Suppressing PD-L1 Expression via AURKA Kinase Inhibition Enhances Natural Killer Cell-Mediated Cytotoxicity against Glioblastoma.

Immunotherapies have shown significant promise as an impactful strategy in cancer treatment. However, in glioblastoma multiforme (GBM), the most prevalent primary brain tumor in adults, these therapies have demonstrated lower efficacy than initially anticipated. Consequently, there is an urgent need for strategies to enhance the effectiveness of immune treatments. AURKA has been identified as a potential drug target for GBM treatment. An analysis of the GBM cell transcriptome following AURKA inhibition revealed a potential influence on the immune system. Our research revealed that AURKA influenced PD-L1 levels in various GBM model systems in vitro and in vivo. Disrupting AURKA function genetically led to reduced PD-L1 levels and increased MHC-I expression in both established and patient-derived xenograft GBM cultures. This process involved both transcriptional and non-transcriptional pathways, partly implicating GSK3ß. Interfering with AURKA also enhanced NK-cell-mediated elimination of GBM by reducing PD-L1 expression, as evidenced in rescue experiments. Furthermore, using a mouse model that mimics GBM with patient-derived cells demonstrated that Alisertib decreased PD-L1 expression in living organisms. Combination therapy involving anti-PD-1 treatment and Alisertib significantly prolonged overall survival compared to vehicle treatment. These findings suggest that targeting AURKA could have therapeutic implications for modulating the immune environment within GBM cells.

Revolutionizing Brain Tumor Care: Emerging Technologies and Strategies.

Glioblastoma multiforme (GBM) is one of the most aggressive forms of brain tumor, characterized by a daunting prognosis with a life expectancy hovering around 12-16 months. Despite a century of relentless research, only a select few drugs have received approval for brain tumor treatment, largely due to the formidable barrier posed by the blood-brain barrier. The current standard of care involves a multifaceted approach combining surgery, irradiation, and chemotherapy. However, recurrence often occurs within months despite these interventions. The formidable challenges of drug delivery to the brain and overcoming therapeutic resistance have become focal points in the treatment of brain tumors and are deemed essential to overcoming tumor recurrence. In recent years, a promising wave of advanced treatments has emerged, offering a glimpse of hope to overcome the limitations of existing therapies. This review aims to highlight cutting-edge technologies in the current and ongoing stages of development, providing patients with valuable insights to guide their choices in brain tumor treatment.

A cell state specific metabolic vulnerability to GPX4-dependent ferroptosis in glioblastoma.

Glioma cells hijack developmental transcriptional programs to control cell state. During neural development, lineage trajectories rely on specialized metabolic pathways. However, the link between tumor cell state and metabolic programs is poorly understood in glioma. Here we uncover a glioma cell state-specific metabolic liability that can be leveraged therapeutically. To model cell state diversity, we generated genetically engineered murine gliomas, induced by deletion of p53 alone (p53) or with constitutively active Notch signaling (N1IC), a pathway critical in controlling cellular fate. N1IC tumors harbored quiescent astrocyte-like transformed cell states while p53 tumors were predominantly comprised of proliferating progenitor-like cell states. N1IC cells exhibit distinct metabolic alterations, with mitochondrial uncoupling and increased ROS production rendering them more sensitive to inhibition of the lipid hydroperoxidase GPX4 and induction of ferroptosis. Importantly, treating patient-derived organotypic slices with a GPX4 inhibitor induced selective depletion of quiescent astrocyte-like glioma cell populations with similar metabolic profiles.

Dietary restriction of cysteine and methionine sensitizes gliomas to ferroptosis and induces alterations in energetic metabolism.

Ferroptosis is mediated by lipid peroxidation of phospholipids containing polyunsaturated fatty acyl moieties. Glutathione, the key cellular antioxidant capable of inhibiting lipid peroxidation via the activity of the enzyme glutathione peroxidase 4 (GPX-4), is generated directly from the sulfur-containing amino acid cysteine, and indirectly from methionine via the transsulfuration pathway. Herein we show that cysteine and methionine deprivation (CMD) can synergize with the GPX4 inhibitor RSL3 to increase ferroptotic cell death and lipid peroxidation in both murine and human glioma cell lines and in ex vivo organotypic slice cultures. We also show that a cysteine-depleted, methionine-restricted diet can improve therapeutic response to RSL3 and prolong survival in a syngeneic orthotopic murine glioma model. Finally, this CMD diet leads to profound in vivo metabolomic, proteomic and lipidomic alterations, highlighting the potential for improving the efficacy of ferroptotic therapies in glioma treatment with a non-invasive dietary modification.

