Gene Summary

Gene:PWAR1; Prader Willi/Angelman region RNA 1
Aliases: PAR1, PAR-1, D15S227E
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Source:NCBIAccessed: 11 March, 2017

Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 11 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

Tag cloud generated 11 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (3)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: PWAR1 (cancer-related)

Baker E, Jacobs C, Martinie J, et al.
Mixed Hepatocellular Carcinoma, Neuroendocrine Carcinoma of the Liver.
Am Surg. 2016; 82(11):1121-1125 [PubMed] Related Publications
We present the case of a 76-year-old male found to have a large tumor involving the left lateral lobe of the liver, presumed to be hepatocellular carcinoma (HCC). After resection, pathologic features demonstrated both high-grade HCC and high-grade neuroendocrine carcinoma (NEC). Areas of NEC stained strongly for synaptophysin, which was not present in HCC component. The HCC component stained strongly for Hep-Par 1, which was not present in the NEC component. The patient underwent genetic analysis for biomarkers common to both tumor cell types. Both tumor components contained gene mutations in CTNNB1 gene (S33F located in exon 3). They also shared mutations in PD-1, PGP, and SMO. Mixed HCC/NEC tumors have been rarely reported in the literature with generally poor outcomes. This patient has been referred for adjuvant platinum-based chemotherapy; genetic biomarker analysis may provide some insight to guide targeted chemotherapy.

Wang Y, Liu J, Ying X, et al.
Twist-mediated Epithelial-mesenchymal Transition Promotes Breast Tumor Cell Invasion via Inhibition of Hippo Pathway.
Sci Rep. 2016; 6:24606 [PubMed] Free Access to Full Article Related Publications
Twist is a key transcription factor for Epithelial-mesenchymal transition (EMT), which is a cellular de-differentiation program that promotes invasion and metastasis, confers tumor cells with cancer stem cell (CSC)-like characteristics, and increases therapeutic resistance. However, the mechanisms that facilitate the functions of Twist remain unclear. Here we report that Twist overexpression increased expression of PAR1, an upstream regulator of the Hippo pathway; PAR1 promotes invasion, migration, and CSC-like properties in breast cancer by activating the transcriptional co-activator TAZ. Our study indicates that Hippo pathway inhibition is required for the increased migratory and invasiveness ability of breast cancer cells in Twist-mediated EMT.

D'Asti E, Rak J
Biological basis of personalized anticoagulation in cancer: oncogene and oncomir networks as putative regulators of coagulopathy.
Thromb Res. 2016; 140 Suppl 1:S37-43 [PubMed] Related Publications
Activation of stromal response pathways in cancer is increasingly viewed as both a local and systemic extension of molecular alterations driving malignant transformation. Rather than reflecting passive and unspecific responses to anatomical abnormalities, the coagulation system is a target of oncogenic deregulation, impacting the role of clotting and fibrinolytic proteins, and integrating hemostasis, inflammation, angiogenesis and cellular growth effects in cancer. These processes signify, but do not depend on, the clinically manifest coagulopathy and thrombosis. In this regard, the role of driver mutations affecting oncoprotein coding genes such as RAS, EGFR or MET and tumour suppressors (PTEN, TP53) are well described as regulators of tissue factor (TF), protease activated receptors (PAR-1/2) and ectopic coagulation factors (FVII). Indeed, in both adult and pediatric brain tumours the expression patterns of coagulation and angiogenesis regulators (coagulome and angiome, respectively) reflect the molecular subtypes of the underlying diseases (glioblastoma or medulloblastoma) as defined by their oncogenic classifiers and clinical course. This emerging understanding is still poorly established in relation to the transforming effects of non-coding genes, including those responsible for the expression of microRNA (miR). Indeed, several miRs have been recently found to regulate TF and other effectors. We recently documented that in the context of the aggressive embryonal tumour with multilayered rosettes (ETMR) the oncogenic driver miR (miR-520g) suppresses the expression of TF and correlates with hypocoagulant tumour characteristics. Unlike in adult cancers, the growth of pediatric embryonal brain tumour cells as spheres (to maintain stem cell properties) results in upregulation of miR-520g and downregulation of TF expression and activity. We postulate that oncogenic protein and miR coding genes form alternative pathways of coagulation system regulation in different tumour settings, a property necessitating more personalised and biologically-based approaches to anticoagulation.

Amador MA, Cavalcante GC, Santos NP, et al.
Distribution of allelic and genotypic frequencies of IL1A, IL4, NFKB1 and PAR1 variants in Native American, African, European and Brazilian populations.
BMC Res Notes. 2016; 9:101 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The inflammatory response plays a key role at different stages of cancer development. Allelic variants of the interleukin 1A (IL1A), interleukin 4 (IL4), nuclear factor kappa B1 (NFKB1) and protease-activated receptor 1 (PAR1) genes may influence not only the inflammatory response but also susceptibility to cancer development. Among major ethnic or continental groups, these polymorphic variants present different allelic frequencies. In admixed populations, such as the Brazilian population, data on distribution of these polymorphisms are limited. Here, we collected samples of cancer-free individuals from the north, northeast, midwest, south and southeast regions of Brazil and from the three main groups that gave rise to the Brazilian population: Native Americans from the Brazilian Amazon, Africans and Europeans. We describe the allelic distributions of four IL1A (rs3783553), IL4 (rs79071878), NFKB1 (rs28362491) and PAR1 (rs11267092) gene polymorphisms, which the literature describes as polymorphisms with a risk of cancer or worse prognosis for cancer.
RESULTS: The genotypic distribution of the four polymorphisms was statistically distinct between Native Americans, Africans and Europeans. For the allelic frequency of these polymorphisms, the Native American population was the most distinct among the three parental populations, and it included the greatest number of alleles with a risk of cancer or worse prognosis for cancer. The PAR1 gene polymorphism allelic distribution was similar among all Brazilian regions. For the other three markers, the northern region population was statistically distinct from other Brazilian region populations.
CONCLUSION: The IL1A, IL4, NFKB1 and PAR1 gene polymorphism allelic distributions are homogeneous among the regional Brazilian populations, except for the northern region, which significantly differs from the other four Brazilian regions. Among the parental populations, the Native American population exhibited a higher incidence of alleles with risk of cancer or worse prognosis for cancer, which can indicate greater susceptibility to this disease. These genetic data may be useful for future studies on the association between these polymorphisms and cancer in the investigated populations.

