Kegg Pathway: VEGF signaling pathway

Cancer Biol Ther. 2009 Dec 19; 8(23):
Tahir SA, Park S, Thompson TC

Caveolin-1 (cav-1) is a multifunctional protein and major component of caveolae membranes serving important functions related to signal transduction, endocytosis, transcytosis, and molecular transport. We previously showed that cav-1 is overexpressed and secreted by metastatic prostate cancer cells. We now report that cav-1 gene transduction (Adcav-1) or recombinant cav-1 (rcav-1) protein treatment of cav-1-negative prostate cancer cell line LP-LNCaP or cav-1(-/-) endothelial cells potentiated VEGF-stimulated angiogenic signaling. Downregulation of cav-1 in prostate cancer cell line PC-3 or human umbilical vein endothelial cells (HUVECs) through cav-1 siRNA significantly reduced basal and VEGF-stimulated phosphorylation of VEGFR2 (Y951), PLCgamma1 (Y783) and/or Akt (S473 & T308) relative to those in control siRNA treated cells. Additionally rcav-1 stimulation of cav-1 siRNA treated HUVECs restored this signaling pathway. Confocal microscopy and immunoprecipitation analysis revealed association and colocalization of VEGFR2 and PLCgamma1 with cav-1 following VEGF stimulation in HUVECs. Interestingly, treatment of HUVECs with cav-1 scaffolding domain (CSD) caused significant reduction in the VEGF-stimulated phosphorylation of VEGFR2, PLCgamma1 and Akt suggesting that CSD inhibits cav-1-mediated angiogenic signaling. VEGF stimulation of HUVECs significantly increased tubule length and cell migration, but this stimulatory effect was significantly reduced by cav-1 siRNA and/or CSD treatment. The present study demonstrates that cav-1 regulates VEGF-stimulated VEGFR2 autophosphorylation and activation of downstream angiogenic signaling, possibly through compartmentalization of specific signaling molecules. Our results provide mechanistic insight into the role of cav-1 in prostate cancer and suggest the use of CSD as a therapeutic tool to suppress angiogenic signaling in prostate cancer.

Clin Transplant. 2009 Nov 16;
Ho CM, Huang SF, Hu RH, Ho MC, Wu YM, Lee PH

Sirolimus is one treatment option in transplant recipients with Kaposi's sarcoma (KS), which involves dysregulation of Akt-mammalian target of rapamycin (mTOR) signaling pathway. Signal modifications after sirolimus therapy in organ recipients with KS are largely unknown and not verified. We reported a case of KS found two yr after liver transplantation in which the immunosuppression was changed from tacrolimus, MMF, and steroid to sirolimus alone. In skin, which was found to have persistent KS after a two-month treatment of sirolimus and was removed completely one yr later, KS was no longer present. The patient went well without graft rejection. Tumor biopsies were performed before, two months, and one yr after the start of sirolimus. Immunohistochemical staining of vascular endothelial growth factor (VEGF), p-Akt, p-mTOR, p-p70 S6 kinase, and Western blot for p-tuberin/ tuberous sclerosis complex (TSC)2 was performed. VEGF was suppressed thoroughly in two-month use of sirolimus. In addition, p-Akt and p-mTOR, which were decreased at two months, could not be detected after one yr of treatment. Moreover, p-p70 S6 kinase, expressed strongly in overlying epidermis initially, was suppressed completely after two months of treatment. However, p-tuberin/TSC2, contrary to suggested theoretically, was not detected through all specimens, implying not to be a significant event. Suppressed expression of VEGF, p-Akt, and p-mTOR was the major event of signaling modification through the long-term use of sirolimus.

