Gene Summary

Gene:GPRC5A; G protein-coupled receptor class C group 5 member A
Aliases: RAI3, TIG1, RAIG1, GPCR5A, PEIG-1
Summary:This gene encodes a member of the type 3 G protein-coupling receptor family, characterized by the signature 7-transmembrane domain motif. The encoded protein may be involved in interaction between retinoid acid and G protein signalling pathways. Retinoic acid plays a critical role in development, cellular growth, and differentiation. This gene may play a role in embryonic development and epithelial cell differentiation. [provided by RefSeq, Jul 2008]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:retinoic acid-induced protein 3
Source:NCBIAccessed: 31 August, 2019

Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 31 August 2019 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Lung Cancer
  • Cell Proliferation
  • Respiratory Mucosa
  • Base Sequence
  • Genetic Predisposition
  • G-Protein-Coupled Receptors
  • Up-Regulation
  • Tissue Array Analysis
  • DNA Sequence Analysis
  • Messenger RNA
  • Nitrosamines
  • MicroRNAs
  • Chromosome 12
  • Smoking
  • Apoptosis
  • Stomach Cancer
  • Cell Movement
  • Knockout Mice
  • Gene Expression Profiling
  • ErbB Receptors
  • Oligonucleotide Array Sequence Analysis
  • Down-Regulation
  • Western Blotting
  • Cancer Gene Expression Regulation
  • Mutation
  • Retinoids
  • Survival Rate
  • Nuclear Proteins
  • Genome-Wide Association Study
  • Breast Cancer
  • Single Nucleotide Polymorphism
  • Neoplasm Proteins
  • Whole Exome Sequencing
  • Epithelial Cells
  • Adenocarcinoma
  • Biomarkers, Tumor
  • Carcinogenesis
  • Transcription
  • Signal Transduction
Tag cloud generated 31 August, 2019 using data from PubMed, MeSH and CancerIndex

Latest Publications: GPRC5A (cancer-related)

Guo W, Hu M, Wu J, et al.
Gprc5a depletion enhances the risk of smoking-induced lung tumorigenesis and mortality.
Biomed Pharmacother. 2019; 114:108791 [PubMed] Related Publications
AIMS: Lung cancer remains the leading cause of cancer incidence and mortality. Although cigarette smoke is regarded as a high risk factor for lung tumor initiation, the role of the lung tumor suppressor GPRC5A in smoking-induced lung cancer is unclear.
MAIN METHODS: We obtained two lung cancer cohorts from the TCGA and GEO databases. Bioinformatics analysis showed differential gene expression in the cohorts. Quantitative real-time PCR, Western Blot and Gprc5a
KEY FINDINGS: Bioinformatics analysis showed that the smoking lung cancer patients with low expression of GPRC5A had poor overall survival compared to the patients with high GPRC5A expression. Further analysis revealed that cancer-related stemness pathways such as the Hippo signaling pathway were induced in smoking patients with low GPRC5A expression. Additionally, we detected enriched expression of WNT5A and DLX5 in normal human lung epithelial 16HBE cells and human lung cancer H1299 cells in vitro. A relationship between cigarette smoke extract (NNK) and lung tumor initiation was observed in Gprc5a
SIGNIFICANCE: The lung tumor suppressor gene GPRC5A played a protective role in cigarette smoke-induced lung tumor initiation, providing a target for the prevention of lung cancer development and monitoring of prognosis.

Duffy DL, Zhu G, Li X, et al.
Novel pleiotropic risk loci for melanoma and nevus density implicate multiple biological pathways.
Nat Commun. 2018; 9(1):4774 [PubMed] Free Access to Full Article Related Publications
The total number of acquired melanocytic nevi on the skin is strongly correlated with melanoma risk. Here we report a meta-analysis of 11 nevus GWAS from Australia, Netherlands, UK, and USA comprising 52,506 individuals. We confirm known loci including MTAP, PLA2G6, and IRF4, and detect novel SNPs in KITLG and a region of 9q32. In a bivariate analysis combining the nevus results with a recent melanoma GWAS meta-analysis (12,874 cases, 23,203 controls), SNPs near GPRC5A, CYP1B1, PPARGC1B, HDAC4, FAM208B, DOCK8, and SYNE2 reached global significance, and other loci, including MIR146A and OBFC1, reached a suggestive level. Overall, we conclude that most nevus genes affect melanoma risk (KITLG an exception), while many melanoma risk loci do not alter nevus count. For example, variants in TERC and OBFC1 affect both traits, but other telomere length maintenance genes seem to affect melanoma risk only. Our findings implicate multiple pathways in nevogenesis.

Greenhough A, Bagley C, Heesom KJ, et al.
Cancer cell adaptation to hypoxia involves a HIF-GPRC5A-YAP axis.
EMBO Mol Med. 2018; 10(11) [PubMed] Free Access to Full Article Related Publications
Hypoxia is a hallmark of solid tumours and a key physiological feature distinguishing cancer from normal tissue. However, a major challenge remains in identifying tractable molecular targets that hypoxic cancer cells depend on for survival. Here, we used SILAC-based proteomics to identify the orphan G protein-coupled receptor GPRC5A as a novel hypoxia-induced protein that functions to protect cancer cells from apoptosis during oxygen deprivation. Using genetic approaches

Song H, Sun B, Liao Y, et al.
GPRC5A deficiency leads to dysregulated MDM2 via activated EGFR signaling for lung tumor development.
Int J Cancer. 2019; 144(4):777-787 [PubMed] Related Publications
GPRC5A, a retinoic acid induced gene, is preferentially expressed in lung tissue. Gprc5a gene deletion leads to spontaneous lung tumor development. However, the mechanism of Gprc5a-mediated lung tumor suppression is not fully understood. Here we showed that MDM2, a p53-negative regulator, was dysregulated in Gprc5a-knockout (ko) mouse tracheal epithelial cells (KO-MTEC) compared to wild type ones. Targeting MDM2 in 1601-a Gprc5a-ko mouse derived lung tumor cell line-and A549-human lung cancer cells, by MDM2 inhibitor Nutlin-3a or small hairpin RNA (sh-RNA)-restored p53 signaling pathway, reduced cancer stem cell markers, and inhibited tumorigenicity. This suggests that dysregulated MDM2 pathway is essential for the oncogenic activities of these cells. MDM2 was found to be stabilized mainly by activated EGFR signaling as targeting EGFR by Erlotinib or sh-RNA repressed MDM2 in a transcription-independent manner. Importantly, overexpression of MDM2 and reduced GPRC5A expression at both protein and mRNA levels were frequently found in clinical human lung cancer tissues. Taken together, GPRC5A deficiency contributes to dysregulated MDM2 via activated EGFR signaling, which promotes lung tumor development.

