Search

OBJECTIVES Tumor Treating Fields (TTFields) are approved in combination with temozolomide for newly diagnosed glioblastoma (GBM). TTFields are low-intensity alternating electric fields that are thought to disturb mitotic macromolecules’ assembly. The addition of TTFields resulted in a significant improvement in overall survival. However, most GBM patients eventually develop resistance to TTFields and the mechanism remains unexplored. METHODS Multiple GBM cell lines were treated continuously at clinically approved frequency of 200 kHz using an in vitro TTFields system until cells with relative resistance to the cytotoxic effects of TTFields. A systems approach aided by innovative network ranking computational algorithms were utilized to analyze global gene expression profiles and identify resistance pathways, which were subsequently validated experimentally. RESULTS TTFields-induced chromosomal instability is preserved in resistant cells, indicating that TTFields resistance is mediated through a non-biophysical mechanism. This acquired TTFields resistance phenotype is associated with a transition of GBM cells to a stem-like state as determined by a neurosphere assay, stemness markers such as CD44 and increased tumorigenesis when implanted into mouse brain. Using an innovative computational platform-NETZEN, we methodically dissected this stemness program in resistant cells. 3 networks were found disrupted and all play critical roles in GBM stemness. Mechanistically, Prostaglandin E Receptor 3 (PTGER3) is the top ranked regulator responsible for resistance. PTGER3 is rapidly upregulated both in vitro and in vivo upon exposure to TTFields and further increases with prolonged treatment as resistance sets in. Immunofluorescence staining shows PTGER3’s nuclear translocation along with Lamin A/C disruption in response to TTFields. Pharmacological inhibition of PTGER3 using aspirin or PTGER3-specific inhibitors resensitized or prevent cells becoming resistance to TTFields. CONCLUSIONS We have identified a novel regulator PTGER3 at the apex that plays a critical role in TTFields resistance. This is a potential therapeutic target to reduce resistance to TTFields therapy in GBM.

Prostaglandin E receptor subtype 4 (EP4) is widely distributed in the heart, but its role in hepatic ischemia/reperfusion (I/R), particularly in mitochondrial permeability transition pore (MPTP) modulation, is yet to be elucidated. In the present study, an EP4 agonist (CAY10598) was used in a rat model to evaluate the effects of EP4 activation on liver I/R and the mechanisms underlying this. I/R insult upregulated hepatic EP4 expression during early reperfusion. In addition, subcutaneous CAY10598 injection prior to the onset of reperfusion significantly increased hepatocyte cAMP concentrations and decreased serum ALT and AST levels and necrotic and apoptotic cell percentages, after 6 h of reperfusion. Moreover, CAY10598 protected mitochondrial morphology, markedly inhibited mitochondrial permeability transition pore (MPTP) opening and decreased liver reactive oxygen species levels. This occurred via activation of the ERK1/2‑GSK3β pathway rather than the janus kinase (JAK)2‑signal transducers and activators of transcription (STAT)3 pathway, and resulted in prevention of mitochondria‑associated cell injury. The MPTP opener carboxyatractyloside (CATR) and the ERK1/2 inhibitor PD98059 also partially reversed the protective effects of CAY10598 on the liver and mitochondria. The current findings indicate that EP4 activation induces ERK1/2‑GSK3β signaling and subsequent MPTP inhibition to provide hepatoprotection, and these observations are informative for developing new molecular targets and preventative therapies for I/R in a clinical setting.

The purpose of this study was to investigate whether genetic ablation of prostaglandin E receptor subtype 4 (EP4) affects white adipose tissue (WAT) remodeling mediated by β3-adrenergic stimulation...

