The epidermal growth factor receptor (EGFR) and proline rich tyrosine kinase 2 (PYK2) are involved in tissue factor dependent factor VIIa signalling in HaCaT cells

High CD142 Level Marks Tumor-Promoting Fibroblasts with Targeting Potential in Colorectal Cancer

Colorectal cancer (CRC) has a high incidence and is one of the leading causes of cancer-related death. The accumulation of cancer-associated fibroblasts (CAF) induces an aggressive, stem-like phenotype in tumor cells, and it indicates a poor prognosis. However, cellular heterogeneity among CAFs and the targeting of both stromal and CRC cells are not yet well resolved. Here, we identified CD142high fibroblasts with a higher stimulating effect on CRC cell proliferation via secreting more hepatocyte growth factor (HGF) compared to CD142low CAFs. We also found that combinations of inhibitors that had either a promising effect in other cancer types or are more active in CRC compared to normal colonic epithelium acted synergistically in CRC cells. Importantly, heat shock protein 90 (HSP90) inhibitor selected against CD142high fibroblasts, and both CRC cells and CAFs were sensitive to a BCL-xL inhibitor. However, targeting mitogen-activated protein kinase kinase (MEK) was ineffective in fibroblasts, and an epigenetic inhibitor selected for a tumor cell population with markers of aggressive behavior. Thus, we suggest BCL-xL and HSP90 inhibitors to eliminate cancer cells and decrease the tumor-promoting CD142high CAF population. This may be the basis of a strategy to target both CRC cells and stromal fibroblasts, resulting in the inhibition of tumor relapse.

The Tissue Factor Pathway in Cancer: Overview and Role of Heparan Sulfate Proteoglycans

Historically, the only focus on tissue factor (TF) in clinical pathophysiology has been on its function as the initiation of the extrinsic coagulation cascade. This obsolete vessel-wall TF dogma is now being challenged by the findings that TF circulates throughout the body as a soluble form, a cell-associated protein, and a binding microparticle. Furthermore, it has been observed that TF is expressed by various cell types, including T-lymphocytes and platelets, and that certain pathological situations, such as chronic and acute inflammatory states, and cancer, may increase its expression and activity. Transmembrane G protein-coupled protease-activated receptors can be proteolytically cleaved by the TF:FVIIa complex that develops when TF binds to Factor VII (PARs). The TF:FVIIa complex can activate integrins, receptor tyrosine kinases (RTKs), and PARs in addition to PARs. Cancer cells use these signaling pathways to promote cell division, angiogenesis, metastasis, and the maintenance of cancer stem-like cells. Proteoglycans play a crucial role in the biochemical and mechanical properties of the cellular extracellular matrix, where they control cellular behavior via interacting with transmembrane receptors. For TFPI.fXa complexes, heparan sulfate proteoglycans (HSPGs) may serve as the primary receptor for uptake and degradation. The regulation of TF expression, TF signaling mechanisms, their pathogenic effects, and their therapeutic targeting in cancer are all covered in detail here.

Activation of β1 integrins and caveolin-1 by TF/FVIIa promotes IGF-1R signaling and cell survival

The tissue factor/coagulation factor VIIa (TF/FVIIa) complex induces transactivation of the IGF-1 receptor (IGF-1R) in a number of different cell types. The mechanism is largely unknown. The transactivation leads to protection from apoptosis and nuclear translocation of the IGF-1R. The aim of this study was to clarify the signaling pathway between TF and IGF-1R after FVIIa treatment with PC3 and DU145 prostate or MDA-MB-231 breast cancer cells as model systems. Protein interactions, levels, and phosphorylations were assessed by proximity ligation assay or flow cytometry in intact cells and by western blot on cell lysates. The transactivation of the IGF-1R was found dependent on TF/FVIIa-induced activation of β1-integrins. A series of experiments led to the conclusion that the caveolae protein caveolin-1 prevented IGF-1R activation in resting cells via its scaffolding domain. TF/FVIIa/β1-integrins terminated this inhibition by activation of Src family kinases and subsequent phosphorylation of caveolin-1 on tyrosine 14. This phosphorylation was not seen after treatment with PAR1 or PAR2 agonists. Consequently, the protective effect of FVIIa against apoptosis induced by the death receptor agonist TRAIL and the de novo synthesis of cyclin D1 induced by nuclear IGF-1R accumulation were both significantly reduced by down-regulation of β1-integrins or overexpression of the caveolin-1 scaffolding domain. In conclusion, we present a plausible mechanism for the interplay between TF and IGF-1R involving FVIIa, β1-integrins, Src family proteins, and caveolin-1. Our results increase the knowledge of diseases associated with TF and IGF-1R overexpression in general but specifically of TF-mediated signaling with focus on cell survival.

