Parasporin A13-2 of Bacillus thuringiensis isolate from Papaloapan region, induce a cytotoxic effect by late apoptosis against breast cancer cells

Abstract The protein A13-2 was obtained from Bacillus thuringiensis strains isolated from the Papaloapan watershed region (Oaxaca, Mexico). The cytotoxic activity of parasporal inclusions was studied against breast cancer cell line (MCF-7) and normal cell (human peripheral blood mononuclear cells). The MTT, the formation of reactive species, nitric oxide, free cell DNA, and the type of death cellular were assessed. The protein A13-2 shows the highest cytotoxic activity against MCF-7 (13% at 6 µg/mL), the extracellular DNA increases, and it shows no stress for reactive species or nitric oxide. Besides, the A13-2 parasporin shows no toxicity to peripheral blood mononuclear cells, and it does not generate changes in nitric oxide levels or free cell DNA. According to microscopy and flow cytometry, A13-2 leads to the death of MCF-7 cell by late apoptosis. Due to that, the cytotoxic effect of A13-2 was specific for MCF-7, and it does not affect peripheral blood mononuclear cells (normal cells). When analyzed together, our results show for the first time that the A13-2 protein isolated from Mexican strains of B. thuringiensis has a high selectivity against the MCF- 7 cell line, thus representing a promising alternative for the treatment of cancer breast.