FEBS Lett. 2009 Nov 12;
Jang GH, Park IS, Yang JH, Bischoff J, Lee YM

We have reported that VEGF-A induces the proliferation of human pulmonary valve endothelial cells (HPVECs) through NFATc1 activation (1). Here we show that VEGF-A increases the migration of HPVECs through NFATc1 activation, suggesting that VEGF-A/NFATc1 regulates the migration of HPVECs. To learn how this pathway may be involved in post-natal valvular repair, HPVECs were treated with VEGF-A, with or without cyclosporine A to selectively block VEGF-NFATc1 signaling. DSCR1 and HB-EGF are two genes identified by DNA microarray as being up-regulated by VEGF-A in a cyclosporine-A-sensitive manner. DSCR1 silencing increased the migration of ovine valve endothelial cells, whereas HB-EGF silencing inhibited migration. This differential effect suggests that VEGF-A/NFATc1 signaling might be a crucial coordinator of endothelial cell migration in post-natal valves.

Biochem Soc Trans. 2009 Dec; 37(Pt 6): 1167-70
Waltenberger J

The action of VEGF (vascular endothelial growth factor) is essential to maintain proper endothelial and vascular function. VEGF stimulates virtually all aspects of endothelial function, namely proliferation, migration, permeability and nitric oxide production and release. In addition, the action of VEGF makes the endothelium anti-apoptotic. In turn, the inhibition of VEGF action is associated with endothelial dysfunction. Likewise, endothelial dysfunction can be found in the presence of several cardiovascular risk factors, including diabetes mellitus, hypercholesterolaemia and smoking. As circulating monocytes express functionally active VEGFR-1 (VEGF receptor 1) on their surface, monocytes and the related VEGFR-1-mediated signal transduction cascades have come into focus. The function of monocytes is negatively affected by diabetes mellitus, resulting in monocyte dysfunction. More specifically, a VEGF-related signal transduction defect can be detected in monocytes isolated from diabetic individuals. This reduced monocyte response to VEGF, demonstrated by a reduced chemotactic response, can be regarded as VEGF resistance. It is based on the pre-activation of certain intracellular pathways secondary to the diabetes mellitus-related RAGE (receptor for advanced glycation end-products) activation, ROS (reactive oxygen species) activation and inhibition of PTPs (protein tyrosine phosphatases). This unspecific pre-activation of intracellular pathways represents the molecular basis of VEGF resistance in diabetes mellitus.

Biochem Soc Trans. 2009 Dec; 37(Pt 6): 1161-6
Shibuya M

Both VEGF (vascular endothelial growth factor)-A and Orf-virus-encoded VEGF-E bind and activate VEGFR (VEGF receptor)-2; however, only VEGF-A binds VEGFR-1. To understand the biological differences between VEGF-A and VEGF-E in vivo, we established transgenic mouse models. K14 (keratin-14)-promoter-driven VEGF-E transgenic mice showed a significant increase in mature blood vessels. However, K14-VEGF-A transgenic mice exhibited severe inflammation and oedema with increased angiogenesis, as well as lymphangiogenesis and lymph vessel dilatation. K14-VEGF-A transgenic mice deficient in VEGFR-1 signalling (K14-VEGF-A-tg/VEGFR-1 TK(-/-) mice) showed decreases in oedema and inflammation with less recruitment of macrophage-lineage cells, suggesting an involvement of VEGFR-1 in these adverse effects. VEGFE might be more useful than VEGFA for pro-angiogenic therapy.

Clin Cancer Res. 2009 Nov 15; 15(22): 6921-30
Damiano V, Garofalo S, Rosa R, Bianco R, Caputo R, Gelardi T, Merola G, Racioppi L, Garbi C, Kandimalla ER, Agrawal S, Tortora G

