Global gene expression and functional network analysis of gastric cancer identify extended pathway maps and GPRC5A as a potential biomarker. Cancer Lett. 2012;326:105-113. [PMID: 22867946 DOI: 10.1016/j.canlet.2012.07.031]

GPRC5A promotes gallbladder cancer metastasis by upregulating TNS4 via the JAK2-STAT3 pathway

Aberrant expression of G protein-coupled receptor class C group 5 member A (GPRC5A) has been reported in multiple cancers and is closely related to patient prognosis. However, the mechanistic role of GPRC5A in gallbladder cancer (GBC) remains unclear. Here, we determined tumor expression levels of GPRC5A and the molecular mechanisms by which GPRC5A regulates gallbladder cancer metastasis. We found that GPRC5A was significantly upregulated in GBC, correlating with poorer patient survival. Knocking down GPRC5A inhibited GBC cell metastasis both in vitro and in vivo. GRPRC5A knockdown resulted in downregulation of TNS4 expression through the JAK2-STAT3 axis. Clinically, GPRC5A expression positively correlated with TNS4. Finally, STAT3 bound to TNS4's promoter region, inducing its expression. Overall, GPRC5A showed high expression in GBC tissues, associated with poor patient prognosis. Our findings first demonstrate that the GPRC5A-JAK2-STAT3-TNS4 pathway promotes GBC cell metastasis, suggesting potential therapy targets.

Mitochondria: a new intervention target for tumor invasion and metastasis

Mitochondria, responsible for cellular energy synthesis and signal transduction, intricately regulate diverse metabolic processes, mediating fundamental biological phenomena such as cell growth, aging, and apoptosis. Tumor invasion and metastasis, key characteristics of malignancies, significantly impact patient prognosis. Tumor cells frequently exhibit metabolic abnormalities in mitochondria, including alterations in metabolic dynamics and changes in the expression of relevant metabolic genes and associated signal transduction pathways. Recent investigations unveil further insights into mitochondrial metabolic abnormalities, revealing their active involvement in tumor cell proliferation, resistance to chemotherapy, and a crucial role in tumor cell invasion and metastasis. This paper comprehensively outlines the latest research advancements in mitochondrial structure and metabolic function. Emphasis is placed on summarizing the role of mitochondrial metabolic abnormalities in tumor invasion and metastasis, including alterations in the mitochondrial genome (mutations), activation of mitochondrial-to-nuclear signaling, and dynamics within the mitochondria, all intricately linked to the processes of tumor invasion and metastasis. In conclusion, the paper discusses unresolved scientific questions in this field, aiming to provide a theoretical foundation and novel perspectives for developing innovative strategies targeting tumor invasion and metastasis based on mitochondrial biology.

PLAU promotes cell proliferation and migration of head and neck cancer via STAT3 signaling pathway

It was reported that within the head and neck cancer (HNC) cell line CAL21 the epithelial-mesenchymal transition (EMT) and cell proliferation were promoted by Urokinase-Type Plasminogen Activator (PLAU) proteinase through TNFRSF12A. Additionally, in this paper HNC cell lines refer to Fadu and Tu686. A novel PLAU-STAT3 axis was found to be involved in HNC cell line proliferation and metastasis. PLAU expression in HNC samples was upregulated, besides, the elevated expression of PLAU was linked to the lower overall survival (OS) and disease-free survival (DFS). Ectopic PLAU expression promoted cell proliferation and migration, while PLAU knockdown exhibited opposite results. RNA-seq data identified the JAK-STAT signaling pathway, confirmed by western blotting. A recovery assay using S3I-201, a selective inhibitor of signal transducer and activator of transcription 3 (STAT3), indicated that PLAU promoted HNC cell line progression via STAT3 signaling in vitro. The oncogenic role of PLAU in HNC tumor growth in vivo was confirmed using xenograft models. In summary, we identified the tumorigenic PLAU function in the HNC progress. PLAU may represent a potential prognostic biomarker of HNC and the PLAU-STAT3 pathway might be considered a therapeutic target of HNC.

Mitochondrial respiratory chain component NDUFA4: a promising therapeutic target for gastrointestinal cancer

Gastrointestinal cancer, one of the most common cancers, continues to be a major cause of mortality and morbidity globally. Accumulating evidence has shown that alterations in mitochondrial energy metabolism are involved in developing various clinical diseases. NADH dehydrogenase 1 alpha subcomplex 4 (NDUFA4), encoded by the NDUFA4 gene located on human chromosome 7p21.3, is a component of mitochondrial respiratory chain complex IV and integral to mitochondrial energy metabolism. Recent researchers have disclosed that NDUFA4 is implicated in the pathogenesis of various diseases, including gastrointestinal cancer. Aberrant expression of NDUFA4 leads to the alteration in mitochondrial energy metabolism, thereby regulating the growth and metastasis of cancer cells, indicating that it might be a new promising target for cancer intervention. This article comprehensively reviews the structure, regulatory mechanism, and biological function of NDUFA4. Of note, the expression and roles of NDUFA4 in gastrointestinal cancer including colorectal cancer, liver cancer, gastric cancer, and so on were discussed. Finally, the existing problems of NDUFA4-based intervention on gastrointestinal cancer are discussed to provide help to strengthen the understanding of the carcinogenesis of gastrointestinal cancer, as well as the development of new strategies for clinical intervention.

Methylation of GPRC5A promotes liver metastasis and docetaxel resistance through activating mTOR signaling pathway in triple negative breast cancer

AIMS

This study aims to explore the function and mechanism of G Protein-coupled receptor class C group 5 member A (GPRC5A) in docetaxel-resistance and liver metastasis of breast cancer.

METHODS

Single-cell RNA transcriptomic analysis and bioinformatic analysis are used to screen relevant genes in breast cancer metastatic hepatic specimens. MeRIP, dual-luciferase analysis and bioinformation were used to detect m6A modulation. Mass spectrometry (MS), co-inmunoprecipitation (co-IP) and immunofluorescence colocalization were executed to explore the mechanism of GPRC5A in breast cancer cells.

