EFFECTS OF ESTROGEN ON APOPTOTIC PATHWAYS IN HUMAN BREAST-CANCER CELL-LINE MCF-7

We utilized a reverse transcription-PCR method to examine the effect o f estrogen on the expression of mRNA for Bcl-2 and Bax, two modulatory proteins in the apoptotic pathway, in human breast cancer cell line M CF-7. We found that the bcl-2 mRNA levels in the cells exposed to 17 b eta-estradiol were higher than those of control cells. Although the re lative bax mRNA levels remained unchanged, the changes in bcl-2 mRNA l evel occurred in a time- and concentration-dependent fashion. In addit ion, pretreatment with 17 beta-estradiol protected MCF-7 cells from ap optosis. Our study provides evidence that responses of breast epitheli al cells toward a steroid sex hormone involve regulation of the apopto tic pathway.