Twist is required for thrombin-induced tumor angiogenesis and growth

Id2 exerts tumor suppressor properties in lung cancer through its effects on cancer cell invasion and migration

Background

Despite advances in prognosis and treatment of lung adenocarcinoma (LADC), a notable non–small cell lung cancer subtype, patient outcomes are still unsatisfactory. New insight on novel therapeutic strategies for LADC may be gained from a more comprehensive understanding of cancer progression mechanisms. Such strategies could reduce the mortality and morbidity of patients with LADC. In our previous study, we performed cDNA microarray screening and found an inverse relationship between inhibitor of DNA binding 2 (Id2) expression levels and the invasiveness of LADC cells.

Materials and Methods

To identify the functional roles of Id2 and its action mechanisms in LADC progression, we successfully established several Id2-overexpressing and Id2-silenced LADC cell clones. Subsequently, we examined in vitro the effects exerted by Id2 on cell morphology, proliferation, colony formation, invasive, and migratory activities and examined in vivo those exerted by Id2 on cell metastasis. The mechanisms underlying the action of Id2 were investigated using RNA-seq and pathway analyses. Furthermore, the correlations of Id2 with its target gene expression and clinical outcomes were calculated.

Results

Our data revealed that Id2 overexpression could inhibit LADC cells’ migratory, invasive, proliferation, and colony formation capabilities. Silencing Id2 expression in LADC cells reversed the aforementioned inhibitory effects, and knockdown of Id2 increased LADC cells’ metastatic abilities in vivo. Bioinformatics analysis revealed that these effects of Id2 on cancer progression might be regulated by focal adhesion kinase (FAK) signaling and CD44/Twist expression. Furthermore, in online clinical database analysis, patients with LADC whose Id2 expression levels were high and FAK/Twist expression levels were low had superior clinical outcomes.

Tight junction protein 1 promotes vasculature remodeling via regulating USP2/TWIST1 in bladder cancer

Bladder cancer (BLCA) is the most common malignant tumor of the urinary system and is characterized by high metastatic rates and poor prognosis. The expression of tight junction protein 1 (TJP1) is associated with bladder cancer invasion; however, the mechanism by which TJP1 affects vasculature remodeling remains unknown. In this study, we found that TJP1 expression correlated with tumor angiogenesis and poor overall survival in clinical samples. Furthermore, TJP1 overexpression promoted tumor angiogenesis in BLCA cells and stimulated recruitment of macrophages to tumors by upregulating CCL2 expression. Mechanistically, TJP1 interacted with TWIST1 and enhanced the transcriptional activity of CCL2. The impairment of tumor angiogenesis caused by knockdown of TJP1 was dramatically rescued by overexpression of TWIST1. Furthermore, TJP1 recruited USP2, which deubiquitinated TWIST1, thereby protecting TWIST1 from proteasome-mediated protein degradation. In conclusion, our results suggest that TJP1 controls angiogenesis in BLCA via TWIST1-dependent regulation of CCL2. We demonstrate that TJP1 functions as a scaffold for the interaction between USP2 and TWIST1 and this may provide potential therapeutic targets in bladder cancer.

Twist1 Influences the Expression of Leading Members of the IL-17 Signaling Pathway in HER2-Positive Breast Cancer Cells

Breast cancer (BC) is a heterogeneous disease composed of multiple subtypes with different molecular characteristics and clinical outcomes. The metastatic process in BC depends on the transcription factors (TFs) related to epithelial-mesenchymal transition (EMT), including the master regulator Twist1. However, its role beyond EMT in BC subtypes remains unclear. Our study aimed to investigate the role of Twist1, beyond EMT, in the molecular subtypes of BC. In patients, we observed the overexpression of TWIST1 in the HER2+ group. The silencing of TWIST1 in HER2+ BC cells resulted in the upregulation of 138 genes and the downregulation of 174 genes compared to control cells in a microarray assay. In silico analysis revealed correlations between Twist1 and important biological processes such as the Th17-mediated immune response, suggesting that Twist1 could be relevant for IL-17 signaling in HER2+ BC. IL-17 signaling was then examined, and it was shown that TWIST1 knockdown caused the downregulation of leading members of IL-17 signaling pathway. Taken together, our findings suggest that Twist1 plays a role on IL-17 signaling in HER2+ BC.

Clinical Significance of Serum Antithrombin III Activity After Hepatectomy for Hepatocellular Carcinoma

Background

As antithrombin III (AT-III) is produced in the hepatocytes, its serum activity decreases at the time of liver failure, in addition to ischemia reperfusion injury, vascular endothelial dysfunction, and disseminated intravascular coagulation (DIC). Here, we examined whether the serum AT-III value after hepatectomy could be a prognostic factor for hepatocellular carcinoma (HCC).

Methods

Of 141 patients who underwent hepatectomy for HCC, data for 101 patients in whom serum AT-III activity was measured on the first postoperative day were extracted. Patients with serum AT-III activity > 50% and ≤ 50% were assigned to high value (72 cases) and low value (29 cases) groups, respectively. We examined the clinical and prognostic differences between these two groups.

Results

The average age of enrolled patients (83 men and 18 women) was 68.0 years. The 5-year overall survival rate was 88% and 60% in the high and low value groups, respectively (P < 0.01). Furthermore, the 2-year relapse-free survival rate was 71% and 54% in the high and low value groups, respectively (P = 0.03).

Conclusion

This is the first study to demonstrate that serum AT-III levels on the first postoperative day may serve as a prognostic factor in HCC patients.

Early Prediction Model of Gestational Hypertension by Multi-Biomarkers Before 20 Weeks Gestation

BACKGROUND

Gestational hypertension (GH), a hypertensive disorder of pregnancy (HDP), is a leading cause of maternal and fetal mortality due to the lack of clarity on its exact etiology and clinically feasible prediction models. This study was performed to discover novel biomarkers before 20 weeks gestation and thereby construct an early GH prediction model.

METHODS

This study was designed based on differentially expressed protein screening followed by clinical validation. In the screening phase, a nested case-controlled study was conducted by plasma proteomic analyses using label-free LC-MS/MS and plasma samples from seven pre-GH cases before 20-week gestation and seven age- and gestational week-matched controls. In the validation phase, 10 proteins with differential expression in the screening phase were validated by ELISA or electrochemiluminescence in an independent study consisting of 29 pre-GH cases before 20-week gestation and 29 matched controls.

RESULTS

In the screening phase, 149 proteins were found to be differentially expressed between the two groups and were predominantly involved in complement and coagulation cascades, platelet degranulation and positive regulation of cell motility. Further validation showed that serpin family C member 1 (SERPINC1), serpin family A member 5 (SERPINA5), complement factor H-related protein 5 (CFHR5), clusterin, cytokeratin 18 (CK18) and histidine-rich glycoprotein (HRG) levels were significantly higher in women who later developed GH compared to women with uncomplicated pregnancies (P<0.05). Binary logistic regression analysis was used to determine the combination efficacy of models for early prediction of GH. The model with a combination of SERPINC1, CK18 and HRG had a significantly better discriminatory power (AUC = 0.91, 95% CI 0.83-0.98) compared to the models with those proteins alone as independent predictors of GH.

CONCLUSION

Plasma levels of SERPINC1, SERPINA5, CFHR5, clusterin, CK18 and HRG are potential novel predictive biomarkers of GH, and a prediction model using a combination of SERPINC1, CK18 and HRG has good discriminatory performance for GH before 20 weeks gestation.

