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

A "rod-shaped tubulated body" (tubular body) was first described by Weibel and Palade in the vascular endothelial cells of various organs in both man and animals. This is now considered to be an organelle specific to the endothelial cell, but its function is still unknown. Both in experimental and human pathology this organelle has been observed more often in either seemingly young or abnormal endothelial cells of the blood vessels in tissue regeneration, inflammation, brain tumors among others. This report deals with ultrastructural study of two surgical cases of cerebellar neoplasm, in which the vascular endothelium was examined for a tubular body. The first case was a 12-year-old boy with cerebellar hemangioblastoma, and the second a 36-year-old female who had a history of renal cell carcinoma removed approximately 5 years previously. Histological diagnosis of the cerebellar tumor in the latter case was indetermined, because a part of the tumor consisted of clear cells suggestive of clear cell carcinoma and another part of well developed endothelial cells and vascular channels apparently indicative of hemangioblastoma. The findings of the ultrastructural study were rather compatible with that of renal cell carcinoma metastatic to the cerebellum although inconclusive. The tubular body observed in the endothelial cells of those tumor vessels consisted of a membrane-limited round, oval or elongated shaped intracytoplasmic body which contained tubules of 170 to 200 A outer diameter with approximately 50 to 60 A thickness. The tubules were arranged mostly in a parallel fashion along their long axis. In the first type of tubular body they were embedded in a relatively pale matrix, and in the second their arrangement appeared to be more compact. The third tubular body, so far undescribed in human endothelial cells except in our previous communication, showed an irregularly and markedly enlarged matrix, surrounded by a limiting membrane which was occasionally observed connected with either a coated vesicle or cytoplasmic membrane. Abundant tubules were intermingled without showing a particular arrangement. Morphological and functional significance of the third type tubular body is unknown, but it might represent a pathological change of a tubular body in cerebellar neoplasms. These findings might give us some clues in understanding a tumor angiogenesis.
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PMID:[A specific organelle in the vascular endothelial cells of cerebellar neoplasms (author's transl)]. 123 7

Implantation of human renal adenocarcinoma in the rabbit cornea has resulted in new vascular growth from the limbus toward the tumor implant. This suggests that renal adenocarcinoma elaborates tumor angiogenesis factor (TAF) which stimulates endothelial cell growth. Such a substance could conceivably be responsible for the luxuriant vascularity of most renal adenocarcinomas. Conversely, absence or diminished secretion of TAF may be responsible for the hypovascular papillary renal adenocarcinomas and their recognized relatively benign clinical behavior.
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PMID:Detection of tumor angiogenesis factor in adenocarcinoma of kidney. 242 3

Mutations or loss of both alleles of the von Hippel-Lindau (VHL) tumor suppressor gene has been documented in sporadic renal cell carcinomas and neoplasms that arise in individuals having the VHL syndrome. The well-vascularized phenotype of tumors that form in VHL disease let us consider vascular endothelial growth factor (VEGF) as a mediator of tumor growth in VHL disease. Human renal carcinoma cells that either lacked endogenous wild-type VHL or were transfected with an inactive mutant VHL showed deregulated expression of VEGF on the mRNA and protein level that was reverted by introduction of wild-type VHL. Stimulation of proliferation of endothelial cells by conditioned medium of cells expressing mutant VHL was almost abolished by neutralizing the VEGF. In contrast, expression of basic fibroblast growth factor and of c-myc proto-oncogene was not affected by VHL. Our data suggest VEGF as the key tumor angiogenesis factor in VHL disease.
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PMID:Reversion of deregulated expression of vascular endothelial growth factor in human renal carcinoma cells by von Hippel-Lindau tumor suppressor protein. 862 3