Kancharla A, Maoz M, Jaber M, et al.
PH motifs in PAR1&2 endow breast cancer growth.
Nat Commun. 2015; 6:8853 [PubMed] Free Access to Full Article Related Publications
Although emerging roles of protease-activated receptor1&2 (PAR1&2) in cancer are recognized, their underlying signalling events are poorly understood. Here we show signal-binding motifs in PAR1&2 that are critical for breast cancer growth. This occurs via the association of the pleckstrin homology (PH) domain with Akt/PKB as a key signalling event of PARs. Other PH-domain signal-proteins such as Etk/Bmx and Vav3 also associate with PAR1 and PAR2 through their PH domains. PAR1 and PAR2 bind with priority to Etk/Bmx. A point mutation in PAR2, H349A, but not in R352A, abrogates PH-protein association and is sufficient to markedly reduce PAR2-instigated breast tumour growth in vivo and placental extravillous trophoblast (EVT) invasion in vitro. Similarly, the PAR1 mutant hPar1-7A, which is unable to bind the PH domain, reduces mammary tumours and EVT invasion, endowing these motifs with physiological significance and underscoring the importance of these previously unknown PAR1 and PAR2 PH-domain-binding motifs in both pathological and physiological invasion processes.

Hidayat AN, Aki-Yalcin E, Beksac M, et al.
Insight into human protease activated receptor-1 as anticancer target by molecular modelling.
SAR QSAR Environ Res. 2015; 26(10):795-807 [PubMed] Related Publications
Protease-activated receptor 1 (PAR1) has been established as a promising target in many diseases, including various cancers. Strong evidence also suggests its role in metastasis. It is proved experimentally that PAR1 can induce numerous cell phenotypes, i.e. proliferation and differentiation. A strong link between PAR1 gene overexpression and high levels of ß-catenin was suggested by a study of the PAR1-Gα(13)-DVL axis in ß-catenin stabilization in cancers. An in vitro study was carried out to analyze PAR1 expression by flow cytometry on CD38+138+ plasma cells obtained from patients either at diagnosis (n: 46) (newly diagnosed multiple myeloma (NDMM)) or at relapse (n: 45) (relapsed/refractory multiple myeloma (RRMM)) and compared with the controls. Our previously synthesized benzoxazole (XT2B) and benzamide (XT5) derivatives were tested with in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, which revealed significant inhibitory activity on PAR1. We provide docking studies using Autodock Vina of these newly tested compounds to compare with the known PAR1 inhibitors in order to examine the binding mechanisms. In addition, the docking results are validated using HYDE binding assessment and a neural network (NN) scoring function.

Burns KE, Thévenin D
Down-regulation of PAR1 activity with a pHLIP-based allosteric antagonist induces cancer cell death.
Biochem J. 2015; 472(3):287-95 [PubMed] Free Access to Full Article Related Publications
Even though abnormal expression of G protein-coupled receptors (GPCRs) and of their ligands is observed in many cancer cells of various origins, only a few anti-cancer compounds directly act on their signalling. One promising approach to modulate their activity consists of targeting the receptor cytoplasmic surfaces interacting with the associated G-proteins using peptides mimicking the intracellular loops of the receptor. Thus, to be fully effective, the peptide mimics must be selectively targeted to the tumour while sparing healthy tissues, translocated across the cell membrane and stay anchored to the cytoplasmic leaflet of the plasma membrane. In the present study, we introduce a novel way to selectively target and inhibit the activity of a GPCR in cancer cells under acidic conditions, such as those found in solid tumours. We find that the conjugation of a peptide fragment derived from the third intracellular loop (i3) of the protease-activated receptor 1 (PAR1) to a peptide that can selectively target tumours solely based on their acidity [pH(Low) Insertion Peptide (pHLIP)], produces a construct capable of effectively down-regulating PAR1 activity in a concentration- and pH-dependent manner and of inducing a potent cytotoxic effect in a panel of cancer cells that is proportional to the relative level of receptor expression at the cell surface. This strategy not only allows for a more selective targeting and specific intracellular delivery than current approaches, but also offers new possibilities for developing novel anti-cancer drugs targeting GPCRs.

Barbosa TC, Terra-Granado E, Quezado Magalhães IM, et al.
Frequency of copy number abnormalities in common genes associated with B-cell precursor acute lymphoblastic leukemia cytogenetic subtypes in Brazilian children.
Cancer Genet. 2015; 208(10):492-501 [PubMed] Related Publications
Copy number alterations (CNAs) in genes committed to B-cell precursors have been associated with poor survival in subgroups of patients with B-cell precursor acute lymphoblastic leukemia (BCP-ALL). We investigated submicroscopic alterations in a series of 274 Brazilian children with BCP-ALL by multiplex ligation-dependent probe amplification and evaluated their correlation with clinical and laboratory features. The relevance of overlapping CNA abnormalities was also explored. Deletions/amplifications in at least one gene were identified in 83% of the total series. In children older than 2 years, there was a predominance of CNAs involving deletions in IKZF1, CDKN2A, and CDKN2B, whereas the pseudoautosomal region 1 (PAR1) had deletions that were found more frequently in infants (P <0.05). Based on the cytogenetic subgroups, favorable cytogenetic subgroups showed more deletions than other subgroups that occurred simultaneously, specifically ETV6 deletions (P <0.05). TCF3-PBX1 was frequently deleted in RB1, and an absence of deletions was observed in IKZF1 and genes localized to the PAR1 region. The results corroborate with previous genome-wide studies and aggregate new markers for risk stratification of BCP-ALL in Brazil.