Liu B, Yang H, Pilarsky C, Weber GF
The Effect of GPRC5a on the Proliferation, Migration Ability, Chemotherapy Resistance, and Phosphorylation of GSK-3β in Pancreatic Cancer.
Int J Mol Sci. 2018; 19(7) [PubMed] Free Access to Full Article Related Publications
Pancreatic cancer (PaCa) is the fourth leading cause of cancer-related death, and personalized targeted cancer therapy is becoming a promising treatment strategy for PaCa. The central approach of targeted therapy is to find a targetable key and an effective targeting method. In this study, the importance of

Wang CH, Shyu RY, Wu CC, et al.
Tazarotene-Induced Gene 1 Interacts with DNAJC8 and Regulates Glycolysis in Cervical Cancer Cells.
Mol Cells. 2018; 41(6):562-574 [PubMed] Free Access to Full Article Related Publications
The tazarotene-induced gene 1 (TIG1) protein is a retinoid-inducible growth regulator and is considered a tumor suppressor. Here, we show that DnaJ heat shock protein family member C8 (DNAJC8) is a TIG1 target that regulates glycolysis. Ectopic DNAJC8 expression induced the translocation of pyruvate kinase M2 (PKM2) into the nucleus, subsequently inducing glucose transporter 1 (GLUT1) expression to promote glucose uptake. Silencing either DNAJC8 or PKM2 alleviated the upregulation of GLUT1 expression and glucose uptake induced by ectopic DNAJC8 expression. TIG1 interacted with DNAJC8 in the cytosol, and this interaction completely blocked DNAJC8-mediated PKM2 translocation and inhibited glucose uptake. Furthermore, increased glycose uptake was observed in cells in which TIG1 was silenced. In conclusion, TIG1 acts as a pivotal repressor of DNAJC8 to enhance glucose uptake by partially regulating PKM2 translocation.

Kantrowitz J, Sinjab A, Xu L, et al.
Genome-Wide Gene Expression Changes in the Normal-Appearing Airway during the Evolution of Smoking-Associated Lung Adenocarcinoma.
Cancer Prev Res (Phila). 2018; 11(4):237-248 [PubMed] Free Access to Full Article Related Publications
Smoking perpetuates in cytologically normal airways a molecular "field of injury" that is pertinent to lung cancer and early detection. The evolution of airway field changes prior to lung oncogenesis is poorly understood largely due to the long latency of lung cancer in smokers. Here, we studied airway expression changes prior to lung cancer onset in mice with knockout of the

Shrestha S, Yang CD, Hong HC, et al.
Integrated MicroRNA-mRNA Analysis Reveals miR-204 Inhibits Cell Proliferation in Gastric Cancer by Targeting CKS1B, CXCL1 and GPRC5A.
Int J Mol Sci. 2017; 19(1) [PubMed] Free Access to Full Article Related Publications
Gastric cancer (GC) is the second most frequent cause of cancer-related deaths worldwide. MicroRNAs are single-stranded RNA molecules of 21-23 nucleotides that regulate target gene expression through specific base-pairing interactions between miRNA and untranslated regions of targeted mRNAs. In this study, we generated a multistep approach for the integrated analysis of miRNA and mRNA expression. First, both miRNA and mRNA expression profiling datasets in gastric cancer from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) identified 79 and 1042 differentially expressed miRNAs and mRNAs, respectively, in gastric cancer. Second, inverse correlations between miRNA and mRNA expression levels identified 3206 miRNA-mRNA pairs combined with 79 dysregulated miRNAs and their 774 target mRNAs predicted by three prediction tools, miRanda, PITA, and RNAhybrid. Additionally, miR-204, which was found to be down-regulated in gastric cancer, was ectopically over-expressed in the AGS gastric cancer cell line and all down-regulated targets were identified by RNA sequencing (RNA-seq) analysis. Over-expression of miR-204 reduced the gastric cancer cell proliferation and suppressed the expression of three targets which were validated by qRT-PCR and luciferase assays. For the first time, we identified that

Huebner H, Strick R, Wachter DL, et al.
Hypermethylation and loss of retinoic acid receptor responder 1 expression in human choriocarcinoma.
J Exp Clin Cancer Res. 2017; 36(1):165 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Human placental development resembles tumorigenesis, due to the invasive and fusogenic potential of trophoblasts. However, these features are tightly controlled in trophoblasts. Disturbance of this spatial and temporal regulation is thought to contribute to the rare formation of choriocarcinomas. Promoter hypermethylation and loss of the tumor suppressor Retinoic acid receptor responder 1 (RARRES1) were shown to contribute to cancer progression. Our study investigated the epigenetic and transcriptional regulation of RARRES1 in healthy human placenta in comparison to choriocarcinoma cell lines and cases.
METHODS: Three choriocarcinoma cell lines (Jeg-3, JAR and BeWo) were treated with three different retinoic acid derivates (Am580, Tazarotene and all-trans retinoic acid) and 5-aza-2'-deoxycytidine. We analyzed RARRES1 promoter methylation by pyrosequencing and performed realtime-PCR quantification to determine RARRES1 expression in placental tissue and trophoblastic cell lines. Additionally, RARRES1 was stained in healthy placentas and in biopsies of choriocarcinoma cases (n = 10) as well as the first trimester trophoblast cell line Swan71 by immunofluorescence and immunohistochemistry.
RESULTS: In the choriocarcinoma cell lines, RARRES1 expression could not be induced by sole retinoic acid treatment. Stimulation with 5-aza-2'-deoxycytidine significantly induced RARRES1 expression, which then could be further increased with Am580, Tazarotene and all-trans retinoic acid. In comparison to healthy placenta, choriocarcinoma cell lines showed a hypermethylation of the RARRES1 promoter, which correlated with a reduced RARRES1 expression. In concordance, RARRES1 protein expression was lost in choriocarcinoma tissue. Additionally, in the trophoblastic cell line Swan71, we found a significant induction of RARRES1 expression with increased cell density, during mitosis and in syncytial knots.
CONCLUSIONS: Our findings showed that RARRES1 expression is absent in choriocarcinoma due to promoter methylation. Based on our analysis, we hypothesize that RARRES1 might exert tumor suppressive functions in multiple cellular processes (e.g. cell cycle regulation, adhesion, invasion and apoptosis).

