[The significance of Fas/FasL molecular system in breast cancer].

Fas (CD95/APO-1) and its natural ligand, FasL, are molecules expressed on cellular membranes, being involved in the induction of programmed cells death or apoptosis. Recently, it has been shown that malignant cells originating from solid tumors tend to inhibit the expression of Fas, as an escape mechanism from the immune cells' attack and to express FasL, as a counterstrike mechanism against the immune effector cells. The purpose of this study was to investigate, by immunohistochemistry, the presence of Fas and FasL in 15 breast carcinomas and to establish possible associations between the expression of these molecules and the histological type and grading of the tumors. Our results showed that 7 breast tumors have lost the expression of Fas and 11 tumors were positive for the Fas-ligand expression, important arguments for the mechanisms of immune escape and tolerance induction. Furthermore, 7 of the 11 FasL+ tumors were poorly differentiated invasive ductal carcinomas, suggesting a possible association between FasL expression and tumor aggressivity.