BCL-6 is expressed in breast cancer and prevents mammary epithelial differentiation.

Appropriately timed proliferation, differentiation and apoptosis are essential to the normal functions of the mammary epithelium. Here, we report that the transcription factor BCL-6 is expressed in mammary epithelium in nonpregnant animals as well as during early pregnancy. When overexpressed in the nontransformed EpH4 mammary epithelial cell line, BCL-6 prevents the STAT-driven expression of the milk protein beta-casein and duct formation, and prevents apoptosis.