CopA3 peptide induces permanent cell-cycle arrest in colorectal cancer cells.

Cell-cycle arrest reflects an accumulation of responses to DNA damage that sequentially affects cell growth and division. Herein, we analyzed the effect of the 9-mer dimer defensin-like peptide, CopA3, against colorectal cancer cell growth and proliferation in a dose-dependent manner upon 96 h of treatment. As observed, CopA3 treatment significantly affected cancer cell growth, reduced colony formation ability, increased the number of SA-β-Gal positive cells, and remarkably reduced Ki67 protein expression. Notably, in HCT-116 cells, CopA3 (5 μM) treatment effectively increased oxidative stress and, as a result, amplified the endogenous ROS, mitochondrial ROS, and NO content in the cells, which further activated the DNA damage response and caused cell-cycle arrest at the G1 phase. The prolonged cell-cycle arrest elevated the release of inflammatory cytokines in the cell supernatant. Nevertheless, mechanistically, NAC treatment effectively reversed the CopA3 effect and significantly reduced the oxidative stress; subsequently rescuing the cells from G1 phase arrest. Overall, CopA3 treatment can inhibit the growth and proliferation of colorectal cancer cells by inducing cell-cycle arrest through the ROS-mediated pathway.