Expression of Twist associated to microcirculation patterns of human glioma correlated with progression and survival of the patient

Twist is a transcription factor involved in the process of epithelial to mesenchymal transition (EMT) of carcinoma cells, and the promotion of invasion of gliomas through the mesenchymal adjusting process. However, its clinical significance in human glioma has not yet to be understood. To delineate the clinical-pathological significance and prognostic value of Twist, the expression of Twist was evaluated by Immunohistochemistry for 187 glioma samples. We found that Twist demonstrated frequent nuclear expression in the glioma samples and its expression levels were associated with tumor grade (P<0.001). Furthermore, high Twist expression was correlated with a poor outcome in patients with glioma (P=0.001), particularly with high grade glioma (P=0.026). Interestingly, Twist expression showed positive correlation with microvascular density (MVD) (r=0.145, P=0.048) as well as vasculogenic mimicry (VM) (r=0.273, P<0.001) in the tumors. These results suggest that Twist could be a predictor for poor prognosis in glioma patients. Additionally, Twist expression was associated with two major microcirculation patterns: endothelial-dependent vessels and VM in glioma, indicating that Twist could be a potential molecular target for anti-glioma therapy.

Over-expression of both VEGF-C and Twist predicts poor prognosis in human breast cancer

BACKGROUND

Angiogenesis is an indispensable step in the growth and invasiveness of breast cancers involving a series of exquisite molecular steps. Pro-angiogenic factors, including vascular endothelial growth factor (VEGF), have been recognized as pivotal therapeutic targets in the treatment of breast cancer. More recently, a highly conserved transcription factor Twist has been reported to be involved in tumor angiogenesis and metastasis.

METHODS

The expression of VEGF-C and Twist was immunohistochemically determined in tissue samples of primary tumors from 408 patients undergoing curative surgical resection for breast cancer. The correlations of VEGF-C and Twist expressions with clinicopathologic parameters as well as survival outcomes were evaluated.

RESULTS

Of the 408 patients evaluated, approximately 70% had high expression of VEGF-C which was significantly associated with advanced tumor stages (P = 0.019). Similarly, VEGF-C expression was associated with the proliferation index Ki67, N3 lymph node metastasis, and D2-40-positive lymphatic vessel invasion (LVI) in a univariate analysis. Furthermore, patients with high expressions of VEGF-C and Twist (V + T+) had significantly increased lymph node metastasis, higher clinical stage, and worse disease-free survival, DFS (P = 0.001) and overall survival, OS (P = 0.011).

CONCLUSIONS

Our results suggested that co-expression of VEGF-C and Twist was associated with larger tumor size, higher numbers of lymph node involvement, D2-40-positive LVI, higher risk of distant metastasis, and worse DFS or OS in breast cancer patients.

Multiple biological functions of Twist1 in various cancers

Twist1 is a well-known regulator of transcription during embryonic organogenesis in many species. In humans, Twist1 malfunction was first linked to Saethre-Chotzen syndrome and later identified to play an essential role in tumor initiation, stemness, angiogenesis, invasion, metastasis, and chemo-resistance in a variety of carcinomas, sarcomas, and hematological malignances. In this review, we will first focus on systematically elaborating the diverse pathological functions of Twist1 in various cancers, then delineating the intricate underlying network of molecular mechanisms, based on which we will summarize current therapeutic strategies in cancer treatment that target and modulate Twist1-involved signaling pathways. Most importantly, we will put special emphasis on revealing the independence and interdependency of these multiple biological functions of Twist1, piecing together the whole delicate picture of Twist1's diversified pathological roles in different cancers and providing new perspectives to guide future research.

Thrombin-unique coagulation system protein with multifaceted impacts on cancer and metastasis

The association between blood coagulation and cancer development is well recognized. Thrombin, the pleiotropic enzyme best known for its contribution to fibrin formation and platelet aggregation during vascular hemostasis, may also trigger cellular events through protease-activated receptors, PAR-1 and PAR-4, leading to cancer progression. Our pioneering findings provided evidence that thrombin contributes to cancer metastasis by increasing adhesive potential of malignant cells. However, there is evidence that thrombin regulates every step of cancer dissemination: (1) cancer cell invasion, detachment from primary tumor, migration; (2) entering the blood vessel; (3) surviving in vasculature; (4) extravasation; (5) implantation in host organs. Recent studies have provided new molecular data about thrombin generation in cancer patients and the mechanisms by which thrombin contributes to transendothelial migration, platelet/tumor cell interactions, angiogenesis, and other processes. Though a great deal is known regarding the role of thrombin in cancer dissemination, there are new data for multiple thrombin-mediated events that justify devoting focus to this topic with a comprehensive approach.

Roles and epigenetic regulation of epithelial-mesenchymal transition and its transcription factors in cancer initiation and progression

The epithelial-mesenchymal transition (EMT) is a crucial developmental process by which epithelial cells undergo a mesenchymal phenotypic change. During EMT, epigenetic mechanisms including DNA methylation and histone modifications are involved in the regulation of EMT-related genes. The epigenetic gene silencing of the epithelial marker E-cadherin has been well characterized. In particular, three major transcriptional repressors of E-cadherin, Snail, ZEB, and Twist families, also known as EMT-inducing transcription factors (EMT-TFs), play a crucial role in this process by cooperating with multiple epigenetic modifiers. Furthermore, recent studies have identified the novel epigenetic modifiers that control the expression of EMT-TFs, and these modifiers have emerged as critical regulators of cancer development and as novel therapeutic targets for human cancer. In this review, the diverse functions of EMT-TFs in cancer progression, the cooperative mechanisms of EMT-TFs with epigenetic modifiers, and epigenetic regulatory roles for the expression of EMT-TFs will be discussed.

Dabigatran antagonizes growth, cell-cycle progression, migration, and endothelial tube formation induced by thrombin in breast and glioblastoma cell lines

Thrombin activates its G-coupled seven transmembrane protease-activated receptor (PAR-1) by cleaving the receptor's N-terminal end. In several human cancers, PAR1 expression and activation correlates with tumor progression and metastatization. This provides compelling evidence for the effectiveness of an appropriate antithrombin agent for the adjuvant treatment of patients with cancer. Dabigatran is a selective direct thrombin inhibitor that reversibly binds to thrombin. In this study, we aimed to explore if dabigatran may affect mechanisms favoring tumor growth by interfering with thrombin-induced PAR-1 activation. We confirmed that exposure of tumor cells to thrombin significantly increased cell proliferation and this was coupled with downregulation of p27 and concomitant induction of cyclin D1. Dabigatran was consistently effective in antagonizing thrombin-induced proliferation as well as it restored the baseline pattern of cell cycle protein expression. Thrombin significantly upregulated the expression of proangiogenetic proteins like Twist and GRO-α in human umbilical vascular endothelial cells (HUVEC) cells and their expression was significantly brought down to control levels when dabigatran was added to culture. We also found that the chemoattractant effect of thrombin on tumor cells was lost in the presence of dabigatran, and that the thrombin antagonist was effective in dampening vascular tube formation induced by thrombin. Our data support a role of thrombin in inducing the proliferation, migration, and proangiogenetic effects of tumor cells in vitro. Dabigatran has activity in antagonizing all these effects, thereby impairing tumor growth and progression. In vivo models may help to understand the relevance of this pathway.

Quantitative proteomic analysis exploring progression of colorectal cancer: Modulation of the serpin family

Colorectal cancer (CRC) remains a major cause of cancer related-death in developed countries. The mortality risk is correlated with the stage of CRC determined at the primary diagnosis and early diagnosis is associated with enhanced survival rate. Currently, only faecal occult blood tests are used to screen for CRC. Consequently, there is an incentive to identify specific markers of CRC. We used quantitative proteomic analysis of serum samples to characterize protein profiles in adenoma, CRC and healthy control samples. We identified 89 distinct proteins modulated between normal, colorectal adenoma and carcinoma patients. This list emphasizes proteins involved in enzyme regulator activities and in particular the serpin family. In serum samples, protein profiles of three members of the serpin family (SERPINA1, SERPINA3 and SERPINC1) were confirmed by ELISA assays. We obtained sensitivity/specificity values of 95%/95% for both SERPINA1 and SERPINC1, and 95%/55% for SERPINA3. This study supports the idea that serum proteins can discriminate adenoma and CRC patients from unaffected patients and reveals a panel of regulated proteins that might be useful for selecting patients for colonoscopy. By evaluating SERPINA1, SERPINA3 and SERPINC1, we highlight the potential role of the serpin family during the development and progression of CRC.