RESULT

GPRC5A was upregulated in triple-negative breast cancer (TNBC) and was associated with a poor prognosis. In vitro and in vivo experiments demonstrated that knockdown of GPRC5A alleviated metastasis and resistance to docetaxel in TNBC. Overexpression of GPRC5A had the opposite effects. The m6A methylation of GPRC5A mRNA was modulated by METTL3 and YTHDF1, which facilitates its translation. GPRC5A inhibited the ubiquitination-dependent degradation of LAMTOR1, resulting in the recruitment of mTORC1 to lysosomes and activating the mTORC1/p70s6k signaling pathway.

CONCLUSION

METTL3/YTHDF1 axis up-regulates GPRC5A expression by m6A methylation. GPRC5A activates mTORC1/p70s6k signaling pathway by recruiting mTORC1 to lysosomes, consequently promotes docetaxel-resistance and liver metastasis.

The G protein-coupled receptor GPRC5A-a phorbol ester and retinoic acid-induced orphan receptor with roles in cancer, inflammation, and immunity

GPRC5A is the first member of a new class of orphan receptors coupled to G proteins, which also includes GPRC5B, GPRC5C, and GPRC5D. Since its cloning and identification in the 1990s, substantial progress has been made in understanding the possible functions of this receptor. GPRC5A has been implicated in a variety of cellular events, such as cytoskeleton reorganization, cell proliferation, cell cycle regulation, migration, and survival. It appears to be a central player in different pathological processes, including tumorigenesis, inflammation, immune response, and tissue damage. The levels of GPRC5A expression differ depending on the type of cancer, with increased expression in colon, pancreas, and prostate cancers; decreased expression in lung cancer; and varied results in breast cancer. In this review, we discuss the early discovery of GPRC5A as a phorbol ester-induced gene and later as a retinoic acid-induced gene, its regulation, and its participation in important canonical pathways related to numerous types of tumors and inflammatory processes. GPRC5A represents a potential new target for cancer, inflammation, and immunity therapies.

Bufalin targeting BFAR inhibits the occurrence and metastasis of gastric cancer through PI3K/AKT/mTOR signal pathway

Gastric cancer (GC) is the most common malignant tumor of digestive system. Bufalin extracted from Venenum Bufonis is one of the most effective anticancer monomers, which has been proved to play anticancer roles in a variety of cancers such as ovarian cancer, prostate cancer and neuroblastoma. However, there are few studies on bufalin in GC, and lack of clear targets. The effect of bufalin on the proliferation and migration of GC cells was detected by CCK-8, scratch wound healing assay, transwell assay and Western blotting. The potential direct interaction proteins of bufalin were screened by human proteome microarray containing 21,838 human proteins. The target protein was determined by bioinformatics, and the binding sites were predicted by molecular docking technique. Biological experiments in vitro and in vivo were conducted to verify the effect of bufalin directly interaction protein and the mechanism of bufalin targeting the protein to inhibit the development of GC. The results showed that bufalin inhibited the proliferation and migration of MKN-45 and HGC-27 GC cell lines in vitro. BFAR, a direct interaction protein of bufalin has several potential binding sites to bufalin. BFAR is highly expressed in GC and promotes the occurrence and metastasis of GC by activating PI3K/AKT/mTOR signal pathway in vitro and in vivo. Bufalin reversed the promoting effect of BFAR on the carcinogenesis and metastasis of GC by down-regulating the expression of BFAR. Our results show that bufalin targeting BFAR inhibits the occurrence and metastasis of GC through PI3K/AKT/mTOR signal pathway. These results provide a new basis for bufalin as a promising drug for the treatment of GC.

RAI3 expression is not associated with clinical outcomes of patients with non-small cell lung cancer

PURPOSE

Retinoic acid inducible protein 3 (RAI3) has been suggested as prognostic biomarker in several cancer types. The present study aimed to examine the role of RAI3 expression in non-small cell lung cancers (NSCLCs).

METHODS

RAI3 protein expression was evaluated by immunohistochemistry in tissue microarray (TMA) sections from a retrospective cohort of more than 600 surgically resected NSCLCs and results were compared with clinicopathological features and follow-up data.

RESULTS

While membranous RAI3 immunostaining was always strong in benign lung, strong RAI3 staining was only detectable in 14.7% of 530 interpretable NSCLCs. Within NSCLC subtypes, immunostaining intensity for RAI3 was significantly decreased in large cell lung cancers (LCLCs) and squamous cell carcinomas (SQCCs) relative to lung adenocarcinomas (LUACs) (P < 0.0001 each). However, RAI3 staining was neither associated with pathological features of NSCLCs nor with survival of patients (P = 0.6915).

CONCLUSION

Our study shows that RAI3 expression was not associated with clinical outcomes of NSCLC patients and cannot be considered as prognostic marker in lung cancer patients.

Identification of key biomarkers for STAD using filter feature selection approaches

Gastric cancer (GC) is the fifth most common cancer and the third leading cause of cancer death worldwide. Discovery of diagnostic biomarkers prompts the early detection of GC. In this study, we used limma method combined with joint mutual information (JMI), a machine learning algorithm, to identify a signature of 11 genes that performed well in distinguishing tumor and normal samples in a stomach adenocarcinoma cohort. Other two GC datasets were used to validate the classifying performances. Several of the candidate genes were correlated with GC tumor progression and survival. Overall, we highlight the application of feature selection approaches in the analysis of high-dimensional biological data, which will improve study accuracies and reduce workloads for the researchers when identifying potential tumor biomarkers.

m6A RNA methylation-mediated NDUFA4 promotes cell proliferation and metabolism in gastric cancer

