Resistin: An Irresistible Therapeutic Target for Inflammatory Diseases, Allergy-Related Disorders, and Cancer

Resistin is a cytokine that has gained popularity over the last decade for its roles in allergic and inflammatory reactions. It is a cysteine-rich protein secreted mostly by macrophages in humans and adipocytes in mice. It was first identified as a small molecule that mediates insulin resistance in rodents. Following the discovery of resistin, many researchers have started investigating its activity in a wide range of pathological conditions where inflammation is present. Findings from these studies have revealed that resistin serves a major function in almost all inflammatory diseases. Elevated serum resistin levels have been associated with allergic contact dermatitis, atherosclerosis, osteoarthritis, obesity, neurological and cognitive disorders, and cancer. Therefore, it is critically important to understand the exact role of resistin in these pathological conditions to develop an effective therapeutic approach. So far, four receptors are known to interact with resistin. Two of these receptors, toll-like receptor 4 (TLR4) and adenylyl cyclase-associated protein 1 (CAP1), are present on the membrane of human macrophages. The other two receptors, receptor tyrosine kinaselike orphan receptor 1 (ROR1) and decorin (DCN), are found in mice. Even though it is possible that ROR1 exists in humans, too, there is still an open question regarding other receptors that interact with resistin in humans. However, accumulated data suggest that resistin is involved in multiple signaling pathways via binding to TLR4 and CAP1. This chapter aims to elaborate on the multi-faceted roles of resistin in cellular events as well as its contribution to allergic and inflammatory diseases with a focus on cancer formation based on the current and most recent findings.