SIGNIFICANCE

Colorectal cancer (CRC) remains a major cause of cancer mortality throughout the world. However, very few CRC biomarkers have satisfactory sensitivity and specificity in clinical practice. To the best of our knowledge our study is the first to profile sera proteomes between adenoma, CRC and healthy patients. We report a comprehensive list of proteins that may be used as early diagnostic biomarkers of CRC. It is noteworthy that 17% of these modulated proteins have been previously described as candidate biomarkers in CRC. Enzyme regulator activity was found to be the main molecular function among these proteins and, in particular, there was an enrichment of members of the serpin family. The subsequent verification on a new cohort by ELISA demonstrates that these serpins could be useful to discriminate healthy from colorectal carcinoma patients with a high sensitivity and specificity. The combination of these biomarkers should increase predictive powers of CRC diagnosis. The remaining candidates form a reserve for further evaluation of additional biomarkers for CRC diagnosis.

MACC-1 Promotes Endothelium-Dependent Angiogenesis in Gastric Cancer by Activating TWIST1/VEGF-A Signal Pathway

Endothelium-dependent angiogenesis is thought to be a crucial step in cancer progression. We previously reported that metastasis-associated in colon cancer-1 (MACC1) contributed to the vasculogenic mimicry in gastric cancer (GC), but it remains unknown whether MACC1 promotes endothelium-dependent angiogenesis of GC and whether TWIST1 is involved in this process. In the present study, we detected MACC1 expression and microvessel density (MVD) by immunohistochemistry in 159 patients with stage I-III GC, and investigated the role of TWIST1 and vascular endothelial growth factor A (VEGF-A) in MACC1-induced endothelium-dependent angiogenesis using nude mice with GC xenografts, and human umbilical vein endothelial cells (HUVECs) that were co-cultured with conditioned media from overexpression and interference MACC1 GC cells. We found that MACC1 expression was positively correlated with an increased MVD and tumor recurrence in GC patients. In GC xenograft models, MACC1 elevated MVD and upregulated the expression of VEGF-A as well as accelerated tumor growth. In addition, MACC1 obviously increased the expression of TWIST1 and induced tube-like formation of HUVECs, whereas attenuation of TWIST1 suppressed the protein expression of VEGF-A and repealed the effect of MACC1 on tube formation. Our findings shed light on the function of MACC1 in endothelium-dependent angiogenesis of GC and suggest potential prognostic and therapeutic value.

TWIST1 Polymorphisms Predict Survival in Patients with Metastatic Colorectal Cancer Receiving First-Line Bevacizumab plus Oxaliplatin-Based Chemotherapy

The epithelial-mesenchymal transition (EMT) is an important mechanism of resistance to angiogenesis inhibition. The ability of EMT pathway genetic variants to predict the efficacy of antiangiogenic therapy is unknown. We analyzed associations between functional SNPs in EMT-related genes and outcomes in metastatic colorectal cancer (mCRC) patients undergoing first-line bevacizumab-based chemotherapy. A total of 220 mCRC patients were included in this study: 143 patients treated with first-line bevacizumab-based chemotherapy (bevacizumab cohort) and 77 patients treated with cetuximab-based chemotherapy (cetuximab cohort). SNPs in TWIST1 (rs2285682, rs2285681), ZEB1 (rs10826943, rs2839658), SNAIL (rs1543442, rs4647958), and E-cadherin (rs16260) genes were analyzed by PCR-based direct sequencing. Patients carrying a TWIST1 rs2285682 G allele had a significantly longer median progression-free survival (PFS) of 18.1 months and overall survival (OS) of 44.1 months compared with those with the T/T genotype, who had a median PFS of 13.3 months (HR, 0.57; P = 0.003) and OS of 29.2 months (HR, 0.53; P = 0.001) in the bevacizumab cohort. In multivariate analysis, associations between TWIST1 rs2285682 and PFS and OS remained significant. Among women, the G allele of TWIST1 rs2285682 (PFS HR, 0.39; P = 0.007; OS HR, 0.30; P = 0.001) and TWIST1 rs2285681 (PFS HR, 0.27; P < 0.001; OS HR, 0.25; P < 0.001) was associated with improved survival. No significant associations were found in the cetuximab cohort. Our findings suggest that TWIST1 polymorphisms are associated with survival in mCRC patients treated with first-line bevacizumab-based chemotherapy and may serve as clinically useful biomarkers for antiangiogenic therapy. Mol Cancer Ther; 15(6); 1405-11. ©2016 AACR.

Inhibition of the STAT3 signaling pathway contributes to apigenin-mediated anti-metastatic effect in melanoma

Signal transducer and activator of transcription 3 (STAT3) signaling is constantly activated in human melanoma, and promotes melanoma metastasis. The dietary flavonoid apigenin is a bioactive compound that possesses low toxicity and exerts anti-metastatic activity in melanoma. However, the anti-metastasis mechanism of apigenin has not been fully elucidated. In the present study, we showed that apigenin suppressed murine melanoma B16F10 cell lung metastasis in mice, and inhibited cell migration and invasion in human and murine melanoma cells. Further study indicated that apigenin effectively suppressed STAT3 phosphorylation, decreased STAT3 nuclear localization and inhibited STAT3 transcriptional activity. Apigenin also down-regulated STAT3 target genes MMP-2, MMP-9, VEGF and Twist1, which are involved in cell migration and invasion. More importantly, overexpression of STAT3 or Twist1 partially reversed apigenin-impaired cell migration and invasion. Our data not only reveal a novel anti-metastasis mechanism of apigenin but also support the notion that STAT3 is an attractive and promising target for melanoma treatment.

Platelets and their role in cancer evolution and immune system

Platelets are anucleate fragments formed from the cytoplasm of megakaryocytes and represent the smallest circulating hematopoietic cells. Thought for almost a century to possess solely hemostatic potentials, platelets actually play a much wider role in tissue regeneration and repair and interact intimately with tumor cells. On the one hand, tumor cells induce platelet aggregation, known to act as the trigger of cancer-associated thrombosis and on the other hand, platelets recruited to the tumor microenvironment interact directly with tumor cells favoring proliferation, and indirectly through the release of angiogenic and mitogenic proteins. Furthermore, platelets are immunosuppressive cells that protect metastatic cancer cells from surveillance by killer cells, nullifying the effects of immunotherapy.

A Clinical Indications Prediction Scale Based on TWIST1 for Human Mesenchymal Stem Cells

In addition to their stem/progenitor properties, mesenchymal stem cells (MSCs) also exhibit potent effector (angiogenic, antiinflammatory, immuno-modulatory) functions that are largely paracrine in nature. It is widely believed that effector functions underlie most of the therapeutic potential of MSCs and are independent of their stem/progenitor properties. Here we demonstrate that stem/progenitor and effector functions are coordinately regulated at the cellular level by the transcription factor Twist1 and specified within populations according to a hierarchical model. We further show that manipulation of Twist1 levels by genetic approaches or by exposure to widely used culture supplements including fibroblast growth factor 2 (Ffg2) and interferon gamma (IFN-gamma) alters MSC efficacy in cell-based and in vivo assays in a predictable manner. Thus, by mechanistically linking stem/progenitor and effector functions our studies provide a unifying framework in the form of an MSC hierarchy that models the functional complexity of populations. Using this framework, we developed a CLinical Indications Prediction (CLIP) scale that predicts how donor-to-donor heterogeneity and culture conditions impact the therapeutic efficacy of MSC populations for different disease indications.