Therapeutic Drug-Induced Metabolic Reprogramming in Glioblastoma.

Glioblastoma WHO IV (GBM), the most common primary brain tumor in adults, is a heterogenous malignancy that displays a reprogrammed metabolism with various fuel sources at its disposal. Tumor cells primarily appear to consume glucose to entertain their anabolic and catabolic metabolism. While less effective for energy production, aerobic glycolysis (Warburg effect) is an effective means to drive biosynthesis of critical molecules required for relentless growth and resistance to cell death. Targeting the Warburg effect may be an effective venue for cancer treatment. However, past and recent evidence highlight that this approach may be limited in scope because GBM cells possess metabolic plasticity that allows them to harness other substrates, which include but are not limited to, fatty acids, amino acids, lactate, and acetate. Here, we review recent key findings in the literature that highlight that GBM cells substantially reprogram their metabolism upon therapy. These studies suggest that blocking glycolysis will yield a concomitant reactivation of oxidative energy pathways and most dominantly beta-oxidation of fatty acids.

Dissecting the treatment-naive ecosystem of human melanoma brain metastasis.

Melanoma brain metastasis (MBM) frequently occurs in patients with advanced melanoma; yet, our understanding of the underlying salient biology is rudimentary. Here, we performed single-cell/nucleus RNA-seq in 22 treatment-naive MBMs and 10 extracranial melanoma metastases (ECMs) and matched spatial single-cell transcriptomics and T cell receptor (TCR)-seq. Cancer cells from MBM were more chromosomally unstable, adopted a neuronal-like cell state, and enriched for spatially variably expressed metabolic pathways. Key observations were validated in independent patient cohorts, patient-derived MBM/ECM xenograft models, RNA/ATAC-seq, proteomics, and multiplexed imaging. Integrated spatial analyses revealed distinct geography of putative cancer immune evasion and evidence for more abundant intra-tumoral B to plasma cell differentiation in lymphoid aggregates in MBM. MBM harbored larger fractions of monocyte-derived macrophages and dysfunctional TOX+CD8+ T cells with distinct expression of immune checkpoints. This work provides comprehensive insights into MBM biology and serves as a foundational resource for further discovery and therapeutic exploration.

Induction of Synthetic Lethality by Activation of Mitochondrial ClpP and Inhibition of HDAC1/2 in Glioblastoma.

PURPOSE: Novel therapeutic targets are critical to unravel for the most common primary brain tumor in adults, glioblastoma (GBM). We have identified a novel synthetic lethal interaction between ClpP activation and HDAC1/2 inhibition that converges on GBM energy metabolism. EXPERIMENTAL DESIGN: Transcriptome, metabolite, and U-13C-glucose tracing analyses were utilized in patient-derived xenograft (PDX) models of GBM. Orthotopic GBM models were used for in vivo studies. RESULTS: We showed that activation of the mitochondrial ClpP protease by mutant ClpP (Y118A) or through utilization of second-generation imipridone compounds (ONC206 and ONC212) in combination with genetic interference of HDAC1 and HDAC2 as well as with global (panobinostat) or selective (romidepsin) HDAC inhibitors caused synergistic reduction of viability in GBM model systems, which was mediated by interference with tricarboxylic acid cycle activity and GBM cell respiration. This effect was partially mediated by activation of apoptosis along with activation of caspases regulated chiefly by Bcl-xL and Mcl-1. Knockdown of the ClpP protease or ectopic expression of a ClpP D190A mutant substantially rescued from the inhibition of oxidative energy metabolism as well as from the reduction of cellular viability by ClpP activators and the combination treatment, respectively. Finally, utilizing GBM PDX models, we demonstrated that the combination treatment of HDAC inhibitors and imipridones prolonged host survival more potently than single treatments or vehicle in vivo. CONCLUSIONS: Collectively, these observations suggest that the efficacy of HDAC inhibitors might be significantly enhanced through ClpP activators in model systems of human GBM.

Methodological Approaches for Assessing Metabolomic Changes in Glioblastomas.

