MCL is an aggressive B-cell lymphoma with aberrant expression of several oncogenic effectors and requiring novel anticancer strategies. The nuclear transporter exportin-1 (XPO1) is highly expressed in MCL and is critical for cancer survival and proliferation. mTOR signaling is frequently activated and an important therapeutic target in MCL. In this study, we investigated the antitumor effects and molecular/metabolic changes induced by combined with dual mTOR inhibitor AZD-2014 and XPO1 inhibitor KPT-185 on MCL cells under the hypothesis that mTOR inhibition by AZD-2014 represses KPT-185 inducedupregulation of glycolysis.
Four MCL cell lines (Jeko-1, X138, JVM-2, and MINO), primary MCL cells, and normal bone marrow samples were utilized. Cell viability was evaluated by MTT assay. Cell cycle and apoptosis were determined by flow cytometric analysis. cDNA array, iTRAQ proteomic, immunoblotting and metabolome analysis using CE-TOF-MS were also performed.
AZD-2014 enhanced KPT-185-induced the inhibition of cell growth and repression of cell viability in MCL cells but not in normal bone marrow cells. Different mTOR inhibitors (AZD-8055 and MLN0128) demonstrated similar effects. AZD-2014+KPT-185 decreased expression of the oncogenic mediator c-Myc andthe translational/transcriptional network regulator HSF1as detected by immunoblotting. iTRAQ proteomic analysis demonstrated thatthe combination caused repression of ribosomal biogenesis. Treatment with either AZD-2014 or KPT-185 depressed phospho-S6.CET-OF-MS metabolite assay showed that AZD-2014+KPT-185inhibited theKrebs cycle, and that AZD-2014 effectively repressed KPT-185-induced upregulation of glycolysis. cDNA array detected downregulation of NOD2which is known to trigger activation of MAP kinases and of NF-kappa-B signaling. Moreover, AZD-2014+KPT-185 activated AMPK, an energy stress marker in a cell type-dependent manner.
Our findings indicated that the combinatorial inhibition of mTOR and XPO1 identifies a novel synthetic lethality mechanism that could be exploited clinically, following satisfactory completion of pre-clinical in vivo studies.
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All authors have declared no conflicts of interest.