Vascular endothelial growth factor: An important molecular target of curcumin.

The discovery of Vascular Endothelial Growth Factor (VEGF), the key modulator of angiogenesis, has triggered intensive research on anti-angiogenic therapeutic modalities. Although several clinical studies have validated anti-VEGF therapeutics, with few of them approved by the U.S. Food and Drug Administration (FDA), anti-angiogenic therapy is still in its infancy. Phytochemicals are compounds that have several metabolic and health benefits. Curcumin, the yellow pigment derived from turmeric (Curcuma longa L.) rhizomes, has a wide range of pharmaceutical properties. It has also been shown to inhibit VEGF by several studies. In this review, we elaborate the effect of curcumin on VEGF and angiogenesis and its therapeutic application.

Salvianolic acid B as an anti-emphysema agent I: In vitro stimulation of lung cell proliferation and migration, and protection against lung cell death, and in vivo lung STAT3 activation and VEGF elevation.

Emphysema causes progressive and life-threatening alveolar structural destruction/loss, yet remains irreversible and incurable to date. Impaired vascular endothelial growth factor (VEGF) signaling has been proposed as a new pathogenic mechanism, and if so, VEGF recovery may enable reversal of emphysema. Thus, we hypothesized that salvianolic acid B (Sal-B), a polyphenol in traditional Chinese herbal danshen, is an alveolar structural recovery agent for emphysema by virtue of VEGF stimulation/elevation via activation of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3), as stimulating lung cell proliferation and migration, and protecting against lung cell death. Using in vitro human lung microvascular endothelial (HMVEC-L) and alveolar epithelial (A549) cell systems, Sal-B was examined for 1) stimulation of cell proliferation by the MTT and BrdU assays; 2) promotion of cell migration by the scratch wound closure assay; 3) protection against emphysema-like induced cell death by the trypan blue exclusion and flow cytometry assays; and 4) mechanistic involvement of JAK2/STAT3/VEGF in these activities. Sal-B was also spray-dosed to the lungs of healthy rats for two weeks to verify the lung's STAT3 activation and VEGF elevation by western blot, as well as the absence of functional and morphological abnormalities. All the in vitro cell-based activities were concentration-dependent. At 25 µM, Sal-B 1) stimulated cell proliferation by 1.4-2.6-fold; 2) promoted migratory cell wound closure by 1.5-1.7-fold; and 3) protected against cell death induced with H2O2 (oxidative stress) and SU5416 (VEGF receptor blockade) by 49-86%. JAK2 and STAT3 inhibitors and VEGF receptor antagonist each opposed these Sal-B's activities by over 65%, suggesting the mechanistic involvement of JAK2/STAT3 activation and VEGF stimulation/elevation. In rats, Sal-B at 0.2 mg/kg enabled 1.9 and 1.5-fold increased STAT3 phosphorylation and VEGF elevation in the lungs, respectively, while causing no functional and morphological abnormalities. Hence, Sal-B was projected to be a new class of anti-emphysema agent capable of reversing alveolar structural destruction/loss via JAK2/STAT3/VEGF-dependent stimulation of lung cell proliferation and migration, and inhibition of induced lung cell death.

VEGF pathway-targeted therapy for advanced renal cell carcinoma: a meta-analysis of randomized controlled trials.

Immunotherapy which has been in practice for more than 20 years proves effective for the treatment of metastatic renal cell carcinoma (mRCC). Anti-angiogenesis-targeted therapy has recently been identified as a promising therapeutic strategy for mRCC. This study was aimed to evaluate the effectiveness of vascular endothelial growth factor (VEGF) pathway-targeted therapy for mRCC by comparing its effectiveness with that of immunotherapy. The electronic databases were searched. Randomized controlled trials (RCTs) on comparison of VEGF inhibiting drugs (sorafenib, sunitinib and bevacizumab) with interferon (IFN) or placebo for mRCC treatment were included. Data were pooled to meta-analyze. A total of 7 RCTs with 3451 patients were involved. The results showed that anti-VEGF agents improved progression-free survival (PFS) and offered substantial clinical benefits to patients with mRCC. Among them, sunitinib had a higher overall response rate (ORR) than IFN (47% versus 12%, P<0.000001). Bevacizumab plus IFN produced a superior PFS [risk ratio (RR): 0.86, 95% confidence interval (CI): 0.76-0.97; P=0.01] and ORR (RR: 2.19; 95% CI: 1.72-2.78; P<0.00001) in patients with mRCC over IFN, but it yielded an increase by 31% in the risk of serious toxic effects (RR: 1.31; 95% CI: 1.20-1.43; P<0.00001) as compared with IFN. The overall survival (OS) was extended by sorafenib (17.8 months) and sunitinib (26.4 months) as compared with IFN (13 months). It was concluded that compared with IFN therapy, VEGF pathway-targeted therapies improved PFS and achieved significant therapeutic benefits in mRCC. However, the risk to benefit ratio of these agents needs to be further evaluated.