Lu N, Wang J, Zhu B, et al.
Whole-exome sequencing to identify novel mutations of nevoid basal cell carcinoma syndrome in a Chinese population.
Cancer Biomark. 2017; 21(1):161-168 [PubMed] Related Publications
BACKGROUND: Nevoid basal cell carcinoma syndrome (NBCCS) is a rare autosomal dominant disease with a complex genetic etiology. Although three causative genes (PTCH1, PTCH2, SUFU) have been identified through linkage analysis and Sanger sequencing, the genetic background of NBCCS hasn't been fully understood.
METHODS: We performed a whole-exome sequencing (WES) in a Han Chinese NBCCS family and two unaffected volunteers to search for its causative gene. Bioinformatic analysis was used to select candidate genes and analyze the functional networks of each candidate gene.
RESULTS: A total of 8 single-nucleotide variants (SNVs) were detected in PTCH1, PTCH2 and SUFU in all the 5 subjects, however none of them was considered the pathogenic genetic mutation in this NBCCS family. The following filtering process identified 17 novel candidate genes (GBP3, AMPD1, ASPM, UNC5C, RBM46, HSPA1L, PNPLA1, GPR126, AP5Z1, ZFHX4, KIF24, C10orf128, COX15, GPRC5A, UGGT2, RHBDF1, RPUSD1). Among them ZFHX4 had been already identified as a new basal cell carcinoma susceptibility loci through a genome-wide association study (GWAS) and was considered the most likely pathogenic gene for this NBCCS family. The functional network analysis revealed that ZFHX4 may be involved in notch signaling pathway.
CONCLUSIONS: Our study reported the identification of 17 novel candidate genes in a Han Chinese family through WES. ZFHX4 may be a susceptibility gene for NBCCS in Chinese population.

Fujimoto J, Nunomura-Nakamura S, Liu Y, et al.
Development of Kras mutant lung adenocarcinoma in mice with knockout of the airway lineage-specific gene Gprc5a.
Int J Cancer. 2017; 141(8):1589-1599 [PubMed] Free Access to Full Article Related Publications
Despite the urgency for prevention and treatment of lung adenocarcinoma (LUAD), we still do not know drivers in pathogenesis of the disease. Earlier work revealed that mice with knockout of the G-protein coupled receptor Gprc5a develop late onset lung tumors including LUADs. Here, we sought to further probe the impact of Gprc5a expression on LUAD pathogenesis. We first surveyed GPRC5A expression in human tissues and found that GPRC5A was markedly elevated in human normal lung relative to other normal tissues and was consistently downregulated in LUADs. In sharp contrast to wild-type littermates, Gprc5a

Zhang L, Li L, Gao G, et al.
Elevation of GPRC5A expression in colorectal cancer promotes tumor progression through VNN-1 induced oxidative stress.
Int J Cancer. 2017; 140(12):2734-2747 [PubMed] Related Publications
The clearance of oxidative stress compounds is critical for the protection of the organism from malignancy, but how this key physiological process is regulated is not fully understood. Here, we found that the expression of GPRC5A, a well-characterized tumor suppressor in lung cancer, was elevated in colorectal cancer tissues in patients. In both cancer cell lines and a colitis-associated cancer model in mice, we found that GPRC5A deficiency reduced cell proliferation and increased cell apoptosis as well as inhibited tumorigenesis in vivo. Through RNA-Seq transcriptome analysis, we identified oxidative stress associated pathways were dysregulated. Moreover, in GPRC5A deficient cells and mouse tissues, the oxidative agents were reduced partially due to increased glutathione (GSH) level. Mechanistically, GPRC5A regulates NF-κB mediated Vanin-1 expression which is the predominant enzyme for cysteamine generation. Administration of cystamine (the disulfide form of cysteamine) in GPRC5A deficient cell lines inhibited γ-GCS activity, leading to reduction of GSH level and increase of cell growth. Taken together, our studies suggest that GPRC5a is a potential biomarker for colon cancer and promotes tumorigenesis through stimulation of Vanin-1 expression and oxidative stress in colitis associated cancer. This study revealed an unexpected oncogenic role of GPRC5A in colorectal cancer suggesting there are complicated functional and molecular mechanism differences of this gene in distinct tissues.

Jahny E, Yang H, Liu B, et al.
The G Protein-Coupled Receptor RAI3 Is an Independent Prognostic Factor for Pancreatic Cancer Survival and Regulates Proliferation via STAT3 Phosphorylation.
PLoS One. 2017; 12(1):e0170390 [PubMed] Free Access to Full Article Related Publications
Pancreatic Ductal Adenocarcinoma (PDAC) is one of the deadliest tumors worldwide. Understanding the function of gene expression alterations is a prerequisite for developing new strategies in diagnostic and therapy. GPRC5A (RAI3), coding for a seven transmembrane G protein-coupled receptor is known to be overexpressed in pancreatic cancer and might be an interesting candidate for therapeutic intervention. Expression levels of RAI3 were compared using a tissue microarray of 435 resected patients with pancreatic cancer as well as 209 samples from chronic pancreatitis (CP), intra-ductal papillary mucinous neoplasm (IPMN) and normal pancreatic tissue. To elucidate the function of RAI3 overexpression, siRNA based knock-down was used and transfected cells were analyzed using proliferation and migration assays. Pancreatic cancer patients showed a statistically significant overexpression of RAI3 in comparison to normal and chronic pancreatitis tissue. Especially the loss of apical RAI3 expression represents an independent prognostic parameter for overall survival of patients with pancreatic cancer. Suppression of GPRC5a results in decreased cell growth, proliferation and migration in pancreatic cancer cell lines via a STAT3 modulated pathway, independent from ERK activation.

