Altered cellular metabolism, including an increased dependence on aerobic glycolysis, is a hallmark of cancer. Despite the fact that this observation was first made nearly a century ago, effective therapeutic targeting of glycolysis in cancer has remained elusive. One potentially promising approach involves targeting the glycolytic enzyme lactate dehydrogenase (LDH), which is overexpressed and plays a critical role in several cancers. Here, we used a novel class of LDH inhibitors to demonstrate, for the first time, that Ewing sarcoma cells are exquisitely sensitive to inhibition of LDH. EWS-FLI1, the oncogenic driver of Ewing sarcoma, regulated LDH A (LDHA) expression. Genetic depletion of LDHA inhibited proliferation of Ewing sarcoma cells and induced apoptosis, phenocopying pharmacologic inhibition of LDH. LDH inhibitors affected Ewing sarcoma cell viability both in vitro and in vivo by reducing glycolysis. Intravenous administration of LDH inhibitors resulted in the greatest intratumoral drug accumulation, inducing tumor cell death and reducing tumor growth. The major dose-limiting toxicity observed was hemolysis, indicating that a narrow therapeutic window exists for these compounds. Taken together, these data suggest that targeting glycolysis through inhibition of LDH should be further investigated as a potential therapeutic approach for cancers such as Ewing sarcoma that exhibit oncogene-dependent expression of LDH and increased glycolysis.Significance: LDHA is a pharmacologically tractable EWS-FLI1 transcriptional target that regulates the glycolytic dependence of Ewing sarcoma.

Isocitrate dehydrogenase (IDH) mutation is a common genetic abnormality in human malignancies characterized by remarkable metabolic reprogramming. Our present study demonstrated that IDH1-mutated cells showed elevated levels of reactive oxygen species and higher demands on Nrf2-guided glutathione de novo synthesis. Our findings showed that triptolide, a diterpenoid epoxide from Tripterygium wilfordii, served as a potent Nrf2 inhibitor, which exhibited selective cytotoxicity to patient-derived IDH1-mutated glioma cells in vitro and in vivo. Mechanistically, triptolide compromised the expression of GCLC, GCLM, and SLC7A11, which disrupted glutathione metabolism and established synthetic lethality with reactive oxygen species derived from IDH1 mutant neomorphic activity. Our findings highlight triptolide as a valuable therapeutic approach for IDH1-mutated malignancies by targeting the Nrf2-driven glutathione synthesis pathway.

Background: Osteosarcoma (OS) is a malignant bone tumor that often develops during the period of rapid growth associated with adolescence. Despite successful primary tumor control accompanied by adjuvant chemotherapy, death from pulmonary metastases occurs in approximately 30% of patients within 5 years. As overall survival in patients remains unchanged over the last 30 years, urgent needs for novel therapeutic strategies exist. Cancer metastasis is characterized by complex molecular events which result from alterations in gene and protein expression/function. Recent studies suggest that metabolic adaptations, or "metabolic reprogramming," may similarly contribute to cancer metastasis. The goal of this study was to specifically interrogate the metabolic vulnerabilities of highly metastatic OS cell lines in a series of in vitro and in vivo experiments, in order to identify a tractable metabolically targeted therapeutic strategy for patients. Methods: Nutrient deprivation and drug treatment experiments were performed in MG63.3, 143B, and K7M2 OS cell lines to identify the impact of glutaminase-1 (GLS1) inhibition and metformin treatment on cell proliferation. We functionally validated the impact of drug treatment with extracellular flux analysis, nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry. 13 C-glucose and 13 C-glutamine tracing was employed to identify specific contributions of these nutrients to the global metabolic profiles generated with GLS1 inhibition and metformin treatment in vivo. Results: Highly metastatic OS cell lines require glutamine for proliferation, and exposure to CB-839, in combination with metformin, induces both primary tumor growth inhibition and a distinct reduction in metastatic outgrowth in vivo. Further, combination-treated OS cells showed a reduction in cellular mitochondrial respiration, while NMR confirmed the pharmacodynamic effects of glutaminase inhibition in tumor tissues. We observed global decreases in glycolysis and tricarboxylic acid (TCA) cycle functionality, alongside an increase in fatty acid oxidation and pyrimidine catabolism. Conclusions: This data suggests combination-treated cells cannot compensate for metformin-induced electron transport chain inhibition by upregulating glutaminolysis to generate TCA cycle intermediates required for cell proliferation, translating into significant reductions in tumor growth and metastatic progression. This therapeutic approach could be considered for future clinical development for OS patients presenting with or at high risk of developing metastasis.

