BALB/c 3T3 cell transformation assays for the assessment of chemical carcinogenicity

In vitro cell transformation assays have been proposed for predicting the carcinogenic potential of chemicals. Morphological transformation can be induced by exposing mammalian cells to carcinogens. The cellular and molecular processes involved in cell transformation in the cultures are assumed to be similar to those of in vivo carcinogenesis. BALB/c 3T3 is an established cell line transformable with genotoxic and nongenotoxic carcinogens and produce foci in the cultures which lose the property of contact-inhibition of growth. We can perform a two-stage cell transformation assay which mimics a two-stage carcinogenicity test in experimental animals. In the two-stage cell transformation assay, a tumor promoter is identified if a test chemical enhances cell transformation by exposure of cells in the promotion stage following a known carcinogen (a tumor initiator) in the initiation stage; initiating activity of a chemical is tested by post-treatment of cells with a known tumor promoter in the promotion stage. The BALB/c 3T3 cell transformation assay has been modified by several research groups to improve its performance including sensitivity, reliability, assay period and cost. Recently a short-term cell transformation assay has been developed using the v-Ha-ras-transfected cell line, Bhas 42.