Inhibition of angiogenesis and tumor progression by hydrodynamic cotransfection of angiostatin K1-3, endostatin, and saxatilin genes

In vivo expression of angiostatin and endostatin, two different types of endothelial cell growth inhibitor, have been reported to inhibit vascularization in tumor tissues, resulting in tumor growth inhibition. Recently, in vivo expression of saxatilin, a novel disintegrin purified from snake (Gloydius saxatilis) venom, was able to strongly inhibit endothelial cell proliferation and smooth muscle cell migration, resulting in tumor growth inhibition. However, the antitumor efficacy of the individual antiangiogenic molecules expressed in vivo was not sufficiently potent to induce tumor regression in animal models. Therefore, in this study, we have systemically examined how combinational transfer of angiostatin, endostatin, and saxatilin genes affects neovascularization in tumor tissues and tumor progression in a mouse model. In Matrigel-implanted mice, cotransfection with plasmids encoding angiostatin K1-3 (pFLAG-Angio K1/3), endostatin (pFLAG-Endo), and saxatilin (pFLAG-Sax) resulted in the most effective inhibition of angiogenesis. In addition, hydrodynamic cotransfection of the three genes induced more inhibition of B16BL6 melanoma growth and pulmonary metastasis than other combinations of transfected genes. Compared with the empty vector-treated control group, cotreatment with the three plasmids reduced B16BL6 tumor growth by 89% and pulmonary metastasis by 90%. These results provide additional evidence supporting the combined systemic expression of antiangiogenic factors, such as angiostatin K1-3, endostatin, and saxatilin, as an alternative procedure for antiangiogenic cancer therapy.     

Angiostatin-like activity of a monoclonal antibody to the catalytic subunit of F1F0 ATP synthase

The antiangiogenic protein angiostatin inhibits ATP synthase on the endothelial cell surface, blocking cellular proliferation. To examine the specificity of this interaction, we generated monoclonal antibodies (mAb) directed against ATP synthase. mAb directed against the beta-catalytic subunit of ATP synthase (MAb3D5AB1) inhibits the activity of the F(1) domain of ATP synthase and recognizes the catalytic beta-subunit of ATP synthase. We located the antibody recognition site of MAb3D5AB1 in domains containing the active site of the beta-subunit. MAb3D5AB1 also binds to purified Escherichia coli F(1) with an affinity 25-fold higher than the affinity of angiostatin for this protein. MAb3D5AB1 inhibits the hydrolytic activity of F(1) ATP synthase at lower concentrations than angiostatin. Like angiostatin, MAb3D5AB1 inhibits ATP generation by ATP synthase on the endothelial cell surface in acidic conditions, the typical tumor microenvironment where cell surface ATP synthase exhibits greater activity. MAb3D5AB1 disrupts tube formation and decreases intracellular pH in endothelial cells exposed to low extracellular pH. Neither angiostatin nor MAb3D5AB1 showed an antiangiogenic effect in the corneal neovascularization assay; however, both were effective in the low-pH environment of the chicken chorioallantoic membrane assay. Thus, MAb3D5AB1 shows angiostatin-like properties superior to angiostatin and may be exploited in cancer chemotherapy.     

Expression of the antiangiogenic factor 16K hPRL in human HCT116 colon cancer cells inhibits tumor growth in Rag1(-/-) mice

The M(r) 16,000 NH(2)-terminal fragment of human prolactin (16K hPRL) is a potent antiangiogenic factor inhibiting endothelial cell function in vitro and neovascularization in vivo. The present study was undertaken to test the ability of 16K hPRL to inhibit the growth of human HCT116 colon cancer cells transplanted s.c. into Rag1(-/-) mice. For this purpose, HCT116 cells were stably transfected with an expression vector encoding a peptide that included the signal peptide and first 139 amino acid residues of human prolactin (HCT116(16K)). Stable clones of HCT116(16K) cells secreted large amounts of biologically active 16K hPRL into the culture medium. Growth of HCT116(16K) cells in vitro was not different from wild-type HCT116 (HCT116(wt)) or vector-transfected HCT116 (HCT116(vector)) cells. Addition of recombinant 16K hPRL had no effect on the proliferation of HCT116(wt) cells in vitro. Tumor growth of HCT116(16K) cells implanted into Rag1(-/-) mice was inhibited 63% in four separate experiments compared with tumors formed from HCT116(wt) or HCT116(vector) cells. Inhibition of tumor growth of HCT116(16K) cells was correlated with a decrease in microvascular density by 44%. These data demonstrate that biologically active 16K hPRL can be expressed and secreted from human colon cancer cells using a gene transfer approach and that production of 16K hPRL by these cells was capable of inhibiting tumor growth and neovascularization. These findings support the potential of 16K hPRL as a therapeutic agent for the treatment of colorectal cancer.     

