In vitro transformation of rat pleural mesothelial cells by chrysotile fibres and/or benzo[a]pyrene.

Rat pleural mesothelial cells (RPMC) were treated, in vitro, in a two-stage model of carcinogenesis. RPMC obtained from passage 12th were treated once with 1 microgram/ml of benzo-[a]pyrene (BP) and from passage 13th to 40th with 0.4 microgram/cm2 of chrysotile fibres (Chr). Transformation was determined by the observation of the colonies formed when the cells were plated at low density. Colonies were classified into four classes according to the level of lack in contact inhibition between cells (0 to III). BP as well as chrysotile fibres were potent in inducing a high proportion of type III colonies which were not observed in control series. In addition, there was no synergistic effect between BP and Chr. These results would indicate that chrysotile fibres do not act as a promoter on rat pleural mesothelial cells in culture, but induce morphologically transformed colonies.