Targeting the Leloir Pathway with Galactose-Based Antimetabolites in Glioblastoma.

Simple Summary: Glioblastoma (GBM) uses the Leloir pathway to catabolize D-Galactose (Gal) for tumor growth. Selective targeting of the Leloir pathway with Gal-based antimetabolites has potential for the treatment of GBM. Here, we tested the effect of a Gal-based antimetabolite, 4-deoxy-4-fluorogalactose (4DFG) on the viability and metabolism of GBM cells in culture. 4DFG is a good Glut3/Glut14 substrate and acts as a potent glioma chemotherapeutic. GBM cell cultures were used to examine toxicity and alterations in glycan composition. 4DFG is moderately potent against GBM cells in vitro (IC50: 125–300 µM). Glycosylation in GBM was disrupted by 4DFG. The effect of 4DFG on D-glucose (Glc) metabolism in GBM cells was assessed by using 13C NMR-based tracer studies. 13C-NMR-based metabolic flux analysis revealed that both glycolytic and mitochondrial metabolic fluxes of [U-13C]Glc were significantly decreased in the presence of 4DFG in GBM cells. Survival analysis in an intracranial mouse model during treatment with 4DFG (6 × 25 mg/kg of 4DFG, intravenously) showed improved outcomes by three-fold (p < 0.01). 4DFG is metabolized by GBM in vitro and in vivo, and is lethal to GBM tumors, but well tolerated in mice. A functional Gal-scavenging pathway in GBM allows Gal-based antimetabolites to act as chemotherapeutics. Background: Glioblastoma (GBM) uses Glut3 and/or Glut14 and the Leloir pathway to catabolize D-Galactose (Gal). UDP-4-deoxy-4-fluorogalactose (UDP-4DFG) is a potent inhibitor of the two key enzymes, UDP-galactose-4-epimerase (GALE) and UDP-Glucose 6-dehydrogenase (UGDH), involved in Gal metabolism and in glycan synthesis. The Gal antimetabolite 4-deoxy-4-fluorogalactose (4DFG) is a good substrate for Glut3/Glut14 and acts as a potent glioma chemotherapeutic. Methods: Primary GBM cell cultures were used to examine toxicity and alterations in glycan composition via lectin binding in fixed cells and by Western blots. Toxicity/efficacy in vivo data was performed in mouse flank and intracranial models. The effect of 4DFG on D-glucose (Glc) metabolism in GBM cells was assessed by using 13C NMR-based tracer studies. Results: 4DFG is moderately potent against GBM cells (IC50: 125–300 µM). GBM glycosylation is disrupted by 4DFG. Survival analysis in an intracranial mouse model showed that treatment with 4DFG (6 × 25 mg/kg of 4DFG, intravenously) improved outcomes by three-fold (p < 0.01). Metabolic flux analysis revealed that both glycolytic and mitochondrial metabolic fluxes of [U-13C]Glc were significantly decreased in the presence of 4DFG in GBM cells. Conclusion: A functional Gal-scavenging pathway in GBM allows Gal-based antimetabolites to act as chemotherapeutics. 4DFG is metabolized by GBM in vitro and in vivo, is lethal to GBM tumors, and is well tolerated in mice. [ABSTRACT FROM AUTHOR]