Pro-apoptotic and anti-adhesive effects of four African plant extracts on the breast cancer cell line MCF-7

Background: Jatropha curcas (JCP1), Pyrenacantha staudtii (PS), Picralima nitida (ZI) and Jatropha gossypifolia (JCP2) are plants used in the African folklore for the treatment of various cancers. Methods: This study investigated the in vitro anticancer effects of the ethanol extracts against human epithelial MCF-7 breast cancer cells in a dose-dependent manner (1-50 mu g/ml) by using cell cycle analysis, viability assay, annexin V/PI staining, TUNEL method and expression determination of apoptotic and adhesion relevant proteins. Adhesion processes were monitored by detachment via flow cytometry, beta 1-integrin expression and formation of the actin cytoskeleton. Results: The three extracts, termed PS, JCP1 and JCP2 at a concentration of 10 mu g/ml induced cell death in MCF-7 breast cancer cells verified by high amounts of PI-positive cells in the cell cycle analysis, Annexin V/PI staining and DNA fragmentation measurements. In parallel cell detachment was accompanied by decreased beta 1- integrin expression and phosphorylation of the focal adhesion kinase at Tyr397. ZI extract was the exception by the increasing beta 1-integrin expression and strengthening the cortical actin cytoskeleton. However, all four plant extracts mediated strong anti-cancer properties with IC50 values between 23-38 mu g/ml. Conclusion: PS, JCP1 and JCP2 were found to be very active against MCF-7 cells by inducing anoikis and therefore possessing vast potential as medicinal drugs especially in estrogen receptor positive breast cancer treatment. ZI mediated their anti-cancer action by different signaling mechanisms which should be analyzed in future studies. Our results further supported the idea that medicinal plants can be promising sources of putative anticancer agents.