Upregulation Of Thrombospondin-1 Research Articles

Investigation of a UPR-Related Gene Signature Identifies the Pro-Fibrotic Effects of Thrombospondin-1 by Activating CD47/ROS/Endoplasmic Reticulum Stress Pathway in Lung Fibroblasts.

Unfolded protein response (UPR) signaling and endoplasmic reticulum (ER) stress have been linked to pulmonary fibrosis. However, the relationship between UPR status and pulmonary function and prognosis in idiopathic pulmonary fibrosis (IPF) patients remains largely unknown. Through a series of bioinformatics analyses, we established a correlation between UPR status and pulmonary function in IPF patients. Furthermore, thrombospondin-1 (TSP-1) was identified as a potential biomarker for prognostic evaluation in IPF patients. By utilizing both bulk RNA profiling and single-cell RNA sequencing data, we demonstrated the upregulation of TSP-1 in lung fibroblasts during pulmonary fibrosis. Gene set enrichment analysis (GSEA) results indicated a positive association between TSP-1 expression and gene sets related to the reactive oxygen species (ROS) pathway in lung fibroblasts. TSP-1 overexpression alone induced mild ER stress and pulmonary fibrosis, and it even exacerbated bleomycin-induced ER stress and pulmonary fibrosis. Mechanistically, TSP-1 promoted ER stress and fibroblast activation through CD47-dependent ROS production. Treatment with either TSP-1 inhibitor or CD47 inhibitor significantly attenuated BLM-induced ER stress and pulmonary fibrosis. Collectively, these findings suggest that the elevation of TSP-1 during pulmonary fibrosis is not merely a biomarker but likely plays a pathogenic role in the fibrotic changes in the lung.

RNF7 Induces Skeletal Muscle Cell Apoptosis and Arrests Cell Autophagy via Upregulation of THBS1 and Inactivation of the PI3K/Akt Signaling Pathway in a Rat Sepsis Model.

Recently, long noncoding RNAs (lncRNAs) have been highlighted for extensive functionality in sepsis. In this study, we aimed to explore the role of RNF7 in the progression of sepsis. We initially established a rat model of sepsis through cecal ligation and puncture induction, whereupon RNF7 expression was determined by RT-qPCR. Following adenovirus infection, the role of RNF7 in muscle injury, skeletal muscle protein metabolism, oxidative stress, and inflammation in sepsis rats was analyzed. Then, downstream mechanisms of RNF7 were identified and validated. Further, lipopolysaccharide was applied to treat myoblast to further demonstrate the in vitro role of RNF7. Our results showed that RNF7 expression was upregulated during sepsis. Overexpression of RNF7 worsened the sepsis-induced skeletal muscle injury, induced skeletal muscle protein metabolism, oxidative stress, and inflammation in sepsis rats. Meanwhile, overexpression of RNF7 elevated thrombospondin-1 (THBS1) expression. Silencing of RNF7 inhibited THBS1 and activated the PI3K/Akt signaling pathway, arresting the release of inflammatory factors and oxidative stress levels in skeletal muscle cells. Altogether, RNF7 may promote skeletal muscle cell apoptosis while simultaneously inhibiting cell autophagy through the promotion of THBS1 and inactivation of the PI3K/Akt signaling pathway.

Cell surface GRP78 regulates TGFβ1-mediated profibrotic responses via TSP1 in diabetic kidney disease.

