Fibulin-5 Regulates Angiopoietin-1/Tie-2 Receptor Signaling in Endothelial Cells

Multiomics Analysis Unravels Alteration in Molecule and Pathways Involved in Nondiabetic Chronic Wounds

The prevalence of chronic wounds (CW) continues to grow. A thorough knowledge of the mechanism of CW formation remains elusive due to a lack of relevant studies. Furthermore, most previous studies concentrated on diabetic ulcers with relatively few investigations on other types. We performed this multiomics study to investigate the proteomic and metabolomic changes in wound and surrounding tissue from a cohort containing 13 patients with nondiabetic CW. Differentially expressed proteins (DEPs) and metabolites (DEMs) were filtered out and analyzed through multiomic profiling. The DEPs were further confirmed with the use of parallel reaction monitoring. Compared with the surrounding tissue, there were 82 proteins and 214 metabolites altered significantly in wound tissue. The DEPs were mainly enriched in focal adhesion (FA), extracellular matrix-receptor interaction (ERI), and the PI3K-Akt (PA) signaling pathway. Moreover, the DEMs were significantly enriched in amino sugar and nucleotide sugar metabolism and biosynthesis of nucleotide sugar pathways. In correlation analysis, we discovered that the PA signaling pathway, as well as its upstream and downstream pathways, coenriched some DEPs and DEMs. Additionally, we found that FBLN1, FBLN5, and EFEMP1 (FBLN3) proteins dramatically elevated in wound tissue and connected with the above signaling pathways. This multiomics study found that changes in FA, ERI, and PA signaling pathways had an impact on the cellular activities and functions of wound tissue cells. Additionally, increased expression of those proteins in wound tissue may inhibit vascular and skin cell proliferation and degrade the extracellular matrix, which may be one of the causes of CW formation.

Maternal n-3 enriched diet reprograms neurovascular transcriptome and blunts inflammation in neonate

Infection during perinatal period can adversely affect brain development, predispose infants to ischemic stroke and have lifelong consequences. We previously demonstrated that diet enriched in n-3 polyunsaturated fatty acids (PUFA) transforms brain lipid composition and protects from neonatal stroke. Vasculature is a critical interface between blood and brain providing a barrier to systemic infection. Here we examined whether maternal PUFA-enriched diets exert reprograming of endothelial cell signalling in 9-day old mice after endotoxin (LPS)-induced infection. Transcriptome analysis was performed on brain microvessels from pups born to dams maintained on 3 diets: standard, n-3 or n-6 enriched. N-3 diet enabled higher immune reactivity in brain vasculature, while preventing imbalance of cell cycle regulation and extracellular matrix cascades that accompanied inflammatory response in standard diet. LPS response in blood and brain was blunted in n-3 offspring. Cerebral angioarchitecture analysis revealed modified vessel complexity after LPS. Thus, n-3-enriched maternal diet partially prevents imbalance in homeostatic processes and alters inflammation rather than affects brain vascularization during early life. Importantly, maternal diet may presage offspring neurovascular outcomes later in life.

The Effects of Preeclamptic Milieu on Cord Blood Derived Endothelial Colony-Forming Cells

Preeclampsia is one of the leading causes of infant and maternal mortality worldwide. Many infants born from preeclamptic pregnancies are born prematurely with higher risk of developing cardiovascular later in their life. A key mechanism by which these complications occur is through stress-induced dysfunction of endothelial progenitor cells (EPCs), including endothelial colony-forming cells (ECFCs). To gain insight into this, cord blood derived ECFCs isolated from preeclamptic pregnancies (PRECs) were analyzed and compared to their healthy counterparts. While PRECs preserve key endothelial markers, they upregulate several markers associated with oxidative stress and inflammatory response. Compared to ECFCs, PRECs also exhibit lower migratory behaviors and impaired angiogenic potential. Interestingly, treatment of neuropilin-1 can improve tube formation in vitro. Collectively, this study reports that preeclamptic milieu influence phenotypes and functionality of PRECs, which can be rejuvenated using exogenous molecules. Promising results from this study warrant future investigations on the prospect of the rejuvenated PRECs to improve lung function of infants born from preeclamptic pregnancies.