Effects of reduced platelet count on the prognosis for patients with non-small cell lung cancer treated with EGFR-TKI: a retrospective study

BACKGROUND

Progressive lung cancer is associated with abnormal coagulation. Platelets play a vital part in evading immune surveillance and angiogenesis in the case of tumor metastasis. The study aimed to analyze the predictive and prognostic effects of platelet count on non-small cell lung cancer (NSCLC) patients treated with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs).

METHODS

This study retrospectively analyzed the prognostic effects of platelets on 52 NSCLC patients with epidermal growth factor receptor (EGFR) mutant following EGFR-TKI treatment. Related data, together with the progression-free survival (PFS) and overall survival (OS) were collected before and after 2 cycles of treatments (60 days).

RESULTS

The anti-EGFR treatment markedly reduced the platelet count in 33 (63.5%) patients after 2 cycles of treatment. Multivariate Cox analysis revealed that, the decreased platelet count was closely correlated with the longer OS (HR = 0.293; 95%CI: 0.107-0.799; p = 0.017). Besides, the median OS was 326 days in the decreased platelet count group and 241 days in the increased platelet count group (HR = 0.311; 95%CI: 0.118-0.818; P = 0.018), as obtained from the independent baseline platelet levels and other clinical features.

CONCLUSIONS

The platelet count may predict the prognosis for EGFR-TKI treatment without additional costs. Besides, changes in platelet count may serve as a meaningful parameter to establish the prognostic model for NSCLC patients receiving anti-EGFR targeted therapy.

Beyond thrombosis: the impact of tissue factor signaling in cancer

Tissue factor (TF) is the primary initiator of the coagulation cascade, though its effects extend well beyond hemostasis. When TF binds to Factor VII, the resulting TF:FVIIa complex can proteolytically cleave transmembrane G protein-coupled protease-activated receptors (PARs). In addition to activating PARs, TF:FVIIa complex can also activate receptor tyrosine kinases (RTKs) and integrins. These signaling pathways are utilized by tumors to increase cell proliferation, angiogenesis, metastasis, and cancer stem-like cell maintenance. Herein, we review in detail the regulation of TF expression, mechanisms of TF signaling, their pathological consequences, and how it is being targeted in experimental cancer therapeutics.

Mapping Subpopulations of Cancer Cell-Derived Extracellular Vesicles and Particles by Nano-Flow Cytometry

The elusive complexity of membranous extracellular vesicle (EV) and membrane-less extracellular particle (EP) populations released from various cellular sources contains clues as to their biological functions and diagnostic utility. In this study, we employed optimized multicolor nano-flow cytometry, structured illumination (SIM), and atomic force microscopy (AFM) to bridge sensitive detection at the single EV/EP level and high-throughput analysis of cancer cell secretomes. We applied these approaches to particles released from intact cells driven by several different transforming mechanisms or to cells under therapeutic stress imposed by pharmacological inhibition of their oncogenic drivers, such as epidermal growth factor receptor (EGFR). We demonstrate a highly heterogeneous distribution of biologically relevant elements of the EV/EP cargo, including oncoproteins (EGFR), clotting factors (tissue factor), pro-metastatic integrins (ITGA6, ITGA4), tetraspanins (CD63), and genomic DNA across the entire particulate secretome of cancer cells. We observed that targeting EGFR activity with irreversible kinase inhibitors (dacomitinib) triggers emission of DNA containing EP/EV subpopulations, including particles (chromatimeres) harboring both EGFR and DNase-resistant chromatin. While nano-flow cytometry enables quantification of these changes across the entire particular secretome, SIM reveals individual molecular topography of EV/EP subsets and AFM exposes some of their physical properties, including the presence of nanofilaments and other substructures. We describe differential uptake rates of distinct EV subsets, resulting in preferential internalization of exosome-like small EVs by cancer cells to the exclusion of larger EVs. Thus, our study illustrates the potential of nano-flow cytometry coupled with high-resolution microscopy to explore the cancer-related EV/EP landscape.

