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.

Growth factor supplemented matrigel improves ectopic skeletal muscle formation--a cell therapy approach

Following damage to skeletal muscle, satellite cells become activated, migrate towards the injured area, proliferate, and fuse with each other to form myotubes which finally mature into myofibers. We tested a new approach to muscle regeneration by incorporating myoblasts, with or without the exogenous growth factors bFGF or HGF, into three-dimensional gels of reconstituted basement membrane (matrigel). In vitro, bFGF and HGF induced C2C12 myoblast proliferation and migration and were synergistic when used together. In vivo, C2C12 or primary i28 myoblasts were injected subcutaneously together with matrigel and growth factors in the flanks of nude mice. The inclusion of either bFGF or HGF increased the vascularization of the gels. Gels supplemented with bFGF showed myogenesis accompanied by massive mesenchymal cell recruitment and poor organization of the fascicles. Samples containing HGF showed delayed differentiation with respect to controls or bFGF, with increased myoblast proliferation and a significantly higher numbers of cells in myotubes at later time points. HGF samples showed limited mesenchymal cell infiltration and relatively good organization of fascicles. The use of both bFGF and HGF together showed increased numbers of nuclei in myotubes, but with bFGF-mediated fibroblast recruitment dominating. These studies suggest that an appropriate combination of basement membrane components and growth factors could represent a possible approach to enhance survival dispersion, proliferation, and differentiation of myogenic cells during muscle regeneration and/or myoblast transplantation. This model will help develop cell therapy of muscle diseases and open the future to gene therapy approaches.