DNA content and chromatin texture of benzo[a]pyrene-transformed human breast epithelial cells as assessed by image analysis.

DNA content and chromatin supraorganization defined in terms of patterns of chromatin texture were studied by image analysis in Feulgen-stained human breast MCF-10F epithelial cells expressing different stages of tumorigenic progression after treatment with benzo[a]pyrene (BP). Nontransformed MCF-10F, nontumorigenic transformed BP1, and tumorigenic BP1-E1 cell lines were analyzed. A relationship between changes in DNA content and chromatin texture and the expression of different stages of tumorigenesis were researched in interphase nuclei. A significant decrease in Feulgen-DNA amounts and absorbing areas suggesting aneuploidy, and first detected in nontumorigenic transformed BP1 cells, became more relevant in the tumorigenic cell line BP1-E1. Simultaneously, an increase in optical densities and a change in related parameters, demonstrating increased chromatin higher order packing states, occurred in transformed BP1 cells and extended over larger chromatin areas in tumorigenic BP1-E1 cells. The results indicate loss of DNA and a change in chromatin higher order packing states accompanying the expression of different stages of the in vitro tumorigenesis process in BP-transformed human breast epithelial cells. It is suspected that the gradually acquired chromatin "condensation" supraorganization pattern is associated with activated transcription activities previously suggested for these cells. Copyright 1998 Academic Press.