Exogenous norepinephrine attenuates the efficacy of sunitinib in a mouse cancer model.

BACKGROUND: Sunitinib alone exhibits satisfactory efficacy in several mouse homografts and xenografts but unsatisfactory efficacy in many kinds of solid tumors in clinic. Different from animals, receiving a diagnosis of cancer impacts chronic stress on patients. Here, we examine whether norepinephrine (NE), one of the most potent stress related hormones, leads to the difference in the efficacy of sunitinib between clinical and preclinical trials. METHODS: The influence of NE on mouse melanoma B16F1 cells under sunitinib was evaluated in vitro and in vivo. The ß-AR/cAMP/PKA (ß-adrenoceptor/cyclic adenosine monophosphate/protein kinase A) signaling pathway was also evaluated in human lung adenocarcinoma cells. RESULTS: We found that NE upregulated the expression of VEGF, IL-8 and IL-6 in vitro and stimulated tumor growth in vivo, which was mediated by ß-AR/cAMP/PKA signaling pathway and could be inhibited by propranolol, a ß-blocker for hypertension for decades. CONCLUSIONS: This research indicates exogenous norepinephrine attenuates the efficacy of sunitinib, and a combination of sunitinib and propranolol might be suggested as a new strategy in solid tumor in clinic.

Analyses of potential predictive markers and survival data for a response to sunitinib in patients with metastatic renal cell carcinoma.

BACKGROUND: Patients with metastatic clear cell renal cell carcinoma (ccRCC) are frequently treated with tyrosine kinase inhibitors (TKI) such as sunitinib. It inhibits angiogenic pathways by mainly targeting the receptors of VEGF and PDGF. In ccRCC, angiogenesis is characterized by the inactivation of the von Hippel-Lindau gene (VHL) which in turn leads to the induction of HIF1α target genes such as CA9 and VEGF. Furthermore, the angiogenic phenotype of ccRCC is also reflected by endothelial markers (CD31, CD34) or other tumor-promoting factors like Ki67 or survivin. METHODS: Tissue microarrays from primary tumor specimens of 42 patients with metastatic ccRCC under sunitinib therapy were immunohistochemically stained for selected markers related to angiogenesis. The prognostic and predictive potential of theses markers was assessed on the basis of the objective response rate which was evaluated according to the RECIST criteria after 3, 6, 9 months and after last report (12-54 months) of sunitinib treatment. Additionally, VHL copy number and mutation analyses were performed on DNA from cryo-preserved tumor tissues of 20 ccRCC patients. RESULTS: Immunostaining of HIF-1α, CA9, Ki67, CD31, pVEGFR1, VEGFR1 and -2, pPDGFRα and -ß was significantly associated with the sunitinib response after 6 and 9 months as well as last report under therapy. Furthermore, HIF-1α, CA9, CD34, VEGFR1 and -3 and PDGRFα showed significant associations with progression-free survival (PFS) and overall survival (OS). In multivariate Cox proportional hazards regression analyses high CA9 membrane staining and a response after 9 months were independent prognostic factors for longer OS. Frequently observed copy number loss and mutation of VHL gene lead to altered expression of VHL, HIF-1α, CA9, and VEGF. CONCLUSIONS: Immunoexpression of HIF-1α, CA9, Ki67, CD31, pVEGFR1, VEGFR1 and -2, pPDGFRα and -ß in the primary tumors of metastatic ccRCC patients might support the prediction of a good response to sunitinib treatment.

Serum eyedrops antagonize the anti(lymph)angiogenic effects of bevacizumab in vitro and in vivo.

