Identification of active small-molecule modulators targeting the novel immune checkpoint VISTA.

BACKGROUND: Cancer immunotherapy has gained increasing popularity as a novel approach to treat cancer. A member of the B7 family, V-domain immunoglobulin suppressor of T-cell activation (VISTA) is a novel immune checkpoint that regulates a broad spectrum of immune responses. VISTA is an acidic pH-selective ligand for P-selectin glycoprotein ligand-1(PSGL-1). CA-170, a first-in-class small-molecule dual antagonist of VISTA/PD-L1, was collaboratively developed by Aurigene Discovery Technologies Limited and Curis, Inc. It is currently in Phase I clinical trial. RESULTS: In this study, we develop homology modeling for the VISTA 3D structure and subsequent virtual screening for VISTA small-molecule hit ligands. Visualization of the binding postures of docked ligands with the VISTA protein indicates that some small molecular compounds target VISTA. The ability of antagonist to disrupt immune checkpoint VISTA pathways was investigated though functional studies in vitro. CONCLUSIONS: Affinity active molecule for VISTA was obtained through virtual screening, and the antagonist compound activity to VISTA was assayed in cellular level. We reported a small molecule with high VISTA affinity as antagonist, providing ideas for development VISTA-targeted small molecule compound in cancer immunotherapy.

3-Acetyl-oleanolic acid ameliorates non-alcoholic fatty liver disease in high fat diet-treated rats by activating AMPK-related pathways.

3-Acetyl-oleanolic acid (3Ac-OA) is a derivative of oleanolic acid (OA), which has shown therapeutic beneficial effects on diabetes and metabolic syndrome. In this study we investigated whether 3Ac-OA exerted beneficial effect on non-alcoholic fatty liver disease (NAFLD) in rats and its potential underlying mechanisms. Treatment with 3Ac-OA (1-100 µmol/L) dose-dependently decreased the intracellular levels of total cholesterol (TC) and triglyceride (TG) in FFA-treated primary rat hepatocytes and human HepG2 cell lines in vitro. Furthermore, oil red staining studies showed that 3Ac-OA caused dose-dependent decrease in the number of lipid droplets in FFA-treated primary rat hepatocytes. SD rats were fed a high fat diet (HFD) for 6 weeks and subsequently treated with 3Ac-OA (60, 30, 15 mg·kg-1·d-1) for 4 weeks. 3Ac-OA administration significantly decreased the body weight, liver weight and serum TC, TG, LDL-C levels in HFD rats. Furthermore, 3AcOA administration ameliorated lipid accumulation and cell apoptosis in the liver of HFD rats. Using adipokine array analyses, we found that the levels of 11 adipokines (HGF, ICAM, IGF-1, IGFBP-3, IGFBP-5, IGFBP-6, lipocalin-2, MCP-1, M-CSF, Pref-1 and RAGE) were increased by more than twofold in the serum of 3Ac-OA-treated rats, whereas ICAM, IGF-1 and lipocalin-2 had levels increased by more than 20-fold. Moreover, 3Ac-OA administration significantly increased the expression of glucose transporter type 2 (GLUT-2) and low-density lipoprotein receptor (LDLR), as well as the phosphorylation of AMP-activated protein kinase (AMPK), protein kinase B (AKT) and glycogen synthase kinase 3ß (GSK-3ß) in the liver tissues of HFD rats. In conclusion, this study demonstrates that 3Ac-OA exerts a protective effect against hyperlipidemia in NAFLD rats through AMPK-related pathways.