PURPOSE: Resistance to anti-HER2 monoclonal antibody trastuzumab is a relevant issue in breast cancer patients. Among the mechanisms implicated in trastuzumab resistance, increasing evidence supports a role of tumor microenvironment. We previously found that a novel toll-like receptor 9 agonist, referred to as immune modulatory oligonucleotide (IMO) and currently under clinical investigation, acts through epidermal growth factor receptor (EGFR) and shows direct antiangiogenic effects by cooperating with anti-EGFR or anti-VEGF drugs, thus interfering with cancer cells and microenvironment. EXPERIMENTAL DESIGN: In this study, we used KPL-4 and JIMT-1 trastuzumab-resistant breast cancer cells to evaluate the combination IMO plus trastuzumab as a therapeutic option for trastuzumab-resistant breast cancers. RESULTS: IMO inhibits KPL-4 and JIMT-1 xenografts growth and potentiates trastuzumab antitumor effect, with complete suppression of tumor growth, potent enhancement of trastuzumab-mediated antibody-dependent cell-mediated cytotoxicity, and strong inhibition of EGFR/HER2-related signaling. In KPL-4 xenografts, IMO alone interferes with HER signal transduction, whereas trastuzumab is ineffective. IMO induces an HER-dependent signal inhibition also in vitro by modulating a functional interaction between toll-like receptor 9 and HER receptors occurring at membrane level. Finally, IMO plus trastuzumab produces a cooperative antiangiogenic effect related to suppression of endothelial HER-related signaling. CONCLUSIONS: We showed a cooperative effect of IMO plus trastuzumab in trastuzumab-resistant breast cancers due to IMO direct antitumor and antiangiogenic activity and antibody-dependent cell-mediated cytotoxicity enhancement. Moreover, we provided first evidence of a toll-like receptor 9/HER interaction at membrane level as novel mechanism of action. Altogether, we propose IMO plus trastuzumab as an effective strategy in trastuzumab-resistant breast cancers.

Target Oncol. 2009 Nov 7;
Capdevila J, Salazar R

Gastroenteropancreatic neuroendocrine tumors (GEPNETs) are rare neoplasms that require a multidisciplinary approach for an optimal management. The traditional cytotoxic agents are of limited efficacy in the treatment of these tumors. A better understanding of the molecular pathways that characterize tumor growth has provided novel targets in cancer treatment. Several proteins have been implicated as having a crucial role in GEPNETs. Several proangiogenic molecules are overexpressed in GEPNETs including vascular endothelial growth factor (VEGF) and its receptors, and related signaling pathway components such as epidermal growth factor receptor (EGFR), insulin growth factor-I receptor (IGF-IR) and PI3K-AKT-mTOR pathway. In this article we aim to review the recent development of the main molecules that target these proteins and have showed promising activity in the treatment of GEPNETs.

Methods Enzymol. 2009; 467: 461-97
Wu FT, Stefanini MO, Mac Gabhann F, Popel AS

Most physiological processes are subjected to molecular regulation by growth factors, which are secreted proteins that activate chemical signal transduction pathways through binding of specific cell-surface receptors. One particular growth factor system involved in the in vivo regulation of blood vessel growth is called the vascular endothelial growth factor (VEGF) system. Computational and numerical techniques are well suited to handle the molecular complexity (the number of binding partners involved, including ligands, receptors, and inert binding sites) and multiscale nature (intratissue vs. intertissue transport and local vs. systemic effects within an organism) involved in modeling growth factor system interactions and effects. This chapter introduces a variety of in silico models that seek to recapitulate different aspects of VEGF system biology at various spatial and temporal scales: molecular-level kinetic models focus on VEGF ligand-receptor interactions at and near the endothelial cell surface; mesoscale single-tissue 3D models can simulate the effects of multicellular tissue architecture on the spatial variation in VEGF ligand production and receptor activation; compartmental modeling allows efficient prediction of average interstitial VEGF concentrations and cell-surface VEGF signaling intensities across multiple large tissue volumes, permitting the investigation of whole-body intertissue transport (e.g., vascular permeability and lymphatic drainage). The given examples will demonstrate the utility of computational models in aiding both basic science and clinical research on VEGF systems biology.

