Prostate-specific G-protein Coupled Receptor Research Articles

Exosomal prostate-specific G-protein-coupled receptor induces osteoblast activity to promote the osteoblastic metastasis of prostate cancer.

BackgroundProstate cancer (PCa) is the second leading cause of cancer-related deaths worldwide. Prostate-specific G-protein-coupled receptor (PSGR) has been identified as a new potential biomarker and therapeutic target for PCa. However, the influence of exosomal PSGR on PCa metastasis remains unknown. This study aimed to identify the regulatory role of exosomal PSGR in the bone microenvironment, prior to metastasis of PCa and the underlying mechanism.MethodshFOB1.19 cells were co-cultured with PC-3 exosomes exhibiting PSGR overexpression. Alkaline phosphatase (ALP) and von Kossa staining methods were used to measure the osteogenesis of hFOB1.19 cells. RNA sequencing was used to screen the downstream target genes of PSGR and the signaling pathways involved. The expression of the candidate genes was verified using quantitative real-time polymerase chain reaction (qRT-PCR).ResultsALP and von Kossa staining results showed that PC-3 exosomes with overexpressed PSGR enhanced osteogenesis of hFOB1.19 cells. A total of 853 mRNAs were differentially expressed in hFOB1.19 cells of the PSGR-overexpressing PC3 cell (PC3PSGR+ exosome) group compared to the negative exosome control (NC) group, among which 182 mRNAs were significantly upregulated and 671 were downregulated. The functional enrichment and pathway analysis showed that differentially expressed mRNAs were mainly involved in cellular responses to interleukin-1 (IL1), chemotaxis, inflammation, transcriptional misregulation in cancer, and MAKP and NF-κB signaling pathways. qRT-PCR showed that levels of intercellular adhesion molecule-1 (ICAM1), RELB proto-oncogene, NF-κB subunit (RELB), and IL1 beta (IL1B) were significantly decreased in hFOB1.19 cells of the PSGR-overexpression group.ConclusionsThis study suggests that PSGR may regulate the MAKP and NF-κB signaling pathways involved in the process of bony metastases by targeting ICAM1, RELB, and IL1B.

Activation of PSGR with β-ionone suppresses prostate cancer progression by blocking androgen receptor nuclear translocation.

The prostate-specific G protein-coupled receptor (PSGR) is a class A G protein-coupled receptor (GPCR) that is specifically expressed in prostate epithelial cells, and its expression has been linked to prostate cancer (PCa) progression. Here, we show that activation of PSGR with its ligand β-ionone, an end-ring analog of β-carotenoid, can suppress PCa cell growth both in vitro and in vivo model. Dissection of the mechanism underlying this relationship reveals that activation of PSGR by β-ionone suppresses AR nuclear translocation via phosphorylation of AR at residue Ser650 by p38 and JNK, which leads to the suppression of AR transactivation, further suppressing PCa cell growth. Overall, we link a cancer cell-specific GPCR with the nuclear AR and show that targeting PSGR can provide us a new target to combat PCa better.

Dynamical Binding Modes Determine Agonistic and Antagonistic Ligand Effects in the Prostate-Specific G-Protein Coupled Receptor (PSGR)

We analysed the ligand-based activation mechanism of the prostate-specific G-protein coupled receptor (PSGR), which is an olfactory receptor that mediates cellular growth in prostate cancer cells. Furthermore, it is an olfactory receptor with a known chemically near identic antagonist/agonist pair, α- and β-ionone. Using a combined theoretical and experimental approach, we propose that this receptor is activated by a ligand-induced rearrangement of a protein-internal hydrogen bond network. Surprisingly, this rearrangement is not induced by interaction of the ligand with the network, but by dynamic van der Waals contacts of the ligand with the involved amino acid side chains, altering their conformations and intraprotein connectivity. Ligand recognition in this GPCR is therefore highly stereo selective, but seemingly lacks any ligand recognition via polar contacts. A putative olfactory receptor-based drug design scheme will have to take this unique mode of protein/ligand action into account.

Prostate-Specific G-Protein Coupled Receptor, an Emerging Biomarker Regulating Inflammation and Prostate Cancer Invasion.

