The hexosamine biosynthetic pathway elevates posttranslational addition of O-linked β-N-acetylglucosamine (O-GlcNAc) on intracellular proteins. Cancer cells elevate total O-GlcNAcylation by increasing O-GlcNAc transferase (OGT) and/or decreasing O-GlcNAcase (OGA) levels. Reducing O-GlcNAcylation inhibits oncogenesis. Here, we demonstrate that O-GlcNAcylation regulates glycolysis in cancer cells via hypoxia-inducible factor 1 (HIF-1α) and its transcriptional target GLUT1. Reducing O-GlcNAcylation increases α-ketoglutarate, HIF-1 hydroxylation, and interaction with von Hippel-Lindau protein (pVHL), resulting in HIF-1α degradation. Reducing O-GlcNAcylation in cancer cells results in activation of endoplasmic reticulum (ER) stress and cancer cell apoptosis mediated through C/EBP homologous protein (CHOP). HIF-1α and GLUT1 are critical for OGT-mediated regulation of metabolic stress, as overexpression of stable HIF-1 or GLUT1 rescues metabolic defects. Human breast cancers with high levels of HIF-1α contain elevated OGT, and lower OGA levels correlate independently with poor patient outcome. Thus, O-GlcNAcylation regulates cancer cell metabolic reprograming and survival stress signaling via regulation of HIF-1α.

Introduction

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Here, we present evidence that O-GlcNAcylation within breast cancer cells regulates cancer cell metabolism via regulation of HIF-1α and its downstream target GLUT1. Mechanistically, we show that OGT regulates HIF-1α proteasomal degradation in a manner that is dependent on regulation of α-ketoglutarate, HIF-1α hydroxylation, and the tumor suppressor pVHL. Furthermore, decreasing O-GlcNAcylation leads to ER-mediated apoptosis in breast cancer cells. In addition, we show that human breast cancers containing high HIF-1α levels also contain elevated OGT and O-GlcNAcylation. Importantly, in overall breast cancer patients, lower OGA expression correlates with poor clinical outcome. Thus, O-GlcNAcylation serves as a critical link between the nutrient sensing and metabolic pathways that are critical for cancer cell survival via regulation of HIF-1α hydroxylation.