Application of the improved BALB/c 3T3 cell transformation assay to the examination of the initiating and promoting activities of chemicals: the second interlaboratory collaborative study by the non-genotoxic carcinogen study group of Japan.

The Non-genotoxic Carcinogen Study Group in the Environmental Mutagen Society of Japan organised the second step of the inter-laboratory collaborative study on one-stage and two-stage cell transformation assays employing BALB/c 3T3 cells, with the objective of confirming whether the respective laboratories could independently produce results relevant to initiation or promotion. The method was modified to use a medium consisting of DMEM/F12 supplemented with 2% fetal bovine serum and a mixture of insulin, transferrin, ethanolamine and sodium selenite, at the stationary phase of cell growth. Seventeen laboratories collaborated in this study, and each chemical was tested by three to five laboratories.

Verification of the BALB/c 3T3 cell transformation assay after improvement by using an ITES-medium.

We carried out the first-step verification study on our ITES-medium-improved BALB/c 3T3 cell transformation assay. In order to estimate its potential use as a short-term screening method for putative carcinogens, 31 chemicals were tested in the improved transformation assay. The test chemicals consisted of 18 carcinogens and 13 noncarcinogens.