Copper (II) complex of salicylate phenanthroline induces the apoptosis of colorectal cancer cells, including oxaliplatin‑resistant cells

Oxaliplatin (Oxa) is one of the most effective chemotherapeutic drugs used in the treatment of colorectal cancer (CRC). However, the use of this drug is associated with severe side-effects and patients eventually develop resistance to Oxa. In recent years, copper complexes have been extensively investigated as substitutes for platinum-based drugs. Therefore, a number of copper complexes have also been developed for cancer therapy, such as copper (II) complex of salicylate phenanthroline [Cu(sal)(phen)]. In the present study, the antitumor activity and the related molecular mechanisms of Cu(sal)(phen) were examined in CRC cells. As compared with the chemotherapeutic drug, Oxa, Cu(sal)(phen) was more effective in inducing apoptosis and reactive oxygen species (ROS) production, and in decreasing mitochondrial membrane potential in the CRC cell lines, HCT116 and SW480. In addition, the expression of the apoptosis-related proteins, Bcl-2 and survivin, and those of the upstream regulators, p-JAK2 and p-STAT5, were significantly decreased in the two cell lines following treatment with Cu(sal)(phen). Furthermore, the efficacy of the complex against CRC was found to be excellent in an animal model. The results of immunohistochemical analysis revealed that the expression levels of Bcl-2, survivin and Ki-67 in tumor tissues were decreased following Cu(sal)(phen) treatment. The antitumor mechanisms underlying Cu(Sal)(phen) treatment were the induction of ROS generation, the inhibition of the JAK2/STAT5 signaling pathway and the downregulation of the expression of anti-apoptotic proteins, such as Bcl-2 and survivin. On the whole, the findings of the present study indicated that Cu(sal)(phen) effectively inhibited the viability and proliferation of HCT116 and SW480 CRC cells; in the future, the authors aim to conduct further experiments in future studies to provide more evidence that supports the development of Cu(sal)(phen) as a therapeutic agent for CRC.