The mechanism of action of anticancer chemotherapeutic agents is mainly thought to be due to a direct inhibition of tumor cell proliferation. The enhanced endothelial cell proliferation rate in tumor specimens raised the question of whether therapeutic effects of chemotherapeutic agents might be at least partially attributed to inhibition of tumor angiogenesis. In the present study, we investigated the potential effects of chemotherapeutic agents on human renal carcinoma angiogenesis with the alginate implantation model in mice. For the first time, we also compared results from the angiogenesis model with the inhibitory effects on growth of s.c. xenografts in nude mice. Vincristine and bleomycin exerted strong inhibition of tumor angiogenesis in both carcinoma lines close to the level of the standard antiangiogenic agent O-chloroacetyl-carbamyl-fumagillol (AGM-1470; T/C 22%). Adriamycin reduced angiogenesis of Caki-2 cells (T/C 33%) but had no effect on Caki-1 angiogenesis (T/C 137%). Etoposide and 5-fluorouracil reduced Caki-1 tumor angiogenesis but had no effect on Caki-2. Despite antiangiogenic effects in both carcinoma lines, vincristine, bleomycin, and AGM-1470 significantly reduced only the growth of fast-growing Caki-1 s.c. xenografts but not the slow-growing Caki-2. Antivascular effects by bleomycin and AGM-1470 were also shown by a decrease of microvessel density in nude mouse xenografts. Our findings suggest that chemotherapeutic agents may exert inhibition of tumor angiogenesis, which could be exploitable by combination therapy of fast-growing tumors. The resistance of the slow-growing Caki-2 carcinoma against acute angiogenesis inhibition indicates a need for well-tolerated angiogenesis inhibitors. Our results also suggest the use of fast-growing s.c. xenografts for demonstrating growth inhibition by antiangiogenic compounds. Further characterization of antiangiogenic compounds considered for clinical application should, however, have its focus on slow-growing tumors, which are not accessible for most therapeutic strategies.
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PMID:Antiangiogenic chemotherapeutic agents: characterization in comparison to their tumor growth inhibition in human renal cell carcinoma models. 960 94

The transcription factor Sp1 is ubiquitously expressed and plays a significant role in the constitutive and induced expression of a variety of mammalian genes and may even contribute to tumorigenesis. Here, we describe a novel pathway whereby Sp1 promotes the transcription of vascular permeability factor/vascular endothelial growth factor (VPF/VEGF), a potent angiogenic factor, by interacting directly and specifically with protein kinase C zeta (PKC zeta) isoform in renal cell carcinoma. PKC zeta binds and phosphorylates the zinc finger region of Sp1. Moreover, in the presence of the wild type von Hippel-Lindau gene product, the interaction of Sp1 with PKC zeta is inhibited, and in this manner steady state levels of Sp1 phosphorylation are decreased significantly. Co-transfection of renal cell carcinoma cells and human fibrosarcoma cells with a plasmid overexpressing PKC zeta and VPF/VEGF promoter luciferase constructs results in activation of Sp1-mediated transcription, whereas expression of a dominant-negative mutant of PKC zeta repressed this activation. Taken together, our results suggest a new pathway of cell signaling through PKC zeta and provide an insight into PKC zeta and Sp1-dependent transcriptional regulation of VPF/VEGF expression and thus tumor angiogenesis.
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PMID:Activation of Sp1-mediated vascular permeability factor/vascular endothelial growth factor transcription requires specific interaction with protein kinase C zeta. 975 52

Angiogenesis is required for tumor formation. Several studies have demonstrated that tumor angiogenesis is regulated by a balance between proangiogenesis and antiangiogenesis factors and that this balance varies in different organ environments. To investigate whether expression of an angiogenesis inhibitor by cancer cells could alter this balance and prevent tumor formation in different organ environments, we engineered stable transfectants from RenCa mouse renal carcinoma cells and SW620 human colon carcinoma cells to constitutively secrete a mouse endostatin protein with c-myc and polyhistidine (His) tags. Production and secretion of the endostatin-c-myc-His fusion protein by endostatin-transfected cells were confirmed by immunofluorescence staining and Western blot analysis. The endostatin transfectants and control transfectants, stably transfected with a control plasmid, had similar in vitro growth rates compared with their parental cell lines. Conditioned medium from endostatin-transfected cells inhibited human umbilical vein endothelial cell proliferation by 36-51% compared with conditioned medium from control cells. After inoculation into mice, flank tumors from endostatin-transfected cells were 73-91% smaller than flank tumors from control cells after 3 weeks. Inoculation of a cell mixture containing 25% endostatin-transfected cells and 75% control cells resulted in inhibition of flank tumor formation as effective as after inoculation of 100% endostatin-transfected cells. Formation of lung metastases by RenCa endostatin-transfected cells and formation of liver metastases by SW620 endostatin-transfected cells were dramatically inhibited compared with formation of metastases by control cells. These findings demonstrate that endostatin can inhibit tumor formation in different organ environments and that gene delivery of endostatin into even a minority of tumor cells may be an effective strategy to prevent progression of micrometastases to macroscopic disease.
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PMID:Mouse endostatin inhibits the formation of lung and liver metastases. 1062 20

