Blockage of vascular endothelial growth factor (VEGF) reduces experimental pleurodesis

Background and objective

Chemical pleurodesis controls recurrent malignant pleural effusion. The mechanism that determines pleural symphysis involves the action of vascular endothelial growth factor (VEGF). We assessed the influence of the anti-VEGF antibody (bevacizumab) on pleurodesis induced by talc or silver nitrate and analyzed the temporal development of pleural angiogenesis.

Methods

Sixty New Zealand rabbits received intrapleural injection (2 mL) of talc (400 mg/kg) or 0.5% silver nitrate. In each group, half of the animals received an intravenous injection of bevacizumab 30 min before the sclerosing agent. Five animals from each group were euthanized 7, 14, or 28 days after the procedure. Adhesions and inflammation (scores: 0-4), thickness (μm), vascular density (vessels/field), and collagen fibers (μm²) were evaluated in the visceral pleura.

Results

Antibody anti-VEGF interferes in pleurodesis induced by talc or silver nitrate. Pleural inflammation was discreet with no difference between the groups, regardless the anti-VEGF treatment. Concerning the vascular density of the visceral pleura, a smaller number of neoformed vessels was noted in the animals that received bevacizumab. In the animals receiving silver nitrate, the decrement in adhesions and vascular density was associated with reduced thick and thin collagen fibers, resulting in less pleural thickness.

Conclusion

The anti-VEGF antibody inhibits adhesions between pleural layers. Despite being an experimental study in animals with normal pleura, the results call attention to a likely lack of success in pleurodesis when VEGF blockers are used.     

VEGF硫代反义寡核苷酸抑制U937细胞VEGF的表达

Objective： To study the effect of VEGF antisense oligodeoxynucleotide （VEGF ASODN） on VEGF expression in acute monocyte leukemic cell line U937 in vitro. Methods： U937 cells were incubated with VEGF ASODN （final concentration as follows： 10, 20 and 30 μmol/L respectively） or scrambled sequence, compared with negative control. The expression of VEGF mRNA was measured by semi-quantitative RT-PCR, VEGF protein was measured by Western blot. Results： VEGF ASODN obviously inhibited expression of VEGF mRNA in U937 cell, compared with scrambled sequence and negative control （P〈0.05）. And the inhibition effect was most remarkable after 24 h, which is related with the dose of VEGF ASODN （P〈0.05）. Scrambled sequence groups had no significant difference compared with negative control groups （P〉0.05）. VEGF ASODN obviously inhibited expression of VEGF protein, compared with scrambled sequence and negative control （P〈0.05）. Conclusion： The expressions of VEGF at mRNA and protein levels in leukemic cell line U937 are down-regulated after being treated with VEGF ASODN.     

Use of soluble recombinant decoy receptor vascular endothelial growth factor trap (VEGF Trap) to inhibit vascular endothelial growth factor activity

Primary tumors and metastases require blood vessel formation to support their continued growth and eventual metastasis. They use existing vasculature during initial growth but eventually must orchestrate the development and maintenance of new vessels--a process termed angiogenesis--to grow beyond a small size and spread. Angiogenesis is regulated by a number of soluble factors, the relative proportions of which can exacerbate or inhibit the process. Vascular endothelial growth factor (VEGF) is a potent stimulator of angiogenesis, produced by the majority of human solid tumors. Inhibitors of VEGF might have an impact on the growth and metastasis of these cancers. The relevance of this strategy to the treatment of colorectal cancer was first successfully demonstrated in human clinical trials using a monoclonal antibody against VEGF. A potent antiangiogenic soluble recombinant decoy, VEGF Trap is a protein constructed from VEGF receptor-binding domains linked to an immunoglobulin G(1) constant region. It possesses an affinity for VEGF that is significantly higher than that of the monoclonal antibody. VEGF Trap has demonstrated marked efficacy in halting angiogenesis and shrinking tumors in preclinical animal models and is currently being studied in phase I clinical trials in humans with advanced solid malignancies.     

