gms | German Medical Science

Objective: The Impact of microenvironmental compositions strongly effects tumor cell metabolism and results in transcriptional reprogramming of glioma stem cells (GSC). This effect leads to intratumoral heterogeneity and varying susceptibility to tumor treatment with an overall poor prognosis for GBM patients. This study aimed to uncover the microenvironmental impact on infiltrating tumor cells and their transcriptional adaptation.

Methods: Metabolic and transcriptional profiles of multiple biopsies (n=35) of three patients were generated and analyzed by a comprehensive bioinformatical approach. Results were transformed into a cell-model (patient-derived GSC) to simulate multiple microenvironmental conditions and to investigate their impact on metabolic and transcriptional changes (RNA-seq and metabolic profiling). Findings were validated by isolating microenvironmental astrocytes (HepaCAM), oligodendrocytes (GalC) and myloide cells (CD45) by immunopanning of the tumor core and normal brain specimens followed by RNA-seq and proteomic profiling.

Results: In a first step, analysis revealed enhanced creatine concentrations in proneural cells of the infiltrative region. In contrast, mesenchymal cells from the tumor core showed relatively low concentrations of creatine but high lactate levels. In GSC cultures analysis of creatine metabolism suggested and up-regulation of the glycine-cleavage system and monocarbon-metabolism. This resulted in an increase of antioxidant components such as glutathione. A significant reduction of reactive oxygen species was detected followed by an activation of the Prolyl-Hydroxylase Domain (PHD). Additionally, chemical hypoxia was rescued by inversion of the alpha-ketoglutarate/succinate ratio. Therefrom, HIF1α-destabilization was shown to promote transcriptional adaptation and lead to increased chemotherapy resistance. Analysis of the cellular microenvironment identified oligodendrocytes of the infiltrating regions as main drivers of the creatine synthesis resulting in a creatine-rich environment.

Conclusion: The present study reports an adaptive mechanism in which the metabolic environment of malignant glioma drives transcriptional reprogramming. Tumor cells in the infiltrating regions showed a distinct transcriptional profile and increased resistance to hypoxia and chemotherapy. These findings open new aspects for targeted tumor therapy in the future.