Gastric cancer (GC) is a malignancy with poor prognosis. NDUFA4 is reported to correlate with the progression of GC. However, its underlying mechanism in GC is unknown. Our study was to reveal the pathogenic mechanism of NDUFA4 in GC. NDUFA4 expression was explored in single-cell and bulk RNA-seq data as well as GC tissue microarray. Mitochondrial respiration and glycolysis were estimated by oxygen consumption rate and extracellular acidification rate, respectively. The interaction between NDUFA4 and METTL3 was validated by RNA immunoprecipitation. Flow cytometry was used to estimate cell cycle, apoptosis and mitochondrial activities. NDUFA4 was highly expressed in GC and its high expression indicated a poor prognosis. The knockdown of NDUFA4 could reduce cell proliferation and inhibit tumor growth. Meanwhile, NDUFA4 could promote glycolytic and oxidative metabolism in GC cells, whereas the inhibition of glycolysis suppressed the proliferation and tumor growth of GC. Besides, NDUFA4 inhibited ROS level and promoted MMP level in GC cells, whereas the inhibition of mitochondrial fission could reverse NDUFA4-induced glycolytic and oxidative metabolism and tumor growth of GC. Additionally, METTL3 could increase the m6A level of NDUFA4 mRNA via the m6A reader IGF2BP1 to promote NDUFA4 expression in GC cells. Our study revealed that NDUFA4 was increased by m6A methylation and could promote GC development via enhancing cell glycolysis and mitochondrial fission. NDUFA4 was a potential target for GC treatment.

Cerebrospinal fluid of progressive multiple sclerosis patients reduces differentiation and immune functions of oligodendrocyte progenitor cells

Oligodendrocyte progenitor cells (OPCs) are responsible for remyelination in the central nervous system (CNS) in health and disease. For patients with multiple sclerosis (MS), remyelination is not always successful, and the mechanisms differentiating successful from failed remyelination are not well-known. Growing evidence suggests an immune role for OPCs, in addition to their regenerative role; however, it is not clear if this helps or hinders the regenerative process. We studied the effect of cerebrospinal fluid (CSF) from relapsing MS (rMS) and progressive MS (pMS) patients on primary OPC differentiation and immune gene expression and function. We observed that CSF from either rMS or pMS patients has a differential effect on the ability of mice OPCs to differentiate into mature oligodendrocytes and to express immune functions. CSF of pMS patients impaired differentiation into mature oligodendrocytes. In addition, it led to decreased major histocompatibility complex class (MHC)-II expression, tumor necrosis factor (TNF)-α secretion, nuclear factor kappa-B (NFκB) activation, and less activation and proliferation of T cells. Our findings suggest that OPCs are not only responsible for remyelination, but they may also play an active role as innate immune cells in the CNS.

Prognostic and clinicopathological significance of GPRC5A in various cancers: A systematic review and meta-analysis

Background

GPRC5A is associated with various cancer initiation and progression. Controversial findings have been reported about GPRC5A prognostic characteristics, and no meta-analysis has been conducted to assess the relationship between GPRC5A and cancer prognosis. Therefore, the objective of this meta-analysis is to evaluate the overall prognostic effectiveness of GPRC5A.

Methods

We first conducted a systematic search in the PubMed, Embase, Web of Science, CNKI, Cochrane, and WangFang databases. The hazard ratio (HR) and odds ratios (OR) with 95% CI were then pooled to assess the associations between GPRC5A expression and overall survival (OS), disease-free survival (DFS), event-free survival (EFS), and clinicopathological characteristics. Chi-squared test and I² statistics were completed to evaluate the heterogeneity in our study. A random‐effects model was used when significant heterogeneity existed (I²>50% and p<0.05); otherwise, we chose the fixed-effect model. Subgroup analysis was stratified by tumor type, region, HR obtained measurements, and sample capacity to explore the source of heterogeneity.

Results

In total, 15 studies with 624 patients met inclusion criteria of this study. Our results showed that higher expression of GPRC5A is associated with worse OS (HR:1.69 95%CI: 1.20–2.38 I² = 75.6% p = 0.000), as well as worse EFS (HR:1.45 95%CI: 1.02–1.95 I² = 0.0% p = 0.354). Subgroup analysis indicated that tumor type might be the source of high heterogeneity. Additionally, cancer patients with enhanced GPRC5A expression were more likely to lymph node metastasis (OR:1.95, 95%CI 1.33–2.86, I² = 43.9%, p = 0.129) and advanced tumor stage (OR: 1.83, 95%CI 1.15–2.92, I² = 61.3%, p = 0.035), but not associated with age, sex, differentiation, and distant metastasis.

Conclusion

GPRC5A can be a promising candidate for predicting medical outcomes and used for accurate diagnosis, prognosis prediction for patients with cancer; however, the predictive value of GPRC5A varies significantly according to cancer type. Further studies for this mechanism will be necessary to reveal novel insights into application of GPRC5A in cancers.

Circ_0000144 functions as a miR-623 sponge to enhance gastric cancer progression via up-regulating GPRC5A

BACKGROUND

Gastric cancer (GC) remains one of the most common malignancies worldwide. Increasing evidence has demonstrated that circRNAs serve as critical roles in human cancer, including GC. In the present study, we focused on the detailed function and mechanism of circ_0000144 on GC progression.

METHODS

The levels of circ_0000144, miR-623 and G-protein-coupled receptor, family C, group 5, member A (GPRC5A) were determined by quantitative real-time polymerase chain reaction (qRT-PCR). Targeted relationships among circ_0000144, miR-623 and GPRC5A were confirmed using dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Cell proliferation, colony formation, apoptosis, migration and invasion were evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), colony formation, flow cytometry and transwell assays. Measurement of glutamine and α-ketoglutarate (α-KG) levels was performed using a corresponding assay kit. GPRC5A protein expression was detected using Western blot. In vivo assays were used to explore the impact of circ_0000144 on tumor growth.

RESULTS

Our data indicated that circ_0000144 was up-regulated and miR-623 was down-regulated in GC tissues and cells. Circ_0000144 interacted with miR-623 through directly binding to miR-623. Moreover, the knockdown of circ_0000144 weakened GC cell proliferation, colony formation, migration, invasion and glutaminolysis and accelerated cell apoptosis by up-regulating miR-623. GPRC5A was a direct target of miR-623 and circ_0000144 protected against GPRC5A repression through sponging miR-623. Furthermore, miR-623-mediated regulation on GC cell progression was reversed by the stored expression of GPRC5A. Additionally, circ_0000144 depletion inhibited tumor growth in vivo.

CONCLUSION

Our study indicated that circ-0000144 knockdown repressed GC progression at least partly by regulating GPRC5A expression via sponging miR-623, illumining a novel therapeutic target for GC treatment.

