METABOLIC RE-PROGRAMING MEDIATES BIDIRECTIONAL SHIFT BETWEEN TRANSCRIPTIONAL SUBCLASSES AND DRIVES TUMOR HETEROGENEITY

The highly heterogeneous nature of malignant brain tumors maintains limited response to therapy and unfavorable clinical prognosis. The underlying molecular mechanisms of transcriptional re-programing that drive tumor heterogeneity are in the focus of research. This study reported an adaptive mechanism of malignant glioma in various metabolic environments, which potently drives transcriptional re-programming and tumor heterogeneity. In a first step, multiple biopsies (total n=138) were obtained from three de-novo glioblastoma multiforme patients and underwent a metabolic and transcriptional profiling. A metabolic landscape was explored marked by varying stages of hypoxia and creatine enrichment with a strong correlation to specific local transcriptional pattern. In the presence of environmental enriched creatine and GABA, the proneural expression subtype was mainly observed where lactate was found to be highly associated with the mesenchymal phenotype. In a second step, patient derived glioblastoma stem-like cells (GSC) were obtained and cultured in either hypoxia, creatine- supplemented or combined conditions for 24h and 48h. This environmental cell-model showed a synergistic effect of up-regulating the GABA signaling and a simultaneous inhibition of HIF signaling in a creatine-supplemented environment. This affected the transcriptional landscape with a shift toward a proneural subtype expression followed by a slowing of cell migration and proliferation. These findings were verified by additional HIF and GABA inhibition, which partially rescued the proneural shift. In a heterogeneous tumor, different stages of hypoxia and environmental creatine enrichment were observed, which required a permanent adaptation of the tumor to varying environmental conditions. These findings suggest that metabolic adaptation plays a major role in transcriptional heterogeneity of malignant brain tumors. Exploiting or targeting metabolic adaption could potentially serve as a future therapeutic option for malignant brain tumors.