MASP2 inhibition by narsoplimab suppresses endotheliopathies characteristic of transplant-associated thrombotic microangiopathy: in vitro and ex vivo evidence

Transplant-associated thrombotic microangiopathy (TA-TMA) is an endotheliopathy complicating up to 30% of allogeneic hematopoietic stem cell transplants (alloHSCT). Positive feedback loops among complement, pro-inflammatory, pro-apoptotic, and coagulation cascade likely assume dominant roles at different disease stages. We hypothesized that mannose-binding lectin-associated serine protease 2 (MASP2), principal activator of the lectin complement system, is involved in the microvascular endothelial cell (MVEC) injury characteristic of TA-TMA through pathways that are susceptible to suppression by anti-MASP2 monoclonal antibody narsoplimab. Pre-treatment plasmas from 8 of 9 TA-TMA patients achieving a complete TMA response in a narsoplimab clinical trial activated caspase 8, the initial step in apoptotic injury, in human MVEC. This was reduced to control levels following narsoplimab treatment in 7 of the 8 subjects. Plasmas from 8 individuals in an observational TA-TMA study, but not 8 alloHSCT subjects without TMA, similarly activated caspase 8, which was blocked in vitro by narsoplimab. mRNA sequencing of MVEC exposed to TA-TMA or control plasmas with and without narsoplimab suggested potential mechanisms of action. The top 40 narsoplimab-affected transcripts included upregulation of SerpinB2, which blocks apoptosis by inactivating procaspase 3; CHAC1, which inhibits apoptosis in association with mitigation of oxidative stress responses; and pro-angiogenesis proteins TM4SF18, ASPM, and ESM1. Narsoplimab also suppressed transcripts encoding pro-apoptotic and pro-inflammatory proteins ZNF521, IL1R1, Fibulin-5, aggrecan, SLC14A1, and LOX1, and TMEM204, which disrupts vascular integrity. Our data suggest benefits to narsoplimab use in high-risk TA-TMA and provide a potential mechanistic basis for the clinical efficacy of narsoplimab in this disorder.

Comprehensive characterization of the prostate tumor microenvironment identifies CXCR4/CXCL12 crosstalk as a novel antiangiogenic therapeutic target in prostate cancer

Background

Crosstalk between neoplastic and stromal cells fosters prostate cancer (PCa) progression and dissemination. Insight in cell-to-cell communication networks provides new therapeutic avenues to mold processes that contribute to PCa tumor microenvironment (TME) alterations. Here we performed a detailed characterization of PCa tumor endothelial cells (TEC) to delineate intercellular crosstalk between TEC and the PCa TME.

Methods

TEC isolated from 67 fresh radical prostatectomy (RP) specimens underwent multi-omic ex vivo characterization as well as orthogonal validation of both TEC functions and key markers by immunohistochemistry (IHC) and immunofluorescence (IF). To identify cell–cell interaction targets in TEC, we performed single-cell RNA sequencing (scRNA-seq) in four PCa patients who underwent a RP to catalogue cellular TME composition. Targets were cross-validated using IHC, publicly available datasets, cell culture expriments as well as a PCa xenograft mouse model.

Results

Compared to adjacent normal endothelial cells (NEC) bulk RNA-seq analysis revealed upregulation of genes associated with tumor vasculature, collagen modification and extracellular matrix remodeling in TEC. PTGIR, PLAC9, CXCL12 and VDR were identified as TEC markers and confirmed by IF and IHC in an independent patient cohort. By scRNA-seq we identified 27 cell (sub)types, including endothelial cells (EC) with arterial, venous and immature signatures, as well as angiogenic tip EC. A focused molecular analysis revealed that arterial TEC displayed highest CXCL12 mRNA expression levels when compared to all other TME cell (sub)populations and showed a negative prognostic role. Receptor-ligand interaction analysis predicted interactions between arterial TEC derived CXCL12 and its cognate receptor CXCR4 on angiogenic tip EC. CXCL12 was in vitro and in vivo validated as actionable TEC target by highlighting the vessel number- and density- reducing activity of the CXCR4-inhibitor AMD3100 in murine PCa as well as by inhibition of TEC proliferation and migration in vitro.

Conclusions

Overall, our comprehensive analysis identified novel PCa TEC targets and highlights CXCR4/CXCL12 interaction as a potential novel target to interfere with tumor angiogenesis in PCa.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01597-7.