The molecular expression profiles of zebrafish ep2aand ep4bhave not been defined to-date. Phylogenetic treesof EP2a and EP4b in zebrafish and other speciesrevealed that human EP4and zebrafish EP4b were more closely related than EP2a. ZebrafishEP2a is a 281amino acid protein with high identity to that of human (43%), mouse (44%), rat (43%),dog(44%), cattle(41%), and chicken (41%). ZebrafishEP4bencoded a precursor of 497amino acids with high amino acid identity to that of mammals, including human (57%), mouse (54%), rat (55%), dog (55%), cattle (56%), and chicken (54%). Whole-mount in situ hybridizationrevealed that ep2awas robustly expressed in the anterior four somitesat the 10-somites stages, but was absent in the somites at 19 hpf.Itwas observedagainin the pronephric duct at 24 hpf, in the intermediate cell masslocated in the trunk, and in the rostral blood island at 30 hpf. Ep2awas also expressed in the notochordat 48 hpf. During somitogenesis, ep4bwas highly expressed in the eyes, somites, and the trunk neural crest. From 30 to 48 hpf, ep4bcould be detected in the posterior cardinal vein and the neighboring ICM. From these data, we conclude that ep2aand ep4bare conserved in vertebrates and that the presence of ep2aand ep4btranscripts during developmental stages infers their role during early zebrafish larval development. In addition, the variable expression of the two receptor isoforms wasstrongly suggestive of divergent roles of molecular regulation.

Aim: Renal fibrosis plays a pivotal role in the development and progression of chronic kidney disease, which affects 10% of the adult population. Previously, it has been demonstrated that the cyclooxygenase-2 (COX-2)/prostaglandin (PG) system influences the progression of renal injury. Here, we evaluated the impact of butaprost, a selective EP2 receptor agonist, on renal fibrosis in several models of kidney injury, including human tissue slices. Methods: We studied the anti-fibrotic efficacy of butaprost using Madin-Darby Canine Kidney (MDCK) cells, mice that underwent unilateral ureteral obstruction and human precision-cut kidney slices. Fibrogenesis was evaluated on a gene and protein level by qPCR and Western blotting. Results: Butaprost (50 μM) reduced TGF-β-induced fibronectin (FN) expression, Smad2 phosphorylation and epithelial-mesenchymal transition in MDCK cells. In addition, treatment with 4 mg/kg/day butaprost attenuated the development of fibrosis in mice that underwent unilateral ureteral obstruction surgery, as illustrated by a reduction in the gene and protein expression of α-smooth muscle actin, FN and collagen 1A1. More importantly, a similar anti-fibrotic effect of butaprost was observed in human precision-cut kidney slices exposed to TGF-β. The mechanism of action of butaprost appeared to be a direct effect on TGF-β/Smad signalling, which was independent of the cAMP/PKA pathway. Conclusion: In conclusion, this study demonstrates that stimulation of the EP2 receptor effectively mitigates renal fibrogenesis in various fibrosis models. These findings warrant further research into the clinical application of butaprost, or other EP2 agonists, for the inhibition of renal fibrosis.

Background Elevated COX-2 expression has been correlated with inferior outcome in NSCLC. COX-2 catalyzes the transformation of arachidonate to PGE 2 . We and others have demonstrated that PGE 2 induces proliferation and metastatic spread and immunosuppression through the G protein-coupled EP4 receptor. We hypothesized that EP4 expression on malignant cells would correlate with outcome and patterns of relapse after treatment of LANSCLC stage IIIA (7th edition, N2+). Methods Tissue specimens from 41 pts treated for LANSC at UMGCC were obtained. A tissue microarray was prepared and examined for EP4 expression. Intensity of staining was scored semi-quantitatively as 0–4 in both the nuclear and cytoplasmic compartments by a pathologist blinded to the clinical data. Results EP4 nuclear staining 0–1 vs. 2+ was associated with overall survival, (OS) (44.3 vs. 18 mo; HR=0.41, p=0.024) and numerically superior progression free survival (PFS) (16.4 vs. 10.2 mo, p=0.16). EP4 cytoplasmic staining did not correlate with OS (0–1 vs. 2+, 23.8 vs. 28.8 mo; HR=1.2, p=0.81). Relapse pattern (no relapse or local vs. systemic) did not correlate with EP nuclear staining (p=1.0, X 2 ). Conclusions This is the first clinical study of EP4 expression in lung cancer. There was a significant correlation between OS and nuclear EP4 expression, indicating that this is a potential therapeutic target. Studies with AT-007, a specific inhibitor of EP4, are planned to commence this year.

