Ha-ras oncogene effect on DNA content and chromatin supraorganization in benzo[a]pyrene-transformed human breast epithelial cells

When transfected to benzo[a]pyrene (BP)-transformed MCF-10F human breast ep ithelial cells (BP1 cell line) the c-Ha-ras oncogene has proven to enhance the neoplastic changes initiated by exposure to BP, giving rise to an aggre ssive tumorigenic cell line, BP1-Tras. We have previously demonstrated by i mage analysis that BP affects the DNA content and the chromatin supraorgani zation of MCF-10F cells. Here Feulgen-stained BP1-Tras cells were studied b y image analysis in order to evaluate possible additional changes in DNA co ntent and chromatin texture induced by insertion of the ras oncogene. A hig h variability in DNA content also including polyploidy or near-polyploidy, and an increase in the packing states of the chromatin which became still c ondensed in BP1 cells were found in BP1-Tras cells. The results differed fr om those reported for the BP1-E1 cell Line which is also an aggressive tumo rigenic cell Line, but was attained through progressive passages of BP-tran sformed cells. It was demonstrated that different patterns of changes in DN A content and chromatin organization may be involved in equally aggressive tumorigenic BP-transformed cell lines originated from the same cell line by different mechanisms.