Endoglin is necessary for angiogenesis in human ovarian carcinoma-derived primary endothelial cells

Endoglin (CD105, END) is upregulated in proliferating endothelial cells, suggesting potential therapeutic properties. However, it is not clear whether endoglin mediates an enhanced proliferative rate or may be upregulated as part of a negative feedback loop. To gain insights into context-dependent and cell type-dependent regulatory effects of endoglin, we studied its role properties in human ovarian carcinoma-derived endothelial cells (ODMECs). We isolated and cultured primary ODMECs from epithelial ovarian carcinoma tissue. ODMECs had higher expression of endoglin and VEGFR-2, and also exhibited enhanced spontaneous formation of vessel-like structures in vitro. Transfection of siRNA targeting endoglin in ODMECs cells resulted in the reduction of the proliferation and tube formation. These results indicate that a subset of ODMECs display abnormal angiogenic properties and this phenotype was blocked by decreasing endoglin levels, suggesting endoglin is essential for stimulating angiogenesis, and targeting it may be an attractive approach to anti-angiogenesis therapy for ovarian carcinoma.     

RhoC is essential for angiogenesis induced by hepatocellular carcinoma cells via regulation of endothelial cell organization

The angiogenesis induced by tumor cells is essential for metastasis of hepatocellular carcinoma. Available information suggests that RhoC participates in angiogenesis through regulation of vascular endothelial growth factor expression in tumor cells. For its broad functions in cell migration and cytoskeletal organization, we hypothesized that RhoC regulating angiogenesis does not exclusively depend on regulation of vascular endothelial growth factor expression. To address this question, in the present study, we used a retroviral small interfering RNA approach to selectively knockdown the expression of RhoC in a neovascularization model in vivo and in vitro. Our present results indicate that RhoC is the downstream regulator of vascular endothelial growth factor in endothelial cells and is essential for angiogenesis induced by vascular endothelial growth factor, notwithstanding that RhoC regulates the expression of vascular endothelial growth factor in tumor cells. Furthermore, we show that knockdown of RhoC is associated with the inhibition of invasion and migration but not apoptosis of endothelial cells. Knockdown of RhoC results in inhibition of endothelial cell organization through restraining the reorganization of F‐actin filaments, which represses endothelial cell network and sprout formation. In conclusion, our results demonstrate that knockdown of RhoC inhibits angiogenesis induced by tumor cells not only through effecting the release of vascular endothelial growth factor, but also through inhibiting endothelial cell migration and organization, which implies that it blocks tumor metastasis by specifically inhibiting RhoC in endothelial cells. (Cancer Sci 2008; 99: 2012–2018)     

Atiprimod is an inhibitor of cancer cell proliferation and angiogenesis

Atiprimod, a novel compound belonging to the azaspirane class of cationic amphiphilic drugs, exhibits both anti-proliferative and anti-angiogenic activities. Atiprimod inhibited proliferation of all human cancer cell lines included in the National Cancer Institute panel with IC50 values in the low micromolar range. Notably, metastatic cell lines were more sensitive to the compound compared to the non-metastatic cell lines derived from the same tumor tissue types. Atiprimod also induced apoptosis and activated both caspase-9 and caspase-3 in T84 colon carcinoma cells. Hence, the anti-proliferative activity could partly be due to its pro-apoptotic activity. Regarding angiogenesis in vitro, atiprimod inhibited both bFGF and VEGF induced proliferation and migration of human umbilical vein endothelial cells (HUVECs), resulting in disruption of cord formation. In addition, atiprimod also suppressed formation of new blood vessels in a chorioallantoic membrane assay. Previous studies have also shown that atiprimod treatment reduced production of IL-6, VEGF and inhibited activation of Stat3, a constitutively activated protein in majority of human cancers. Together these findings suggest that atiprimod acts on several molecules that are essential for tumor growth, invasion and metastasis.     

Suramin inhibits bFGF-induced endothelial cell proliferation and angiogenesis in the chick chorioallantoic membrane.

The effects of suramin, an inhibitor of growth factor mitogenic activity, were evaluated on basic fibroblast growth factor (bFGF)-induced proliferation of bovine aortic endothelial cells and on angiogenesis in the chorioallantoic membrane (CAM) of chick embryos. The role of bFGF gene expression in endothelial cell growth was also investigated by using an antisense oligodeoxynucleotide to bFGF. The 4-fold increase in [3H]-thymidine uptake in endothelial cells in vitro upon stimulation with 10 ng ml-1 of bFGF was inhibited by suramin 300 micrograms ml-1. bFGF antisense oligomer (10 microM) reduced [3H]-thymidine incorporation in exponentially growing cells by 76%; this effect was reversed by bFGF 10 ng ml-1. In the CAM of chick embryos suramin 50 micrograms was a more potent inhibitor of angiogenesis than the combination of heparin 60 micrograms/hydrocortisone 50 micrograms; the mean value of the area with reduced vascularity was significantly larger in suramin-treated CAMs (2.4 cm2) than in heparin/hydrocortisone (0.6 cm2), while the reduction of vascular density was similar (- 35 and - 29% compared to controls, respectively), In conclusion, the effects of treatments with bFGF and bFGF antisense oligomer demonstrate that bFGF plays a relevant role in endothelial cell proliferation and may be the target of suramin since the drug is able to suppress basal and bFGF-induced endothelial cell growth; in addition to this, suramin is a more potent angiogenesis inhibitor in the CAM than the combination of heparin/hydrocortisone.     

