Increased sugar uptake promotes oncogenesis via EPAC/RAP1 and O-GlcNAc pathways
Yasuhito Onodera, Jin-Min Nam, Mina J. Bissell
Yasuhito Onodera, Jin-Min Nam, Mina J. Bissell
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Research Article Oncology

Increased sugar uptake promotes oncogenesis via EPAC/RAP1 and O-GlcNAc pathways

Abstract

There is a considerable resurgence of interest in the role of aerobic glycolysis in cancer; however, increased glycolysis is frequently viewed as a consequence of oncogenic events that drive malignant cell growth and survival. Here we provide evidence that increased glycolytic activation itself can be an oncogenic event in a physiologically relevant 3D culture model. Overexpression of glucose transporter type 3 (GLUT3) in nonmalignant human breast cells activated known oncogenic signaling pathways, including EGFR, β1 integrin, MEK, and AKT, leading to loss of tissue polarity and increased growth. Conversely, reduction of glucose uptake in malignant cells promoted the formation of organized and growth-arrested structures with basal polarity, and suppressed oncogenic pathways. Unexpectedly and importantly, we found that unlike reported literature, in 3D the differences between “normal” and malignant phenotypes could not be explained by HIF-1α/2α, AMPK, or mTOR pathways. Loss of epithelial integrity involved activation of RAP1 via exchange protein directly activated by cAMP (EPAC), involving also O-linked N-acetylglucosamine modification downstream of the hexosamine biosynthetic pathway. The former, in turn, was mediated by pyruvate kinase M2 (PKM2) interaction with soluble adenylyl cyclase. Our findings show that increased glucose uptake activates known oncogenic pathways to induce malignant phenotype, and provide possible targets for diagnosis and therapeutics.

Authors

Yasuhito Onodera, Jin-Min Nam, Mina J. Bissell

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Figure 12

Reciprocal interactions between increased glucose uptake/metabolism and other signaling pathways.

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Reciprocal interactions between increased glucose uptake/metabolism and ...
Extracellular glucose is taken up by glucose transporters, including GLUT3, as well as by diffusion and is metabolized by hexokinase (HK) and glucose-6-phosphate isomerase (GPI) to enter different metabolic pathways. The glycolytic pathway includes subsequent steps mediated by PFK, ALDO, and GAPDH; LDH also supports the glycolytic pathway by production of the GAPDH coenzyme NAD+. These enzymes were all upregulated in T4-2 cells, leading to loss of integration of form and function. The sAC-EPAC-RAP1 pathway regulates β1 integrin positively, most likely via a direct link between ATP production in the glycolytic pathway and cAMP generation by sAC, which is mediated by tumor-specific PKM2-sAC association. HBP (dashed outline) is rate-limited by GFPT, which is also upregulated via activation of oncogenic signaling. Downstream O-GlcNAcylation of target proteins mediated by OGT regulates β1 integrin, EGFR, and GLUT3 expression. Inhibition of any of the key metabolic enzymes or the key signaling molecules results in suppression of all the others, reestablishment of the polarized acinar structure, and growth arrest. See Results and Discussion for details. Fonts distinguish metabolites (italic), proteins (bold), and genes (bold and italic). Colored text highlights proteins upregulated in T4-2 cells (orange), energy carrier molecules (green), and chemical reagents that do (red) or do not (purple) induce phenotypic reversion. 2DGP, 2DG-phosphate; G6P, glucose-6-phosphate; F1,6BP, fructiose-1,6-bisphosphate; GAD3P, glyceraldehyde-3-phosphate; DHAP, dihydroxyacetone phosphate; 1,3BPG, 1,3-bisphosphoglycerate; GlcNAc, N-acetylglucosamine.