Antitumor effects of angiostatin K1-3 and endostatin genes coadministered by the hydrodynamics-based transfection method

Angiostatin and endostatin are potent endothelial cell growth inhibitors and have been carefully evaluated for antiangiogenic cancer therapy. Previously, we have shown that subcutaneous administration of angiostatin K1-3 and endostatin genes complexed with liposomal vectors is a more practical treatment procedure than administration of angiostatin and endostatin proteins. This study provides additional conclusive evidence supporting the effectiveness of antiangiogenic cancer gene therapy employing angiostatin K1-3 and endostatin genes. Plasmids encoding a mouse angiostatin K1-3 gene (pFLAG-AngioK1/3) and an endostatin gene (pFLAG-Endo) were introduced by the hydrodynamic transduction method into mice carrying Matrigel plugs or B16BL6 mouse melanoma tumors. A single systemic injection of the two genes exhibited potent antiangiogenic and antitumor activity in the mouse model. Hydrodynamic coadministration of the genes inhibited the B16BL6 mouse melanoma growth and pulmonary metastasis more effectively than administration of either gene alone. Compared with the untreated control group, the mice cotreated with pFLAG-AngioK1/3 and pFLAG-Endo exhibited 75% reduction of tumor growth while those treated with pFLAG-AngioK1/3 or pFLAG-Endo showed 46% and 52% reduction, respectively. The cotreatment inhibited B16BL6 pulmonary metastasis formation by 80% while the inhibition induced by individual treatment with pFLAG-AngioK1/3 or pFLAG-Endo was 68% and 71%, respectively. These results provide additional evidence that systemic expression of angiostatin K1-3 and/or endostatin genes is a viable alternative procedure for antiangiogenic cancer therapy.     

携带血管抑素K1-5基因的腺病毒载体对血管内皮细胞增殖的抑制作用

目的 研究携带血管抑素K1-5基因的腺病毒载体对其对血管内皮细胞增殖的抑制作用.方法 采用直接感染台盼蓝染色排除法、MTT实验检测血管抑素K1-5对血管内皮细胞增殖的抑制作用.结果 直接感染台盼蓝染色排除法及MTT法检测表明,携带血管抑素K1-5基因的腺病毒能显著抑制血管内皮细胞增生,并对其具有杀伤力.结论 血管抑素K1-5能明显抑制血管内皮细胞增殖,为进一步体内实验,研究其对血管形成的抑制作用奠定了基础.     

Kringle 5 of human plasminogen suppresses hepatocellular carcinoma growth both in grafted and xenografted mice by anti-angiogenic activity

Plasminogen kringle 5 (K5), a proteolytic fragment of plasminogen, is an endogenous angiogenic inhibitor. We have previously shown that K5 inhibits ischemia-induced retinal neovascularization in a rat model. However, its anti-angiogenic potential and application in the treatment of neoplastic diseases have not been well investigated. Our present study was designed to test its effect on the neovascularization and growth of hepatocellular carcinoma, a typical hypervascular tumor. Recombinant human K5 was expressed in E. coli and purified by affinity chromatography. K5 inhibited proliferation and induced apoptosis of primary endothelial cells in dose-dependent manner, but no effect on pericytes from the same origin of endothelial cells, which suggested an endothelial cell-specific inhibition. Moreover, K5 had no effect on the proliferation and apoptosis of mouse HepA and human Bel7402 hepatoma cell lines even in the enhanced concentration range, which suggested K5 having no direct effect on tumor cells. Ventral injection of K5 significantly suppressed the tumor growth in graphed hepatocarcinoma mice model, which was established by injection of mouse HepA hepatoma cells. In xenografted hepatocarcinoma athymic mice model, which mimicked human tumors by injection of human Bel7402 hepatoma cells, K5 significantly suppressed the tumor growth. An average of 68% suppression of primary tumor growth was observed in the K5-treated mice compared with control group. K5 also inhibited intratumoral neovascularization in the two cancer models determined by micro vessel density (MVD) analysis. Injection of K5 significantly induced the cleavage of pro-caspase-3 in tumor tissues of grafted mouse model, which suggested K5 also induced apoptosis of tumor tissues and the decreased intratumoral microvascular density in K5 treated group may correlate with K5-induced endothelial cell apoptosis. These results suggest that tumor growth suppression of K5 depends on its anti-angiogenic activity and K5 could have therapeutic potential in hepatocellular carcinoma.     