Yang E, Cisowski J, Nguyen N, et al.
Dysregulated protease activated receptor 1 (PAR1) promotes metastatic phenotype in breast cancer through HMGA2.
Oncogene. 2016; 35(12):1529-40 [PubMed] Related Publications
As the majority of patients with basal-like breast carcinoma present with invasive, metastatic disease that do not respond to available therapies, it is essential to identify new therapeutic targets that impact invasion and metastasis. Protease-activated receptor 1 (PAR1), a G-protein coupled receptor has been shown to act as an oncogene, but underlying mechanisms are not well understood. Here, we show that ectopic expression of functionally active PAR1 in MCF-7 cells induced a hormone-refractory, invasive phenotype representative of advanced basal-like breast carcinoma that readily formed metastatic lesions in lungs of mice. PAR1 was found to globally upregulate mesenchymal markers, including vimentin, a direct target of PAR1, and downregulate the epithelial markers including E-cadherin, as well as estrogen receptor. In contrast, non-signaling PAR1 mutant receptor did not lead to an invasive, hormone refractory phenotype. PAR1 expression increased spheroid formation and the level of stemness markers and self-renewal capacity in human breast cancer cells. We identified HMGA2 (high mobility group A2) as an important regulator of PAR1-mediated invasion. Inhibition of PAR1 signaling suppresses HMGA2-driven invasion in breast cancer cells. HMGA2 gene and protein are highly expressed in metastatic breast cancer cells. Overall, our results show that PAR1/HMGA2 pathway may present a novel therapeutic target.

d'Audigier C, Cochain C, Rossi E, et al.
Thrombin receptor PAR-1 activation on endothelial progenitor cells enhances chemotaxis-associated genes expression and leukocyte recruitment by a COX-2-dependent mechanism.
Angiogenesis. 2015; 18(3):347-59 [PubMed] Related Publications
BACKGROUND: Endothelial colony forming cells (ECFC) represent a subpopulation of endothelial progenitor cells involved in endothelial repair. The activation of procoagulant mechanisms associated with the vascular wall's inflammatory responses to injury plays a crucial role in the induction and progression of atherosclerosis. However, little is known about ECFC proinflammatory potential.
AIMS: To explore the role of the thrombin receptor PAR-1 proinflammatory effects on ECFC chemotaxis/recruitment capacity.
METHODS AND RESULTS: The expression of 30 genes known to be associated with inflammation and chemotaxis was quantified in ECFC by real-time qPCR. PAR-1 activation with the SFLLRN peptide (PAR-1-ap) resulted in a significant increase in nine chemotaxis-associated genes expression, including CCL2 and CCL3 whose receptors are present on ECFC. Furthermore, COX-2 expression was found to be dramatically up-regulated consequently to PAR-1 activation. COX-2 silencing with the specific COX-2-siRNA also triggered down-regulation of the nine target genes. Conditioned media (c.m.) from control-siRNA- and COX-2-siRNA-transfected ECFC, stimulated or not with PAR-1-ap, were produced and tested on ECFC capacity to recruit leukocytes in vitro as well in the muscle of ischemic hindlimb in a preclinical model. The capacity of the c.m. from ECFC stimulated with PAR-1-ap to recruit leukocytes was abrogated when COX-2 gene expression was silenced in vitro (in terms of U937 cells migration and adhesion to endothelial cells) as well as in vivo. Finally, the postnatal vasculogenic stem cell derived from infantile hemangioma tumor (HemSC) incubated with PAR-1-ap increased leukocyte recruitment in Matrigel(®) implant.
CONCLUSIONS: PAR-1 activation in ECFC increases chemotactic gene expression and leukocyte recruitment at ischemic sites through a COX-2-dependent mechanism.

Olsson L, Ivanov Öfverholm I, Norén-Nyström U, et al.
The clinical impact of IKZF1 deletions in paediatric B-cell precursor acute lymphoblastic leukaemia is independent of minimal residual disease stratification in Nordic Society for Paediatric Haematology and Oncology treatment protocols used between 1992 and 2013.
Br J Haematol. 2015; 170(6):847-58 [PubMed] Related Publications
Paediatric B-cell precursor acute lymphoblastic leukaemias (BCP ALL) with IKZF1 deletions (∆IKZF1) are associated with a poor outcome. However, there are conflicting data as to whether ∆IKZF1 is an independent risk factor if minimal residual disease (MRD) and other copy number alterations also are taken into account. We investigated 334 paediatric BCP ALL, diagnosed 1992-2013 and treated according to Nordic Society for Paediatric Haematology and Oncology ALL protocols, with known IKZF1 status based on either single nucleotide polymorphism array (N = 218) or multiplex ligation-dependent probe amplification (N = 116) analyses. ∆IKZF1, found in 15%, was associated with inferior 10-year probabilities of event-free (60% vs. 83%; P < 0·001) and overall survival (pOS; 73% vs. 89%; P = 0·001). Adjusting for known risk factors, including white blood cell (WBC) count and MRD, ∆IKZF1 was the strongest independent factor for relapse and death. ∆IKZF1 was present in 27% of cases with non-informative cytogenetics ('BCP-other') and a poor 10-year pOS was particularly pronounced in this group (58% vs. 90%; P < 0·001). Importantly, neither MRD nor WBC count predicted events in the ∆IKZF1-positive cases. Co-occurrence of pseudoautosomal region 1 (PAR1) deletions in Xp22.33/Yp11.32 (P2RY8-CRLF2) and ∆IKZF1 increased the risk of relapse (75% vs. 30% for cases with only ∆IKZF1; P = 0·045), indicating that BCP-other ALL with both P2RY8-CRLF2 and ∆IKZF1 constitutes a particularly high-risk group.

Olsson L, Albitar F, Castor A, et al.
Cooperative genetic changes in pediatric B-cell precursor acute lymphoblastic leukemia with deletions or mutations of IKZF1.
Genes Chromosomes Cancer. 2015; 54(5):315-25 [PubMed] Related Publications
In contrast to IKZF1 deletions (ΔIKZF1), IKZF1 sequence mutations (mutIKZF1) have been reported to be rare in B-cell precursor acute lymphoblastic leukemia and their clinical implications are unknown. We performed targeted deep sequencing of all exons of IKZF1 in 140 pediatric cases, eight (5.7%) of which harbored a mutIKZF1. The probabilities of relapse (pRel) and event-free survival (pEFS) did not differ between cases with or without mutIKZF1, whereas pEFS was decreased and pRel increased in ΔIKZF1-positive case. Coexisting microdeletions, mutations (FLT3, JAK2, SH2B3, and SPRED1), and rearrangements (ABL1, CRLF2, JAK2, and PDGFRB) in 35 ΔIKZF1 and/or mutIKZF1-positive cases were ascertained using fluorescence in situ hybridization, single nucleotide polymorphism array, Sanger, and targeted deep sequencing analyses. The overall frequencies of copy number alterations did not differ between cases with our without ΔIKZF1/mutIKZF1. Deletions of HIST1, SH2B3, and the pseudoautosomal region (PAR1), associated with deregulation of CRLF2, were more common in ΔIKZF1-positive cases, whereas PAR1 deletions and JAK2 mutations were overrepresented in the combined ΔIKZF1/mutIKZF1 group. There was no significant impact on pRel of the deletions in ΔIKZF1-positive cases or of JAK2 mutations in cases with ΔIKZF1/mutIKZF1. In contrast, the pRel was higher (P = 0.005) in ΔIKZF1/mutIKZF1-positive cases with PAR1 deletions.

