The copper (II) complex of salicylate phenanthroline induces immunogenic cell death of colorectal cancer cells through inducing endoplasmic reticulum stress

In our previous study, Cu(sal)phen was found to have anti-tumor effects, yet its precise mechanism remains unknown. Research has shown that dying tumor cells release damage-associated molecular patterns (DAMPs) to promote anti-tumor immune response. Therefore, we have further explored the effects and potential molecular mechanisms of Cu(sal)phen-induced immunogenic cell death (ICD) in colorectal cancer (CRC). ELISA and flow cytometry were used to detect the effects of Cu(sal)phen treatment on ICD markers. The molecular mechanisms of Cu(sal)phen-induced ICD were investigated through the detection of endoplasmic reticulum stress (ERS) and reactive oxygen species (ROS) in vitro using Western blot and flow cytometry. Additionally, a mouse model was constructed to study the effects of Cu(sal)phen on immune cells and anti-tumor-related cytokines in vivo. Cu(sal)phen induced the release of calreticulin (CRT), adenosine triphosphate (ATP) and high mobility group box 1 (HMGB1), the main molecular markers of ICD, by promoting the accumulation of ROS and inducing ERS. Furthermore, Cu(sal)phen promoted the maturation of dendritic cells (DCs) and activation of CD8+T cells, as well as the secretion of interleukin-12 (IL-12) and interferon-γ (IFN-γ), while downregulating transforming growth factor-β (TGF-β) levels, thereby activating the anti-tumor immune response. Cu(sal)phen has the potential to induce ICD in tumors and activate the adaptive immune response to achieve anti-tumor effects. This makes Cu(sal)phen a promising candidate for the treatment of CRC.