Purified recombinant human Chromogranin A N46 peptide with remarkable anticancer effect on human colon cancer cells

Human Chromogranin A N46 (CGA-N46) is a weak cationic α-helical peptide with wide-spectrum antibacterial, fungal, and anticancer activities. In this study, the recombinant human CGA-N46 peptide was expressed successfully in Escherichia coli. The gene of CGA-N46 was cloned into the expression vector pET-15b without a fusion tag at the N terminus and the peptide was expressed using Isopropyl-β-d-thiogalactoside (IPTG) as an inducer. Using 8 M guanidinium HCl, inclusion bodies containing the peptide were purified and solubilized. The rhCGA-N46 peptide was purified using Q-FF anion exchange column. The cytotoxicity of the purified rhCGA-N46 peptide was investigated on WI-38 human lung normal cell line. The anticancer activity was studied on human colon cancer cell line; HCT-116 cell line. Besides, the possible involvement of rhCGA-N46 peptide in regulating apoptotic signal pathways was analyzed by detecting the expression levels of BCL2, BID, and CAS-8 in the treated cells. The results concluded that the active peptide recovery was up to 41.98%. The purified rhCGA-N46 was safe on normal cells with IC₅₀ = 227.74 µg/ml (40.67 µM) and had an obvious anticancer effect on colon cancer cells with IC₅₀ = 1.997 µg/ml (356.6 nM). The expression level of BCL2 was down-regulated and BID and CAS-8 were up-regulated significantly in treated HCT-116 cells compared to untreated. In conclusion, the rhCGA-N46 peptide was produced successfully in the native form with promising anti-colon cancer activity.