GPRC5a suppresses the proliferation of non-small cell lung cancer under wild type p53 background

Introduction: GPRC5a plays an important role in many types of cancers with intriguing dual functions. GPRC5a acts as oncogene or tumor suppressor in different types of cancer. It is interesting to illustrate why GPRC5a functions differently.Methods: Data mining method were used to analyze the potential prognostic value of GPRC5a expression for Non-Small Cell Lung Cancer (NSCLC) lung cancer patients. Then we used cell models to further investigate the effect of p53 mutation on GPRC5a expression and the thereafter cell biological behaviors.Results: Our results present here showed High mRNA-level expression of GPRC5a was associated with worse overall survival about lung cancer patients; mutation of p53 gene could result in up regulation of GPRC5a expression and promotion of cell proliferation in lung cancer cells. Our results not only demonstrate the role of GPRC5a as a tumor suppressor in lung cancer, but also revealed the tumor suppressive factor p53 regulated tightly on GPRC5a and cell growth of NSCLC cancer.Conclusions: Our results demonstrated that p53 upregulated GPRC5a expression in NSCLC cells, and the loss of p53 expression in NSCLC may be one of the mechanisms leading to the decreased GPRC5a expression in NSCLC.

Integrated Analysis of DNA Copy Number Changes and Gene Expression Identifies Key Genes in Gastric Cancer

This study was aimed at identifying differentially expressed genes (DEGs) with copy number changes in gastric cancer (GC) pathogenesis. Microarray data GSE33429, including array-based comparative genomic hybridization and gene expression profiles, were obtained. DEGs were screened between GC and adjacent noncancerous tissues. Genes located at Minimum Common Regions (MCRs) were identified, and overlapped genes between DEGs and genes with amplification or deletion were identified. Gene Ontology function and pathway enrichment analysis of DEGs were performed. A protein-protein interaction network for DEGs was built, and significant modules were mined from the network. Functional annotation of genes in modules was also performed. A total of 677 up- and 583 downregulated DEGs were identified, including 37 overexpressed genes located at gained MCRs and 28 downregulated genes located at deleted MCRs. In significant modules, upregulated genes with amplification, including DSN1 (MIS12 kinetochore complex component), MAPRE1 (microtubule-associated protein, RP/EB family, member 1), TPX2 (microtubule-associated), UBE2C (ubiquitin-conjugating enzyme E2C), and MYBL2 (v-myb avian myeloblastosis viral oncogene homolog-like 2), were associated with cell cycle, but downregulated genes with deletion, including UGT2B15 (UDP glucuronosyltransferase 2 family, polypeptide B15), UGT2B17 (UDP glucuronosyltransferase 2 family, polypeptide B17), ADH1B (alcohol dehydrogenase 1B), and ADH1A (alcohol dehydrogenase 1A), were related to metabolism. The identified genes DSN1, MAPRE1, TPX2, UBE2C, and MYBL2 located at gained MCRs and UGT2B15, UGT2B17, ADH1B, and ADH1A located at deleted MCRs may play an important role in GC progression through regulating cell cycle and metabolism.

Five-long non-coding RNA risk score system for the effective prediction of gastric cancer patient survival

The prognosis for patients with gastric cancer (GC) is usually poor, as the majority of patients have reached the advanced stages of disease at the point of diagnosis. Therefore, revealing the mechanisms of GC is necessary for the identification of key biomarkers and the development of effective targeted therapies. The present study aimed to identify long non-coding RNAs (lncRNAs) prominently expressed in patients with GC. The GC dataset (including 384 GC samples) was downloaded from The Cancer Genome Atlas database as the training set. A number of other GC datasets were obtained from the Gene Expression Omnibus database as validation sets. Following data processing, lncRNAs were annotated, followed by co-expression module analysis to identify stable modules, using the weighted gene co-expression network analysis (WGCNA) package. Prognosis-associated lncRNAs were screened using the ‘survival’ package. Following the selection of the optimal lncRNA combinations using the ‘penalized’ package, risk score systems were constructed and assessed. Consensus differentially-expressed RNAs (DE-RNAs) were screened using the MetaDE package, and an lncRNA-mRNA network was constructed. Additionally, pathway enrichment analysis was conducted for the network nodes using gene set enrichment analysis (GSEA). A total of seven modules (blue, brown, green, grey, red, turquoise and yellow) were obtained following WGCNA analysis, among which the green and turquoise modules were stable and associated with the histological grade of GC. A total of 12 prognosis-associated lncRNAs were identified in the two modules. Combined with the optimal lncRNA combinations, risk score systems were constructed. The risk score system based on the green module [including ITPK1 antisense RNA 1 (ITPK1-AS1), KCNQ1 downstream neighbor (KCNQ1DN), long intergenic non-protein coding RNA 167 (LINC00167), LINC00173 and LINC00307] was the more efficient at predicting risk compared with those based on the turquoise, or the green + turquoise modules. A total of 1,105 consensus DE-RNAs were identified; GSEA revealed that LINC00167, LINC00173 and LINC00307 had the same association directions with 4 pathways and the 32 genes involved in those pathways. In conclusion, a risk score system based on the green module may be applied to predict the survival of patients with GC. Furthermore, ITPK1-AS1, KCNQ1DN, LINC00167, LINC00173 and LINC00307 may serve as biomarkers for GC pathogenesis.

High levels of RAI3 expression is linked to shortened survival in esophageal cancer patients

Expression of the retinoic acid-induced protein 3 (RAI3) has been suggested to predict clinical outcome in a variety of malignancies. However, its role in esophageal cancers remains unclear. Immunohistochemical RAI3 staining was analyzed on tissue microarrays containing 359 esophageal adenocarcinomas (EAC) and 254 esophageal squamous cell carcinomas (ESCC). RAI3 immunostaining was typically absent or weakly detectable in the membranes in benign esophageal tissues. RAI3 staining was higher in malignant than in benign esophagus epithelium. High-levels of RAI3 staining were found in 79.2% of interpretable EACs and 55.9% of ESCCs. In EACs, strong RAI3 staining was associated with advanced pathological tumor stage (p < .0001), high UICC stage (p < .0001), high tumor grade (p = .0133), and positive lymph nodal status (p = .0002). Additionally, high RAI3 staining predicted shortened overall survival of EAC and ESCC patients (p = .0298 and p = .0227). RAI3 overexpression is associated with poor prognosis in esophageal cancers. We propose that RAI3 overexpression might play a biologically relevant role of RAI3 in esophageal cancers.

