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Query: UMLS:C1519670 (tumor angiogenesis)
 6,052 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The roles played by the endogenous angiogenesis inhibitor thrombospondin-1 (TSP-1) in the early stages of multi-step carcinogenesis and in the control of hematogenous versus lymphatic metastasis are unknown. To investigate these issues we compared tumor development in normal mice and in transgenic mice with targeted overexpression of TSP-1 in the epidermis following a standard two-step chemical skin carcinogenesis regimen. Overexpression of TSP-1 resulted in delayed and reduced development of premalignant epithelial hyperplasias, but did not inhibit the malignant conversion to squamous cell carcinomas. TSP-1 overexpression also suppressed tumor angiogenesis and distant organ metastasis, but failed to inhibit tumor-associated lymphangiogenesis or lymphatic tumor spread to regional lymph nodes. Concomitant with these results, we found that the endothelial TSP-1 receptor CD36 was mostly absent from cutaneous lymphatic vessels. Our findings indicate the potential use of TSP-1 for the prevention of premalignant stages of tumorigenesis and are likely to have implications for the further development of anti-angiogenic cancer therapies.
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PMID:Thrombospondin-1 selectively inhibits early-stage carcinogenesis and angiogenesis but not tumor lymphangiogenesis and lymphatic metastasis in transgenic mice. 1243 45

Cyclooxygenase-2 (COX-2), the inducible COX isozyme, plays a key role in intestinal tumorigenesis. We have demonstrated recently that COX-2 protein is induced in the polyp stroma near the intestinal luminal surface in the Apc(Delta716) mouse, a model for human familial adenomatous polyposis, and stimulate tumor angiogenesis. However, the precise cell types that express COX-2 are still to be determined. By immunohistochemical analysis, here we show that the majority of COX-2-expressing cells in the intestinal polyps of Apc(Delta716) mice are fibroblasts and endothelial cells. Furthermore, the COX-2-expressing cells in human familial adenomatous polyposis polyps are also fibroblasts and endothelial cells. In contrast, bone marrow-derived cells such as macrophages and leukocytes express little COX-2 protein in the intestinal polyps. These results clearly indicate that fibroblasts and endothelial cells play important roles in polyp expansion by expressing COX-2, resulting in tumor angiogenesis.
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PMID:Cyclooxygenase-2 expression in fibroblasts and endothelial cells of intestinal polyps. 1246 Aug 97

The role of angiogenesis in tumorigenesis is widely accepted. Therefore, it is mandatory to develop a clinically useful method for assessing tumor angiogenesis. This study was designed to compare the 'in vivo' and 'in vitro' methods for assessing angiogenesis and to evaluate their clinical application using cervical carcinoma as a model. Ninety women with stages IB-IIA cervical carcinoma exhibiting visible cervical tumors by transvaginal ultrasound were enrolled in this study. All patients underwent radical abdominal hysterectomy and pelvic lymph node dissection. Vascularity index (VI) was assessed by power Doppler ultrasound and a quantitative image processing system. The microvessel density (MVD) of the excised tumors was immunohistochemically assessed. Both the enzyme immunoassay and immunohistochemistry methods were performed for assessing the protein levels of vascular endothelial growth factor (VEGF) in tumor tissues. Significantly higher VI, MVD and cytosol VEGF concentrations were detected in tumors with deep stromal invasion (>or=1/2 thickness) (11.43 +/- 7.25 vs. 5.87 +/- 6.81, P < 0.001; 53.0 vs. 37.0, P = 0.006, 550.0 vs. 86.0 pg/mg, P < 0.001), lymphatic invasion (12.21 +/- 7.89 vs. 6.86 +/- 6.29, P < 0.001; 53.0 vs. 40.0, P = 0.038; 930.0 vs. 110.0 pg/mg, P = 0.002), and pelvic lymph node metastasis (17.15 +/- 8.58 vs. 7.83 +/- 6.41, P < 0.001; 54.0 vs. 39.0, P = 0.02; 964.0 vs. 131.0 pg/mg, P = 0.002). VEGF-rich tumors detected by immunohistochemistry also revealed higher VI (12.26 +/- 7.96 vs. 8.05 +/- 7.62, P = 0.012), MVD (53.0 vs. 37.5, P = 0.01) and cytosol VEGF levels (745.0 vs. 98.0 pg/mg, P = 0.002). The relationships between VI values, MVD values and cytosol VEGF concentrations were linear (VI vs. MVD, r = 0.38, P < 0.001; VI vs. VEGF, r = 0.78, P < 0.001; MVD vs. VEGF, r = 0.29, P = 0.006). As revealed by the receiver operating characteristic (ROC) curve analysis, VI is better than MVD and VEGF in predicting lymph node metastasis. In conclusion, there is histological, molecular and clinical evidence supporting VI as a useful 'in vivo' indicator of tumor angiogenesis, particularly for predicting lymph node metastases in cervical carcinomas.
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PMID:Comparison between 'in vivo' and 'in vitro' methods for evaluating tumor angiogenesis using cervical carcinoma as a model. 1451 9