[Novelties in the treatment for advanced renal-cell cancer]. / Új lehetoségek a vesedaganatok onkológiai kezelésében.

Therapeutic options in advanced renal-cell cancer have expanded through better understanding of molecular pathology and development of novel targeted therapeutics. Vascular endothelial growth factor, the key ligand of angiogenesis, has a major role in the progression of vascularized kidney tumors and this is the target molecule of modern medications. The three types of the mechanism of action of current therapies are: monoclonal antibodies blocking directly vascular endothelial growth factor ligand (bevacizumab), tyrosine-kinase inhibitors blocking vascular endothelial growth factor receptors (sorafenib, sunitinib, pazopanib) and inhibitors of the intracellular mTOR-kinase (temsirolimus, everolimus). Based on randomized studies, sunitinib, pazopanib or interferon-α-bevacizumab combination should be the first-line therapy in patients with good/moderate prognosis, while temsirolimus is recommended in those with poor prognosis. Following an ineffective cytokine therapy sorafenib or pazopanib are the second-line treatment. In case of tyrosine-kinase inhibitor inefficacy, current evidence favors everolimus. Patient outcome can further be improved by the involvement of more modern and effective target products.

Inhibition of hypoxia inducible factor-1alpha by dihydroxyphenylethanol, a product from olive oil, blocks microsomal prostaglandin-E synthase-1/vascular endothelial growth factor expression and reduces tumor angiogenesis.

PURPOSE: 2-(3,4-dihydroxyphenil)-ethanol (DPE), a polyphenol present in olive oil, has been found to attenuate the growth of colon cancer cells, an effect presumably related to its anti-inflammatory activity. EXPERIMENTAL DESIGN: To further explore the effects of DPE on angiogenesis and tumor growth we investigated the in vivo efficacy of DPE in a HT-29 xenograft model and in vitro activities in colon cancer cells exposed to interleukin-1beta (IL-1beta) and prostaglandin E-2 (PGE-2). RESULTS: DPE (10 mg/kg/day for 14 days) inhibited tumor growth, reducing vessel lumina and blood perfusion to tumor, and diminished expression of hypoxia inducible factor-1alpha (HIF-1alpha), vascular endothelial growth factor (VEGF), and microsomal prostaglandin-E synthase-1 (mPGEs-1). In vitro, DPE (100 mumol/L) neither affected cell proliferation nor induced apoptosis in HT-29 and WiDr cells. DPE prevented the IL-1beta-mediated increase of mPGEs-1 expression and PGE-2 generation, as it did the silencing of HIF-1alpha. Moreover, DPE blocked mPGEs-1-dependent expression of VEGF and inhibited endothelial sprouting induced by tumor cells in a coculture system. PGE-2 triggers a feed-forward loop involving HIF-1alpha, which impinges on mPGEs-1 and VEGF expression, events prevented by DPE via extracellular signal-related kinase 1/2. The reduction of PGE-2 and VEGF levels, caused by DPE, was invariably associated with a marked decrease in HIF-1alpha expression and activity, independent of proteasome activity, indicating that the DPE effects on tumor growth and angiogenesis are dependent on the inhibition of HIF-1alpha translation. CONCLUSIONS: We show that the in vivo DPE antitumor effect is associated with anti-inflammatory and antiangiogenic activities resulting from the downregulation of the HIF-1alpha/mPGEs-1/VEGF axis.

[Advanced renal carcinomas with special situations. How to treat them?]. / Cancers du rein avancés en situations particulières. Comment les traiter ?

