Inhibition of GPR137 expression reduces the proliferation and colony formation of malignant glioma cells

GPR137 Inhibits Cell Proliferation and Promotes Neuronal Differentiation in the Neuro2a Cells

The orphan receptor, G protein-coupled receptor 137 (GPR137), is an integral membrane protein involved in several types of cancer. GPR137 is expressed ubiquitously, including in the central nervous system (CNS). We established a GPR137 knockout (KO) neuro2A cell line to analyze GPR137 function in neuronal cells. KO cells were generated by genome editing using clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 and cultured as single cells by limited dilution. Rescue cells were then constructed to re-express GPR137 in GPR137 KO neuro2A cells using an expression vector with an EF1-alpha promoter. GPR137 KO cells increased cellular proliferation and decreased neurite outgrowth (i.e., a lower level of neuronal differentiation). Furthermore, GPR137 KO cells exhibited increased expression of a cell cycle regulator, cyclin D1, and decreased expression of a neuronal differentiation marker, NeuroD1. Additionally, GPR137 KO cells exhibited lower expression levels of the neurite outgrowth markers STAT3 and GAP43. These phenotypes were all abrogated in the rescue cells. In conclusion, GPR137 deletion increased cellular proliferation and decreased neuronal differentiation, suggesting that GPR137 promotes cell cycle exit and neuronal differentiation in neuro2A cells. Regulation of neuronal differentiation by GPR137 could be vital to constructing neuronal structure during brain development.

Network pharmacological systems study of Huang-Lian-Tang in the treatment of glioblastoma multiforme

Glioblastoma multiforme (GBM) has a poor prognosis and its recurrence and mortality rates are high. At present, there is no effective clinical method to control its progression and recurrence. Traditional Chinese Medicine has a high status not only in China, but also in the world. Certain drugs are also used in the clinical treatment of tumor diseases. In clinical practice, Huang-Lian-Tang (HLT) has proven efficacy in treating brain diseases and preventing tumor recurrence. However, the mechanisms of action have remained elusive. The present study explored the potential mechanisms of HLT in the treatment of gliomas based on network pharmacology. First, information on the composition of HLT was obtained from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform, and the composition and targets of the chemical substances contained in the herbs were analyzed. Subsequently, a pharmacological interaction network for HLT was built. Furthermore, the expressed genes of patients with GBM were obtained from Gene Expression Omnibus database and screened. A protein-protein interaction network was then constructed for both sets of data and they were combined with a topology method for analysis. Finally, the screened genes were subjected to enrichment analysis and pathway analysis. A total of 386 candidate targets and 7 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were screened, which were mainly associated with amino acid metabolism. Gene Ontology enrichment analysis and KEGG signal pathway analysis indicated that these targets are involved in anti-apoptosis, anti-oxidative stress, multicellular biological processes and other physiological and pathological processes related to the occurrence and development of GBM. In conclusion, the present results indicated that the mechanisms of action of HLT against GBM involve multiple targets and signaling pathways that are related to tumorigenesis and progression. The present study not only provided a novel theoretical basis for Traditional Chinese Medicine to treat tumors but also novel ideas for the treatment of GBM.

GPR137 is a promising novel bio-marker for the prognosis of bladder cancer patients

OBJECTIVES

G protein-coupled receptor 137 (GPR137) was reported to be associated with several cancers, but its role in bladder cancer has not been reported. The purpose of this study was to evaluate clinical significance of GPR137 in bladder cancer.

METHODS

The expressions of GPR137 in pathological tissues and corresponding normal tissues from bladder cancer patients were detected via quantitative real time polymerase chain reaction (qRT-PCR). Western blot was performed to detect GPR137 expression in bladder cancer tissues and adjacent normal tissues. Chi-Squared test analyzed the relationship between GPR137 expression and clinical features of bladder cancer patients. Additionally, Kaplan-Meier method was adopted in estimating overall survival of bladder cancer patients. Prognostic value of GPR137 was evaluated through Cox regression analysis.

RESULTS

The expression of GPR137 mRNA and protein in pathological tissues was significantly higher than that in adjacent normal tissues (P < .001). Moreover, similar result was found for bladder cancer patients and healthy controls (P < .001). And GPR137 expression was associated with tumor size (P = .006) and TNM stage (P = .012). The results of Kaplan-Meier analysis suggested that patients with high expression of GPR137 had shorter overall survival time than those with low expression (Log rank test, P = .001). Cox regression analysis indicated that GPR137 could act as an independent biomarker for bladder cancer prognosis (HR = 1.850, 95% CI = 1.272-2.689, P = .001).