Curr Eye Res. 2009 Oct; 34(10): 867-76
Weng CY, Kothary PC, Verkade AJ, Reed DM, Del Monte MA

PURPOSE: To investigate the mitogenic activity of insulin-like growth factor-1 (IGF-1) on the proliferation of human retinal pigment epithelial cells (hRPE) and to elucidate the role of vascular endothelial growth factor (VEGF) and MAP kinase (MAPK) in the IGF-1 signaling cascade. METHODS: Human RPE specimens were obtained from postmortem non-pathological eyes and cultured in vitro through several passages. Cellular proliferation in the presence of increasing concentrations of IGF-1 and IGF-1 + PD98059 (a known MAPK inhibitor) was measured by [(3)H]thymidine incorporation; trypan blue exclusion studies (T) verified cell viability. Under the same experimental conditions, synthesis of VEGF was measured utilizing [(14)C]methionine immunoprecipitation and immunocytochemical methods as well as Western blot analysis. RESULTS: IGF-1 stimulated hRPE proliferation, as demonstrated by [(3)H]thymidine incorporation. There was also an IGF-1-induced increase in VEGF synthesis as measured quantitatively by [(14)C]methionine-VEGF immunoprecipitation. This was qualitatively confirmed by immunocytochemistry and Western blotting. PD98059 suppressed both IGF-1-induced cell proliferation as well as IGF-1-stimulated VEGF production. CONCLUSIONS: These studies suggest that IGF-1 is a mitogen for hRPE cells and also stimulates production of the angiogenic factor, VEGF. Additionally, PD98059 inhibits the production of VEGF, suggesting that the MAP kinase pathway is involved in IGF-1-mediated angiogenesis.

Circ Res. 2009 Nov 5;
van Rooij E, Fielitz J, Sutherland LB, Thijssen VL, Crijns HJ, Dimaio MJ, Shelton J, De Windt LJ, Hill JA, Olson EN

Rationale: Gender differences in cardiovascular disease have long been recognized and attributed to beneficial cardiovascular actions of estrogen. Class II histone deacetylases (HDACs) act as key modulators of heart disease by repressing the activity of the myocyte enhancer factor (MEF)2 transcription factor, which promotes pathological cardiac remodeling in response to stress. Although it is proposed that HDACs additionally influence nuclear receptor signaling, the effect of class II HDACs on gender differences in cardiovascular disease remains unstudied. Objective: We aimed to examine the effect of class II HDACs on post-myocardial infarction remodeling in male and female mice. Methods and Results: Here we show that the absence of HDAC5 or -9 in female mice protects against maladaptive remodeling following myocardial infarction, which coincides with upregulation of estrogen-responsive genes in the heart. This genetic reprogramming coincides with a pronounced increase in expression of the estrogen receptor (ER)alpha gene, which we show to be a direct MEF2 target gene. ERalpha also directly interacts with class II HDACs. Cardioprotection resulting from the absence of HDAC5 or -9 in female mice can be attributed, at least in part, to enhanced neoangiogenesis in the infarcted region via upregulation of the ER target gene vascular endothelial growth factor-a. Conclusions: Our results reveal a novel gender-specific pathway of cardioprotection mediated by ERalpha and its regulation by MEF2 and class II HDACs.

Cell Mol Immunol. 2009 Oct; 6(5): 327-34
Wang S, Liu Z, Wang L, Zhang X

There is growing evidence for a connection between inflammation and tumor development, and the nuclear factor kappa B (NF-kappaB), a proinflammatory transcription factor, is hypothesized to promote tumorigenesis. Although the genetic evidence for the hypothesis has been lacking, recent papers have lent credence to this hypothesis. It has been reported that constitutive NF-kappaB activation in inflammatory bowel diseases (IBDs) increases risk of colorectal cancer (CRC) in the patients with the number of years of active disease. NF-kappaB activation might induce cellular transformation, mediate cellular proliferation, prevent the elimination of pre-neoplastic and fully malignant cells by up-regulating the anti-apoptosis proteins. Furthermore, NF-kappaB may contribute to the progression of CRC by regulating the expression of diverse target genes that are involved in cell proliferation (Cyclin D1), angiogenesis (VEGF, IL-8, COX2), and metastasis (MMP9). These findings implicate NF-kappaB inhibition as an important therapeutic target in CRC. However, due to lack of knowledge about the specific roles of different NF-kappaB subunits in different stage of carcinogenesis, and compounds to block specific subunits of NF-kappaB family, it will be a long time before the coming of targeting NF-kappaB in CRC therapy.