•

Mesenchymal stem cells exhibit stem/progenitor and effector (angiogenic, anti-inflammatory, immuno-modulatory) functions.

•

Twist1 coordinately regulates stem/progenitor and effector functions, which are specified hierarchically in populations.

•

Twist1 levels predict inter-population differences in therapeutic efficacy of mesenchymal stem cells for different disease indications.

Mesenchymal stem cells are being evaluated in human clinical trials for treating ischemic, inflammatory, and immunological diseases. However, most completed trials have yielded suboptimal outcomes due to the inability to predict the potency of different donor populations, which are functionally heterogeneous. We demonstrate that clinically relevant biological activities of MSCs are coordinately regulated by the transcription factor Twist1. Furthermore, we showed that TWIST1 levels reliably predict differences in the angiogenic, anti-inflammatory, and immuno-modulatory activity of populations and as such used it to develop a Clinical Indications Prediction (CLIP) scale. By predicting potency of MSC populations for different disease indications the CLIP scale is expected to dramatically improve MSC-based clinical trial outcomes.

Endothelial TWIST1 promotes pathological ocular angiogenesis

PURPOSE

Pathological neovessel formation impacts many blinding vascular eye diseases. Identification of molecular signatures distinguishing pathological neovascularization from normal quiescent vessels is critical for developing new interventions. Twist-related protein 1 (TWIST1) is a transcription factor important in tumor and pulmonary angiogenesis. This study investigated the potential role of TWIST1 in modulating pathological ocular angiogenesis in mice.

METHODS

Twist1 expression and localization were analyzed in a mouse model of oxygen-induced retinopathy (OIR). Pathological ocular angiogenesis in Tie2-driven conditional Twist1 knockout mice were evaluated in both OIR and laser-induced choroidal neovascularization models. In addition, the effects of TWIST1 on angiogenesis and endothelial cell function were analyzed in sprouting assays of aortic rings and choroidal explants isolated from Twist1 knockout mice, and in human retinal microvascular endothelial cells treated with TWIST1 small interfering RNA (siRNA).

RESULTS

TWIST1 is highly enriched in pathological neovessels in OIR retinas. Conditional Tie2-driven depletion of Twist1 significantly suppressed pathological neovessels in OIR without impacting developmental retinal angiogenesis. In a laser-induced choroidal neovascularization model, Twist1 deficiency also resulted in significantly smaller lesions with decreased vascular leakage. In addition, loss of Twist1 significantly decreased vascular sprouting in both aortic ring and choroid explants. Knockdown of TWIST1 in endothelial cells led to dampened expression of vascular endothelial growth factor receptor 2 (VEGFR2) and decreased endothelial cell proliferation.

CONCLUSIONS

Our study suggests that TWIST1 is a novel regulator of pathologic ocular angiogenesis and may represent a new molecular target for developing potential therapeutic treatments to suppress pathological neovascularization in vascular eye diseases.

The basic helix-loop-helix (bHLH) transcription factor DEC2 negatively regulates Twist1 through an E-box element

Differentiated embryo chondrocyte 2 (DEC2/Sharp-1/Bhlhe41), a basic helix-loop-helix (bHLH) transcription factor, has been shown to regulate the transcription of target genes by binding to their E-box elements. We identified a possible DEC2-response element (consensus E-box: CACGTG) in the promoter region of Twist1. Forced expression of DEC2 significantly repressed Twist1 promoter activity under normoxia and under hypoxia as assessed by a luciferase reporter assay. In addition, over-expression of DEC2 repressed Twist1 mRNA expression assessed by quantitative real-time PCR. Site-directed mutagenesis studies showed that mutagenesis of the consensus E-box sequence eliminated the ability of DEC2 to reduce the Twist1 promoter activity. Chromatin immunoprecipitation (ChIP) assays confirmed that the DEC2-mediated repression is primarily achieved by binding to the E-box in the Twist1 promoter. Knockdown of DEC2 by siRNA significantly attenuated the repression of Twist1 expression. DEC2 and Twist1 exhibit inversed protein expression patterns during development of mouse tongue embryo tissue. Given the fact that DEC2 protein is emerging as an important regulator in a vast array of cellular events, including cell differentiation, maturation of lymphocytes and the molecular clock, our study elucidates an important mechanism by which DEC2 regulates cellular function by modulating the expression of Twist1.

Gonadotropin stimulation in mice leads to ovarian accumulation of immature myeloid cells and altered expression of proangiogenic genes

OBJECTIVE

Ovarian hyperstimulation syndrome is associated with increased angiogenesis and vascular leakage. Immature myeloid cells (IMCs) and dendritic cells have been shown to be actively involved in angiogenesis in several disease models in mice and humans. Nevertheless, little is known about the role of these cells in the ovary. As such, this study sought to determine whether alterations in these ovarian myeloid cell populations are associated with gonadotropin stimulation in a mouse model.

STUDY DESIGN

Four-week-old pre-pubertal C57Bl/6 female mice were allocated into three groups: high-dose stimulation (n=4; pregnant mare serum gonadotropins (PMSG) 20U for 2 days), low-dose stimulation (n=5; PMSG 5U for 1 day) and sham-treated controls (n=4). Human chorionic gonadotropin 5U was injected on Day 3, and the mice were killed on Day 5. Ovaries were analysed by flow cytometry, confocal microscopy and quantitative polymerase chain reaction.

RESULTS

Gonadotropin stimulation increased the proportion of CD11b(+)Gr1(+) IMCs among the ovarian myeloid cells: 22.6±8.1% (high dose), 7.2±1.6% (low dose) and 4.1±0.3% (control) (p=0.02). Conversely, gonadotropin stimulation decreased the proportion of ovarian CD11c(+)MHCII(+) dendritic cells: 15.1±1.9% (high dose), 20.7±4.8% (low dose) and 27.3±8.2% (control) (p=0.02). IMCs, unlike dendritic cells, were localized adjacent to PECAM1(+) endothelial cells. Finally, gonadotropin stimulation was associated with increased expression of S100A8, S100A9, Vcan and Dmbt1, and decreased expression of MMP12.

CONCLUSIONS

Gonadotropin stimulation is associated with proangiogenic myeloid cell alterations, reflected by a dose-dependent increase in ovarian IMCs and a parallel decrease in dendritic cells. Recruited IMCs localize strategically at sites of angiogenesis. These changes are associated with differential expression of key proangiogenic genes.

NETosis: a new factor in tumor progression and cancer-associated thrombosis

Neutrophils have long been known as innate immune cells that phagocytose and kill pathogens and mount inflammatory responses protecting the host from infection. In the past decades, new aspects of neutrophils have emerged unmasking their importance not only in inflammation but also in many pathological conditions including thrombosis and cancer. The 2004 discovery that neutrophils, upon strong activation, release decondensed chromatin to form neutrophil extracellular traps (NETs), has unveiled new avenues of research. Here, we review current knowledge regarding NETs in thrombosis, with a special focus on cancer-associated thrombosis as well as their potential role in cancer growth and metastasis. We discuss the prospective use of NET-specific biomarkers, such as citrullinated histone H3 and NET inhibitors, as tools to anticipate and fight cancer-associated thrombosis. We propose that the rapid developments in the field of NETosis may provide new targets to combat the thrombotic consequences of cancer and perhaps even help to contain the disease itself.

