Role of innate immunity in cancers and antitumor response

Abstract

Innate immune system serves as the first line of defense against pathogens and cancers. In tumors, innate immune cells are attracted into the tumor site, where they can recognize the transformed cells. Recognition of tumor cells is mediated by receptors expressed on the surface of innate immune cells, such as NK receptors, CLRs, as well as phagocytosis receptors expressed on APCs. Additionally, factors released from stressed cells at the tumor microenvironment, such as PAMPs and DAMPs, are recognized by another set of receptors, including TLRs, RLRs, and NLRs, which trigger distinct innate signaling pathways; these pathways lead to maturation, activation, as well as production of cytokines and chemokines from immune cells, to attract more immune cells into the tumor site and initiate an immune response against tumor cells. Innate immune cells may also be involved in the promotion of tumor growth, angiogenesis, and metastasis, due to the interaction between tumor cells and innate immune cells at the tumor microenvironment. Thus, a deep knowledge of the role of innate immune system in tumor immunity and tumorigenesis is critical to develop new strategies for the immunotherapy of cancer.