Pineau et al. [55] showed that miR-221 overexpression promoted the growth of tumorigenic murine hepatic progenitor cells using a mouse HCC model, and that miR-221 could induce the tumor growth via suppressing p27 and/or DDIT4 (DNA damage-inducible transcript 4) expression. Here, DDIT4 is linked to hepatocellular carcinoma.