On the other hand, tribbles homolog 3 (TRB3), which inhibits AKT activation induced by insulin in the liver,34 was strongly up-regulated in preneoplastic foci, but suppressed in HCC. Accordingly, TRB3-AKT complexes (a marker of AKT inhibition) were elevated in preneoplastic foci and were extremely low in HCC. Because TRB3 counteracts de novo lipogenesis by stimulating degradation of ACAC through the constitutive photomorphogenic protein 1 (COP1) E3 ubiquitin ligase,35 we determined the levels of TRB3-ACAC and ACAC-COP1 complexes and the amount of ubiquitinated ACAC. TRB3-ACAC, ACAC-COP1, and ACAC ubiquitinated levels were highest in preneoplastic

selleck products foci and lowest in HCC (Supporting Fig. 12). These data imply the presence of a mechanism at least partly counteracting ACAC activity (and AKT signaling) in the preneoplastic foci that is selectively lost at the tumor stage. Furthermore, pleckstrin homology domain leucine-rich repeat protein phosphatases 1 and 2 (PHLPP1 and

PHLPP2), which control the amplitude and duration of AKT signaling by catalyzing its dephosphorylation,36 were selectively down-regulated in HCC. Furthermore, we assessed the levels of the upstream inducers of AKT, namely, the phosphoinositide 3′-kinase catalytic subunit isoforms. Noticeably, PIK3CA and PIK3CB were up-regulated only in HCC, whereas no significant differences in the levels of PIK3CD and PIK3CG were detected in rat healthy livers, preneoplastic foci, and HCC. Mounting evidence suggests a role for insulin deregulation in human hepatocarcinogenesis.1, 9, 10 In our rat model, intrahepatic transplantation Ibrutinib in vivo of a low number of pancreatic islets is able to ameliorate, but not to normalize, hyperglycemia, thus perpetuating local hyperinsulinemia and inducing a well-defined sequence of morphological events in the downstream hepatocytes, leading to the development of preneoplastic foci and HCC.19-22 In the present study, we investigated the function of the AKT/mTOR pathway as a downstream effector of the insulin-signaling

cascade in this rat model. Overall, our results imply a central role of AKT signaling in mediating multiple biochemical and molecular events (e.g., up-regulation of lipogenesis, glycolysis, and the pentose MCE公司 phosphate pathway as well as down-regulation of fatty acid β-oxidation and gluconeogenesis) induced by insulin deregulation. Of note, subsequent experiments in human HCC cell lines supplemented with insulin showed that suppression of lipogenesis, glycolysis, and/or the pentose phosphate pathway results in growth restraint of these cells. This finding clearly indicates that the metabolic alterations induced by the AKT/mTOR cascade mediate at least some of the growth properties of insulin, thus linking metabolic alterations and aberrant liver growth in this model.