Glioblastoma (GBM), a highly malignant primary brain tumor, inevitably leads to death. In the last decade, a variety of novel molecular characteristics of GBMs were unraveled. The identification of the mutation in the IDH1 and less commonly IDH2 gene was surprising and ever since has nurtured research in the field of GBM metabolism. While initially thought that mutated IDH1 were to act as a loss of function mutation it became clear that it conferred the production of an oncometabolite that in turn substantially reprograms GBM metabolism. While mutated IDH1 represents truly the tip of the iceberg, there are numerous other related observations in GBM that are of significant interest to the field, including the notion that oxidative metabolism appears to play a more critical role than believed earlier. Metabolic zoning is another important hallmark of GBM since it was found that the infiltrative margin that drives GBM progression reveals enrichment of fatty acid derivatives. Consistently, fatty acid metabolism appears to be a novel therapeutic target for GBM. How metabolism in GBM intersects is another pivotal issue that appears to be important for its progression and response and resistance to therapies. In this review, we will summarize some of the most relevant findings related to GBM metabolism and cell death and how these observations are influencing the field. We will provide current approaches that are applied in the field to measure metabolomic changes in GBM models, including the detection of unlabeled and labeled metabolites as well as extracellular flux analysis.

Aurora kinase A inhibition reverses the Warburg effect and elicits unique metabolic vulnerabilities in glioblastoma.

Aurora kinase A (AURKA) has emerged as a drug target for glioblastoma (GBM). However, resistance to therapy remains a critical issue. By integration of transcriptome, chromatin immunoprecipitation sequencing (CHIP-seq), Assay for Transposase-Accessible Chromatin sequencing (ATAC-seq), proteomic and metabolite screening followed by carbon tracing and extracellular flux analyses we show that genetic and pharmacological AURKA inhibition elicits metabolic reprogramming mediated by inhibition of MYC targets and concomitant activation of Peroxisome Proliferator Activated Receptor Alpha (PPARA) signaling. While glycolysis is suppressed by AURKA inhibition, we note an increase in the oxygen consumption rate fueled by enhanced fatty acid oxidation (FAO), which was accompanied by an increase of Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α). Combining AURKA inhibitors with inhibitors of FAO extends overall survival in orthotopic GBM PDX models. Taken together, these data suggest that simultaneous targeting of oxidative metabolism and AURKAi might be a potential novel therapy against recalcitrant malignancies.

Targeting super-enhancers reprograms glioblastoma central carbon metabolism.

The concept that tumor cells demand a distinct form of metabolism was appreciated almost a century ago when the German biochemist Otto Warburg realized that tumor cells heavily utilize glucose and produce lactic acid while relatively reducing oxidative metabolism. How this phenomenon is orchestrated and regulated is only partially understood and seems to involve certain transcription factors, including c-Myc, HIF1A and others. The epigenome eintails the posttranslational modification of histone proteins which in turn are involved in regulation of transcription. Recently, it was found that cis-regulatory elements appear to facilitate the Warburg effects since several genes encoding for glycolysis and associated pathways are surrounded by enhancer/super-enhancer regions. Disruption of these regions by FDA-approved HDAC inhibitors suppressed the transcription of these genes and elicited a reversal of the Warburg effect with activation of transcription factors facilitating oxidative energy metabolism with increases in transcription factors that are part of the PPARA family. Therefore, combined targeting of HDACs and oxidative metabolism suppressed tumor growth in patient-derived xenograft models of solid tumors, including glioblastoma.

RAB38 Facilitates Energy Metabolism and Counteracts Cell Death in Glioblastoma Cells.

Glioblastoma is a high-grade glial neoplasm with a patient survival of 12-18 months. Therefore, the identification of novel therapeutic targets is an urgent need. RAB38 is a GTPase protein implicated in regulating cell proliferation and survival in tumors. The role of RAB38 in glioblastoma is relatively unexplored. Here, we test the hypothesis that RAB38 regulates glioblastoma growth using human glioblastoma cell lines. We found that genetic interference of RAB38 resulted in a decrease in glioblastoma growth through inhibition of proliferation and cell death induction. Transcriptome analysis showed that RAB38 silencing leads to changes in genes related to mitochondrial metabolism and intrinsic apoptosis (e.g., Bcl-xL). Consistently, rescue experiments demonstrated that loss of RAB38 causes a reduction in glioblastoma viability through downregulation of Bcl-xL. Moreover, RAB38 knockdown inhibited both glycolysis and oxidative phosphorylation. Interference with RAB38 enhanced cell death induced by BH3-mimetics. RAB38 antagonists are under development, but not yet clinically available. We found that FDA-approved statins caused a rapid reduction in RAB38 protein levels, increased cell death, and phenocopied some of the molecular changes elicited by loss of RAB38. In summary, our findings suggest that RAB38 is a potential therapeutic target for glioblastoma treatment.