Antiangiogenic therapy is a promising new strategy to inhibit tumor growth and formation of metastases. Vascular endothelial growth factor (VEGF) and its receptors, VEGF-receptor 1 (VEGF-R1; FLT-1) and VEGF-R2 (KDR), have been shown to play a major role in tumor angiogenesis. PTK787/ZK 222584, a specific inhibitor of both VEGF-receptor tyrosine kinases, was investigated for its antitumoral and antiangiogenic activity in a murine renal cell carcinoma model. After intrarenal application of the renal carcinoma cells, mice develop a primary tumor and metastases to the lung and to the abdominal lymph nodes. Daily oral therapy with PTK787/ZK 222584 at a dose of 50 mg/kg resulted in a significant decrease of 61 and 67% in primary tumors after 14 and 21 days, respectively. The occurrence of lung metastases was significantly inhibited at both time points (98% reduction and 78% reduction, respectively). After 14 days, no lymph node metastases developed in the PTK787/ZK 222584-treated group, whereas after 21 days of treatment, the lymph node metastases were reduced by 87%. Vessel density in tumor tissues, detected by immunohistochemistry with an anti-CD31 antibody, was significantly decreased by PTK787/ZK 222584. Using color Doppler imaging ultrasound, significant changes in blood flow in the tumor feeding renal artery were found under treatment with PTK787/ZK 222584. Blood flow changes correlated with changes in vessel density but not with tumor volume. The compound was well tolerated in all in vivo experiments and had no significant effects on body weight or general well-being of the animals. This was in contrast to the animals treated with the antiangiogenic agent TNP-470. s.c. therapy with 30 mg/kg TNP-470 every other day had to be discontinued after 13 days because of animal weight loss (>20%) and ataxia. These results demonstrate that PTK787/ZK 222584 is a potent inhibitor of tumor growth, metastases formation, and tumor vascularization in murine renal cell carcinoma. Furthermore, we have been able to demonstrate that color Doppler imaging ultrasound can be used to measure blood flow to a tumor and that flow correlates with vessel density. Thus, this may be a valuable noninvasive method for monitoring the effects of antiangiogenic agents such as PTK787/ZK 222584 on tumor vasculature.
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PMID:Effects of PTK787/ZK 222584, a specific inhibitor of vascular endothelial growth factor receptor tyrosine kinases, on primary tumor, metastasis, vessel density, and blood flow in a murine renal cell carcinoma model. 1098 92

Clear cell renal carcinoma (CCRC) is a highly angiogenic tumor known to secrete vascular endothelial cell growth factor (VEGF). Endostatin is an endogenous antiangiogenic agent with antitumor activity in mice. The purpose of this study was to evaluate serum levels of endostatin in normal subjects and in patients with CCRC and to examine the relationship of these levels to circulating VEGF levels. Fifteen patients (mean age, 48 years) on a clinical protocol for stage IV CCRC at the National Cancer Institute were included in the study. Archived prenephrectomy serum samples were analyzed for endostatin and VEGF concentrations. Endostatin and VEGF levels were compared with those of an age-matched group of volunteer blood donors (n = 18) using a competitive enzyme immunoassay. Data were analyzed using the Mann-Whitney U test and the Spearman rank correlation. Median serum endostatin levels were 24.6 ng/ml (range, 15.1-54.0 ng/ml) in CCRC patients versus 14.1 ng/ml (range, 1.0-19.3 ng/ml) in healthy controls (P < 0.0001). Median VEGF levels were 3.4 ng/ml (range, 0.1-11.2 ng/ml) and 2.5 ng/ml (range, 0.1-4.2 ng/ml), respectively (P = 0.065). A highly significant correlation was observed between endostatin and VEGF levels among the CCRC patients (r = 0.81, P = 0.0003) but not among controls (r = -0.22, P = 0.37). Endostatin levels are detectable in serum from healthy subjects as well as from CCRC patients. Levels are significantly elevated and correlate with VEGF levels in CCRC patients. Elucidating the nature of this correlation may lend insight into the regulation of tumor angiogenesis in patients with renal cancer.
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PMID:Serum endostatin levels are elevated and correlate with serum vascular endothelial growth factor levels in patients with stage IV clear cell renal cancer. 1115 12