Importance of a collagen substratum for stimulation of capillary endothelial cell proliferation by tumour angiogenesis factor.

Tumour extracts were obtained from rat Walker 256 carcinoma and examined for the presence of tumour angiogenesis factor (TAF) in vivo before being used in tissue culture experiments. Capillary endothelial cells derived from cow brain white matter were used to study the effects of TAF-containing tumour extracts on cell proliferation in vitro. The cells were grown on two types of substrata: (1) plastic tissue culture dishes and (2) hydrated gels made of rat tail tendon type I collagen. Human platelets or platelet-released factors were introduced into the system because of the many inter-relationships known to exist between platelets, collagen and endothelial cells. If trypsin was used during the preparation of TAT, the resulting batches stimulated endothelial cell proliferation only when the cells were growing on a collagen substratum and either platelets or platelet-released factors were present in the growth medium. If incubation with trypsin was omitted from the TAF extraction procedure, the resulting batches stimulated cell growth both on plastic and on collagen. A synergistic interaction also occurred between these TAF-containing tumour extracts and platelet-released factors. This effect was always more marked when the cells were growing on collagen than when on plastic. These data suggest that the nature of the substratum affects the response of the endothelial cells to TAF and to platelet-released factors.     

Evidence of involvement of CD44 in endothelial cell proliferation,migration and angiogenesis in vitro

Angiogenesis is essential for tumor growth and metastasis. In the process of angiogenesis, the interaction between adhesive proteins of endothelial cells and extracellular matrix components plays an important role by mediating cell attachment, which is indispensable for their motility, and by transmitting the regulatory signals for cell locomotion and proliferation. In this study, we examined the hypothesis that CD44 expressed on the endothelial cell surface is involved in the angiogenesis process. The experiments using calf pulmonary artery endothelial cells (CPAE) and a human microvascular endothelial cell line (HMEC-I) show that a monoclonal antibody against CD44 (clone J 173) inhibits endothelial cell proliferation by about 30% and migration by 25–50%, and abolishes the stimulating effect of hyaluronan polysaccharides on endothelial cell migration and proliferation. This antibody also suppresses the capillary formation of CPAE in an in vitro model of angiogenesis using fibrin matrix. These results provide evidence of the involvement of endothelial-cell-associated CD44 in angiogenesis. © 1996 Wiley-Liss, Inc.     

Tamoxifen inhibits endothelial cell proliferation and attenuates VEGF-mediated angiogenesis and migration in vivo

INTRODUCTION: Angiogenesis is fundamental to tumour growth and vascular endothelial growth factor (VEGF) is one of the most potent proangiogenic cytokines known. We have previously demonstrated that tamoxifen reduces serum VEGF in certain cancer patients. We hypothesized that tamoxifen may attenuate the angiogenetic response to VEGF. METHODS: Human dermal microvessel endothelial primary cell cultures (HMEC) were incubated with tamoxifen (1.25-5.0 microg) or vehicle. Cell proliferation was quantified using 5-bromo-2'-deoxyuridine (BrdU) labelling endothelial cell proliferation assay. The effect of oral tamoxifen (20 mg/day) on VEGF-mediated angiogenesis in vivo was assessed using a Matrigel angiogenesis assay in the Sprague-Dawley rat. RESULTS: Tamoxifen (5.0 microg/ml) significantly reduced HMEC proliferation over 24 h when compared with cells treated with vehicle alone. Oral administration of tamoxifen in the rat (20 mg/day) significantly reduced endothelial cell proliferation and migration in response to VEGF. CONCLUSION: Tamoxifen (5.0 microg/ml) reduces proliferation of a VEGF-dependent endothelial cell line in vitro. In vivo, orally administered tamoxifen reduces VEGF-mediated angiogenesis in the rat. These findings indicate that tamoxifen may directly inhibit the effect of VEGF on the endothelial cell, in addition to its previously described effect of reducing serum VEGF levels. This data supports a role for tamoxifen in modulation of the VEGF-dependent angiogenic response to surgical trauma, particularly as an adjuvant therapy for VEGF-dependent tumours.     