Lim HC, Multhaupt HA, Couchman JR
Cell surface heparan sulfate proteoglycans control adhesion and invasion of breast carcinoma cells.
Mol Cancer. 2015; 14:15 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Cell surface proteoglycans interact with numerous regulators of cell behavior through their glycosaminoglycan chains. The syndecan family of transmembrane proteoglycans are virtually ubiquitous cell surface receptors that are implicated in the progression of some tumors, including breast carcinoma. This may derive from their regulation of cell adhesion, but roles for specific syndecans are unresolved.
METHODS: The MDA-MB231 human breast carcinoma cell line was exposed to exogenous glycosaminoglycans and changes in cell behavior monitored by western blotting, immunocytochemistry, invasion and collagen degradation assays. Selected receptors including PAR-1 and syndecans were depleted by siRNA treatments to assess cell morphology and behavior. Immunohistochemistry for syndecan-2 and its interacting partner, caveolin-2 was performed on human breast tumor tissue arrays. Two-tailed paired t-test and one-way ANOVA with Tukey's post-hoc test were used in the analysis of data.
RESULTS: MDA-MB231 cells were shown to be highly sensitive to exogenous heparan sulfate or heparin, promoting increased spreading, focal adhesion and adherens junction formation with concomitantly reduced invasion and matrix degradation. The molecular basis for this effect was revealed to have two components. First, thrombin inhibition contributed to enhanced cell adhesion and reduced invasion. Second, a specific loss of cell surface syndecan-2 was noted. The ensuing junction formation was dependent on syndecan-4, whose role in promoting actin cytoskeletal organization is known. Syndecan-2 interacts with, and may regulate, caveolin-2. Depletion of either molecule had the same adhesion-promoting influence, along with reduced invasion, confirming a role for this complex in maintaining the invasive phenotype of mammary carcinoma cells. Finally, both syndecan-2 and caveolin-2 were upregulated in tissue arrays from breast cancer patients compared to normal mammary tissue. Moreover their expression levels were correlated in triple negative breast cancers.
CONCLUSION: Cell surface proteoglycans, notably syndecan-2, may be important regulators of breast carcinoma progression through regulation of cytoskeleton, cell adhesion and invasion.

Aissaoui H, Prévost C, Boucharaba A, et al.
MDA-9/syntenin is essential for factor VIIa-induced signaling, migration, and metastasis in melanoma cells.
J Biol Chem. 2015; 290(6):3333-48 [PubMed] Free Access to Full Article Related Publications
Melanoma differentiation associated gene-9 (MDA-9), also known as syntenin, is a novel gene that positively regulates cancer cell motility, invasion, and metastasis through distinct biochemical and signaling pathways, but how MDA-9/syntenin is regulated in response to signals with the extracellular environment and promotes tumor progression is unclear. We now demonstrate that MDA-9/syntenin is dramatically up-regulated by a combination of rFVIIa and factor F(X) in malignant melanoma. Induction of MDA-9/syntenin in melanoma was found to occur in a thrombin-independent signaling pathway and involves the PAR-1/c-Src/Rho GTPases Rac1 and Cdc42/c-Jun N-terminal kinase axis resulting in the activation of paxillin, NF-κB, and matrix metalloproteinase-2 (MMP-2). MDA-9/syntenin physically interacts with c-Src through its PDZ binding motif following stimulation of melanoma cells with rFVIIa and FX. We also document that induction of this signaling pathway is required for TF·FVIIa·Xa-induced cell migration, invasion, and metastasis by melanoma cells. The present finding uncovers a novel role of MDA-9/syntenin as an important TF·FVIIa·Xa/PAR-1-regulated gene that initiates a signaling circuit essential for cell motility and invasion of metastatic melanoma. In these contexts, targeting TF·FVIIa·Xa and its relevant downstream targets such as MDA-9/syntenin, may represent a novel therapeutic strategy to control the evolution of neoplastic cells.

Mußbach F, Henklein P, Westermann M, et al.
Proteinase-activated receptor 1- and 4-promoted migration of Hep3B hepatocellular carcinoma cells depends on ROS formation and RTK transactivation.
J Cancer Res Clin Oncol. 2015; 141(5):813-25 [PubMed] Related Publications
PURPOSE: There is growing evidence for a role of proteinase-activated receptors (PARs), a subfamily of G protein-coupled receptors, in cancer. We have previously shown that PAR1 and PAR4 are able to promote the migration of hepatocellular carcinoma (HCC) cells suggesting a function in HCC progression. In this study, we assessed the underlying signalling mechanisms.
METHODS: Using Hep3B liver carcinoma cells, RTK activation was assessed by Western blot employing phospho-RTK specific antibodies, ROS level were estimated by H2DCF-DA using confocal laser scanning microscopy, and measurement of PTP activity was performed in cell lysates using 6,8-difluoro-4-methylumbelliferyl phosphate (DiFMUP) as a substrate.
RESULTS: Thrombin, the PAR1 selective agonist peptide TFLLRN-NH2 (PAR1-AP), and the PAR4 selective agonist peptide, AYPGKF-NH2 (PAR4-AP), induced a significant increase in Hep3B cell migration that could be blocked by inhibitors targeting formation of reactive oxygen species (ROS), or activation of hepatocyte-growth factor receptor (Met), or platelet-derived growth factor receptor (PDGFR), respectively. The involvement of these intracellular effectors in PAR1/4-initiated migratory signalling was further supported by the findings that individual stimulation of Hep3B cells with the PAR1-AP and the PAR4-AP induced an increase in ROS production and the transactivation of Met and PDGFR. In addition, PAR1- and PAR4-mediated inhibition of total PTP activity and specifically PTP1B. ROS inhibition by N-acetyl-L-cysteine prevented the inhibition of PTP1B phosphatase activity induced by PAR1-AP and the PAR4-AP, but had no effect on PAR1/4-mediated activation of Met and PDGFR in Hep3B cells.
CONCLUSIONS: Collectively, our data indicate that PAR1 and PAR4 activate common promigratory signalling pathways in Hep3B liver carcinoma cells including activation of the receptor tyrosine kinases Met and PDGFR, the formation of ROS and the inactivation of PTP1B. However, PAR1/4-triggered Met and PDGFR transactivation seem to be mediated independently from the ROS-PTP1B signalling module.

