E1A gene therapy inhibits angiogenesis in a Ewing's sarcoma animal model

We assessed vascular endothelial growth factor (VEGF) expression in four different human Ewing's sarcoma cell lines (TC71, SK-ES, RD, and A4573) and in tumors in nude mice induced following s.c. injection of TC71 cells. Three of the four cell lines (TC71, SK-ES, and A4573) expressed significantly higher levels of VEGF than did normal human osteoblasts. Transfection of the adenovirus type 5 early region 1A (E1A) gene into TC71 cells down-regulated VEGF expression in vitro. In the mice bearing TC71 cell tumors, intratumoral injections of an adenoviral vector containing the E1A gene (Ad-E1A) decreased VEGF expression, inhibited tumor growth, and increased the survival rates in comparison with the mice given injections of PBS or an adenoviral vector containing β-galactosidase (Ad-β-gal). E1A gene therapy also significantly reduced blood vessel density and induced cell apoptosis in the tumors. These results demonstrate that E1A gene therapy inhibits angiogenesis, most likely by suppression of VEGF expression. Thus, E1A gene therapy may be a new therapeutic approach for Ewing's sarcoma.