MicroRNAs regulate tumor angiogenesis modulated by endothelial progenitor cells

Bone marrow (BM)-derived endothelial progenitor cells (EPCs), contribute to the angiogenesis dependent growth of tumors in mice and humans. EPCs regulate the angiogenic switch via paracrine secretion of proangiogenic growth factors, and by direct luminal incorporation into sprouting nascent vessels. MicroRNAs (miRNAs) have emerged as key regulators of several cellular processes including angiogenesis; however, whether miRNAs contribute to BM-mediated angiogenesis has remained unknown. Here, we show that genetic ablation of microRNA processing enzyme Dicer, specifically in the BM, decreased the number of circulating EPCs, resulting in angiogenesis suppression and impaired tumor growth. Furthermore, genome-wide deep sequencing of small RNAs revealed tumor EPC-intrinsic miRNAs including miR-10b and miR-196b; which have been previously identified as key regulators of HOX signaling and adult stem cell differentiation. Notably, we found that both miR-10b and miR-196b, are responsive to vascular endothelial growth factor (VEGF) stimulation, and show elevated expression in human high-grade breast tumor vasculature. Strikingly, targeting miR-10b and miR-196b led to significant defects in angiogenesis-mediated tumor growth in mice. Targeting these miRNAs may constitute a novel strategy for inhibiting tumor angiogenesis