Molecular polarity in endothelial cells and tumor-induced angiogenesis

Endothelial cells expose receptors for vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) at the abluminal, basal surface that work as basic regulators of tumor-induced angiogenesis. Their specific localization makes them susceptible to the activity of tumor-released stimulatory factors, like VEGF/VPF, which induce proliferation of the endothelial cell toward the extracellular matrix. At the same time, VEGF/VPF stimulates endothelial cells to expose tissue factor (TF), the high-affinity transmembrane receptor and cofactor for cellular initiation of the plasma coagulation protease cascades through the extrinsic pathway, so generating thrombin. Thrombin exerts a number of activities: it forms an extracellular fibrin barrier from the VEGF/VPF-dependent fibrinogen extravasation; it activates progelatinase-A (pro-MMP-2), which destroys the basal membrane, allowing proliferation of endothelial cells (ECs) in the novel tumoral fibrin matrix; finally, it induces EC proliferation, potentiating the VEGF effect. Another important factor exposed at the abluminal endothelial cell surface is membrane type 1 matrix metalloproteinase (MT1-MMP), a membrane-bound metalloproteinase, which also activates progelatinase-A, allowing an alternative pathway to that of thrombin to destroy the basal membrane. In addition, we will see that MT1-MMP is also engaged in a direct, cell-associated fibrinolytic activity, essential for tubulogenesis of the novel outsprouting capillary.     

Relationship between vascular endothelial growth factor expression and angiogenesis and cell proliferation of malignant gliomas in children

Thereismountingevidencethattumorangiogenesisisintimatelyrelatedtotumorgrowth,invasion,metastasisandprognosis.Tumorangiogenesisisregulatedbysomekindsofcytokinesintissues,suchasfibroblastgrowthfactor(FGF),transforminggrowthfactor(TGF),platelet-derivedgrowthfactor(PDGF)andvascularendothelialgrowthfactor(VEGF),amongwhich,VEGFisknowntobeparticularlyresponsiblefortheprocessofbraintumorangiogenesisVEGFinfluenceonbiologicalpropertiesofadultbraintumorhavebeenreportedinotherarticles.[1]Inthisstu…     

Weibel-Palade bodies in endothelial cells as a marker for angiogenesis in brain tumors

A transmission electron microscope study was made of eight childhood brain tumors divided up into three zones, center, edge, infiltrating zone, and also of adjacent "normal-looking" brain. In seven of eight tumors, the numbers of Weibel-Palade bodies in endothelial cells were significantly increased in peripheral zones compared with central zones. A similar significant increase was observed after treatment of chick chorioallantoic membranes with tumor angiogenesis factor. It is suggested that large numbers of Weibel-Palade bodies may be a marker for proliferating endothelial cells in vivo.     

循环内皮祖细胞与肿瘤血管生成

恶性肿瘤细胞可产生多种细胞因子,可使骨髓中的内皮祖细胞(EPC)动员至外周血,并将这些细胞募集到肿瘤组织的血管床,参与肿瘤的血管生成.EPC有望成为抗肿瘤血管生成的靶点或肿瘤基因治疗的载体.     

Choline kinase activation is a critical requirement for the proliferation of primary human mammary epithelial cells and breast tumor progression

Breast cancer is still one of the most important tumors among women in industrialized countries. Improvement in both understanding the molecular events associated with the disease and the development of new additional treatments is still an important goal to be achieved. Choline kinase (ChoK) is increased in human mammary tumors with high incidence, and this activation is associated with clinical variable indicators of greater malignancy. Here, we have investigated the role of ChoK in the development of breast cancer and found that ChoK is both necessary and sufficient for growth factor-induced proliferation in primary human mammary epithelial cells and an absolute requirement for the specific mitogenic response to heregulin in breast tumor-derived cells. These results demonstrate that ChoK plays an essential role in both normal human mammary epithelial cell proliferation and breast tumor progression. Furthermore, inhibition of ChoK shows a strong in vivo antitumor activity against human breast cancer xenografts. Thus, ChoK constitutes a novel bona fide molecular target for the treatment of breast cancer patients.     

循环内皮细胞与肿瘤血管生成的关系

 循环内皮细胞（CEC）是指外周血中测得的血管内皮细胞。其在健康人外周血中数量极少,而在动脉粥样硬化、糖尿病、红斑狼疮等疾病中明显增加,被认为是判断血管内皮细胞损伤情况特异而直接的指标。目前临床科研上常用流式细胞术检测计数和免疫磁珠分离法对CEC进行检测和计数。已有多项研究结果证实,CEC与肿瘤关系密切,现就对CEC的来源、检测、与肿瘤血管生成的关系以及在肿瘤预后监测的意义等进行综述。     

Luteolin inhibits vascular endothelial growth factor-induced angiogenesis; inhibition of endothelial cell survival and proliferation by targeting phosphatidylinositol 3'-kinase activity

