Dual Anti-tumorigenic Activities of Human Glycyl-tRNA Synthetase and Its Peptide Derivatives

Abstract

ABSTRACT

Over the past decade, the ex-translation functions of secreted Aminoacyl-tRNA Synthetases (AARSs) have been more elucidated. Several of the secreted AARSs have been shown to be correlated to the immune system. Secreted Tryosyl-tRNA Synthetase (YRS) and Histidyl-tRNA Synthetase (HRS)/Asparaginyl-tRNA Synthetase (NRS) induce polymorphonuclear leukocyte (PMN) and immature dendritic cell migration, respectively. In relation to macrophage, Tryptophanyl-tRNA Synthetase (WRS) plays a role in activating macrophage upon bacterial infection while Lysyl-tRNA Synthetase (KRS) and Glycyl-tRNA Synthetase (GRS) were both shown to have an influence on macrophages in a tumor microenvironment. KRS secretion from tumor cells causes a proinflammatory response and migration of macrophage. GRS secretion from macrophage responds to Fas ligand secreted from tumor cells and binds to Cadherin-6 (CDH6) suppressing tumor growth. Previous observations showed that GRS antibodies were detected in patients blood with inflammatory induced myositis and interstitial lung disease. In addition, GRS was shown to bind to macrophage, which mediates inflammatory responses. These observations lead me to further understand the role of GRS on macrophage. In this study, I focused on explicating GRS role on macrophage and development of its derived peptides . In chapter one of this study, it was shown that macrophage, under stressed conditions, secret GRS in autocrine manner stimulating their polarization to become anti-tumor. GRS binds to macrophage receptor CELSR2, part of the super cadherin and G protein-coupled receptor (GPCR) families, activating the RAS-RAF-MEK signaling pathway. Upon activation, TNF-α, IL-6, and CXCL10 cytokines are secreted shifting macrophages from M0 state to M1 type, which is antitumor, and induces phagocytosis. GRS treatment in an initiation mice model, the growth of tumor was prevented or retarded. This data shows that GRS is an important secreted cytokine that is needed for immune surveillance. In chapter two of this study, the active domain of GRS that binds to cancer cells was discovered and developed into a druggable peptide. GRS has been previously reported to kill cancers that expressed cadherin-6 (CDH6) by suppressing ERK signaling and inducing apoptosis. Through computational predicted binding regions of GRS to CDH6, mutations were performed to find the active region of GRS. Upon these results, synthesized peptides were derived and tested in-vitro and in-vivo. The active region of the peptide was reduced to a conformational stable 8 and cyclic 25 amino acid, which greatly reduced the tumor growth by intra-tumor (IT) and intravenous (IV) injection. In-vivo imaging system (IVIS) showed the fluorescent labeled peptides targeting the tumor. These results show a developed GRS-derived peptide role as a potential drug candidate. This study shows secreted GRS has an important role in immunosurveillance. GRS is secreted by macrophages as an alarmin that notices the abnormal environment formed during tumorigenesis. Secreted GRS polarizes macrophage to produce antitumor cytokines to eliminate the malignant tumor cells and protect the body. In addition, an active and stable peptide derived from GRS was developed. The in-vitro and in-vivo testing showed promising results that GRS-derived peptide as a therapeutic agent against cancer.