Although previous studies have indicated that RB levels determine the sensitivity to CDK4/6 inhibition (Dean et al., 2010; Konecny et al., 2011; Logan et al., 2013; Michaud et al., 2010), we and others have observed some activity of palbociclib that is independent of RB levels in HCC cells. Here, CDK4 is linked to hepatocellular carcinoma.