FENDRR regulates GADD45B by competitively binding miR-423-5p, which targets GADD45B. FENDRR and GADD45B are downregulated in HCC, while miR-423-5p is upregulated. FENDRR overexpression and miR-423-5p downregulation inhibit HCC proliferation, promote apoptosis, and regulate Treg-mediated immune escape. Here, GADD45B is linked to hepatocellular carcinoma.