Sun B, Guo W, Hu S, et al.
Gprc5a-knockout mouse lung epithelial cells predicts ceruloplasmin, lipocalin 2 and periostin as potential biomarkers at early stages of lung tumorigenesis.
Oncotarget. 2017; 8(8):13532-13544 [PubMed] Free Access to Full Article Related Publications
Lung cancer is the leading cause of cancer death. As most of lung cancer patients were diagnosed with the advanced stage, early detection is considered as the most effective strategy to reduce high mortality. Thus, it is desirable to identify specific biomarkers at early stages of lung tumorigenesis. GPRC5A is a lung tumor suppressor gene. GPRC5A deficiency is linked to lung cancer development. We hyposthesized that, dysregulated gene expression that results from Gprc5a deficiency may provide potential biomarkers at early stages of lung tumorigenesis. By analysis of top 20 upregulated genes in mouse tracheal epithelial cells (MTEC) of Gprc5a knockout (KO) vs wild-type (WT), we found that ceruloplasmin, lipocalin-2, and periostin are not only upregulated in lung epithelial cells of Gprc5a-ko mice, but also expressed at high levels in lung tumor tissues of Gprc5a-ko mice. This suggests that increased expression of these genes is associated with lung tumorigenesis. Importantly, expression of ceruloplasmin, lipocalin-2, and periostin has also been found to be significantly increased, both at mRNA and protein levels, in the lung tissues from NSCLC patients, which is correlated with repressed GPRC5A. Thus, dysregulated ceruloplasmin, lipocalin-2, and periostin may be used as potential biomarkers at early stages of lung tumorigenesis.

Shyu RY, Wang CH, Wu CC, et al.
Tazarotene-Induced Gene 1 Enhanced Cervical Cell Autophagy through Transmembrane Protein 192.
Mol Cells. 2016; 39(12):877-887 [PubMed] Free Access to Full Article Related Publications
Tazarotene-induced gene 1 (TIG1) is a retinoic acid-inducible protein that is considered a putative tumor suppressor. The expression of TIG1 is decreased in malignant prostate carcinoma or poorly differentiated colorectal adenocarcinoma, but TIG1 is present in benign or well-differentiated tumors. Ectopic TIG1 expression led to suppression of growth in cancer cells. However, the function of TIG1 in cell differentiation is still unknown. Using a yeast two-hybrid system, we found that transmembrane protein 192 (TMEM192) interacted with TIG1. We also found that both TIG1A and TIG1B isoforms interacted and co-localized with TMEM192 in HtTA cervical cancer cells. The expression of TIG1 induced the expression of autophagy-related proteins, including Beclin-1 and LC-3B. The silencing of TMEM192 reduced the TIG1-mediated upregulation of autophagic activity. Furthermore, silencing of either TIG1 or TMEM192 led to alleviation of the upregulation of autophagy induced by all-trans retinoic acid. Our results demonstrate that the expression of TIG1 leads to cell autophagy through TMEM192. Our study also suggests that TIG1 and TMEM192 play an important role in the all-trans retinoic acid-mediated upregulation of autophagic activity.

Yang L, Ma T, Zhang J
GPRC5A exerts its tumor-suppressive effects in breast cancer cells by inhibiting EGFR and its downstream pathway.
Oncol Rep. 2016; 36(5):2983-2990 [PubMed] Related Publications
G-protein-coupled receptor family C group 5 member A (GPRC5A) is a member of the type 3-G protein‑coupling receptor family. Previous studies have observed dysregulated expression of GPRC5A in several malignant diseases which suggests that GPRC5A may participate in tumor progression. However, these results are controversial. In the present study, we explored the biological functions of GPRC5A in breast cancer cells and aimed to uncover the related molecular mechanisms. Our results demonstrated that GPRC5A is a tumor suppressor in EGFR-expressing breast cancer cells. GPRC5A knockdown in EGFR-expressing MDA-MB-231 cells promoted colony formation, cell proliferation, cell migration and invasion, while GPRC5A suppression had no impact on MCF7 cells, which express no EGFR. Furthermore, GPRC5A knockdown enhanced EGF-induced EGFR and its downstream signaling activation. Inhibition of EGFR phosphorylation in MDA-MB-231 cells suppressed the tumorigenic effects of GPRC5A knockdown. Moreover, GPRC5A knockdown exhibited an oncogenic role in MCF7 cells transfected with the EGFR-expressing plasmid. Taken together, our results implicate GPRC5A as a tumor suppressor in breast cancer cells, and GPRC5A exerts its tumor-suppressive function by inhibiting EGFR and its downstream pathway.