GPRC5A: An Emerging Biomarker in Human Cancer

Aberrant expression of G protein-coupled receptors (GPCRs) is frequently associated with tumorigenesis. G Protein-coupled receptor class C group 5 member A (GPRC5A) is a member of the GPCR superfamily, is expressed preferentially in lung tissues, and is regulated by various entities at multiple levels. GPRC5A exerts a tumor suppressive role in lung cancer and GPRC5A deletion promotes lung tumor initiation and progression. Recent advances have highlighted that GPRC5A dysregulation is found in various human cancers and is related to many tumor-associated signaling pathways, including the cyclic adenosine monophosphate (cAMP), nuclear factor (NF)-κB, signal transducer and activator of transcription (STAT) 3, and focal adhesion kinase (FAK)/Src signaling. This review aimed to summarize our updated view on the biology and regulation of GPRC5A, its expression in human cancers, and the linked signaling pathways. A better comprehension of the underlying cellular and molecular mechanisms of GPRC5A will provide novel insights into its potential diagnostic and therapeutic value.

Clinical significance of reduced GPRC5A expression in surgically resected non-small cell lung cancer

G protein-coupled receptor, family C, group 5 member A (GPRC5A) is a retinoid-inducible protein, which has been characterized as a tumor-suppressor gene in lung cancer. The present study further examined GPRC5A expression in non-small cell lung cancer (NSCLC) for any association with the clinical features and treatment outcomes of patients with NSCLC. A total of 30 paired NSCLC tumor and adjacent normal tissues were analyzed for the detection of GPRC5A mRNA and protein using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis, respectively. Immunohistochemistry was performed to determine the GPRC5A expression levels in 110 NSCLC and 60 para-tumor tissues. The results confirmed significantly lower expression levels of GPRC5A in NSCLC tumors compared with the corresponding noncancerous tissues (P<0.001). Lost GPRC5A expression was significantly associated with the tumor histological type (P=0.008), poor tumor differentiation (P<0.001) and tumor-node-metastasis (TNM) stage (P<0.001). Kaplan-Meier curve analysis revealed that patients with NSCLC with low GPRC5A expression tumors had a worse prognosis compared with those with high GPRC5A expression tumors (P=0.010). The results of multivariate Cox analysis further suggested that low GPRC5A expression was an independent prognostic factor for patients with NSCLC (P<0.001). The results of this study suggest GPRC5A expression has clinical potential as a prognostic biomarker for patients with NSCLC.

Identification of Potential Key Genes Associated With the Pathogenesis and Prognosis of Gastric Cancer Based on Integrated Bioinformatics Analysis

Background and Objective: Despite striking advances in multimodality management, gastric cancer (GC) remains the third cause of cancer mortality globally and identifying novel diagnostic and prognostic biomarkers is urgently demanded. The study aimed to identify potential key genes associated with the pathogenesis and prognosis of GC.

Methods: Differentially expressed genes between GC and normal gastric tissue samples were screened by an integrated analysis of multiple gene expression profile datasets. Key genes related to the pathogenesis and prognosis of GC were identified by employing protein–protein interaction network and Cox proportional hazards model analyses.

Results: We identified nine hub genes (TOP2A, COL1A1, COL1A2, NDC80, COL3A1, CDKN3, CEP55, TPX2, and TIMP1) which might be tightly correlated with the pathogenesis of GC. A prognostic gene signature consisted of CST2, AADAC, SERPINE1, COL8A1, SMPD3, ASPN, ITGBL1, MAP7D2, and PLEKHS1 was constructed with a good performance in predicting overall survivals.

Conclusion: The findings of this study would provide some directive significance for further investigating the diagnostic and prognostic biomarkers to facilitate the molecular targeting therapy of GC.

Multi-omics analysis identifies pathways and genes involved in diffuse-type gastric carcinogenesis induced by E-cadherin, p53, and Smad4 loss in mice

The molecular mechanisms underlying the pathogenesis of diffuse-type gastric cancer (DGC) have not been adequately explored due to a scarcity of appropriate animal models. A recently developed tool well suited for this line of investigation is the Pdx-1-Cre;Cdh1^F/+ ;Trp53^F/F ;Smad4^F/F (pC^he PS) mouse model that spontaneously develops metastatic DGC showing nearly complete E-cadherin loss. Here, we performed a proteogenomic analysis to uncover the molecular changes induced by the concurrent targeting of E-cadherin, p53, and Smad4 loss. The gene expression profiles of mouse DGCs and in vivo gastric phenotypes from various combinations of gene knockout demonstrated that these mutations collaborate to activate cancer-associated pathways to generate aggressive DGC. Of note, WNT-mediated epithelial-to-mesenchymal transition (EMT) and extracellular matrix (ECM)-cytokine receptor interactions were prominently featured. In particular, the WNT target gene osteopontin (OPN) that functions as an ECM cytokine is highly upregulated. In validation experiments, OPN contributed to DGC stemness by promoting cancer stem cell (CSC) survival and chemoresistance. It was further found that Bcl-xL acts as a targetable downstream effector of OPN in DGC CSC survival. In addition, Zeb2 and thymosin-β4 (Tβ4) were identified as prime candidates as suppressors of E-cadherin expression from the remaining Cdh1 allele during DGC development. Specifically, Tβ4 suppressed E-cadherin expression and anoikis while promoting cancer cell growth and migration. Collectively, these proteogenomic analyses broaden and deepen our understanding of the contribution of key driver mutations in the stepwise carcinogenesis of DGC through novel effectors, namely OPN and Tβ4.

