HDAC1 and hepatocellular carcinoma: HDAC1 has been established as directly regulated by mTORC1 signaling through mTOR-S6K1 axis (54) and we also found a positive correlation between mTOR signaling score and HDAC1 activity score (Figure 4L and Figure S5A) and between protein expression of S6K1 and HDAC1 activity score (Figure S5B) in HCC tumors.