The black turtle bean (BTB) is most widely consumed legume all over the world having anticancer activity. The aim of the study was to analyse the apoptotic effects of BTB extracts on human breast cancer cell lines. Plant extract was prepared by homogenization and centrifugation. The cytotoxic effects of BTB was evaluated by MTT assay and their apoptotic effects were characterized by DNA fragmentation, nuclear staining assay, mitochondrial membrane potential analysis, annexin-V FITC and caspase 3/7 activity assay. The changes in cell cycle and gene expression of cell lines were analysed by flow cytometry and qRT-PCR, respectively. BTB extract showed cytotoxicity with IC50 values of 50 μg/ml in MCF-7 and MDA-MB231 cells. The caspase 3/7 was activated in the cancer cells treated with BTB extract leading to cell death by apoptosis. Moreover, there was significant increase in the expression of Bax as well as decrease in the Bcl-2 and Bcl-xL expression with in a dose dependent manner in both cells. It induces cell cycle arrest in S and G2/M phase in MCF-7 and MDA-MB231 cells, respectively. The mitochondrial membrane potential was decreased in BTB treated cells thereby transducing the apoptotic signal through the mitochondrial pathway and it also causes DNA fragmentation. Thus, it can be concluded that BTB induces the apoptosis in MCF-7 and MDA-MB-231 cells through intrinsic and extrinsic pathway and can be explored further for promising candidate to combat breast cancer. BTB extract exhibit anti-cancer activity by inducing apoptosis in breast cancer cell lines.
Keywords: AnnexinV-FITC; Apoptosis; Bcl-2 family proteins; Black turtle beans (Phaseolus vulgaris) extract; Caspase 3/7; Cell cycle arrest; Mitochondrial membrane potential.