Enhanced immunity in a mouse model of malignant glioma is mediated by a therapeutic ketogenic diet

Abstract

BackgroundGlioblastoma multiforme is a highly aggressive brain tumor with a poor prognosis, and advances in treatment have led to only marginal increases in overall survival. We and others have shown previously that the therapeutic ketogenic diet (KD) prolongs survival in mouse models of glioma, explained by both direct tumor growth inhibition and suppression of pro-inflammatory microenvironment conditions. The aim of this study is to assess the effects of the KD on the glioma reactive immune response.MethodsThe GL261-Luc2 intracranial mouse model of glioma was used to investigate the effects of the KD on the tumor-specific immune response. Tumor-infiltrating CD8+ T cells, CD4+ T cells and natural killer (NK) cells were analyzed by flow cytometry. The expression of immune inhibitory receptors cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed death 1 (PD-1) on CD8+ T cells were also analyzed by flow cytometry. Analysis of intracellular cytokine production was used to determine production of IFN, IL-2 and IFN- in tumor-infiltrating CD8+ T and natural killer (NK) cells and IL-10 production by T regulatory cells.ResultsWe demonstrate that mice fed the KD had increased tumor-reactive innate and adaptive immune responses, including increased cytokine production and cytolysis via tumor-reactive CD8+ T cells. Additionally, we saw that mice maintained on the KD had increased CD4 infiltration, while T regulatory cell numbers stayed consistent. Lastly, mice fed the KD had a significant reduction in immune inhibitory receptor expression as well as decreased inhibitory ligand expression on glioma cells.ConclusionsThe KD may work in part as an immune adjuvant, boosting tumor-reactive immune responses in the microenvironment by alleviating immune suppression. This evidence suggests that the KD increases tumor-reactive immune responses, and may have implications in combinational treatment approaches.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2337-7) contains supplementary material, which is available to authorized users.

Tumor Metabolism, the Ketogenic Diet and β-Hydroxybutyrate: Novel Approaches to Adjuvant Brain Tumor Therapy

“…Finally, ketones and the KD have been shown to affect the immune system (Kim D. Y. et al, 2012; Husain et al, 2013; Rahman et al, 2014; Youm et al, 2015), and we have shown that the KD also reverses tumor-mediated immune suppression in a mouse model of malignant glioma (Lussier et al, 2016). As radiation-induced tumor killing is known to expose the immune system to a greater diversity of tumor antigens, it is possible that the KD as an adjuvant works to augment the effect of radiation in part by enhancing immunity against GBM.…”

“…D’Agostino and co-workers have added hyperbaric oxygen and ketone supplementation to demonstrate reduced tumor cell growth and metastatic spread in the VM metastatic tumor model (Poff et al, 2014, 2015). We used the syngeneic intracranial GL261-luc/albino C57/Bl6 model to demonstrate that CR was not necessary for the anti-tumor effects of the KD (Stafford et al, 2010), particularly when a 4:1 fat:carbohydrate plus protein formulation is used (Scheck et al, 2012; Woolf et al, 2015; Lussier et al, 2016). Recently Martuscello et al (2016) demonstrated inhibition of glioma stem cell growth in vitro and in vivo through the use of a supplemented high fat low carbohydrate diet.…”

Glioblastoma utilizes fatty acids and ketone bodies for growth allowing progression during ketogenic diet therapy

“…Our study shows that as glucose levels are diminished, GBM cells can adapt by at least partially shifting their metabolism to accommodate ketone body oxidation. Prior animal studies investigating the therapeutic potential of the KD have yielded mixed results, usually depending on the manner of administration and ability to achieve ketosis 18,20,49,50 . One study using U87 cells in a mouse tumor model found that an ad libitum KD resulted in increased blood ketone levels without affecting blood glucose or tumor growth 20 .…”

Beneficial Effects of Ketogenic Diets for Cancer Patients – A Realist Review With Focus on Evidence and Confirmation

“…Another seven animal studies [72][73][74][75][76][77][78] and nine human studies [79][80][81][82][83][84][85][86][87] were identified by the secondary search process. Subsequently, 14 animal studies were excluded because they either initiated the KD prior to tumor cell injection [41,43,66,67], had no control group [44] or because they basically replicated the results of a previously published tumor model system ( [37,38,73] replicated [36], [74] replicated [42], [57] replicated [75], [59] replicated [51], [78] replicated [56], and [60,65] replicated [45,47]). A flow chart of the search process is given in Figure 1.…”