Twist1 controls lung vascular permeability and endotoxin-induced pulmonary edema by altering Tie2 expression

Tight regulation of vascular permeability is necessary for normal development and deregulated vascular barrier function contributes to the pathogenesis of various diseases, including acute respiratory distress syndrome, cancer and inflammation. The angiopoietin (Ang)-Tie2 pathway is known to control vascular permeability. However, the mechanism by which the expression of Tie2 is regulated to control vascular permeability has not been fully elucidated. Here we show that transcription factor Twist1 modulates pulmonary vascular leakage by altering the expression of Tie2 in a context-dependent way. Twist1 knockdown in cultured human lung microvascular endothelial cells decreases Tie2 expression and phosphorylation and increases RhoA activity, which disrupts cell-cell junctional integrity and increases vascular permeability in vitro. In physiological conditions, where Ang1 is dominant, pulmonary vascular permeability is elevated in the Tie2-specific Twist1 knockout mice. However, depletion of Twist1 and resultant suppression of Tie2 expression prevent increase in vascular permeability in an endotoxin-induced lung injury model, where the balance of Angs shifts toward Ang2. These results suggest that Twist1-Tie2-Angs signaling is important for controlling vascular permeability and modulation of this mechanism may lead to the development of new therapeutic approaches for pulmonary edema and other diseases caused by abnormal vascular permeability.

Pathologies at the nexus of blood coagulation and inflammation: thrombin in hemostasis, cancer, and beyond

Thrombin is the protease involved in blood coagulation. Its deregulation can lead to hemostatic abnormalities, which range from subtle subclinical to serious life-threatening coagulopathies, i.e., during septicemia. Additionally, thrombin plays important roles in many (patho)physiological conditions that reach far beyond its well-established role in stemming blood loss and thrombosis, including embryonic development and angiogenesis but also extending to inflammatory processes, complement activation, and even tumor biology. In this review, we will address thrombin's broad roles in diverse (patho)physiological processes in an integrative way. We will also discuss thrombin as an emerging major target for novel therapies.

Mesenchymal CD44 expression contributes to the acquisition of an activated fibroblast phenotype via TWIST activation in the tumor microenvironment

Tumor-stroma interactions play a crucial role in cancer progression by eliciting factors that promote proliferative, angiogenic, and invasive supports to the tumor microenvironment. Mesenchymal stromal/stem cells (MSC) contribute to stroma in part as cancer-associated fibroblasts (CAF), but a complete understanding of how MSC contribute to the tumor stroma is lacking. In this study, we show how CAF phenotypes rely upon MSC expression of the multifunctional cell surface glycoprotein CD44, a putative stem cell marker. Through bone marrow transplantation experiments in a transgenic mouse model of cancer, we determined that CD44 deficiency leads to a relative reduction in the contribution of bone marrow-derived cells to tumor stroma. CD44 attenuation in MSC limited their expression of CAF markers induced by tumor conditioning, and these MSC migrated poorly and provided weak angiogenic support compared with wild-type MSC. These defects were linked to deficiencies in the ability of CD44-attenuated MSC to transcriptionally upregulate Twist expression. Together, our results establish that CD44 expression contributes to critical functions in the tumor stroma.

Twist1 induces CCL2 and recruits macrophages to promote angiogenesis

The transcription factor Twist1 induces epithelial-mesenchymal transition and extracellular matrix degradation to promote tumor metastasis. Although Twist1 also plays a role in embryonic vascular development and tumor angiogenesis, the molecular mechanisms that underlie these processes are not as well understood. Here, we report a novel function for Twist1 in modifying the tumor microenvironment to promote progression. We found that expression of Twist1 in human mammary epithelial cells potently promoted angiogenesis. Surprisingly, Twist1 expression did not increase the secretion of the common proangiogenic factors VEGF and basic fibroblast growth factor but rather induced expression of the macrophage chemoattractant CCL2. Attenuation of endogenous Twist1 in vivo blocked macrophage recruitment and angiogenesis, whereas exogenous CCL2 rescued the ability of tumor cells lacking Twist1 to attract macrophages and promote angiogenesis. Macrophage recruitment also was essential for the ability of Twist1-expressing cells to elicit a strong angiogenic response. Together, our findings show that how Twist1 recruits stromal macrophages through CCL2 induction to promote angiogenesis and tumor progression. As Twist1 expression has been associated with poor survival in many human cancers, this finding suggests that anti-CCL2 therapy may offer a rational strategy to treat Twist1-positive metastatic cancers.

ARTEMIN promotes de novo angiogenesis in ER negative mammary carcinoma through activation of TWIST1-VEGF-A signalling

The neurotrophic factor ARTEMIN (ARTN) has been reported to possess a role in mammary carcinoma progression and metastasis. Herein, we report that ARTN modulates endothelial cell behaviour and promotes angiogenesis in ER-mammary carcinoma (ER-MC). Human microvascular endothelial cells (HMEC-1) do not express ARTN but respond to exogenously added, and paracrine ARTN secreted by ER-MC cells. ARTN promoted endothelial cell proliferation, migration, invasion and 3D matrigel tube formation. Angiogenic behaviour promoted by ARTN secreted by ER-MC cells was mediated by AKT with resultant increased TWIST1 and subsequently VEGF-A expression. In a patient cohort of ER-MC, ARTN positively correlated with VEGF-A expression as measured by Spearman’s rank correlation analysis. In xenograft experiments, ER-MC cells with forced expression of ARTN produced tumors with increased VEGF-A expression and increased microvessel density (CD31 and CD34) compared to tumors formed by control cells. Functional inhibition of ARTN by siRNA decreased the angiogenic effects of ER-MC cells. Bevacizumab (a humanized monoclonal anti-VEGF-A antibody) partially inhibited the ARTN mediated angiogenic effects of ER-MC cells and combined inhibition of ARTN and VEGF-A by the same resulted in further significant decrease in the angiogenic effects of ER-MC cells. Thus, ARTN stimulates de novo tumor angiogenesis mediated in part by VEGF-A. ARTN therefore co-ordinately regulates multiple aspects of tumor growth and metastasis.

EMT-activating transcription factors in cancer: beyond EMT and tumor invasiveness

Cancer is a complex multistep process involving genetic and epigenetic changes that eventually result in the activation of oncogenic pathways and/or inactivation of tumor suppressor signals. During cancer progression, cancer cells acquire a number of hallmarks that promote tumor growth and invasion. A crucial mechanism by which carcinoma cells enhance their invasive capacity is the dissolution of intercellular adhesions and the acquisition of a more motile mesenchymal phenotype as part of an epithelial-to-mesenchymal transition (EMT). Although many transcription factors can trigger it, the full molecular reprogramming occurring during an EMT is mainly orchestrated by three major groups of transcription factors: the ZEB, Snail and Twist families. Upregulated expression of these EMT-activating transcription factors (EMT-ATFs) promotes tumor invasiveness in cell lines and xenograft mice models and has been associated with poor clinical prognosis in human cancers. Evidence accumulated in the last few years indicates that EMT-ATFs also regulate an expanding set of cancer cell capabilities beyond tumor invasion. Thus, EMT-ATFs have been shown to cooperate in oncogenic transformation, regulate cancer cell stemness, override safeguard programs against cancer like apoptosis and senescence, determine resistance to chemotherapy and promote tumor angiogenesis. This article reviews the expanding portfolio of functions played by EMT-ATFs in cancer progression.

Snail promotes lymph node metastasis and Twist enhances tumor deposit formation through epithelial-mesenchymal transition in colorectal cancer

Snail and Twist, transcriptional repressors of E-cadherin as well as inducers of epithelial-mesenchymal transition, play pivotal roles in tumor invasion and metastasis. We investigated the expression of Snail, Twist, and E-cadherin by immunohistochemistry in 193 colorectal cancers, including 79 with positive lymph nodes, 36 with tumor deposits, 39 with both, and 39 with no metastases. Snail was expressed to a greater extent in the group with positive lymph nodes (68.4%), whereas Twist was overexpressed in patients with other metastases (75.0%). Ectopic expression of Snail and Twist correlated with reduced membranous expression of E-cadherin. Importantly, Snail overexpression correlated significantly with lymph node metastasis (P < .0001), whereas Twist up-regulation correlated strongly with other metastases (P < .0001). Multivariate logistic regression analysis showed that Snail was an independent predictor of lymph node metastasis (odds ratio, 4.445; 95% confidence interval, 2.250-8.781; P < .0001), whereas Twist displayed predictive value for metastasis formation (odds ratio, 5.606; 95% confidence interval, 2.829-11.111; P < .0001), suggesting that lymph node and other metastases may follow different signaling pathways. In conclusion, ectopic expression of Snail and Twist contributed to lymph node and disseminated metastasis, respectively, by reducing E-cadherin expression, providing a novel role for Snail and Twist in the progression of colorectal cancer.

