Inhibiting Glutamine-Dependent mTORC1 Activation Ameliorates Liver Cancers Driven by β-Catenin Mutations

Based on their lobule location, hepatocytes display differential gene expression, including pericentral hepatocytes that surround the central vein, which are marked by Wnt-b-catenin signaling. Activating b-catenin mutations occur in a variety of liver tumors, including hepatocellular carcinoma (HCC), but no specific therapies are available to treat these tumor subsets. Here, we identify a positive relationship be- tween b-catenin activation, its transcriptional target glutamine synthetase (GS), and p-mTOR-S2448, an indicator of mTORC1 activation. In normal livers of mice and humans, pericentral hepatocytes were simultaneously GS and p-mTOR-S2448 positive, as were b-catenin-mutated liver tumors. Genetic disruption of b-catenin signaling or GS prevented p-mTOR-S2448 expression, while its forced expres- sion in b-catenin-deficient livers led to ectopic p-mTOR-S2448 expression. Further, we found notable therapeutic benefit of mTORC1 inhibition in mutant-b-catenin-driven HCC through suppression of cell proliferation and survival. Thus, mTORC1 in- hibitors could be highly relevant in the treatment of liver tumors that are b-catenin mutated and GS positive.