PIK3CA and hepatocellular carcinoma: In this study, IHC analysis showed that RAS-RAF-MEK-ERK signaling was activated in 85% of human HCC with high YAP/TAZ activity, whereas PI3K-AKT signaling was active only in 23% of human HCC with high YAP/TAZ activity, suggesting that the RAS-RAF-MEK-ERK pathway is the major contributor to HCC development with YAP/TAZ activation (Supplementary Table 1).