A Metabolomics approach towards understanding glucocorticoid-induced apoptosis of leukemic lymphoblasts

Glucocorticoids (GC) induce cell cycle arrest and cell death in certain lymphoid lineage cells and this has been exploited in the therapy of lymphoid malignancies, in particular childhood acute lymphoblastic leukemia (ALL). Because of the development of GC resistance, GCs have to be combined with intensive multi-component chemotherapy with all its adverse side effects. Improved combination therapy is, however, hampered by the still poorly understood molecular mechanisms of GC-induced apoptosis and GC resistance. Our recent studies exploiting whole genome comparative expression profiling, NMR-based metabolomics and metabolic inhibitors along with data from the literature provided increasing evidence for an involvement of GC-induced metabolic changes in these phenomena. In particular, we observed GC regulation of phosphofructokinase/fructose- biphosphatase (PFKFB2), the key regulator of glycolysis, metabolic alterations in glycolytic and energetic pathways, and a potentiating effect of 2-deoxyglucose, an inhibitor of glucose metabolism, on GC-induced apoptosis. Based on these observations, we propose the following specific aims: (i) Identification of GC-induced alterations in metabolite composition in lymphoblasts from GC-treated ALL patients as well as in ex vivo and in vitro systems of GC-induced leukemia apoptosis using NMR-based metabolomics. (ii) Bioinformatic analysis of the data derived from Specific Aim 1 in context with our whole genome comparative expression profiling results to identify GC-regulated genes controlling the observed metabolic alterations (iii) Functional analyses of the pathways incriminated in Specific Aim 2 using (a) genetic interference by conditional over-expression and/or RNAi-mediated knock-down of the GC-regulated genes responsible for the observed metabolic alterations, or (b) specific synthetic pathway inhibitors in appropriate ex vivo and in vitro ALL systems. Taken together, the proposed experiments will define the role of metabolome alterations for GC-induced apoptosis and might provide the basis for novel combinatorial approaches in the treatment of ALL.