Engineering BinB Pore-Forming Toxin for Selective Killing of Breast Cancer Cells

Breast cancer is one of the most common cancers in women worldwide. Conventional cancer chemotherapy always has adverse side effects on the patient's healthy tissues. Consequently, combining pore-forming toxins with cell-targeting peptides (CTPs) is a promising anticancer strategy for selectively destroying cancer cells. Here, we aim to improve the target specificity of the BinB toxin produced from Lysinibacillus sphaericus (Ls) by fusing a luteinizing hormone-releasing hormone (LHRH) peptide to its pore-forming domain (BinB(C)) to target MCF-7 breast cancer cells as opposed to human fibroblast cells (Hs68). The results showed that LHRH-BinB(C) inhibited MCF-7 cell proliferation in a dose-dependent manner while leaving Hs68 cells unaffected. BinB(C), at any concentration tested, did not affect the proliferation of MCF-7 or Hs68 cells. In addition, the LHRH-BinB(C) toxin caused the efflux of the cytoplasmic enzyme lactate dehydrogenase (LDH), demonstrating the efficacy of the LHRH peptide in directing the BinB(C) toxin to damage the plasma membranes of MCF-7 cancer cells. LHRH-BinB(C) also caused MCF-7 cell apoptosis by activating caspase-8. In addition, LHRH-BinB(C) was predominantly observed on the cell surface of MCF-7 and Hs68 cells, without colocalization with mitochondria. Overall, our findings suggest that LHRH-BinB(C) could be investigated further as a potential cancer therapeutic agent.