The role of 2-arachidonoylglycerol in the regulation of the tumor-immune microenvironment in murine models of pancreatic cancer

Abstract

The pancreatic ductal adenocarcinoma (PDAC) microenvironment plays a critical role in the antitumor immune response. 2-arachidonoylglycerol (2-AG) exhibits a direct antitumor effect in various tumor models. However, the immunomodulatory effect of 2-AG on PDAC remains obscure. The aim of this study was to explore the tumor microenvironment response to 2-AG in pancreatic cancer. A PDAC orthotopic tumor model was used to investigate tumor proliferation and the population of immune cells in vivo, including dendritic cells (DCs), myeloid-derived suppressor cells (MDSCs), CD8+ T cells and CD4+ T cells. The effect of 2-AG on panc02 cell proliferation and DC2.4 cell maturation in vitro by mediating activation the typical cannabinoid receptors (CB1, CB2) was evaluated by flow cytometry and CCK8. The protein levels of P-STAT6, STAT6 and GADPH were measured by Western blotting.2-AG inhibited pancreatic cancer cell proliferation in tumor bearing mice and panc02 cell. Inhibition of proliferation was blocked by the CB1receptor antagonist (AM251) but not the CB2 receptor antagonist (AM630). In addition, 2-AG promoted DC phenotypic maturation and the production of proinflammatory cytokines by up-regulating p-STAT6. These effects were also blocked by AM251 but not AM630. Moreover, we also provide evidence that 2-AG administration induced the expansion of MDSCs in tumor bearing mice. However, no effect on the population of CD8+ T cells and CD4+ T cells was observed. Our findings support 2-AG exhibited direct antitumor effects via inhibiting pancreatic cancer proliferation and inducing DC phenotypic maturation, but also significantly promoted an immunosuppressive microenvironment via increasing the suppressive immune cell population of MDSCs.