Crosstalk between TF/FVIIa and EGFR signaling in colorectal cancer cells

TF/FVIIa (Tissue Factor/Active Coagulation factor VII) and EGFR (Epidermal Growth Factor Receptor) signaling both promote malignant progression of colorectal cancer. However, the crosstalk of these two signaling pathways in human colorectal cancer cells remains unclear. Here we detected the changes of mRNA profile in human colorectal cancer cell SW620 exposed to FVIIa. Microarray showed that mRNA levels of EGFR ligands were significantly upregulated. Western blot analysis confirmed the upregulation of EGFR ligands and the phosphorylation of EGFR at tyrosine-845 in colorectal cancer cells exposed to FVIIa. However, knockdown of TF by RNAi could block the upregulation of EGFR ligands induced by FVIIa stimulation. On the other hand, the expression of components of TF/FVIIa signaling was significantly upregulated in LoVo cells stimulated by EGF. However, the crosstalk between the two signaling pathways could not be detected in HT-29 colon cancer cells bearing wild-type KRAS. Taken together, our study suggest that the crosstalk between TF/FVIIa and EGFR signaling pathways in colon cancer cells depends on KRAS mutation.

Tissue factor at the crossroad of coagulation and cell signaling

The tissue factor (TF) pathway plays a central role in hemostasis and thrombo-inflammatory diseases. Although structure-function relationships of the TF initiation complex are elucidated, new facets of the dynamic regulation of TF's activities in cells continue to emerge. Cellular pathways that render TF non-coagulant participate in signaling of distinct TF complexes with associated proteases through the protease-activated receptor (PAR) family of G protein-coupled receptors. Additional co-receptors, including the endothelial protein C receptor (EPCR) and integrins, confer signaling specificity by directing subcellular localization and trafficking. We here review how TF is switched between its role in coagulation and cell signaling through thiol-disulfide exchange reactions in the context of physiologically relevant lipid microdomains. Inflammatory mediators, including reactive oxygen species, activators of the inflammasome, and the complement cascade play pivotal roles in TF procoagulant activation on monocytes, macrophages and endothelial cells. We furthermore discuss how TF, intracellular ligands, co-receptors and associated proteases are integrated in PAR-dependent cell signaling pathways controlling innate immunity, cancer and metabolic inflammation. Knowledge of the precise interactions of TF in coagulation and cell signaling is important for understanding effects of new anticoagulants beyond thrombosis and identification of new applications of these drugs for potential additional therapeutic benefits.

Tissue factor: newer concepts in thrombosis and its role beyond thrombosis and hemostasis

For many years, the attention on tissue factor (TF) in human pathophysiology has been limited to its role as initiator of extrinsic coagulation pathway. Moreover, it was described as a glycoprotein located in several tissue including vascular wall and atherosclerotic plaque. However, in the last two decades, the discovery that TF circulates in the blood as cell-associated protein, microparticles (MPs) bound and as soluble form, is changing this old vessel-wall TF dogma. Moreover, it has been reported that TF is expressed by different cell types, even T lymphocytes and platelets, and different pathological conditions, such as acute and chronic inflammatory status, and cancer, may enhance its expression and activity. Thus, recent advances in the biology of TF have clearly indicated that beyond its known effects on blood coagulation, it is a "true surface receptor" involved in many intracellular signaling, cell-survival, gene and protein expression, proliferation, angiogenesis and tumor metastasis. Finally, therapeutic modulation of TF expression and/or activity has been tested with controversial results. This report, starting from the old point of view about TF as initiator of extrinsic coagulation pathway, briefly illustrates the more recent concepts about TF and thrombosis and finally gives an overview about its role beyond thrombosis and haemostasis focusing on the different intracellular mechanisms triggered by its activation and potentially involved in atherosclerosis.

