Studies on the tumor microenvironment reveal that infiltration or induction of tumor-associated immune regulatory populations at the local tumor site is strongly associated with severe immunosuppression as well as worse prognosis of patients. Despite major advances in cancer immunotherapy, most of the therapeutic agents often fail to break negative immunosuppressive network to trigger anticancer immunity, leading to tumor progression and metastasis. Therefore, emergence of potent immunostimulatory agents is of great clinical importance. Emerging evidence suggests that metal chelates of Schiff bases hold the promise to overcome tumor-associated immunosuppression by inhibiting or subverting suppressive immune population toward pro-immunogenic type and thus can be used clinically for immunotherapy of different types of cancers