The Lineage Differentiation and Dynamic Heterogeneity of Thymic Epithelial Cells During Thymus Organogenesis

Although much progress has been made recently in revealing the heterogeneity of the thymic stromal components, the molecular programs of cell lineage divergency and temporal dynamics of thymic epithelial cell (TEC) development are largely elusive. Here, we constructed a single-cell transcriptional landscape of non-hematopoietic cells from mouse thymus spanning embryonic to adult stages, producing transcriptomes of 30,959 TECs. We resolved the transcriptional heterogeneity of developing TECs and highlighted the molecular nature of early TEC lineage determination and cortico-medullary thymic epithelial cell lineage divergency. We further characterized the differentiation dynamics of TECs by clarification of molecularly distinct cell states in the thymus developing trajectory. We also identified a population of Bpifa1⁺ Plet1⁺ mTECs that was preserved during thymus organogenesis and highly expressed tissue-resident adult stem cell markers. Finally, we highlighted the expression of Aire-dependent tissue-restricted antigens mainly in Aire⁺ Csn2⁺ mTECs and Spink5⁺ Dmkn⁺ mTECs in postnatal thymus. Overall, our data provided a comprehensive characterization of cell lineage differentiation, maturation, and temporal dynamics of thymic epithelial cells during thymus organogenesis.

The Effect of Qingre Huayu Recipe on Wound Healing after Anal Fistulotomy in Sprague-Dawley Rats

Anal fistula is a common anorectal disease. At present, most scholars believe that its pathogenesis is related to anal gland infection. Anal fistula cannot heal on its own after the onset and must be treated surgically. The wound of anal fistula surgery is open and polluted, and it belongs to three types of three-stage healing; it is the most difficult to heal among all surgical incisions, with a long course of disease, a lot of exudation, and pain for the patient; traditional Chinese medicine has rich experience in the treatment of postoperative wound healing of anal fistula. The study aimed to evaluate the mechanism of Qingre Huayu (QRHY) Recipe on wound healing after fistulotomy on SD rats. SD rats (n = 72) were randomized into three groups post-anorectal surgery. The rats in the positive control group were given potassium permanganate (PP), treatment group were given QRHY, and trauma model group were given 0.9% normal salinity. The changes in wound secretion, granulated tissue, and epithelium tissue were observed, and wound healing rates were evaluated by the discrepancies in wound area. HE and Masson's staining as well as transmission electron microscopy were also performed. The localization as well as the measurement of Ang1, Src, and VE cadherin expression in each group adopted real-time PCR, western blot, and immunohistochemistry (IHC) assays. Statistically higher wound healing rates were observed in QRHY group on days 3, 7, and 14 compared with other groups. Histological analyses showed highly significant increase in collagen and fibroblasts, less inflammatory cells, and vascular endothelial permeability in QRHY rats. The transmission electron microscopy revealed that the intact structure of tight junctions in endothelial cells and well-organized collagen and VE-cadherin, Ang1, and Tie-2 were upregulated by QRHY, while Src was inhibited. This study showed that QRHY can promote wound healing after anal fistulas.

Engeletin protects against cerebral ischemia/reperfusion injury by modulating the VEGF/vasohibin and Ang-1/Tie-2 pathways

Engeletin is a natural derivative of Smilax glabra rhizomilax that exhibits anti-inflammatory activity and suppresses lipid peroxidation. In the present study, we sought to elucidate the mechanistic basis for the neuroprotective and pro-angiogenic activity of engeltin in a human umbilical vein endothelial cells (HUVECs) oxygen-glucose deprivation and reoxygenation (OGD/R) model system and a middle cerebral artery occlusion (MCAO) rat model of cerebral ischemia and reperfusion injury. These analyses revealed that engeletin (10, 20, or 40 mg/kg) was able to reduce the infarct volume, increase cerebral blood flow, improve neurological function, and bolster the expression of vascular endothelial growth factor (VEGF), vasohibin-2 (Vash-2), angiopoietin-1 (Ang-1), phosphorylated human angiopoietin receptor tyrosine kinase 2 (p-Tie2), and platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) in MCAO rats. Similarly, engeletin (100, 200, or 400 nM) markedly enhanced the migration, tube formation, and VEGF expression of HUVECs in an OGD/R model system, while the VEGF receptor (R) inhibitor axitinib reversed the observed changes in HUVEC tube formation activity and Vash-2, VEGF, and CD31 expression. These data suggested that engeletin exhibited significant neuroprotective effects against cerebral ischemia and reperfusion injury in rats, and improved cerebrovascular angiogenesis by modulating the VEGF/vasohibin and Ang-1/Tie-2 pathways.