Integrated MicroRNA-mRNA Analysis Reveals miR-204 Inhibits Cell Proliferation in Gastric Cancer by Targeting CKS1B, CXCL1 and GPRC5A

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 CKS1B, CXCL1, and GPRC5A are putative targets of miR-204 and elucidated that miR-204 acted as potential tumor suppressor and, therefore, are useful as a promising therapeutic target for gastric cancer.

RAI3 knockdown promotes adipogenic differentiation of human adipose-derived stem cells by decreasing β-catenin levels

Retinoic acid-induced protein 3 (RAI3) has been found to play significant roles in embryonic development, cellular proliferation and differentiation, but its role in adipogenesis has not been explored. In this study, we discovered RAI3 was downregulated during the adipogenic differentiation of human adipose derived stem cells (hASCs). Moreover, we demonstrated that knockdown of RAI3 promoted adipogenic differentiation of hASCs both in vitro and in vivo. Mechanistically, our findings showed that inhibition of RAI3 in hASCs reduced the expression of β-catenin, and lithium chloride which can activate the β-catenin pathway abolished the effect of RAI3 knockdown on the adipogenesis. These results suggest RAI3 plays an important role in adipogenesis of hASCs and may have a potential use in the future application.

Elevation of GPRC5A expression in colorectal cancer promotes tumor progression through VNN-1 induced oxidative stress

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.

The G Protein-Coupled Receptor RAI3 Is an Independent Prognostic Factor for Pancreatic Cancer Survival and Regulates Proliferation via STAT3 Phosphorylation

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.

Identifying key stage-specific genes and transcription factors for gastric cancer based on RNA-sequencing data

BACKGROUND

To identify gastric cancer (GC)-associated genes and transcription factors (TFs) using RNA-sequencing (RNA-seq) data of Asians.

MATERIALS AND METHODS

The RNA-seq data (GSE36968) were downloaded from Gene Expression Omnibus database, including 6 noncancerous gastric tissue samples, 5 stage I GC samples, 5 stage II GC samples, 8 stage III GC samples, and 6 stage IV GC samples. The gene expression values in each sample were calculated using Cuffdiff. Following, stage-specific genes were identified by 1-way analysis of variance and hierarchical clustering analysis. Upstream TFs were identified using Seqpos. Besides, functional enrichment analysis of stage-specific genes was performed by DAVID. In addition, the underlying protein-protein interactions (PPIs) information among stage IV-specific genes were extracted from STRING database and PPI network was constructed using Cytoscape software.

RESULTS

A total of 3576 stage-specific genes were identified, including 813 specifically up-regulated genes in the normal gastric tissues, 2224 stage I and II-specific genes, and 539 stage IV-specific genes. Also, a total of 9 and 11 up-regulated TFs were identified for the stage I and II-specific genes and stage IV-specific genes, respectively. Functional enrichment showed SPARC, MMP17, and COL6A3 were related to extracellular matrix. Notably, 2 regulatory pathways HOXA4-GLI3-RUNX2-FGF2 and HMGA2-PRKCA were obtained from the PPI network for stage IV-specific genes. In the PPI network, TFs HOXA4 and HMGA2 might function via mediating other genes.

CONCLUSION

These stage-specific genes and TFs might act in the pathogenesis of GC in Asians.

Biphasic Ccl20 regulation by Toll-like receptor 9 through the activation of ERK-AP-1 and non-canonical NF-κB signaling pathways

BACKGROUND

Chemokines play key roles in immune homeostasis and inflammatory response. Considering the role of Ccl20 and Toll-like receptor 9 (TLR9) in gut homeostasis and inflammatory bowel disease (IBD), regulation of Ccl20 by bacterial DNA, the TLR9 ligand, merits in-depth studies.

METHODS

We analyzed Ccl20 expression in various epithelial cell (EC) lines by q-PCR and ELISA. In-vivo expression was investigated in isolated murine colonocytes by immunoblotting. Transcriptional regulation of Ccl20 was studied by reporter assays, gene knock-down, electrophoretic mobility shift assay and chromatin immunoprecipitation. Activation of upstream kinases was checked by immunoblotting.

RESULTS

We showed low levels of Ccl20 expression in mouse colonic ECs, but marked induction by in vivo treatment with bacterial DNA. This corroborated with persistent Ccl20 induction in different EC lines. We found involvement of MAP-kinases during the early hours after stimulation, and a novel AP-1site (-252bp) regulated the expression in colonic ECs. More importantly, mutually exclusive transcriptional regulation by AP-1 (cjun/cfos) and non-canonical NF-κB (RelB/p52) downstream of MEK-ERK and NIK-IKK-α-NF-κB2 (p100) phosphorylation, respectively was responsible for persistent Ccl20 expression in the colonic cells, while canonical NF-κB isoforms played no role.

CONCLUSIONS

Persistent Ccl20 induction by TLR9 in colonic ECs involves early and delayed activation of two independent signaling pathways. This is the first report of non-canonical NF-κB activation and Ccl20 expression in the colonic ECs by TLR9.

GENERAL SIGNIFICANCE

Our study will help to better understand immune regulation by Ccl20 in the intestine and may be exploited for future development of novel therapeutics against IBD.

GPRC5A is a potential oncogene in pancreatic ductal adenocarcinoma cells that is upregulated by gemcitabine with help from HuR

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.

Integrated miRNA-risk gene-pathway pair network analysis provides prognostic biomarkers for gastric cancer

Purpose

This study aimed to identify molecular prognostic biomarkers for gastric cancer.

Methods

mRNA and miRNA expression profiles of eligible gastric cancer and control samples were downloaded from Gene Expression Omnibus to screen the differentially expressed genes (DEGs) and differentially expressed miRNAs (DEmiRs), using MetaDE and limma packages, respectively. Target genes of the DEmiRs were also collected from both predictive and experimentally validated target databases of miRNAs. The overlapping genes between selected targets and DEGs were identified as risk genes, followed by functional enrichment analysis. Human pathways and their corresponding genes were downloaded from the Kyoto Encyclopedia of Genes and Genomes (KEGG) database for the expression analysis of each pathway in gastric cancer samples. Next, co-pathway pairs were selected according to the Pearson correlation coefficients. Finally, the co-pathway pairs, miRNA–target pairs, and risk gene–pathway pairs were merged into a complex interaction network, the most important nodes (miRNAs/target genes/co-pathway pairs) of which were selected by calculating their degrees.