Introduction: Diabetic kidney disease (DKD) is the leading cause of kidney failure in North America, characterized by glomerular accumulation of extracellular matrix (ECM) proteins. High glucose (HG) induction of glomerular mesangial cell (MC) profibrotic responses plays a central role in its pathogenesis. We previously showed that the endoplasmic reticulum resident GRP78 translocates to the cell surface in response to HG, where it mediates Akt activation and downstream profibrotic responses in MC. Transforming growth factor β1 (TGFβ1) is recognized as a central mediator of HG-induced profibrotic responses, but whether its activation is regulated by cell surface GRP78 (csGRP78) is unknown. TGFβ1 is stored in the ECM in a latent form, requiring release for biological activity. The matrix glycoprotein thrombospondin 1 (TSP1), known to be increased in DKD and by HG in MC, is an important factor in TGFβ1 activation. Here we determined whether csGRP78 regulates TSP1 expression and thereby TGFβ1 activation by HG. Methods: Primary mouse MC were used. TSP1 and TGFβ1 were assessed using standard molecular biology techniques. Inhibitors of csGRP78 were: 1) vaspin, 2) the C-terminal targeting antibody C38, 3) siRNA downregulation of its transport co-chaperone MTJ-1 to prevent GRP78 translocation to the cell surface, and 4) prevention of csGRP78 activation by its ligand, active α2-macroglobulin (α2M*), with the neutralizing antibody Fα2M or an inhibitory peptide. Results: TSP1 transcript and promoter activity were increased by HG, as were cellular and ECM TSP1, and these required PI3K/Akt activity. Inhibition of csGRP78 prevented HG-induced TSP1 upregulation and deposition into the ECM. The HG-induced increase in active TGFβ1 in the medium was also inhibited, which was associated with reduced intracellular Smad3 activation and signaling. Overexpression of csGRP78 increased TSP-1, and this was further augmented in HG. Discussion: These data support an important role for csGRP78 in regulating HG-induced TSP1 transcriptional induction via PI3K/Akt signaling. Functionally, this enables TGFβ1 activation in response to HG, with consequent increase in ECM proteins. Means of inhibiting csGRP78 signaling represent a novel approach to preventing fibrosis in DKD.

Abstract P153: Upregulation Of Thrombospondin-1 Associates With Accelerated Atherosclerosis And Reduced Smooth Muscle Cell Differentiation In Metabolic Syndrome

Hyperglycemia and obesity, characteristic of metabolic syndrome (MetS), are important risk-factors for atherosclerosis. MetS patients manifest increased vascular smooth muscle cell (VSMC) migration and proliferation, hallmark of VSMC phenotypic transition, critical for evolution of atherosclerosis. We previously reported that high glucose and high leptin independently upregulate a potent proatherogenic matricellular protein, Thrombospondin-1 (TSP-1), expression in VSMC. The goal of the present study was to interrogate the role of TSP-1 in SMC de-differentiation and development of atherosclerosis in MetS. We utilized a mouse model of combined MetS and atherosclerosis (KKAy +/- /ApoE -/- ) generated by crossing obese hyperglycemic agouti KKAy +/- mice with atherosclerotic ApoE -/- . Upon weaning (4 wks age), male yellow KKAy +/- /ApoE -/- and age-matched black KKAy -/- /ApoE -/- littermates on standard lab diet were monitored monthly for body weight and blood glucose. At 24 wks age, mice were harvested after overnight fasting; plasma, aorta and heart were collected for biochemical, molecular and lesion studies. Prior to harvest, mice were subjected to treadmill exercise test at an incline with progressively increasing speed until exhaustion. At 16 wks age, yellow KKAy +/- /ApoE -/- mice showed significant increase in body weight and random blood glucose levels (<0.0001) vs. black KKAy -/- /ApoE -/- littermates, validating the MetS phenotype. Peak oxygen consumption (VO 2max ), maximum running speed and total run time until exhaustion were significantly reduced in MetS KKAy +/- /ApoE -/- mice (p<0.003 vs. non-MetS KKAy -/- /ApoE -/- ), suggesting impaired cardiovascular fitness. Aortic root morphometry revealed 4-fold increase in lesion lipid burden in MetS vs non-MetS mice. This was accompanied with reduced LMOD (SM contractile marker) and SRF (transcriptional activator of SM contractile genes) expression in aortic vessels of MetS mice (p<0.04 vs. non-MetS mice). Notably, lesion abundance and reduced SMC differentiation associated with increased TSP-1 expression in the aortic vasculature of MetS mice. Together, our data suggest a putative role of TSP-1 in SMC de-differentiation and atherosclerotic lesion formation in metabolic syndrome.

Upregulation of THBS1 is Related to Immunity and Chemotherapy Resistance in Gastric Cancer.

