Epithelial Mesenchymal Transition Induces Aberrant Glycosylation through Hexosamine Biosynthetic Pathway Activation

Abstract

Deregulated cellular metabolism is a hallmark of tumors. Cancer cells increase glucose and glutamine flux to provide energy needs and macromolecular synthesis demands. Several studies have been focused on the importance of glycolysis and pentose phosphate pathway. However, a neglected but very important branch of glucose metabolism is the hexosamine biosynthesis pathway (HBP). The HBP is a branch of the glucose metabolic pathway that consumes ϳ2-5% of the total glucose, generating UDP-GlcNAc as the end product. UDP-GlcNAc is the donor substrate used in multiple glycosylation reactions. Thus, HBP links the altered metabolism with aberrant glycosylation providing a mechanism for cancer cells to sense and respond to microenvironment changes. Here, we investigate the changes of glucose metabolism during epithelial mesenchymal transition (EMT) and the role of O-GlcNAcylation in this process. We show that A549 cells increase glucose uptake during EMT, but instead of increasing the glycolysis and pentose phosphate pathway, the glucose is shunted through the HBP. The activation of HBP induces an aberrant cell surface glycosylation and O-GlcNAcylation. The cell surface glycans display an increase of sialylation ␣2-6, poly-LacNAc, and fucosylation, all known epitopes found in different tumor models. In addition, modulation of O-GlcNAc levels was demonstrated to be important during the EMT process. Taken together, our results indicate that EMT is an applicable model to study metabolic and glycophenotype changes during carcinogenesis, suggesting that cell glycosylation senses metabolic changes and modulates cell plasticity.Altered metabolism represents the first known difference between cancer cells and normal cells (1). The Warburg effect consists of an increase of glucose uptake for producing energy by a high rate of glycolysis followed by lactic acid fermentation even under high oxygen tension ("aerobic glycolysis"). Understanding the metabolism of tumors remains a topic of intense study with important therapeutic potential (2, 3). Several advances in cancer metabolism research over past years have enhanced our understanding of how aerobic glycolysis and other metabolic shifts support the anabolic demands of high growth rate (4). Traditionally, the study of glucose metabolism usually focused on the use of glucose for energy needs. However, cancer cells use glucose in anabolic pathways that provide precursors for the synthesis of lipids, proteins, glycans, and DNA to satisfy the demands of growth and proliferation. Several studies have been focused on the importance of the pentose phosphate pathway (PPP), 3 to generate NADPH that ensures the antioxidant defenses of the cell and to generate the nucleotides in high demand or the use of intermediates of the glycolytic pathway to generate molecules such as lipids or amino acids (5). However, a neglected but integral branch of glucose metabolism is the hexosamine biosynthesis pathway (HBP).Approximately 2-5% of glucose influx is directed to the HBP by the rate-limiting enzyme ...

Cellular glycosylation senses metabolic changes and modulates cell plasticity during epithelial to mesenchymal transition

“…Another recent paper showed that Snail regulates glycolytic activity by suppressing transcription of PFKP, which directs the glucose flux toward the PPP (Kim et al, 2017). Although the authors have noticed that this metabolic regulation of PFKP occurs independently of EMT program, we showed a decreased level of PFKP enzyme during EMT (Lucena et al, 2016). Although the authors have noticed that this metabolic regulation of PFKP occurs independently of EMT program, we showed a decreased level of PFKP enzyme during EMT (Lucena et al, 2016).…”

“…In general, cancer cells during EMT enhance glycolysis and glucose uptake. 1) (Lucena et al, 2016). Kondaveeti and colleagues showed an increase in glycolysis and a decrease in gluconeogenesis during EMT using two different breast cancer cell lines (Kondaveeti et al, 2015).…”

O-GlcNAcylation in Cancer Biology: Linking Metabolism and Signaling

“…In addition, the actin binding protein cofilin is O-GlcNAcylated, which is required for its proper localization to invadopodia of breast cancer cells and contributes to breast cancer cell invasion 68 . Recent studies have shown that EMT in lung cancer cells increases flux through the HBP and increases O-GlcnAcylation 69 . These data indicate possible crosstalk between O-GlcNAcylation and EMT programs that may contribute to fine-tuning cancer cell invasion.…”

TGF-β1 Induces EMT in Bovine Mammary Epithelial Cells Through the TGFβ1/Smad Signaling Pathway

“…During EMT, epithelial cells acquire certain characteristics of the stromal cells around them, as seen by the loss of epithelial polarity and the acquisition of stromal features, including a stromal-like appearance, and vimentin, snail, and osteopontin expression [10, 11]. Epithelial cells often change from a cobblestone-shape to a spindle-shape, the level of E-cadherin decreases, and those of vimentin, α-SMA, and fibronectin increase; after EMT, epithelial cells show functional similarity to fibroblasts.…”