Fazzini A, D'Antongiovanni V, Giusti L, et al.
Altered protease-activated receptor-1 expression and signaling in a malignant pleural mesothelioma cell line, NCI-H28, with homozygous deletion of the β-catenin gene.
PLoS One. 2014; 9(11):e111550 [PubMed] Free Access to Full Article Related Publications
Protease activated receptors (PARs) are G-protein coupled receptors that are activated by an unique proteolytic mechanism. These receptors play crucial roles in hemostasis and thrombosis but also in inflammation and vascular development. PARs have also been implicated in tumor progression, invasion and metastasis. In this study, we investigated expression and signaling of PAR1 in nonmalignant pleural mesothelial (Met-5A) and malignant pleural mesothelioma (NCI-H28) cells. We found that the expression level of PAR1 was markedly higher in NCI-H28 cells compared to Met-5A and human primary mesothelial cells. Other three malignant pleural mesothelioma cell lines, i.e. REN, Ist-Mes2, and Mero-14, did not show any significant PAR1 over-expression compared to Met-5A cell line. Thrombin and PAR1 activating peptides enhanced Met-5A and NCI-H28 cell proliferation but in NCI-H28 cells higher thrombin concentrations were required to obtain the same proliferation increase. Similarly, thrombin caused extracellular signal-regulated kinase 1/2 activation in both cell lines but NCI-H28 cells responded at higher agonist concentrations. We also determined that PAR1 signaling through Gq and G12/13 proteins is severely altered in NCI-H28 cells compared to Met-5A cells. On the contrary, PAR1 signaling through Gi proteins was persistently maintained in NCI-H28 cells. Furthermore, we demonstrated a reduction of cell surface PAR1 expression in NCI-H28 and malignant pleural mesothelioma REN cells. Thus, our results provide evidences for dysfunctional PAR1 signaling in NCI-H28 cells together with reduced plasma membrane localization. The role of PAR1 in mesothelioma progression is just emerging and our observations can promote further investigations focused on this G-protein coupled receptor.

Chan KT, Asokan SB, King SJ, et al.
LKB1 loss in melanoma disrupts directional migration toward extracellular matrix cues.
J Cell Biol. 2014; 207(2):299-315 [PubMed] Free Access to Full Article Related Publications
Somatic inactivation of the serine/threonine kinase gene STK11/LKB1/PAR-4 occurs in a variety of cancers, including ∼10% of melanoma. However, how the loss of LKB1 activity facilitates melanoma invasion and metastasis remains poorly understood. In LKB1-null cells derived from an autochthonous murine model of melanoma with activated Kras and Lkb1 loss and matched reconstituted controls, we have investigated the mechanism by which LKB1 loss increases melanoma invasive motility. Using a microfluidic gradient chamber system and time-lapse microscopy, in this paper, we uncover a new function for LKB1 as a directional migration sensor of gradients of extracellular matrix (haptotaxis) but not soluble growth factor cues (chemotaxis). Systematic perturbation of known LKB1 effectors demonstrated that this response does not require canonical adenosine monophosphate-activated protein kinase (AMPK) activity but instead requires the activity of the AMPK-related microtubule affinity-regulating kinase (MARK)/PAR-1 family kinases. Inhibition of the LKB1-MARK pathway facilitated invasive motility, suggesting that loss of the ability to sense inhibitory matrix cues may promote melanoma invasion.

Li SM, Jiang P, Xiang Y, et al.
Protease-activated receptor (PAR)1, PAR2 and PAR4 expressions in esophageal squamous cell carcinoma.
Dongwuxue Yanjiu. 2014; 35(5):420-5 [PubMed] Free Access to Full Article Related Publications
Here, we used reverse transcription-PCR (RT-PCR) and western blot to detect protease-activated receptor (PAR) 1, PAR 2 and PAR 4 expression in cancer tissues and cell lines of esophageal squamous cell carcinoma, and investigated the co-relationship between PAR expression and clinic-pathological data for esophageal cancer. The methylation of PAR4 gene promoter involved in esophageal carcinoma was also analyzed. By comparing the mRNA expressions of normal esophageal tissue and human esophageal epithelial cells (HEEpiC), we found that among the 28 cases of esophageal squamous cell carcinoma, PAR1 (60%) and PAR2 (71%) were elevated in 17 and 20 cases, respectively, and PAR4 (68%) expression was lowered in 19 cases. Whereas, in human esophageal squamous cells (TE-1 and TE-10), PAR1 and PAR2 expression was increased but PAR4 was decreased. Combined with clinical data, the expression of PAR1 in poorly differentiated (P=0.016) and middle and lower parts of the esophagus (P=0.016) was higher; expression of PAR4 in poorly differentiated carcinoma was lower (P=0.049). Regarding TE-1 and TE-10 protein expression, we found that in randomized esophageal carcinoma, PAR1 (P=0.027) and PAR2 (P=0.039) expressions were increased, but lowered for PAR4 (P=0.0001). In HEEpiC, TE-1, TE-10, esophageal and normal esophagus tissue samples (case No. 7), the frequency of methylation at the 19 CpG loci of PAR4 was 35.4%, 95.2%, 83.8%, 62.6% and 48.2%, respectively. Our results indicate that the expression of PAR1 and PAR2 in esophageal squamous cell carcinoma is increased but PAR4 is decreased. Hypermethylation of the promoter of the PAR4 gene may contribute to reduced expression of PAR4 in esophageal squamous cell carcinoma.