Prostate cancer is highly prevalent among men in developed countries, but a significant proportion of detected cancers remain indolent, never progressing into aggressive carcinomas. This highlights the need to develop refined biomarkers that can distinguish between indolent and potentially dangerous cases. The prostate-specific G-protein coupled receptor (PSGR, or OR51E2) is an olfactory receptor family member with highly specific expression in human prostate epithelium that is highly overexpressed in PIN and prostate cancer. PSGR has been functionally implicated in prostate cancer cell invasiveness, suggesting a potential role in the transition to metastatic PCa. Recently, transgenic mice overexpressing PSGR in the prostate were reported to develop an acute inflammatory response followed by emergence of low grade PIN, whereas mice with compound PSGR overexpression and loss of PTEN exhibited accelerated formation of invasive prostate adenocarcinoma. This article will review recent PSGR findings with a focus on its role as a potential prostate cancer biomarker and regulator of prostate cancer invasion and inflammation.

Prostate specific G protein coupled receptor is associated with prostate cancer prognosis and affects cancer cell proliferation and invasion.

BackgroundThere is limited information about the clinical and biological significance of prostate specific G protein coupled receptor (PSGR) in prostate cancer (PCa) initiation and progression. Here, we evaluated the expression of PSGR protein, studied its diagnostic and prognostic value in PCa, and also explored its role in cancer cell growth and invasion.MethodsThe expression of PSGR in paired adjacent normal prostate, high grade prostatic intraepithelial neoplasia (PIN), and PCa were determined by immunohistochemistry on tissue microarrays constructed from 150 radical prostatectomy specimens. The effects of PSGR on PCa cell growth and invasion were investigated using human PCa cell lines.ResultsMembranous and cytoplasmic PSGR staining was observed at luminal epithelial cells of prostate. PSGR protein expression was significantly higher in PIN compared to normal prostate. Interestingly, the expression of PSGR decreased as PIN progressed to PCa. Low PSGR expression in PCa was associated with high Gleason score, and poor overall survival. Activated PSGR increased cancer cell invasive ability, but retarded cell growth. PSGR did not affect mTOR activity, but suppressed P70 S6 kinase activity.ConclusionsPSGR may participate in PCa progression through affecting cell proliferation and invasion. High expression of PSGR in PIN may implicate its role in early neoplastic transformation of PCa. Low expression of PSGR in PCa may serve as a potential indicator for poor prognosis.

Prostate-specific G-protein-coupled receptor collaborates with loss of PTEN to promote prostate cancer progression.

Among frequent events in prostate cancer are loss of the tumor-suppressor phosphatase and tensin homologue (PTEN) and overexpression of prostate-specific G-protein-coupled receptor (PSGR), but the potential tumorigenic synergy between these lesions is unknown. Here, we report a new mouse model (PSGR-Pten(Δ/Δ)) combining prostate-specific loss of Pten with probasin promoter-driven PSGR overexpression. By 12 months PSGR-Pten(Δ/Δ) mice developed invasive prostate tumors featuring Akt activation and extensive inflammatory cell infiltration. PSGR-Pten(Δ/Δ) tumors exhibited E-cadherin loss and increased stromal androgen receptor (AR) expression. PSGR overexpression increased LNCaP proliferation, whereas PSGR short hairpin RNA knockdown inhibited proliferation and migration. In conclusion, we demonstrate that PSGR overexpression synergizes with loss of PTEN to accelerate prostate cancer development, and present a novel bigenic mouse model that mimics the human condition, where both PSGR overexpression and loss of PTEN occur concordantly in the majority of advanced prostate cancers, yielding an environment more relevant to studying human prostate cancer.

PSGR promotes prostatic intraepithelial neoplasia and prostate cancer xenograft growth through NF-κB.

Prostate-specific G-protein-coupled receptor (PSGR), a member of the olfactory subfamily of G-protein-coupled receptors, is specifically expressed in human prostate tissue and overexpressed in prostate cancer (PCa). This expression pattern suggests a possible role in PCa initiation and progression. We developed a PSGR transgenic mouse model driven by a probasin promoter and investigated the role of PSGR in prostate malignancy. Overexpression of PSGR induced a chronic inflammatory response that ultimately gave rise to premalignant mouse prostate intraepithelial neoplasia lesions in later stages of life. PSGR-overexpressing LnCaP cells in prostate xenografts formed larger tumors compared with normal LnCaP cancer cells, suggesting a role of PSGR in the promotion of tumor development. Furthermore, we identified nuclear factor-κB (NF-κB) or RELA as a key downstream target activated by PSGR signaling. We also show that this regulation was mediated in part by the phosphatidylinositol-3-kinase/Akt (PI3K/AKT) pathway, highlighting a collaborative role between PI3K/AKT and NF-κB during tumor inflammation downstream of PSGR in the initial phases of prostate disease.