Advanced or metastatic renal carcinoma represents a frequent disease in oncologic practice. Few years ago, in immunotherapy era, treatments had quickly reached deadlock. New therapies targeting vascular endothelial growth factors and their receptors (VEGF-R), sorafenib, sunitinib and bevacizumab, and the mammalian target of rapamycin (mTOR), temsirolimus and everolimus, have modified these patients prognosis and their quality of life in a few years. Nevertheless, patients included in randomized trials presented severe inclusion criteria. Then in the daily practice, patients have distinctive characteristics which were not evaluated in large pivotal studies: poor performance status, older patients, renal dysfunction, cerebral metastases or non clear cell renal cancer. In published trials, a few data concerning these situations are reported, and these studies have often included small samples, were retrospective or not randomised. However compared to global population, tolerance have not been very different in geriatric patients, or patients with poor performance status, or with central neurological metastases, or with papillary and chromophobe sub-types. On the contrary progression free or overall survivals increases are more difficult to confirm. Also before starting treatment, ratio between potential benefit and possible toxicities have to be evaluated. In patients with renal insufficiency, VEGF receptor inhibitors seem to be cautiously initiated at reduced doses, and to be increased according to tolerance. Due to these poor proof levels, clinical trials are needed for these specific populations.

[Targeted therapies and their indications in solid neoplasias]. / Les thérapies ciblées et leurs indications dans les tumeurs solides.

Targeted therapies are widely used in cancer because of their effectiveness, even in tumours that are resistant to conventional chemotherapy such as kidney or hepatocellular carcinomas. There are different families classified according to their mode of action. The antiangiogenics block tumor angiogenesis by acting on VEGF or its receptor. The main molecules are bevacizumab, sunitinib, and sorafinib. HER inhibitors work by blocking these receptors, which control different signaling intracellular pathways, and include an inhibitor of HER2, trastuzumab, and various inhibitors of HER1, or EGFR, including cetuximab, erlotinib, and gefitinib. Inhibitors of KIT, a membrane receptor, are mainly represented by imatinib, an inhibitor of tyrosine kinase. Finally, mTOR inhibitors act on the signaling pathway PI3K/AKT/mTOR, and key molecules are temsirolimus, everolimus, and deforolimus.

Grape seed extract inhibits angiogenesis via suppression of the vascular endothelial growth factor receptor signaling pathway.

Blockade of angiogenesis is an important approach for cancer treatment and prevention. Vascular endothelial growth factor (VEGF) is one of the most critical factors that induce angiogenesis and has thus become an attractive target for antiangiogenesis treatment. However, most current anti-VEGF agents often cause some side effects when given chronically. Identification of naturally occurring VEGF inhibitors derived from diet would be one alternative approach with an advantage of known safety. Grape seed extract (GSE), a widely used dietary supplement, is known to have antitumor activity. In this study, we have explored the activity of GSE on VEGF receptor and angiogenesis. We found that GSE could directly inhibit the kinase activity of purified VEGF receptor 2, a novel activity of GSE that has not been characterized. GSE could also inhibit the VEGF receptor/mitogen-activated protein kinase-mediated signaling pathway in endothelial cells. As a result, GSE could inhibit VEGF-induced endothelial cell proliferation and migration as well as sprout formation from aorta ring. In vivo assay further showed that GSE could inhibit tumor growth and tumor angiogenesis of MDA-MB-231 breast cancer cells in mice. Consistent with the in vitro data, GSE treatment of tumor-bearing mice led to concomitant reduction of blood vessel density and phosphorylation of mitogen-activated protein kinase. Depletion of polyphenol with polyvinylpyrrolidone abolished the antiangiogenic activity of GSE, suggesting a water-soluble fraction of polyphenol in GSE is responsible for the antiangiogenic activity. Taken together, this study indicates that GSE is a well-tolerated and inexpensive natural VEGF inhibitor and could potentially be useful in cancer prevention or treatment.

Inhibition of tyrosine phosphorylation of vascular endothelial growth factor receptors in human umbilical vein endothelial cells: a potent anti-angiogenic lipid-rich extract from shark.