Cell-Penetrating CEBPB and CEBPD Leucine Zipper Decoys as Broadly Acting Anti-Cancer Agents.

Transcription factors are key players underlying cancer formation, growth, survival, metastasis and treatment resistance, yet few drugs exist to directly target them. Here, we characterized the in vitro and in vivo anti-cancer efficacy of novel synthetic cell-penetrating peptides (Bpep and Dpep) designed to interfere with the formation of active leucine-zipper-based dimers by CEBPB and CEBPD, transcription factors implicated in multiple malignancies. Both peptides similarly promoted apoptosis of multiple tumor lines of varying origins, without such effects on non-transformed cells. Combined with other treatments (radiation, Taxol, chloroquine, doxorubicin), the peptides acted additively to synergistically and were fully active on Taxol-resistant cells. The peptides suppressed expression of known direct CEBPB/CEBPD targets IL6, IL8 and asparagine synthetase (ASNS), supporting their inhibition of transcriptional activation. Mechanisms by which the peptides trigger apoptosis included depletion of pro-survival survivin and a required elevation of pro-apoptotic BMF. Bpep and Dpep significantly slowed tumor growth in mouse models without evident side effects. Dpep significantly prolonged survival in xenograft models. These findings indicate the efficacy and potential of Bpep and Dpep as novel agents to treat a variety of cancers as mono- or combination therapies.

Cbl-b deficiency prevents functional but not phenotypic T cell anergy.

T cell anergy is an important peripheral tolerance mechanism. We studied how T cell anergy is established using an anergy model in which the Zap70 hypermorphic mutant W131A is coexpressed with the OTII TCR transgene (W131AOTII). Anergy was established in the periphery, not in the thymus. Contrary to enriched tolerance gene signatures and impaired TCR signaling in mature peripheral CD4 T cells, CD4SP thymocytes exhibited normal TCR signaling in W131AOTII mice. Importantly, the maintenance of T cell anergy in W131AOTII mice required antigen presentation via MHC-II. We investigated the functional importance of the inhibitory receptor PD-1 and the E3 ubiquitin ligases Cbl-b and Grail in this model. Deletion of each did not affect expression of phenotypic markers of anergic T cells or T reg numbers. However, deletion of Cbl-b, but not Grail or PD-1, in W131AOTII mice restored T cell responsiveness and signaling. Thus, Cbl-b plays an essential role in the establishment and/or maintenance of unresponsiveness in T cell anergy.

Epigenetic Targeting of Mcl-1 Is Synthetically Lethal with Bcl-xL/Bcl-2 Inhibition in Model Systems of Glioblastoma.

Apoptotic resistance remains a hallmark of glioblastoma (GBM), the most common primary brain tumor in adults, and a better understanding of this process may result in more efficient treatments. By utilizing chromatin immunoprecipitation with next-generation sequencing (CHIP-seq), we discovered that GBMs harbor a super enhancer around the Mcl-1 locus, a gene that has been known to confer cell death resistance in GBM. We utilized THZ1, a known super-enhancer blocker, and BH3-mimetics, including ABT263, WEHI-539, and ABT199. Combined treatment with BH3-mimetics and THZ1 led to synergistic growth reduction in GBM models. Reduction in cellular viability was accompanied by significant cell death induction with features of apoptosis, including disruption of mitochondrial membrane potential followed by activation of caspases. Mechanistically, THZ1 elicited a profound disruption of the Mcl-1 enhancer region, leading to a sustained suppression of Mcl-1 transcript and protein levels, respectively. Mechanism experiments suggest involvement of Mcl-1 in the cell death elicited by the combination treatment. Finally, the combination treatment of ABT263 and THZ1 resulted in enhanced growth reduction of tumors without induction of detectable toxicity in two patient-derived xenograft models of GBM in vivo. Taken together, these findings suggest that combined epigenetic targeting of Mcl-1 along with Bcl-2/Bcl-xL is potentially therapeutically feasible.

