Etude protéomique de la reprogrammation métabolique lors de la transformation tumorale des astrocytes

Metabolic reprogramming is one of the main characteristics of cancer cells that adapt their energy metabolism to promote cell survival and tumor proliferation. This reprogramming includes all metabolic, enzymatic, proteic or genetic adaptations, allowing cancer cells to create a favorable microenvironment for their survival and growth. In fact, cancer cells display an aberrant metabolic behavior generating ATP through an inefficient glycolysis pathway even in the presence of adequate oxygen supply. Recent works have shown that the genetic alterations that contribute to cancer development affect a number of oncogenic signaling pathways driving several tumor metabolic modifications that are essential for malignancy. Those changes in metabolic pathways allow cancer cells to facilitate their uptake and release of nutrients that can be transformed into building blocks for nucleotide, protein and lipid synthesis necessary for macromolecule assembly and tumor growth.We exploited the analytical potential of the 2D-DIGE (two-dimensional differential in-gel electrophoresis) quantitative proteomic analysis to characterize the proteomes of mouse astrocytes that underwent in vitro cancerous transformation, and of their normal counterparts. We aimed to identify and characterize the protein signature of those in vitro transformed cells in an attempt to understand their neoplastic behavior and the effect of transformation on metabolic processes.Metabolic reprogramming effects on enzymatic and structural protein expression as well as associated metabolites abundance were quantified. A total of 143 unique proteins were found to be affected by this transformation process. Using enzymatic activity measurements and zymography, we documented and confirmed several changes in abundance and activity of various isoenzymes likely to participate in metabolic reprogramming. We found that after transformation, the cells increase their expression of glycolytic enzymes, thus acquiring the ability to use aerobic glycolysis (Warburg effect). An increased capacity to dispose of reducing equivalents through lactate production was also documented. Major effects on carbohydrates, amino acids and nucleotides metabolic components were also observed. Conversely, the transformed cells reduced their capacity for tricarboxylic acid oxidation, for neurotransmitters (glutamate and GABA) metabolism and their expression of astroglial markers.