Article

Glucose metabolism via the pentose phosphate pathway, glycolysis and Krebs cycle in an orthotopic mouse model of human brain tumors.

Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA
NMR in Biomedicine (Impact Factor: 3.56). 03/2012; 25(10):1177-86. DOI: 10.1002/nbm.2787
Source: PubMed

ABSTRACT It has been hypothesized that increased flux through the pentose phosphate pathway (PPP) is required to support the metabolic demands of rapid malignant cell growth. Using orthotopic mouse models of human glioblastoma (GBM) and renal cell carcinoma metastatic to brain, we estimated the activity of the PPP relative to glycolysis by infusing [1,2-(13) C(2) ]glucose. The [3-(13) C]lactate/[2,3-(13) C(2) ]lactate ratio was similar for both the GBM and brain metastasis and their respective surrounding brains (GBM, 0.197 ± 0.011 and 0.195 ± 0.033, respectively (p = 1); metastasis: 0.126 and 0.119 ± 0.033, respectively). This suggests that the rate of glycolysis is significantly greater than the PPP flux in these tumors, and that the PPP flux into the lactate pool is similar in both tumors. Remarkably, (13) C-(13) C coupling was observed in molecules derived from Krebs cycle intermediates in both tumor types, denoting glucose oxidation. In the renal cell carcinoma, in contrast with GBM, (13) C multiplets of γ-aminobutyric acid (GABA) differed from its precursor glutamate, suggesting that GABA did not derive from a common glutamate precursor pool. In addition, the orthotopic renal tumor, the patient's primary renal mass and brain metastasis were all strongly immunopositive for the 67-kDa isoform of glutamate decarboxylase, as were 84% of tumors on a renal cell carcinoma tissue microarray of the same histology, suggesting that GABA synthesis is cell autonomous in at least a subset of renal cell carcinomas. Taken together, these data demonstrate that (13) C-labeled glucose can be used in orthotopic mouse models to study tumor metabolism in vivo and to ascertain new metabolic targets for cancer diagnosis and therapy. Copyright © 2012 John Wiley & Sons, Ltd.

0 Bookmarks
 · 
218 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The pentose phosphate pathway (PPP) is a fundamental component of cellular metabolism. The PPP is important to maintain carbon homoeostasis, to provide precursors for nucleotide and amino acid biosynthesis, to provide reducing molecules for anabolism, and to defeat oxidative stress. The PPP shares reactions with the Entner–Doudoroff pathway and Calvin cycle and divides into an oxidative and non-oxidative branch. The oxidative branch is highly active in most eukaryotes and converts glucose 6-phosphate into carbon dioxide, ribulose 5-phosphate and NADPH. The latter function is critical to maintain redox balance under stress situations, when cells proliferate rapidly, in ageing, and for the ‘Warburg effect’ of cancer cells. The non-oxidative branch instead is virtually ubiquitous, and metabolizes the glycolytic intermediates fructose 6-phosphate and glyceraldehyde 3-phosphate as well as sedoheptulose sugars, yielding ribose 5-phosphate for the synthesis of nucleic acids and sugar phosphate precursors for the synthesis of amino acids. Whereas the oxidative PPP is considered unidirectional, the non-oxidative branch can supply glycolysis with intermediates derived from ribose 5-phosphate and vice versa, depending on the biochemical demand. These functions require dynamic regulation of the PPP pathway that is achieved through hierarchical interactions between transcriptome, proteome and metabolome. Consequently, the biochemistry and regulation of this pathway, while still unresolved in many cases, are archetypal for the dynamics of the metabolic network of the cell. In this comprehensive article we review seminal work that led to the discovery and description of the pathway that date back now for 80 years, and address recent results about genetic and metabolic mechanisms that regulate its activity. These biochemical principles are discussed in the context of PPP deficiencies causing metabolic disease and the role of this pathway in biotechnology, bacterial and parasite infections, neurons, stem cell potency and cancer metabolism.
    Biological Reviews 09/2014; · 10.26 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Hypoxia is a common finding in advanced human tumors and is often associated with metastatic dissemination and poor prognosis. Cancer cells adapt to hypoxia by utilizing physiological adaptation pathways that promote a switch from oxidative to glycolytic metabolism. This promotes the conversion of glucose into lactate while limiting its transformation into acetyl coenzyme A (acetyl-CoA). The uptake of glucose and the glycolytic flux are increased under hypoxic conditions, mostly owing to the upregulation of genes encoding glucose transporters and glycolytic enzymes, a process that depends on hypoxia-inducible factor 1 (HIF-1). The reduced delivery of acetyl-CoA to the tricarboxylic acid cycle leads to a switch from glucose to glutamine as the major substrate for fatty acid synthesis in hypoxic cells. In addition, hypoxia induces (1) the HIF-1-dependent expression of BCL2/adenovirus E1B 19-kDa interacting protein 3 (BNIP3) and BNIP3-like (BNIP3L), which trigger mitochondrial autophagy, thereby decreasing the oxidative metabolism of both fatty acids and glucose, and (2) the expression of the sodium-hydrogen exchanger NHE1, which maintains an alkaline intracellular pH. Here, we present a compendium of methods to study hypoxia-induced metabolic alterations.
    Methods in enzymology. 01/2014; 542:425-55.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Early stage detection and precise quantification of circulating tumor cells (CTCs) in the peripheral blood of cancer patients are important for early diagnosis. Early diagnosis improves the effectiveness of the therapy and results in better prognosis. Several techniques have been used for CTC detection but are limited by their need for dye tagging, low throughput and lack of statistical reliability at single cell level. Solid-state micropores can characterize each cell in a sample providing interesting information about cellular populations. We report a multi-channel device which utilized solid-state micropores array assembly for simultaneous measurement of cell translocation. This increased the throughput of measurement and as the cells passed the micropores, tumor cells showed distinctive current blockade pulses, when compared to leukocytes. The ionic current across each micropore channel was continuously monitored and recorded. The measurement system not only increased throughput but also provided on-chip cross-relation. The whole blood was lysed to get rid of red blood cells, so the blood dilution was not needed. The approach facilitated faster processing of blood samples with tumor cell detection efficiency of about 70%. The design provided a simple and inexpensive method for rapid and reliable detection of tumor cells without any cell staining or surface functionalization. The device can also be used for high throughput electrophysiological analysis of other cell types.
    Biosensors & Bioelectronics 06/2014; 62C:343-349. · 6.45 Impact Factor

Full-text (2 Sources)

Download
17 Downloads
Available from
Jun 5, 2014