PurposeThrombospondin 1 (THBS1) is an endogenous inhibitor of angiogenesis, but it also promotes tumor invasion, metastasis, and immune response in the tumor environment. Previous research has found that THBS1 is highly expressed in many tumors and has a negative correlation with tumor prognosis. However, research on the relationship between THBS1 and immune infiltration in GC is less well documented, and the objective of our study was to investigate the role of THBS1 expression in GC.Patients and MethodsThe expression of THBS1 in GC was analyzed by Oncomine, TIMER, TGCA, GEO and IHC staining. Analysis of the signaling pathways associated with THBS1 expression in GC uses GSEA. The relationship between THBS1 expression and immune infiltration was analyzed by the ESTIMATE algorithm, single-cell transcriptome analysis, TIMER2 database and CIBERSORT algorithm. Finally, the relationship between THBS1 expression and drug sensitivity was analyzed by the CellMiner database.ResultsTHBS1 was overexpressed in GC and was associated with poor prognosis, and high THBS1 expression was an independent risk factor. GSEA results showed that high THBS1 expression in GC was associated with tumorigenesis, adhesion, and significant immune enrichment. THBS1 expression was most strongly correlated with tumor-associated macrophages (TAMs), M2 macrophages and cancer-associated fibroblast (CAFs) in GC. THBS1 expression positively correlates with most immune checkpoint members, suggesting that THBS1 may play an important role in the tumor microenvironment. THBS1 overexpression was negatively correlated with some drug sensitivities, such as Oxaliplatin.ConclusionUpregulation of THBS1 was positively correlated with poor prognosis and immunosuppression in GC and negatively correlated with anticancer drug sensitivity, suggesting that THBS1 may serve as a potential target for the treatment of GC.

Molecular factors related to skeletal muscle atrophy in a mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is progressive neurological disease that results in the death of motor neurons in the brain and spinal cord, leading to a decrease in skeletal muscle size and muscle weakness, wasting, or paralysis. Most research on ALS has focused on motor neuron death, and the underlying mechanisms are not well understood. This study examined the molecular mechanisms underlying muscle degeneration. We compared the protein and cytokine profiles of gastrocnemius muscle in ALS model hSOD1G93A mice at pre-symptomatic and symptomatic stages by western blotting. Pro-inflammatory factors including tumor necrosis factor-α, interleukin (IL)-1β and IL-6, and cluster of differentiation 11b were upregulated in the muscle of symptomatic as compared to pre-symptomatic mice. Additionally, the levels of oxidative stress-related proteins, heme oxygenase-1 and ferritin, were increased in muscle from symptomatic as compared to pre-symptomatic mice. We also observed increased autophagy dysfunction and metabolic dysregulation in the muscles of symptomatic hSOD1G93A as compared to non-Tg and pre-symptomatic hSOD1G93A mice, which was accompanied by upregulation of thrombospondin-1, Prospero-related homeobox 1, glial fibrillary acidic protein, and DNA-damage-inducible 45α. Increased inflammation, oxidative stress, and autophagy contribute to motor neuron death and muscle atrophy in ALS, and the factors involved in these processes are potential therapeutic targets for treatment of this disease.

MicroRNA-221 Inhibits Latent TGF-β1 Activation through Targeting Thrombospondin-1 to Attenuate Kidney Failure-Induced Cardiac Fibrosis

Kidney failure (KF) is associated with cardiac fibrosis and significantly increased mortality in heart failure. Thrombospondin-1 (TSP1), a key regulator of latent transforming growth factor-β1 (L-TGF-β1) activation, is a predicted target of miR-221. We hypothesized miR-221 attenuates severe KF-associated cardiac fibrosis via targeting of Thbs1 with subsequent inhibition of L-TGF-β1 activation. Rat cardiac fibroblasts (cFB) were isolated and transfected with microRNA-221 (miR-221) mimics or mimic control (miR-221 and MC) with or without exposure to L-TGF-β1. We demonstrate miR-221 downregulates Thbs1 via direct 3′ untranslated region (3′ UTR) targeting with consequent inhibition of L-TGF-β1 activation in cFB as proven by the significant reduction of myofibroblast activation, collagen secretion, TGF-β1 signaling, TSP1 secretion, and TGF-β1 bioactivity measured by Pai1 promoter reporter. The 5/6 nephrectomy (Nx) model of cardiac fibrosis was used to test the in vivo therapeutic efficacy of miR-221 (i.v. 1 mg/kg ×3). miR-221 significantly inhibited Nx-induced upregulation of TSP1 and p-SMAD3 in the heart at day-7 and reduced cardiac fibrosis (picro-sirius), improved cardiac function (±dP/dt), and improved 8-week survival rate (60% versus 36%; p = 0.038). miR-221 mimic treatment improved survival and reduced cardiac fibrosis in a model of severe KF. miR-221 is a therapeutic target to address cardiac fibrosis originating from renal disease and other causes.

