Although the systemic administration of a number of different gene products has been shown to result in the inhibition of angiogenesis and tumor growth in different animal tumor models, the relative potency of those gene products has not been studied rigorously. To address this issue, recombinant adenoviruses encoding angiostatin, endostatin, and the ligand-binding ectodomains of the vascular endothelial growth factor receptors Flk1, Flt1, and neuropilin were generated and used to systemically deliver the different gene products in several different preexisting murine tumor models. Single i.v. injections of viruses encoding soluble forms of Flk1 or Flt1 resulted in Ϸ80% inhibition of preexisting tumor growth in murine models involving both murine (Lewis lung carcinoma, T241 fibrosarcoma) and human (BxPC3 pancreatic carcinoma) tumors. In contrast, adenoviruses encoding angiostatin, endostatin, or neuropilin were significantly less effective. A strong correlation was observed between the effects of the different viruses on tumor growth and the activity of the viruses in the inhibition of corneal micropocket angiogenesis. These data underscore the need for comparative analyses of different therapeutic approaches that target tumor angiogenesis and provide a rationale for the selection of specific antiangiogenic gene products as lead candidates for use in gene therapy approaches aimed at the treatment of malignant and ocular disorders.

Collagen XVIII (c18) is a triple helical endothelial/epithelial basement membrane protein whose noncollagenous (NC)1 region trimerizes a COOH-terminal endostatin (ES) domain conserved in vertebrates, Caenorhabditis elegans and Drosophila. Here, the c18 NC1 domain functioned as a motility-inducing factor regulating the extracellular matrix (ECM)-dependent morphogenesis of endothelial and other cell types. This motogenic activity required ES domain oligomerization, was dependent on rac, cdc42, and mitogen-activated protein kinase, and exhibited functional distinction from the archetypal motogenic scatter factors hepatocyte growth factor and macrophage stimulatory protein. The motility-inducing and mitogen-activated protein kinase–stimulating activities of c18 NC1 were blocked by its physiologic cleavage product ES monomer, consistent with a proteolysis-dependent negative feedback mechanism. These data indicate that the collagen XVIII NC1 region encodes a motogen strictly requiring ES domain oligomerization and suggest a previously unsuspected mechanism for ECM regulation of motility and morphogenesis.

Neuroblastoma (NB) is a rapidly growing, wellvascularized childhood cancer that often presents with metastases. The overall five-year survival in NB is approximately 45% despite multimodality treatment, and therefore there is a clinical need for new therapeutic strategies. NB frequently overexpresses the angiogenic factor VEGF (vascular endothelial growth factor). The aim of this study was to investigate the effect of bevacizumab (Avastin®, Genentech/Roche), a humanized anti-VEGF-A antibody, on NB growth in three different xenograft models, chosen to resemble high-risk NB. The human NB cell lines SK-N-AS, IMR-32 and SH-SY5Y, which are poorly differentiated and overexpress VEGF-A, were injected s.c. in immunodeficient mice. Bevacizumab was given intraperitoneally twice weekly at 5 mg/kg body weight, starting at a tumor volume of 0.3 mL. Bevacizumab significantly (p Ͻ 0.01-0.05) reduced NB growth in vivo without toxicity by causing a 30 -63% reduction of angiogenesis, but had no effect on NB cell survival in vitro. Serum concentrations of VEGF-A increased two-to six-fold during bevacizumab therapy which did not result in faster tumor growth compared with control animals. Based on our experimental data we suggest consideration of bevacizumab in treatment of highrisk NB that does not respond to conventional therapy and that overexpresses VEGF. (Pediatr Res 60: 576-581, 2006)