Results

Totally, 1,260 DEGs and 144 DEmiRs were identified. There were 336 risk genes found in the 9,572 miRNA–target pairs. Judging from the pathway expression files, 45 co-pathway pairs were screened out. There were 1,389 interactive pairs and 480 nodes in the integrated network. Among all nodes in the network, focal adhesion/extracellular matrix–receptor interaction pathways, CALM2, miR-19b, and miR-181b were the hub nodes with higher degrees.

Conclusion

CALM2, hsa-miR-19b, and hsa-miR-181b might be used as potential prognostic targets for gastric cancer.

ccmGDB: a database for cancer cell metabolism genes

Accumulating evidence has demonstrated that rewiring of metabolism in cells is an important hallmark of cancer. The percentage of patients killed by metabolic disorder has been estimated to be 30% of the advanced-stage cancer patients. Thus, a systematic annotation of cancer cell metabolism genes is imperative. Here, we present ccmGDB (Cancer Cell Metabolism Gene DataBase), a comprehensive annotation database for cell metabolism genes in cancer, available at http://bioinfo.mc.vanderbilt.edu/ccmGDB. We assembled, curated, and integrated genetic, genomic, transcriptomic, proteomic, biological network and functional information for over 2000 cell metabolism genes in more than 30 cancer types. In total, we integrated over 260 000 somatic alterations including non-synonymous mutations, copy number variants and structural variants. We also integrated RNA-Seq data in various primary tumors, gene expression microarray data in over 1000 cancer cell lines and protein expression data. Furthermore, we constructed cancer or tissue type-specific, gene co-expression based protein interaction networks and drug-target interaction networks. Using these systematic annotations, the ccmGDB portal site provides 6 categories: gene summary, phenotypic information, somatic mutations, gene and protein expression, gene co-expression network and drug pharmacological information with a user-friendly interface for browsing and searching. ccmGDB is developed and maintained as a useful resource for the cancer research community.

Copy Number Gains at 8q24 and 20q11-q13 in Gastric Cancer Are More Common in Intestinal-Type than Diffuse-Type

The present study was aimed at discovering DNA copy number alterations (CNAs) involved in the carcinogenesis of stomach and at understanding their clinicopathological significances in the Korean population. DNA copy numbers were analyzed using Agilent 244K or 400K array comparative genomic hybridization (aCGH) in fresh-frozen tumor and matched normal tissues from 40 gastric cancer patients. Some of the detected CNA regions were validated using multiplex ligation-dependent probe amplification (MLPA) in six of the 40 patients and customized Agilent 60K aCGH in an independent set of 48 gastric cancers. The mRNA levels of genes at common CNA regions were analyzed using quantitative real-time PCR. Copy number gains were more common than losses across the entire genome in tumor tissues compared to matched normal tissues. The mean number of alterations per case was 64 for gains and 40 for losses, and the median aberration length was 44016 bp for gains and 4732 bp for losses. Copy number gains were frequently detected at 7p22.1 (20%), 8q24.21 (27%-30%), 8q24.3 (22%-48%), 13q34 (20%-31%), and 20q11-q13 (25%-30%), and losses at 3p14.2 (43%), 4q35.2 (27%), 6q26 (23%), and 17p13.3 (20%-23%). CNAs at 7p22.1, 13q34, and 17p13.3 have not been reported in other populations. Most of the copy number losses were associated with down-regulation of mRNA levels, but the correlation between copy number gains and mRNA expression levels varied in a gene-dependent manner. In addition, copy number gains tended to occur more commonly in intestinal-type cancers than in diffuse-type cancers. In conclusion, the present study suggests that copy number gains at 8q24 and 20q11-q13 and losses at 3p14.2 may be common events in gastric cancer but CNAs at 7p22.1, 13q34, and 17p13.3 may be Korean-specific.

GPRC5A overexpression predicted advanced biological behaviors and poor prognosis in patients with gastric cancer

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.

The emerging roles of GPRC5A in diseases

The ‘Retinoic Acid-Inducible G-protein-coupled receptors’ or RAIG are a group comprising the four orphan receptors GPRC5A, GPRC5B, GPRC5C and GPRC5D. As the name implies, their expression is induced by retinoic acid but beyond that very little is known about their function. In recent years, one member, GPRC5A, has been receiving increasing attention as it was shown to play important roles in human cancers. As a matter of fact, dysregulation of GPRC5A has been associated with several cancers including lung cancer, breast cancer, colorectal cancer, and pancreatic cancer. Here we review the current state of knowledge about the heterogeneity and evolution of GPRC5A, its regulation, its molecular functions, and its involvement in human disease.

Clinicopathological significance of GPRC5A and STAT3 expression in esophageal squamous cell carcinoma

AIM: To investigate the expression of G protein-coupled receptor family C, member 5, group A (GPRC5A) and signal transducer and activator of transcription 3 (STAT3) proteins in esophageal squamous cell carcinoma (ESCC) and to analyze their clinicopathological significance.

METHODS: Immunohistochemistry was used to detect the expression of GPRC5A and STAT3 proteins in ESCC, matched tumor-adjacent tissue and normal esophageal tissue. The correlation between the expression of these proteins and clinicopathologic features of ESCC was analyzed.

RESULTS: The rate of GPRC5A protein expression in ESCC was significantly lower than those in tumor-adjacent tissue and normal esophageal tissue (41.79% vs 58.21%, 68.66%, P < 0.05 for both). The positive rate of STAT3 expression was significantly higher in ESCC than in tumor-adjacent tissue and normal esophageal tissue (80.60% vs 71.64%, 53.73%, P < 0.05 for both). Expression of GPRC5A was significantly associated with tumor invasion depth and histological grade, but not with age, sex or lymph node metastasis. STAT3 expression was significantly associated with tumor invasion depth and histological grade, but not with age, sex or lymph node metastasis. GPRC5A protein expression was positively correlated with the expression of STAT3 proteins (r = -0.254, P < 0.05).