Treatment with a Combination of Metformin and 2-Deoxyglucose Upregulates Thrombospondin-1 in Microvascular Endothelial Cells: Implications in Anti-Angiogenic Cancer Therapy.

Metformin, the most widely used anti-diabetic drug, also exhibits anti-cancer properties; however, the true potential of metformin as an anticancer drug remains largely unknown. In this study using mouse microvascular endothelial cells (MMECs), we investigated the effects of metformin alone or in combination with the glycolytic inhibitor, 2-deoxyglucose (2DG), on angiogenesis-a process known to be an integral part of tumor growth, cancer cell survival and metastasis. MMECs were exposed to 2DG (1–10 mM) for 48 h in the absence or presence of metformin (2 mM). The status of angiogenic and anti-angiogenic marker proteins, proteins of the mTOR pathway and cell-cycle-related proteins were quantified by Western blot analysis. Assays for cell proliferation, migration and tubulogenesis were also performed. We observed robust up-regulation of anti-angiogenic thrombospondin-1 (TSP1) and increased TSP1-CD36 co-localization with a marked decrease in the levels of phosphorylated vascular endothelial growth factor receptor-2 (pVEGFR2; Y1175) in 2DG (5 mM) exposed cells treated with metformin (2 mM). Additionally, treatment with metformin and 2DG (5 mM) inhibited the Akt/mTOR pathway and down-regulated the cell-cycle-related proteins such as p-cyclin B1 (S147) and cyclins D1 and D2 when compared to cells that were treated with either 2DG or metformin alone. Treatment with a combination of 2DG (5 mM) and metformin (2 mM) also significantly decreased cell proliferation, migration and tubulogenic capacity when compared to cells that were treated with either 2DG or metformin alone. The up-regulation of TSP1, inhibition of cell proliferation, migration and tubulogenesis provides support to the argument that the combination of metformin and 2DG may prove to be an appropriate anti-proliferative and anti-angiogenic therapeutic strategy for the treatment of some cancers.

Thrombospondin 1 Triggers Osteosarcoma Cell Metastasis and Tumor Angiogenesis.

Osteosarcomas, especially those with metastatic or unresectable disease, have limited treatment options. The antitumor effects of pharmacologic inhibitors of angiogenesis in osteosarcomas are hampered in patients by the rapid development of tumor resistance, notably through increased invasiveness and accelerated metastasis. Here we demonstrated that thrombospondin 1 (TSP-1) is a potent inhibitor of the growth and metastasis of the osteosarcoma cell line MG-63. Moreover, we demonstrate that upregulation of TSP-1 facilitated expression of vasculostatin in MG-63 cells. In angiogenesis assays, overexpression of TSP-1 inhibited MG-63 cells and induced tube formation of human umbilical vein endothelial cells (HUVECs) in a CD36-dependent fashion. Finally, in xenografted tumors, we observed that TSP-1 overexpression inhibited angiogenesis and tumor growth. These results provided strong evidence for an important role of the TSP-1/CD36/vasculostatin signaling axis in mediating the antiangiogenic activity of osteosarcoma.

FGF7/FGFR2 signal promotes invasion and migration in human gastric cancer through upregulation of thrombospondin-1.

