Cytotoxicity and Molecular Alterations Induced by Scorpion Venom Antimicrobial Peptide Smp43 in Breast Cancer Cell Lines MDA-MB-231 and MCF-7

Smp43 is a novel cationic antimicrobial peptide (AMP) which was extracted from the venom of Scorpio maurus palmatus scorpion. However, many studies described the cytotoxic activities of Smp43 on various cancer cell lines; cytotoxicity and its mode of action on human breast cancer remain unstudied. The purpose of this research is to determine the cytotoxicity and the molecular mechanisms of Smp43 in human breast cancer cell lines (MDA-MB-231 and MCF-7). Cells were treated with Smp43 and various assays have been performed including MTT assay, apoptosis assay (Annexin V/PI staining), cell cycle analysis, DNA fragmentation by DPA and agarose gel electrophoresis, and wound healing assay were performed. In addition, apoptosis-related gene expression levels were determined by qRT-PCR while the expression levels of cell proliferation/migration/invasion-related genes were determined by western blotting. Treatment with Smp43 inhibited cell proliferation, migration, and metastasis, but it induced cell apoptosis as observed by DNA fragmentation and Annexin V/PI analysis. Further molecular mechanism studies showed that bax, p53, caspase 7, and caspase 9 expression levels was found to be up regulated in both treated cell lines. On the other hand, bcl-2, ki67, PCNA, laminin-5, and upA expression levels significantly downregulated in both treated cell lines. These findings were also validated by ELISA test of cytochrome C, MMP9, and VEGF. Generally, our results revealed that proliferation of breast cancer cells is dramatically reduced in vitro by Smp43 through apoptosis induction and migration/invasion inhibition. Our findings provide new insights about antitumor activity of scorpion venom antimicrobial peptides and may lead to the development of effective therapeutic agents targeting breast cancer.