SOD1 and neoplasm: In the tumor microenvironment, CQ functions both as a copper ion chelator to deplete intracellular copper ions and to inhibit the activity of copper - dependent enzymes such as SOD1, leading to ROS accumulation and mitochondrial dysfunction, and as a direct inhibitor of 26S proteasome activity, impeding the degradation of ubiquitinated proteins and resulting in the abnormal accumulation of misfolded proteins within cells (Sun H. et al., 2025).