Enriched in HCC cell-derived exosomes characterized by high metastatic potential, circPTGR1 can upregulate MET proto-oncogene (MET) by competitively binding miR-449a, activating the metastatic activity of HCC cells with low or no metastatic potential, thereby destroying the tumor microenvironment homeostasis and promoting the invasion and metastasis of HCC cells (42). Here, MET is linked to neoplasm.