The ketogenic diet induces epigenetic changes that impact on the expression of microRNAs and chromatin modifying enzymes that play key roles in tumour development

Presented at BNOS June 2016

Jessica Preston 1; Julianna Stylianou 1, Quingyu Zeng 1, Sophie Glover 1, Kevin O’Neill 1; Adrienne C. Scheck 2; Eric C. Woolf 2, Nelofer Syed 1;

1: John Fulcher Molecular Neuro-Oncology Laboratory, BTRC, Imperial College, London, UK,
2: Neuro-Oncology Research, Barrow Neurological Institute, Phoenix, Arizona

Abstract

Glioblastoma Multiforme (GBM) is the most aggressive form of primary brain tumour, with a median survival time of just 14 months. Current therapies are relatively ineffective, and the inherent heterogeneity of these tumours reduces the efficacy of targeted therapies since the target is often not present on all tumour cells. Due to the limited effectiveness of current and novel targeted therapeutic approaches, alternative strategies are being sought out. An attractive strategy is to exploit the altered metabolism exhibited by virtually all tumour cells ie their high dependence on glucose for survival. This can be accomplished using the therapeutic ketogenic diet.

The ketogenic diet (KD), is a high fat, low carbohydrate and adequate protein diet. This diet is used for the clinical management of refractory paediatric epilepsy has been shown to extend survival in a number of animal models of glioma. Furthermore, studies using the GL261-luc2 syngeneic intracranial model of malignant glioma also highlighted the ability of the KD to potentiate the effects of chemotherapy and radiotherapy.

In an attempt to unravel the mechanistic basis for these observed responses, we profiled tumours from mice fed either a KD or standard diet for epigenetic changes, namely changes in the expression of microRNAs (miRNAs) by global miRNA sequencing as well as changes in the expression of chromatin modifying enzymes using the mouse epigenetic chromatin modification enzyme PCR array from Qiagen.

Our results highlighted a general upregulation of microRNAs with a tumour suppressor function in tumours from animals fed a KD verses those fed a standard diet, eg. miR-138-1-5p, miR-204-5p and several members of the mmu-let-7 family. Interestingly, a number of these miRNAs have been implicated in chemotherapy and radiotherapy resistance in several cancer types, including GBM. Furthermore, we observed significant changes in chromatin modifying enzymes, namely DNMT3b, a de novo methylating enzyme and PRMT8, a protein arginine methylating enzyme in animals fed the KD.

Taken together our results suggest that the KD could inhibit tumour growth and contribute to therapy sensitivity through epigenetic modifications that impact on the regulation of genes critical for tumour survival.