PURPOSE: The effect of autologous serum eyedrops on the corneal vasculature is undefined. Therefore, we analyzed the corneal vascular effects of serum eyedrops in comparison with and in combination with bevacizumab eyedrops. METHODS: In vitro, blood and lymphatic endothelial cells were treated with serum eyedrops, bevacizumab eyedrops, or a combination of both, and cell proliferation was measured. In vivo, inflammatory corneal neovascularization was induced by suture placement. Subsequently, corneal blood and lymphatic vessel progression and regression were analyzed after treatment with serum or bevacizumab eyedrops or a combination of both. Hemangiogenesis and lymphangiogenesis were quantified in whole mounts using CD31 and lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1); inflammatory cell infiltration was analyzed using CD11b. Furthermore, corneal expression levels of interleukin 1ß, tumor necrosis factor α, vascular endothelial growth factor (VEGF) A, VEGF-C, and VEGF-D were analyzed by real-time PCR. RESULTS: In vitro, serum increased and bevacizumab decreased endothelial cell proliferation. In vivo, serum eyedrops had no significant effect on corneal vessel progression or regression. Bevacizumab eyedrops reduced blood and lymphatic vessel progression and promoted blood and lymphatic vessel regression. The combination of serum eyedrops and bevacizumab eyedrops attenuated the anti(lymph)angiogenic effects of bevacizumab. Inflammatory corneal cell counts were not significantly altered by serum or bevacizumab eyedrops. Serum eyedrops changed the proinflammatory and pro(lymph)angiogenic status of the cornea. Bevacizumab eyedrops significantly reduced proinflammatory and pro(lymph)angiogenic factor expression. Higher doses of bevacizumab did not restore its anti(lymph)angiogenic effects when used in combination with serum. CONCLUSIONS: The counteracting effects of serum eyedrops and bevacizumab eyedrops on the corneal vasculature should be taken into account when combined therapeutic regimens are considered.

PG545, an angiogenesis and heparanase inhibitor, reduces primary tumor growth and metastasis in experimental pancreatic cancer.

Aggressive tumor progression, metastasis, and resistance to conventional therapies lead to an extremely poor prognosis for pancreatic ductal adenocarcinoma (PDAC). Heparanase, an enzyme expressed by multiple cell types, including tumor cells in the tumor microenvironment, has been implicated in angiogenesis and metastasis, and its expression correlates with decreased overall survival in PDAC. We evaluated the therapeutic potential of PG545, an angiogenesis and heparanase inhibitor, in experimental PDAC. PG545 inhibited the proliferation, migration, and colony formation of pancreatic cancer cells in vitro at pharmacologically relevant concentrations. Heparanase inhibition also reduced the proliferation of fibroblasts but had only modest effects on endothelial cells in vitro. Furthermore, PG545 significantly prolonged animal survival in intraperitoneal and genetic models (mPDAC: LSL-Kras(G12D); Cdkn2a(lox/lox); p48(Cre)) of PDAC. PG545 also inhibited primary tumor growth and metastasis in orthotopic and genetic endpoint studies. Analysis of tumor tissue revealed that PG545 significantly decreased cell proliferation, increased apoptosis, reduced microvessel density, disrupted vascular function, and elevated intratumoral hypoxia. Elevated hypoxia is a known driver of collagen deposition and tumor progression; however, tumors from PG545-treated animals displayed reduced collagen deposition and a greater degree of differentiation compared with control or gemcitabine-treated tumors. These results highlight the potent antitumor activity of PG545 and support the further exploration of heparanase inhibitors as a potential clinical strategy for the treatment of PDAC.

Rhapontigenin inhibited hypoxia inducible factor 1 alpha accumulation and angiogenesis in hypoxic PC-3 prostate cancer cells.

