Abstract 116: Stromal expression of the synaptic protein netrin G1 ligand (NGL-1) promotes tumorigenesis and immunosuppression in pancreatic cancer
Authors: Vendramini-Costa Debora B. , Francescone Ralph , Luong Tiffany , Franco-Barraza Janusz , Astsaturov Igor , Cai Kathy Q. , Klein-Szanto Andres J. , Wang Huamin , Campbell Kerry S. , Cukierman Edna 
Published: July 2021

Abstract
Pancreatic ductal adenocarcinoma (PDAC) is one of the most deadly types of cancer, with a 5-year survival of only 10%. One of the major features of PDAC is the dense fibrous stroma, due to the expansion of cancer associated fibroblasts (CAFs) and their extracellular matrix (ECM). This unique environment promotes immunosuppression, lack of nutrients and exclusion or inactivation of antitumor immune cells, representing a challenge for therapies. Recently, we identified the ectopic expression of the neuronal protein Netrin G1 Ligand (NGL-1) in PDAC tissue, including its novel expression in immune cells and CAFs. However, the roles of NGL-1 in the microenvironment of PDAC and in immune cell function are unknown and deserved further investigation. The effects in tumorigenesis were evaluated by orthotopically injecting pancreatic tumor cells in wild-type and NGL-1 full body knockout mice. The roles of NGL-1 in the pro-tumor functions of CAFs were evaluated using our in vitro 3D system, and questioning if NGL-1+ CAFs, compared to NGL-1 knockdown CAFs (CRISPRi), are able to rescue PDAC cell survival under nutrient deprivation, and discern their immunosuppressive profile. For the translational approach, we assessed the overall survival of 140 PDAC patients according to NGL-1 expression in the TME. Myeloid, T and NK cells from tumor-bearing mice tended to overexpress NGL-1 when compared with cells from naïve mice. Moreover, CD8+ and CD4+ T cells from NGL-1 KO mice proliferated more when stimulated in vitro, suggesting that NGL-1 could represent a functional brake for T cells. Moreover, the lack of NGL-1 in stimulated bone marrow-derived macrophages decreased pro-inflammatory cytokine secretion, further suggesting a functional role for NGL-1 in myeloid cells. Of note, NGL-1 KO mice orthotopically injected with PDAC cells developed smaller tumors with decreased secretion of immunosuppressive factors. In accordance, NGL-1 knockdown CAFs did not support PDAC cell survival in vitro and produced less immunosuppressive cytokines, which was phenocopied by the treatment with a peptide targeting NGL-1. Finally, the low expression of NGL-1 in CAFs and immune cells correlated with better survival of PDAC patients, therefore underscoring NGL-1 as a potential new target in PDAC, that could be manipulated in different compartments in pancreatic cancer (cancer cells, CAFs, immune cells).
Citation Format: Debora B. Vendramini-Costa, Ralph Francescone, Tiffany Luong, Janusz Franco-Barraza, Igor Astsaturov, Kathy Q. Cai, Andres J. Klein-Szanto, Huamin Wang, Kerry S. Campbell, Edna Cukierman. Stromal expression of the synaptic protein netrin G1 ligand (NGL-1) promotes tumorigenesis and immunosuppression in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 116.