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Query: UMLS:C0178874 (tumor progression)
 40,807 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Vascular endothelial cells are ordinarily quiescent in adult humans and divide less than once per decade. When tumors reach a size of about 0.2-2.0mm in diameter, they become hypoxic and limited in size in the absence of angiogenesis. There are about 30 endogenous pro-angiogenic factors and about 30 endogenous anti-angiogenic factors. In order to increase in size, tumors undergo an angiogenic switch where the action of pro-angiogenic factors predominates, resulting in angiogenesis and tumor progression. One mechanism for driving angiogenesis results from the increased production of vascular endothelial growth factor (VEGF) following up-regulation of the hypoxia-inducible transcription factor. The human VEGF family consists of VEGF (VEGF-A), VEGF-B, VEGF-C, VEGF-D, and placental growth factor (PlGF). The VEGF family of receptors consists of three protein-tyrosine kinases and two non-protein kinase receptors (neuropilin-1 and -2). Owing to the importance of angiogenesis in tumor progression, inhibition of VEGF signaling represents an attractive cancer treatment.
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PMID:Vascular endothelial growth factor (VEGF) signaling in tumor progression. 1732 79

Neural alterations and aberrantly expressed nerve-specific factors promoting tumor progression are known to contribute to pancreatic cancer's extremely poor prognosis. Despite hints that axon guidance factor semaphorin 3A (SEMA3A) may function as a tumor inhibitor, its clinical importance and therapeutic potential have not yet been explored. The present study investigated the role of SEMA3A and its receptors-plexins A1-A4 (PLXNA1-A4) and neuropilin-1 (NRP1)-in pancreatic cancer. QRT-PCR and immunohistochemical analyses revealed overexpression of SEMA3A, NRP1 and PLXNA1 in metaplastic ducts, malignant cells and nerves of cancerous specimens, and showed that elevated levels of corresponding mRNA (6.8-fold, 2.0-fold and 1.5-fold, respectively) clearly correlated with negative clinicopathological manifestations such as shorter survival (SEMA3A and PLXNA1) and a lesser degree of tumor differentiation (NRP1) in Stages I-III patients. High SEMA3A expression in pancreata of Stage IV M1 patients and in peritoneal metastases, and consequent functional studies indicated that poor clinical outcome might be related to the ability of SEMA3A to promote dissemination and invasiveness of pancreatic cancer cells through activation of multiple pathways involving Rac1, GSK3b or p42/p44 MAPK, but not E- to N-cadherin switch, MMP-9 or VEGF induction. Thus, this study is the first to quantify expression of the SEMA3A system in human malignancy and to show that overexpression of SEMA3A by nerves and transformed cells leads to a SEMA3A-rich environment which may favor malignant activities of tumor cells. Furthermore, negative clinicopathological correlations suggest that SEMA3A might represent a novel intervention target but not a treatment option for pancreatic cancer patients.
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PMID:Association of axon guidance factor semaphorin 3A with poor outcome in pancreatic cancer. 1763 38

Angiogenesis is the hallmark of cancer, and development of aggressiveness of primary tumor depends on de novo angiogenesis. Here, using multiple in vitro and in vivo models, we report that osteopontin (OPN) triggers vascular endothelial growth factor (VEGF)-dependent tumor progression and angiogenesis by activating breast tumor kinase (Brk)/nuclear factor-inducing kinase/nuclear factor-kappaB (NF-kappaB)/activating transcription factor-4 (ATF-4) signaling cascades through autocrine and paracrine mechanisms in breast cancer system. Our results revealed that both exogenous and tumor-derived OPN play significant roles in VEGF-dependent tumor angiogenesis. Clinical specimen analysis showed that OPN and VEGF expressions correlate with levels of neuropilin-1, Brk, NF-kappaB, and ATF-4 in different grades of breast cancer. Consequently, OPN plays essential role in two key aspects of tumor progression: VEGF expression by tumor cells and VEGF-stimulated neovascularization. Thus, targeting OPN and its regulated signaling network could be a novel strategy to block tumor angiogenesis and may develop an effective therapeutic approach for the management of breast cancer.
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PMID:Osteopontin promotes vascular endothelial growth factor-dependent breast tumor growth and angiogenesis via autocrine and paracrine mechanisms. 2716 Mar 11

