Adenoviral vector expressing murine angiostatin inhibits a model of breastcancer metastatic growth in the lungs of mice

Angiostatin, an internal fragment of plasminogen, has been shown to inhibit the process of angiogenesis or neovascularization. In this study, we have expressed the cDNA for murine angiostatin under the control of the human cy tomegalovirus promoter from a human type-5 adenovirus and shown that this v ector produces a protein which retains biological activity. Angiostatin exp ression was determined by Northern blot analysis and Western immunoblotting . Ad-angiostatin, but not a control vector Ad-d170, significantly reduced t he viability of infected human umbilical cord vein endothelial cells (HUVEC ) in vitro. In an in vivo model of basic fibroblast growth factor-induced a ngiogenesis, Ad-angiostatin (1 x 10(9) pfu) could inhibit endothelial cell migration and the formation of capillaries within a Matrigel plug which had been implanted for one week subcutaneously into C57BL/6 mice. Endothelial cells in these plugs had an altered, rounded, phenotype with dark picnotic nuclei indicative of apoptosis, which was confirmed using transmission elec tron microscopy. in contrast, endothelial cells from bFGF alone or in combi nation with the control vector-treated plugs retained the long spindle shap e characteristic of endothelial cells. Intranasal delivery of Ad-angiostati n into the lungs of FVB/n mice demonstrated comparable cellular infiltratio n in the recovered bronchoalveolar lavage fluid with no signs of abnormal p athology as compared to PBS or control vector-treated animals. in a pulmona ry metastatic breast cancer model, the delivery of Ad-angiostatin (1 x 10(9 ) pfu) to the lung significantly delayed tumor growth as measured by the nu mber of visible surface tumor nodules. This study has demonstrated that the specific targeting of tumors to inhibit angiogenesis using an adenovirus e xpressing angiostatin, may deliver localized concentrations of protein havi ng a greater impact on inhibition of tumor growth.