Tissue Eng Part A. 2009 Nov 3;
Dohle E, Fuchs S, Kolbe M, Hofmann A, Schmidt H, Kirkpatrick J

A number of previous studies documented the angiogenic potential of outgrowth endothelial cells (OEC) in vitro and in vivo and provided evidence that therapeutic success could depend on co-culture or co-implantation strategies. Thus, deeper insight into the molecular mechanisms underlying this pro-angiogenic effect of co-cultures might provide new translational options for tissue engineering and regenerative medicine. One promising signaling pathway in bone repair involved in neoangiogenesis and bone formation, is the sonic hedgehog (Shh) pathway. In this paper we focus on the effect of Shh on the formation of microvessel-like structures and osteoblastic differentiation in co-cultures of primary osteoblasts (pOB) and OEC. Already after 24 hours of treatment, Shh leads to a massive increase in microvessel-like structures compared to untreated co-cultures. Increased formation of angiogenic structures seems to correlate with the upregulation of vascular endothelial growth factor (VEGF) or angiopoietins (Ang-1, Ang-2) studied at both the mRNA and protein-level. In addition, treatment with cyclopamine, an inhibitor of hedgehog signaling, blocked the formation of microvessel-like structures in the co-cultures. However, exogenous Shh also resulted in the upregulation of several osteogenic differentiation markers in real time PCR, as well as in an increased mineralization and alkaline phosphatase (ALP) activity. The present data highlight the central role of the Shh pathway in bone regeneration and vascularization. Furthermore sonic hedgehog might have the potential to improve both angiogenesis and osteogenesis in clinical applications in the future.

Traffic. 2009 Oct 7;
Bruns AF, Herbert SP, Odell AF, Jopling HM, Hooper NM, Zachary IC, Walker JH, Ponnambalam S

Abstract Vascular endothelial growth factor A (VEGF-A)-induced signaling through VEGF receptor 2 (VEGFR2) regulates both physiological and pathological angiogenesis in mammals. However, the temporal and spatial mechanism underlying VEGFR2-mediated intracellular signaling is not clear. Here, we define a pathway for VEGFR2 trafficking and proteolysis that regulates VEGF-A-stimulated signaling and endothelial cell migration. Ligand-stimulated VEGFR2 activation and ubiquitination preceded proteolysis and cytoplasmic domain removal associated with endosomes. A soluble VEGFR2 cytoplasmic domain fragment displayed tyrosine phosphorylation and activation of downstream intracellular signaling. Perturbation of endocytosis by the depletion of either clathrin heavy chain or an ESCRT-0 subunit caused differential effects on ligand-stimulated VEGFR2 proteolysis and signaling. This novel VEGFR2 proteolysis was blocked by the inhibitors of 26S proteasome activity. Inhibition of proteasome activity prolonged VEGF-A-induced intracellular signaling to c-Akt and endothelial nitric oxide synthase (eNOS). VEGF-A-stimulated endothelial cell migration was dependent on VEGFR2 and VEGFR tyrosine kinase activity. Inhibition of proteasome activity in this assay stimulated VEGF-A-mediated endothelial cell migration. VEGFR2 endocytosis, ubiquitination and proteolysis could also be stimulated by a protein kinase C-dependent pathway. Thus, removal of the VEGFR2 carboxyl terminus linked to phosphorylation, ubiquitination and trafficking is necessary for VEGF-stimulated endothelial signaling and cell migration.