The E-cadherin transcriptional repressor Snail is a prognostic marker for metastatic breast carcinoma, as well as a critical determinant of tumor growth and recurrence. We define a non-angiogenic, autocrine function for the vascular endothelial growth factor-A (VEGF-A) in regulating Snail expression in breast tumor cells. The transfection of well-differentiated breast tumor cells with VEGF-A increases Snail mRNA and protein levels, resulting in reduced E-cadherin expression. Conversely, reducing endogenous VEGF-A expression in poorly differentiated breast tumor cells by siRNA transfection decreases Snail levels. Our studies demonstrate that VEGF and the VEGF receptor Neuropilin-1 increase Snail expression by suppressing the Glycogen Synthase Kinase-3 (GSK-3), an established inhibitor of Snail transcription and protein stability. The VEGF-A neutralizing antibody Avastin was recently approved by the FDA for the treatment of metastatic breast cancer. We present the provocative finding that beyond its anti-angiogenic activity, Avastin can reduce Snail expression in breast tumor cells. Collectively, this work describes a novel autocrine function for VEGF in breast tumor cells in driving the expression of Snail, a breast tumor progression factor. Based on our demonstration that Avastin reduces Snail expression in breast tumor cells, we propose that the treatment of early stage breast cancer patients with Avastin may impede tumor progression.
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PMID:Vascular endothelial growth factor-A stimulates Snail expression in breast tumor cells: implications for tumor progression. 1855 84

L1 cell adhesion molecule (L1CAM) is a transmembrane cell adhesion molecule initially defined as a promigratory molecule in the developing nervous system that appears to be also expressed in some endothelial cells. However, little is known about the functional role of L1CAM on endothelial cells. We observed that L1CAM expression was selectively enhanced on endothelium associated with pancreatic adenocarcinoma in situ and on cultured pancreatic tumor-derived endothelial cells in vitro. L1CAM expression of endothelial cells could be augmented by incubation with immunomodulatory cytokines such as tumor necrosis factor alpha, interferon gamma, or transforming growth factor beta 1. Antibodies to L1CAM and the respective ligand neuropilin-1 blocked tube formation and stromal cell-derived factor 1beta induced transmigration of tumor endothelial cells in vitro. L1CAM expression on tumor-derived-endothelial cells enhanced Panc1 carcinoma cell adhesion to endothelial cell monolayers and transendothelial migration. Our data demonstrate a functional role of L1CAM expression on tumor endothelium that could favor metastasis and angiogenesis during tumor progression.
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PMID:Enhanced L1CAM expression on pancreatic tumor endothelium mediates selective tumor cell transmigration. 1893 29

Placenta growth factor (PlGF) is a key regulator of pathological angiogenesis and its overexpression has been linked to neoplastic progression. To assess whether PlGF could have a role in malignant mesothelioma (MM), we analyzed the expression of PlGF, VEGF, and their cognate receptors (VEGF-R1 and VEGF-R2) and co-receptors (neuropilin-1 and neuropilin-2) in MM cell lines as well as in resected MM tissues, hyperplastic/reactive mesothelium and normal mesothelium. MM cell cultures expressed both ligands and the associated receptors to a variable extent and released different amounts of PlGF. As assessed by immunohistochemistry, PlGF expression was switched on in hyperplastic/reactive compared to normal mesothelium. Moreover, 74 and 94 percent of MM tissues overexpressed PlGF and VEGF-R1, respectively (p<0.05 MM vs normal mesothelium). Administration of recombinant PlGF-2 did not elicit a significant stimulation of MM cell growth, while it was associated with a transient phosphorylation of Akt, suggesting that PlGF-2 could activate downstream effectors of proliferative and cytoprotective signals via VEGF-R1 in MM cells. Indeed, the administration of an anti-PlGF antibody was found to cause a significant reduction of MM cell survival. In conclusion, our data demonstrate that, by acting as a survival factor, PlGF can play a role which goes beyond the stimulation of angiogenesis in MM. This evidence could help the rational design of new therapeutic interventions for this aggressive tumor.
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PMID:Placenta growth factor is a survival factor for human malignant mesothelioma cells. 1950 92

Neuropilin-1 (Nrp1) was recently described as a novel receptor for the pro-angiogenic molecule vascular endothelial growth factor (VEGF), indicating a role in tumor angiogenesis and tumor progression. Recent data confirm this assumption by demonstrating that some tumor and endothelial cells express Nrp1. Therefore, we wanted to investigate the potential role of Nrp1-knockdown on hepatoma and endothelial cell function in vitro and tumor growth in vivo. Nrp1 knockdown in SVEC4 - 10 and Hepa129 cells and its influence on signal transduction (MAPK pP38, pAKT, pERK1 / 2) was analyzed by Western blot. Effects on endothelial tube formation were assayed in an in vitro and in vivo matrigel assay. In vivo, effects of siRNA-Nrp1 were analyzed in a subcutaneous hepatoma model. To verify effects on endothelial and tumor cells in vivo, immunohistochemistry for proliferation, apoptosis and endothelial vessels was performed. LightCycler and Western blot analysis showed efficient inhibition of gene expression in SVEC4 - 10 and Hepa129 cells following siRNA-Nrp1 transfection. Signal transduction pathways were not influenced after siRNA-Nrp1 treatment compared to the controls. Endothelial tube formation was reduced by 59 % and 94 % in vitro and in vivo compared to controls, corresponding to reduced VCAM expression. Subcutaneous tumor growth was not influenced after siRNA treatment. Intratumoral proliferation was not altered after treatment with siRNA-Nrp1, whereas microvessel density and apoptosis were reduced after treatment with siRNA-Nrp1 compared to siRNA-Ctrl. In conclusion, inhibition of Nrp1 expression led to strong anti-endothelial effects, whereas tumor cells and tumor growth were not affected.
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PMID:Inhibition of neuropilin-1 by RNA-interference and its angiostatic potential in the treatment of hepatocellular carcinoma. 2007 92

