Liu et al. found and confirmed that circ_MMP2 functions as a ceRNA to sequester miR-136-5p, and then positively regulated the expression of its host gene MMP2, which is transmitted to living cells in adjacent tissues through secreted exosomes, ultimately promoting the metastasis of hepatocellular carcinoma (HCC) [32]. Here, MMP2 is linked to hepatocellular carcinoma.