Nicastri A, Gaspari M, Sacco R, et al.
N-glycoprotein analysis discovers new up-regulated glycoproteins in colorectal cancer tissue.
J Proteome Res. 2014; 13(11):4932-41 [PubMed] Related Publications
Colorectal cancer is one of the leading causes of death due to cancer worldwide. Therefore, the identification of high-specificity and -sensitivity biomarkers for the early detection of colorectal cancer is urgently needed. Post-translational modifications, such as glycosylation, are known to play an important role in cancer progression. In the present work, we used a quantitative proteomic technique based on (18)O stable isotope labeling to identify differentially expressed N-linked glycoproteins in colorectal cancer tissue samples compared with healthy colorectal tissue from 19 patients undergoing colorectal cancer surgery. We identified 54 up-regulated glycoproteins in colorectal cancer samples, therefore potentially involved in the biological processes of tumorigenesis. In particular, nine of these (PLOD2, DPEP1, SE1L1, CD82, PAR1, PLOD3, S12A2, LAMP3, OLFM4) were found to be up-regulated in the great majority of the cohort, and, interestingly, the association with colorectal cancer of four (PLOD2, S12A2, PLOD3, CD82) has not been hitherto described.

Otsuki T, Fujimoto D, Hirono Y, et al.
Thrombin conducts epithelial‑mesenchymal transition via protease‑activated receptor‑1 in human gastric cancer.
Int J Oncol. 2014; 45(6):2287-94 [PubMed] Related Publications
Epithelial-mesenchymal transition (EMT) is thought to be a key step for cancer metastasis. Using an immunohistochemical approach with gastric carcinoma tissue, we found the expression of protease-activated receptor-1 (PAR1), along with a metalloproteinase known to activate PAR1, were associated with poorer prognosis, compared with expression-negative tumors, and activated PAR1 promotes gastric cancer cell invasion and proliferation in vivo. In this study we observed EMT induction by the PAR1 agonist α-thrombin, in human gastric cell lines stably expressing PAR1. We investigated α-thrombin-induced changes in the cell forms of pcDNA3.1-MKN45 (MKN45/Mock), pcDNA3.1‑PAR1 transfected MKN45 (MKN45/PAR1), and MKN74. Expression levels of epithelial and mesenchymal markers as well as the distribution of transcriptional factors of E-cadherin in the cytoplasm and nucleus were also noted in these cell lines. We observed α-thrombin-induced morphological changes in MKN45/PAR1 and MKN74 cells. Western blotting and immunohistochemistry of these cells indicated a fall in the expression level of E-cadherin and an increase in fibronectin expression after 48 h. PAR1 activation also induced significant increases in nuclear levels of the Snail which is a repressor of E-cadherin gene expression. We found EMT in gastric cancer cell lines that underwent α-thrombin-induced PAR1 activation.

D'Asti E, Kool M, Pfister SM, Rak J
Coagulation and angiogenic gene expression profiles are defined by molecular subgroups of medulloblastoma: evidence for growth factor-thrombin cross-talk.
J Thromb Haemost. 2014; 12(11):1838-49 [PubMed] Related Publications
BACKGROUND: The coagulation system becomes activated during progression and therapy of high-grade brain tumors. Triggering tissue factor (F3/TF) and thrombin receptors (F2R/PAR-1) may influence the vascular tumor microenvironment and angiogenesis irrespective of clinically apparent thrombosis. These processes are poorly understood in medulloblastoma (MB), in which diverse oncogenic pathways define at least four molecular disease subtypes (WNT, SHH, Group 3 and Group 4). We asked whether there is a link between molecular subtype and the network of vascular regulators expressed in MB.
METHODS: Using R2 microarray analysis and visualization platform, we mined MB datasets for differential expression of vascular (coagulation and angiogenesis)-related genes, and explored their link to known oncogenic drivers. We evaluated the functional significance of this link in DAOY cells in vitro following growth factor and thrombin stimulation.
RESULTS: The coagulome and angiome differ across MB subtypes. F3/TF and F2R/PAR-1 mRNA expression are upregulated in SHH tumors and correlate with higher levels of hepatocyte growth factor receptor (MET). Cultured DAOY (MB) cells exhibit an up-regulation of F3/TF and F2R/PAR-1 following combined SHH and MET ligand (HGF) treatment. These factors cooperate with thrombin, impacting the profile of vascular regulators, including interleukin 1β (IL1B) and chondromodulin 1 (LECT1).
CONCLUSIONS: Coagulation pathway sensors (F3/TF, F2R/PAR-1) are expressed in MB in a subtype-specific manner, and may be functionally linked to SHH and MET circuitry. Thus coagulation system perturbations may elicit subtype/context-specific changes in vascular and cellular responses in MB.

Sayyah J, Bartakova A, Nogal N, et al.
The Ras-related protein, Rap1A, mediates thrombin-stimulated, integrin-dependent glioblastoma cell proliferation and tumor growth.
J Biol Chem. 2014; 289(25):17689-98 [PubMed] Free Access to Full Article Related Publications
Rap1 is a Ras family GTPase with a well documented role in ERK/MAP kinase signaling and integrin activation. Stimulation of the G-protein-coupled receptor PAR-1 with thrombin in human 1321N1 glioblastoma cells led to a robust increase in Rap1 activation. This response was sustained for up to 6 h and mediated through RhoA and phospholipase D (PLD). Thrombin treatment also induced a 5-fold increase in cell adhesion to fibronectin, which was blocked by down-regulating PLD or Rap1A or by treatment with a β1 integrin neutralizing antibody. In addition, thrombin treatment led to increases in phospho-focal adhesion kinase (tyrosine 397), ERK1/2 phosphorylation and cell proliferation, which were significantly inhibited in cells treated with β1 integrin antibody or Rap1A siRNA. To assess the role of Rap1A in tumor formation in vivo, we compared growth of 1321N1 cells stably expressing control, Rap1A or Rap1B shRNA in a mouse xenograft model. Deletion of Rap1A, but not of Rap1B, reduced tumor mass by >70% relative to control. Similar observations were made with U373MG glioblastoma cells in which Rap1A was down-regulated. Collectively, these findings implicate a Rap1A/β1 integrin pathway, activated downstream of G-protein-coupled receptor stimulation and RhoA, in glioblastoma cell proliferation. Moreover, our data demonstrate a critical role for Rap1A in glioblastoma tumor growth in vivo.

