Huang et al. discovered that circRNA-100338 is highly abundant in exosomes of HCC cells with high metastatic potential, and the mechanism is that it can promote the proliferation of human umbilical vein endothelial cells (HUVECs) and regulates angiogenesis by interacting with neuro-oncological ventral antigen 2 (NOVA2), an RNA-binding protein associated with vascular development and lumen formation. Here, NOVA2 is linked to hepatocellular carcinoma.