In an attempt to identify phytochemicals contributing to the well-documented preventive effect of plant-based diets on cancer incidence and mortality, we have previously shown that certain flavonoids inhibit in vitro angiogenesis. Here, we show that the flavonoid luteolin inhibited tumor growth and angiogenesis in a murine xenograft model. Furthermore, luteolin inhibited vascular endothelial growth factor (VEGF)-induced in vivo angiogenesis in the rabbit corneal assay. In agreement, luteolin inhibited both VEGF-induced survival and proliferation of human umbilical vein endothelial cells (HUVECs) with an IC(50) of about 5 mumol/L. Luteolin inhibited VEGF-induced phosphatidylinositol 3'-kinase (PI3K) activity in HUVECs, and this inhibition was critical for both the antisurvival and antimitotic affects of the compound. Indeed, luteolin abolished VEGF-induced activation of Akt, a downstream target of PI3K conveying both survival and mitotic downstream signals. Because overexpression of a constitutively active form of Akt rescued HUVECs only from the antisurvival effects of luteolin, the result indicated that luteolin targeted mainly the survival signals of the PI3K/Akt pathway. With regard to its antimitotic activity, luteolin inhibited VEGF-induced phosphorylation of p70 S6 kinase (S6K), a downstream effector of PI3K responsible for G(1) progression. Indeed, VEGF-induced proliferation of HUVECs was sensitive to rapamycin, an inhibitor of p70 S6K activation. Surprisingly, luteolin did not affect VEGF-induced phosphorylation of extracellular signal-regulated kinase 1/2 mitogen-activated protein kinases, a pathway that is considered important for the mitotic effects of VEGF. Thus, blockade of PI3K by luteolin was responsible for the inhibitory effects of the compound on VEGF-induced survival and proliferation of HUVECs. The antisurvival effects of luteolin were mediated via blockage of PI3K/Akt-dependent pathways, whereas inhibition of the PI3K/p70 S6K pathway mediated the antimitotic effects of the compound.     

Baicalein and baicalin are potent inhibitors of angiogenesis: Inhibition of endothelial cell proliferation,migration and differentiation

In recent studies, we have shown that baicalein and baicalin, 2 major flavonoids of Scutellaria baicalensis Georgi, exhibit anticancer activity against several cancers in vitro. In our present study, we assessed their potential as anti-angiogenic agents in vivo employing chicken chorioallantoic membrane (CAM) assay and in vitro human umbilical vein endothelial cells (HUVECs) culture. When CAMs were treated with either baicalein or baicalin for 48 hr, the angiogenic response induced by basic fibroblast growth factor (bFGF) was markedly reduced in a dose-dependent manner. Further characterization showed that both flavonoids exhibited dual antiproliferative (at low dose) and apoptogenic (at high dose) effects on HUVECs. In biochemical analysis, treatment of HUVECs with baicalein and baicalin for 24 hr resulted in a dose-dependent decrease in the matrix metalloproteinase (MMP)-2 activity. Moreover, the migration of endothelial cells and the differentiation of endothelial cells into branching networks of tubular structures in vitro were also inhibited by these 2 flavonoids in a dose-dependent manner. Baicalein is more potent than baicalin in anti-angiogenesis in vivo as well as in vitro. Taken together, the results of our study provide evidence that baicalein and baicalin possess an anti-angiogenesis potential that is a previously unrecognized biologic activity.     

Cultured tumor cells produce chemotactic factors specific for endothelial cells: a possible mechanism for tumor-induced angiogenesis

The production of stimulants of endothelial cell motility by cultured tumor cells was studied. Spontaneously transformed murine fibroblasts in culture produced activity that stimulated migration of endothelial cells, while this kind of activity was not detected in media from cultures of the normal counterparts of the transformed cells. Furthermore, a line of murine tumor cells (HB4), known to induce vasoformative sarcomas in vivo, was found to produce in culture a strong chemoattractant specific for endothelial cells. Since the tumor-derived material also caused vessel ingrowth when implanted in the rabbit eye, these results suggest that the angiogenesis observed during tumor growth may involve chemoattractants for endothelial cells produced by tumor cells.     

Hedgehog-interacting protein is highly expressed in endothelial cells but down-regulated during angiogenesis and in several human tumors

Background  

The Hedgehog (Hh) signaling pathway regulates a variety of developmental processes, including vasculogenesis, and can also induce the expression of pro-angiogenic factors in fibroblasts postnatally. Misregulation of the Hh pathway has been implicated in a variety of different types of cancer, including pancreatic and small-cell lung cancer. Recently a putative antagonist of the pathway, Hedgehog-interacting protein (HIP), was identified as a Hh binding protein that is also a target of Hh signaling. We sought to clarify possible roles for HIP in angiogenesis and cancer.