EZH2 and cholangiocarcinoma: After endothelial cells receive extracellular vesicles (mainly exosomes) carrying circ-CCAC1 released by cholangiocarcinoma cells, circ-CCAC1 can bind to EZH2 in endothelial cells and prevent the nuclear translocation of EZH2, weakening EZH2-mediated H3K27me3 modification of SG3GL2 promoter region.