TSC/mTORC1 mediates mTORC2/AKT1 signaling in c-MYC-induced murine hepatocarcinogenesis via centromere protein M.

Abstract

Activated mTORC2/AKT signaling plays a role in hepatocellular carcinoma (HCC). Research has shown that TSC/mTORC1 and FOXO1 are distinct downstream effectors of AKT signaling in liver regeneration and metabolism. However, the mechanisms by which these pathways mediate mTORC2/AKT activation in HCC are not yet fully understood. Amplification and activation of c-MYC is a key molecular event in HCC. In this study, we explored the roles of TSC/mTORC1 and FOXO1 as downstream effectors of mTORC2/AKT1 in c-MYC-induced hepatocarcinogenesis. Using various genetic approaches in mice, we found that manipulating the FOXO pathway had minimal impact on c-MYC-induced HCC. In contrast, loss of mTORC2 inhibited c-MYC-induced HCC, an effect that was completely reversed by ablating TSC2, which activated mTORC1. Additionally, we discovered that p70/RPS6 and 4EBP1/eIF4E act downstream of mTORC1, regulating distinct molecular pathways. Notably, the 4EBP1/eIF4E cascade is crucial for cell proliferation and glycolysis in c-MYC-induced HCC. We also identified centromere protein M (CENPM) as a downstream target of the TSC2/mTORC1 pathway in c-MYC-driven hepatocarcinogenesis, and its ablation entirely inhibited c-MYC-dependent HCC formation. Our findings demonstrate that the TSC/mTORC1/CENPM pathway, rather than the FOXO cascade, is the primary signaling pathway regulating c-MYC-driven hepatocarcinogenesis. Targeting CENPM holds therapeutic potential for treating c-MYC-driven HCC.