Generation of angiostatin-like fragments from plasminogen by prostate-specific antigen

Angiostatin, a potent inhibitor of angiogenesis, tumour growth and metastasis, is a biologically active fragment of plasminogen, containing the kringle domains 1-4. It is generated from plasminogen by limited proteolysis. We show that prostate-specific antigen (PSA), a serine proteinase secreted by human prostate and human prostate cancer cells, is able to convert Lys-plasminogen to biologically active angiostatin-like fragments, containing kringles 1-4, by limited proteolysis of peptide bond Glu439-Ala440 in vitro. In an in vitro morphogenesis assay, the purified angiostatin-like fragments inhibited proliferation and tubular formation of human umbilical vein endothelial cells with the same efficacy as angiostatin. This finding might help to understand growth characteristics of prostate cancer, which usually has low microvessel density and slow proliferation.     

A multiprong approach to cancer gene therapy by coencapsulated cells

Immune-isolation of nonautologous cells with microencapsulation protects these cells from graft rejection, thus allowing the same recombinant therapeutic cell line to be implanted in different recipients. This approach was successful in treating HER2/neu-expressing tumors in mice by delivering an interleukin-2 fusion protein (sFvIL-2), or angiostatin. However, treatment with interleukin-2 led to profuse inflammation, while angiostatin delivery did not result in long-term tumor suppression, in part due to endothelial cell-independent neovascularization (vascular mimicry). We hypothesize that coencapsulating the two producer cells in the same microcapsules may enhance the efficacy and ameliorate the above side effects. Hence, B16-F0/neu tumor-bearing mice were implanted with sFvIL-2- and angiostatin-secreting cells coencapsulated in the same alginate-poly-L-lysine-alginate microcapsules. However, this protocol only produced an incremental but not synergistic improvement, as measured with greater tumor suppression and improved survival. Compared to the single sFvIL-2 treatment, the coencapsulation protocol showed improved efficacy associated with: mobilization of sFvIL-2 from the spleen; a higher level of cytokine delivery systemically and to the tumors; increased tumor and tumor-associated endothelial cell apoptosis; and a reduced host inflammatory response. However, compared to the single angiostatin treatment, the efficacy was reduced, primarily due to a "bystander" effect in which the angiostatin-secreting cells suffered similar transgene silencing as the coencapsulated cytokine-secreting cells. Nevertheless, the level of "vascular mimicry" of the single angiostatin treatment was significantly reduced. Hence, while there was no synergy in efficacy, an incremental improvement and some reduction in undesirable side effects of inflammation and vascular mimicry were achieved over the single treatments.     

