Regulation of endothelial migration and cancer angiogenesis by microRNAs. Left, A small non-coding RNA, miR-9, expressed and secreted by cancer cells promotes endothelial migration by targeting endothelial SOCS5, an inhibitor of JAK-STAT signalling. SOCS5 suppression by miR-9 drives endothelial migration. Right, Another small non-coding RNA, miR-126, suppresses endothelial migration by targeting a set of genes in cancer cells that drive endothelial migration. These genes drive endothelial migration by activating endothelial IGF1 receptor, a promoter of endothelial migration, and inhibiting endothelial MERTK receptor, a suppressor of endothelial migration. Mertk ECD, Mertk extracellular domain.