Inhibition of HDAC1/2 Along with TRAP1 Causes Synthetic Lethality in Glioblastoma Model Systems.

The heterogeneity of glioblastomas, the most common primary malignant brain tumor, remains a significant challenge for the treatment of these devastating tumors. Therefore, novel combination treatments are warranted. Here, we showed that the combined inhibition of TRAP1 by gamitrinib and histone deacetylases (HDAC1/HDAC2) through romidepsin or panobinostat caused synergistic growth reduction of established and patient-derived xenograft (PDX) glioblastoma cells. This was accompanied by enhanced cell death with features of apoptosis and activation of caspases. The combination treatment modulated the levels of pro- and anti-apoptotic Bcl-2 family members, including BIM and Noxa, Mcl-1, Bcl-2 and Bcl-xL. Silencing of Noxa, BAK and BAX attenuated the effects of the combination treatment. At the metabolic level, the combination treatment led to an enhanced reduction of oxygen consumption rate and elicited an unfolded stress response. Finally, we tested whether the combination treatment of gamitrinib and panobinostat exerted therapeutic efficacy in PDX models of glioblastoma (GBM) in mice. While single treatments led to mild to moderate reduction in tumor growth, the combination treatment suppressed tumor growth significantly stronger than single treatments without induction of toxicity. Taken together, we have provided evidence that simultaneous targeting of TRAP1 and HDAC1/2 is efficacious to reduce tumor growth in model systems of glioblastoma.

Mitral prosthetic size predictor in minimally invasive mitral valve replacement.

BACKGROUND: Minimally invasive mitral valve replacement has become popular across the world. However, annular rupture and patient - prosthetic mismatch (PPM) are still problematic, particularly in the Asian population. To avoid this, a predictor model could be beneficial. Our study aimed to assess the value of mitral valve diameters measured on TTE and CT scan on predicting the actual mitral prostheses. METHODS: From January 2018 to December 2019, a total number of 96 patients underwent minimally invasive mitral valve replacement. The association between imaging measurements and the outcome was checked by scatter plot and Pearson's correlation coefficient. Univariable linear regression was used to build the prediction model. RESULTS: The three strongest correlations for the whole population are the following features: Mean TTE diameter (0.702), mean diameter on CT lowest plane through the mitral annulus (0.679), and area-derived diameter on CT highest plane through the mitral annulus (0.665). The prosthetic size of the tissue valve group was more correlated to the calculated annulus diameters than that of the mechanical valve group. Tissue valve size predictor models based on these calculated diameters were 16.19 + 0.27 × d (r = 0.744), 12.74 + 0.44 × d (r = 0.756) and 12.79 + 0.38 × d (r = 0.730), respectively. CONCLUSION: Mitral prosthetic size could be predicted based on the mitral diameters measured on TTE and CT scan. The overall correlation coefficient varied from 0.665 (CT Scan) to 0.702 (TTE). These models performed better when applied to bioprosthesis.

Contrasting effects of stored allogeneic red blood cells and their supernatants on permeability and inflammatory responses in human pulmonary endothelial cells.

Transfusion of red blood cells (RBCs) is a common life-saving clinical practice in severely anemic or hemorrhagic patients; however, it may result in serious pathological complications such as transfusion-related acute lung injury. The factors mediating the deleterious effects of RBC transfusion remain unclear. In this study, we tested the effects of washed long-term (RBC-O; >28 days) versus short-term (RBC-F; <14 days) stored RBCs and their supernatants on lung endothelial (EC) permeability under control and inflammatory conditions. RBCs enhanced basal EC barrier function as evidenced by an increase in transendothelial electrical resistance and decrease in permeability for macromolecules. RBCs also attenuated EC hyperpermeability and suppressed secretion of EC adhesion molecule ICAM-1 and proinflammatory cytokine IL-8 in response to LPS or TNF-α. In both settings, RBC-F had slightly higher barrier protective effects as compared with RBC-O. In contrast, supernatants from both RBC-F and RBC-O disrupted the EC barrier. The early phase of EC permeability response caused by RBC supernatants was partially suppressed by antioxidant N-acetyl cysteine and inhibitor of Src kinase family PP2, while addition of heme blocker and inhibition of NOD-like receptor family pyrin domain containing protein 3 (NLRP3), stress MAP kinases, receptor for advanced glycation end-products (RAGE), or Toll-like receptor-4 (TLR4) signaling were without effect. Morphological analysis revealed that RBC supernatants increased LPS- and TNF-α-induced breakdown of intercellular junctions and formation of paracellular gaps. RBC supernatants augmented LPS- and TNF-α-induced EC inflammation reflected by increased production of IL-6, IL-8, and soluble ICAM-1. These findings demonstrate the deleterious effects of RBC supernatants on EC function, which may have a major impact in pathological consequences associated with RBC transfusion.