Background: Presence of cancer stem-like cells (CSCs) is the main obstacle for poor treatment response and mortality in breast cancer patients. Prostaglandin E receptors have been reported to play a role in epithelial-mesenchymal transition (EMT) and metastasis, however, the contribution on cancer stem cell compartment remains unstudied. Methods: Human xenograft breast cancer model was used to study the expression of EP receptors during cancer development. Construction of stable EP2-expression cells was used to study tumorigenesis and characterization of EP2 receptor. Functional role of EP2 receptor on cell proliferation, flow cyometry, invasion and EMT gene expression array were performed in transfected cells. Expression of EP2 receptor was compared in primary tumor tissues by immunostaining and real-time PCR. Results: EP2 receptor was predominantly expressed in animal tissues during cancer development, as well as in human primary tumor tissues. In mouse xenograft model, MB-231-EP2 clone developed a more aggressive tumor with a larger tumor size and showed a significant increase in cancer stem cell marker aldehyde hydrogenase (ALDH1) expression. In vitro study, MB-231-EP2 clone increased colony formation capacity and S-phase entry by the regulation of E-cadherin, TWIST1 and ALDH1. Importantly, we found that Twist1 expression level was higher in breast cancer patients than healthy controls and was associated with ALDH1 expression. Conclusions: These findings implicated that EP2 receptor was crucial to nurture CSC phenotype and promote tumorigenesis in breast cancer. Blocking of EP2 might be a potential therapeutic strategy to improve treatment response for breast cancer patients. Citation Format: Vivian Y Shin, Man T Siu, John C Ho, Isabella Cheuk, Jiawei Chen, Ava Kwong. Prostaglandin E receptor 2 (EP2) regulates breast cancer stem-cell like property and promotes epithelial-mesenchymal transition [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-07-07.

Prostaglandin E2 constitutes a major cyclooxygenase-2-derived prostanoid produced at inflammatory sites. In vitro and in vivo data support its role as a modulator of inflammation. Prostaglandin E2 exerts anti-inflammatory effects by binding to one of its receptors, the prostaglandin E receptor 4 (EP4), thereby modulating macrophage and T lymphocyte functions that participate crucially in innate and adaptive immunity and tissue remodeling and repair. The activation of EP4 suppresses the release of cytokines and chemokines from macrophages and T cells, inhibits the proliferation and the activation of T cells, and induces T-cell apoptosis. Lack of EP4 in bone marrow-derived cells accelerates local inflammation in atherosclerotic and aneurysm lesions and increases the prevalence of aneurysm formation. An EP4 agonist promotes graft survival in allograft cardiac transplantation and dampens tissue damage after myocardial ischemia. Anti-inflammatory actions of EP4 agonism may benefit other inflammatory disorders, including colitis and gastric ulcers. By contrast, EP4 acts as a proinflammatory mediator in encephalomyelitis, skin inflammation, and arthritis by promoting T helper (Th) 1 differentiation and Th17 expansion. Overall, EP4 activation produces powerful anti-inflammatory responses in many experimental diseases, rendering EP4 agonists attractive agents to attenuate syndromes associated with inflammation. Copyright © 2012 by Lippincott Williams & Wilkins., link_to_OA_fulltext

Vascular Biology Surgery is the only therapeutic option currently available for intracranial aneurysms. Aoki et al. delineated a selfamplifying signaling pathway in macrophages that could be pharmacologically targeted to limit the inflammation that initiates intracranial aneurysms and causes them to enlarge. Stimulation of EP2 (prostaglandin E receptor subtype 2) in macrophages increased the levels of COX-2, the enzyme that synthesizes the ligand for EP2, and MCP-1, an attractant for macrophages. Administering an EP2 antagonist to rats prevented the formation and progression of intracranial aneurysms. Sci. Signal. 10, eaah6037 (2017).