Methylation-dependent Tissue Factor Suppression Contributes to the Reduced Malignancy of IDH1-mutant Gliomas

PURPOSE

Gliomas with isocitrate dehydrogenase 1 mutations (IDH1^mut) are less aggressive than IDH1 wild-type (IDH1^wt) gliomas and have global genomic hypermethylation. Yet it is unclear how specific hypermethylation events contribute to the IDH1^mut phenotype. Previously, we showed that the gene encoding the procoagulant tissue factor (TF), F3, is among the most hypermethylated and downregulated genes in IDH1^mut gliomas, correlating with greatly reduced thrombosis in patients with IDH1^mut glioma. Because TF also increases the aggressiveness of many cancers, the current study explored the contribution of TF suppression to the reduced malignancy of IDH1^mut gliomas.Experimental Design: TF expression was manipulated in patient-derived IDH1^mut and IDH1^wt glioma cells, followed by evaluation of in vitro and in vivo behavior and analyses of cell signaling pathways.

RESULTS

A demethylating agent, decitabine, increased F3 transcription and TF-dependent coagulative activity in IDH1^mut cells, but not in IDH1^wt cells. TF induction enhanced the proliferation, invasion, and colony formation of IDH1^mut cells, and increased the intracranial engraftment of IDH1^mut GBM164 from 0% to 100% (P = 0.0001). Conversely, TF knockdown doubled the median survival of mice engrafted with IDH1^wt/EGFRvIII^amp GBM6, and caused complete regression of IDH1^wt/EGFR^amp GBM12 (P = 0.001). In vitro and in vivo effects were linked to activation of receptor tyrosine kinases (RTK) by TF through a Src-dependent intracellular pathway, even when extracellular RTK stimulation was blocked. TF stimulated invasion predominately through upregulation of β-catenin.

CONCLUSIONS

These data show that TF suppression is a component of IDH1^mut glioma behavior, and that it may therefore be an attractive target against IDH1^wt gliomas.

Oncogenes and the coagulation system--forces that modulate dormant and aggressive states in cancer

Cancers arise and progress genetically amidst profound perturbations of the microenvironmental and systemic homeostasis. This includes the coagulation system, which is a part of the vascular milieu (niche) that remains under the control of molecular events occurring within the cancer cell genome. Thus, activation of several prototypic oncogenic pathways, such as RAS, EGFR, HER2, MET, SHH and loss of tumor suppressors (PTEN, TP53) alter the expression, activity and vesicular release of coagulation effectors, as exemplified by tissue factor (TF). The cancer-specific determinants of coagulopathy are also illustrated by the emerging link between the expression profiles of coagulation-related genes (coagulome) in glioblastoma multiforme (GBM), medulloblastoma (MB) and possibly other cancers and molecular subtypes of these respective tumors. The state of the coagulome is consequential for growth, metastasis and angiogenesis of established tumors, but could potentially also affect dormant cancer cells. For example, TF expression may trigger awakening of dormant glioma cells in mice in a manner involving recruitment of vascular and inflammatory cells, and resulting in lasting changes in the cancer cell genome and epigenome. Thus, coagulation system effectors could act as both targets and (indirect) inducers of genetic tumor progression, and a better understanding of this link may hold new diagnostic and therapeutic opportunities.

Brain neoplasms and coagulation-lessons from heterogeneity

The coagulation system constitutes an important facet of the unique vascular microenvironment in which primary and metastatic brain tumors evolve and progress. While brain tumor cells express tissue factor (TF) and other effectors of the coagulation system (coagulome), their propensity to induce local and peripheral thrombosis is highly diverse, most dramatic in the case of glioblastoma multiforme (GBM), and less obvious in pediatric tumors. While the immediate medical needs often frame the discussion on current clinical challenges, the coagulation pathway may contribute to brain tumor progression through subtle, context-dependent, and non-coagulant effects, such as induction of inflammation, angiogenesis, or by responding to iatrogenic insults (e.g. surgery). In this regard, the emerging molecular diversity of brain tumor suptypes (e.g. in glioma and medulloblastoma) highlights the link between oncogenic pathways and the tumor repertoire of coagulation system regulators (coagulome). This relationship may influence the mechanisms of spontaneous and therapeutically provoked tumor cell interactions with the coagulation system as a whole. Indeed, oncogenes (EGFR, MET) and tumor suppressors (PTEN, TP53) may alter the expression, activity, and vesicular release of tissue factor (TF), and cause other changes. Conversely, the coagulant microenvironment may also influence the molecular evolution of brain tumor cells through selective and instructive cues. We suggest that effective targeting of the coagulation system in brain tumors should be explored through molecular stratification, stage-specific analysis, and more personalized approaches including thromboprophylaxis and adjuvant treatment aimed at improvement of patient survival.