Expression of vascular endothelial growth factor (VEGF) and VEGF receptors in tumor angiogenesis and malignancies

Angiogenesis is a process by which new blood vessels are formed from preexisting vessels. New blood vessel formation by angiogenesis involves the degradation of extra-cellular matrix combined with sprouting and migration of endothelial cells from preexisting capillaries. Solid tumors consist of several components, including normal and stromal cells, extracellular matrix, and vasculature. To grow and metastasize, tumors must stimulate the development of new vasculature through angiogenesis. Vascular endothelial growth factor (VEGF) is a potent angiogenic peptide with biologic effects that include regulation of hematopoietic stem cell development, extracellular matrix remodeling, and inflammatory cytokine regeneration. VEGF is both a vascular growth factor and a vascular permeability factor. Its expression can upregulate several proangiogenic and prometa-static molecules. As a central mediator of angiogenesis, VEGF has emerged as an important target for antiangiogenic therapy. In this review, the authors describe the essential characteristics of VEGF and the VEGF family of ligands and their receptors. They also provide an overview of the central role of VEGF in physiologic and pathologic angiogenesis, directly or indirectly. This review sheds light on the importance of VEGF-targeted antiangiogenic therapy based on the monoclonal antibodies against VEGF, small interfering RNA, and therapy directed against VEGF-VEGFR kinase. It also gives a brief overview of the natural products or dietary compounds that could be used as antiangiogenic agents. Therapeutic inhibition of vessel formation could be best suited to preventive strategies aimed at the suppression of angiogenesis in primary tumors in subjects at risk or of micrometastases after surgical removal of primary tumor.     

Immunohistochemical evaluation of vascular endothelial growth factor (VEGF) in colorectal carcinoma

BACKGROUND: Vascular endothelial growth factor (VEGF) is one of the most important proangiogenic factors over-expressed in many human cancers and is usually associated with an unfavorable outcome. This work was planned to assess VEGF and microvessel density (MVD) in colorectal carcinoma (CRC) and to correlate them with the available clinicopathological parameters. MATERIAL AND METHODS: Ten normal colonic mucosa, 21 adenoma and 70 CRC cases were examined by immunohistochemical staining using anti-VEGF antibody. RESULTS: Eighty-one percent (81%) of adenoma and 78.6% of CRC cases showed VEGF immunoreactivity; however, the intensity of staining was significantly in favour of malignant cases (p=0.032). VEGF immunostaining in CRC was correlated with low grade (p=0.009), early stage either by Dukes' system (p=0.03) or TNM stage (p=0.03), negative nodal status (p=0.04) and high mast cell count (p=0.04). MVD assessed by Haematoxylin and Eosin staining was associated with dense inflammatory response (p=0.003) and high mast cell count (p=0.006). CONCLUSIONS: VEGF could be an early carcinogenic factor in CRC that declines with its progression. Inflammatory cells including mast cells could play a role in CRC angiogenesis.     

The clinical toxicity profile of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor (VEGFR) targeting angiogenesis inhibitors; a review

Clinical experience with vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor (VEGFR) targeting angiogenesis inhibitors is rapidly increasing, and some compounds have already been approved for regular anticancer treatment.Apart from their activity, much attention has been focussed on the clinical toxicity profile of these compounds.This review describes the most frequently occurring side-effects of both antibodies and tyrosine kinase inhibitors and discusses some of the underlying mechanisms. Some practical guidelines for treatment of the side-effects are given.     

Activated Ras enhances insulin-like growth factor I induction of vascular endothelial growth factor in prostate epithelial cells

Mutations in the three closely related RAS genes, HRAS, KRAS, and NRAS are among the most common mutations found in human cancer; reaching 50% in some types of cancer, such as colorectal carcinoma, and 10% in prostate cancers. The activated Ras proteins produced by these mutations can, among other cellular changes, increase vascular endothelial growth factor (VEGF) production. Moreover, tumors bearing RAS gene mutations are more vascular than tumors without RAS mutations. We find that, in prostate epithelial cells, the introduction of an activated HRAS causes cells to produce VEGF in response to insulin-like growth factor I (IGF-I). In comparison, cells lacking an activated Ras are unable to produce VEGF in response to IGF-I. This effect of Ras may occur through stabilization of a second messenger protein, insulin receptor substrate 1, that mediates PI 3-kinase-dependent signaling. Because IGF-I is a paracrine/endocrine hormone that has been associated with increased risk for several types of cancer, these results suggest a novel interrelationship between oncogenic conversion of a cellular gene such as HRAS, and IGF-I produced locally for normal tissue homeostasis.     