Fibroblast growth factor 7 (FGF7) is a mesenchyme-specific heparin-binding growth factor that binds FGF receptor 2 (FGFR2) to regulate numerous cellular and physiological processes. FGF7/FGFR2 signal is associated with gastric cancer progression. In the present study, we investigated the molecular mechanism by which FGF7/FGFR2 promotes invasion and migration in human gastric cancer. We first demonstrated that increased FGFR2 expression in human gastric cancer tissues was significantly associated with tumor depth and clinical stage in human gastric cancer tissues. Thrombospondin 1 (THBS1) is an extracellular glycoprotein that plays multiple roles in cell-matrix and cell-cell interactions. Increased expression of THBS1 significantly correlated with tumor differentiation. FGFR2 and THBS1 expression were both increased in cancer tissues as compared with adjacent normal tissues and their expression was positively correlated. In vitro, FGF7 stimulation of cell invasion and migration was partially suppressed by the FGFR2 knockdown. In addition, FGF7/FGFR2 upregulated THBS1, and cell invasion and migration were decreased by knockdown of THBS1. Furthermore, the PI3K/Akt/mTOR signaling pathway was predominantly responsible for FGF7/FGFR2-induced THBS1 upregulation. Taken together, our data suggest that FGF7/FGFR2/THBS1 is associated with the regulation of invasion and migration in human gastric cancer.

TSP1-CD47 signaling is upregulated in clinical pulmonary hypertension and contributes to pulmonary arterial vasculopathy and dysfunction.

Thrombospondin-1 (TSP1) is a ligand for CD47 and TSP1-/- mice are protected from pulmonary hypertension (PH). We hypothesized the TSP1-CD47 axis is upregulated in human PH and promotes pulmonary arterial vasculopathy. We analyzed the molecular signature and functional response of lung tissue and distal pulmonary arteries (PAs) from individuals with (n = 23) and without (n = 16) PH. Compared with controls, lungs and distal PAs from PH patients showed induction of TSP1-CD47 and endothelin-1/endothelin A receptor (ET-1/ETA) protein and mRNA. In control PAs, treatment with exogenous TSP1 inhibited vasodilation and potentiated vasoconstriction to ET-1. Treatment of diseased PAs from PH patients with a CD47 blocking antibody improved sensitivity to vasodilators. Hypoxic wild type (WT) mice developed PH and displayed upregulation of pulmonary TSP1, CD47, and ET-1/ETA concurrent with down regulation of the transcription factor cell homolog of the v-myc oncogene (cMyc). In contrast, PH was attenuated in hypoxic CD47-/- mice while pulmonary TSP1 and ET-1/ETA were unchanged and cMyc was overexpressed. In CD47-/- pulmonary endothelial cells cMyc was increased and ET-1 decreased. In CD47+/+ cells, forced induction of cMyc suppressed ET-1 transcript, whereas suppression of cMyc increased ET-1 signaling. Furthermore, disrupting TSP1-CD47 signaling in pulmonary smooth muscle cells abrogated ET-1-stimulated hypertrophy. Finally, a CD47 antibody given 2weeks after monocrotaline challenge in rats upregulated pulmonary cMyc and improved aberrations in PH-associated cardiopulmonary parameters. In pre-clinical models of PH CD47 targets cMyc to increase ET-1 signaling. In clinical PH TSP1-CD47 is upregulated, and in both, contributes to pulmonary arterial vasculopathy and dysfunction.

Quercetin inhibits angiogenesis through thrombospondin-1 upregulation to antagonize human prostate cancer PC-3 cell growth in vitro and in vivo