Prognostic significance of antithrombin III levels for outcomes in patients with hepatocellular carcinoma after curative hepatectomy

BACKGROUND

Although several studies have shown that serum antithrombin III (ATIII) has anti-inflammatory effects, the prognostic value of ATIII in HCC is unknown. We investigated the influence of preoperative ATIII levels on the outcome of patients who underwent hepatectomy for hepatocellular carcinoma (HCC).

METHODS

Data from 440 patients (314 patients with ATIII ≥ 70 % and 126 patients with ATIII <70 %) who underwent curative hepatectomy for HCC were retrospectively collected and analyzed. To overcome bias due to the different distribution of covariates for the 2 groups, propensity score matching was performed on the patients, and outcomes were compared.

RESULTS

The propensity score analysis revealed that 65 patients with ATIII of ≥ 70 % (group 1) and 65 patients with ATIII of <70 % (group 2) had the same preoperative and operative characteristics (excluding the ATIII level). The overall survival rate and the disease-free survival rate was significantly higher in group 1 than in group 2 (P = 0.005 and 0.011, respectively). Multivariate analysis showed that ATIII was a significant favorable factor for overall survival and disease-free survival of patients with HCC after curative hepatectomy.

CONCLUSIONS

The prognosis of patients with HCC was found to be associated with preoperative antithrombin III levels. ATIII may be useful for predicting outcomes of patients with HCC after curative hepatectomy.

Activator protein-1 involvement in proliferation inhibition by gene silencing of Twist in gastric cancer cells

AIMS

To study the role of the Twist gene in growth of gastric cancer cell line MKN45 and the possible mechanisms involved.

METHODS

Human gastric carcinoma MKN45 cells were stably transfected with Twist antisense plasmid using the lipofectamine transfection technique. Expression of Twist in Twist antisense plasmid transfected cells (TwistAS), non-transfected cells (NT) and non-specific Twist antisense plasmid transfected cells (CON) were examined by Western blotting. Cell growth ability in vitro was evaluated by MTT and clone formation assays. Xenograft cancer models were established by nude mouse transfer method. Activator protein-1 (AP-1) DNA binding activity was measured by electrophoretic mobility shift assay (EMSA). The expression of c-Jun and c-Fos were examined by Western blotting. The mRNA level of cyclin D1 was detected by RT-PCR.

RESULTS

TwistAS inhibited cell growth and proliferation. In vitro, the cloning efficiency of TwistAS cells (8.0  ±  0.6%) was significantly lower compared to that in NT (26.5  ±  1.1%) and CON (22.7  ±  1.2%). In vivo, the average tumour weight was lighter in the TwistAS group (425.3  ±  20.8  mg) compared with the CON group (1217.0  ±  50.2  mg) and the NT group (1120.6  ±  75  mg). TwistAS inhibited AP-1 activity in MKN45 cells (15.3  ±  3.2% versus 50.2  ±  3.6% and 52.4  ±  3.8%). TwistAS inhibited the expression of c-Fos in MKN45 cells (20.4  ±  3.8% versus 72.5  ±  3.6% and 75.3  ±  4.0%) but not c-Jun (p < 0.05). cyclin D1 mRNA level was significantly lower in TwistAS cells (40.5  ±  3.8%) than that in CON (132  ±  5.4%) and NT cells (130  ±  5.2%).

CONCLUSIONS

This study demonstrated that down-regulation of the Twist gene suppressed the proliferation of MKN45 gastric cancer cells by negatively regulating the AP-1 activity resulting in the cyclin D1 mRNA level decreasing.

Megakaryocytes, malignancy and bone marrow vascular niches

Dynamic interactions between hematopoietic cells and their specialized bone marrow microenvironments, namely the vascular and osteoblastic 'niches', regulate hematopoiesis. The vascular niche is conducive for thrombopoiesis and megakaryocytes may, in turn, regulate the vascular niche, especially in supporting vascular and hematopoietic regeneration following irradiation or chemotherapy. A role for platelets in tumor growth and metastasis is well established and, more recently, the vascular niche has also been implicated as an area for preferential homing and engraftment of malignant cells. This article aims to provide an overview of the dynamic interactions between cellular and molecular components of the bone marrow vascular niche and the potential role of megakaryocytes in bone marrow malignancy.

Normal and disease-related biological functions of Twist1 and underlying molecular mechanisms

This article reviews the molecular structure, expression pattern, physiological function, pathological roles and molecular mechanisms of Twist1 in development, genetic disease and cancer. Twist1 is a basic helix-loop-helix domain-containing transcription factor. It forms homo- or hetero-dimers in order to bind the Nde1 E-box element and activate or repress its target genes. During development, Twist1 is essential for mesoderm specification and differentiation. Heterozygous loss-of-function mutations of the human Twist1 gene cause several diseases including the Saethre-Chotzen syndrome. The Twist1-null mouse embryos die with unclosed cranial neural tubes and defective head mesenchyme, somites and limb buds. Twist1 is expressed in breast, liver, prostate, gastric and other types of cancers, and its expression is usually associated with invasive and metastatic cancer phenotypes. In cancer cells, Twist1 is upregulated by multiple factors including SRC-1, STAT3, MSX2, HIF-1α, integrin-linked kinase and NF-κB. Twist1 significantly enhances epithelial-mesenchymal transition (EMT) and cancer cell migration and invasion, hence promoting cancer metastasis. Twist1 promotes EMT in part by directly repressing E-cadherin expression by recruiting the nucleosome remodeling and deacetylase complex for gene repression and by upregulating Bmi1, AKT2, YB-1, etc. Emerging evidence also suggests that Twist1 plays a role in expansion and chemotherapeutic resistance of cancer stem cells. Further understanding of the mechanisms by which Twist1 promotes metastasis and identification of Twist1 functional modulators may hold promise for developing new strategies to inhibit EMT and cancer metastasis.

Heparin impairs angiogenesis through inhibition of microRNA-10b

Heparin, which has been used as an anticoagulant drug for decades, inhibits angiogenesis, whereas thrombin promotes tumor-associated angiogenesis. However, the mechanisms underlying the regulation of angiogenesis by heparin and thrombin are not well understood. Here, we show that microRNA-10b (miR-10b) is down-regulated by heparin and up-regulated by thrombin in human microvascular endothelial cells (HMEC-1). Overexpression of miR-10b induces HMEC-1 cell migration, tube formation, and angiogenesis, and down-regulates homeobox D10 (HoxD10) expression via direct binding of miR-10b to the putative 3' UTR of HoxD10. In addition, HMEC-1 cell migration and tube formation are induced by HoxD10 knockdown, whereas angiogenesis is arrested when HoxD10 expression is increased after anti-miR-10b or heparin treatments. Furthermore, expression of miR-10b and its transcription factor Twist are up-regulated by thrombin, whereas HoxD10 expression is impaired by thrombin. Using quartz crystal microbalance analysis, we show that heparin binds to thrombin, thereby inhibiting thrombin-induced expression of Twist and miR-10b. However, the expression of miR-10b is not attenuated by heparin any more after thrombin expression is silenced by its siRNA. Interestingly, we find that heparin attenuates miR-10b expression and induces HoxD10 expression in vivo to inhibit angiogenesis and impair the growth of MDA-MB-231 tumor xenografts. These results provide insight into the molecular mechanism by which heparin and thrombin regulate angiogenesis.