Ahmad AS, Vasiljević N, Carter P, et al.
A novel DNA methylation score accurately predicts death from prostate cancer in men with low to intermediate clinical risk factors.
Oncotarget. 2016; 7(44):71833-71840 [PubMed] Free Access to Full Article Related Publications
Clinically aggressive disease behavior is difficult to predict in men with low to intermediate clinical risk prostate cancer and methylation biomarkers may be a valuable adjunct for assessing the management of these patients. We set to evaluate the utility of DNA methylation to identify high risk disease in men currently considered as low or intermediate risk. DNA was extracted from formalin-fixed paraffin-embedded transurethral prostate resection tissues collected during the years 1990-96 in a watchful-waiting cohort of men in the UK. The primary end point was death of prostate cancer, assessed by reviewing cancer registry records from 2009. Methylation was quantified by pyrosequencing assays for six genes (HSPB1, CCND2, TIG1, DPYS, PITX2, and MAL) with established biomarker value in prostate cancer. A novel prognostic methylation score was developed by multivariate Cox modelling using the six methylation biomarkers in 385 men with low-and-intermediate clinical risk variables and its prognostic value compared to two previously defined clinically-derived risk scores. Methylation score was the most significant variable in univariate and bivariate analysis in men with low-to-intermediate CAPRA risk score. When combined with CAPRA score the hazard ratio was 2.02; 95% confidence interval, 1.40-2.92. For a methylation score sensitivity of 83% the specificity was 44%, while the maximum achieved sensitivity by CAPRA was 68% at a specificity of 44%. The derived methylation score is a strong predictor of aggressive prostate cancer that could have an important role in directing the management of patients with low-to-intermediate risk disease. The estimated areas under the curve (AUC) at 10 years of follow-up were 0.62 (95% CI: 0.51, 0.70) and 0.74 (95% CI: 0.65, 0.82) for CAPRA, and combined (CAPRA + methylation) risk score (CRS) respectively.

Zhou H, Telonis AG, Jing Y, et al.
GPRC5A is a potential oncogene in pancreatic ductal adenocarcinoma cells that is upregulated by gemcitabine with help from HuR.
Cell Death Dis. 2016; 7:e2294 [PubMed] Free Access to Full Article Related Publications
GPRC5A is an orphan G-protein coupled receptor with an intriguing dual behavior, acting as an oncogene in some cancers and as a tumor suppressor in other cancers. In the pancreatic cancer context, very little is known about GPRC5A. By analyzing messenger RNA (mRNA) expression data from 675 human cancer cell lines and 10 609 samples from The Cancer Genome Atlas (TCGA) we found that GPRC5A's abundance in pancreatic cancer is highest (cell lines) or second highest (TCGA) among all tissues and cancer types. Further analyses of an independent set of 252 pancreatic normal and cancer samples showed GPRC5A mRNA to be more than twofold upregulated in primary tumor samples compared with normal pancreas (P-value<10(-5)), and even further upregulated in pancreatic cancer metastases to various organs (P-value=0.0021). Immunostaining of 208 cores (103 samples) of a tissue microarray showed generally low expression of GPRC5A protein in normal pancreatic ductal cells; on the other hand, in primary and metastatic samples, GPRC5A protein levels were dramatically increased in pancreatic ductal cells. In vitro studies of multiple pancreatic cancer cell lines showed that an increase in GPRC5A protein levels promoted pancreatic cancer cell growth and migration. Unexpectedly, when we treated pancreatic cancer cell lines with gemcitabine (2',2'-difluorodeoxycytidine), we observed an increase in GPRC5A protein abundance. On the other hand, when we knocked down GPRC5A we sensitized pancreatic cancer cells to gemcitabine. Through further experimentation we showed that the monotonic increase in GPRC5A protein levels that we observe for the first 18 h following gemcitabine treatment results from interactions between GPRC5A's mRNA and the RNA-binding protein HuR, which is an established key mediator of gemcitabine's efficacy in cancer cells. As we discovered, the interaction between GPRC5A and HuR is mediated by at least one HuR-binding site in GPRC5A's mRNA. Our findings indicate that GPRC5A is part of a complex molecular axis that involves gemcitabine and HuR, and, possibly, other genes. Further work is warranted before it can be established unequivocally that GPRC5A is an oncogene in the pancreatic cancer context.

Yang Z, Li C, Fan Z, et al.
Single-cell Sequencing Reveals Variants in ARID1A, GPRC5A and MLL2 Driving Self-renewal of Human Bladder Cancer Stem Cells.
Eur Urol. 2017; 71(1):8-12 [PubMed] Related Publications
Cancer stem cells are considered responsible for many important aspects of tumors such as their self-renewal, tumor-initiating, drug-resistance and metastasis. However, the genetic basis and origination of human bladder cancer stem cells (BCSCs) remains unknown. Here, we conducted single-cell sequencing on 59 cells including BCSCs, bladder cancer non-stem cells (BCNSCs), bladder epithelial stem cells (BESCs) and bladder epithelial non-stem cells (BENSCs) from three bladder cancer (BC) specimens. Specifically, BCSCs demonstrate clonal homogeneity and suggest their origin from BESCs or BCNSCs through phylogenetic analysis. Moreover, 21 key altered genes were identified in BCSCs including six genes not previously described in BC (ETS1, GPRC5A, MKL1, PAWR, PITX2 and RGS9BP). Co-mutations of ARID1A, GPRC5A and MLL2 introduced by CRISPR/Cas9 significantly enhance the capabilities of self-renewal and tumor-initiating of BCNSCs. To our knowledge, our study first provides an overview of the genetic basis of human BCSCs with single-cell sequencing and demonstrates the biclonal origin of human BCSCs via evolution analysis.
PATIENT SUMMARY: Human bladder cancer stem cells show the high level of consistency and may derived from bladder epithelial stem cells or bladder cancer non-stem cells. Mutations of ARID1A, GPRC5A and MLL2 grant bladder cancer non-stem cells the capability of self-renewal.

Wang J, Farris AB, Xu K, et al.
GPRC5A suppresses protein synthesis at the endoplasmic reticulum to prevent radiation-induced lung tumorigenesis.
Nat Commun. 2016; 7:11795 [PubMed] Free Access to Full Article Related Publications
GPRC5A functions as a lung tumour suppressor to prevent spontaneous and environmentally induced lung carcinogenesis; however, the underlying mechanism remains unclear. Here we reveal that GPRC5A at the endoplasmic reticulum (ER) membrane suppresses synthesis of the secreted or membrane-bound proteins including a number of oncogenes, the most important one being Egfr. The ER-located GPRC5A disturbs the assembly of the eIF4F-mediated translation initiation complex on the mRNA cap through directly binding to the eIF4F complex with its two middle extracellular loops. Particularly, suppression of EGFR by GPRC5A contributes significantly to preventing ionizing radiation (IR)-induced lung tumorigenesis. Thus, GPRC5A deletion enhances IR-promoted EGFR expression through an increased translation rate, thereby significantly increasing lung tumour incidence in Gprc5a(-/-) mice. Our findings indicate that under-expressed GPRC5A during lung tumorigenesis enhances any transcriptional stimulation through an active translational status, which can be used to control oncogene expression and potentially the resulting related disease.