In addition to providing integrity to cellular structure, the various classes of lipids participate in a multitude of functions including secondary messengers, receptor stimulation, lymphocyte trafficking, inflammation, angiogenesis, cell migration, proliferation, necrosis and apoptosis, thus highlighting the importance of understanding their role in the tumor phenotype. In the context of IDH1mut glioma, investigations focused on metabolic alterations involving lipidomics’ present potential to uncover novel vulnerabilities. Herein, a detailed lipidomic analysis of the sphingolipid metabolism was conducted in patient-derived IDH1mut glioma cell lines, as well as model systems, with the of identifying points of metabolic vulnerability. We probed the effect of decreasing D-2HG levels on the sphingolipid pathway, by treating these cell lines with an IDH1mut inhibitor, AGI5198. The results revealed that N,N-dimethylsphingosine (NDMS), sphingosine C17 and sphinganine C18 were significantly downregulated, while sphingosine-1-phosphate (S1P) was significantly upregulated in glioma cultures following suppression of IDH1mut activity. We exploited the pathway using a small-scale, rational drug screen and identified a combination that was lethal to IDHmut cells. Our work revealed that further addition of N,N-dimethylsphingosine in combination with sphingosine C17 triggered a dose-dependent biostatic and apoptotic response in a panel of IDH1mut glioma cell lines specifically, while it had little effect on the IDHWT cells probed here. To our knowledge, this is the first study that shows how altering the sphingolipid pathway in IDH1mut gliomas elucidates susceptibility that can arrest proliferation and initiate subsequent cellular death.

Infiltrating gliomas are devastating and incurable tumors. Amongst all gliomas, those harboring a mutation in isocitrate dehydrogenase 1 mutation (IDH1mut) acquire a different tumor biology and clinical manifestation from those that are IDH1WT. Understanding the unique metabolic profile reprogrammed by IDH1 mutation has the potential to identify new molecular targets for glioma therapy. Herein, we uncover increased monounsaturated fatty acids (MUFA) and their phospholipids in endoplasmic reticulum (ER), generated by IDH1 mutation, that are responsible for Golgi and ER dilation. We demonstrate a direct link between the IDH1 mutation and this organelle morphology via D-2HG-induced stearyl-CoA desaturase (SCD) overexpression, the rate-limiting enzyme in MUFA biosynthesis. Inhibition of IDH1 mutation or SCD silencing restores ER and Golgi morphology, while D-2HG and oleic acid induces morphological defects in these organelles. Moreover, addition of oleic acid, which tilts the balance towards elevated levels of MUFA, produces IDH1mut-specific cellular apoptosis. Collectively, these results suggest that IDH1mut-induced SCD overexpression can rearrange the distribution of lipids in the organelles of glioma cells, providing new insight into the link between lipid metabolism and organelle morphology in these cells, with potential and unique therapeutic implications.

