No abstract

Certain gliomas often harbor a mutation in the activity center of IDH1 (R132H), which leads to the production of the oncometabolite 2-R-2-hydroxyglutarate (2-HG). In six model systems, including patient-derived stem cell-like glioblastoma cultures, inhibition of Bcl-xL induces significantly more apoptosis in IDH1-mutated cells than in wild-type IDH1 cells. Anaplastic astrocytoma samples with mutated IDH1 display lower levels of Mcl-1 than IDH1 wild-type tumors and specific knockdown of Mcl-1 broadly sensitizes glioblastoma cells to Bcl-xL inhibition-mediated apoptosis. Addition of 2-HG to glioblastoma cultures recapitulates the effects of the IDH mutation on intrinsic apoptosis, shuts down oxidative phosphorylation and reduces ATP levels in glioblastoma cells. 2-HG-mediated energy depletion activates AMPK (Threonine 172), blunting protein synthesis and mTOR signaling, culminating in a decline of Mcl-1. In an orthotopic glioblastoma xenograft model expressing mutated IDH1, Bcl-xL inhibition leads to long-term survival. These results demonstrate that IDH1-mutated gliomas are particularly vulnerable to Bcl-xL inhibition.

The goal of this study is to enhance the efficacy of imipridones, a novel class of AKT/ERK inhibitors that displayed limited therapeutic efficacy against glioblastoma (GBM). Gene set enrichment, LC/MS, and extracellular flux analyses were used to determine the mechanism of action of novel imipridone compounds, ONC206 and ONC212. Orthotopic patient-derived xenografts were utilized to evaluate therapeutic potency. Imipridones reduce the proliferation of patient-derived xenograft and stem-like glioblastoma cell cultures and in multiple xenograft models ONC212 displayed the highest potency. High levels of c-myc predict susceptibility to growth inhibition and apoptosis induction by imipridones and increased host survival in orthotopic patient-derived xenografts. As early as 1 hour, imipridones elicit on-target inhibition, followed by dephosphorylation of GSK3β at serine 9. GSK3β promotes phosphorylation of c-myc at threonine 58 and enhances its proteasomal degradation. Moreover, inhibition of c-myc by BRD4 antagonists sensitizes for imipridone-induced apoptosis in stem-like GBM cells and Imipridones affect energy metabolism by suppressing both glycolysis and oxidative phosphorylation, which is accompanied by a compensatory activation of the serine-one carbon-glycine (SOG) pathway, involving the transcription factor ATF4. Interference with the SOG pathway through novel inhibitors of PHGDH results in synergistic cell death induction and These results suggest that c-myc expression predicts therapeutic responses to imipridones and that imipridones lead to suppression of tumor cell energy metabolism, eliciting unique metabolic vulnerabilities that can be exploited for clinical relevant drug combination therapies..

Highlights d AAV9-mediated Stasimon expression improves motor function in SMA mice d Stasimon contributes to deafferentation and motor neuron death in SMA mice d Stasimon deficiency induces p53 phosphorylation through p38 MAPK activation d Pharmacological inhibition of p38 MAPK prevents neurodegeneration in SMA mice

Rational therapeutic approaches based on synthetic lethality may improve cancer management. Based on a high-throughput drug screen, we provide preclinical proof of concept that targeting the mitochondrial Hsp90 chaperone network (mtHsp90) and inhibition of Bcl-2, Bcl-xL and Mcl-1 is sufficient to elicit synthetic lethality in tumors recalcitrant to therapy. Our analyses focused on BH3 mimetics that are broad acting (ABT263 and Obatoclax) or selective (ABT199, WEHI-539 and A1210477), along with the established mitochondrial matrix chaperone inhibitor Gamitrinib-TPP. Drug combinations were tested in various therapy-resistant tumors in vitro and in vivo in murine model systems of melanoma, triple-negative breast cancer and patient-derived orthotopic xenografts of human glioblastoma (PDX). We found that combining BH3-mimetics and Gamitrinib-TPP blunted cellular proliferation in a synergistic manner by massive activation of intrinsic apoptosis. In like manner, suppressing either Bcl-2, Bcl-xL or Mcl-1 recapitulated the effects of BH3-mimetics and enhanced the effects of Gamitrinib-TPP. Mechanistic investigations revealed that Gamitrinib-TPP activated a PERK-dependent integrated stress response which activated the pro-apoptotic BH3 protein Noxa and its downstream targets Usp9X and Mcl-1. Notably, in the PDX glioblastoma and BRAFi-resistant melanoma models, this drug combination safely and significantly extended host survival. Our results show how combining mitochondrial chaperone and Bcl-2 family inhibitors can synergize to safely degrade the growth of tumors recalcitrant to other treatments.