Interestingly, circGPR137B acted as a sponge for miR-4739 to up-regulate its target FTO, which mediated m6A demethylation of circGPR137B and promoted its expression, thus finally forming a feedback loop comprising circGPR137B/miR-4739/FTO axis and affecting the hepatocellular carcinoma cells [101]. Here, FTO is linked to hepatocellular carcinoma.