In the present study, we found that mTORC1 is activated in human HB cell lines as well as YAP/β-catenin-induced mouse HB tissues. A key role of mTORC1 in HB development was substantiated by subsequent functional studies. Mechanistically, we found that YAP induces the expression of the amino acid transporter SLC38A1, leading to the activation of mTORC1. Therefore, our study strongly suggests that mTORC1 is a major signaling event downstream of activated YAP along HB development. The results obtained also support the further testing of mTOR inhibitors for the treatment of human HB.