Liu H, Zhang Y, Hao X, et al.
GPRC5A overexpression predicted advanced biological behaviors and poor prognosis in patients with gastric cancer.
Tumour Biol. 2016; 37(1):503-10 [PubMed] Related Publications
G protein-coupled receptor, family C, group 5, member A (GPRC5A) had received attentions for its role in carcinogenesis and prognostic values in several types of cancer. However, the functional roles of GPRC5A in gastric cancer (GC) had never been elucidated. The expression levels of GPRC5A were detected by real-time quantitative reverse transcription PCR and Western blot in GC tissues and adjacent non-tumor tissues. GPRC5A expression in tissue sections of 106 GC samples was evaluated using immunohistochemistry. The staining results were compared with clinicopathological factors and to the prognosis of GC patients. The mRNA and protein expression levels of GPRC5A in gastric cancer tissues were higher than those in adjacent non-tumor tissues. Positive GPRC5A expression was significantly correlated with larger size of primary tumor, diffuse type (Lauren's classification), deeper serosal invasion, and more lymph node metastasis. In addition, Kaplan-Meier curve analysis demonstrated that GC patients with positive GPRC5A expression had poor prognosis than those with negative GPRC5A expression. GPRC5A expression was identified as an independent factor of the overall survival in GC patients by multivariate Cox analysis. Further, the overall survival difference existed between patients with GPRC5A positive and negative groups in GC patients with lymph node metastasis. Our results suggested that elevated levels of GPRC5A played significant roles in GC progression. GPRC5A could serve as a prognostic biomarker of GC.

Lin X, Zhong S, Ye X, et al.
EGFR phosphorylates and inhibits lung tumor suppressor GPRC5A in lung cancer.
Mol Cancer. 2014; 13:233 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: GPRC5A is a retinoic acid inducible gene that is preferentially expressed in lung tissue. Gprc5a- knockout mice develop spontaneous lung cancer, indicating Gprc5a is a lung tumor suppressor gene. GPRC5A expression is frequently suppressed in majority of non-small cell lung cancers (NSCLCs), however, elevated GPRC5A is still observed in a small portion of NSCLC cell lines and tumors, suggesting that the tumor suppressive function of GPRC5A is inhibited in these tumors by an unknown mechanism.
METHODS: In this study, we examined EGF receptor (EGFR)-mediated interaction and tyrosine phosphorylation of GPRC5A by immunoprecipitation (IP)-Westernblot. Tyrosine phosphorylation of GPRC5A by EGFR was systematically identified by site-directed mutagenesis. Cell proliferation, migration, and anchorage-independent growth of NSCLC cell lines stably transfected with wild-type GPRC5A and mutants defective in tyrosine phosphorylation were assayed. Immunohistochemical (IHC) staining analysis with specific antibodies was performed to measure the total and phosphorylated GPRC5A in both normal lung and lung tumor tissues.
RESULT: We found that EGFR interacted with GPRC5A and phosphorylated it in two conserved double-tyrosine motifs, Y317/Y320 and Y347/ Y350, at the C-terminal tail of GPRC5A. EGF induced phosphorylation of GPRC5A, which disrupted GPRC5A-mediated suppression on anchorage-independent growth of NSCLC cells. On contrary, GPRC5A-4 F, in which the four tyrosine residues have been replaced with phenylalanine, was resistant to EGF-induced phosphorylation and maintained tumor suppressive activities. Importantly, IHC analysis with anti-Y317/Y320-P sites showed that GPRC5A was non-phosphorylated in normal lung tissue whereas it was highly tyrosine-phosphorylated in NSCLC tissues.
CONCLUSION: GPRC5A can be inactivated by receptor tyrosine kinase via tyrosine phosphorylation. Thus, targeting EGFR can restore the tumor suppressive functions of GPRC5A in lung cancer.

Kume H, Muraoka S, Kuga T, et al.
Discovery of colorectal cancer biomarker candidates by membrane proteomic analysis and subsequent verification using selected reaction monitoring (SRM) and tissue microarray (TMA) analysis.
Mol Cell Proteomics. 2014; 13(6):1471-84 [PubMed] Free Access to Full Article Related Publications
Recent advances in quantitative proteomic technology have enabled the large-scale validation of biomarkers. We here performed a quantitative proteomic analysis of membrane fractions from colorectal cancer tissue to discover biomarker candidates, and then extensively validated the candidate proteins identified. A total of 5566 proteins were identified in six tissue samples, each of which was obtained from polyps and cancer with and without metastasis. GO cellular component analysis predicted that 3087 of these proteins were membrane proteins, whereas TMHMM algorithm predicted that 1567 proteins had a transmembrane domain. Differences were observed in the expression of 159 membrane proteins and 55 extracellular proteins between polyps and cancer without metastasis, while the expression of 32 membrane proteins and 17 extracellular proteins differed between cancer with and without metastasis. A total of 105 of these biomarker candidates were quantitated using selected (or multiple) reaction monitoring (SRM/MRM) with stable synthetic isotope-labeled peptides as an internal control. The results obtained revealed differences in the expression of 69 of these proteins, and this was subsequently verified in an independent set of patient samples (polyps (n = 10), cancer without metastasis (n = 10), cancer with metastasis (n = 10)). Significant differences were observed in the expression of 44 of these proteins, including ITGA5, GPRC5A, PDGFRB, and TFRC, which have already been shown to be overexpressed in colorectal cancer, as well as proteins with unknown function, such as C8orf55. The expression of C8orf55 was also shown to be high not only in colorectal cancer, but also in several cancer tissues using a multicancer tissue microarray, which included 1150 cores from 14 cancer tissues. This is the largest verification study of biomarker candidate membrane proteins to date; our methods for biomarker discovery and subsequent validation using SRM/MRM will contribute to the identification of useful biomarker candidates for various cancers. Data are available via ProteomeXchange with identifier PXD000851.