The objective of this study was to evaluate the utility of measuring microvessel fractal dimension (MFD) as a parameter of architectural microvascular complexity in localized renal cell carcinoma (RCC). Forty-nine patients with low-stage clear cell RCC were assessed in a 9-year follow-up retrospective study. Tumor vessels were visualized with the endothelial marker CD34. Tumor microvessel density (MVD) was measured by computerized morphometry. Fractal analysis of the RCC microvascular network was performed and the MFD was computed in each case. Correlation between tumor vascular parameters, histological grade, extent of tumor necrosis and patient survival were tested by uni- and multivariate analyses. A significant correlation was found between tumor grade and decreased survival (P = 0.04). The extent of macroscopic tumor necrosis also significantly correlated with poor prognosis (P = 0.0001). Survival analysis revealed a significantly higher MVD in patients who survived longer than 5 years as compared with those who died before the end of the 5-year follow-up period (MVD = 10.8 +/- 4.7% versus 6.4 +/- 3.7%; P = 0.03). MVD was also inversely associated with the extent of tumor necrosis (P = 0.03). Microvessel fractal dimension was significantly higher in low- as compared with high-grade tumors (1.55 +/- 0.11 versus 1.45 +/- 0.15; P = 0.03). Survival analysis revealed a significantly higher MFD in those who lived >5 years as compared with those who died earlier (1.56 +/- 0.11 versus 1.46 +/- 0.15; P = 0.02). The MFD was inversely associated with the extent of tumor necrosis (P = 0.01). Multivariate analysis revealed that the MFD was the only significant factor to correlate with tumor necrosis, and that tumor necrosis was the only independent predictor of patient survival. These results indicate that the analysis of MFD as a marker of tumor microvascular complexity may provide important prognostic information as well as novel insight into the biology of tumor angiogenesis.
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PMID:Microscopic analysis and significance of vascular architectural complexity in renal cell carcinoma. 1159 29

Many oncogenes induce expression of vascular endothelial growth factor (VEGF), a key factor in tumor angiogenesis. Phosphatidylinositol 3'-kinase (PI3K)/Akt is a common signaling pathway for oncogenes and tumor suppressor genes and is involved in VEGF regulation. Because hypoxia is a major stimulus for VEGF production, we examined the effects of LY294002, a selective PI3K inhibitor, on hypoxia-inducible factor (HIF)-1alpha and HIF-2alpha expression and on endogenous VEGF responses to hypoxia. A panel of breast cancer cell lines reflecting the different genetic changes occurring in human breast cancer was analyzed. LY294002 inhibited HIF-1alpha induction and phosphorylation under hypoxia. However, HIF-2alpha expression was not affected. Basal and hypoxia-inducible VEGF expression was reduced at both mRNA and protein levels by 50%. V12-ras overexpression resulted in an increase in hypoxia-induced HIF-1alpha and HIF-2alpha expression. This effect was blocked by PI3K inhibitor, demonstrating one mechanism for ras synergy with hypoxia-mediated induction of genes. The decreased HIF-1alpha expression was not dependent on VHL interaction because a renal carcinoma cell line with VHL mutation and constitutive high HIF-1alpha expression also showed down-regulation of HIF-1alpha after treatment with LY294002. These results have implications for the use of PI3K inhibitors to inhibit synergistic effects of hypoxia with a wide range of common oncogenes.
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PMID:Effects of ras and von Hippel-Lindau (VHL) gene mutations on hypoxia-inducible factor (HIF)-1alpha, HIF-2alpha, and vascular endothelial growth factor expression and their regulation by the phosphatidylinositol 3'-kinase/Akt signaling pathway. 1158 76


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