In humans, thromboxane (TX)A

Prostacyclin is widely implicated in re-endothelialization and angiogenesis but through unknown mechanisms. Herein the HDL scavenger receptor class B, type 1 adapter PDZK1 was identified as a direct, functional interactant of the human prostacyclin receptor and was found to influence prostacyclin-mediated endothelial migration and in vitro angiogenesis.

The human prostacyclin receptor (hIP) undergoes agonistinduced internalization and subsequent recyclization in slowly recycling endosomes involving its direct physical interaction with Rab11a. may dynamically position ␣-helix 8 in proximity to Rab11a, to regulate agonist-induced intracellular trafficking of the hIP. Moreover, Ala-scanning mutagenesis identified several hydrophobic residues within ␣-helix 8 as necessary for the interaction with Rab11a. Given the diverse membership of the G protein-coupled receptor superfamily, of which many members are also predicted to contain an ␣-helical 8 domain proximal to TM7 and, often, adjacent to palmitoylable cysteine(s), the identification of a functional role for ␣-helix 8, as exemplified as an RBD for the hIP, is likely to have broader significance for certain members of the superfamily.

The prostanoid thromboxane (TX) A2 plays a central role in haemostasis and is increasingly implicated in cancer progression. TXA2 signals through two T Prostanoid receptor (TP) isoforms termed TPα and TPβ, with both encoded by the TBXA2R gene. Despite exhibiting several functional and regulatory differences, the role of the individual TP isoforms in neoplastic diseases is largely unknown.This study evaluated expression of the TPα and TPβ isoforms in tumour microarrays of the benign prostate and different pathological (Gleason) grades of prostate cancer (PCa). Expression of TPβ was significantly increased in PCa relative to benign tissue and strongly correlated with increasing Gleason grade. Furthermore, higher TPβ expression was associated with increased risk of biochemical recurrence (BCR) and significantly shorter disease-free survival time in patients post-surgery. While TPα was more variably expressed than TPβ in PCa, increased/high TPα expression within the tumour also trended toward increased BCR and shorter disease-free survival time. Comparative genomic CpG DNA methylation analysis revealed substantial differences in the extent of methylation of the promoter regions of the TBXA2R that specifically regulate expression of TPα and TPβ, respectively, both in benign prostate and in clinically-derived tissue representative of precursor lesions and progressive stages of PCa. Collectively, TPα and TPβ expression is differentially regulated both in the benign and tumourigenic prostate, and coincides with clinical pathology and altered CpG methylation of the TBXA2R gene. Analysis of TPβ, or a combination of TPα/TPβ, expression levels may have significant clinical potential as a diagnostic biomarker and predictor of PCa disease recurrence.

The prostanoid thromboxane (TX) A 2 is increasingly implicated in neoplastic progression, including prostate cancer (PCa). Mechanistically, we recently identified protein kinase C-related kinase (PRK) 1 as a functional interactant of both the TP` and TPβ isoforms of the human T prostanoid receptor (TP). The interaction with PRK1 was not only essential for TP`/TPβ-induced PCa cell migration but also enabled the TXA 2 -TP axis to induce phosphorylation of histone H3 at Thr11 (H3Thr11), an epigenetic marker both essential for and previously exclusively associated with androgen-induced chromatin remodelling and transcriptional activation. PRK1 is a member of a subfamily of three structurally related kinases comprising PRK1/PKN`, PRK2/PKNγ and PRK3/PKNβ that are widely yet differentially implicated in various cancers. Hence, focusing on the setting of prostate cancer, this study investigated whether TP` and/or TPβ might also complex with PRK2 and PRK3 to regulate their activity and neoplastic responses. While TP` and TPβ were found in immune complexes with PRK1, PRK2 and PRK3 to regulate their activation and signalling, they do so differentially and in a TP agonist-regulated manner dependent on the T-loop activation status of the PRKs but independent of their kinase activity. Furthermore, TXA 2 -mediated neoplastic responses in prostate adenocarcinoma PC-3 cells, including histone H3Thr11 phosphorylation, was found to occur through a PRK1-and PRK2-, but not PRK3-, dependent mechanism. Collectively, these data suggest that TXA 2 acts as both a neoplastic and epigenetic regulator and provides a mechanistic explanation, at least in part, for the prophylactic benefits of Aspirin in reducing the risk of certain cancers.

The prostanoid thromboxane (TX)A signals through the TPα and TPβ isoforms of T Prostanoid receptor (TP) that are transcriptionally regulated by distinct promoters termed Prm1 and Prm3, respectively, within the TBXA2R gene. We recently demonstrated that expression of TPα and TPβ is increased in PCa, differentially correlating with Gleason grade and with altered CpG methylation of the individual Prm1/Prm3 regions within the TBXA2R. The current study sought to localise the sites of CpG methylation within Prm1 and Prm3, and to identify the main transcription factors regulating TPβ expression through Prm3 in the prostate adenocarcinoma PC-3 and LNCaP cell lines. Bisulfite sequencing revealed extensive differences in the pattern and status of CpG methylation of the individual Prm1 and Prm3 regions that regulate TPα and TPβ expression, respectively, within the TBXA2R. More specifically, Prm1 is predominantly hypomethylated while Prm3 is hypermethylated across its entire sequence in PC-3 and LNCaP cells. Furthermore, the tumour suppressors FOXP1 and NKX3.1, strongly implicated in PCa development, were identified as key transcription factors regulating TPβ expression through Prm3 in both PCa cell lines. Specific siRNA-disruption of FOXP1 and NKX3.1 each coincided with up-regulated TPβ protein and mRNA expression, while genetic-reporter and chromatin immunoprecipitation (ChIP) analyses confirmed that both FOXP1 and NKX3.1 bind to cis‑elements within Prm3 to transcriptionally repress TPβ in the PCa lines. Collectively these data identify Prm3/TPβ as a bona fide target of FOXP1 and NKX3.1 regulation, providing a mechanistic basis, at least in part, for the highly significant upregulation of TPβ expression in PCa.

