Innate immune signaling and negative regulators in cancer

Innate immune pattern recognition receptors (PRRs), including Toll-like receptors (TLRs), NOD-like receptors (NLRs), RIG-I-like receptors, and AIM2-like receptors (ALRs), function as pathogen pattern recognition molecules that sensor and initiate innate and adaptive immune responses against microbes and cancer cells. Recognition of pathogen-derived ligands by PRRs expressed on many types of cells, including dendritic cells (DCs) and T cells, triggers the NF-kB, type 1 interferon and inflammasome activation pathways, leading to the production of proinflammatory cytokines that are essential in inflammation and inflammation-linked cancer. Both positive and negative regulators are critical in the maintenance of innate immune homeostasis. In this review, I focus on the current understanding of PRRs, signaling pathways and their regulation through negative regulators. Their relevance to cancer will be discussed as well.