CONCLUSION: GPRC5A and STAT3 may participate in the occurrence and metastasis of esophageal carcinoma. Combined detection of the expression of these proteins will be helpful to the diagnosis of esophageal carcinoma and accurate determination of the biological behavior of this malignancy. GPRC5A and STAT3 may become new targets for gene therapy of esophageal carcinoma.

MiR-103a-3p targets the 5' UTR of GPRC5A in pancreatic cells

MicroRNAs (miRNAs) are short noncoding RNAs that regulate the expression of their targets in a sequence-dependent manner. For protein-coding transcripts, miRNAs regulate expression levels through binding sites in either the 3' untranslated region (3' UTR) or the amino acid coding sequence (CDS) of the targeted messenger RNA (mRNA). Currently, for the 5' untranslated region (5' UTR) of mRNAs, very few naturally occurring examples exist whereby the targeting miRNA down-regulates the expression of the corresponding mRNA in a seed-dependent manner. Here we describe and characterize two miR-103a-3p target sites in the 5' UTR of GPRC5A, a gene that acts as a tumor suppressor in some cancer contexts and as an ongocene in other cancer contexts. In particular, we show that the interaction of miR-103a-3p with each of these two 5' UTR targets reduces the expression levels of both GPRC5A mRNA and GPRC5A protein in one normal epithelial and two pancreatic cancer cell lines. By ectopically expressing "sponges" that contain instances of the wild-type 5' UTR targets we also show that we can reduce miR-103a-3p levels and increase GPRC5A mRNA and protein levels. These findings provide some first knowledge on the post-transcriptional regulation of this tumor suppressor/oncogene and present additional evidence for the participation of 5' UTRs in miRNA driven post-transcriptional regulatory control.

Analysis of long non-coding RNA expression profiles in gastric cancer

AIM: To investigate the expression patterns of long non-coding RNAs (lncRNAs) in gastric cancer.

METHODS: Two publicly available human exon arrays for gastric cancer and data for the corresponding normal tissue were downloaded from the Gene Expression Omnibus (GEO). We re-annotated the probes of the human exon arrays and retained the probes uniquely mapping to lncRNAs at the gene level. LncRNA expression profiles were generated by using robust multi-array average method in affymetrix power tools. The normalized data were then analyzed with a Bioconductor package linear models for microarray data and genes with adjusted P-values below 0.01 were considered differentially expressed. An independent data set was used to validate the results.

RESULTS: With the computational pipeline established to re-annotate over 6.5 million probes of the Affymetrix Human Exon 1.0 ST array, we identified 136053 probes uniquely mapping to lncRNAs at the gene level. These probes correspond to 9294 lncRNAs, covering nearly 76% of the GENCODE lncRNA data set. By analyzing GSE27342 consisting of 80 paired gastric cancer and normal adjacent tissue samples, we identified 88 lncRNAs that were differentially expressed in gastric cancer, some of which have been reported to play a role in cancer, such as LINC00152, taurine upregulated 1, urothelial cancer associated 1, Pvt1 oncogene, small nucleolar RNA host gene 1 and LINC00261. In the validation data set GSE33335, 59% of these differentially expressed lncRNAs showed significant expression changes (adjusted P-value < 0.01) with the same direction.

CONCLUSION: We identified a set of lncRNAs differentially expressed in gastric cancer, providing useful information for discovery of new biomarkers and therapeutic targets in gastric cancer.

A 4-gene panel as a marker at chromosome 8q in Asian gastric cancer patients

A widely held viewpoint is that the use of multiple markers, combined in some type of algorithm, will be necessary to provide high enough discrimination between diseased cases and non-diseased. We applied stepwise logistic regression analysis to identify the best combination of the 32 biomarkers at chromosome 8q on an independent public microarray test set of 80 paired gastric samples. A combination of SULF1, INTS8, ATP6V1C1, and GPR172A was identified with a prediction accuracy of 98.0% for discriminating carcinomas from adjacent noncancerous tissues in our previous 25 paired samples. Interestingly, the overexpression of SULF1 was associated with tumor invasion and metastasis. Function prediction analysis revealed that the 4-marker panel was mainly associated with acidification of intracellular compartments. Taken together, we found a 4-gene panel that accurately discriminated gastric carcinomas from adjacent noncancerous tissues and these results had potential clinical significance in the early diagnosis and targeted treatment of gastric cancer.

Overexpression of retinoic acid-induced protein 3 predicts poor prognosis for hepatocellular carcinoma

AIM

To investigate clinical significance of retinoic acid-induced protein 3 (RAI3) in hepatocellular carcinoma (HCC).

METHODS

Expression of RAI3 at both mRNA and protein levels in tumor, para-tumor and normal liver tissues was detected in 106 HCC patients by real-time quantitative RT-PCR, Western blot and immunohistochemistry. Then, the correlation of RAI3 expression with clinicopathological characteristics and survivals of HCC patients was analyzed.

RESULTS

Our data first found that RAI3 mRNA and protein expression were both significantly higher in HCC than in para-tumor (both P < 0.001) and normal liver tissues (both P < 0.001). The correlation analysis showed a positive correlation between RAI3 mRNA level and RAI3 protein level in HCC tissues (r = 0.8, P < 0.001). Immunohistochemistry data also revealed that overexpression of RAI3 was present in 73.6 % (78/106) of HCC tissues. In addition, high RAI3 protein expression was correlated with advanced TNM stage (P = 0.001), high serum AFP (P = 0.008), vascular invasion (P = 0.01) and tumor recurrence (P = 0.008). Moreover, HCC patients with overexpression of RAI3 had significantly shorter overall (P = 0.01) and disease-free survival (P = 0.01). Furthermore, multivariate analysis showed that overexpression of RAI3 was an independent prognostic factor for both overall (P = 0.02) and disease-free survival (P = 0.03) in HCC.

CONCLUSION

Our data for the first time provide a basis for the concept that overexpression of RAI3 may contribute to the malignant progression of HCC and predict poor prognosis for patients with this deadly disease after curative hepatectomy. RAI3 might be an important marker for tumor progression and prognosis, as well as a potential therapeutic target of HCC.