G protein-coupled receptors (GPCRs) are the most widely targeted gene family for Food and Drug Administration (FDA)-approved drugs. To assess possible roles for GPCRs in cancer, we analyzed The Cancer Genome Atlas (TCGA) data for mRNA expression, mutations, and copy number variation (CNV) in 20 categories and 45 subtypes of solid tumors and quantified differential expression (DE) of GPCRs by comparing tumors against normal tissue from the Gene Tissue Expression Project (GTEx) database. GPCRs are overrepresented among coding genes with elevated expression in solid tumors. This analysis reveals that most tumor types differentially express >50 GPCRs, including many targets for approved drugs, hitherto largely unrecognized as targets of interest in cancer. GPCR mRNA signatures characterize specific tumor types and correlate with expression of cancer-related pathways. Tumor GPCR mRNA signatures have prognostic relevance for survival and correlate with expression of numerous cancer-related genes and pathways. GPCR expression in tumors is largely independent of staging, grading, metastasis, and/or driver mutations. GPCRs expressed in cancer cell lines largely parallel GPCR expression in tumors. Certain GPCRs are frequently mutated and appear to be hotspots, serving as bellwethers of accumulated genomic damage. CNV of GPCRs is common but does not generally correlate with mRNA expression. Our results suggest a previously underappreciated role for GPCRs in cancer, perhaps as functional oncogenes, biomarkers, surface antigens, and pharmacological targets.

G protein-coupled receptors (GPCRs) are the largest family of membrane receptors and targets for approved drugs. The analysis of GPCR expression is, thus, important for drug discovery and typically involves messenger RNA (mRNA)-based methods. We compared transcriptomic complementary DNA (cDNA) (Affymetrix) microarrays, RNA sequencing (RNA-seq), and quantitative polymerase chain reaction (qPCR)-based TaqMan arrays for their ability to detect and quantify expression of endoGPCRs (nonchemosensory GPCRs with endogenous agonists). In human pancreatic cancer-associated fibroblasts, RNA-seq and TaqMan arrays yielded closely correlated values for GPCR number (∼100) and expression levels, as validated by independent qPCR. By contrast, the microarrays failed to identify ∼30 such GPCRs and generated data poorly correlated with results from those methods. RNA-seq and TaqMan arrays also yielded comparable results for GPCRs in human cardiac fibroblasts, pancreatic stellate cells, cancer cell lines, and pulmonary arterial smooth muscle cells. The magnitude of mRNA expression for several Gq/11-coupled GPCRs predicted cytosolic calcium increase and cell migration by cognate agonists. RNA-seq also revealed splice variants for endoGPCRs. Thus, RNA-seq and qPCR-based arrays are much better suited than transcriptomic cDNA microarrays for assessing GPCR expression and can yield results predictive of functional responses, findings that have implications for GPCR biology and drug discovery.

G protein-coupled receptors (GPCRs) are the largest family of membrane receptors and targets for approved drugs.Analysis of GPCR expression is thus important for drug discovery and typically involves mRNA-based methods.We compared transcriptomic cDNA [Affymetrix] microarrays, RNA-seq and qPCR-based TaqMan arrays for their ability to detect and quantify expression of endoGPCRs (non-chemosensory GPCRs with endogenous agonists).In human pancreatic cancer-associated fibroblasts, RNA-seq and TaqMan arrays yielded closely correlated values for GPCR number (~100) and expression levels, as validated by independent qPCR. By contrast, the microarrays failed to identify ~30 such GPCRs and generated data poorly correlated with results from those methods. RNA-seq and TaqMan arrays also yielded comparable results for GPCRs in human cardiac fibroblasts, pancreatic stellate cells, cancer cell lines and pulmonary arterial smooth muscle cells. The magnitude of mRNA expression for several Gq/11-coupled GPCRs predicted cytosolic calcium increase and cell migration by cognate agonists. RNA-seq also revealed splice variants for endoGPCRs. Thus, RNA-seq and qPCR-based arrays are better suited than microarrays for assessing GPCR expression and can yield results predictive of functional responses--findings that have implications for GPCR biology and drug discovery. Abstract Graphic:GPCRs, a family of >800 membrane proteins in humans, respond to a wide range of peptides, proteins, lipids, metabolites etc. and regulate a broad range of cellular processes including proliferation, metabolism, and protein synthesis. There are ~360 GPCRs that are activated by endogenous agonists, i.e., endo-GPCRs other than visual, taste and olfactory receptors. EndoGPCRs are targets for a large fraction (~35%) of approved drugs. 1 The detection of GPCRs in cells and tissues is thus valuable for identifying GPCRs and defining their roles in cell physiology and pathophysiology as well as for identifying opportunities for drug discovery.Detection of GPCRs by protein-based methods is challenging. Due to their low expression, GPCRs are difficult to assay by current proteomic methods plus the paucity of well-validated antibodies for many GPCRs makes it problematic to detect them by immunological techniques. As a consequence, detection of GPCRs, especially in efforts to profile their expression in cells and tissues, relies on assays of mRNA expression. Multiple methods can assess mRNA expression but their utility for defining GPCR expression has not been assessed. We thus sought to evaluate GPCR expression by parallel analysis of RNA samples from a single cell type--human pancreatic cancer associated fibroblasts (CAFs) tested with three different techniques: TaqMan arrays, RNA sequencing (RNA-seq) and transcriptomic cDNA (e.g., Affymetrix) arrays. Due to the low expression of most GPCRs, even at the mRNA level, such a comparison is important for evaluating data in public databases (e.g., CCLE 2 ) that were generated using transcriptomic (Affymetrix) arrays. Because ...