CONCLUSION

Abnormal expression of GPR137 is associated with bladder cancer and GPR137 is a potential biomarker for the therapy and prognosis of bladder cancer.

Putative Receptors Underpinning l-Lactate Signalling in Locus Coeruleus

The importance of astrocytic l-lactate (LL) for normal functioning of neural circuits such as those regulating learning/memory, sleep/wake state, autonomic homeostasis, or emotional behaviour is being increasingly recognised. l-Lactate can act on neurones as a metabolic or redox substrate, but transmembrane receptor targets are also emerging. A comparative review of the hydroxy-carboxylic acid receptor (HCA1, formerly known as GPR81), Olfactory Receptor Family 51 Subfamily E Member 2 (OR51E2), and orphan receptor GPR4 highlights differences in their LL sensitivity, pharmacology, intracellular coupling, and localisation in the brain. In addition, a putative Gs-coupled receptor on noradrenergic neurones, LLRx, which we previously postulated, remains to be identified. Next-generation sequencing revealed several orphan receptors expressed in locus coeruleus neurones. Screening of a selection of these suggests additional LL-sensitive receptors: GPR180 which inhibits and GPR137 which activates intracellular cyclic AMP signalling in response to LL in a heterologous expression system. To further characterise binding of LL at LLRx, we carried out a structure–activity relationship study which demonstrates that carboxyl and 2-hydroxyl moieties of LL are essential for triggering d-lactate-sensitive noradrenaline release in locus coeruleus, and that the size of the LL binding pocket is limited towards the methyl group position. The evidence accumulating to date suggests that LL acts via multiple receptor targets to modulate distinct brain functions.

GRP137 promotes cell proliferation and metastasis through regulation of the PI3K/AKT pathway in human ovarian cancer

PURPOSE

Ovarian cancer is one of the leading causes of death for women worldwide. The present study aims to investigate the role of G protein-coupled receptor 137 (GPR137) in the biological activities of ovarian cancer cells.

METHODS

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RESULTS

G protein-coupled receptor 137 was highly expressed in clinical ovarian cancer tissues and exhibited the highest protein levels in SKOV3 cells and OVCAR3 cells. Knockdown of GPR137 caused significant decreases in cell proliferative rates and colony formation abilities in SKOV3 cells and OVCAR3 cells and also inhibited the in vivo tumorigenesis in a xenograft model. It was observed that knockdown of GPR137 inhibited cell motility by up to 40% in SKOV3 cells and approximately 65% in OVCAR3 cells in wound-healing assay. Cell migration abilities were consistently inhibited by 68.2% in SKOV3 cells and 59.3% in OVCAR3 cells, whereas cell invasion abilities were inhibited by 64.0% and 74.2% in SKOV3 and OVCAR3 cells, respectively, after knockdown of GPR137. When GPR137 was depleted, epithelial markers were increased, while mesenchymal markers decreased.

CONCLUSIONS

Our data suggest that GPR137 plays pro-oncogenic roles in ovarian cancer via regulation of the PI3K/AKT pathway. These observations might pave new insights into therapeutic strategies against human ovarian cancer.

Small interfering RNA-mediated silencing of G-protein-coupled receptor 137 inhibits growth of osteosarcoma cells

Purpose

Osteosarcoma is the most widespread primary carcinoma in bones. Osteosarcoma cells are highly metastatic and frequently develop resistance to chemotherapy making this disease harder to treat. This identifies an urgent need of novel therapeutic strategies for osteosarcoma. G-Protein-coupled receptor 137 (GPR137) is involved in several human cancers and may be a novel therapeutic target.

Methods

The expression of GPR137 was assessed in one osteoblast and three human osteosarcoma cell lines via the quantitative real-time polymerase chain reaction and western blot assays. Stable GPR137 knockdown cell lines were established using an RNA interference lentivirus system. Viability, colony formation, and flow cytometry assays were performed to measure the effects of GPR137 depletion on cell growth. The underlying molecular mechanism was determined using signaling array analysis and western blot assays.

Results

GPR137 expression was higher in the three human osteosarcoma cell lines, Saos-2, U2OS, and SW1353, than in osteoblast hFOB 1.19 cells. Lentivirus-mediated small interfering RNA targeting GPR137 successfully knocked down GPR137 mRNA and protein expression in both Saos-2 and U2OS cells. In the absence of GPR137, cell viability and colony formation ability were seriously impaired. The extent of apoptosis was also increased in both cell lines. Moreover, AMP-activated protein kinase α, proline-rich AKT substrate of 40 kDa, AKT, and extracellular signal-regulated kinase phosphorylation levels were down-regulated in GPR137 knockdown cells.

