Expression of BC l-2 and BAX proteins in breast cancer after in vivo tamoxifen administration Expressão das proteínas BCL-2 e BAX no câncer de mama após administração in vivo de tamoxifeno

ABstr ACt Despite the presence of estrogen receptor in breast cancer cells, some patients do not show benefits on their treatment with tamoxifen, which is a medication that interferes on cell cycle promoting apoptosis. Since BCL-2 and BAX proteins are directly linked to this process, it is important to understand which pathways for cell death are related to and interfered by tamoxifen. Paired samples of breast cancer tumors, which were previously obtained before and after tamoxifen therapy were randomly divided in the Control and Treated Patients Groups. The Treated Group received tamoxifen for 14 days (20 mg/day). The immunohistochemical identification of BAX and BCL-2 expression was analyzed in a semi-quantitative scale considering the number of positive cells and intensity of staining. The scores of each reaction were compared pre and post–treatment and to the Control Group. Over the 25 patients studied, considering no exposure to the drug, there were 36 (9/25) and 72% (18/25) of positive cases for BCL-2 and BAX, respectively. This study showed no significant changes over BCL-2 and BAX proteins expression after 14 days of treatment with tamoxifen (p > 0,05) compared to the control patients. Expression of BCL-2 and BAX proteins did not suffer statistically significant changes after a 14-day exposure to tamoxifen. This is one of a few prospective randomized double-blind studies about in vivo effects of tamoxifen in apoptosis.