Abstract A06: Elucidation of the extracellular adenosine pathway in metastatic pancreatic cancer

Abstract

Abstract Pancreatic cancer is a deadly disease that is expected to kill over 45,000 people in the United States this year alone. More than 80% of pancreatic cancer patients begin treatment after the disease has already metastasized. We recently published on an autochthonous mouse model of pancreatic cancer (Pdx1-cre; LSL-KRASG12D/+; LSL-Trp53R172H; Rosa26LSL-YFP herein KPCY), whereby we studied the molecular consequences of losing the tumor suppressor P120-CATENIN (encoded by the gene Ctnnd1). We demonstrated that pancreas-specific Ctnnd1 heterozygous deletion (herein P120-het) in KPCY mice dramatically increased metastatic potential relative to KPCY control animals. Upon further investigation with co-immunofluorescence, we found that the metastatic lesions were largely devoid of any P120 protein. The metastatic cells with complete P120 loss appear more mesenchymal, a phenotype associated with tumor cells undergoing epithelial-to-mesenchymal transition (EMT) and with increased metastatic potential. To determine the underlying processes downstream of P120 loss that may be driving EMT and metastasis, we performed RNA-sequencing on P120-WT (nonmetastatic) and P120-null (highly metastatic) tumor cells. Compared to the P120-WT tumor cells, the P120-null tumor cells revealed significant upregulation of several genes involved in extracellular adenosine signaling, Enpp3, Nt5e, and Adora2B. More recently, we confirmed upregulation of ENPP3, NT5E, and ADORA2B at the protein level, compared to healthy pancreas tissue, using immunohistochemistry (IHC). In the highly metastatic cells, Enpp3 (Ectonucleotide pyrophosphatase/phosphodiesterase-3) expression was increased 57-fold. ENPP3 is a type II glycoprotein involved in binding to and converting extracellular ATP into AMP. Nt5e/CD73 was increased 9-fold and also has ecto-nucleotidase activity to convert AMP to adenosine. Increases in extracellular adenosine can activate ADORA2B (a cell membrane receptor that binds adenosine and initiates downstream intracellular signaling), which was activated 4-fold. While this pathway has been shown to be important and therapeutically relevant in other cancers, it has yet to be fully characterized in the context of pancreatic cancer. In summary, using a model with increased metastatic capability, we have unraveled a novel panel of upregulated and functionally related genes that are related to increasing and sensing extracellular adenosine levels. Our recent data suggest that extracellular adenosine signaling may be a previously undiscovered mechanism for cells to acquire metastatic ability. Citation Format: Anna M. Chiarella, Rustgi K. Rustgi. Elucidation of the extracellular adenosine pathway in metastatic pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr A06.