Sokolenko AP, Bulanova DR, Iyevleva AG, et al.
High prevalence of GPRC5A germline mutations in BRCA1-mutant breast cancer patients.
Int J Cancer. 2014; 134(10):2352-8 [PubMed] Related Publications
In a search for new breast cancer (BC) predisposing genes, we performed a whole exome sequencing analysis using six patient samples of familial BC and identified a germline inactivating mutation c.183delG [p. Arg61fs] in an orphan G protein-coupled receptor GPRC5A. An extended case-control study revealed a tenfold enrichment for this mutation in BC patients carrying the 5382insC allele of BRCA1, the major founder mutation in the Russian population, compared to wild-type BRCA1 BC cases [6/117 (5.1%) vs. 8/1578 (0.5%), p = 0.0002]. In mammary tumors (n = 60), the mRNA expression of GPRC5A significantly correlated with that of BRCA1 (p = 0.00018). In addition, the amount of GPRC5A transcript was significantly lower in BC obtained from BRCA1 mutation carriers (n = 17) compared to noncarriers (n = 93) (p = 0.026). Accordingly, a siRNA-mediated knockdown of either BRCA1 or GPRC5A in the MDA-MB-231 human BC cell line reduced expression of GPRC5A or BRCA1, respectively. Knockdown of GPRC5A also attenuated radiation-induced BRCA1- and RAD51-containing nuclear DNA repair foci. Taken together, these data suggest that GPRC5A is a modifier of BC risk in BRCA1 mutation carriers and reveals a functional interaction of these genes.

Xin H, Wang K, Hu G, et al.
Establishment and characterization of 7 novel hepatocellular carcinoma cell lines from patient-derived tumor xenografts.
PLoS One. 2014; 9(1):e85308 [PubMed] Free Access to Full Article Related Publications
Hepatocellular carcinoma (HCC) is a common cancer with poor prognosis worldwide and the molecular mechanism is not well understood. This study aimed to establish a collection of human HCC cell lines from patient-derived xenograft (PDX) models. From the 20 surgical HCC sample collections, 7 tumors were successfully developed in immunodeficient mice and further established 7 novel HCC cell lines (LIXC002, LIXC003, LIXC004, LIXC006, LIXC011, LIXC012 and CPL0903) by primary culture. The characterization of cell lines was defined by morphology, growth kinetics, cell cycle, chromosome analysis, short tandem repeat (STR) analysis, molecular profile, and tumorigenicity. Additionally, response to clinical chemotherapeutics was validated both in vitro and in vivo. STR analysis indicated that all cell lines were unique cells different from known cell lines and free of contamination by bacteria or mycoplasma. The other findings were quite heterogeneous between individual lines. Chromosome aberration could be found in all cell lines. Alpha-fetoprotein was overexpressed only in 3 out of 7 cell lines. 4 cell lines expressed high level of vimentin. Ki67 was strongly stained in all cell lines. mRNA level of retinoic acid induced protein 3 (RAI3) was decreased in all cell lines. The 7 novel cell lines showed variable sensitivity to 8 tested compounds. LIXC011 and CPL0903 possessed multiple drug resistance property. Sorafenib inhibited xenograft tumor growth of LIXC006, but not of LIXC012. Our results indicated that the 7 novel cell lines with low passage maintaining their clinical and pathological characters could be good tools for further exploring the molecular mechanism of HCC and anti-cancer drug screening.

Moritz R, Ellinger J, Nuhn P, et al.
DNA hypermethylation as a predictor of PSA recurrence in patients with low- and intermediate-grade prostate cancer.
Anticancer Res. 2013; 33(12):5249-54 [PubMed] Related Publications
BACKGROUND: DNA CpG island hypermethylation causes gene silencing and is a common event in prostate carcinogenesis and progression. We investigated its role as a possible prognostic marker in patients with PCA Gleason score ≤7.
PATIENTS AND METHODS: We used a quantitative, methylation-specific PCR to analyze methylation patterns at five gene loci (APC, GSTP1, PTGS2, RARbeta and TIG1) in 84 prostate cancer (PCA) tissues (Gleason Score ≤7). Methylation was correlated with established clinico-pathological parameters (preoperative PSA, pathological Gleason score, extraprostatic extension, seminal vesicle penetration, lymph node involvement, surgical margins and age) and PSA recurrence.
RESULTS: DNA hypermethylation was frequently detected at APC (95.2%), GSTP1 (84.5%), PTGS2 (100%), RAR-beta (81.0%) and TIG1 (95.2%). DNA hypermethylation was correlated with Gleason Score (p=0.027; PTGS2) and lymph node involvement (p=0.024; RARbeta). High methylation levels at RARbeta (p=0.023) was a significant predictor of PSA recurrence following radical prostatectomy.
CONCLUSION: The analysis of DNA hypermethylation provides prognostic information in prognosis of low- and intermediate-grade PCA.

Chen XH, Wu WG, Ding J
Aberrant TIG1 methylation associated with its decreased expression and clinicopathological significance in hepatocellular carcinoma.
Tumour Biol. 2014; 35(2):967-71 [PubMed] Related Publications
Recently, it has been reported that tazarotene-induced gene 1 (TIG1) methylation was frequently detected in a variety of human cancers. However, the relationship between the TIG1 methylation and the characteristics of hepatocellular carcinoma (HCC) remains unknown. The aim of present study was to observe the promoter methylation of TIG1 in HCC tissues and assess its prognostic significance for HCC. Real-time quantitative polymerase chain reaction and methylation-specific polymerase chain reaction were used, respectively, to examine the mRNA expression and methylation status of TIG1 in 91 pairs of HCC and adjacent noncancerous tissues. The mRNA expression level of TIG1 was significantly lower in HCC tissues than in adjacent noncancerous tissues. The rate of TIG1 promoter methylation was significantly higher in HCC tissues than in adjacent noncancerous tissues (P < 0.001). A strong correlation between downregulation and promoter methylation was found in these tumors (P < 0.001). More importantly, TIG1 methylation status was related to tumor size (P = 0.015), histological differentiation (P = 0.004), and tumor stage (P < 0.001). Kaplan-Meier survival analysis showed that TIG1 promoter hypermethylation was associated with a worse outcome in patients with HCC. Further, Cox multivariate analysis indicated that TIG1 methylation status was an independent prognostic factor for the overall survival rate of HCC patients. In conclusion, our data suggested that epigenetic silencing of TIG1 gene expression by promoter hypermethylation may play an important role in HCC.

