Limiting dietary carbohydrates inhibits glioma growth in preclinical models. Therefore, the ERGO trial (NCT00575146) examined feasibility of a ketogenic diet in 20 patients with recurrent glioblastoma. Patients were put on a low-carbohydrate, ketogenic diet containing plant oils. Feasibility was the primary endpoint, secondary endpoints included the percentage of patients reaching urinary ketosis, progression-free survival (PFS) and overall survival. The effects of a ketogenic diet alone or in combination with bevacizumab was also explored in an orthotopic U87MG glioblastoma model in nude mice. Three patients (15%) discontinued the diet for poor tolerability. No serious adverse events attributed to the diet were observed. Urine ketosis was achieved at least once in 12 of 13 (92%) evaluable patients. One patient achieved a minor response and two patients had stable disease after 6 weeks. Median PFS of all patients was 5 (range, 3–13) weeks, median survival from enrollment was 32 weeks. The trial allowed to continue the diet beyond progression. Six of 7 (86%) patients treated with bevacizumab and diet experienced an objective response, and median PFS on bevacizumab was 20.1 (range, 12–124) weeks, for a PFS at 6 months of 43%. In the mouse glioma model, ketogenic diet alone had no effect on median survival, but increased that of bevacizumab-treated mice from 52 to 58 days (p<0.05). In conclusion, a ketogenic diet is feasible and safe but probably has no significant clinical activity when used as single agent in recurrent glioma. Further clinical trials are necessary to clarify whether calorie restriction or the combination with other therapeutic modalities, such as radiotherapy or anti-angiogenic treatments, could enhance the efficacy of the ketogenic diet.

Abstracts iii21NEURO-ONCOLOGY • MAY 2017 characterized, potential paracrine effects influencing antitumor immunity remain enigmatic. However, they are important to decipher, as immunotherapies targeting IDH1-mutant gliomas are emerging. AIM: This study aimed at characterizing a potential cell-specific modulatory role of the oncometabolite R-2-HG in shaping the immune microenvironment of IDH1-mutant gliomas. METHODS AND RESULTS: By means of expression dataset analyses, syngeneic murine tumor models and human glioma tissue, as well as a novel astrocyte-specific IDH1R132H-knock in model, we demonstrate that R-2-HG impairs endogenous and IDH1(R132H)-specific antitumor T cell immunity. This is underlined by functional and transcriptomic analyses of myeloid cells indicating a R-2-HG-driven induction of tolerogenicity and compromised antigen presentation. Metabolomic profiling was complemented by mitochondrial respiration assays, calcium measurements and pathway analyses in primary human and mouse immune cells to delineate key molecular mechanisms by which tumor-derived R-2-HG corrupts the glioma immunoenvironment. The functional relevance of R-2-HG-mediated impairment of antitumor immunity was demonstrated in vivo and potential pharmacological strategies abrogating its effects were assessed. CONCLU-SION: Glioma-derived R-2-HG impairs antitumor immunity by affecting both infiltrating T-cells and the associated myeloid compartment, thus contributing to tumorigenesis and resistance to therapy. Immunotherapeutic strategies against IDH-mutant gliomas may benefit from approaches to prevent excess R-2-HG production or its uptake by immune cells. BACKGROUND: Despite available treatment options for patients (pts) with recurrent glioblastoma (GBM), < 5% of pts survive 5 years beyond initial diagnosis, and no single-agent therapy has demonstrated a survival benefit in the second-line setting, including bevacizumab (bev), which is approved for the treatment of recurrent disease. Nivolumab (nivo), a fully human IgG4 monoclonal antibody that inhibits the programmed death 1 receptor, has provided clinical benefit in multiple cancer types. In cohort 2 of the open-label, phase 3 CheckMate 143 study (NCT02017717), the efficacy and safety of nivo was compared with that of bev in pts with GBM experiencing their first recurrence after prior radiotherapy (RT) and temozolomide (TMZ). METHODS: Pts with no prior VEGF therapy were randomized 1:1 to receive nivo 3 mg/kg Q2W or bev 10 mg/kg Q2W until confirmed disease progression; pts were stratified by the presence/absence of measurable disease. The primary endpoint was overall survival (OS); secondary endpoints were 12-mo OS rate and investigator-assessed progression-free survival (PFS) and objective response rate (ORR) per Response Assessment in Neuro-Oncology criteria. RESULTS: At the time of final analyses (Jan 20, 2017), 369 pts were randomized to the nivo (n = 184) or bev (n = 185) treatment arms; of these pts, 182 received nivo and 165 received bev. At baseline, most pts in the nivo (...

