MiR-34a Targeting of Notch Ligand Delta-Like 1 ImpairsCD15+/CD133+ Tumor-Propagating Cells and SupportsNeural Differentiation in

In a screening of potential targets within Notch signaling, miR-34a was seen to be a regulator of the Notch pathway through its targeting of Notch ligand Delta-like 1 (Dll1). Down-regulation of Dll1 expression by miR-34a negatively regulates cell proliferation, and induces apoptosis and neural differentiation in MB cells. MiR-34a expression negatively affects CD133+/CD15+ tumor-propagating cells. Adenoviruses carrying the precursor miR-34a induce neurogenesis of tumor spheres derived from a genetic animal model of MB (Patch1+/- p53-/-), thus providing further evidence that the miR-34a/Dll1 axis controls both autonomous and non autonomous signaling of Notch. In vivo, miR-34a overexpression carried by adenoviruses reduces tumor burden in cerebellum xenografts of athymic mice, thus demonstrating an anti-tumorigenic role of miR-34a in vivo.