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mTOR/MYC Axis Regulates O-GlcNAc Transferase Expression and O-GlcNAcylation in Breast Cancer
Journal article   Open access   Peer reviewed

mTOR/MYC Axis Regulates O-GlcNAc Transferase Expression and O-GlcNAcylation in Breast Cancer

Valerie L Sodi, Sakina Khaku, Raisa Krutilina, Luciana P Schwab, David J Vocadlo, Tiffany N Seagroves and Mauricio J Reginato
Molecular cancer research, v 13(5), pp 923-933
May 2015
PMID: 25636967
url
https://doi.org/10.1158/1541-7786.MCR-14-0536View
Published, Version of Record (VoR) Open

Abstract

TOR Serine-Threonine Kinases - metabolism Humans Cell Proliferation - physiology N-Acetylglucosaminyltransferases - genetics Mice, Transgenic Proto-Oncogene Proteins c-myc - metabolism N-Acetylglucosaminyltransferases - metabolism Breast Neoplasms - metabolism N-Acetylglucosaminyltransferases - biosynthesis Breast Neoplasms - enzymology Animals Breast Neoplasms - genetics TOR Serine-Threonine Kinases - genetics Transfection MCF-7 Cells Breast Neoplasms - pathology Cell Line, Tumor Female Mice Proto-Oncogene Proteins c-myc - genetics Apoptosis - physiology Acylation
Cancers exhibit altered metabolism characterized by increased glucose and glutamine uptake. The hexosamine biosynthetic pathway (HBP) uses glucose and glutamine, and directly contributes to O-linked-β-N-acetylglucosamine (O-GlcNAc) modifications on intracellular proteins. Multiple tumor types contain elevated total O-GlcNAcylation, in part, by increasing O-GlcNAc transferase (OGT) levels, the enzyme that catalyzes this modification. Although cancer cells require OGT for oncogenesis, it is not clear how tumor cells regulate OGT expression and O-GlcNAcylation. Here, it is shown that the PI3K-mTOR-MYC signaling pathway is required for elevation of OGT and O-GlcNAcylation in breast cancer cells. Treatment with PI3K and mTOR inhibitors reduced OGT protein expression and decreased levels of overall O-GlcNAcylation. In addition, both AKT and mTOR activation is sufficient to elevate OGT/O-GlcNAcylation. Downstream of mTOR, the oncogenic transcription factor c-MYC is required and sufficient for increased OGT protein expression in an RNA-independent manner and c-MYC regulation of OGT mechanistically requires the expression of c-MYC transcriptional target HSP90A. Finally, mammary tumor epithelial cells derived from MMTV-c-myc transgenic mice contain elevated OGT and O-GlcNAcylation and OGT inhibition in this model induces apoptosis. Thus, OGT and O-GlcNAcylation levels are elevated via activation of an mTOR/MYC cascade. Evidence indicates OGT as a therapeutic target in c-MYC-amplified cancers.

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Collaboration types
Domestic collaboration
International collaboration
Web of Science research areas
Cell Biology
Oncology
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