Liu SL, Zhong SS, Ye DX, et al.
Repression of G protein-coupled receptor family C group 5 member A is associated with pathologic differentiation grade of oral squamous cell carcinoma.
J Oral Pathol Med. 2013; 42(10):761-8 [PubMed] Related Publications
BACKGROUND: G protein-coupled receptor family C group 5 member A (GPRC5A), a member of G protein-coupled receptor family, has been shown to function as a tumor suppressor in lung tissue. The biological functions of GPRC5A have therefore been linked to lung tissue. However, the biological significance of this gene product remains obscure. In this study, we investigated the expression of GPRC5A proteins in normal oral tissue and oral squamous cell carcinoma (OSCC), and we characterized its biological activity in OSCC cell lines.
METHODS: Western blot analysis and immunohistochemical staining were used to investigate the expression of GPRC5A in both OSCC cell lines and clinical samples. GPRC5A stable transfectants and their parental OSCC cells were characterized for their biological activities in anchorage-independent growth.
RESULTS: High levels of immunohistochemical GPRC5A expression were detected in normal oral tissue, especially differentiated area. In contrast, GPRC5A expression was dramatically repressed in OSCCs (P < 0.01). The immunohistochemical GPRC5A expression was moderately well differentiated, but greatly repressed in moderately differentiated OSCCs and completely repressed in poorly differentiated OSCCs. Overexpression of GPRC5A in OSCC CAL27 cells resulted in a suppressed anchorage-independent growth activity, a transforming phenotype.
CONCLUSIONS: GPRC5A is expressed in normal oral epithelium. Repression of GPRC5A is associated with poorly differential grade of OSCCs. Overexpression of GPRC5A in OSCC cell line reversed the malignant phenotype. Thus, GPRC5A is important for homeostasis in oral tissue, and deletion or repression of this gene may involve in tumorigenesis of OSCCs and may serve as a prognostic marker for malignant type of OSCCs.

Honda M, Yamashita T, Yamashita T, et al.
Peretinoin, an acyclic retinoid, improves the hepatic gene signature of chronic hepatitis C following curative therapy of hepatocellular carcinoma.
BMC Cancer. 2013; 13:191 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The acyclic retinoid, peretinoin, has been shown to be effective for suppressing hepatocellular carcinoma (HCC) recurrence after definitive treatment in a small-scale randomized clinical trial. However, little has been documented about the mechanism by which peretinoin exerts its inhibitory effects against recurrent HCC in humans in vivo.
METHODS: Twelve hepatitis C virus-positive patients whose HCC had been eradicated through curative resection or ablation underwent liver biopsy at baseline and week 8 of treatment with either a daily dose of 300 or 600 mg peretinoin. RNA isolated from biopsy samples was subjected to gene expression profile analysis.
RESULTS: Peretinoin treatment elevated the expression levels of IGFBP6, RBP1, PRB4, CEBPA, G0S2, TGM2, GPRC5A, CYP26B1, and many other retinoid target genes. Elevated expression was also observed for interferon-, Wnt-, and tumor suppressor-related genes. By contrast, decreased expression levels were found for mTOR- and tumor progression-related genes. Interestingly, gene expression profiles for week 8 of peretinoin treatment could be classified into two groups of recurrence and non-recurrence with a prediction accuracy rate of 79.6% (P<0.05). In the liver of patients with non-recurrence, expression of PDGFC and other angiogenesis genes, cancer stem cell marker genes, and genes related to tumor progression was down-regulated, while expression of genes related to hepatocyte differentiation, tumor suppression genes, and other genes related to apoptosis induction was up-regulated.
CONCLUSIONS: Gene expression profiling at week 8 of peretinoin treatment could successfully predict HCC recurrence within 2 years. This study is the first to show the effect of peretinoin in suppressing HCC recurrence in vivo based on gene expression profiles and provides a molecular basis for understanding the efficacy of peretinoin.

Subrungruanga I, Thawornkunob C, Chawalitchewinkoon-Petmitrc P, et al.
Gene expression profiling of intrahepatic cholangiocarcinoma.
Asian Pac J Cancer Prev. 2013; 14(1):557-63 [PubMed] Related Publications
Intrahepatic cholangiocarcinoma (ICC) is ranked as one of the top five causes of cancer-related deaths. ICC in Thai patients is associated with infection with the liver fluke, Opisthorchis viverrini, but the molecular basis for development remains unclear. The present study employed a microarray approach to compare gene expression profiles of ICCs and normal liver tissues from the same patients residing in Northeast Thailand, a region with a high prevalence of liver fluke infection. In ICC samples, 2,821 and 1,361 genes were found to be significantly up- and down-regulated respectively (unpaired t-test, p<0.05; fold-change>2.0). For validation of the microarray results, 7 up-regulated genes (FXYD3, GPRC5A, CEACAM5, MUC13, EPCAM, TMC5, and EHF) and 3 down- regulated genes (CPS1, TAT, and ITIH1) were selected for confirmation using quantitative RT-PCR, resulting in 100% agreement. The metallothionine heavy metal pathway contains the highest percentage of genes with statistically significant changes in expression. This study provides exon-level expression profiles in ICC that should be fruitful in identifying novel genetic markers for classifying and possibly early diagnosis of this highly fatal type of cholangiocarcinoma.

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