血管生长抑制因子angiostatin在昆虫细胞中的表达及活性研究

背景与目的:抑制新生血管的形成,有助于抑制肿瘤的生长,减少和预防肿瘤转移的发生。血管抑素(angiostatin)是一种重要的内源性新生血管生成抑制剂,对血管内皮细胞增殖有较强的抑制作用。为获得具有高活性的Angiostatin表达,本研究通过杆状病毒表达系统表达重组的angiostatin,分析其在昆虫细胞中表达和生物活性。方法:用带有angiostatin的杆状病毒转移载体pBlueBacHis2B和病毒DNA共同转染Sf9细胞,构建重组病毒,蚀斑实验筛选,PCR分析确定后扩增产生大量高滴度的病毒贮存液;用SDS-PAGE电泳和Westernblot对感染不同时间后分泌的重组蛋白做时间表达分析;用ProBondTM纯化系统对表达的重组angiostatin进行纯化,分光光度计确定蛋白含量,SDS-PAGE电泳确定蛋白纯度;采用MTT法测定重组蛋白angiostatin对原代培养的人脐静脉内皮细胞(HUVEC)的抑制作用而后通过鸡胚尿囊膜实验进一步证实其抗血管形成作用。结果:成功构建了滴度为2×108pfu/ml的angiostatin重组杆状病毒,并在昆虫细胞Sf9中高效表达了分子量为53ku的angiostatin重组蛋白,纯度约为90%,重组angiostatin蛋白不仅在体外显著抑制内皮细胞的生长(IC50为2.3μg/ml),而且显著抑制鸡胚尿囊膜血管的生长。结论:此系统可制备高滴度angiostatin重组杆状病毒贮存液,并在Sf9昆虫细胞中高效表达该重组蛋白,经在体和离体细胞学实验验证其对内皮细胞的增殖具有抑制作用。     

The recombinant kringle domain of urokinase plasminogen activator inhibits in vivo malignant glioma growth

In a previous report, the recombinant kringle domain (UK1) of the urokinase type plasminogen activator (uPA) showed antiangiogenic activity. Here, we investigated in vivo antitumor effects of the UK1 of human uPA employing a brain tumor model. The systemic administration of UK1 purified from pichia expression (10 and 50 mg/kg/day intraperitoneally for 25 days) led to suppress the growth of a U87 human glioma xenograft, implanted into the brains of male BALB/cSlc nude mice, by 35% and 80%, respectively. In the immunohistochemical analysis, the tumors treated with UK1 showed decreased vascularity and expression of angiogenesis-related factors including vascular endothelial growth factor (VEGF), angiogenin, alpha-smooth muscle actin, von Willebrand's factor, and CD31 (PECAM-1 [Platelet endothelial cell adhesion molecule-1]), and increased apoptosis. UKl inhibited the in vitro proliferation and tube formation of VEGF-stimulated endothelial cells but not the proliferation of glioma cells. These results suggest that UK1 inhibits the malignant glioma growth by suppression of angiogenesis.     

Angiostatin enhances B7.1-mediated cancer immunotherapy independently of effects on vascular endothelial growth factor expression.

Tumors must develop an adequate vascular network to meet their increasing demands for nutrition and oxygen. Angiostatin, a multiple kringle (1-4)-containing fragment of plasminogen, is an effective natural inhibitor of tumor angiogenesis. Here we show that gene transfer of angiostatin into small (0.1 cm in diameter) solid EL-4 lymphomas established in syngeneic C57BL/6 mice led to reduced tumor angiogenesis and weak inhibition of tumor growth. In contrast, when angiostatin gene therapy was preceded by in situ gene transfer of the T-cell costimulator B7.1, large (0.4 cm in diameter) tumors were rapidly and completely eradicated, whereas B7.1 and angiostatin monotherapies were ineffective. Combined gene transfer of B7.1 and angiostatin generated potent systemic antitumor immunity that was effective in eradicating a systemic challenge of 10(7) EL-4 cells. Gene transfer of angiostatin expression plasmids led to overexpression of angiostatin in tumors, increased apoptosis of tumor cells, and decreased density of tumor blood vessels, which may allow the immune system to overcome tumor immune resistance. The latter effects were not the result of a decrease in vascular endothelial growth factor expression, as tumoral vascular endothelial growth factor expression increased slightly after angiostatin gene transfer, presumably in response to increasing hypoxia. These results suggest that combining immunogene therapy with a vascular attack by angiostatin is a particularly effective approach for eliciting antitumor immunity.     

Recombinant adeno-associated virus 2-mediated antiangiogenic prevention in a mouse model of intraperitoneal ovarian cancer.