Patients with pancreatic cancer, in particular pancreatic ductal adenocarcinoma (PDAC), have a ~6% chance of surviving 5 years after diagnosis. Approved drugs only add weeks or months to patient lifespan. PDAC is difficult to treat, in part because the tumor often has poor vascularization and dense extracellular matrix, which yield a hypoxic tumor microenvironment. Finding new drugs for PDAC is thus an unmet medical need. The G protein‐coupled receptor (GPCR) superfamily is the most frequently targeted class of proteins for FDA‐approved drugs. We hypothesized that one or more GPCR may be a novel therapeutic target for PDAC.Bioinformatic analysis of PDAC tumors in TCGA [The Cancer Genome Atlas] revealed prominent (~32‐fold) overexpression of H1 histamine receptor (HRH1) compared to normal pancreatic tissue [GTex database]. KRAS and p53 mutations occur, respectively, in ~70% and ~60% of PDAC tumors whereas increased HRH1 expression of HRH1 in 100% of tumor samples in TCGA. HRH1 is an attractive target for repurposing since many FDA approved antagonists are directed at this receptor. We thus sought to validate HRH1 expression in PDAC cells.Using qPCR, we found high HRH1 expression and low expression of HRH2‐4 in BxPC, AsPC‐1, and CAPAN‐2 (PDAC) cell lines and normal pancreatic ductal epithelial cells. Addition of histamine increased Ca++ in ASPC‐1 and CAPAN‐2 cells; this increase in Ca++ was blocked by multiple FDA‐approved HRH1 antihistamines. Histamine increased PDAC cell proliferation in cells grown in hypoxia but not normoxia. High expression of HRH1 in PDAC cells may thus confer a growth advantage for PDAC cells in hypoxic conditions. These preliminary data suggest that FDA‐approved HRH1 antihistamines are candidates for repurposing as novel therapeutics for the treatment of pancreatic cancer.Support or Funding InformationSupported by HHMI and an ASPET David Lehr AwardThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

G protein-coupled receptors (GPCRs), the largest family of membrane receptors, regulate numerous cellular functions and are drug targets for many disorders but not generally in cancer. We analyzed The Cancer Genome Atlas (TCGA) for GPCR mutations, copy number variation (CNV) and mRNA expression in 20 categories of solid tumors. We found that numerous GPCRs are frequently mutated, in particular, certain adhesion GPCRs (e.g.,GPR98 and GPR112), which appear to have a higher density of mutation events than other genes of similar length. Tumors with high mutational burden show a high frequency of such GPCR mutations that may result from DNA damage. CNV (especially amplifications and single-copy deletions) of GPCRs is widespread. In certain tumor types, particular GPCRs (e. g., GPR160) show high-level amplification in >30% of tumors. However, CNV does not appear to be a major factor in determining differential expression (DE) of GPCRs in tumors. Compared to RNA expression in normal tissues (GTEX database), most solid tumor types (including those accounting for the most annual deaths) differentially express >50 GPCRs, including 77 GPCRs with increased expression in at least one tumor type that are targets for approved drugs, providing opportunities for drug repurposing. DE of GPCRs is largely independent of tumor stage/grade, largely insensitive to specific driver mutations, and similar in primary and metastatic tumors, which both have high expression of numerous GPCRs in nearly all members within tumor populations. Cancer cells highly express most GPCRs overexpressed in tumors, making such GPCRs (especially those that are druggable) attractive candidates for further validation and functional studies. Multiple published studies provide functional data for certain such GPCRs. These findings imply a previously unappreciated role for GPCRs in solid tumors. Overexpressed GPCRs in tumors may regulate tumor biology as “functional oncogenes” and are potentially novel biomarkers and therapeutic targets, including for approved drugs. Citation Format: Krishna Sriram, Kevin Moyung, Ross Corriden, Paul Insel. Solid tumors have frequent mutation, copy number variation and differential mRNA expression of GPCRs: Are such GPCRs functional oncogenes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3293.