Indução de morte em células MCF-7 e MDA-MB-435 tratadas com fração isolada do extrato de folhas de barbatimão

Abstract

The aim of the present work was to investigate the type of cell death induced in the MCF-7 (ER+) and MDA-MB-435 (ER-) human mammary carcinoma cell lineages by the fraction isolated from the barbatimão leaf extract. Stryphnodendron adstringens (Martius) Coville (Fabaceae) leaves were collected, dried and the acetone extract was prepared. It was partitioned with ethyl acetate and the remaining aqueous solution was lyophilized and fractioned by Sephadex LH 20 chromatography. The collected fractions were analyzed by thin layer chromatography and the fraction eluted with 100 % methanol was used in the experiments, because it showed the highest proanthocyanidin content. The HPLC analysis showed that the isolated fraction is composed by procyanidin dimmer B1, epigallocatechin-3-O-gallate and gallic acid. The MCF-7 (ER+) and MDA-MB-435 (ER-) cells were treated for 24 h with different concentrations of the fraction (5 – 160 μg/mL) and with 550 μg/mL cyclophosphamide. The cell treatment with the isolated fraction induced cell viability reduction and morphologic alterations in both cell lines, including cell typical shape loss, chromatin condensation and a decrease in the colony and cell area. The ED50 dose for MCF-7 cells was 12.35 μg/mL and the ED50 dose for MDA-MB-435 cells was 34.43 μg/mL, being the MCF-7 cells more sensitive to the fraction treatment. The Western blotting analysis showed that the fraction treatment induced an increase in the Bax and a decrease in the Bcl-2 cell expression that is indicative of apoptosis. There were also an increase in the caspase-9, caspase-3-active and caspase-8 expression and a decrease in the caspase-3 and pro-caspase-8 expression. These proteins are involved in induction of the intrinsic apoptosis pathway. It was also observed an increase in the expression of autophagy protein markers: LC-3 expression increased in both cell lines and beclin-1 expression increased only in the treated MDA-MB-435. The results of the present work allowed the conclusion that the isolated fraction from barbatimão leaf extract induced apoptotic death with autophagy in both cell lines, MCF-7 and MDA-MB-435. These results are important because it was demonstrated the cytotoxic effect and the ER- MDA-MB-435 cell death induction, besides the cytotoxicity to ER+ MCF-7 cells. As there is no a curative treatment for ER- mammary tumors as well as ER+ tumors in an advanced stage, the isolated fraction seems to be a promising candidate to a drug development for breast cancer treatment and prevention.