Human breast cancer cell death induced by BnSP-6, a Lys-49 PLA₂ homologue from Bothrops pauloensis venom

This work shows the antitumoral effects of BnSP-6, a Lys 49 PLA2 isolated from Bothrops pauloensis venom, on human breast cancer MDA-MB-231 cells. BnSP-6 caused a dose-dependent cytotoxicity and inhibited cell adhesion. Interestingly, cytotoxic activity of BnSP-6 was significantly lower against MCF10A, a non-tumorigenic breast cell line, suggesting that this PLA2 presented a possible preference for targets in cancer cells. Analysis of cell death on MDA-MB-231 cells showed that BnSP-6 stimulated the autophagy process, as evidenced by labeling of autophagic vacuoles. Moreover, apoptosis assays showed that BnSP-6 induced both early and late apoptosis. Apoptosis of MDA-MB-231 cells was also confirmed by up-regulation of different genes related to the apoptosis pathway, such as TNF, TNFRSF10B, TNFRSF1A and CASP8 and decreased expression of anti-apoptotic genes (BCL2 and BCL2L). In addition, BnSP-6 caused a remarkable increase in gene expression of BRCA2 and TP53 tumor suppressors. Finally, BnSP-6 induced down-regulation of Angiopoetin 1 gene (potent pro-angiogenic factor) and inhibited adhesion and migration of MDA-MB-231 cells suggesting pharmaceutical applications of this PLA2 as an antiangiogenic and anti-metastatic agent. Taken together, our results show that the PLA2 BnSP-6 presents anticancer potential that can be exploited as prototype for the design of new therapies.