Promotion of Cancer Cell Invasiveness and Metastasis Emergence Caused by Olfactory Receptor Stimulation

Olfactory receptors (ORs) are expressed in the olfactory epithelium, where they detect odorants, but also in other tissues with additional functions. Some ORs are even overexpressed in tumor cells. In this study, we identified ORs expressed in enterochromaffin tumor cells by RT-PCR, showing that single cells can co-express several ORs. Some of the receptors identified were already reported in other tumors, but they are orphan (without known ligand), as it is the case for most of the hundreds of human ORs. Thus, genes coding for human ORs with known ligands were transfected into these cells, expressing functional heterologous ORs. The in vitro stimulation of these cells by the corresponding OR odorant agonists promoted cell invasion of collagen gels. Using LNCaP prostate cancer cells, the stimulation of the PSGR (Prostate Specific G protein-coupled Receptor), an endogenously overexpressed OR, by β-ionone, its odorant agonist, resulted in the same phenotypic change. We also showed the involvement of a PI3 kinase γ dependent signaling pathway in this promotion of tumor cell invasiveness triggered by OR stimulation. Finally, after subcutaneous inoculation of LNCaP cells into NSG immunodeficient mice, the in vivo stimulation of these cells by the PSGR agonist β-ionone significantly enhanced metastasis emergence and spreading.

Identification of Prostate-Specific G-Protein Coupled Receptor as a Tumor Antigen Recognized by CD8+ T Cells for Cancer Immunotherapy

BackgroundProstate cancer is the most common cancer among elderly men in the US, and immunotherapy has been shown to be a promising strategy to treat patients with metastatic castration-resistant prostate cancer. Efforts to identify novel prostate specific tumor antigens will facilitate the development of effective cancer vaccines against prostate cancer. Prostate-specific G-protein coupled receptor (PSGR) is a novel antigen that has been shown to be specifically over-expressed in human prostate cancer tissues. In this study, we describe the identification of PSGR-derived peptide epitopes recognized by CD8+ T cells in an HLA-A2 dependent manner.Methodology/Principal FindingsTwenty-one PSGR-derived peptides were predicted by an immuno-informatics approach based on the HLA-A2 binding motif. These peptides were examined for their ability to induce peptide-specific T cell responses in peripheral blood mononuclear cells (PBMCs) obtained from either HLA-A2+ healthy donors or HLA-A2+ prostate cancer patients. The recognition of HLA-A2 positive and PSGR expressing LNCaP cells was also tested. Among the 21 PSGR-derived peptides, three peptides, PSGR3, PSGR4 and PSGR14 frequently induced peptide-specific T cell responses in PBMCs from both healthy donors and prostate cancer patients. Importantly, these peptide-specific T cells recognized and killed LNCaP prostate cancer cells in an HLA class I-restricted manner.Conclusions/SignificanceWe have identified three novel HLA-A2-restricted PSGR-derived peptides recognized by CD8+ T cells, which, in turn, recognize HLA-A2+ and PSGR+ tumor cells. The PSGR-derived peptides identified may be used as diagnostic markers as well as immune targets for development of anticancer vaccines.

G Protein-coupled Receptor Signaling via Src Kinase Induces Endogenous Human Transient Receptor Potential Vanilloid Type 6 (TRPV6) Channel Activation

Ca(2+) homeostasis plays a critical role in a variety of cellular processes. We showed previously that stimulation of the prostate-specific G protein-coupled receptor (PSGR) enhances cytosolic Ca(2+) and inhibits proliferation of prostate cells. Here, we analyzed the signaling mechanisms underlying the PSGR-mediated Ca(2+) increase. Using complementary molecular, biochemical, electrophysiological, and live-cell imaging techniques, we found that endogenous Ca(2+)-selective transient receptor potential vanilloid type 6 (TRPV6) channels are critically involved in the PSGR-induced Ca(2+) signal. Biophysical characterization of the current activated by PSGR stimulation revealed characteristic properties of TRPV6. The molecular identity of the involved channel was confirmed using RNA interference targeting TrpV6. TRPV6-mediated Ca(2+) influx depended on Src kinase activity. Src kinase activation occurred independently of G protein activation, presumably by direct interaction with PSGR. Taken together, we report that endogenous TRPV6 channels are activated downstream of a G protein-coupled receptor and present the first physiological characterization of these channels in situ.

