Identification of ATP citrate lyase as a positive regulator of glycolytic function in glioblastomas

Authors

  • Marie E. Beckner,

    Corresponding author
    1. Department of Pathology, University of Pittsburgh, Pittsburgh, PA
    Current affiliation:
    1. Department of Pathology, Louisiana State University Health Sciences Center—Shreveport, Shreveport, LA
    • Department of Pathology, Room C2-26, Molecular Pathology Laboratory, Louisiana State University HSC—Shreveport, 1541 Kings Highway, Shreveport, LA 71130
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    • Tel: 318-675-7732, Fax: 318-675-8395

  • Wendy Fellows-Mayle,

    1. Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA
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  • Zhe Zhang,

    1. Department of Pharmaceutical Sciences, University of Pittsburgh, Pittsburgh, PA
    Current affiliation:
    1. Department of Biochemistry, University of Missouri, Columbia, MO
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  • Naomi R. Agostino,

    1. Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA
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  • Jeffrey A. Kant,

    1. Department of Pathology, University of Pittsburgh, Pittsburgh, PA
    2. Department of Human Genetics, University of Pittsburgh, Pittsburgh, PA
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  • Billy W. Day,

    1. Department of Pharmaceutical Sciences, University of Pittsburgh, Pittsburgh, PA
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  • Ian F. Pollack

    1. Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA
    2. Children's Hospital of Pittsburgh, University of Pittsburgh, Pittsburgh, PA
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Abstract

Glioblastomas, the most malignant type of glioma, are more glycolytic than normal brain tissue. Robust migration of glioblastoma cells has been previously demonstrated under glycolytic conditions and their pseudopodia contain increased glycolytic and decreased mitochondrial enzymes. Glycolysis is suppressed by metabolic acids, including citric acid which is excluded from mitochondria during hypoxia. We postulated that glioma cells maintain glycolysis by regulating metabolic acids, especially in their pseudopodia. The enzyme that breaks down cytosolic citric acid is ATP citrate lyase (ACLY). Our identification of increased ACLY in pseudopodia of U87 glioblastoma cells on 1D gels and immunoblots prompted investigation of ACLY gene expression in gliomas for survival data and correlation with expression of ENO1, that encodes enolase 1. Queries of the NIH's REMBRANDT brain tumor database based on Affymetrix data indicated that decreased survival correlated with increased gene expression of ACLY in gliomas. Queries of gliomas and glioblastomas found an association of upregulated ACLY and ENO1 expression by chi square for all probe sets (reporters) combined and correlation for numbers of probe sets indicating shared upregulation of these genes. Real-time quantitative PCR confirmed correlation between ACLY and ENO1 in 21 glioblastomas (p < 0.001). Inhibition of ACLY with hydroxycitrate suppressed (p < 0.05) in vitro glioblastoma cell migration, clonogenicity and brain invasion under glycolytic conditions and enhanced the suppressive effects of a Met inhibitor on cell migration. In summary, gene expression data, proteomics and functional assays support ACLY as a positive regulator of glycolysis in glioblastomas.

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