Abstract 2038: NG1/NGL1 engagement supports PDAC development via CAF to PDAC nutrition and CAF-regulated immunosuppression

Pancreatic ductal adenocarcinoma (PDAC) is predicted to soon become the second killer cancer in the USA. One of the hallmarks of PDAC is desmoplasia, which consists of an expansion in activated stellate cells, known as cancer associated fibroblasts (CAFs), and remodeling of their extracellular matrix. Desmoplasia is a major culprit for the unique PDAC microenvironment, which both collapses blood vessels restricting nutrients and fosters immunosuppression. Crosstalk between CAFs, PDAC, and immune cells, within this microenvironment, is not fully understood. To study the functions of CAFs on PDAC development, we first performed a microarray comparing patient matched normal pancreatic stellate cells and CAFs cultured using our stromal 3D system. We identified proteins upregulated in CAFs that have not been previously implicated in desmoplasia. To understand the functional role of these proteins, CRISPR/Cas9 mediated deletion of target proteins was undertaken and cells were subjected to a number of co-culture assays, with PDAC cells and NK cells. Assays consisted of material transfer, cell engagement, proliferation, survival, NK cell activation and PDAC killing. Syngeneic/orthotopic in vivo models, RNAseq analyzes and quantitative multi-plex microscopy, on pathological samples, were also used. We uncovered the ectopic expressions of NetrinG1 (NG1), a neural pre-synaptic protein, in CAFs, and of NG1’s post-synaptic binding partner, NGL1, in PDAC cells. Using our 3D system, we observed that heterotypic CAF-to-PDAC interactions, via NG1/NGL1 engagement, are critical for providing survival advantages to nutrient deprived PDAC cells and for CAFs to protect PDAC from NK cell-driven elimination. Mechanistically, we uncovered that PDAC starvation is overcome by NG1 expressing CAFs that provide nutrition via material transfer. Further, knockout of NG1, in CAFs, significantly reduced the production of immunosuppressive cytokines, such as IL-6, IL-8, and TGF-β. Moreover, loss of NG1 from CAFs resulted in anti-tumor NK cell activation. Unexpectedly, we observed a link between glutamate metabolism in CAFs and the inactivation of anti-tumor NK cells, and this was dependent on CAFs’ NG1 expression. These results were confirmed in an orthotopic PDAC mouse model in which ablation of NGL1, in syngeneic mouse PDAC cells, significantly halted tumor growth. RNAseq comparing CON or NG1+ CAFs vs. knockout NG1- CAFs rendered changes in neural, metabolic and fibrous signature pathways. Translationally, we saw clear expression of stromal NG1 only in PDAC affected pancreata. Overall, this study identifies two novel targets for PDAC; a cancer that lacks effective therapies. Inhibition of the NG1/NGL1 axis, constitutes a potential future therapeutic approach, as it alters CAF mediated metabolism and reverts immunosuppression, stunting PDAC growth in vitro and in vivo. Citation Format: Ralph Francescone, Débora Barbosa Vendramini-Costa, Janusz Franco-Barraza, Jessica Wagner, Alex Muir, Linara Gabitova, Tatiana Pazina, Tiffany Luong, Neelima Shah, Dustin Rollins, Ruchi Malik, Sapna Gupta, Roshan Thapa, Diana Restifo, Allison Lau, Yan Zhou, Kathy Q. Cai, Harvey Harvey Hensley, Emmanuelle Nicolas, Warren D. Kruger, Karthik Devarajan, Siddharth Balachandran, Wafik S. El-Deiry, Matthew Vander Heiden, Kerry Campbell, Igor Astsaturov, Edna Cukierman. NG1/NGL1 engagement supports PDAC development via CAF to PDAC nutrition and CAF-regulated immunosuppression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2038.