Tissue factor/factor VIIa induces cell survival and gene transcription by transactivation of the insulin-like growth factor 1 receptor

The insulin-like growth factor 1 receptor (IGF-1R) is known to promote survival and has also been implicated in the pathogenesis of several disease states, including cardiovascular disorders and cancer. Recently, we showed that binding of coagulation factor VIIa (FVIIa) to its receptor tissue factor (TF) protects cancer cells from TNF-related apoptosis inducing ligand (TRAIL)-induced apoptosis. Here we present evidence that this biological function of TF/FVIIa is dependent on the IGF-1R. IGF-1R inhibitors AG1024 and PPP as well as siRNA-mediated downregulation of IGF-1R, abolished the TF/FVIIa-mediated protection against TRAIL-induced apoptosis. Moreover, FVIIa rapidly induced a time- and concentration-dependent tyrosine phosphorylation of the IGF-1R in MDA-MB-231 breast cancer cells and in primary human monocytes, an event that was accompanied by IGF-1R chromatin binding and gene transcription. We hereby present novel evidence of a cross-talk between the coagulation and IGF-1R signalling systems, and propose that the IGF-1R is a key player in mediating TF/FVIIa-induced cell survival.

Tissue factor non-coagulant signaling - molecular mechanisms and biological consequences with a focus on cell migration and apoptosis

Tissue factor (TF), a transmembrane glycoprotein, is the main initiator of the blood coagulation cascade. TF is also recognized as a true signaling receptor. There is accumulating evidence that the downstream signaling effects of the TF complexes are transduced by several mechanisms, including: activation of protease-activated receptor (PAR)-1 and PAR-2, and the PAR-dependent pathways, via the TF cytoplasmic domain and by transactivation of receptor tyrosine kinases. Triggering of signaling cascades such as the mitogen-activated protein kinase and phosphoinositide 3-kinase/AKT pathways couples TF to a multitude of functions within the cell, such as proliferation, cell migration, and survival. Thus, TF has a Janus face; on the one hand, it has vital life-maintaining functions, and on the other it has harmful effects, exemplified by inflammation, the acute coronary syndromes, and cancer. TF mediates a broad spectrum of signaling mechanisms. Learning more about these different mechanisms/pathways will lead to new treatment strategies, which can ultimately be personalized.

Genetic pathways linking hemostasis and cancer

Oncogenic events impact interactions of cancer cells with their surroundings. Amongst the most consequential, in this regard, is the influence on angiogenesis, inflammation and hemostasis. Indeed, mutant oncogenes (EGFR, HER2, RAS, MET, PML-RARα) are known to alter the expression of angiogenic and pro-inflammatory factors, as well as change the cancer cell coagulome, including the levels of tissue factor (TF) and other mediators (PAI-1, COX2). Accompanying losses of tumour suppressor genes (PTEN, p53), and changes in microRNA (miR-19b, miR-520) facilitate these effects. Transforming genes may also trigger ectopic production of coagulation factors (e.g. FVII) by cancer cells and their release and properties of procoagulant microparticles (MPs). By deregulating protease activated receptors (PAR1/2) oncogenes may also change tumour cell responses to coagulation factor signalling. These changes act in concert with microenvironmental factors (hypoxia), stress responses (therapy) and differentiation programs, including epithelial-to-mesechymal transitions (EMT) and through tumour initiating cell (TIC) compartment. In so doing, the coagulation system influences early (initiation, angiogenesis), intermediate (growth, invasion) and late stages (metastasis, relapse) of cancer progression. In fact, TF may act as a molecular switch that controls the transition between dormant, latent and progressive/metastatic disease. TIC-like cells may play a role in these effects, as they express TF and PAR-1/2, and respond to stimulation with their agonists. As major human malignancies (e.g. glioblastoma) are increasingly recognized to consist of a spectrum of molecularly distinct disease subtypes driven by specific genetic pathways, so too may their patterns of interaction differ with the coagulation system. A better understanding of these linkages may be a source of new diagnostic, prognostic and therapeutic opportunities.