Endogenous activated protein C is essential for immune-mediated cancer cell elimination from the circulation

Fibrinogen and platelets play an important role in cancer cell survival in the circulation by protecting cancer cells from the immune system. Moreover, endogenous activated protein C (APC) limits cancer cell extravasation due to sphingosine-1-phosphate receptor-1 (S(1)P(1)) and VE-cadherin-dependent vascular barrier enhancement. We aimed to study the relative contribution of these two mechanisms in secondary tumor formation in vivo. We show that fibrinogen depletion limits pulmonary tumor foci formation in an experimental metastasis model in C57Bl/6 mice but not in NOD-SCID mice lacking a functional immune system. Moreover, we show that in the absence of endogenous APC, fibrinogen depletion does not prevent cancer cell dissemination and secondary tumor formation in immune-competent mice. Overall, we thus show that endogenous APC is essential for immune-mediated cancer cell elimination.

Thrombin induces expression of twist and cell motility via the hypoxia-inducible factor-1α translational pathway in colorectal cancer cells

Deep vein thrombosis associated with advanced cancer is known as Trousseau's syndrome. We hypothesized that thrombin, an activator of protease-activated receptor (PAR)-1 and PAR-4 contributes to tumor metastasis. In this study, we demonstrated that thrombin and the PAR-1 activating peptide (AP) SFLLRN, but not the PAR-4 AP GYPGKF, induced HIF-1α activities, protein expression, and cell motility in colorectal cancer cells, and these actions were significantly inhibited by the PAR-1 antagonist SCH79797. Moreover, thrombin-induced HIF-1α activity and cell motility were blocked by inhibiting important mediators of signaling transduction, including the ERK, PI3K, and mTOR pathways. These results showed that thrombin induced HIF-1α protein expression through PAR-1 and HIF-1α translational de novo protein synthesis. Twist can regulate epithelial-mesenchymal transition (EMT) and increase tumor metastasis. However, we observed that thrombin-induced HIF-1α increased Twist mRNA and its protein level was mediated by the modulation of PAR-1 activation and the HIF-1α translational pathway. In addition, Twist could increase N-cadherin but not E-cadherin to promote tumor metastasis. Overexpression of dominant-negative HIF-1α reversed thrombin-mediated Twist and Twist-induced N-cadherin expression. Moreover, siTwist inhibited Twist-induced N-cadherin and Thrombin-induced cell motility. In conclusion, our study showed that thrombin-induced HIF-1α upregulated Twist at the transcriptional level to enhance cell motility. These findings show that thrombin upregulates Twist via HIF-1α to make tumor cells malignant and also establish a link between the coagulation disorder and cancer metastasis.

Contribution of platelets to tumour metastasis

Extensive experimental evidence shows that platelets support tumour metastasis. The activation of platelets and the coagulation system have a crucial role in the progression of cancer. Within the circulatory system, platelets guard tumour cells from immune elimination and promote their arrest at the endothelium, supporting the establishment of secondary lesions. These contributions of platelets to tumour cell survival and spread suggest platelets as a new avenue for therapy.

G protein-coupled receptors: novel targets for drug discovery in cancer

G protein-coupled receptors (GPCRs) belong to a superfamily of cell surface signalling proteins that have a pivotal role in many physiological functions and in multiple diseases, including the development of cancer and cancer metastasis. Current drugs that target GPCRs - many of which have excellent therapeutic benefits - are directed towards only a few GPCR members. Therefore, huge efforts are currently underway to develop new GPCR-based drugs, particularly for cancer. We review recent findings that present unexpected opportunities to interfere with major tumorigenic signals by manipulating GPCR-mediated pathways. We also discuss current data regarding novel GPCR targets that may provide promising opportunities for drug discovery in cancer prevention and treatment.

Abnormal fibrillin-1 expression and chronic oxidative stress mediate endothelial mesenchymal transition in a murine model of systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune connective tissue disorder characterized by oxidative stress, impaired vascular function, and attenuated angiogenesis. The tight-skin (Tsk(-/+)) mouse is a model of SSc that displays many of the cellular features of the clinical disease. We tested the hypotheses that abnormal fibrillin-1 expression and chronic phospholipid oxidation occur in Tsk(-/+) mice and, furthermore, that these factors precipitate a prooxidant state, collagen-related protein expression, apoptosis, and mesenchymal transition in endothelial cells cultured on Tsk(-/+) extracellular matrix. Human umbilical vein endothelial cells were seeded on microfibrils isolated from skin of C57BL/6J (control) and Tsk(-/+) mice in the presence or absence of chronic pretreatment with the apolipoprotein Apo A-I mimetic D-4F (1 mg·kg(-1)·day(-1) ip for 6 to 8 wk). Nitric oxide-to-superoxide anion ratio was assessed 12 h after culture, and cell proliferation, apoptosis, and phenotype were studied 72 h after culture. Tsk(-/+) mice demonstrated abnormal "big fibrillin" expression (405 kDa) by Western blot analysis compared with control. Endothelial cells cultured on microfibrils prepared from Tsk(-/+) mice demonstrated reduced proliferation, a prooxidant state (reduced nitric oxide-to-superoxide anion ratio), increased apoptosis, and collagen-related protein expression associated with mesenchymal transition. Chronic D-4F pretreatment of Tsk(-/+) mice attenuated many of these adverse effects. The findings demonstrate that abnormal fibrillin-1 expression and chronic oxidative stress mediate endothelial mesenchymal transition in Tsk(-/+) mice. This mesenchymal transition may contribute to the reduction in angiogenesis that is known to occur in this model of SSc.

Platelets: linking hemostasis and cancer

Platelets are the main cellular component in blood responsible for maintaining the integrity of the cardiovascular system via hemostasis. Platelet dysfunction contributes to a wide range of obvious pathological conditions, such as bleeding or thrombosis, but normal platelet function is also linked to diseases not immediately associated with hemostasis or thrombosis, such as cancer. Since the description of Trousseau syndrome in 1865, various experimental and clinical studies have detailed the interaction of platelets with primary tumors and circulating metastatic tumor cells. Observations have suggested that platelets not only augment the growth of primary tumors via angiogenesis but endow tumor cells physical and mechanical support to evade the immune system and extravasate to secondary organs, the basis of metastatic disease. Many laboratory and animal studies have identified specific targets for antiplatelet therapy that may be advantageous as adjuncts to existing cancer treatments. In this review, we summarize important platelet properties that influence tumorigenesis, including primary tumor growth and metastasis at the molecular level. The studies provide a link between the well-studied paradigms of platelet hemostasis and tumorigenesis.

Bypass mechanisms of the androgen receptor pathway in therapy-resistant prostate cancer cell models

BACKGROUND

Prostate cancer is initially dependent on androgens for survival and growth, making hormonal therapy the cornerstone treatment for late-stage tumors. However, despite initial remission, the cancer will inevitably recur. The present study was designed to investigate how androgen-dependent prostate cancer cells eventually survive and resume growth under androgen-deprived and antiandrogen supplemented conditions. As model system, we used the androgen-responsive PC346C cell line and its therapy-resistant sublines: PC346DCC, PC346Flu1 and PC346Flu2.

