Abstract 1139: G protein-coupled receptors (GPCRs): unrecognized potential therapeutic targets in cancer

G protein-coupled receptors (GPCRs) are the largest class of signaling receptors in humans and other species and in addition, the most widely targeted class for FDA-approved therapeutics. However, GPCRs are not commonly targeted in cancers other than endocrine tumors. We hypothesize that GPCRs may have been “missed” as targets in cancer, perhaps in part because they have not been frequently identified as driver mutations; however, GPCRs may have unappreciated utility as therapeutic targets in a variety of tumors. To test this hypothesis, we have used unbiased approaches (Taqman GPCR arrays and RNA-seq), mining of publicly available datasets (e.g., The Cancer Genome Atlas, TCGA), and validation studies (e.g., protein and functional analyses) to assess GPCRs in a variety of human tumors, cancer cells and stromal cells (cancer-associated fibroblasts, CAFs). A major focus of our efforts has been on pancreatic ductal adenocarcinoma (PDAC) cells/tumors and pancreatic CAFs (PCAFs). We find that PDAC cells and PCAFs express >70 different GPCRs, including many orphan GPCRs (receptors without known physiologic agonists) and that numerous GPCRs are expressed at much higher levels than in normal precursor cells (pancreatic ductal epithelial cells for PDAC cells and pancreatic stellate cells and pancreatic fibroblasts for PCAFs). We find that a cluster of GPCRs is overexpressed in PDAC tumors. Two such receptors are orphan GPCRs, Orphan 1 and Orphan A, neither of which is mutated but each has high expression, respectively, in PCAFs and PDAC cells. Orphan 1 and Orphan A have at least 2-fold higher expression in >90% of PDAC tumors in TCGA compared to that in normal pancreatic tissue (compiled from the GTEX database). Higher expression of orphan A is associated with decreased survival and remission, while Orphan 1 expression correlates with that of numerous fibrotic genes. Importantly, both Orphan 1 and Orphan A are functional and appear to contribute to the malignant phenotype. For example, siRNA knockdown of Orphan 1 in PCAFs blunts production of profibrotic markers and decreases ability of conditioned media from PCAFs to enhance proliferation of PDAC cells while transfection of Orphan A increases DNA synthesis of normal pancreatic ductal epithelial cells. Taken together, these and other results suggest that in addition to their role in endocrine tumors, GPCRs represent previously unrecognized contributors to cancer through actions on tumor cells and stromal cells. These data suggest the possibility that highly expressed GPCRs (such as Orphan A) may function as oncogenes. Thus, GPCRs may be druggable, novel targets for the treatment of cancer, including pancreatic cancer, a tumor for which new therapeutics are an important, unmet need. Note: This abstract was not presented at the meeting. Citation Format: Paul A. Insel, Krishna Sriram, Shu Z. Wiley, Thalia McCann, Randall P. French, Andrew M. Lowy. G protein-coupled receptors (GPCRs): unrecognized potential therapeutic targets in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1139. doi:10.1158/1538-7445.AM2017-1139