Hypoxia inducible factor 1 alpha (HIF-1α) is frequently over-expressed in the numerous types of cancer and plays an important role in angiogenesis. In the present study, the inhibitory mechanism of rhapontigenin isolated from Vitis coignetiae was investigated on HIF-1α stability and angiogenesis in human prostate cancer PC-3 cells. Rhapontigenin significantly suppressed HIF-1α accumulation at protein level but not at mRNA level in PC-3 cells under hypoxia. Also, rhapontigenin suppressed hypoxia-induced HIF-1α activation in various cancer cells, such as colorectal adenocarcinoma (SW620), breast adenocarcinoma (MCF-7), fibrosarcoma (HT-1080) and prostate carcinoma (LNCaP). Interestingly, rhapontigenin had more potency in inhibition of hypoxia-induced HIF-1α expression than that of resveratrol, a known HIF-1α inhibitor. In addition, rhapontigenin promoted hypoxia-induced HIF-1α degradation and cycloheximide (CHX) blocked protein synthesis. A prolyl hydroxylase (PHD) inhibitor dimethyloxalylglycine (DMOG) is usually utilized to examine whether prolyl hydroxylation is involved in inhibition of HIF-1α accumulation. Here, DMOG recovered HIF-1α accumulation inhibited by rhapontigenin. Immunoprecipitation assay also revealed that rhapotigenin enhanced the binding of hydroxylated HIF-1α to von Hippel-Lindau (VHL) tumor suppressor protein. Furthermore, rhapontigenin reduced vascular endothelial growth factor (VEGF) secretion in hypoxic PC-3 cells as well as suppressed tube formation in human umbilical vein endothelial cells (HUVECs) treated by the conditioned media of hypoxic PC-3 cells. However, anti-angiogenic effect of rhapontigenin in hypoxic PC-3 cells was reversed by DMOG. Taken together, these findings suggest that rhapontigenin inhibits HIF-1α accumulation and angiogenesis in PC-3 prostate cancer cells.

The myc-miR-17~92 axis blunts TGF{beta} signaling and production of multiple TGF{beta}-dependent antiangiogenic factors.

c-Myc stimulates angiogenesis in tumors through mechanisms that remain incompletely understood. Recent work indicates that c-Myc upregulates the miR-17∼92 microRNA cluster and downregulates the angiogenesis inhibitor thrombospondin-1, along with other members of the thrombospondin type 1 repeat superfamily. Here, we show that downregulation of the thrombospondin type 1 repeat protein clusterin in cells overexpressing c-Myc and miR-17∼92 promotes angiogenesis and tumor growth. However, clusterin downregulation by miR-17∼92 is indirect. It occurs as a result of reduced transforming growth factor-ß (TGFß) signaling caused by targeting of several regulatory components in this signaling pathway. Specifically, miR-17-5p and miR-20 reduce the expression of the type II TGFß receptor and miR-18 limits the expression of Smad4. Supporting these results, in human cancer cell lines, levels of the miR-17∼92 primary transcript MIR17HG negatively correlate with those of many TGFß-induced genes that are not direct targets of miR-17∼92 (e.g., clusterin and angiopoietin-like 4). Furthermore, enforced expression of miR-17∼92 in MIR17HG(low) cell lines (e.g., glioblastoma) results in impaired gene activation by TGFß. Together, our results define a pathway in which c-Myc activation of miR-17∼92 attenuates the TGFß signaling pathway to shut down clusterin expression, thereby stimulating angiogenesis and tumor cell growth.

Plethora of agents, plethora of targets, plethora of side effects in metastatic renal cell carcinoma.

The plethora of novel agents recently approved for the management of metastatic renal cell carcinoma (RCC) has changed the therapeutic landscape in this disease. The plethora of targets some of these agents inhibit can result in a wide range of side effects. While these novel therapies can be viewed as inhibitors of angiogenesis that directly or indirectly target the vascular endothelial growth factor (VEGF) pathway, their individual mechanisms of action (MoA) are key to defining their side-effect profiles. Direct VEGF inhibition with the anti-VEGF monoclonal antibody bevacizumab, is primarily associated with side effects related to the precise inhibition of VEGF, such as proteinuria, hypertension and minor bleeding events. In contrast, non-VEGF-related side effects are observed with agents inhibiting multiple receptor tyrosine kinases (sunitinib, sorafenib, axitinib and pazopanib) and mammalian target of rapamycin inhibitors (temsirolimus and everolimus); these include diarrhoea, skin rash, stomatitis, hand-foot skin reaction, hypothyroidism, and haematological and metabolic abnormalities. This review discusses the MoA of these novel therapies and how a greater understanding of MoA may help to predict the range and type of side effects, develop combinations of agents with acceptable tolerability, enable a more rational approach to patient selection, and allow the development of effective side-effect management strategies.