Vascul Pharmacol. 2009 Oct 30;
Luidens MK, Mousa SA, Davis FB, Lin HY, Davis PJ

In models of thyroid hormone-induced cardiac hypertrophy, there is appropriate, supportive angiogenesis. Twenty years ago in one such model, angiogenesis in response to the hormone was observed before hypertrophy developed and it is now understood that iodothyronines induce neovascularization in a variety of settings, including the heart, ischemic striated muscle and tumor beds. The molecular mechanism of the proangiogenic action of thyroid hormone is both nongenomic and genomic. It is initiated nongenomically at the cell surface receptor for the hormone on integrin alphavbeta3. Kinase transduction of the hormone signal and, ultimately, transcription of several anagiogenesis-relevant genes result. The genes include basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF). In addition, the integrin receptor for thyroid hormone (l-thyroxine, T(4), and 3, 5, 3'-triiodo-l-thyronine, T(3)) engages in crosstalk with the VEGF and bFGF receptors. Occlusion with tetraiodothyroacetic acid (tetrac) of the hormone receptor on the integrin in the absence of T(4) and T(3) suppresses the angiogenic effects of VEGF and bFGF. Tetrac also blocks the proangiogenic actions of T(4) and T(3). Other thyroid hormone analogues that are angiogenic include diiodothyropropionic acid (DITPA) and the nuclear thyroid hormone receptor-beta-selective agonist, GC-1. Thyroid hormone sustains angiogenesis and coronary blood flow about infarcted heart tissue in experimental models and blocks deleterious heart remodeling that otherwise is predictable in such tissue. The hormone may also induce expression of the hypoxia-inducible factor 1alpha (HIF1alpha) gene, a transcription factor important to coronary artery collateralization in the setting of hypoxia. The hormone also causes transcription of the matrix Gla protein (MGP) gene that opposes vascular smooth muscle calcification.

J Nanobiotechnology. 2009; 7: 8
Sheikpranbabu S, Kalishwaralal K, Venkataraman D, Eom SH, Park J, Gurunathan S

ABSTRACT: The aim of this study is to determine the effects of silver nanoparticles (Ag-NP) on vascular endothelial growth factor (VEGF)-and interleukin-1 beta (IL-1beta)-induced vascular permeability, and to detect the underlying signaling mechanisms involved in endothelial cells. Porcine retinal endothelial cells (PRECs) were exposed to VEGF, IL-1beta and Ag-NP at different combinations and endothelial cell permeability was analyzed by measuring the flux of RITC-dextran across the PRECs monolayer. We found that VEGF and IL-1beta increase flux of dextran across a PRECs monolayer, and Ag-NP block solute flux induced by both VEGF and IL-1beta. To explore the signalling pathway involved VEGF- and IL-1beta-induced endothelial alteration, PRECs were treated with Src inhibitor PP2 prior to VEGF and IL-1beta treatment, and the effects were recorded. Further, to clarify the possible involvement of the Src pathways in endothelial cell permeability, plasmid encoding dominant negative(DN) and constitutively active(CA) form of Src kinases were transfected into PRECs, 24 h prior to VEGF and IL-1beta exposure and the effects were recorded. Overexpression of DN Src blocked both VEGF-and IL-1beta-induced permeability, while overexpression of CA Src rescues the inhibitory action of Ag-NP in the presence or absence of VEGF and IL-1beta. Further, an in vitro kinase assay was performed to identify the presence of the Src phosphorylation at Y419. We report that VEGF and IL-1beta-stimulate endothelial permeability via Src dependent pathway by increasing the Src phosphorylation and Ag-NP block the VEGF-and IL-1beta-induced Src phosphorylation at Y419. These results demonstrate that Ag-NP may inhibit the VEGF-and IL-1beta-induced permeability through inactivation of Src kinase pathway and this pathway may represent a potential therapeutic target to inhibit the ocular diseases such as diabetic retinopathy.

Invest Ophthalmol Vis Sci. 2009 Oct 29;
Zhou T, Hu Y, Chen Y, Zhou K, Zhang B, Gao G, Ma JX