The evidence that cyclooxygenase-2 (COX-2) is upregulated and plays an important role in carcinogenesis of gastric cancer has triggered the topic of COX-2 inhibitors as chemopreventive agents for gastric cancer. Studies find that COX-2 inhibitors are associated not only with chemoprophylactic effects, but also with chemotherapeutic potentials in gastric cancer. Both COX-dependent and COX-independent pathways have a role in the anticancer efficiency of COX-2 inhibitors. However, enthusiasm is thwarted by the potential toxicity, that is, gastrointestinal toxicity of nonselective COX-2 inhibitors and cardiovascular risk of selective COX-2 inhibitors. Therefore, more studies are needed to develop new targeted antitumor agents (such as prostaglandin E receptor antagonist) and to define fundamental questions such as optimal treatment regimens, integration of cotherapy, and careful selection of candidates.

Cyclooxygenase-2 is frequently upregulated in epithelial tumors and contributes to poor outcomes in multiple malignancies. The COX-2 product prostaglandin E2 (PGE2) promotes tumor growth and metastasis by acting on a family of four G protein-coupled receptors (EP1-4). Using a novel small molecule EP4 antagonist (RQ-15986) and a syngeneic murine model of metastatic breast cancer, we determined the effect of EP4 blockade on innate immunity and tumor biology. Natural killer (NK)-cell functions are markedly depressed in mice bearing murine mammary tumor 66.1 or 410.4 cells owing to the actions of PGE2 on NK cell EP4 receptors. The EP4 agonist PGE1-OH inhibits NK functions in vitro, and this negative regulation is blocked by RQ-15986. Likewise, the treatment of tumor-bearing mice with RQ-15986 completely protected NK cells from the immunosuppressive effects of the tumor microenvironment in vivo. RQ-15986 also has direct effects on EP4 expressed by tumor cells, inhibiting the PGE2-mediated activation of adenylate cyclase and blocking PGE2-induced tumor cell migration. The pretreatment of tumor cells with a non-cytotoxic concentration of RQ-15986 inhibited lung colonization, a beneficial effect that was lost in mice depleted of NK cells. The oral administration of RQ-15986 inhibited the growth of tumor cells implanted into mammary glands and their spontaneous metastatic colonization to the lungs, resulting in improved survival. Our findings reveal that EP4 antagonism prevents tumor-mediated NK-cell immunosuppression and demonstrates the anti-metastatic activity of a novel EP4 antagonist. These observations support the investigation of EP4 antagonists in clinical trials.

e23249Background: Elevated COX-2 expression has been correlated with inferior outcome in NSCLC. COX-2 catalyzes the transformation of PG to PGE-2. We and others have demonstrated that PGE-2 induces...

Plasma prostaglandin E(2) (PGE(2)) levels are markedly elevated in acute Kawasaki disease (KD). We evaluated the function of the EP receptors in the expression of activated beta(1)-integrin stimulated by PGE(2) in human coronary arterial endothelial cells (HCAEC).We determined the mRNA expression of the PGE(2) receptors, EP receptors (EP(1-4)) in HCAEC by RT-PCR and protein expression by Western blotting. We evaluated the function of the EP receptors in the expression of activated beta(1)-integrin stimulated by PGE(2) in HCAEC, using antagonists and agonists of the EP receptors, by flow cytometry.RT-PCR revealed mRNAs for all four EP receptors in HCAEC. Western blotting demonstrated EP(1), EP(2) and EP(3) expression in HCAEC. The EP(2) and EP(3) agonists enhanced the expression of activated beta(1)-integrin in HCAEC. The potency of the EP(2) agonist was significantly greater than that of the EP(3) agonist. Pretreatment with the EP(1), EP(2) and EP(3) antagonists inhibited the expression of activated beta(1)-integrin induced by PGE(2) in HCAEC. The potency of the EP(2) antagonist was significantly greater than that of the EP(1) and EP(3) antagonists.Our results suggest that PGE(2) mainly induces the activation of beta(1)-integrins via the EP(2) receptor in HCAEC. Our results further suggest that the EP(2) antagonist modulates the inflammatory response during KD vasculitis.

There are eight types and subtypes of receptors for prostanoids including PGD receptor (DP), PGE receptors of EP1, EP2, EP3 and EP4 subtypes, PGF receptor (FP)