Hepatocyte growth factor/scatter factor (HGF/SF), acting through the Met receptor, plays an important role in most human solid tumors, and inappropriate expression of this ligand-receptor pair is often associated with poor prognosis. The molecular basis for the malignant potential of the HGF/SF-Met signal in cancer cells has mostly been attributed to its mitogenic and invasive properties. However, HGF/SF also induces angiogenesis, but the signaling mechanism has not been fully explained, nor has this activity been directly associated with HGF/SF-Met-mediated tumorigenesis. It is known that HGF/SF induces in vitro expression of vascular endothelial growth factor (VEGF), a key agonist of tumor angiogenesis; by contrast, thrombospondin 1 (TSP-1) is a negative regulator of angiogenesis. Here, we show that, in the very same tumor cells, in addition to inducing VEGF expression, HGF/SF dramatically down-regulates TSP-1 expression. We show that TSP-1 shut-off plays an important, extrinsic role in HGF/SF-mediated tumor development, because ectopic expression of TSP-1 markedly inhibits tumor formation through the suppression of angiogenesis. Interestingly, although VEGF-induced expression is sensitive to inhibitors of several pathways, including mitogen-activated protein kinase, phosphoinositide 3-kinase, and signal transducer and activator of transcription 3, TSP-1 shut-off by HGF/SF is prevented solely by inhibiting mitogen-activated protein kinase activation. These studies identify HGF/SF as a key switch for turning on angiogenesis. They suggest that TSP-1 is a useful antagonist to tumor angiogenesis and that it may have therapeutic value when used in conjunction with inhibitors of VEGF.
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PMID:Hepatocyte growth factor/scatter factor mediates angiogenesis through positive VEGF and negative thrombospondin 1 regulation. 1455 67

Id genes regulate tumor angiogenesis and loss of Id1 inhibits tumor xenograft growth in mice. Here we evaluate the role of Id1 in a more clinically relevant tumor model system using a two-step chemical carcinogenesis protocol. Remarkably, we find that Id1-/- mice are more susceptible to skin tumorigenesis compared to their wild-type counterparts. Cutaneous neoplasms in Id1-/- mice show increased proliferation without alterations in tumor angiogenesis; however, Id1-/- mice possess 50% fewer cutaneous gammadelta T cells than their wild-type counterparts due to an intrinsic migration defect associated with loss of expression of the chemokine receptor, CXCR4. We suggest that there are important differences between the mechanisms of angiogenesis in transplanted and autochthonous tumors and that these findings will have significant implications for the potential utility of antiangiogenic therapies in cancer.
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PMID:Disruption of Id1 reveals major differences in angiogenesis between transplanted and autochthonous tumors. 1458 56

Angiogenesis is deeply involved in the progression of major diseases such as cancer, diabetes, and rheumatoid arthritis. Molecular mechanism on angiogenesis was extensively studied, and several signaling systems including VEGF (VEGF-A), angiopoietin, PDGF, and ephrin were shown to be crucial for physiological angiogenesis. Interestingly, among these factors, VEGF appears to play key roles in most of the pathological angiogenesis, and other factors are considered to have additional effects on its development depending on the situation. VEGF binds and activates two tyrosine kinase receptors, VEGFR-1 (Flt-1) and VEGFR-2 (KDR/Flk-1), and stimulates endothelial cell growth, survival, and vascular permeability. VEGF induces not only tumor angiogenesis but also blood-vessel-dependent metastasis. Based on the importance of VEGF in diseases, many companies and institutes are now trying to generate appropriate small molecules as well as proteins that strongly antagonize the VEGF-VEGFR system. Several molecules quite effective for suppression of tumorigenesis and pathological angiogenesis in animal models are under clinical trials.
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PMID:VEGF-receptor inhibitors for anti-angiogenesis. 1463 4

