Flow-cytometrically monitored chromatin in situ testing in the breast cell line H184A1N4.

Previous investigations in human precancerous and cancerous tissues identified subsets of cells that were different in respect to a heparin-induced increase in fluorescence intensity (IFI) monitored by flow cytometry. We suggested that differences in IFI were due to different chromatin types in the cells and related to different transcriptional capacities. This study is to prove our suggestion. Heparin-induced IFI was measured in the human breast cell line H184A1N4 cultured under different, defined growth conditions. Cells in quiescence obtained from a culture deprived of serum and other supplements essential for growth or from the confluent state revealed a higher IFI than cells restimulated to proliferation by addition of complete medium; here a reduced IFI was found. Changes in the magnitude of heparin-induced IFI precede changes in cell-cycle stage distribution by at least 6.5 h. We conclude that the heparin-induced effects, as revealed by flow cytometry, reflect changes in the accessibility of chromatin to transcription in different stages of proliferative activity. The results confirm our conclusions from previous findings with clinical material.