sentence: For example , Adp53 infection markedly inhibits the expression of an angiogenic factor , vascular endothelial growth factor , and increases the expression of an antiangiogenic factor , brain-specific angiogenesis inhibitor 1 , resulting in reduced neovascularization and tumor growth of adjacent nontransduced cells in vivo.34 Immunological mechanisms involving natural killer cells play an important role in the bystander effect involving Adp53 gene therapy for ovarian cancer .