Non-small cell lung cancer (NSCLC) is cured with surgery in a minority of affected persons. Chemotherapy and radiation can palliate and extend survival of patients with disease not amenable to surgery. Consequently, new treatment options are urgently needed. In the era of molecularly targeted therapeutics, the recent direction in cancer research has been to identify and modulate specific events in tumorigenesis. Angiogenesis, or new vessel formation, is one such event elucidated to be fundamental to the development, growth, and metastasis of cancers and is one of the characteristics that differentiates tumor from host. Thus, targeting of tumor neovasculature continues to generate tremendous enthusiasm and effort in drug development. Extensive research into the role of angiogenesis in NSCLC has produced a host of novel targets; their potential inhibitors, now numbering over 40, are in various phases of clinical testing around the world. The current lead compounds include inhibitors of matrix metalloproteinases, angiogenic growth factors and their receptor tyrosine kinases. Despite their impressive activity in animal models, definitive evidence of their antitumor activity in humans is yet to be established. We face several challenges as we look to advance the field of antiangiogenesis for the treatment of cancer, namely, the need for a better understanding of the optimal timing and dosing of antiangiogenic agents, the validation of imaging and quantification methods of tumor angiogenesis, and a new clinical trials design for a more expedient evaluation of novel cytostatic target modulators.
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PMID:Angiogenesis in non-small cell lung cancer. A new target for therapy. 1472 35

The histopathology and the epidemiology of human cancers, as well as studies of animal models of tumorigenesis, have led to a widely accepted notion that multiple genetic and epigenetic changes have to accumulate for progression to malignancy. Formation of new blood vessels (tumor angiogenesis) has been recognized, in addition to proliferative capabilities and ability to down-modulate cell death (apoptosis), as essential for the progressive growth and expansion of solid tumors. Mice overexpressing activated forms of oncogenes or carrying targeted mutations in tumor suppressor genes have proven extremely useful for linking the function of these genes with specific tumor features such as continuous proliferation, escape from apoptosis, invasion and neo-angiogenesis. The interbreeding of these mice allows for studying the extent of cooperativity between different genetic lesions in disease progression, leading to a greater understanding of multi-stage nature of tumorigenesis.
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PMID:Angiogenesis in transgenic models of multistep angiogenesis. 1501 54

The late stages of human breast cancer development are poorly understood complex processes associated with the expression of genes by cancers that promote specific tumorigenic activities, such as angiogenesis. Here, we describe the identification of periostin as a mesenchyme-specific gene whose acquired expression by human breast cancers leads to a significant enhancement in tumor progression and angiogenesis. Undetectable in normal human breast tissues, periostin was found to be overexpressed by the vast majority of human primary breast cancers examined. Tumor cell lines engineered to overexpress periostin showed a phenotype of accelerated growth and angiogenesis as xenografts in immunocompromised animals. The underlying mechanism of periostin-mediated induction of angiogenesis was found to derive in part from the up-regulation of the vascular endothelial growth factor receptor Flk-1/KDR by endothelial cells through an integrin alpha(v)beta(3)-focal adhesion kinase-mediated signaling pathway. These findings demonstrate the presence of a novel mechanism by which tumor angiogenesis is acquired with the expression of a mesenchyme-specific gene as a crucial step in late stages of tumorigenesis.
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PMID:Acquired expression of periostin by human breast cancers promotes tumor angiogenesis through up-regulation of vascular endothelial growth factor receptor 2 expression. 1508 92

Cancer cells promote angiogenesis early in tumorigenesis because cancer cells require oxygen and nutrients for their survival they need to be supported by blood vessels. The angiogenic switch is driven by several proangiogenic factors, vascular endothelial growth factor (VEGF), interleukin-8 (IL-8), basic fibroblast growth factor (bFGF) and others. These proangiogenic factors are released from not only cancer cells but also various stromal cells by various stimulations, mutations or inflammation. From our experimental results using human lung cancer cell lines, survival factors in each cancer cell line are different. This makes cancer therapy difficult. Various angiogenesis inhibitors have been developed to block tumor angiogenesis. However we need to think how and when to use angiogenesis inhibitors together with conventional chemotherapeutic agents.
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PMID:[Screening of antiangiogenic compound]. 1511 93


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