The rapid growth, morbidity and mortality of prostate cancer, and the lack of effective treatment have attracted great interests of researchers to find novel cancer therapies aiming to inhibit angiogenesis and tumor growth. Quercetin is a flavonoid compound that widely exists in the nature. Our previous study preliminarily demonstrated that quercetin effectively inhibited human prostate cancer cell xenograft tumor growth by inhibiting angiogenesis. Thrombospondin-1 (TSP-1) is the first reported endogenous anti-angiogenic factor that can inhibit angiogenesis and tumorigenesis. However, the relationship between quercetin inhibiting angiogenesis and TSP-1 upregulation in prostate cancer has not been determined. Thus, we explored the important role of TSP-1 upregulation in reducing angiogenesis and anti-prostate cancer effect of quercetin both in vitro and in vivo for the first time. After the selected doses were used for a certain time, quercetin i) significantly inhibited PC-3 and human umbilical vein endothelial cells (HUVECs) proliferation, migration and invasion in a dose-dependent manner; ⅱ) effectively inhibited prostate cancer PC-3 cell xenograft tumor growth by 37.5% with 75 mg/kg as compared to vehicle control group, more effective than 25 (22.85%) and 50 mg/kg (29.6%); ⅲ) was well tolerated by BALB/c mice and no obvious toxic reactions were observed; ⅳ) greatly reduced angiogenesis and led to higher TSP-1 protein and mRNA expression both in vitro and in vivo in a dose-dependent manner. Therefore, quercetin could increase TSP-1 expression to inhibit angiogenesis resulting in antagonizing prostate cancer PC-3 cell and xenograft tumor growth. The present study can lay a good basis for the subsequent concrete mechanism study and raise the possibility of applying quercetin to clinical for human prostate cancer in the near future.

Decrease of let-7f in low-dose metronomic Paclitaxel chemotherapy contributed to upregulation of thrombospondin-1 in breast cancer.

Low-dose metronomic (LDM) paclitaxel therapy displayed a stronger anti-angiogenic activity on breast tumors with fewer side effects. Upregulation of anti-angiogenic factor Thrombospondin-1 (TSP-1) accords for therapeutic potency of LDM paclitaxel, but its molecular mechanism has not been elucidated yet. microRNAs (miRNAs) have emerged as new important regulators of tumor growth and metastasis. Here, we hypothesize that miRNAs are involved in TSP-1 overexpression in paclitaxel LDM therapy of breast tumors. The miRNA profile of tumor tissues from control, LDM and MTD groups in 4T1 mouse breast cancer model was detected by microarray, and then verified by quantitative real-time PCR (qRT-PCR). Luciferase assay and western blot were employed to explore the mechanisms of miRNAs involved in this process. We found that let-7f, let-7a, miR-19b and miR-340-5p were reduced by >2 fold, and miR-543* and miR-684 were upregulated by at least 50% in paclitaxel LDM therapy. qRT-PCR verification revealed that let-7f level was reduced most significantly in LDM therapy. Computational prediction using TargetScan and miRanda suggested THBS1 which encodes TSP-1 as a potential target for let-7f. Luciferase activity assay further confirmed that let-7f may bind to 3'UTR of THBS1 gene and inhibit its activity. Moreover, forced expression of let-7f led to a decrease of TSP-1 at both mRNA and protein levels in MCF-7 cells. Contrastly, let-7f inhibition induced an increased expression of THBS1 mRNA and TSP-1 protein, but did not affect the proliferation and apoptosis of MCF-7 cells. Paclitaxel LDM therapy led to a decrease of let-7f and the elevation of TSP-1 protein expression in MCF-7 cells, while overexpression of let-7f may abolish LDM-induced the upregulation of TSP-1 in MCF-7 cells. In summary, let-7f inhibition contributed to the upregulation of TSP-1 in paclitaxel LDM therapy, independently of proliferation, cell cycle arrest and apoptosis of breast cancer. This study indicates let-7f as a potential therapeutic target for breast tumor.

Immunosurveillance by Antiangiogenesis: Tumor Growth Arrest by T Cell–Derived Thrombospondin-1

Recent advances in cancer immunotherapy suggest that manipulation of the immune system to enhance the antitumor response may be a highly effective treatment modality. One understudied aspect of immunosurveillance is antiangiogenic surveillance, the regulation of tumor angiogenesis by the immune system, independent of tumor cell lysis. CD4(+) T cells can negatively regulate angiogenesis by secreting antiangiogenic factors such as thrombospondin-1 (TSP-1). In tumor-bearing mice, we show that a Th1-directed viral infection that triggers upregulation of TSP-1 in CD4(+) and CD8(+) T cells can inhibit tumor angiogenesis and suppress tumor growth. Using bone marrow chimeras and adoptive T-cell transfers, we demonstrated that TSP-1 expression in the T-cell compartment was necessary and sufficient to inhibit tumor growth by suppressing tumor angiogenesis after the viral infection. Our results establish that tumorigenesis can be stanched by antiangiogenic surveillance triggered by an acute viral infection, suggesting novel immunologic approaches to achieve antiangiogenic therapy.