Background Early detection of increased aggressiveness of brain tumors is a major challenge in the field of neuro-oncology because of the inability of traditional imaging to uncover it. Isocitrate dehydrogenase (IDH)-mutant gliomas represent an ideal model system to study the molecular mechanisms associated with tumorigenicity because they appear indolent and non-glycolytic initially, but eventually a subset progresses toward secondary glioblastoma with a Warburg-like phenotype. The mechanisms and molecular features associated with this transformation are poorly understood. Methods We employed model systems for IDH1 mutant (IDH1mut) gliomas with different growth and proliferation rates in vivo and in vitro. We described the metabolome, transcriptome, and epigenome of these models in order to understand the link between their metabolism and the tumor biology. To verify whether this metabolic reprogramming occurs in the clinic, we analyzed data from The Cancer Genome Atlas. Results We reveal that the aggressive glioma models have lost DNA methylation in the promoters of glycolytic enzymes, especially lactate dehydrogenase A (LDHA), and have increased mRNA and metabolite levels compared with the indolent model. We find that the acquisition of the high glycolytic phenotype occurs at the glioma cytosine-phosphate-guanine island methylator phenotype (G-CIMP)-high molecular subtype in patients and is associated with the worst outcome. Conclusion We propose very early monitoring of lactate levels as a biomarker of metabolic reprogramming and tumor aggressiveness.

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35Cytosolic IDH1 enzyme plays a key, but currently unexplored, role in lipid biosynthesis. Using 36Raman imaging microscopy, we identified heterogeneous lipid profiles in cellular organelles 37 attributed uniquely to IDH1 mutations. Via organelle lipidomics, we found an increase in saturated 38 and monounsaturated fatty acids in the endoplasmic reticulum of IDH1 mut cells compared with 39 IDH WT glioma. We showed that these fatty acids incorporate into phospholipids and induce 40 organelle dysfunctions, with prominent dilation of Golgi apparatus, which can be restored by 41 transient knockdown of stearyl-CoA desaturase or inhibition of D-2-hydroxyglutarate (D-2HG) 42 formation. We validated these findings using tissue from patients with glioma. Oleic acid addition 43 led to increased sensitivity to apoptosis of IDH1 mut cells compared with IDH WT . Addition of D-2HG 44 to U251 WT cells lead in increased ER and Golgi apparatus dilation. Collectively, these studies 45 provide clinically relevant insights into the functional link between IDH1 mut -induced lipid alterations 46 and organelle dysfunction, with therapeutic implications. 48 Significance 52Gliomas are devastating tumors, with the most aggressive form-glioblastoma multiforme-53 correlated with a mean patient survival of 14.5 months. No curative treatment exists to date. Low-54 grade glioma (LGG) with the isocitrate dehydrogenase 1 (IDH1) mutation, R132H, provides a 55 survival benefit to patients. Understanding the unique metabolic profile of IDH1 mut could provide 56 clues regarding its association with longer survival and information about therapeutic targets. 57Herein, we identified lipid imbalances in organelles, generated by IDH mut in cells and patient 58 tissue, that were responsible for Golgi dilation and that correlated with increased survival. Addition 59 3 of oleic acid, which tilted the balance towards elevated levels of monounsaturated fatty acids 60 produced IDH1 mut -specific cellular apoptosis. 65 et al., 2019, Lopez et al., 2010, Victor et al., 2019). IDH1 mutations are an early event, (Lass et 66 al., 2012) are associated with a less aggressive phenotype (Parsons et al., 2008) potentially due 67 to their slow growth and need for nutrients to form D-2-hydroxyglutarate (D-2HG), and are used 68 as prognostic and diagnostic markers of glioma . In fact, the World Health Organization (WHO) 69 released a novel classification of glioma in 2016 to include IDH1 mutations as molecular markers 70 that dictate the classification (Louis et al., 2016). Much effort has been directed toward inhibiting 71 D-2HG formation(Yen et al., 2010, Han and Batchelor, 2017); however, the links between IDH1 72 mutations, tumor metabolism, and clinical manifestation are not well understood.73 Cytosolic NADP-dependent IDH1 plays an important role in lipid biosynthesis via its the 74 production of citrate and NADPH (Koh et al., 2004). The loss of the wildtype (WT) allele in gliomas 75 with the arginine 132 to histidine mutation leads to impaired citrate formation; moreov...