BCL-2 EXPRESSION IN NORMAL BREAST-TISSUE DURING THE MENSTRUAL-CYCLE

bcl-2 is a proto oncogene discovered through the t(14;18) translocatio n occurring in most human follicular lymphomas. The function so far at tributed to bcl-2 is to counteract the occurrence of apoptosis and to prolong cell survival without affecting the cycling cells. Apoptosis h as been described in normal breast tissue epithelial cells, and it pea ks at the end of the luteal phase. We have studied bcl-2 expression by an immunohistochemical method in 50 samples of normal breast tissue d istributed throughout the menstrual cycle. bcl-2 staining predominated in the lobular epithelial cells. It displayed a striking cyclic varia tion, with maximal expression at the midcycle period and a sharp decre ase at the end of the cycle. These results strongly suggest that the r egulation of bcl-2 expression in breast tissue is hormone-dependent. T his could be of significance in tumorigenesis. (C) 1994 Wiley-Liss, In c.