Abstract
When transfected to benzo[a]pyrene (BP)‐transformed MCF‐10F human breast epithelial 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 aggressive tumorigenic cell line, BP1‐Tras. We have previously demonstrated by image analysis that BP affects the DNA content and the chromatin supraorganization of MCF‐10F cells. Here Feulgen‐stained BP1‐Tras cells were studied by image analysis in order to evaluate possible additional changes in DNA content and chromatin texture induced by insertion of the ras oncogene. A high variability in DNA content also including polyploidy or near‐polyploidy, and an increase in the packing states of the chromatin which became still condensed in BP1 cells were found in BP1‐Tras cells. The results differed from those reported for the BP1‐E1 cell line which is also an aggressive tumorigenic cell line, but was attained through progressive passages of BP‐transformed cells. It was demonstrated that different patterns of changes in DNA content and chromatin organization may be involved in equally aggressive tumorigenic BP‐transformed cell lines originated from the same cell line by different mechanisms.
Highlights
The MCF-10 cell line has been reported as the first spontaneous line of cultured breast epithelium for which there is direct evidence that the normal diploid chromosome pattern of the explanted tissues was retained for over a year of growth culture [14]
Image analysis results for BP1-Tras cells indicated a wide variability in their Feulgen-DNA values, reflected by respective standard deviation (SD) values (Figs 1 and 2; Table 1) and differing from the situation reported with the advancing tumorigenesis steps from BP1 to BP1-E1 cells, when the Feulgen-DNA values shifted to smaller integrated optical densities (IOD) values [17]
Aggressive tumorigenic phenotypes have been found to be attained by different mechanisms in human breast epithelial cells, MCF-10F
Summary
The MCF-10 cell line has been reported as the first spontaneous line of cultured breast epithelium for which there is direct evidence that the normal diploid chromosome pattern of the explanted tissues was retained for over a year of growth culture [14]. This cell line gave rise to MCF-10A and MCF-10F cells [14]. Immortal human breast epithelial cells, MCF-10F, which exhibit characteristics of normal cells [14], have been successfully transformed in vitro with benzo[a]pyrene, giving rise to several cell lines (BP1, BP1-E, BP1-E1, among others) [3]. The subsequent steps of the neoplastic process in the BP-transformed MCF10F cells have been reported to involve the action of other genes [2,19,20,22]
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