PURPOSE: In the present study, we sought to determine the potential of sustained transgene expression by a single i.m. administration of recombinant adeno-associated virus 2 (rAAV) encoding angiostatin and endostatin in inhibiting i.p. ovarian cancer growth and dissemination in a preclinical mouse model. EXPERIMENTAL DESIGN: Cohorts of female athymic nude mice received either no virus or 1.2 x 10(11) particles of rAAV encoding green fluorescence protein or endostatin plus angiostatin, i.m. Three weeks later, the mice were i.p. injected with 10(6) human epithelial ovarian cancer cell line SKOV3.ip1. As a measure of effectiveness of the therapy, tumor weight, abdominal distension, ascites volume and vascular endothelial growth factor level, and tumor weight were determined. Immunohistochemistry was done to determine tumor cell apoptosis and endothelial cell proliferation following the therapy. Tumor-free survival was recorded as the end point. RESULTS: Results indicated a significant tumor-free survival (P < 0.003) following therapy with rAAV encoding endostatin and angiostatin compared with untreated or rAAV-green fluorescence protein-treated mice. Ascites volume in rAAV endostatin and angiostatin-treated mice was significantly lower than naive mice and contained less hemorrhage and tumor conglomerates. The level of vascular endothelial growth factor in the ascites of antiangiogenic vector treated mice was also significantly less compared with the untreated mice. Immunohistochemical analyses indicated increased tumor cell apoptosis and decreased blood vasculature following rAAV endostatin and angiostatin treatment. CONCLUSION: The results indicate that antiangiogenic genetic prevention from stable systemic levels of angiostatin and endostatin by i.m. administration of rAAV can be used for the treatment of i.p. ovarian cancer growth and dissemination.     

Effects of angiostatin gene transfer on functional properties and in vivo growth of Kaposi's sarcoma cells.

Gene transfer delivery of endogenous angiogenesis inhibitors such as angiostatin would circumvent problems associated with long-term administration of proteins. Kaposi's sarcoma (KS), a highly vascular neoplasm, is an excellent model for studying tumor angiogenesis and antiangiogenic agent efficacy. We investigated the effects of angiostatin gene transfer in in vitro and in vivo models of KS-induced neovascularization and tumor growth. A eukaryotic expression plasmid and a Moloney leukemia virus-based retroviral vector for expression of murine angiostatin were generated harboring the angiostatin cDNA with cleavable leader signals under the control of either the strong cytomegalovirus promoter/enhancer or the Moloney leukemia virus long terminal repeat. Angiostatin secretion was confirmed by radioimmunoprecipitation and Western blot analysis. Supernatants of angiostatin-transfected cells inhibited endothelial cell migration in vitro. Stable gene transfer of the angiostatin cDNA by retroviral vectors in KS-IMM cells resulted in sustained angiostatin expression and delayed tumor growth in nude mice, which was associated with reduced vascularization. These findings suggest that gene therapy with angiostatin might be useful for treatment of KS and possibly other highly angiogenic tumors.     

血管抑素联合顺铂治疗Lewis肺癌

目的探讨血管抑素联合顺铂对内皮细胞增殖和Lewis肺癌生长抑制作用.方法将内皮细胞接种到96孔板中,加入不同试药72 h后,作MTT检测每孔中的细胞数.将Lewis肺癌细胞接种到C57小鼠右腋下,随机分为4组,分别用不同试药处理.每2日测量瘤体积,20天后处死动物,称取瘤重,常规病理和免疫组织化学染色检查,观察微血管密度和血管内皮细胞生长因子表达情况.结果顺铂与血管抑素在抑制血管内皮细胞增殖方面具有协同作用.顺铂组和顺铂 血管抑素组瘤体积、瘤重和血管密度均明显＜对照组.其中以顺铂与血管抑素在同时应用时瘤体积与瘤重又明显低于顺铂组.结论血管抑素与顺铂同时使用对lewis肺癌生长的抑制作用优于先后使用.     