Castellone MD, Laukkanen MO, Teramoto H, et al.
Cross talk between the bombesin neuropeptide receptor and Sonic hedgehog pathways in small cell lung carcinoma.
Oncogene. 2015; 34(13):1679-87 [PubMed] Free Access to Full Article Related Publications
Small cell lung carcinoma (SCLC) often features the upregulation of the Sonic hedgehog (Shh) pathway leading to activation of Gli transcription factors. SCLC cells secrete bombesin (BBS)-like neuropeptides that act as autocrine growth factors. Here, we show that SCLC tumor samples feature co-expression of Shh and BBS-cognate receptor (gastrin-releasing peptide receptor (GRPR)). We also demonstrate that BBS activates Gli in SCLC cells, which is crucial for BBS-mediated SCLC proliferation, because cyclopamine, an inhibitor of the Shh pathway, hampered the BBS-mediated effects. BBS binding to GRPR stimulated Gli through its downstream Gαq and Gα₁₂/₁₃ GTPases, and consistently, other Gαq and Gα₁₃ coupled receptors (such as muscarinic receptor, m1, and thrombin receptor, PAR-1) and constitutively active GαqQL and Gα₁₂/₁₃QL mutants stimulated Gli. By using cells null for Gαq and Gα₁₂/₁₃, we demonstrate that these G proteins are strictly necessary for Gli activation by BBS. Moreover, by using constitutively active Rho small G-protein (Rho QL) as well as its inhibitor, C3 toxin, we show that Rho mediates G-protein-coupled receptor (GPCR)-, Gαq- and Gα₁₂/₁₃-dependent Gli stimulation. At the molecular level, BBS caused a significant increase in Shh gene transcription and protein secretion that was dependent on BBS-induced GPCR/Gαq-₁₂/₁₃/Rho mediated activation of nuclear factor κB (NFκB), which can stimulate a NF-κB response element in the Shh gene promoter. Our data identify a novel molecular network acting in SCLC linking autocrine BBS and Shh circuitries and suggest Shh inhibitors as novel therapeutic strategies against this aggressive cancer type.

Bäumer N, Krause A, Köhler G, et al.
Proteinase-Activated Receptor 1 (PAR1) regulates leukemic stem cell functions.
PLoS One. 2014; 9(4):e94993 [PubMed] Free Access to Full Article Related Publications
External signals that are mediated by specific receptors determine stem cell fate. The thrombin receptor PAR1 plays an important role in haemostasis, thrombosis and vascular biology, but also in tumor biology and angiogenesis. Its expression and function in hematopoietic stem cells is largely unknown. Here, we analyzed expression and function of PAR1 in primary hematopoietic cells and their leukemic counterparts. AML patients' blast cells expressed much lower levels of PAR1 mRNA and protein than CD34+ progenitor cells. Constitutive Par1-deficiency in adult mice did not affect engraftment or stem cell potential of hematopoietic cells. To model an AML with Par1-deficiency, we retrovirally introduced the oncogene MLL-AF9 in wild type and Par1-/- hematopoietic progenitor cells. Par1-deficiency did not alter initial leukemia development. However, the loss of Par1 enhanced leukemic stem cell function in vitro and in vivo. Re-expression of PAR1 in Par1-/- leukemic stem cells delayed leukemogenesis in vivo. These data indicate that Par1 contributes to leukemic stem cell maintenance.

Waitkus MS, Chandrasekharan UM, Willard B, et al.
Signal integration and gene induction by a functionally distinct STAT3 phosphoform.
Mol Cell Biol. 2014; 34(10):1800-11 [PubMed] Free Access to Full Article Related Publications
Aberrant activation of the ubiquitous transcription factor STAT3 is a major driver of solid tumor progression and pathological angiogenesis. STAT3 activity is regulated by numerous posttranslational modifications (PTMs), including Tyr(705) phosphorylation, which is widely used as an indicator of canonical STAT3 function. Here, we report a noncanonical mechanism of STAT3 activation that occurs independently of Tyr(705) phosphorylation. Using quantitative liquid chromatography-tandem mass spectrometry, we have discovered and characterized a novel STAT3 phosphoform that is simultaneously phosphorylated at Thr(714) and Ser(727) by glycogen synthase kinase 3α and -β (GSK-3α/β). Both Thr(714) and Ser(727) are required for STAT3-dependent gene induction in response to simultaneous activation of epidermal growth factor receptor (EGFR) and protease-activated receptor 1 (PAR-1) in endothelial cells. In this combinatorial signaling context, preventing formation of doubly phosphorylated STAT3 by depleting GSK-3α/β is sufficient to disrupt signal integration and inhibit STAT3-dependent gene expression. Levels of doubly phosphorylated STAT3 but not of Tyr(705)-phosphorylated STAT3 are remarkably elevated in clear-cell renal-cell carcinoma relative to adjacent normal tissue, suggesting that the GSK-3α/β-STAT3 pathway is active in the disease. Collectively, our results describe a functionally distinct, noncanonical STAT3 phosphoform that positively regulates target gene expression in a combinatorial signaling context and identify GSK-3α/β-STAT3 signaling as a potential therapeutic target in renal-cell carcinoma.

Wu Z, Zeng Y, Zhong M, Wang B
Targeting A549 lung adenocarcinoma cell growth and invasion with protease‑activated receptor‑1 siRNA.
Mol Med Rep. 2014; 9(5):1787-93 [PubMed] Related Publications
Lung cancer is the major cause of cancer-associated mortality worldwide and the invasive and metastatic characteristics of lung tumor cells are responsible for their high malignancy. Protease-activated receptor 1 (PAR1) is a G-protein-coupled receptor (GPCR) which is activated by a unique proteolytic mechanism. PARs have crucial roles in hemostasis and thrombosis as well as tumor progression. RNA interference (RNAi) is a fundamental cellular mechanism for gene silencing that is able to be harnessed for the development of novel anti-cancer drugs. In the present study, PAR1 was successfully inhibited by using Lipofectamine RNAiMAX transfection reagent to deliver siRNA. Inhibition occurred at the mRNA and protein level as determined by polymerase chain reaction and western blot analysis. Furthermore, the growth and invasion of tumor cells were significantly decreased. In conclusion, the present study demonstrated that the progression of A549 cells is able to be inhibited by knockdown of PAR1 expression. Efficient delivery of the specific siRNA targeting PAR1 may be used for further study in clinical cancer therapy.

