Fig. 3

Exo-circRNAs play a crucial role via their sponging function and can be secreted into body fluid in tumors. a In malignant L-02 cells, circRNA-100284 can bind to miR-217, which gives rise to EZH2 and contributes to the abnormal proliferation of liver cells. EZH2 can be transported to other cells and influence their biological behavior. b Circ-DB from exosomes functions by downregulating expression of miR-34a and upregulating level of both USP7 and cyclin A2. Then the growth of HCC is accelerated. c The ciRS-133/miR-133/PRDM16 signaling pathway is important for differentiation of preadipocytes. The ciRS-133 can upregulate level of PRDM by reducing miR-133 and promote the differentiation process. d It has been proven that there is exosome-mediated circRNAs communication in pancreatic ductal adenocarcinoma (PDAC). Circ-PDE8A shows high expression in PDAC, and this molecule can act as a miR-338 sponge and promote the expression of the cancer-related genes MACC1 and MET. e The epithelial-mesenchymal transition (EMT) is a crucial process in carcinoma. Exo-circPRMT5 is reported to show a remarkable increase in serum and urine samples from patients who have urothelial carcinoma of the bladder (UCB). CircPRMT5 could promote UCB cell EMT by acting as a miR-30c sponge, and the downstream genes SNAIL1 and E-cadherin would be enhanced to promote cell invasiveness