Regulation of endothelial cell differentiation in embryonic vascular development and its therapeutic potential in cardiovascular diseases

During vertebrate development, the cardiovascular system begins operating earlier than any other organ in the embryo. Endothelial cell (EC) forms the inner lining of blood vessels, and its extensive proliferation and migration are requisite for vasculogenesis and angiogenesis. Many aspects of cellular biology are involved in vasculogenesis and angiogenesis, including the tip versus stalk cell specification. Recently, epigenetics has attracted growing attention in regulating embryonic vascular development and controlling EC differentiation. Some proteins that regulate chromatin structure have been shown to be directly implicated in human cardiovascular diseases. Additionally, the roles of important EC signaling such as vascular endothelial growth factor and its receptors, angiopoietin-1 and tyrosine kinase containing immunoglobulin and epidermal growth factor homology domain-2, and transforming growth factor-β in EC differentiation during embryonic vasculature development are briefly discussed in this review. Recently, the transplantation of human induced pluripotent stem cell (iPSC)-ECs are promising approaches for the treatment of ischemic cardiovascular disease including myocardial infarction. Patient-specific iPSC-derived EC is a potential new target to study differences in gene expression or response to drugs. However, clinical application of the iPSC-ECs in regenerative medicine is often limited by the challenges of maintaining cell viability and function. Therefore, novel insights into the molecular mechanisms underlying EC differentiation might provide a better understanding of embryonic vascular development and bring out more effective EC-based therapeutic strategies for cardiovascular diseases.

SIX1 and SIX4 homeoproteins regulate PAX7+ progenitor cell properties during fetal epaxial myogenesis

Pax7 expression marks stem cells in developing skeletal muscles and adult satellite cells during homeostasis and muscle regeneration. The genetic determinants that control the entrance into the myogenic program and the appearance of PAX7+ cells during embryogenesis are poorly understood. SIX homeoproteins are encoded by the sine oculis-related homeobox Six1-Six6 genes in vertebrates. Six1, Six2, Six4 and Six5 are expressed in the muscle lineage. Here, we tested the hypothesis that Six1 and Six4 could participate in the genesis of myogenic stem cells. We show that fewer PAX7+ cells occupy a satellite cell position between the myofiber and its associated basal lamina in Six1 and Six4 knockout mice (s1s4KO) at E18. However, PAX7+ cells are detected in remaining muscle masses present in the epaxial region of the double mutant embryos and are able to divide and contribute to muscle growth. To further characterize the properties of s1s4KO PAX7+ cells, we analyzed their transcriptome and tested their properties after transplantation in adult regenerating tibialis anterior muscle. Mutant stem cells contribute to hypotrophic myofibers that are not innervated but retain the ability to self-renew.

Correlation between the Serum Platelet-Derived Growth Factor, Angiopoietin-1, and Severity of Coronary Heart Disease

Background

The expression of the platelet-derived growth factor (PDGF), angiopoietin-1 (Ang-1) in patients with coronary artery disease of different studies was inconsistent. This study was to investigate the expression of the PDGF and Ang-1 in peripheral blood and coronary artery in patients with acute coronary syndrome (ACS) and the relationship between the expression of the PDGF and Ang-1 and the severity of coronary artery disease.

Methods

A total of 81 patients with acute coronary syndrome undergoing coronary angiography were enrolled from September 2012 to December 2013. Patients with ACS included 61 patients with acute myocardial infarction (AMI group) and 20 patients with unstable angina pectoris (UAP group). The 29 patients who were hospitalized for chest pain undergoing coronary angiography without stenosis and with TIMI level 3 blood flow were selected as the control group. During coronary arteriography (CAG) or percutaneous coronary intervention (PCI), blood in the peripheral artery and in the local coronary artery was collected from all the patients. Serum PDGF and Ang-1 levels were measured by ELISA. We calculated the Gensini score of each patient with CHD according to the result of CAG. Patients with ACS were followed up, and the major adverse cardiovascular and cerebrovascular adverse events were recorded.

Results

In peripheral blood, the concentration of the PDGF was significantly elevated in the ACS group than that of the control group. The level of the PDGF in the AMI group was significantly higher than that in the UAP group. In coronary artery blood, the level of the PDGF in the ACS group was significantly higher than that of the UAP group. There was no significant difference in the concentration of Ang-1 in peripheral blood between patients with coronary heart disease and the control group. The concentration of Ang-1 in the coronary artery was significantly lower than that in peripheral blood. The coronary Ang-1 concentrations in the ACS group were significantly higher than those in the UAP group. The concentrations of the PDGF and Ang-1 in peripheral and coronary artery blood were positively correlated with the severity of coronary lesions. Patients with MACCE had higher PDGF and Ang-1 levels in the coronary sinus.