We have previously reported that an ethanolic extract of dried shark muscle mixed with olive oil (shark muscle-olive oil [SMO]) has potent anti-angiogenic activity and that this extract appears to inhibit the binding of vascular endothelial growth factor (VEGF) to its receptor(s). In this study, we investigated the effects of SMO on the phosphorylation of VEGF receptor(s) in human umbilical vein endothelial cells (HUVECs). In vitro cell proliferation assays showed that SMO significantly reversed the VEGF-promoted increase in HUVEC proliferation. Western blot analysis revealed that SMO treatment markedly inhibited the VEGF-promoted tyrosine phosphorylation of VEGF receptor-2 (KDR) and VEGF receptor-1 (Flt-1) in a dose-dependent manner. These results demonstrated that SMO might interfere with or block the binding of VEGF with its receptors, and thereby inhibit the VEGF receptor(s) signal transduction pathway and so inhibit angiogenesis.

[Effect of angiogenesis inhibitors on renal cell carcinoma]. / Angiogenezisgátlók hatása metasztatikus vesesejtes rákban.

Sporadic renal cell carcinomas are characterized by EGFR (HER-1) and EGFR-2 (HER-2) expression, however, signal transduction inhibitors of this pathway were clinically ineffective. Clear cell renal cell cancer is hormone-, irradiation- and chemotherapy resistant with moderate sensitivity to immunotherapy. The only clinically effective class of agents in case of this tumor type was proved to be the angiosuppressive agents. In 2005 FDA approved sorafenib for the first line treatment while in 2006 sunitinib for second line treatment in the cytokine resistant medium-risk renal cell carcinoma. This was followed by the European approval of both agents for second line treatment of renal cell cancer. Sunitinib was approved for first line treatment of renal cell cancer in Europe based on a phase III trial comparing it to interferon. Temsirolimus obtained its approval for the treatment of high risk renal cell cancer patients in 2007. Last but not least, FDA approval is on the way in case of bevacizumab as well to treat renal cell cancer. Based on the data demonstrated on the ASCO'2007, various modalities have to be developed for various stages of progression of clear cell renal cell cancer.

Vascular endothelial growth factor receptor tyrosine kinase inhibitors in non-small cell lung cancer: a review of recent clinical trials.

Non-small cell lung cancer (NSCLC) remains the leading cause of cancer-related mortality in the United States. Therapeutic agents that target the underlying biology of this disease are necessary to improve outcomes. Angiogenesis plays a central role in NSCLC tumor growth and metastases. The vascular endothelial growth factor pathway (VEGF) as a therapeutic target was recently validated in NSCLC. Since then, a multitude of early phase clinical trials that incorporate the use of angiogenesis inhibitors, either as single agents or in combination with cytotoxic chemotherapy, have been conducted in advanced, refractory NSCLC. This article reviews these clinical trials with attention to toxicity, efficacy, and direction of further study. The data from these trials suggest that optimal use of anti-angiogenic agents in NSCLC is more likely in combination with standard cytotoxic agents, however the most effective combination with the least toxicity is yet to be determined.

Glycitein activates extracellular signal-regulated kinase via vascular endothelial growth factor receptor signaling in nontumorigenic (RWPE-1) prostate epithelial cells.

Increased consumption of soy is associated with a decreased risk for prostate cancer; however, the specific cellular mechanisms responsible for this anticancer activity are unknown. Dietary modulation of signaling cascades controlling cellular growth, proliferation and differentiation has emerged as a potential chemopreventive mechanism. The present study examined the effects of four soy isoflavones (genistein, daidzein, glycitein and equol) on extracellularsignal-regulated kinase (ERK1/2) activity in a nontumorigenic prostate epithelial cell line (RWPE-1). All four isoflavones (10 micromol/L) significantly increased ERK1/2 activity in RWPE-1 cells, as determined by immunoblotting. Isoflavone-induced ERK1/2 activation was rapid and sustained for approximately 2 h posttreatment. Glycitein, the most potent activator of ERK1/2, decreased RWPE-1 cell proliferation by 40% (P<.01). Glycitein-induced ERK1/2 activation was dependent, in part, on tyrosine kinase activity associated with vascular endothelial growth factor receptor (VEGFR). The presence of both VEGFR1 and VEGFR2 in the RWPE-1 cell line was confirmed by immunocytochemistry. Treatment of RWPE-1 cells with VEGF(165) resulted in transient ERK1/2 activation and increased cellular proliferation. The ability of isoflavones to modulate ERK1/2 signaling cascade via VEGFR signaling in the prostate may be responsible, in part, for the anticancer activity of soy.