Alzheimer's beta-amyloid peptide blocks vascular endothelial growth factor mediated signaling via direct interaction with VEGFR-2.

Beta-amyloid peptides (Abeta) are the major constituents of senile plaques and cerebrovascular deposits in the brains of Alzheimer's disease patients. We have shown previously that soluble forms of Abeta are anti-angiogenic both in vitro and in vivo. However, the mechanism of the anti-angiogenic activity of Abeta peptides is unclear. In this study, we examined the effects of Abeta1-42 on vascular endothelial growth factor receptor 2 (VEGFR-2) signaling, which plays a key role in angiogenesis. Abeta inhibited VEGF-induced migration of endothelial cells, as well as VEGF-induced permeability of an in vitro model of the blood brain barrier. Consistently, exogenous VEGF dose-dependently antagonized the anti-angiogenic activity of Abeta in a capillary network assay. Abeta1-42 also blocked VEGF-induced tyrosine phosphorylation of VEGFR-2 in two types of primary endothelial cells, suggesting an antagonistic action of Abeta toward VEGFR-2 signaling in cells. Moreover, Abeta was able to directly interact with the extracellular domain of VEGFR-2 and to compete with the binding of VEGF to its receptor in a cell-free assay. Co-immunoprecipitation experiments confirmed that Abeta can bind VEGFR-2 both in vitro and in vivo. Altogether, our data suggest that Abeta acts as an antagonist of VEGFR-2 and provide a mechanism explaining the anti-angiogenic activity of Abeta peptides.

The heparin binding motif of endostatin mediates its interaction with receptor nucleolin.

Endostatin is a potent angiogenesis inhibitor with heparin-dependent activities. Nucleolin, a novel functional receptor of endostatin, mediates both the internalization to endothelial cells and the antiangiogenic activity of endostatin. To define the exact role of the heparin binding motif in mediating the interaction between endostatin and its receptor nucleolin, up to six arginine residues (R155, R158, R184, R270, R193, and R194) located in the heparin binding motif of endostatin were substituted by alanine to make double, quadruple, or hexad point mutations, respectively. Contributions of the heparin binding motif to both the interaction with nucleolin and the biological activities of endostatin were investigated from in vitro to in vivo. Here we show that Arg to Ala point mutagenesis of the heparin binding motif does not interrupt the folding of endostatin but significantly impairs the interaction between endostatin and nucleolin. Double and quadruple mutants showed significantly decreased internalization to endothelial cells and antitumor activities, while the hexad Arg to Ala mutant completely lost its interaction with nucleolin and biological functions. Taken together, the present study demonstrates that the arginine clusters in the heparin binding motif of endostatin significantly contribute to its interaction with receptor nucleolin and mediate the antiangiogenic and antitumor activities of endostatin.

Papel do fator de crescimento endotelial vascular nos carcinomas de tireóide / The role of vascular endothelial growth factor in tumor

O crescimento tumoral está diretamente relacionado com a neovascularização, a qual decorre do desequilíbrio entre os fatores pró-angiogênicos e antiangiogênicos, secretados pelas células neoplásicas. O fator de crescimento endotelial vascular (VEGF) desempenha papel chave na angiogênese tumoral, estimulando a proliferação, migração e sobrevivência das células endoteliais. Atua através da ligação a receptores tirosina quinase específicos: VEGFR-1/Flt-1, VEGFR-2/KDR e VEGFR-3. O aumento da expressão do VEGF e de seus receptores tem sido associado à progressão, metastatização e pior prognóstico em diversos tumores malignos. A compreensão das vias moleculares que envolvem o mecanismo de indução da angiogênese tumoral por fatores de crescimento como o VEGF aumentam as possibilidades de novas terapêuticas a serem utilizadas no tratamento de tumores malignos humanos. Evidências indicam um importante papel do VEGF nas neoplasias da tireóide e a utilização de inibidores do VEGF ou de seus receptores pode constituir um importante recurso terapêutico, já tendo sido utilizado em determinados tipos de tumores humanos. O presente artigo tem como objetivo fazer uma revisão da atuação do VEGF no crescimento tumoral com enfoque nas neoplasias malignas da tireóide.

