Polyphenols purified from the Brazilian aroeira plant (Schinus terebinthifolius, Raddi) induce apoptotic and autophagic cell death of DU145 cells.

Polyphenols extracted from many plants have shown antiproliferative and antitumor activities in a wide range of carcinogenesis models. The antiproliferative effects of polyphenols purified from the Brazilian aroeira plant (Schinus terebinthifolius, Raddi) were investigated on the androgen-insensitive DU145 human prostatic carcinoma cell line. A F3 fraction purified from leaf extract inhibited the DU145 cell proliferation more than 30-fold compared to the crude extract. By flow cytometric analysis, the polyphenol fraction was demonstrated to induce G0/G1 cell growth arrest and cell apoptosis. This apoptosis was evidenced by caspase 3 stimulation in F3-treated cells as compared to crude extract treated cells. The acid phosphatase activity of lysosomes was strongly activated in the lysosomal fraction of the F3-treated DU145 cells. This lysosomal activation, together with the appearance of autophagic vacuoles, suggests that "type 2 physiological cell death" was also involved in this antiproliferative effect. HPLC analysis of this F3 fraction showed 18 different subfractions. Among these subfractions, F3-3, F3-7 and F3-13 strongly inhibited DU145 cell proliferation in a dose-dependent manner. However, the nature of these polyphenols remains unknown since only one (Isoquercitrin) of the tested pure polyphenols co-migrated with F3-13. Since lysosomotropic drugs are considered as possible regulators of lysosome activity, aroeira polyphenols could target lysosomes of prostatic cancer cells to induce autophagic cell death.