PURPOSE. Our previous studies showed that the Wnt signaling pathway is activated in the retina and retinal pigment epithelium of animal models of age-related macular degeneration (AMD) and diabetic retinopathy (DR). The purpose of this study is to investigate the role of the canonical Wnt pathway in pathogenesis of these diseases. METHODS. The Wnt pathway was activated using the Wnt3a conditioned medium and adenovirus expressing a constitutively active mutant of beta-catenin (Ad-S37A) in ARPE19, a cell line derived from human RPE. Ad-S37A was injected into the vitreous of normal rats to activate the Wnt pathway in the retina. Accumulation of beta-catenin was determined by Western blot analysis, and its nuclear translocation revealed by immunocytochemistry. Inflammatory factors were quantified by Western blot analysis and ELISA. Oxidative stress was determined by measuring intracellular reactive oxygen species (ROS) generation, and nitrotyrosine levels. RESULTS. The Wnt3a conditioned medium and Ad-S37A both increased beta-catenin levels and its nuclear translocation in ARPE19 cells, suggesting activation of the canonical Wnt pathway. The activation of the Wnt pathway significantly up-regulated expression of VEGF, NF-kappaB and TNF-alpha. Further, Ad-S37A induced ROS generation in a dose-dependent manner. Wnt3a also induced a 2-fold increase of ROS generation. Intravitreal injection of Ad-S37A up-regulated expression of VEGF, ICAM-1, NF-kappaB, TNF-alpha and increased protein nitrotyrosine levels in the retina of normal rats. CONCLUSION. Activation of the canonical Wnt pathway is sufficient to induce retinal inflammation and oxidative stress and plays a pathogenic role in AMD and DR.

Cancer Sci. 2009 Sep 18;
Boere IA, Hamberg P, Sleijfer S

Through advances in molecular biology, insight into the mechanisms driving malignancies has improved immensely and as a result, various factors playing an essential role in the biology of numerous tumor types have been revealed. By using compounds that specifically block the function of a single factor being crucial for tumor pathogenesis, it was hoped to exert antitumor activity while avoiding toxicities characteristic for conventional chemotherapy. One of the processes of crucial importance in the development of cancer, and consequently an attractive target, is angiogenesis. In recent years, several key factors for angiogenesis have been identified, including ligands, receptors, and transduction signaling factors. Of these, the vascular endothelial growth factor (VEGF) pathway has been found to be activated in numerous tumor types and considered one of the main drivers of angiogenesis. Roughly, VEGF-mediated angiogenesis can be inhibited by two approaches: either by monoclonal antibodies directed towards VEGF or its corresponding receptors, or by kinase inhibitors targeting the signal transduction of the VEGF receptors. As monotherapy, several kinase inhibitors exert antitumor activity in tumor types such as renal cell carcinoma. However, in most tumor types, the antitumor activity of compounds targeting the VEGF pathway is limited. In recent years, evidence is mounting that the paradigm of one single factor that drives malignant behavior applies rarely and is an oversimplification for most tumors in which there are multiple driving pathways. Consequently, multitargeting rather than single-targeting approaches are required. One of the means is by combining targeted agents with conventional cytotoxics. As the VEGF pathway also affects the sensitivity of tumor cells to chemotherapeutics, combinations of compounds targeting this pathway and conventional cytotoxics have been explored. This review addresses such combinations. (Cancer Sci 2009; 00: 000-000).

Rheumatol Int. 2009 Oct 27;
He Y, Fan J, Lin H, Yang X, Ye Y, Liang L, Zhan Z, Dong X, Sun L, Xu H

Increasing evidence indicates that the anti-malarial agent artemisinin and its derivatives may exert anti-angiogenic effect. In the present study, we explored the effect of artesunate, a artemisinin derivative, on TNFalpha- and hypoxia-induced expression of hypoxia inducible factor-1alpha (HIF-1alpha) and secretion of vascular endothelial growth factor (VEGF) and inteleukin-8 (IL-8) in human rheumatoid arthritis fibroblast-like synoviocytes (RA FLS), and further investigated the signal mechanism by which this compound modulates HIF-1alpha, VEGF and IL-8 expression. RA FLS obtained from patients with active rheumatoid arthritis were pretreated with artesunate, and then stimulated with TNFalpha and hypoxia. Production of VEGF and IL-8 was measured by ELISA. Nuclear location of HIF-1alpha was measured by confocal fluorescence microscopy. HIF-1alpha and other signal transduction proteins expression was measured by Western blot. Artesunate decreased the secretion of VEGF and IL-8 from TNFalpha- or hypoxia-stimulated RA FLS in a dose-dependent manner. Artesunate also inhibited TNFalpha- or hypoxia-induced nuclear expression and translocation of HIF-1alpha. We also showed that artesunate prevented Akt phosphorylation, but did not find evidence that phosphorylation of p38 and ERK was affected. TNFalpha- or hypoxia-induced secretion of VEGF and IL-8 and expression of HIF-1alpha were hampered by treatment with the PI3 kinase inhibitor LY294002, suggesting that inhibition of PI3 kinase/Akt activation might inhibit VEGF and IL-8 secretion and HIF-1alpha expression induced by TNFalpha or hypoxia. Our results suggest that artesunate inhibits angiogenic factor expression in RA FLS, and provide novel evidence that, as a low-cost agent, artesunate may have therapeutic potential for RA.

