In HCC patients with high body fat percentages, the expression of circ-DB is upregulated, and circ-DB downregulates the expression of miR-34a by acting as a miRNA sponge, thus activating USP7, which can promote tumor growth and metastasis by reducing the ubiquitination of Cyclin A2 and many other proteins68. Here, USP7 is linked to hepatocellular carcinoma.