy)-19-norpregna-1,3,5(10)-triene). All these agents, except I3C and BTP, were negative in the Salmonella-E. coli assay in the presence and absence of metabolic activation (S9). I3C and BTP induced a weak mutagenic response in the presence and absence of S9 with strains TA100 and TA98, respectively. Of the three compounds tested in the mouse lymphoma assay (I3C, BBIC, and BTP), only BTP was mutagenic in the presence of S9. In the chromosomal aberration assay, of the 8 compounds that were tested, 4'-bromoflavone elicited a positive response in the absence of S9 only, while SR16157 was positive in the presence of S9. The results with geraniol remain inconclusive. I3C, BBIC and BTP were not tested in the chromosomal aberration assay. None of the 11 agents induced micronuclei in mouse bone marrow erythrocytes.

Salmonella /Mammalian-Microsome Test to Detect Chemical Mutagens.

With few exceptions, chemical mutagens are carcinogens. A number of short-term microbial pre-screening procedures for detection of potential chemical mutagens are now available. One of these, the Salmonella /mammalian-microsome assay (Ames test), has proven to be highly reliable in predicting what chemicals are potential carcinogens. The test is designed primarily to identify which chemicals are mutagens, so that priorities can be established for further testing in long-term animal carcinogenicity studies. This report describes what the Salmonella test is, and how the test has been used as a tool to detect mutagens in our food and drinking water. The usefulness of the test in detecting mutagenic metabolites in human feces and urine is also discussed briefly.