Nat Cell Biol. 2009 Nov; 11(11): 1325-31
Jones CA, Nishiya N, London NR, Zhu W, Sorensen LK, Chan AC, Lim CJ, Chen H, Zhang Q, Schultz PG, Hayallah AM, Thomas KR, Famulok M, Zhang K, Ginsberg MH, Li DY

Slit-Roundabout (Robo) signalling has a well-understood role in axon guidance. Unlike in the nervous system, however, Slit-dependent activation of an endothelial-specific Robo, Robo4, does not initiate a guidance program. Instead, Robo4 maintains the barrier function of the mature vascular network by inhibiting neovascular tuft formation and endothelial hyperpermeability induced by pro-angiogenic factors. In this study, we used cell biological and biochemical techniques to elucidate the molecular mechanism underlying the maintenance of vascular stability by Robo4. Here, we demonstrate that Robo4 mediates Slit2-dependent suppression of cellular protrusive activity through direct interaction with the intracellular adaptor protein paxillin and its paralogue, Hic-5. Formation of a Robo4-paxillin complex at the cell surface blocks activation of the small GTPase Arf6 and, consequently, Rac by recruitment of Arf-GAPs (ADP-ribosylation factor- directed GTPase-activating proteins) such as GIT1. Consistent with these in vitro studies, inhibition of Arf6 activity in vivo phenocopies Robo4 activation by reducing pathologic angiogenesis in choroidal and retinal vascular disease and VEGF-165 (vascular endothelial growth factor-165)-induced retinal hyperpermeability. These data reveal that a Slit2-Robo4-paxillin-GIT1 network inhibits the cellular protrusive activity underlying neovascularization and vascular leak, and identify a new therapeutic target for ameliorating diseases involving the vascular system.

Rheumatology (Oxford). 2009 Oct 23;
Dayer JM, Choy E

RA is a chronic, debilitating disease in which articular inflammation and joint destruction are accompanied by systemic manifestations including anaemia, fatigue and osteoporosis. IL-6 is expressed abundantly in the SF of RA patients and is thought to mediate many of the local and systemic effects of this disease. Unlike a number of other cytokines, IL-6 can activate cells through both membrane-bound (IL-6R) and soluble receptors (sIL-6R), thus widening the number of cell types responsive to this cytokine. Indeed, trans-signalling, where IL-6 binds to the sIL-6R, homodimerizes with glycoprotein 130 subunits and induces signal transduction, has been found to play a key role in acute and chronic inflammation. Elevated levels of IL-6 and sIL-6R in the SF of RA patients can increase the risk of joint destruction and, at the joint level, IL-6/sIL-6R can stimulate pannus development through increased VEGF expression and increase bone resorption as a result of osteoclastogenesis. Systemic effects of IL-6, albeit through conventional or trans-signalling, include regulation of acute-phase protein synthesis, as well as hepcidin production and stimulation of the hypothalamo-pituitary-adrenal axis, the latter two actions potentially leading to anaemia and fatigue, respectively. This review aims to provide an insight into the biological effects of IL-6 in RA, examining how IL-6 can induce the articular and systemic effects of this disease.