PTEN基因转染对白血病细胞VEGF调控作用的影响

目的:探讨在白血病细胞中与张力蛋白同源的10号染色体缺失的磷酸酶基因(phosphatase and tensin hemology deleted on chromosome ten gene,PTEN)对血管内皮生长因子(vascular endothelial growth factor,VEGF)及其受体1(VEGF receptor 1,VEGFR1)调控作用的影响.方法:将携带有野生型PTEN及绿色荧光蛋白(green fluorescent protein,GFP)基因的腺病毒(Ad-PTEN-GFP)及空载体腺病毒(Ad-GFP)转染人慢性粒细胞白血病急变细胞株K562,实时荧光定量PCR法检测不同转染组细胞中PTEN、VEGF和VEGF1 mRNA表达水平,Western印迹法检测PTEN、VEGF、Akt和磷酸化Akt蛋白的表达水平,并采用Transwell小室侵袭实验检测不同转染组细胞的侵袭性.通过MTT实验及FCM法检测PTEN基因对脐静脉内皮细胞株ECV304增殖和凋亡的影响.通过鸡胚尿囊膜(chick chorioallantoic membrane,CAM)体内血管生长实验检测PTEN基因对鸡胚血管生成的影响.结果:与空载体腺病毒(Ad-GFP)相比,Ad-PTEN-GFP 转染人白血病细胞K562后,VEGF及其受体的表达被明显抑制,并呈剂量依赖性负相关;同时,Ad-PTEN-GFP 转染后K562细胞侵袭能力明显减弱.PTEN基因转染能够抑制血管内皮细胞ECV304增殖,并促进其细胞凋亡,细胞周期阻滞在S期.PTEN基因转染可明显抑制CAM血管生长.结论:肿瘤抑制基因PTEN能够抑制内皮细胞增殖和白血病细胞侵袭,其作用机制可能是负调控白血病细胞VEGF表达以及抑制肿瘤血管新生.     

The role of vascular endothelial growth factor (VEGF) in AIDS-related Kaposi's sarcoma

Kaposi's sarcoma (KS) is the most common neoplasm associated with human immunodeficiency virus-1 (HIV-1) infection. KS involves the skin and mucous membranes as well as other organs and can lead to tumor-associated edema and ulcerations. Despite therapy with highly active antiviral agents, most patients with HIV-1-related KS eventually develop disseminated disease. In the treatment of KS, a strong rationale exists for the use of agents that inhibit vascular endothelial growth factor (VEGF). Angiogenesis appears to be an important feature of this disease, and recent experimental studies have demonstrated the role of VEGF and its receptors in the pathogenesis of KS. Thus, therapeutic agents that target the VEGF pathway may be an effective strategy in reducing the tumor growth and edema associated with KS. Phase I study results with SU5416, a synthetic low molecular-weight inhibitor of the VEGF-Flk-1/KDR receptor tyrosine kinase, demonstrate that this agent is well tolerated. Preliminary results show that in a majority of patients with autoimmune deficiency syndrome (AIDS)-related disease, SU5416 clearly has biological activity (it flattens, shrinks, or dissolves lesions and reduces or resolves edema) or stabilizes the disease. Angiogenesis inhibition with SU5416 is a promising therapeutic approach in treating patients with KS, and further clinical evaluation is currently under way.     

血管内皮生长因子在子宫颈癌组织中的表达及意义

目的　探讨血管内皮生长因子 (VEGF ,VEGFmRNA)在子宫颈癌组织中的表达及意义。方法　采用免疫组织化学技术SP法及原位杂交方法检测 33例宫颈癌 ,其中鳞癌 2 0例 ,腺癌 13例及 10例正常宫颈组织中VEGF及VEGFmRNA的表达情况。结果　宫颈癌组织切片中VEGF及VEGFmRNA皆有活跃表达。正常宫颈组织中VEGFmRNA呈阴性表达 ,VEGF蛋白可见弱阳性表达 ,两组比较差异有显著性 (P <0 .0 5 ) ;宫颈癌组织切片中的VEGFmRNA的表达与宫颈癌病理类型比较差异有显著性 (P <0 .0 5 ) ;而与宫颈癌临床分期及病理分化程度比较差异无显著性 (P >0 .0 5 )。结论　VEGF及VEGFmRNA的阳性表达在子宫颈癌的发生 ,发展中可能有着重要的意义。VEGF的检测对判断宫颈癌的病理类型有一定的临床价值。     