The neoplasic process is directly related to neovascularization, an imbalance between pro-angiogenic and antiangiogenic factors. The vascular endothelial growth factor (VEGF) plays a key role in tumor angiogenesis, stimulating proliferation, migration and survival of endothelial cells. VEGF acts through binding to specific tyrosine kinase receptor: VEGFR-1/Flt-1, VEGFR-2/KDR and VEGFR-3. Increased expression of VEGF and its receptors have been associated with progression, metastasis and worse prognosis in human malignant tumors. Understanding molecular pathways of tumor angiogenesis related to growth factors such as VEGF is a crucial step on developing new treatment options. Evidence indicates an important role of VEGF in thyroid cancer and inhibition of VEGF or its receptors may constitute an important therapeutic resource, particularly for those patients with metastatic diseases. This aim of this article is to review the role of VEGF in tumor growth, focusing on thyroid malignancies.

Sunitinib malate, a receptor tyrosine kinase inhibitor, is effective in the treatment of restrictive heart failure due to heart metastases from renal cell carcinoma.

Few systematic trials have studied metastatic tumors to the heart and there are currently no guidelines for the treatment of heart metastases and its associated symptoms. This article presents the first known case of effective pharmacological treatment of heart failure due to metastases of renal cell carcinoma (RCC). Due to pressure caused by metastatic tissue on the left atrium and the decreased blood inflow to the left ventricle, the 61-year-old male patient suffered from dyspnea. Treatment with sunitinib, an oral multitargeted receptor tyrosine kinase inhibitor, was initiated and led to a decrease in the mass of the metastasis infiltrating the left atrium. Arterial hypertension caused by sunitinib therapy was effectively controlled by the use of an angiotensin-converting-enzyme inhibitor. Therapy with sunitinib reduced the symptoms of exercise intolerance; the patient felt much better and was able to return to his family and resume professional activity. Further studies are required to confirm the utility of sunitinib therapy in patients with symptoms of heart failure due to heart metastases from RCC.

HDAC5 is a repressor of angiogenesis and determines the angiogenic gene expression pattern of endothelial cells.

Class IIa histone deacetylases (HDACs) are signal-responsive regulators of gene expression involved in vascular homeostasis. To investigate the differential role of class IIa HDACs for the regulation of angiogenesis, we used siRNA to specifically suppress the individual HDAC isoenzymes. Silencing of HDAC5 exhibited a unique pro-angiogenic effect evidenced by increased endothelial cell migration, sprouting, and tube formation. Consistently, overexpression of HDAC5 decreased sprout formation, indicating that HDAC5 is a negative regulator of angiogenesis. The antiangiogenic activity of HDAC5 was independent of myocyte enhancer factor-2 binding and its deacetylase activity but required a nuclear localization indicating that HDAC5 might affect the transcriptional regulation of gene expression. To identify putative HDAC5 targets, we performed microarray expression analysis. Silencing of HDAC5 increased the expression of fibroblast growth factor 2 (FGF2) and angiogenic guidance factors, including Slit2. Antagonization of FGF2 or Slit2 reduced sprout induction in response to HDAC5 siRNA. Chromatin immunoprecipitation assays demonstrate that HDAC5 binds to the promoter of FGF2 and Slit2. In summary, HDAC5 represses angiogenic genes, such as FGF2 and Slit2, which causally contribute to capillary-like sprouting of endothelial cells. The derepression of angiogenic genes by HDAC5 inactivation may provide a useful therapeutic target for induction of angiogenesis.

