High-grade bladder cancer cells secrete extracellular vesicles containing miRNA-146a-5p and promotes angiogenesis

Recurrence is one of the major issues in bladder cancer (BCa). Novel technologies, such as the detection of microRNAs carried by extracellular vesicles (EVs) in urine, have been proposed as biomarkers for detecting recurrence in BCa. Although the usefulness of microRNAs in body fluids from cancer patients has been reported, it is also known that they play essential roles in cancer progression. We previously proposed miR-146a-5p as a prognostic marker in BCa, since its urinary expression was associated with grade and tumour depth. However, the specific mechanisms of miR-146a-5p remain unclear. Here, we show the proangiogenic effects of miR-146a-5p secreted by high-grade BCa cells. The urinary miR-146a-5p level was higher in patients with high-grade BCa than in those with low-grade BCa. Similarly, tumours generated by miR-146a-overexpressing BCa cells in mice grew rapidly with high levels of angiogenesis. BCa-derived EV treatment promoted the proliferation of endothelial cells via the inhibition of the demethylase TET2 and the subsequent increase in its downstream target c-Myc. These findings demonstrate that secreted miR-146a-5p contributes to cancer progression by promoting angiogenesis. Therefore, miRNAs in EVs may become not only a diagnostic tool but also a target molecule for therapy.