BCL-6 prevents mammary epithelial apoptosis and promotes cell survival

Proliferation, differentiation and apoptosis are essential processes in the normal functions of the mammary epithelium. The hypothesis examined in this study is that BCL-6 is critically important not only for regulating B cell growth and development, but also for influencing mammary epithelial apoptosis.

Full length BCL-6 cDNA was retrovirally transduced into EpH-4 cell line. We used flow cytometry of BrdUrd-stained cells to investigate the cell cycle duration of control and transduced cells. TUNEL was used as a marker of apoptosis to find out differences in the frequencies of apoptotic cells in control and transduced cells.

Restoration of human BCL-6 into EpH4 cells not only inhibits apoptosis, but also prolongs the cell cycle. The results also indicated that the cell cycle time of BCL-6-transduced EpH4 cells was prolonged by about 3 hours. We found differences in the frequencies of viable and apoptotic cells in cultures of the parent EpH4 cells, control transduced EpH4 cells and BCL-6-transduced EpH4 cells.

The results suggest that BCL-6 may be involved in mammary growth or mammary gland cell kinetics, but not in mammary gland development.