MET Inhibition Elicits PGC1α-Dependent Metabolic Reprogramming in Glioblastoma.

The receptor kinase c-MET has emerged as a target for glioblastoma therapy. However, treatment resistance emerges inevitably. Here, we performed global metabolite screening with metabolite set enrichment coupled with transcriptome and gene set enrichment analysis and proteomic screening, and identified substantial reprogramming of tumor metabolism involving oxidative phosphorylation and fatty acid oxidation (FAO) with substantial accumulation of acyl-carnitines accompanied by an increase of PGC1α in response to genetic (shRNA and CRISPR/Cas9) and pharmacologic (crizotinib) inhibition of c-MET. Extracellular flux and carbon tracing analyses (U-13C-glucose, U-13C-glutamine, and U-13C-palmitic acid) demonstrated enhanced oxidative metabolism, which was driven by FAO and supported by increased anaplerosis of glucose carbons. These findings were observed in concert with increased number and fusion of mitochondria and production of reactive oxygen species. Genetic interference with PGC1α rescued this oxidative phenotype driven by c-MET inhibition. Silencing and chromatin immunoprecipitation experiments demonstrated that cAMP response elements binding protein regulates the expression of PGC1α in the context of c-MET inhibition. Interference with both oxidative phosphorylation (metformin, oligomycin) and ß-oxidation of fatty acids (etomoxir) enhanced the antitumor efficacy of c-MET inhibition. Synergistic cell death was observed with c-MET inhibition and gamitrinib treatment. In patient-derived xenograft models, combination treatments of crizotinib and etomoxir, and crizotinib and gamitrinib were significantly more efficacious than single treatments and did not induce toxicity. Collectively, we have unraveled the mechanistic underpinnings of c-MET inhibition and identified novel combination therapies that may enhance its therapeutic efficacy. SIGNIFICANCE: c-MET inhibition causes profound metabolic reprogramming that can be targeted by drug combination therapies.

Novel IDH1-Targeted Glioma Therapies.

Mutations in the isocitrate dehydrogenase (IDH) 1 gene are commonly found in human glioma, with the majority of low-grade gliomas harboring a recurrent point mutation (IDH1 R132H). Mutant IDH reveals an altered enzymatic activity leading to the synthesis of 2-hydroxyglutarate, which has been implicated in epigenetic mechanisms of oncogenesis. Nevertheless, it is unclear exactly how IDH mutations drive glioma initiation and progression, and it is also not clear why tumors with this mutation generally have a better prognosis than IDH wild-type tumors. Recognition of the high frequency of IDH mutations in glioma [and also in other malignancies, including acute myeloid leukemia (AML) and cholangiocarcinoma] have led to the development of a number of targeted agents that can inhibit these enzymes. Enasidenib and ivosidenib have both gained regulatory approval for IDH mutant AML. Both agents are still in early clinical phases for glioma therapy, as are a number of additional candidates (including AG-881, BAY1436032, and DS1001). A marked clinical problem in the development of these agents is overcoming the blood-brain barrier. An alternative approach to target the IDH1 mutation is by the induction of synthetic lethality with compounds that target poly (ADP-ribose) polymerase (PARP), glutamine metabolism, and the Bcl-2 family of proteins. We conclude that within the last decade, several approaches have been devised to therapeutically target the IDH1 mutation, and that, potentially, both IDH1 inhibitors and synthetic lethal approaches might be relevant for future therapies.

Metabolic Reprogramming by Dual AKT/ERK Inhibition through Imipridones Elicits Unique Vulnerabilities in Glioblastoma.

Purpose: 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).Experimental Design: 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.Results: Imipridones reduce the proliferation of patient-derived xenograft and stem-like glioblastoma cell cultures in vitro and in multiple xenograft models in vivo 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 GSK3ß at serine 9. GSK3ß 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 in vitro and in vivo 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 in vitro and in vivo Conclusions: 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. Clin Cancer Res; 24(21); 5392-406. ©2018 AACR.