Apoptosis and catastrophic cell death in benzo[a]pyrene-transformed human breast epithelial cells

Abstract Apoptosis and mitotic death, bi- and multinucleation, giant cells and micronucleation were investigated in human breast epithelial cell lines transformed by benzo[ a ]pyrene (BP) (BP1, BP1-E and BP1-E1 cells) and in BP1 cells transfected with the c-Ha- ras oncogene (BP1-T ras cells). Since BP induces apoptosis and the abnormal expression of ras genes elicits catastrophic mitosis, both cell death phenomena were expected to occur in this system, especially in BP1-T ras cells. Regardless of the cell line considered, single-nucleate cells were found to be eliminated preferentially through apoptosis, while bi- and multinucleate cells were eliminated through catastrophic mitosis. Apoptosis and catastrophic mitosis were observed in all cell lines but were significantly more frequent in BP1-T ras cells. The abnormal expression of Ha- ras in the latter cells may enhance in this system the effects of the BP apoptosis path reported for BP-transformed Hepa 1c1c7 hepatoma cells. Transfection with the ras oncogene also enhanced the mitotic disturbances, which produced multi- and micronucleation and mitotic death, possibly because of the genomic instability promoted by this oncogene in the BP-transformed cell line.