Modulation of retinal capillary endothelial cells by Müller glial cell-derived factors.

PURPOSE: The inner blood-retinal barrier (BRB) is a gliovascular unit in which macroglial cells surround capillary endothelial cells and regulate retinal capillaries by paracrine interactions. The purpose of the present study was to identify genes of retinal capillary endothelial cells whose expression is modulated by Müller glial cell-derived factors. METHODS: Conditionally immortalized rat retinal capillary endothelial (TR-iBRB2) and Müller (TR-MUL5) cell lines were chosen as an in vitro model. TR-iBRB2 cells were incubated with conditioned medium of TR-MUL5 (MUL-CM) for 24 h and subjected to microarray and quantitative real-time PCR analysis. RESULTS: TR-MUL5 cell-derived factors increased alkaline phosphatase activity in TR-iBRB2 cells, indicating that paracrine interactions occurred between TR-iBRB2 and TR-MUL5 cells. Microarray analysis demonstrated that MUL-CM treatment leads to a modulation of several genes including an induction of plasminogen activator inhibitor 1 (PAI-1) and a suppression of an inhibitor of DNA binding 2 (Id2) in TR-iBRB2 cells. Treatment with TGF-beta1, which is incorporated in MUL-CM, also resulted in an induction of PAI-1 and a suppression of Id2 in TR-iBRB2 cells. CONCLUSIONS: In vitro inner BRB model study revealed that Müller glial cell-derived factors modulate endothelial cell functions including the induction of anti-angiogenic PAI-1 and the suppression of pro-angiogenic Id2. Therefore, Müller cells appear to be one of the modulators of retinal angiogenesis.

Semaphorin-3B is an angiogenesis inhibitor that is inactivated by furin-like pro-protein convertases.

Semaphorin-3B (sema3B) and semaphorin-3F (sema3F) are secreted tumor suppressors of lung cancer. Sema3F functions as an antiangiogenic factor that repels endothelial cells and compromises their proliferation/survival. However, tumor cells expressing either endogenous or recombinant sema3B fail to repel endothelial cells efficiently. Sema3B found in the conditioned medium of such cells is almost completely cleaved by furin-like pro-protein convertases, generating inactive 61- and 22-kDa fragments. We have generated a sema3B variant that was point mutated at the cleavage site (sema3B-m), thereby conferring partial resistance to cleavage. Conditioned medium from HEK293 cells expressing sema3b-m and conditioned medium of HEK293 cells expressing sema3B contained similar concentrations of semaphorin but sema3B-m was cleaved much less than sema3B. In contrast to HEK293 cells expressing native sema3B, cells expressing sema3b-m strongly repel endothelial cells. Conditioned medium from sema3B-m-expressing cells rapidly caused disassembly of focal adhesions and a collapse of the actin cytoskeleton of endothelial cells, inhibited vascular endothelial growth factor-induced phosphorylation of extracellular signal-regulated kinase 1/2, induced apoptosis of endothelial cells, and inhibited the formation of tubes from endothelial cells in an in vitro angiogenesis assay more potently than conditioned medium from cells expressing sema3B. Furthermore, HEK293 cells expressing sema3B-m inhibited basic fibroblast growth factor-induced angiogenesis in vivo much more potently than cells expressing sema3B. Repulsion of human umbilical vascular endothelial cells by sema3B-m was mediated primarily by the neuropilin-1 (np1) receptor but sema3B-m was also able to transduce signals via neuropilin-2 (np2). These results suggest that up-regulation of furin-like pro-protein convertases in malignant cells may enable tumors to evade the antiangiogenic effects of sema3B.

The heparin-binding site of antithrombin is crucial for antiangiogenic activity.

