MicroRNA-519c suppresses hypoxia-inducible factor-1alpha expression and tumor angiogenesis

Hypoxia-inducible factor-1alpha (HIF-1alpha) is widely considered to be one of the key regulators of tumor angiogenesis. The upstream regulation is complex and involves several growth factors, cytokines, and hypoxia. Herein, we have identified miR-519c as a hypoxia-independent regulator of HIF-1alpha, acting through direct binding to the HIF-1alpha 3' untranslated region and leading to reduced tumor angiogenesis. Overexpression of miR-519c resulted in a significant decrease of HIF-1alpha protein levels and reduced the tube formation of human umbilical vein endothelial cells; similarly, antagomir inhibition of miR-519c increased the level of HIF-1alpha protein and enhanced angiogenic activity, suggesting an important role of miR-519c in HIF-1alpha-mediated angiogenesis. Consistent with the overexpression of miR-519c in cancer patients with better prognosis, mice injected with miR-519c-overexpressing cells exhibited dramatically reduced HIF-1alpha levels, followed by suppressed tumor angiogenesis, growth, and metastasis. In addition, we found that hepatocyte growth factor (HGF), a known HIF-1alpha inducer, reduced the miR-519c levels through an Akt-dependent pathway. This regulation was posttranscriptional and may be mediated by suppression of miR-519c maturation. Taken together, our findings provide the first evidence that miR-519c is a pivotal regulator of tumor angiogenesis and that microenvironmental HGF contributes to regulating miR-519c biogenesis in cancer cells.