1. Introduction

To attain malignant phenotype, the tumor cells overcome the deadly encounter of immune system through a process known as immune editing and thus create an immunosuppressive environment [1]. This phenomenon is evident in clinical scenarios where patients with

© The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

malignant tumor quite often possess a blunt immune system [2]. Thus the immune system has an impact in the progression and severity of the disease. For most of advanced malignancies where chemotherapy is considered the treatment modality of choice often rely on the strategy to target and destroy rapidly dividing cancer cells, neglecting the possibility that immune system may contribute to the efficacy of treatment. In recent years, extensive research in the context of cancer immune system has led to the development of cancer immunotherapy field that may prove to be a powerful weapon in the treatment of cancer through modulating the immune system. The suppressive roles played by immune cells of tumor microenvironment in promoting tumor progression indicate that these cells can serve as novel therapeutic targets in the treatment of cancer [3]. Emerging evidence in recent time indicates that metal chelates of Schiff base can be used as a potent anticancer agent that imparts their cytotoxic effect through generation of reactive oxygen species (ROS) in cancer cells [4]. Recent study also highlights the role of those metal chelates as immune-stimulating agents [4] that possess the ability to inhibit or subvert immunosuppressive phenotype toward proimmunogenic type and thus associated with tumor regression. In search of novel immune-stimulatory or modulatory agents, we had synthesized a number of metal chelates of a Schiff base namely N-(2-hydroxy acetophenone) glycinate (NG). Among these, copper and manganese complexes of NG, e.g., copper N-(2 hydroxy acetophenone) glycinate (CuNG) and manganese N-(2-hydroxy acetophenone) glycinate (MnNG) exhibit immunomodulatory properties [4]. Other such metal chelates of iron, nickel, and zinc formed with the same organic moiety (NG) lack the property of immunomodulation [4]. This chapter deals with the major negative regulator of immune system during cancer, as well as the key aspects of how the immune system can be controlled or manipulated by the application of novel Schiff base metal chelates to enhance anticancer immunity.