The heparin-binding site of antithrombin is shown here to play a crucial role in mediating the antiangiogenic activity of conformationally altered cleaved and latent forms of the serpin. Blocking the heparin-binding site of cleaved or latent antithrombin by complexation with a high-affinity heparin pentasaccharide abolished the serpin's ability to inhibit proliferation, migration, capillary-like tube formation, basic fibroblast growth factor (bFGF) signaling, and perlecan gene expression in bFGF-stimulated human umbilical vein endothelial cells. Mutation of key heparin binding residues, when combined with modifications of Asn-linked carbohydrate chains near the heparin-binding site, also could abrogate the anti-proliferative activity of the cleaved serpin. Surprisingly, mutation of Lys114, which blocks anticoagulant activation of antithrombin by heparin, caused the native protein to acquire antiproliferative activity without the need for conformational change. Together, these results indicate that the heparin-binding site of antithrombin is of crucial importance for mediating the serpin's antiangiogenic activity and that heparin activation of native antithrombin constitutes an antiangiogenic switch that is responsible for turning off the antiangiogenic activity of the native serpin.

Inibição da angiogênese: novo alvo no combate ao câncer / Angiogenesis' inhibition: new target against cancer

A formação de novos vasos sanguíneos é de fundamental importância para o desenvolvimento do câncer, visto que a hipóxia e a falta de nutrientes podem causar apoptose (morte celular programada) de células neoplásicas. Este trabalho tem por objetivo elucidar o mecanismo molecular da angiogênese e apresentar os principais grupos de inibidores, bem como as fases de estudos clínicos em que cada droga antiangiogênica está sendo hoje utilizada. Serão descritas inicialmente as fases dos estudos para o desenvolvimento de novos fármacos e a seguira classificação em grupos dos principais fármacos inibidores da angiogênese,que são: inibidores de metaloproteinases, inibidores da proliferação e migração de células endoteliais, inibidores de fatores decrescimento, inibidores de integrinas, quelantes de cobre e antiangiogênicos de mecanismos distintos. Será apresentado ainda o mecanismo ou alvo de ação de tais drogas, bem como os tipos específicos de tumores em que cada antiangiogênico está sendo usado. Os dados apresentados nesse trabalho mostram que nos últimos anos a inibição da angiogênese tornou-se um importante alvo para pesquisas que visam o desenvolvimento de novas terapias no combate ao câncer.

Investigation of novel fumagillin analogues as angiogenesis inhibitors.

Modification of fumagillin was conducted to develop MetAP-2 inhibitors with desirable pharmacological properties. Replacement of the C4 side chain by benzyloxime preserves the inhibitory activity against MetAP-2 enzyme. Fumagillin analogues containing the C4 benzyloxime moiety were found to be very sensitive to the nature of the C6 substituent on the inhibition activity of HUVEC proliferation. This lack of correlation between MetAP-2 and HUVEC activities might be due to the cellular metabolism of the compounds by epoxide hydrolase, which is present in the cell. Compound (E)-3d, containing ethylpiperazinyl carbamate at C6 position, exhibited antiangiogenic effects similar to TNP-470 on matrigel plug assay and rat corneal micropocket assay.

NO and angiogenesis.

Angiogenesis requires the elaboration of endothelium-derived nitric oxide (NO). Angiogenic factors induce the release of NO from endothelial cells, which mediates a multiplicity of processes involved in angiogenesis. These NO-modulated processes include endothelial cell survival, proliferation, migration, and interaction with the extracellular matrix. Derangements of the NO synthase pathway impair angiogenesis. Accordingly, the competitive inhibitor of the NOS pathway asymmetric dimethylarginine (ADMA) acts as an endogenous inhibitor of angiogenesis. By contrast, agents which increase NO synthesis, such as low dose statins, enhance angiogenesis. Modulation of the NO synthase pathway could become a new therapeutic avenue for angiogenesis-related disorders.

Novel bicyclic oxazolone derivatives as anti-angiogenic agents.

Novel bicyclic tetrahydropyrano[3,2-d]oxazolones derivatives, analogues of Fumagillin, were synthesised via a stereocontrolled oxidative-rearrangement of furylcarbinols and subsequent treatment with the appropriate isocyanate. These compounds demonstrated potent antiangiogenic activity.