Abstract C007: Targeting vasoactive intestinal peptide receptor signaling enhances T-cell mediated anti-tumor response to immune checkpoint therapy in pancreatic ductal adenocarcinoma

Abstract Current immune checkpoint therapies including anti-CTLA-4 and anti-PD1 have limited efficacy in the treatment of pancreatic ductal adenocarcinoma (PDAC), largely due to a paucity of effector T cells within the tumor microenvironment (TME). In our study, we show that vasoactive intestinal peptide (VIP), an immunosuppressive neuropeptide, is over-expressed in human PDAC tumors. Thus, we hypothesized that paracrine production of VIP by tumor cells within the PDAC TME constitutes an immune checkpoint pathway that limits the antitumor activity of VIP-receptor (VIP-R) expressing T cells. We first evaluated whether inhibiting VIP-R signaling by peptide-based VIP-R antagonist affects the growth of PDAC cells in vitro. Treatment of PDAC cells with increasing concentrations of VIP-R antagonist did not affect the viability of PDAC cell lines in vitro, except for a transient effect in MT5 albeit not significant. Furthermore, depletion of VIP receptor 2 (VPAC2) in a PDAC cell line, Panc02, by CRISPR-Cas9 KO had similar growth rates in vitro with a slight growth delay in vivo compared to the parental cell line. These data suggest that the expression of VPAC2 on PDAC cells may not confer a significant autocrine effect on tumor growth impacted by VIP signaling. On the contrary, human T cells cultured with VIP-R antagonists had enhanced activation, decreased proportions of Tregs, and exhausted T cells co-expressing PD-1, Tim-3, and Lag-3. Next, we performed pharmacological inhibition with VIP-R antagonists in tumor-bearing mice to model T cell homing, activation, and antitumor responses in preclinical murine models of PDAC. Daily subcutaneous injections of VIP-R antagonists had synergistic antitumor activity when combined with anti-PD-1 therapy with decreased tumor burden and improved survival. In contrast to the limited single-agent activity of anti-PD1 or VIP-R antagonists, combination therapy eliminated tumors in up to 40% of animals. Anti-tumor responses were T cell-dependent, as the combination therapy failed to improve survival in CD4 or CD8 deficient mice using knock-out strains and antibody depletion. In addition, tumor-free mice were resistant to tumor re-challenge, indicating the generation of anti-cancer immunological memory. In correspondent to these data, combination therapy led to enhanced T cell activation in vivo with increased antigen-specific T cells, decreased frequencies of Tregs as well as enhanced T cell infiltration to the tumor site as observed by infiltration of adoptively transferred GFP+ T cells into PDAC tumors. Taken together, our findings show that VIP-VIPR signaling is a targetable mechanism of immune escape in PDAC. Inhibiting VIP-R signaling improves T cell effector properties and enhances the responsiveness of PDAC to immune checkpoint therapy. Further pharmacokinetic and toxicology studies are underway. Citation Format: Tenzin Passang, Sruthi Ravindranathan, Jian-Ming Li, Shuhua Wang, Michael Brandon Ware, Hanwen Zhang, Gregory B. Lesinski, Edmund K. Waller. Targeting vasoactive intestinal peptide receptor signaling enhances T-cell mediated anti-tumor response to immune checkpoint therapy in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr C007.