Effects of sustained antiangiogenic therapy in multistage prostate cancer in TRAMP model

Antiangiogenic therapy is a promising alternative for prostate cancer growth and metastasis and holds great promise as an adjuvant therapy. The present study evaluated the potential of stable expression of angiostatin and endostatin before the onset of neoplasia and during the early and late stages of prostate cancer progression in transgenic adenocarcinoma of mouse prostate (TRAMP) mice. Groups of 5-, 10-, and 18-week-old male TRAMP mice received recombinant adeno-associated virus-6 encoding mouse endostatin plus angiostatin (E+A) by i.m. injection. The effects of therapy were determined by sacrificing groups of treated mice at defined stages of tumor progression and following cohorts of similarly treated mice for long-term survival. Results indicated remarkable survival after recombinant adeno-associated virus-(E+A) therapy only when the treatment was given at an earlier time, before the onset of high-grade neoplasia, compared with treatment given for invasive cancer. Interestingly, early-stage antiangiogenic therapy arrested the progression of moderately differentiated carcinoma to poorly differentiated state and distant metastasis. Immunohistochemical analysis of the prostate from treated mice indicated significantly lower endothelial cell proliferation and increased tumor cell apoptosis. Vascular endothelial growth factor receptor (VEGFR)-2 expression was significantly down-regulated in tumor endothelium after treatment but not VEGFR-1. Analysis of the neuroendocrine marker synaptophysin expression indicated that antiangiogenic therapy given at an early-stage disease reduced neuroendocrine transition of the epithelial tumors. These studies indicate that stable endostatin and angiostatin gene therapy may be more effective for minimally invasive tumors rather than advanced-stage disease.     

Inhibition of B16BL6 tumor progression by coadministration of recombinant angiostatin K1-3 and endostatin genes with cationic liposomes

Transfection of the antiangiogenic angiostatin and endostatin genes was shown to be an alternative to high-dose administration of angiostatin or endostatin proteins for cancer therapy. We have systematically investigated whether coadministration of the mouse angiostatin kringle 1-3 gene (pFLAG-AngioK1/3) and the endostatin gene (pFLAG-Endo) complexed with cationic liposomes exhibits enhanced therapeutic efficacy. In vitro, the coexpressed mixture of angiostatin K1-3 and endostatin more effectively reduced angiogenesis in chorioallantoic membranes than either angiostatin K1-3 or endostatin alone. In vivo, subcutaneous co-administration of pFLAG-AngioK1/3 and pFLAG-Endo lipoplexes more effectively inhibited vascularization in Matrigel plugs implanted in mice than either one alone. Additionally, subcutaneous administration of these genes inhibited the growth and formation of pulmonary metastases of B16BL6 melanoma cells in mice. Compared to treatment with an empty vector, treatment with pFLAG-AngioK1/3 plus pFLAG-Endo inhibited 81% of tumor growth, while treatment with pFLAG-AngioK1/3 or pFLAG-Endo inhibited tumor growth 70 and 69%, respectively. Cotreatment with the two plasmids after primary tumor excision induced a 90% inhibition of pulmonary metastases versus 79% for pFLAG-AngioK1/3 or 80% for pFLAG-Endo individually. These results suggest that combined administration of angiostatin K1-3 and endostatin genes complexed with cationic liposomes may be an innovated antiangiogenic strategy for cancer therapy.     

重组人血管抑素的克隆、表达及活性测定

目的：研究血管抑素（ａｎｇｉｏｓｔａｔｉｎ）的临床应用价值,将其开发为多肽类药物。方法：ＲＴ－ＰＣＲ从胎儿肝脏钓取人血管抑素全编码区ｃＤＮＡ,使用Ｐｉｃｈｉａ分泌型酵母表达系统表达重组人血管抑素,重组蛋白经肝素亲和层析纯化后,以鸡胚尿囊膜法血管生成实验及小鼠创伤愈合实验检测活性。结果：重组人血管抑素在酵母系统中得到较高量表达（５ｍｇ／Ｌ）,经肝素亲和层析纯化,ＳＤＳ－ＰＡＧＥ显示分子量为４３ｋＤ。活性实验表明,重组蛋白能够抑制新生管形成、抑制伤口愈合。结论：重组人血管抑素在酵母系统中实现高效表达,并具有很好的生物学活性。     

Angiostatin gene therapy inhibits the growth of murine squamous cell carcinoma in vivo

