Comparison of sensitivity to arsenic compounds between a Bhas 42 cell transformation assay and a BALB/c 3T3 cell transformation assay.

A short-term cell transformation assay has recently been developed, using Bhas 42 cells which were established from BALB/c 3T3 cells transfected by v-Ha-ras gene and postulated to be initiated in the two-stage carcinogenesis theory. The Bhas 42 cell transformation assay has been reported to be capable of detecting initiating and promoting activities of chemical carcinogens, according to the different protocols, initiation assay and promotion assay, respectively. The assay is superior to classical transformation assays in cost and labor performance. The present study was carried out to compare its sensitivity with that of a classical BALB/c 3T3 cell system. We performed the Bhas 42 cell transformation assay with inorganic arsenic compounds which are potent environmental carcinogens in human but not mutagens in bacteria or weak mutagens in mammalian cells in vitro. Sodium arsenite, disodium arsenate, and their metabolites, monomethylarsonic acid and dimethylarsinic acid (DMAA) were included in the study. Sodium arsenite was positive in the initiation assay and all compounds except for DMAA were positive in the promotion assay. These results were compared with reported data in a two-stage BALB/c 3T3 cell transformation assay. The sensitivity of Bhas 42 cell transformation assay was found to be similar to that of the conventional BALB/c 3T3 cell transformation assay for the detection of initiating activities of arsenic compounds. For the detection of promoting activities, its sensitivity was equivalent to that of the two-stage BALB/c 3T3 cell transformation assay where the target cells were initiated with sub-threshold dose of 3-methylcholanthrene, confirming that Bhas 42 cells behave as initiated cells in the transformation assay.