2013 Late-Breaking Basic Science Abstracts

### 21998 #### Enhanced Myocardial Repair with CardioChimeras Pearl J Quijada, Jonathan D Cubillo, Claudio Staub, Mark A Sussman; San Diego State Univ, San Diego, CA Dual stem cell transplantation of c-kit positive cardiac progenitor cells (CPCs) and mesenchymal stem cells (MSCs) after infarction support modest improvements in cardiac function, however there are currently no reports substantiating a single stem cell type supporting both direct and indirect mechanisms of myocardial repair. Therefore we created a CardioChimera, a stem/progenitor cell formed by fusion between CPCs and MSCs, resulting in a unique progeny superior to either individual precursor. CardioChimeras were purified after cell fusion with Hemagglutinating virus of Japan and expanded clonally based on dual expression of fluorescent proteins mCherry and eGFP from CPCs and MSCs respectively. CardioChimeras are mono-nucleated, have comparable growth kinetics to parental CPCs and MSCs and display increased cellular size unrelated to cell cycle arrest and/or senescence. CardioChimeras have increased expression of cardiomyogenic lineage markers cardiac troponin T (2.5-fold), smooth muscle 22 (9.3-fold), and CD31 (10.7-fold) concomitantly associated with decreased c-kit protein expression (50%) relative to parent CPCs. Lineage commitment of CardioChimeras is bolstered by dexamethasone treatment measured by mRNA levels of cardiogenic genes and increases in active mitochondria (2.2-fold) after labeling with MitoTracker. Induction of apoptosis is blunted in cardiomyocytes co-cultured with CardioChimeras compared to co-culturing with CPCs and MSCs alone, or combination of non-fused parent cells. CardioChimeras enhance cardiomyocyte growth similar to parent MSCs owing to an increased propensity to secrete pro-growth factors. Collectively, CardioChimeras represent an adaptable cell therapy combining the beneficial properties of CPCs to undergo cardiac specific commitment as well as MSCs that foster an improved microenvironment with protective paracrine secretion. Clinically, CardioChimeras merge the application of distinct cell types into a single entity for increased engraftment, mitigation of inflammation and blunting the progression of heart failure by promoting myocardial regeneration. …

Thrombospondin-1 mediates oncogenic Ras–induced senescence in premalignant lung tumors

Progression of premalignant lesions is restrained by oncogene-induced senescence. Oncogenic Ras triggers senescence in many organs, including the lung, which exhibits high levels of the angiogenesis inhibitor thrombospondin-1 (TSP-1). The contribution of TSP-1 upregulation to the modulation of tumorigenesis in the lung is unclear. Using a mouse model of lung cancer, we have shown that TSP-1 plays a critical and cell-autonomous role in suppressing Kras-induced lung tumorigenesis independent of its antiangiogenic function. Overall survival was decreased in a Kras-driven mouse model of lung cancer on a Tsp-1-/- background. We found that oncogenic Kras-induced TSP-1 upregulation in a p53-dependent manner. TSP-1 functioned in a positive feedback loop to stabilize p53 by interacting directly with activated ERK. TSP-1 tethering of ERK in the cytoplasm promoted a level of MAPK signaling that was sufficient to sustain p53 expression and a senescence response. Our data identify TSP-1 as a p53 target that contributes to maintaining Ras-induced senescence in the lung.

