Distinct inhibitory effects on mTOR signaling by ethanol and INK128 in diffuse large B-cell lymphoma

Abstract

BackgroundThe mechanistic target of rapamycin, (mTOR) kinase plays a pivotal role in controlling critical cellular growth and survival pathways, and its aberrant induction is implicated in cancer pathogenesis. Therefore, suppression of active mTOR signaling has been of great interest to researchers; several mTOR inhibitors have been discovered to date. Ethanol (EtOH), similar to pharmacologic mTOR inhibitors, has been shown to suppress the mTOR signaling pathway, though in a non-catalytic manner. Despite population studies showing that the consumption of EtOH has a protective effect against hematological malignancies, the mechanisms behind EtOH’s modulation of mTOR activity in cells and its downstream consequences are largely unknown. Here we evaluated the effects of EtOH on the mTOR pathway, in comparison to the active-site mTOR inhibitor INK128, and compared translatome analysis of their downstream effects in diffuse large B-cell lymphoma (DLBCL).ResultsTreatment of DLBCL cells with EtOH suppressed mTORC1 complex formation while increasing AKT phosphorylation and mTORC2 complex assembly. INK128 completely abrogated AKT phosphorylation without affecting the structure of mTORC1/2 complexes. Accordingly, EtOH less profoundly suppressed cap-dependent translation and global protein synthesis, compared to a remarkable inhibitory effect of INK128 treatment. Importantly, EtOH treatment induced the formation of stress granules, while INK128 suppressed their formation. Microarray analysis of polysomal RNA revealed that although both agents primarily affected cell growth and survival, EtOH and INK128 regulated the synthesis of mostly distinct genes involved in these processes. Though both EtOH and INK128 inhibited cell cycle, proliferation and autophagy, EtOH, in contrast to INK128, did not induce cell apoptosis.ConclusionGiven that EtOH, similar to pharmacologic mTOR inhibitors, inhibits mTOR signaling, we systematically explored the effect of EtOH and INK128 on mTOR signal transduction, components of the mTORC1/2 interaction and their downstream effectors in DLBCL malignancy. We found that EtOH partially inhibits mTOR signaling and protein translation, compared to INK128’s complete mTOR inhibition. Translatome analysis of mTOR downstream target genes established that differential inhibition of mTOR by EtOH and INK128 distinctly modulates translation of specific subsets of mRNAs involved in cell growth and survival, leading to differential cellular response and survival.Electronic supplementary materialThe online version of this article (doi:10.1186/s12964-015-0091-0) contains supplementary material, which is available to authorized users.

Polysome Profiling Links Translational Control to the Radioresponse of Glioblastoma Stem-like Cells

“…Thus, to test the accuracy of this prediction, we determined the effects of radiation on eIF4F-cap complex formation using m 7 -GTP batch chromatography to pull down the bound eIF4F complex, which was then subjected to immunoblotting for eIF4E, 4EBP1 and eIF4G. As shown in Figure 3B, treatment of GSCs with the ATP-competitive mTOR inhibitor INK128 reduced cap complex formation as indicated by the decrease in eIF4G and increase in 4EBP1 pulled down with eIF4E, consistent with previous studies (30, 31). In contrast, IR increased the amount of eIF4G pulled down, signifying an increase in cap complex formation in each of the GSC lines.…”

Alcohol consumption and risk of hematological malignancies: A meta‐analysis of prospective studies

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