Factor VII deficiency impairs cutaneous wound healing in mice

Skin keratinocytes express tissue factor (TF) and are highly associated with skin wound healing. Although it has been demonstrated that perivascular TF expression in granulation tissue formed after dermal injury is downregulated during healing, studies of the mechanism of factor (F) VII, a TF ligand, in skin wound healing are lacking. We reported the use of a dermal punch model to demonstrate that low-expressing FVII mice (approximately 1% of wild type [WT]) exhibited impaired skin wound healing compared with WT controls. These low-FVII mice showed defective reepithelialization and reduced inflammatory cell infiltration at wound sites. This attenuated reepithelialization was associated with diminished expression of the transcription factor early growth response 1 (Egr-1). In vitro, Egr-1 was shown to be essential for the FVIIa-induced regulation of keratinocyte migration and inflammation. Both Egr-1 upregulation and downstream inflammatory cytokine appearance in keratinocytes depended on FVIIa/TF/protease-activated receptor 2 (PAR-2)-induced signaling and did not require subsequent generation of FXa and thrombin. The participation of Egr-1 in FVIIa-mediated regulation of keratinocyte function was confirmed by use of Egr-1-deficient mice, wherein a significant delay in skin wound healing after injury was observed, relative to WT mice. The results from these studies demonstrate an in vivo mechanistic relationship between FVIIa, Egr-1 and the inflammatory response in keratinocyte function during the wound healing process.

Cystatin E/M suppresses legumain activity and invasion of human melanoma

Background

High activity of cysteine proteases such as legumain and the cathepsins have been shown to facilitate growth and invasion of a variety of tumor types. In breast cancer, several recent studies have indicated that loss of the cysteine protease inhibitor cystatin E/M leads to increased growth and metastasis. Although cystatin E/M is normally expressed in the skin, its role in cysteine protease regulation and progression of malignant melanoma has not been studied.

Methods

A panel of various non-melanoma and melanoma cell lines was used. Cystatin E/M and C were analyzed in cell media by immunoblotting and ELISA. Legumain, cathepsin B and L were analyzed in cell lysates by immunoblotting and their enzymatic activities were analyzed by peptide substrates. Two melanoma cell lines lacking detectable secretion of cystatin E/M were transfected with a cystatin E/M expression plasmid (pCST6), and migration and invasiveness were studied by a Matrigel invasion assay.

Results

Cystatin E/M was undetectable in media from all established melanoma cell lines examined, whereas strong immunobands were detected in two of five primary melanoma lines and in two of six lines derived from patients with metastatic disease. Among the four melanoma lines secreting cystatin E/M, the glycosylated form (17 kD) was predominant compared to the non-glycosylated form (14 kD). Legumain, cathepsin B and L were expressed and active in most of the cell lines, although at low levels in the melanomas expressing cystatin E/M. In the melanoma lines where cystatin E/M was secreted, cystatin C was generally absent or expressed at a very low level. When melanoma cells lacking secretion of cystatin E/M were transfected with pCST6, their intracellular legumain activity was significantly inhibited. In contrast, cathepsin B activity was not affected. Furthermore, invasion was suppressed in cystatin E/M over-expressing melanoma cell lines as measured by the transwell Matrigel assay.

Conclusions

These results suggest that the level of cystatin E/M regulates legumain activity and hence the invasive potential of human melanoma cells.

Vasopressin up-regulates the expression of growth-related immediate-early genes via two distinct EGF receptor transactivation pathways

Activation of V(1a) receptor triggers the expression of growth-related immediate-early genes (IEGs), including c-Fos and Egr-1. We found that pre-treatment of rat vascular smooth muscle A-10 cell line with the EGF receptor inhibitor AG1478 or the over-expression of an EGFR dominant negative mutant (HEBCD533) blocked the vasopressin-induced expression of IEGs, suggesting that activation of these early genes mediated by V(1a) receptor is via transactivation of the EGF receptor. Importantly, the inhibition of the metalloproteinases, which catalyzed the shedding of the EGF receptor agonist HB-EGF, selectively blocked the vasopressin-induced expression c-Fos. On the other hand, the inhibition of c-Src selectively blocked the vasopressin-induced expression of Egr-1. Interestingly, in contrast to the expression of c-Fos, the expression of Egr-1 was mediated via the Ras/MEK/MAPK-dependent signalling pathway. Vasopressin-triggered expression of both genes required the release of intracellular calcium, activation of PKC and beta-arrestin 2. These findings demonstrated that vasopressin up-regulated the expression of c-Fos and Erg-1 via transactivation of two distinct EGF receptor-dependent signalling pathways.