The UCD community has made this article openly available. Please share how this access benefits you. Your story matters! (@ucd_oa) Some rights reserved. For more information, please see the item record link above. TitleTranscriptional regulation of the human thromboxane A2 receptor gene by Wilms' tumor (WT)1 and hypermethylated in cancer (HIC) 1 in prostate and breast cancers Author(s)Keating, Garret L.; Reid, Helen M.; Eivers, Sarah B.; Mulvaney, Eamon P.; Kinsella, B. Therese Publication date 2014-06 Publication informationBiochimica Biophysica Acta (Gene Regulator Mechanisms), 1839 (6): 476-492Publisher Elsevier Item record/more information http://hdl.handle.net/10197/5646 Publisher's statementThis is the author's version of a work that was accepted for publication in Biochimica Biophysica Acta (Gene Regulator Mechanisms) . Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Biochimica Biophysica Acta (Gene Regulator Mechanisms) (VOL1839, ISSUE 6, (2014 Abstract:The prostanoid thomboxane (TX) A 2 plays a central role in hemostasis and is increasingly implicated in neoplastic disease, including prostate and breast cancers. In humans, TXA 2 signals though the TP and TP isoforms of the T prostanoid receptor, two structurally related receptors transcriptionally regulated by distinct promoters, Prm1 and Prm3, respectively, within the TP gene. Focusing on TP, the current study investigated its expression and transcriptional regulation though Prm1 in prostate and breast cancers. Expression of TPα correlated with increasing prostate and breast tissue tumor grade while the TXA 2 mimetic U46619 promoted both proliferation and migration of the respective prostate (PC3) and breast (MCF-7 and MDA-MD-231) derived-carcinoma cell lines.Though 5' deletional and genetic reporter analyses, several functional upstream repressor regions (URRs) were identified within Prm1 in PC3, MCF-7 and MDA-MB-231 cells while site-directed mutagenesis identified the tumor suppressors Wilms' tumor (WT)1 and hypermethylated in cancer (HIC) 1 as the trans-acting factors regulating those repressor regions. Chomatin immunoprecipitation (ChIP) studies confirmed that WT1 binds in vivo to multiple GC-enriched WT1 cis-elements within the URRs of Prm1 in PC3, MCF-7 and MDA-MB-231 cells. Furthermore, ChIP analyses established that HIC1 binds in vivo to the HIC1 (b) cis-element within Prm1 in PC3 and MCF-7 cells but not in the MDA-MB-231 carcinoma line. Collectively, these data establish that WT1 and HIC1, both tumor suppressors implicated in prostate and breast cancers, transcriptionally repress TPα expression and thereby provide a strong genetic basis for understanding the role of TXA 2 in the progression of certain human cancers. Highlights: Upregulation of the thomboxane receptor (th...

Background: NTP42 is a novel antagonist of the thromboxane prostanoid receptor (TP), currently in development for the treatment of pulmonary arterial hypertension (PAH). PAH is a devastating disease with multiple pathophysiological hallmarks including excessive pulmonary vasoconstriction, vascular remodelling, inflammation, fibrosis, in situ thrombosis and right ventricular hypertrophy. Signalling through the TP, thromboxane (TX) A 2 is a potent vasoconstrictor and mediator of platelet aggregation. It is also a pro-mitogenic, pro-inflammatory and pro-fibrotic agent. Moreover, the TP also mediates the adverse actions of the isoprostane 8-iso-prostaglandin F 2α , a free-radical-derived product of arachidonic acid produced in abundance during oxidative injury. Mechanistically, TP antagonists should treat most of the hallmarks of PAH, including inhibiting the excessive vasoconstriction and pulmonary artery remodelling, in situ thrombosis, inflammation and fibrosis. This study aimed to investigate the efficacy of NTP42 in the monocrotaline (MCT)-induced PAH rat model, alongside current standard-of-care drugs. Methods: PAH was induced by subcutaneous injection of 60 mg/kg MCT in male Wistar-Kyoto rats. Animals were assigned into groups: 1. 'No MCT'; 2. 'MCT Only'; 3. MCT + NTP42 (0.25 mg/kg BID); 4. MCT + Sildenafil (50 mg/kg BID), and 5. MCT + Selexipag (1 mg/kg BID), where 28-day drug treatment was initiated within 24 h post-MCT. Results: From haemodynamic assessments, NTP42 reduced the MCT-induced PAH, including mean pulmonary arterial pressure (mPAP) and right systolic ventricular pressure (RSVP), being at least comparable to the standardof-care drugs Sildenafil or Selexipag in bringing about these effects. Moreover, NTP42 was superior to Sildenafil and Selexipag in significantly reducing pulmonary vascular remodelling, inflammatory mast cell infiltration and fibrosis in MCT-treated animals.