RARB and hepatocellular carcinoma: ACR treatments on hepatoma cell lines can suppress growth through inducing of apoptosis via caspase-3 cleavage [204], inhibiting RXRα phosphorylation by suppressing Ras-MAPK pathway [196], up-regulating RARβ expression [75,205], and promoting cell cycle arrest by increasing cellular levels of p21CIP1 [205,206,207].