Use of adequate adjuvant is necessary for induction of effective antitumor immune responses. To develop an effective adjuvant for cancer immunotherapy, we selected formalin-inactivated (f)-HSV as an adjuvant component, and analyzed the mechanisms underlying its adjuvant effects. First, we found that f-HSV can induce the tumor antigen-specific CTLs by enhancing antigen cross-presentation by dendritic cells (DCs), mainly through TLR2, but not TLR9. Next, f-HSV was also found to prevent the accumulation of myeloid-derived suppressor cells (MDSCs). We demonstrated that the expansion of MDSCs in the blood and spleen during tumor progression required B cells producing the inflammatory angiogenesis factors, vascular endothelial growth factor (VEGF)-A and neuropilin-1 (NRP-1), a co-receptor for VEGF receptor-2 (VEGFR-2). Interestingly, the transmembrane-type NRP-1 on B cells changed to soluble-type NRP-1 (sNRP-1) by f-HSV treatment. We further showed that the sNRP-1 and VEGF-A secreted from B cells by f-HSV treatment could abrogate the immunosuppressive ability of MDSCs. These results suggest that f-HSV can enhance antitumor immune responses as an adjuvant, not only through activation of DCs, but also inactivation of MDSCs via B cells.
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PMID:Adjuvant effects of formalin-inactivated HSV through activation of dendritic cells and inactivation of myeloid-derived suppressor cells in cancer immunotherapy. 2023 89

Vascular endothelial growth factor (VEGF) is critical for physiological and pathological angiogenesis. Within the tumor microenvironment, VEGF functions as an endothelial cell survival factor, permeability factor, mitogen, and chemotactic agent. The majority of these functions are mediated by VEGF-induced activation of VEGF receptor 2 (VEGFR2), a high affinity receptor tyrosine kinase expressed by endothelial cells and other cell types in the tumor microenvironment. VEGF can also ligate other cell surface receptors including VEGFR1 and neuropilin-1 and -2. However, the importance of VEGF-induced activation of these receptors in tumorigenesis is still unclear. We report the development and characterization of r84, a fully human monoclonal antibody that binds human and mouse VEGF and selectively blocks VEGF from interacting with VEGFR2 but does not interfere with VEGF:VEGFR1 interaction. Selective blockade of VEGF binding to VEGFR2 by r84 is shown through ELISA, receptor binding assays, receptor activation assays, and cell-based functional assays. Furthermore, we show that r84 has potent anti-tumor activity and does not alter tissue histology or blood and urine chemistry after chronic high dose therapy in mice. In addition, chronic r84 therapy does not induce elevated blood pressure levels in some models. The ability of r84 to specifically block VEGF:VEGFR2 binding provides a valuable tool for the characterization of VEGF receptor pathway activation during tumor progression and highlights the utility and safety of selective blockade of VEGF-induced VEGFR2 signaling in tumors.
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PMID:r84, a novel therapeutic antibody against mouse and human VEGF with potent anti-tumor activity and limited toxicity induction. 2070 May 12

Neuropilin-1 (NRP-1) is a non-tyrosine kinase receptor for vascular endothelial growth factor (VEGF) that was recently found to play a role in tumor functions. Previous studies demonstrated that NRP-1 was overexpressed in a number of human tumors, including glioblastoma (GBM). However, the role of NRP-1 in glioma progression has yet to be adequately elucidated. Thus, we examined the expression of NRP-1 in human glioma cell lines using Western blotting, and cell cycle distribution and proliferation by transfection of the U373 cell line with NRP-1 short interference RNA (siRNA). Results showed NRP-1 siRNA to significantly reduce NRP-1 gene expression, decrease in vitro cell proliferation and induce cell apoptosis in cultured glioma cells, along with the accumulation of cells in the G1 phase and a decrease in cells in the S phase. Our results further revealed that NRP-1 knockdown decreased the expression levels of Bcl-2 family proteins and deactivated extracellular signal-regulated kinase (ERK) and c-Jun-N-terminal kinase (JNK)/mitogen-activated protein kinase (MAPK) signaling pathways, closely associated with cancer progression. Thus, our results provide a molecular mechanism for the effect of NRP-1 in tumors, rendering NRP-1 an attractive candidate as a therapeutic target in certain types of cancer, such as GBM.
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PMID:RNA interference targeting NRP-1 inhibits human glioma cell proliferation and enhances cell apoptosis. 2184 23


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