The Anticancer Effect of a Conjugated Antimicrobial Peptide Against Colorectal Cancer (CRC) Cells.

Abstract

Although antimicrobial peptides (AMPs) were initially known as compounds of the innate immune system to fight microbial pathogens, it has been recently proposed that differences in normal and cancer cell membranes cause the anticancer effect of these peptides. The aim of this study was to evaluate the anticancer effect of MELITININ+BMAP27-conjugated peptide against colorectal cancer (CRC) cells. The MELITININ+BMAP27-conjugated peptides were designed and the β-naphthylalanine residues were added to the termini to improve the anticancer effect. CRC cancer cell lines including HT29, SW742, HCT-116, and WiDr were used. After preparing concentrations of 5, 10, 25, 50, 100, 150, 200, and 400μg/mL of peptide solution, the rate of cell death after 12, 24, and 48h was assessed using MTT test. After confirmation of the 30µg/mL efficacy and nontoxic concentration, the cells were exposed to this concentration, and the total RNA was extracted. The quantitative real-time PCR (RT-qPCR) technique was performed for the amplification of Bax, caspase3, atg5, and GAPDH (glyceraldehyde 3-phosphate dehydrogenase as the internal control) genes. The cytotoxicity of peptide against normal cells exhibited that the IC50 at 24 and 4h included 80 and 100µg/mL, respectively. After 24-72h of treatment, a significant difference in the mean percentage of CRC living cells was observed at concentrations of 50-400μg/mL of conjugated peptide (p < 0.05). The IC50 of the peptide at 24, 48, and 72h of exposure was measured as 30, 20, and 10μg/mL, respectively. The peptide resulted in a significant increase of 2.35-fold in the mean expression of Bax gene in CRC cells (p < 0.001). It also caused a significant increase of 1.75 times (p = 0.0112) of caspase 3 gene and 1.2 times (p = 0.0217) of atg5 gene. There was no significant difference among cell lines regarding the expression of each gene. The conjugated peptide caused the death of CRC lines via induction of the apoptosis and necrosis mechanisms. More studies are needed in this regard.