Conclusion

The serum PDGF concentration in patients with acute coronary syndrome was significantly increased, especially in the local coronary artery. The serum Ang-1 in the coronary artery was significantly increased in patients with acute myocardial infarction and was related to the degree of coronary artery stenosis. Coronary sinus PDGF and Ang-1 levels can reflect the severity of lesions in patients with acute coronary syndrome.

DHA Attenuates Hypoxia/Reoxygenation Injury by Activating SSeCKS in Human Cerebrovascular Pericytes

Docosahexaenoic acid (DHA) can alleviate cerebral ischemia/reperfusion injury by reducing blood–brain barrier permeability and maintaining its integrity, accompanied by an increased Ang-1/Ang-2 ratio; however, the underlying mechanisms of these effects remain unclear. Src-suppressed C kinase substrates (SSeCKS), a substrate of protein kinase C, plays an important role in maintaining cell junctions and cell morphology and regulating cell permeability. However, whether DHA can increase SSeCKS expression and then mediate the Ang-1/Ang-2 ratio still needs to be studied. Human cerebrovascular pericytes (HBVPs) cultured in vitro were divided into groups, treated with or without DHA along with SSeCKS siRNA to knockdown SSeCKS expression, and then subjected to 24 h of hypoxia followed by 6 h of reoxygenation. Cell viability; lactate dehydrogenase (LDH) release; and Ang-1, Ang-2 and VEGF activity were detected by using ELISA kits. The apoptosis rate was assessed by TUNEL flow cytometry. Expression of the SSeCKS, Ang-1, Ang-2 and VEGF proteins was evaluated by western blotting. Pretreatment with 10 μM or 40 μM DHA efficiently attenuated hypoxia/reoxygenation (H/R) injury by activating SSeCKS to increase the Ang-1/Ang-2 ratio and downregulate VEGF expression in HBVPs, as evidenced by decreased LDH release and apoptotic rates and increased HBVPs viability. Meanwhile, after we used SSeCKS siRNA to knock down SSeCKS protein expression, the protective effect of DHA on HBVPs following H/R injury was reversed. In conclusion, DHA can activate SSeCKS to increase the Ang-1/Ang-2 ratio and downregulate VEGF expression in HBVPs, thus reducing H/R injury.

Fibulin-7 is overexpressed in glioblastomas and modulates glioblastoma neovascularization through interaction with angiopoietin-1

Glioblastoma (GBM) is pathologically characterized by highly malignant neoplastic cells, focal necrosis and aberrant blood vessels composed of disorganized endothelial cells and pericytes. The recent cancer microarray database revealed upregulation of fibulin-7 (Fbln7), a member of the fibulin family, but provided no information on the tissue localization or biological function. In the present study, we demonstrated that Fbln7 is markedly overexpressed by the GBM tissue among astrocytic tumors, and immunolocalized mainly to endothelial cells and pericytes of the glomeruloid and hypertrophied microvessels. The production of Fbln7 by endothelial cells and pericytes was confirmed in cultured human umbilical vein endothelial cells (HUVEC) and human brain vascular pericytes (HBVP) and vascular endothelial growth factor (VEGF) stimulated the Fbln7 expression in HUVEC. Fbln7 bound to angiopoietin-1, but not angiopoietin-2 or Tie2 receptor, through interaction between the N-terminal portions of Fbln7 and angiopoietin-1, and it blocked phosphorylation of Tie2 receptor in HUVEC. In a coculture assay using HUVEC and HBVP, multilayered and irregular-shaped tube-like structures of HUVEC were induced by treatment with a high concentration of VEGF. This was accompanied by Fbln7 overproduction by HUVEC and angiopoietin-1 expression by HBVP. The production of aberrant VEGF-induced tube-like structures was attenuated by treatment with antibody or synthetic peptides specific to the Fbln7 N-terminal domain or knockdown of Fbln7. These data demonstrate that Fbln7 is overexpressed by endothelial cells and pericytes of the abnormal microvessels in GBM, and suggest that Fbln7 may contribute to the aberrant vessel formation by modulation of the angiopoietin-1/angiopoietin-2-Tie2 axis.