Wogonin inhibits IL-6-induced angiogenesis via down-regulation of VEGF and VEGFR-1, not VEGFR-2.

So far, no antiangiogenic activity of wogonin, a flavonoid, on human umbilical vein endothelial cells (HUVECs) has been demonstrated. The aim of this study was to investigate the effects of wogonin on IL-6-induced angiogenesis in HUVEC cultures and chorioallantoic membrane (CAM) neovascularization. The in vivo CAM model was applied to evaluate the percentage of new vessel formations, followed by measurement of endothelial migration and tube formation in HUVEC cultures. The results revealed that wogonin (10(-8) approximately 10(-5)M) concentration-dependently inhibited IL-6-induced angiogenesis. The signaling pathway was through down-regulation of the autocrine loop of VEGF and VEGFR-1, but not of VEGFR-2. Furthermore, the regulating loop of the IL-6 receptor complex was also attenuated via expression of sIL-6Ralpha and gp130, but not of IL-6/IL-6R binding density. We conclude that wogonin is a suppressive agent of the autoregulated loop of VEGF, VEGFR-1 and the IL-6 receptor complex.

Inhibition of pro-angiogenic factors by a lipid-rich shark extract.

This study aimed to determine whether a shark muscle oil-olive oil mixture influences activators of human angiogenesis. The mixture completely abolished the stimulation induced by vascular endothelial growth factor (VEGF), fibroblast growth factor-2, transforming growth factor-beta, and platelet-derived growth factor. This suggests that it may compete with these growth factors for their binding sites on the endothelial cell surface either by binding to the growth factor or by blocking the actual receptor. The possibility of the oil binding to the VEGF receptor was studied through the use of soluble forms of the receptors (VEGF-R1 and VEGF-R2). It was found that the shark oil-olive oil inhibited the formation of the complexes of VEGF with both of the receptors. This could have been because the oil bound to either the VEGF or the receptor or both. To determine which is possible, the shark oil-olive oil was mixed with the receptors. The molecular size of the receptors increased, and these larger forms of the receptor had reduced capacity for complexing with VEGF. Therefore, one mode of potential anti-angiogenic action of the shark muscle oil-olive oil is the inhibition of the activity of a number of stimulatory molecules, including VEGF. This study demonstrates that the blend of shark and olive oils antagonizes VEGF activity by binding to at least two receptors for the factor, thereby inhibiting the activation by the growth factor.

Artesunate reduces chicken chorioallantoic membrane neovascularisation and exhibits antiangiogenic and apoptotic activity on human microvascular dermal endothelial cell.

Artesunate (ART), a semi-synthetic derivative of artemisinin extracted from the Chinese herb Artemisia annua, is a safe and effective antimalarial drug. ART has now been analyzed for its anti-angiogenic activity in vivo and in vitro. The anti-angiogenic effect in vivo was evaluated on chicken chorioallantoic membrane (CAM) neovascularisation model. ART started to significantly inhibit CAM angiogenesis at a low concentration of 10 nm/100 microl/egg, and completely inhibited the angiogenesis at 80 nm/100 microl/egg. The inhibitory effect of in vitro angiogenesis was tested on the models of proliferation and differentiation of human microvascular dermal endothelial cell line, an important representive of endothelial cells, as well as immunocytochemistry assay for two major VEGF receptors (Flt-1 and KDR/flk-1) expressions. The results showed that ART could remarkably inhibit proliferation and differentiation of endothelial cells in a dose-dependent form in a range of 12.5-100 microM. ART also could reduce Flt-1 and KDR/flk-1 expressions in a range of 0.1-0.5 microM. Furthermore, we examined the apoptosis of human microvascular dermal endothelial cell line induced by ART. The apoptosis was detected by morphological assay of ethidium bromide (EB)/acridine orange (AO) dual staining as well as DNA fragmentation assay of TUNEL labeling and quantified by flowcytometric PI assay. Our results suggest that the antiangiogenic effect induced by ART might occur by the induction of cellular apoptosis. These findings and the known low toxicity indicated ART might be a promising candidate for angiogenesis inhibitors.