D'Asti E, Magnus N, Meehan B, et al.
Genetic basis of thrombosis in cancer.
Semin Thromb Hemost. 2014; 40(3):284-95 [PubMed] Related Publications
Genetically altered cancer cells both provoke and respond to changes in their microenvironment, stroma, and vasculature. This includes local and systemic activation of the coagulation system, which is a part of the functional continuum involving inflammation, angiogenesis, and tissue repair programs, often reactivated in cancer. These responses coevolve with, and contribute to, the malignant process. Cancer coagulopathy is not only a source of comorbidity and mortality in cancer patients, but it also affects the disease biology including processes of tumor growth, initiation, dormancy, invasion, angiogenesis, metastasis, and therapeutic responsiveness. Notably, genetic and cellular differences between different cancer types are paralleled by a degree of diversity in the related coagulation system perturbations. Although some of these differences may be unspecific, iatrogenic, or indirect in nature, others are affected by oncogenic pathways (RAS, EGFR, HER2, MET, PTEN, and TP53) activated in cancer cells due to driver mutations of critical genes. Such mutations cooperate with hypoxia, cellular differentiation, and other influences to alter the expression of tissue factor, protease-activated receptors (e.g., PAR-1 and PAR-2), coagulation factors (FII and FVII), and other molecules related to the hemostatic system. Oncogenic pathways also control secretion of some of these entities from cancer cells, either as soluble proteins, or as cargo of extracellular vesicles/microparticles. Moreover, emerging evidence suggests that the expression profiles of coagulation-related genes differ between molecularly and genetically distinct subgroups of specific malignancies such as glioblastoma multiforme and medulloblastoma. Certain hereditary thrombophilias may also affect cancer pathogenesis. We suggest that mechanisms of cancer coagulopathy may be more diverse and genetically modulated than hitherto realized. If so, a possibility may exist to deliver more personalized, biologically based, anticoagulation, and thereby improve patient survival.

Saleiban A, Faxälv L, Claesson K, et al.
miR-20b regulates expression of proteinase-activated receptor-1 (PAR-1) thrombin receptor in melanoma cells.
Pigment Cell Melanoma Res. 2014; 27(3):431-41 [PubMed] Related Publications
The proteinase-activated receptor 1 (PAR-1) plays a central role in melanoma progression and its expression level is believed to correlate with the degree of cancer invasiveness. Here, we show that PAR-1 is post-transcriptionally regulated by miR-20b microRNA in human melanoma cells. PAR-1 was found to be expressed in metastatic melanoma cells but was barely detectable in primary melanoma. By transducing primary melanoma cells with a lentivirus containing a 3'-UTR construct of PAR-1 mRNA, we could show that endogenous melanoma microRNAs interacted with PAR-1 3'-UTR and silenced a fused luciferase reporter. Transfection of an inhibitor against miR-20b into primary melanoma cells reversed this process. Finally, transfection of miR-20b mimic into metastatic melanoma cells caused downregulation of the luciferase reporter. We conclude that miR-20b regulates expression of melanoma PAR-1 receptor, which may explain the differential expression of PAR-1 observed in human melanoma.

Fang BA, Kovačević Ž, Park KC, et al.
Molecular functions of the iron-regulated metastasis suppressor, NDRG1, and its potential as a molecular target for cancer therapy.
Biochim Biophys Acta. 2014; 1845(1):1-19 [PubMed] Related Publications
N-myc down-regulated gene 1 (NDRG1) is a known metastasis suppressor in multiple cancers, being also involved in embryogenesis and development, cell growth and differentiation, lipid biosynthesis and myelination, stress responses and immunity. In addition to its primary role as a metastasis suppressor, NDRG1 can also influence other stages of carcinogenesis, namely angiogenesis and primary tumour growth. NDRG1 is regulated by multiple effectors in normal and neoplastic cells, including N-myc, histone acetylation, hypoxia, cellular iron levels and intracellular calcium. Further, studies have found that NDRG1 is up-regulated in neoplastic cells after treatment with novel iron chelators, which are a promising therapy for effective cancer management. Although the pathways by which NDRG1 exerts its functions in cancers have been documented, the relationship between the molecular structure of this protein and its functions remains unclear. In fact, recent studies suggest that, in certain cancers, NDRG1 is post-translationally modified, possibly by the activity of endogenous trypsins, leading to a subsequent alteration in its metastasis suppressor activity. This review describes the role of this important metastasis suppressor and discusses interesting unresolved issues regarding this protein.

Jaber M, Maoz M, Kancharla A, et al.
Protease-activated-receptor-2 affects protease-activated-receptor-1-driven breast cancer.
Cell Mol Life Sci. 2014; 71(13):2517-33 [PubMed] Related Publications
Mammalian protease-activated-receptor-1 and -2 (PAR1 and PAR2) are activated by proteases found in the flexible microenvironment of a tumor and play a central role in breast cancer. We propose in the present study that PAR1 and PAR2 act together as a functional unit during malignant and physiological invasion processes. This notion is supported by assessing pro-tumor functions in the presence of short hairpin; shRNA knocked-down hPar2 or by the use of a truncated PAR2 devoid of the entire cytoplasmic tail. Silencing of hPar2 by shRNA-attenuated thrombin induced PAR1 signaling as recapitulated by inhibiting the assembly of Etk/Bmx or Akt onto PAR1-C-tail, by thrombin-instigated colony formation and invasion. Strikingly, shRNA-hPar2 also inhibited the TFLLRN selective PAR1 pro-tumor functions. In addition, while evaluating the physiological invasion process of placenta extravillous trophoblast (EVT) organ culture, we observed inhibition of both thrombin or the selective PAR1 ligand; TFLLRNPNDK induced EVT invasion by shRNA-hPar2 but not by scrambled shRNA-hPar2. In parallel, when a truncated PAR2 was utilized in a xenograft mouse model, it inhibited PAR1-PAR2-driven tumor growth in vivo. Similarly, it also attenuated the interaction of Etk/Bmx with the PAR1-C-tail in vitro and decreased markedly selective PAR1-induced Matrigel invasion. Confocal images demonstrated co-localization of PAR1 and PAR2 in HEK293T cells over-expressing YFP-hPar2 and HA-hPar1. Co-immuno-precipitation analyses revealed PAR1-PAR2 complex formation but no PAR1-CXCR4 complex was formed. Taken together, our observations show that PAR1 and PAR2 act as a functional unit in tumor development and placenta-uterus interactions. This conclusion may have significant consequences on future breast cancer therapeutic modalities and improved late pregnancy outcome.

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