VEGF和MMP-9在食管癌中的表达及低氧调节

目的 研究血管内皮生长因子（VEGF）和基质金属蛋白酶－9（MMP－9）的表达与食管癌血管形成和临床的关系,以及低氧对其的调节作用。方法 用逆转录－聚合酶链式反应（RT－PCR）检测了42例食管癌手术标本（包括18例癌旁组织）中VEGF和MMP－9mRNA的表达,用免疫组化染色的方法检测了56例食管癌标本中VEGF蛋白的表达和平均血管密度（MVD）,同时用酶联免疫吸附试验（ELISA）的方法定量测定了低氧对食管癌细胞系中VEGF和MMP－9表达的影响。结果 食管癌中VEGF的表达显著高于癌旁组织,与肿瘤内平均MVD密切正相关,VEGF表达和肿瘤中MVD计数与食管癌的分期、淋巴结转移密切相关。食管癌中MMP－9的表达也显著高于癌旁组织,但MMP－9的表达与食管癌中的MVD计数和临床病理特征无关。低氧可以显著增加食管癌细胞系中VEGF的表达,但对MMP－9的表达无明显影响。结果 VEGF的表达可能在食管癌血管形成和转移中起重要作用,并受低氧调节,有可能作为反映食管癌进展的生物学指标和抗血管治疗的靶点。     

In vivo neutralization of vascular endothelial growth factor (VEGF) vascular permeability factor (VPF) inhibits ovarian carcinoma-associated ascites formation and tumor growth

Vascular endothelial growth factor (VEGF)/ vascular permeability factor (VPF) is emerging as an important growth factor in a variety of tumor types. As a potent endothelial cell mitogen and vascular permeabilizing agent, VEGF/VPF has the unique functional capacity to mediate the component events of solid tumor neovascularization and ascites tumor growth. In the present series of investigations, our experimental hypothesis was that VEGF/VPF is a critical mediator of ovarian carcinoma-associated ascites formation and solid tumor growth. Athymic nude mice xenotransplanted with human ovarian carcinoma cell lines received either a preimmune rabbit serum or VEGF/VPF antiserum. Compared with the control group receiving the preimmune serum, the antiserum-treated animals displayed a 10- and 12-fold reduction in ascites accumulation and solid tumor growth, respectively. The administration of a neutralizing antiserum to VEGF/VPF conferred a modest survival advantage to animals harboring intraperitoneal tumors. These data demonstrate the significance of VEGF/VPF in the pathogenesis of ovarian carcinoma and suggest that interventions targeting this growth factor and/or its receptor may be of therapeutic value in the management of ovarian cancer.     

Vascular endothelial growth factor (VEGF) inhibition by small molecules

Angiogenesis is essential for primary tumours to grow and metastasise, and is driven by the production of positive angiogenic factors. The Vascular Endothelial Growth Factor (VEGF) family is central to the process of angiogenesis and comprises 5 molecules designated A, B, C, D and E. VEGF is overexpressed in several solid malignancies. The actions of VEGF are mediated through receptors possessing tyrosine kinase activity: VEGFR-1 (Flt-1), VEGFR-2 (Kdr/Flk-1) and VEGFR-3 (Flt-4). Anti-VEGF strategies include the use of antibodies to VEGF or its receptors, the use of ribozymes to decrease receptor expression, and the use of inhibitors of tyrosine kinase to reduce receptor activation and downstream signalling. The focus of this review is small molecule inhibitors of VEGF receptors which target their intrinsic tyrosine kinase activity. The clinical development of the following agents is discussed: SU5416, SU11248, SU6668, PTK/ZK, ZD6474.     

Elevated vascular endothelial growth factor (VEGF) serum levels in idiopathic myelofibrosis.

An increase of angiogenesis has been shown in idiopathic myelofibrosis with myeloid metaplasia (MMM) by microvessel density count method but evaluation of circulating angiogenic factors is still incomplete. In 31 patients affected by MMM and in 12 healthy subjects we evaluated the serum levels of VEGF (vascular endothelial growth factor) and correlated VEGF with clinical and laboratory features of disease. We found that MMM patients had circulating VEGF concentrations much higher than controls (Median 1208 ng/ml vs 138 ng/ml, P < 0.0001). No correlation was found between VEGF and Hb, WBC, PLT, LDH, creatinine, bone marrow cellularity, fibrosis, splenomegaly, hepatomegaly, and therapy. However, in the subgroup of patients with a normal or low VEGF concentration, a direct correlation between VEGF and platelet count (r = 0.90, P = 0.002) was detected. Moreover, patients with a platelet count < 300 x 10(9)/l had VEGF serum levels lower than patients with a higher PLT count (median VEGF 864 vs 1557 pg/ml, P = 0.001). In six patients and in eight controls we also had the opportunity to measure VEGF in the plasma and we calculated that VEGF concentration was much higher in platelet-rich than in platelet-poor plasma and that platetets of MMM patients contained four times more VEGF than those of healthy controls. These results indicate that VEGF is overproduced in MMM, thus confirming an increased angiogenic activity. Platelets are probably a major source of VEGF in MMM but not the only one.