Adenosine promotes angiogenesis through up-regulation of thrombospondin-1

Adenosine promotes angiogenesis through up-regulation of thrombospondin-1

PRMT6 overexpression upregulates TSP-1 and downregulates MMPs: Its implication in motility and invasion

In this study, we investigate the molecular mechanism by which protein arginine methyltransferase 6 (PRMT6) exerts anti-invasiveness effect against breast cancer cells and prostate cancer cells. PRMT6 has been known to be responsible for asymmetric dimethylation of histone H3 at R2 (H3R2me2a). To investigate the biological role of PRMT6, we first established stable cell lines expressing GFP-PRMT6 with MCF7 and PC3 cells. Growth rates and colony forming abilities of PRMT6-overexpressing cells were significantly retarded compared to control GFP expressing cells. This growth retardation seems to be associated with p21WAF1 induction. In addition, our data show that migration and invasion of prostate cancer cells was strongly suppressed by PRMT6 overexpression. In parallel, the levels of thrombospondin-1 (TSP-1), a potent natural inhibitor of angiogenesis, were highly up-regulated in both PRMT6-overexpressing cells. Furthermore, this suppression of migration and invasion by PRMT6 overexpression was significantly rescued by specific knock-down of TSP-1. Concomitantly, down-regulations of MMP-2 and -9 were observed in PRMT6-overexpressing cells. Taken together, our data demonstrate that PRMT6 overexpression is associated with regulation of motility and invasion through up-regulation of TSP-1 and down-regulation of MMPs in human cancer cells.

Caffeine-induced endothelial cell death and the inhibition of angiogenesis

Numerous studies have shown that adenosine or adenosine agonists can stimulate angiogenesis. However, the effect of caffeine (a known adenosine receptor antagonist) on angiogenesis has not been previously studied. Accordingly, this study was undertaken to examine the effect of caffeine on angiogenesis and to clarify the mechanism involved. Chick chorioallantoic membrane assays were used to investigate the effect of caffeine on angiogenesis and proliferation assays using human umbilical vein endothelial cells (HUVECs), were used to study its effects on specific aspects of angiogenesis. The expressions of caspase-3 and Bcl-2 were examined by western blotting, immunofluorescence staining was used to identify HUVEC morphological changes, and fluorescence activated cell sorting (FACS) and DAPI staining were used to detect HUVEC apoptosis. Caffeine was found to inhibit blood vessel formation dose-dependently and to inhibit the proliferation of HUVECs time- and dose-dependently. FACS analysis and DAPI staining showed that inhibitory effect of caffeine on HUVEC proliferation was the result of apoptosis and the up-regulation of thrombospondin-1 (TSP-1). Furthermore, TSP-1 levels were down-regulated by NECA but were unaffected by CGS21680, indicating that caffeine regulated TSP-1 expression via adenosine A2B receptor. In addition, caffeine up-regulated caspase-3 and down-regulated Bcl-2 at the protein level. These results suggest that the inhibitory effect of caffeine on angiogenesis is associated, at least in part, with its induction of endothelial cell apoptosis, probably mediated by a caspase-3 dependent mechanism.

The novel tumor suppressor NOL7 post-transcriptionally regulates thrombospondin-1 expression

Thrombospondin-1 (TSP-1) is an endogenous inhibitor of angiogenesis whose expression suppresses tumor growth in vivo. Like many angiogenesis-related genes, TSP-1 expression is tightly controlled by various mechanisms, but there is little data regarding the contribution of post-transcriptional processing to this regulation. NOL7 is a novel tumor suppressor that induces an antiangiogenic phenotype and suppresses tumor growth, in part through upregulation of TSP-1. Here we demonstrate that NOL7 is an mRNA-binding protein that must localize to the nucleoplasm to exert its antiangiogenic and tumor suppressive effects. There, it associates with the RNA-processing machinery and specifically interacts with TSP-1 mRNA through its 3'UTR. Reintroduction of NOL7 into SiHa cells increases luciferase expression through interaction with the TSP-1 3'UTR at both the mRNA and protein levels. NOL7 also increases endogenous TSP-1 mRNA half-life. Further, NOL7 post-transcriptional stabilization is observed in a subset of angiogenesis-related mRNAs, suggesting that the stabilization of TSP-1 may be part of a larger novel mechanism. These data demonstrate that NOL7 significantly alters TSP-1 expression and may be a master regulator that coordinates the post-transcriptional expression of key signaling factors critical for the regulation of the angiogenic phenotype.