PSGR and PCA3 as biomarkers for the detection of prostate cancer in urine

Several studies have demonstrated the usefulness of monitoring an RNA transcript in urine, such as PCA3, for prostate cancer (PCa) diagnosis. PCa screening would benefit from additional biomarkers of higher specificity and could be used in conjunction with prostate-specific antigen (PSA) testing, in order to better determine biopsy candidates. We used urine sediments after prostate massage (PM) from 215 consecutive patients, who presented for prostate biopsy. We tested whether prostate-specific G-protein coupled receptor (PSGR), a biomarker previously described to be over-expressed in PCa tissue, could also be detected by quantitative real-time PCR in post-PM urine sediment. We combined these findings with prostate cancer gene 3 (PCA3), the current gold standard for PCa diagnosis in urine, to test if a combination of both biomarkers could improve the sensitivity of PCA3 alone. By univariate analysis we found that PSGR and PCA3 were significant predictors of PCa. Receiver operator characteristic curve analysis and its multivariate extension, multivariate ROC (MultiROC), were used to assess the outcome predictive values of the individual and the paired biomarkers. We obtained the following area under the curve values: PSA (0.602), PSGR (0.681), PCA3 (0.656), and PSGRvPCA3 (0.729). Then, we tested whether a combination of PSGR and PCA3 could improve specificity by fixing the sensitivity at 95%. We obtained specificities of 15% (PSGR), 17% (PCA3), and 34% (PSGRvPCA3). A multiplexed model including PSGR and PCA3 improves the specificity for the detection of PCa, especially in the area of high sensitivity. This could be clinically useful for determining which patients should undergo biopsy.

Activation of an Olfactory Receptor Inhibits Proliferation of Prostate Cancer Cells

Olfactory receptors (ORs) are expressed not only in the sensory neurons of the olfactory epithelium, where they detect volatile substances, but also in various other tissues where their potential functions are largely unknown. Here, we report the physiological characterization of human OR51E2, also named prostate-specific G-protein-coupled receptor (PSGR) due to its reported up-regulation in prostate cancer. We identified androstenone derivatives as ligands for the recombinant receptor. PSGR can also be activated with the odorant beta-ionone. Activation of the endogenous receptor in prostate cancer cells by the identified ligands evoked an intracellular Ca2+ increase. Exposure to beta-ionone resulted in the activation of members of the MAPK family and inhibition of cell proliferation. Our data give support to the hypothesis that because PSGR signaling could reduce growth of prostate cancer cells, specific receptor ligands might therefore be potential candidates for prostate cancer treatment.

Production of Antibodies against Multipass Membrane Proteins Expressed in Human Tumor Cells Using Dendritic Cell Immunization

Antibody mediated therapeutic strategies against human malignant tumors have been widely authorized and clinically applied to cancer patients. In order to develop methods to generate antibodies reactive to the extracellular domains of multipass plasma membrane proteins specifically expressed in malignant tumors, we examined the use of dendritic cells (DCs) for immunization. DCs were transduced with genes encoding the human six transmembrane epithelial antigen of prostate 1 (STEAP1), STEAP4, and seven transmembrane prostate specific G-protein coupled receptor (PSGR). Mice were immunized with these DCs and followed by repeated booster immunization with plasmids expressing each protein. The immunized mice produced significant amounts of antibodies against these proteins. Our results suggest that DC immunization is an effective method to produce antibodies reactive to extracellular regions of plasma membrane proteins with multiple-transmembrane domains, and may be useful to develop antibody mediated antitumor therapies.

Increased expression of prostate‐specific G‐protein‐coupled receptor in human prostate intraepithelial neoplasia and prostate cancers

The G-protein-coupled receptors and signal transduction pathways represent important specific targets for a variety of human diseases, ranging from the control of blood pressure, allergic response, hormonal disorders and neurologic diseases to tumorigenesis. Most recently, we and others have identified a novel human prostate-specific G-protein coupled receptor (PSGR). To investigate the potential roles of PSGR in human normal prostate and prostate cancers, we examined the expression level of PSGR in 146 human prostate samples with real-time quantitative reverse transcription-PCR and in situ hybridization method. We significantly extended previous studies and demonstrated that PSGR is specifically expressed in human prostate tissues, not in any other normal and tumor samples tested. Compared to normal and benign prostatic hyperplasia tissues, the expression of PSGR increased significantly in human prostate intraepithelial neoplasia (PIN) and prostate tumors (approximately 10-fold), especially in early prostate tumors, suggesting PSGR may play an important role in early prostate cancer development and progression. The sensitivity and specificity estimates for PSGR expression were calculated as the area under the receiver-operating characteristics curve (0.902), indicating high-level sensitivity and specificity for discriminating benign prostate tissues from malignant prostate tissues. The association of PSGR expression with clinical parameters (clinical stages, Gleason scores, recurrent status and metastasis) was also investigated in this study. Our data suggest that overexpression of PSGR in human PIN and prostate cancers have the potential for early prostate cancer detection and diagnosis.