ABSTRACT
Vascular endothelial growth factor (VEGF) expression is elevated in a wide variety of solid tumours. Inhibition of VEGF activities is able to reduce angiogenesis and tumour growth. We have recently shown in vitro that carboxymethyl dextran benzylamide (CMDB7) prevents the binding of VEGF(165) to its cell surface receptors and thus inhibits VEGF activities on endothelial cells. In the present study, we explored the effects of CMDB7 on highly aggressive human epidermoid carcinoma A431 cells known to overexpress epidermal growth factor receptors (EGFRs) and produce a high amount of VEGF and a minor quantity of bFGF. In vitro, CMDB7 blocked the mitogenic activity of A431-conditioned medium on endothelial cells. Concerning A431 cells, CMDB7 inhibited their proliferation and the VEGF(165) binding to them. In vivo, administration of CMDB7 (10 mg kg(-1)) three times per week for 2 weeks inhibited the growth of A431 xenografts in nude mice by 73% as compared to the control group. Immunostaining of endothelial cells with mouse-specific GSL-1 lectin in tumour sections revealed that CMDB7 also inhibited the density of intratumour endothelial cells by 66%. These findings demonstrate that CMDB7 has an efficient antiangiogenic and antitumour action in vivo even when tumour cells produce a high level of VEGF and EGFRs.
Subject(s)
Carcinoma, Squamous Cell/pathology , Dextrans/pharmacology , Endothelial Growth Factors/pharmacology , Intercellular Signaling Peptides and Proteins/pharmacology , Lymphokines/pharmacology , Neovascularization, Pathologic , Animals , Humans , Mice , Mice, Nude , Transplantation, Heterologous , Tumor Cells, Cultured , Vascular Endothelial Growth Factor A , Vascular Endothelial Growth FactorsABSTRACT
We have previously shown that carboxymethyl dextran benzylamide (CMDB7), a heparin-like molecule, inhibits the growth of tumors xenografted in nude mice, angiogenesis, and metastasis by altering the binding of angiogenic growth factors, including platelet-derived growth factor, transforming growth factor beta, and fibroblast growth factor 2, to their specific receptors. In this study, we explore the effect of CMDB7 on the most specific angiogenic growth factor, vascular endothelial growth factor 165 (VEGF(165)). We demonstrate here that CMDB7 inhibits the mitogenic effect of VEGF(165) on human umbilical vein endothelial cells (HUV-ECs) by preventing the VEGF(165)-induced VEGF receptor-2 (KDR) autophosphorylation and consequently a specific intracellular signaling. In competition experiments, the binding of (125)I-VEGF(165) to HUV-ECs is inhibited by CMDB7 with an IC(50) of 2 microm. Accordingly, CMDB7 inhibits the cross-linking of (125)I-VEGF(165) to the surface of HUV-ECs, causing the disappearance of both labeled complexes, 170-180 and 240-250 kDa. We show that CMDB7 increases the electrophoretic mobility of VEGF(165), thus evidencing formation of a stable complex with this factor. Moreover, CMDB7 reduces the (125)I-VEGF(165) binding to coated heparin-albumin and prevents a heparin-induced increase in iodinated VEGF(165) binding to soluble (125)I-KDR-Fc chimera. Concerning KDR, CMDB7 has no effect on (125)I-KDR-Fc electrophoretic migration and does not affect labeled KDR-Fc binding to coated heparin-albumin. In the presence of VEGF(165), (125)I-KDR-Fc binding to heparin is enhanced, and under these conditions, CMDB7 interferes with KDR binding. These data indicate that CMDB7 effectively inhibits the VEGF(165) activities by interfering with heparin binding to VEGF(165) and VEGF(165).KDR complexes but not by direct interactions with KDR.
Subject(s)
Angiogenesis Inhibitors/metabolism , Dextrans/metabolism , Endothelial Growth Factors/antagonists & inhibitors , Endothelium, Vascular/drug effects , Heparin/metabolism , Lymphokines/antagonists & inhibitors , Receptor Protein-Tyrosine Kinases/metabolism , Receptors, Growth Factor/metabolism , Angiogenesis Inhibitors/pharmacology , Binding, Competitive , Cell Division/drug effects , Dextrans/pharmacology , Dose-Response Relationship, Drug , Endothelium, Vascular/cytology , Humans , Receptors, Vascular Endothelial Growth Factor , Umbilical Veins/cytology , Vascular Endothelial Growth Factor A , Vascular Endothelial Growth FactorsABSTRACT
We showed previously that a carboxymethyl dextran benzylamide (CMDB7) blocks angiogenesis of MDA-MB-435 carcinoma and its lung metastases in nude mice. In this study, we examined the combination effects of CMDB7 and tamoxifen (TAM) on cell proliferation, tumor growth, and angiogenesis on the MCF-7RAS cells. We showed that CMDB7 and TAM acted in a synergistic manner to inhibit the growth of MCF-7RAS cells, blocking them in G(0)/G(1) phase of the cell cycle. For 7 weeks, the CMDB7- (300 mg/kg/week) and TAM- (20 mg/kg/week) treated groups showed tumor growth inhibition of about 66% and 76%, respectively. Combined treatments with CMDB7 and TAM block the tumor development by 94% and induce a complete regression of 4 of 8 mice. Histological analysis showed markedly less neovascularization (88%) in the tumors treated with a combination of CMDB7 and TAM. This antiangiogenic activity was further demonstrated by direct inhibition of endothelial cell proliferation. Overall, this study points to the potential use of a combination of CMDB7 and TAM to inhibit tumor angiogenesis that can prevent tumor progression.