A Single-Cell Transcriptome Atlas of the Mouse Glomerulus

Background Three different cell types constitute the glomerular filter: mesangial cells, endothelial cells, and podocytes. However, to what extent cellular heterogeneity exists within healthy glomerular cell populations remains unknown.Methods We used nanodroplet-based highly parallel transcriptional profiling to characterize the cellular content of purified wild-type mouse glomeruli.Results Unsupervised clustering of nearly 13,000 single-cell transcriptomes identified the three known glomerular cell types. We provide a comprehensive online atlas of gene expression in glomerular cells that can be queried and visualized using an interactive and freely available database. Novel marker genes for all glomerular cell types were identified and supported by immunohistochemistry images obtained from the Human Protein Atlas. Subclustering of endothelial cells revealed a subset of endothelium that expressed marker genes related to endothelial proliferation. By comparison, the podocyte population appeared more homogeneous but contained three smaller, previously unknown subpopulations.Conclusions Our study comprehensively characterized gene expression in individual glomerular cells and sets the stage for the dissection of glomerular function at the single-cell level in health and disease.

LPS‑induced downregulation of microRNA‑204/211 upregulates and stabilizes Angiopoietin‑1 mRNA in EA.hy926 endothelial cells

Angiopoietin-1 (ANG-1), a ligand of the endothelial cell-specific TIE2 surface receptor, acts in a complementary and coordinated manner with vascular endothelial growth factor during the process of angiogenesis. ANG-1 can be used as a clinically informative biomarker of disease severity and outcome in severe sepsis. The epithelium-specific Ets transcription factor 1 can activate ANG-1 transcription in the setting of inflammation; however, relatively little is known about the regulation of ANG-1 by microRNAs (miRs). It was observed that lipopolysaccharide (LPS) significantly increased ANG-1 mRNA and protein expression in EA.hy926 cells. ANG-1 was identified as a potential target gene of miR-204 and miR-211. Overexpression of miR-204/211 partially reversed the LPS-induced ANG-1 expression in EA.hy926 cells. Furthermore, overexpression of miR-204/211 significantly reduced the activity of a luciferase reporter gene containing the wild-type ANG-1 3′-untranslated region (UTR), but did not influence the activity of a luciferase reporter gene containing the ANG-1 3′-UTR with a mutated miR-204/211 binding site, confirming that miR-204/211 can bind to the ANG-1 3′-UTR and post-transcriptionally regulate ANG-1. Additionally, LPS enhanced the stability of ANG-1 mRNA by reducing the abundance of miR-204/211. Overexpression of miR-204/211 reduced the migration of EA.hy926 cells in vitro. The present study demonstrated that ANG-1 is a novel direct target gene of miR-204 and miR-211; in addition, LPS was able to inhibit this effect by reducing the expression of miR-204 and miR-211.

All-trans retinoic acid suppresses the angiopoietin-Tie2 pathway and inhibits angiogenesis and metastasis in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is the second common cancer in Henan province and is well-known for aggressiveness and dismal prognosis. Adjuvant therapies, chemotherapy, radiotherapy and endoscopic treatment have not improved survival rates in patients with late stage esophageal carcinoma. All-trans retinoic acid (ATRA) is the active ingredient of Vitamin A and affects a wide spectrum of biological processes including development, growth, neural function, immune function, reproduction, and vision. It is one of the most potent therapeutic agents used for treating cancers, especially lung adenocarcinomas. ATRA inhibits metastatic potential and angiogenesis in several tumor models. We investigated the effects of ATRA on the expression of angiopoietin 1 (Ang-1), angiopoietin 2 (Ang-2) and receptor Tie-2 in EC1 cells in vitro. We also assessed the growth and migration of EC1 cells in vitro. ATRA treatment caused 29.5% and 40.3% reduction of the growth of EC1 cells after 24 hours and 48 hours, relative to the control. ATRA plus fluorouracil treatment reduced the viability more strongly than either drug alone, indicating an additive effect. Moreover, ATRA decreased EC1 migration by 87%. Furthermore, ATRA treatment led to a marked decrease of the transcript levels of Ang-1, Ang-2, Tie-2, VEGF, and VEGF receptors, as assessed by real-time RT-PCR. Importantly, the protein levels of Ang-1, Ang-2 and Tie-2 were reduced by ATRA treatment. In vivo, we found ATRA treatment suppressed the tumor growth and improved the cachexia of mice. Importantly, ATRA treatment decreased the expression of CD31, Ang-1, Ang-2 and Tie-2 in subcutaneous tumors of EC1 cells. Collectively, our findings demonstrate that ATRA exhibits a dose- and temporal-dependent effect on the metastatic behavior, suppresses the angiopoietin-Tie2 pathway and inhibits angiogenesis and the progression of xenograft tumors of EC1 cells.