FIS1 and hepatocellular carcinoma: Mechanistically, circFOXK2 exhibits protein-encoding (encodes the FOXK2-142aa protein to regulate the phosphorylation of LDHA) and miRNA sponging [binds to miR-484 to relieve silencing of mitochondrial adaptor fission 1 (Fis1)] roles to enhance the Warburg effect in HCC cells.