RESUMEN
G protein-coupled receptors (GPCRs) are the most widely targeted class for approved drugs but only a small portion (-15%) of GPCRs are currently targeted. Work in my laboratory has tested the hypothesis that individual cell types express previously unrecognized GPCRs that regulate cell function and may be novel drug targets. A key focus has been our efforts to define differential expression (DE) of GPCRs on normal cells versus cells from patients with diseases: pulmonary arterial smooth muscle cells/pulmonary arterial hypertension, lung and cardiac fibroblasts/lung and cardiac fibrosis and pancre?atic cells/pancreatic ductal adenocarcinoma (PDAC). To test our hypothesis, we have used unbiased (GPCRomic) approaches (Taqman GPCR arrays and RNA-seq), mining of publicly available datasets (the GTEX database for normal tissues and the Cancer Genome Atlas, TCGA) and studies of signaling and functional activity to validate newly detected GPCRs. The GPCRomic studies reveal that most cell types and tissues express >100 different GPCRs with limited prior data for many highly expressed GPCRs, numerous of which are ″orphans″ (which lack known physiologic agonists). Numerous GPCRs have DE and alter functionin diseased cells. For example, studies of PDAC tumors/cells and pancreatic cancer- associated fibroblasts (PCAFs) identify two GPCRs with high DE, respectively, in PDAC cells compared to normal pancreatic ductal epithelial cells and in PCAFs compared to normal pancreatic Fs/stellate cells. These two GPCRs: ① are frequently, highly expressed in PDAC tumors compared to normal pancreas and ② regulate functional activities that influence the malignant pheno?type. Overall, the results indicate the utility of unbiased GPCRomic and data- mining approaches to identify previously unrecognized, functional GPCRs that may contribute to human disease and that may be novel, drug gable targets.
RESUMEN
OBJECTIVE Pancreatic ductal adenocarcinoma (PDAC), a lethal cancer in need of new, effective therapies, has a unique tumor microenvironment characterized by a dense fibrotic stroma (desmoplasia) that is generated by pancreatic cancer- associated fibroblasts (PCAFs) derived from pancreatic stellate cells (PSCs) and pancreatic fibroblasts (PFs). METHEDS and RESULTS Hypothe?sizing that G protein-coupled receptors (GPCRs) may regulate PCAFs, we used an unbiased GPCRomic array approach to compare GPCR expression in PCAFs, PFs and PSCs and identified 82 GPCRs commonly expressed by PCAFs derived from primary tumors of five PDAC patients. We discovered that PCAFs have increased expression of numerous GPCRs, in particular aGPCR with much higher expression in PCAFs compared to both PFs and PSCs. Immunohistochemistry revealed increased expression of this GPCR in PDAC tumors. Co- culture of PSCs with PDAC cells or incubation with TNFα induced its expression. Activation of the GPCR in PCAF sincreased expression of interleukin-6 (IL-6) via a cAMP/PKA/CREB signaling pathway. GPCR knockdown with siRNA diminished IL-6 production and secretionby PCAFs and ability of PCAF conditioned media to enhance proliferation of PDAC cells. CONCLUSION We conclude that PDAC cells induce expression by PCAFs of a novel GPCR, resulting in increased IL-6 production by PCAFs and promotion of PDAC cell proliferation. This PCAF-expressed GPCR thus contributes to PDAC cell-PCAF interaction and as such, may be a novel therapeutic target for PDAC tumors.