SOS2 and hepatocellular carcinoma: Sulfarotene at 2.2 mg/kg imposed a as high as 90 % reduction in the volumes of tumor nodes that originated from PDXs with high SOS2 expression compared to only a 52 % reduction in those with low SOS2 expression, demonstrating a predominant role of SOS2 in determining the malignant behavior and the high sensitivity to sulfarotene of HCC TRCs.