MicroRNA-145 inhibits the growth, invasion, metastasis and angiogenesis of neuroblastoma cells through targeting hypoxia-inducible factor 2 alpha

Recent evidence shows that hypoxia-inducible factor 2 alpha (HIF-2 alpha) may have critical roles in the growth and progression of neuroblastoma (NB) under non-hypoxic conditions. However, the underlying mechanisms and clinical potentials of normoxic HIF-2 alpha expression in NB still remain largely unknown. In this study, HIF-2 alpha immunostaining was identified in 26/42 NB tissues, which was correlated with clinicopathological features. In subtotal 20 NB cases, microRNA-145 (miR-145) was downregulated and inversely correlated with HIF-2 alpha expression. Bioinformatics analysis revealed a putative miR-145 binding site in the 3'-untranslated region (3'-UTR) of HIF-2 alpha messenger RNA (mRNA). Overexpression or knockdown of miR-145 responsively altered both the mRNA and protein levels of HIF-2 alpha and its downstream genes, cyclin D1, matrix metalloproteinase 14 and vascular endothelial growth factor, in normoxically cultured NB cell lines SH-SY5Y and SK-N-SH. In a luciferase reporter system, miR-145 downregulated the luciferase activity of HIF-2 alpha 3'-UTR, and these effects were abolished by a mutation in the putative miR-145-binding site. Overexpression of miR-145 suppressed the growth, invasion, metastasis and angiogenesis of SH-SY5Y and SK-N-SH cells in vitro and in vivo, while restoration of HIF-2 alpha expression rescued the tumor cells from miR-145-mediated defects in these biological features. Furthermore, anti-miR-145 inhibitor rescued the HIF-2 alpha knockdown-mediated repression on the growth, migration, invasion and angiogenesis of NB cells. These data indicate that miR-145 suppresses HIF-2 alpha expression via the binding site in the 3'-UTR under normoxic conditions, thus inhibiting the aggressiveness and angiogenesis of NB.