Cancer-induced metabolic alterations within the microenvironment play a key role in tumor maintenance or else may be involved in carcinogenesis. Interestingly, oxidative stress could be the central core of metabolic rewiring. The reactive oxygen species (ROS) diffuse from cancer cells to stromal cells, which in turn result in oxidative stress. The oxidative stress induces a metabolic shift mainly through the activation of HIF-1 and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB). These transcription factors stimulate the angiogenesis to increase oxygen availability
[45][46], and the conversion into a perivascular niche. They trigger mitochondrial dysfunction and aerobic glycolysis, autophagy, and lysosomal degradation with the release of high-energy substrates such as pyruvate and lactate. Proliferative cancer stem cells would take up these molecules and use them for OXPHOS; yet, the reverse Warburg effect occurred
[47].
GBM-associated stromal cells (GASCs) functionally remind the cancer-associated fibroblasts (CAFs) described in the stroma of carcinomas, promoting the tumor in vivo and in vitro
[48]. Stromal cells such as non-neoplastic-astrocytes in contact with GBM could transfer mitochondrial DNA and mitochondria to the tumor cells. A recent study reported that mitochondrial transplantation, from healthy astrocytes, redirects the aerobic respiration in glioma cells, attenuates the Warburg effect, and may enhance radiosensitivity
[49]. Microglia, and macrophages, rapidly respond to alteration of the CNS homeostasis, including brain tumors. Their role in GBM biology is controversial. The depletion of microglia impairs glioma growth and invasiveness both in organotypic slice culture and in vivo tumor models
[1][51][52], while the “natural” microglia and macrophages induce the glioma cell cycle arrest and differentiation in culture
[52]. Single-cell profiling obtained combining gene expression, sequencing data, and protein levels reveal the complexity and the heterogeneity of glial cell functioning states related to GBMs. Variation in oxidative phosphorylation (OXPHOS) rate and regulation appears to be the most important contributor to the metabolic and functional heterogeneity among malignant and non-malignant cells. Of note, OXPHOS activity is correlated with both glycolysis and response to hypoxia in almost all cell types and might be responsible for adapting to environmental factors
[54]. Therefore, control of the metabolism both in cancer and host cells is a promising approach. Bioinformatic and computational studies help to disengage the complexity of the metabolism in modules
[55]. Metabolic modules comprise a conserved sequence of chemical reactions for the transformation of a defined substrate. Metabolic modules present a comprehensive summary of the major metabolic activities and fulfill the production/usage of the main classes of metabolites (nucleotides, carbohydrates, lipids, and amino acids)
[56]. Based on literature evidence, we identified eight main metabolic modules: glucose oxidation (glycolysis, GLU), anaerobic fermentation and lactate production (FER), pentose phosphate pathway (PPP), (non-essential) amino acid pool (AA) such as glutamate, OXPHOS, fatty acid oxidation (FAO), ROS production, glycogenolysis (GLYC). Each module could be analyzed separately in 3D models of GBM-neuro/glial interactions for every phase of the disease and could be integrated to form a feasible flux in the whole network. Integrated metabolic modules may help to identify the key factors for controlling the metabolism in targeted, time-dependent therapies.