Targeting the Lactate Transporter MCT1 in Endothelial Cells Inhibits Lactate-Induced HIF-1 Activation and Tumor Angiogenesis Pierre Sonveaux1,2*, Tamara Copetti1, Christophe J. De Saedeleer1, Fre´ de´ rique Ve´ gran1, Julien Verrax1, Kelly M. Kennedy2, Eui Jung Moon4, Suveera Dhup1, Pierre Danhier3, Franc¸ oise Fre´ rart1, Bernard Gallez3, Anthony Ribeiro5, Carine Michiels6, Mark W. Dewhirst2,4., Olivier Feron1. 1 Pole of Pharmacology, Institute of Experimental and Clinical Research (IREC), Universite´ catholique de Louvain (UCL), Brussels, Belgium, 2 Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina, United States of America, 3 Nuclear Magnetic Resonance Research Group, Louvain Drug Research Institute (LDRI), Universite´ catholique de Louvain (UCL), Brussels, Belgium, 4 Department of Pathology, Duke University Medical Center, Durham, North Carolina, United States of America, 5 Department of Radiology and Biochemistry, Duke University Medical Center, Durham, North Carolina, United States of America, 6 Laboratory of Biochemistry and Cellular Biology, University of Namur (FUNDP), Namur, Belgium Abstract Switching to a glycolytic metabolism is a rapid adaptation of tumor cells to hypoxia. Although this metabolic conversion may primarily represent a rescue pathway to meet the bioenergetic and biosynthetic demands of proliferating tumor cells, it also creates a gradient of lactate that mirrors the gradient of oxygen in tumors. More than a metabolic waste, the lactate anion is known to participate to cancer aggressiveness, in part through activation of the hypoxia-inducible factor-1 (HIF-1) pathway in tumor cells. Whether lactate may also directly favor HIF-1 activation in endothelial cells (ECs) thereby offering a new druggable option to block angiogenesis is however an unanswered question. In this study, we therefore focused on the role in ECs of monocarboxylate transporter 1 (MCT1) that we previously identified to be the main facilitator of lactate uptake in cancer cells. We found that blockade of lactate influx into ECs led to inhibition of HIF-1-dependent angiogenesis. Our demonstration is based on the unprecedented characterization of lactate-induced HIF-1 activation in normoxic ECs and the consecutive increase in vascular endothelial growth factor receptor 2 (VEGFR2) and basic fibroblast growth factor (bFGF) expression. Furthermore, using a variety of functional assays including endothelial cell migration and tubulogenesis together with in vivo imaging of tumor angiogenesis through intravital microscopy and immunohistochemistry, we documented that MCT1 blockers could act as bona fide HIF-1 inhibitors leading to anti-angiogenic effects. Together with the previous demonstration of MCT1 being a key regulator of lactate exchange between tumor cells, the current study identifies MCT1 inhibition as a therapeutic modality combining antimetabolic and anti-angiogenic activities. Citation: Sonveaux P, Copetti T, De Saedeleer CJ, Ve´gran F, Verrax J, et al. (2012) Targeting the Lactate Transporter MCT1 in Endothelial Cells Inhibits Lactate- Induced HIF-1 Activation and Tumor Angiogenesis. PLoS ONE 7(3): e33418. doi:10.1371/journal.pone.0033418 Editor: Eric Deutsch, Institut Gustave Roussy, France Received November 30, 2011; Accepted February 8, 2012; Published March 13, 2012 Copyright: 2012 Sonveaux et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by grants from the European Research Council (FP7/2007–2013 European Research Council Independent Researcher Starting Grant No. 243188 TUMETABO to P. Sonveaux), the NIH/NCI (CA40355-24 and CA40355-25 to M.W. Dewhirst), the Fonds National de la Recherche Scientifique (F.R.S.-FNRS), an Action de Recherche Concerte´e from the Communaute´ Franc¸aise de Belgique (to P. Sonveaux and O. Feron), the NEOANGIO research program from the Re´gion Wallonne de Belgique (to O. Feron), the Fondation Belge contre le Cancer (200-2008 to P. Sonveaux and O. Feron), and the J. Maisin and St. Luc Foundations (to O. Feron). O. Feron is a Research Director, P. Sonveaux and B. F. Jordan are Research Associates, J. Verrax is a Postdoctoral Researcher, and P. Danhier is a Research Fellow of the F.R.S.-FNRS. C. De Saedeleer is a Te´le´vie Research Fellow. For this study, P. Sonveaux was also supported by a fellowship from the Belgian American Educational Foundation (BAEF). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: pierre.sonveaux@uclouvain.be . These authors contributed equally to this work. Introduction Solid tumors most often exhaust their oxygen supply creating tumor hypoxia [1]. Hypoxia initially triggers a key metabolic adaptation, the glycolytic switch, during which glycolysis is uncoupled from the TCA cycle and becomes the primary source of ATP production. This process is extremely fast as it initially proceeds through inhibition of the Pasteur effect, a negative feedback exerted by energy metabolites on the glycolytic flux [2]. Glycolysis is rather inefficient at producing energy, yielding only 2 ATP molecules per molecule of glucose whereas full glucose oxidation provides up to 38 ATP. Further adaptations are thus needed to support cell survival and proliferation under sustained (or repeated episodes of) hypoxia. Two main biological paths have evolved. On the one hand, tumor cells exhibit an accelerated glycolytic flux to meet their high bioenergetic and biosynthetic demands indepen- dently of oxygen but at the cost of high glucose consumption and lactate release [3–5]. On the other hand, the angiogenic switch, corresponding to the initiation of vascular extension, aims at increasing oxygen and nutrient supply to hypoxic tumor sites [6]. These two adaptations require de novo protein synthesis and share the transcription factor HIF-1 as a master regulator. PLoS ONE | www.plosone.org 1 March 2012 | Volume 7 | Issue 3 | e33418