Targeting brain tumor stem cells by interfering with choline metabolism: Evidence for an EMT-choline oncometabolic network

Abstract

Glioblastoma (GBM) is the most lethal primary malignant brain tumor with a median survival of less than two years. High levels of therapy resistance, strong cellular invasiveness and rapid cell growth demand aggressive multimodal therapies involving resection as well as radio-chemotherapy. Recent evidence has pointed to the existence of brain tumor stem cells (BTSCs), a subpopulation of human brain tumors which is thought to be responsible for tumor dissemination, relapse and chemo resistance. BTSCs have been associated with the expression of mesenchymal features as a result of epithelial-mesenchymal transition (EMT). Using high resolution proton nuclear magnetic resonance spectroscopy (1H NMR) we compared the intracellular metabolic composition of GBM cells after induction vs. inhibition of EMT as well as under stem cell or differentiated conditions. We identified that both EMT and enrichment for stemness induces the cholinic phenotype which is characterized by high intracellular levels of phosphocholine and total choline derivatives. Furthermore, interference with choline metabolism by targeting choline kinase alpha (CHKα) reversed EMT in GBM cells as we observed reduced invasiveness, clonogenicity, and expression of EMT associated genes. Taken together, interfering with choline metabolism is a powerful strategy to suppress EMT and thus target BTSCs. Moreover, the newly identified BTSC-oncometabolic network could be used to non-invasively monitor the invasive properties of glioblastomas and the success of anti-BTSC therapy