Cytotoxic activity and mechanism of action of Smp43 scorpion peptide against colorectal cancer cell line HCT-116

Abstract

This study was conducted to extend our previous investigations to examine the cytotoxic efficacy of Smp43 scorpion peptide against colorectal cancer cell line (HCT-116) and revealing its molecular mechanisms of action. Using MTT assay, Smp43 significantly induced cytotoxic effects on HCT-116 cancer cells compared to normal colon epithelial cell line (FHC) of IC50 4.11 and 62.17 µg/ml, respectively. Flow cytometric apoptosis assay showed that IC50 (4.11 µg/ml) of Smp43 induced a remarkable increase in the proportion of HCT-116 cancer cells undergoing late apoptotic cell death. Also, Smp43 caused cell cycle arrest at the S phase. RT-PCR analysis showed highly significant downregulation of Bcl-2 anti-apoptotic gene and ki-67 proliferative markers in HCT-116 treated with IC50 of Smp43. In contrast, caspase-3, −8, −9, Bax, and p53 apoptotic genes were upregulated. Protein expression levels of caspase-3, −8, −9, and p53 were similarly elevated in treated cells using a western blot analysis. The apoptotic characteristics were also confirmed through scanning and transmission electron microscopy. The Smp43 treated HCT-116 cancer cells showed cell membrane blebbing, pore formation, heterochromatin condensation toward the nuclear envelope, leakage of cell organelles, and formation of apoptotic bodies. Consequently, Smp43 peptide provides a great starting point for creating effective cytotoxic agents against human colorectal cancer.