Conclusions

The results of this study highlight the crucial role of GPR137 in promoting osteosarcoma cell growth in vitro. GPR137 could serve as a potential therapeutic target against osteosarcoma.

Bromodomain and Extraterminal Protein Inhibitor JQ1 Suppresses Thyroid Tumor Growth in a Mouse Model

PURPOSE

New therapeutic approaches are needed for patients with thyroid cancer refractory to radioiodine treatment. An inhibitor of bromodomain and extraterminal domain (BET) proteins, JQ1, shows potent antitumor effects in hematological cancers and solid tumors. To evaluate whether JQ1 is effective against thyroid cancer, we examined antitumor efficacy of JQ1 using the ThrbPV/PVKrasG12D mouse, a model of anaplastic thyroid cancer.

EXPERIMENTAL DESIGN

We treated ThrbPV/PVKrasG12D mice with vehicle or JQ1 at a dose of 50 mg/kg body weight/day starting at the age of 8 weeks for a 10-week period and monitored thyroid tumor progression.

RESULTS

JQ1 markedly inhibited thyroid tumor growth and prolonged survival of these mice. Global differential gene expression analysis showed that JQ1 suppressed the cMyc (hereafter referred to as Myc) transcription program by inhibiting mRNA expression of Myc, ccnd1, and other related genes. JQ1-suppressed Myc expression was accompanied by chromatin remodeling as evidenced by increased expression of histones and hexamethylene bis-acetamide inducible 1, a suppressor of RNA polymerase II transcription elongation. Analyses showed that JQ1 decreased MYC abundance in thyroid tumors and attenuated the cyclin D1-CDK4-Rb-E2F3 signaling to decrease tumor growth. Further analysis indicated that JQ1 inhibited the recruitment of BDR4 to the promoter complex of the Myc and Ccnd1 genes in rat thyroid follicular PCCL3 cells, resulting in decreased MYC expression at the mRNA and protein levels to inhibit tumor cell proliferation.

CONCLUSIONS

These preclinical findings suggest that BET inhibitors may be an effective agent to reduce thyroid tumor burden for the treatment of refractory thyroid cancer. Clin Cancer Res; 23(2); 430-40. ©2016 AACR.

G-protein-coupled receptor 137 accelerates proliferation of urinary bladder cancer cells in vitro

Urinary bladder cancer is a worldwide concern because of its level of incidence and recurrence. To search an effective therapeutic strategy for urinary bladder cancer, it is important to identify proteins involved in tumorigenesis that could serve as potential targets for diagnosis and treatment. G-protein-coupled receptors (GPRs) constitute a large protein family of receptors that sense molecules outside the cell and activate signal transduction pathways and cellular responses inside the cell. GPR137 is a newly discovered human gene encoding orphan GPRs. In this study, we aimed to investigate the physiological role of GPR137 in urinary bladder cancer. The effect of GPR137 on cell growth was examined via an RNA interference (RNAi) lentivirus system in two human urinary bladder cancer cell lines BT5637 and T24. Lentivirus-mediated RNAi could specifically suppressed GPR137 expression in vitro, resulting in alleviated cell viability and impaired colony formation, as well as blocks G0/G1 and S phases of the cell cycle. These results suggested GPR137 as an essential player in urinary bladder cancer cell growth, and it may serve as a potential target for gene therapy in the treatment of urinary bladder cancer.

Inhibition of GPR137 suppresses proliferation of medulloblastoma cells in vitro

Medulloblastoma is the most common malignant pediatric brain tumor in children. GPR137 is a ubiquitously expressed gene in the central nervous system. It has been reported that GPR137 modulates malignant proliferation of glioma cells. However, the relationship between GPR137 and medulloblastoma is still unknown. In this study, we knocked down GPR137 in the medulloblastoma cell line Daoy via a lentivirus-based RNA interference system to explore its role in medulloblastoma. Functional analyses showed that cell proliferation and colony formation were obviously restrained in Daoy cells after GPR137 knockdown. Furthermore, knockdown of GPR137 in Daoy cells led to a significant increase in cell percentage in the G0/G1 phase but a decrease in the S phase. Additionally, the cell population in the sub-G1 phase, which represents apoptotic cells, was remarkably increased in GPR137 knockdown cells. GPR137 inhibition induced a strong proapoptotic effect in Daoy cells, as confirmed by annexin V-APC/7-AAD double staining. In conclusion, GPR137 knockdown inhibited growth of Daoy medulloblastoma cells via disturbing cell cycle progression and inducing apoptosis. Our investigation suggested that GPR137 could be a potential oncogene in medulloblastoma cells and might serve as a target for the treatment of medulloblastoma.