cells Review Hypoxia Dictates Metabolic Rewiring of Tumors: Implications for Chemoresistance Dimas Carolina Belisario 1, Joanna Kopecka 1 , Martina Pasino 1, Muhlis Akman 1, Enrico De Smaele 2, Massimo Donadelli 3 and Chiara Riganti 1,* 1 Department of Oncology, University of Torino, via Santena 5/bis, 10126 Torino, Italy;
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[email protected] (M.A.) 2 Department of Experimental Medicine, Sapienza University of Roma, 00185 Roma, Italy;
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[email protected]; Tel.: +39-011-670-5857 Received: 27 October 2020; Accepted: 3 December 2020; Published: 4 December 2020 Abstract: Hypoxia is a condition commonly observed in the core of solid tumors. The hypoxia- inducible factors (HIF) act as hypoxia sensors that orchestrate a coordinated response increasing the pro-survival and pro-invasive phenotype of cancer cells, and determine a broad metabolic rewiring. These events favor tumor progression and chemoresistance. The increase in glucose and amino acid uptake, glycolytic flux, and lactate production; the alterations in glutamine metabolism, tricarboxylic acid cycle, and oxidative phosphorylation; the high levels of mitochondrial reactive oxygen species; the modulation of both fatty acid synthesis and oxidation are hallmarks of the metabolic rewiring induced by hypoxia. This review discusses how metabolic-dependent factors (e.g., increased acidification of tumor microenvironment coupled with intracellular alkalinization, and reduced mitochondrial metabolism), and metabolic-independent factors (e.g., increased expression of drug efflux transporters, stemness maintenance, and epithelial-mesenchymal transition) cooperate in determining chemoresistance in hypoxia.