Tissue factor, angiogenesis and tumour progression

Tissue factor, the primary initiator of the coagulation cascade, maintains vascular integrity in response to injury. It is now recognised that, in addition to the role as a procoagulant activator, tissue factor participates in many tumour-related processes that contribute to malignant disease progression. The present review details the recent evidence supporting a role for tissue factor in tumour haemostasis, angiogenesis, metastasis and malignant cell survival. Furthermore, future research directions are discussed that may enhance our understanding of the role and regulation of this protein, which could ultimately lead to the innovative design and development of new anticancer therapies.

TF/FVIIa Transactivate PDGFRβ to Regulate PDGF-BB–Induced Chemotaxis in Different Cell Types

Background— We have previously reported the potentiation of PDGF-BB–induced chemotaxis of fibroblasts, vascular smooth muscle cells, and endothelial cells by FVIIa. Here we studied the role of TF/FVIIa and the induced signaling pathways in regulation of chemotaxis of human monocytes, fibroblasts, and porcine aorta endothelial cells.

Methods and Results— Human monocytes were obtained by using Ficoll-Paque gradient and the MACS system (for highly purified population), fibroblasts and PAE cells have been characterized previously. Inhibitors of selected signaling intermediates were used, and the effect of TF/FVIIa on the migratory response of all cells to chemotactic agents was analyzed. The induced signaling was studied by immunoprecipitation and Western blotting. TF/FVIIa complex selectively enhanced PDGF-BB–induced chemotaxis in a Src-family, PLC, and PAR-2–dependent manner. Using PAE cells we identified c-Src and c-Yes as the Src-family members activated by TF/FVIIa. We report for the first time the PAR-2 and Src family-dependent transactivation of PDGFRβ by TF/FVIIa involving phosphorylation of a subset of PDGFRβ tyrosines.

Conclusions— The described transactivation is a likely mechanism of TF/FVIIa-mediated regulation of PDGF-BB–induced chemotaxis. Similar behavior of 3 principally different cell types in our experimental setup may reflect a general function of TF in regulation of cell migration.

Tissue factor pathway inhibitor: structure, biology and involvement in disease

Tissue factor (TF)-initiated coagulation plays a significant role in the pathophysiology of many diseases, including cancer and inflammation. Tissue factor pathway inhibitor (TFPI) is a plasma Kunitz-type serine protease inhibitor, which modulates initiations of coagulation induced by TF. In a factor (F) Xa-dependent feedback system, TFPI binds directly and inhibits the TF-FVII/FVIIa complex. Normally, TFPI exists in plasma both as a full-length molecule and as variably carboxy-terminal truncated forms. TFPI also circulates in complex with plasma lipoproteins. The levels and the dual inhibitor effect of TFPI on FXa and TF-FVII/FVIIa complex offers insight into the mechanisms of various pathological conditions triggered by TF. The use of selective pharmacological inhibitors has become an indispensable tool in experimental haemostasis and thrombosis research. In vivo administration of recombinant TFPI (rTFPI) in an experimental animal model prevents thrombosis (and re-thrombosis after thrombolysis), reduces mortality from E. coli-induced-septic shock, prevents fibrin deposition on subendothelial human matrix and protects against disseminated intravascular coagulation (DIC). Thus, TFPI may play an important role in modulating TF-induced thrombogenesis and it may also provide a unique therapeutic approach for prophylaxis and/or treatment of various diseases. In this review, we consider structural and biochemical aspects of the TFPI molecule and detail its inhibitory mechanisms and therapeutic implications in various disease conditions.

Tissue factor-factor VIIa signaling

How does tissue factor (TF), whose principle role is to support clotting factor VIIa (FVIIa) in triggering the coagulation cascade, affect various pathophysiological processes? One of the answers is that TF interaction with FVIIa not only initiates clotting but also induces cell signaling via activation of G-protein-coupled protease activated receptors (PARs). Recent studies using various cell model systems and limited in vivo systems are beginning to define how TF-VIIa-induced signaling regulates cellular behavior. Signaling pathways initiated by both TF-VIIa protease activation of PARs and phosphorylation of the TF-cytoplasmic domain appear to regulate cellular functions. In the present article, we review the emerging data on the mechanism of TF-mediated cell signaling and how it regulates various cellular responses, with particular focus on TF-VIIa protease-dependent signaling.