The Bloch sphere is a generic picture describing the coherent dynamics of coupled classical or quantum-mechanical twolevel systems under the control of electromagnetic fields 1,2 . It is commonly applied to systems such as spin ensembles 3 , atoms 4 , quantum dots 5 and superconducting circuits 6 . The underlying Bloch equations 7 describe the state evolution of the two-level system and allow the characterization of both energy and phase relaxation processes 3,8,9 . Here we realize a classical nanomechanical two-level system 2 driven by radiofrequency signals. It is based on the two orthogonal fundamental flexural modes of a high-quality-factor nanostring resonator that are strongly coupled by dielectric gradient fields 10 . Full Bloch sphere control is demonstrated by means of Rabi 11 , Ramsey 12 and Hahn echo 13 experiments. Furthermore, we determine the energy relaxation time T 1 and phase relaxation times T 2 and T * 2 , and find them all to be equal. Thus decoherence is dominated by energy relaxation, implying that not only T 1 but also T 2 can be increased by engineering larger mechanical quality factors.Whereas the dynamics of semiclassical two-level systems under the influence of a pulsed external electromagnetic field was observed decades ago in many-spin NMR experiments, a completely classical analogue remained elusive for a long time. Such a classical two-mode system can for example be created using two optical cavity modes 14 or mechanical resonators. Only recently, several approaches were employed to achieve purely mechanical resonant coupling either between separate resonators [15][16][17] or different modes of the same resonator 10,18 in the classical regime. So far, the pulsed coherent control of the system was prevented by weak coupling, low quality factors or the lack of a sufficiently strong and fast tuning mechanism.We present the successful implementation of a purely mechanical, classical two-level system, consisting of the two coupled fundamental flexural modes of a nanomechanical resonator with coherent time-domain control (see also the experiments independently performed using parametric coupling 19 instead of the linear coupling employed here). To this end, we use a 250 nm wide and 100 nm thick, strongly stressed 20 silicon nitride string resonator with a length of 50 µm dielectrically coupled to a pair of electrodes used for detection 21 as well as actuation and tuning 22 . The two fundamental flexural modes of the mechanical resonator oscillating in the out-of-plane and in-plane direction (Fig. 1a in the vicinity of the avoided crossing (Fig. 1b,c). Both voltages are added, combined with the radiofrequency actuation at a bias-tee, and applied to one electrode. The other electrode is connected to a 3.6 GHz microstrip cavity, enabling heterodyne detection of the string deflection 21 after addition of a microwave bypass capacitor at the first electrode 22 . These components, as well as the mechanical resonator, are placed in a vacuum of ≤10 −4 mbar and the system is cooled to 10.00±0.02 K...

BackgroundEven in the presence of oxygen, malignant cells often highly depend on glycolysis for energy generation, a phenomenon known as the Warburg effect. One strategy targeting this metabolic phenotype is glucose restriction by administration of a high-fat, low-carbohydrate (ketogenic) diet. Under these conditions, ketone bodies are generated serving as an important energy source at least for non-transformed cells.MethodsTo investigate whether a ketogenic diet might selectively impair energy metabolism in tumor cells, we characterized in vitro effects of the principle ketone body 3-hydroxybutyrate in rat hippocampal neurons and five glioma cell lines. In vivo, a non-calorie-restricted ketogenic diet was examined in an orthotopic xenograft glioma mouse model.ResultsThe ketone body metabolizing enzymes 3-hydroxybutyrate dehydrogenase 1 and 2 (BDH1 and 2), 3-oxoacid-CoA transferase 1 (OXCT1) and acetyl-CoA acetyltransferase 1 (ACAT1) were expressed at the mRNA and protein level in all glioma cell lines. However, no activation of the hypoxia-inducible factor-1α (HIF-1α) pathway was observed in glioma cells, consistent with the absence of substantial 3-hydroxybutyrate metabolism and subsequent accumulation of succinate. Further, 3-hydroxybutyrate rescued hippocampal neurons from glucose withdrawal-induced cell death but did not protect glioma cell lines. In hypoxia, mRNA expression of OXCT1, ACAT1, BDH1 and 2 was downregulated. In vivo, the ketogenic diet led to a robust increase of blood 3-hydroxybutyrate, but did not alter blood glucose levels or improve survival.ConclusionIn summary, glioma cells are incapable of compensating for glucose restriction by metabolizing ketone bodies in vitro, suggesting a potential disadvantage of tumor cells compared to normal cells under a carbohydrate-restricted ketogenic diet. Further investigations are necessary to identify co-treatment modalities, e.g. glycolysis inhibitors or antiangiogenic agents that efficiently target non-oxidative pathways.