Tumor growth is an angiogenesis-dependent process and therapeutic strategies aimed at inhibiting angiogenesis are theoretically attractive. Angiostatin has been shown to potently inhibit endothelial proliferation in vitro and tumor growth in vivo. We now show that a shift in the balance of tumor angiogenesis by gene transfer of a cDNA coding for mouse angiostatin into mouse squamous cell carcinoma NRS-1 and SCC-VII cells suppresses tumor growth in vivo. The inhibition of an angiostatin-transfected tumor was accompanied by a marked reduction in vascularity and the presence of many apoptotic tumor cells. However, transfected-angiostatin cDNA does not affect the expression of the vascular endothelial growth factor (VEGF) and VEGF-R2 in the vascular endothelium. The inhibition mechanisms of neovascularization may be mediated independent of VEGF:VEGF-R2 complex. Our data may provide a useful approach for human oral cancer therapy by gene therapy with angiostatin.     

Antivascular endothelial growth factor receptor (fetal liver kinase 1) monoclonal antibody inhibits tumor angiogenesis and growth of several mouse and human tumors.

Tumor angiogenesis is mediated by tumor-secreted angiogenic growth factors that interact with their surface receptors expressed on endothelial cells. Vascular endothelial growth factor (VEGF) and its receptor [fetal liver kinase 1 (Flk-1)/kinase insert domain-containing receptor] play an important role in vascular permeability and tumor angiogenesis. Previously, we reported on the development of anti-Flk-1 and antikinase insert domain-containing receptor monoclonal antibodies (mAbs) that potently inhibit VEGF binding and receptor signaling. Here, we report the effect of anti-Flk-1 mAb (DC101) on angiogenesis and tumor growth. Angiogenesis in vivo was examined using a growth factor supplemented (basic fibroblast growth factor + VEGF) Matrigel plug and an alginate-encapsulated tumor cell (Lewis lung) assay in C57BL/6 mice. Systemic administration of DC101 every 3 days markedly reduced neovascularization of Matrigel plugs and tumor-containing alginate beads in a dose-dependent fashion. Histological analysis of Matrigel plugs showed reduced numbers of endothelial cells and vessel structures. Several mouse tumors and human tumor xenografts in athymic mice were used to examine the effect of anti-Flk-1 mAb treatment on tumor angiogenesis and growth. Anti-Flk-1 mAb treatment significantly suppressed the growth of primary murine Lewis lung, 4T1 mammary, and B16 melanoma tumors and growth of Lewis lung metastases. DC101 also completely inhibited the growth of established epidermoid, glioblastoma, pancreatic, and renal human tumor xenografts. Histological examination of anti-Flk-1 mAb-treated tumors showed evidence of decreased microvessel density, tumor cell apoptosis, decreased tumor cell proliferation, and extensive tumor necrosis. These findings support the conclusion that anti-Flk-1 mAb treatment inhibits tumor growth by suppression of tumor-induced neovascularization and demonstrate the potential for therapeutic application of anti-VEGF receptor antibody in the treatment of angiogenesis-dependent tumors.     

Growth of human melanoma xenografts is suppressed by systemic angiostatin gene therapy

The effect of local and systemic delivery of the angiostatin gene on human melanoma growth was studied in nude mice. Liposome-coated plasmids carrying the cDNA coding for murine and human angiostatin (CMVang and BSHang) were injected weekly, locally or systemically, in mice transplanted with melanoma cells. The treatment reduced melanoma growth by 50% to 90% compared to that occurring in control animals treated with liposome-coated plasmid carrying the lacZ gene or in untreated controls. The growth of both locally injected and controlateral uninjected tumors in mice bearing two melanoma grafts was significantly suppressed after intratumoral treatment. Tumor growth inhibition was also observed in mice treated by intraperitoneal delivery, suggesting that angiostatin gene therapy acts through a systemic effect. Both melanoma growth suppression and delay in the onset of tumor growth were observed in treated mice. PCR performed on tumors and normal tissues showed that the lipofected DNA was present in tissues from treated mice, and angiostatin expression was demonstrated by RT-PCR. Histopathological analysis of melanoma nodules revealed an increase in apoptotic cells and a reduction in vessel density in tumors from treated mice. Our results suggest that systemic, liposome-mediated administration of genes coding for antiangiogenic factors represents a promising strategy for melanoma treatment in humans.