METHODOLOGY/PRINCIPAL FINDINGS

Microarray technology was used to analyze differences in gene expression between the androgen-responsive and therapy-resistant PC346 cell lines. Microarray analysis revealed 487 transcripts differentially-expressed between the androgen-responsive and the therapy-resistant cell lines. Most of these genes were common to all three therapy-resistant sublines and only a minority (∼5%) was androgen-regulated. Pathway analysis revealed enrichment in functions involving cellular movement, cell growth and cell death, as well as association with cancer and reproductive system disease. PC346DCC expressed residual levels of androgen receptor (AR) and showed significant down-regulation of androgen-regulated genes (p-value = 10(-7)). Up-regulation of VAV3 and TWIST1 oncogenes and repression of the DKK3 tumor-suppressor was observed in PC346DCC, suggesting a potential AR bypass mechanism. Subsequent validation of these three genes in patient samples confirmed that expression was deregulated during prostate cancer progression.

CONCLUSIONS/SIGNIFICANCE

Therapy-resistant growth may result from adaptations in the AR pathway, but androgen-independence may also be achieved by alternative survival mechanisms. Here we identified TWIST1, VAV3 and DKK3 as potential players in the bypassing of the AR pathway, making them good candidates as biomarkers and novel therapeutical targets.

Suppression of Her2/neu expression through ILK inhibition is regulated by a pathway involving TWIST and YB-1

In a previous study it was found that the therapeutic effects of QLT0267, a small molecule inhibitor of integrin-linked kinase (ILK), were influenced by Her2/neu expression. To understand how inhibition or silencing of ILK influences Her2/neu expression, Her2/neu signaling was evaluated in six Her2/neu-positive breast cancer cell lines (LCC6^Her2, MCF7^Her2, SKBR3, BT474, JIMT-1 and KPL-4). Treatment with QLT0267 engendered suppression (32–87%) of total Her2/neu protein in these cells. Suppression of Her2/neu was also observed following small interfering RNA-mediated silencing of ILK expression. Time course studies suggest that ILK inhibition or silencing caused transient decreases in P-AKT^ser473, which were not temporally related to Her2/neu downregulation. Attenuation of ILK activity or expression was, however, associated with decreases in YB-1 (Y-box binding protein-1) protein and transcript levels. YB-1 is a known transcriptional regulator of Her2/neu expression, and in this study it is demonstrated that inhibition of ILK activity using QLT0267 decreased YB-1 promoter activity by 50.6%. ILK inhibition was associated with changes in YB-1 localization, as reflected by localization of cytoplasmic YB-1 into stress granules. ILK inhibition also suppressed TWIST (a regulator of YB-1 expression) protein expression. To confirm the role of ILK on YB-1 and TWIST, cells were engineered to overexpress ILK. This was associated with a fourfold increase in the level of YB-1 in the nucleus, and a 2- and 1.5-fold increase in TWIST and Her2/neu protein levels, respectively. Taken together, these data indicate that ILK regulates the expression of Her2/neu through TWIST and YB-1, lending support to the use of ILK inhibitors in the treatment of aggressive Her2/neu-positive tumors.

Thrombin regulates the metastatic potential of human rhabdomyosarcoma cells: distinct role of PAR1 and PAR3 signaling

We observed that human rhabdomyosarcoma (RMS) cells highly express a tissue factor that promotes thrombin formation, which indirectly and directly affects RMS progression. First, we found that thrombin activates platelets to generate microvesicles (PMV), which transfer to RMS cells' alpha2beta3 integrin and increase their adhesiveness to endothelial cells. Accordingly, RMS cells covered with PMVs showed higher metastatic potential after i.v. injection into immunodeficient mice. Furthermore, PMVs activate mitogen-activated protein kinase (MAPK)p42/44 and AKT to chemoattract RMS cells. We also found that RMS cells express functional protease-activated receptor-1 (PAR1) and PAR3 and respond to thrombin stimulation by MAPKp42/44 and MAPKp38 phosphorylation. To our surprise, thrombin did not affect RMS proliferation or survival; it inhibited the chemotactic and adhesive properties of RMS cells. However, when PAR1-specific agonist thrombin receptor-activating peptide 6 was used, which does not activate PAR3, selective PAR1 stimulation enhanced RMS proliferation. To learn more on the role of PAR1 and PAR3 antagonism in RMS proliferation and metastasis, we knocked down both receptors by using a short hairpin RNA strategy. We found that although thrombin does not affect growth of PAR1(-/-) cells, it stimulated the proliferation of PAR3(-/-) cells. More importantly, PAR3(-/-) cells, in contrast to PAR1(-/-) ones, formed larger tumors in immunodeficient mice. We conclude that thrombin is a novel underappreciated modulator of RMS metastasis and that we have identified a novel role for PAR3 in thrombin signaling.

TWISTing an embryonic transcription factor into an oncoprotein

Over the past decade, the reactivation of TWIST embryonic transcription factors has been described as a frequent event and a marker of poor prognosis in an impressive array of human cancers. Growing evidence now supports the premise that these cancers hijack TWIST's embryonic functions, granting oncogenic and metastatic properties. In this review, we report on the history and recent breakthroughs in understanding TWIST protein functions and the emerging role of the associated epithelial-mesenchymal transition (EMT) in tumorigenesis. We then broaden the discussion to address the general contribution of reactivating embryonic programs in cancerogenesis.

Enhanced adhesion of early endothelial progenitor cells to radiation-induced senescence-like vascular endothelial cells in vitro

The effects of ionizing radiation (IR) on tumor neovascularization are still unclear. We previously reported that vascular endothelial cells (ECs) expressing the IR-induced senescence-like (IRSL) phenotype exhibit a significant decrease in angiogenic activity in vitro. In this study, we examined the effects of the IRSL phenotype on adhesion to early endothelial progenitor cells (early EPCs). Adhesion of human peripheral blood-derived early EPCs to human umbilical vein endothelial cells (HUVECs) expressing the IRSL phenotype was evaluated by an adhesion assay under static conditions. It was revealed that the IRSL HUVECs supported significantly more adhesion of early EPCs than normal HUVECs. Expressions of ICAM-1, VCAM-1 and E-selectin were up-regulated in IRSL HUVECs. Pre-treatment of IRSL HUVECs with adhesion-blocking monoclonal antibodies against E-selectin and VCAM-1 significantly reduced early EPC adhesion to IRSL HUVECs, suggesting a potential role for the E-selectin and VCAM-1 in the adhesion between IRSL ECs and early EPCs. Therefore, the IRSL phenotype expressed in ECs may enhance neovascularization via increased homing of early EPCs. Our findings are first to implicate the complex effects of this phenotype on tumor neovascularization following irradiation.

Thrombin induces tumor cell cycle activation and spontaneous growth by down-regulation of p27Kip1, in association with the up-regulation of Skp2 and MiR-222

The effect of thrombin on tumor cell cycle activation and spontaneous growth was examined in synchronized serum-starved tumor cell lines and a model of spontaneous prostate cancer development in TRAMP mice. BrdUrd incorporation and propidium iodide staining of prostate LNCaP cells arrested in G(0) and treated with thrombin or serum revealed a 48- and 29-fold increase in S phase cells, respectively, at 8 hours. Similar results were obtained with TRAMP cells and a glioblastoma cell line, T98G. Cell cycle kinases and inhibitors in synchronized tumor cells revealed high levels of p27(Kip1) and low levels of Skp2 and cyclins D1 and A. Addition of thrombin, TFLLRN, or serum down-regulated p27(Kip1) with concomitant induction of Skp2, Cyclin D1, and Cyclin A with similar kinetics. LNCaP p27(Kip1)-transfected cells or Skp2 knockdown cells were refractory to thrombin-induced cell cycle activation. MicroRNA 222, an inhibitor of p27(Kip1), was robustly up-regulated by thrombin. The in vitro observations were tested in vivo with transgenic TRAMP mice. Repetitive thrombin injection enhanced prostate tumor volume 6- to 8-fold (P < 0.04). Repetitive hirudin, a specific potent antithrombin, decreased tumor volume 13- to 24-fold (P < 0.04). Thus, thrombin stimulates tumor cell growth in vivo by down-regulation of p27(Kip1).