Targeting the Lactate Transporter MCT1 in Endothelial Cells Inhibits Lactate-Induced HIF-1 Activation and Tumor Angiogenesis

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

Metabolic control of tumor progression : contribution of glycolysis and monocarboxylate transporter 1 to tumor angiogenesis and tumor cell migration

Cancer development is a multistep evolutionary process. On a temporal scale, the onset of hypoxia is an early event initially affecting tumor cells outgrowing their oxygen supply. It imposes a selection pressure promoting three main adaptations: (1) a glycolytic switch corresponding to uncoupling glycolysis from oxidative phosphorylation of the TCA cycle, thereby allowing oxygen-independent ATP production and further promoting cell proliferation; (2) an angiogenic switch corresponding to the initiation of vascular extension from preexisting blood vessels; and (3) a metastatic switch during which some cancer cells acquire the phenotypic characteristics necessary to escape from the primary tumor in order to colonize distant organs. In this thesis we hypothesized the existence of a necessary coordination between these three events, and focused on the influence of glycolysis on tumor angiogenesis and tumor cell migration. More particularly, we tested whether tumor progression could be promoted by lactate, the end-product of glycolysis, and monocarboxylate transporter 1 (MCT1), a lactate-proton symporter that primarily facilitates lactate uptake by tumor cells. We first found that glycolysis promotes tumor angiogenesis. Indeed, we documented that lactate is a pro-angiogenic agent that can activate the transcription factor hypoxia-inducible factor-1 (HIF-1) in tumor and in endothelial cells. In these cells, lactate competes with 2-oxoglutarate to inhibit prolylhydroxylase-2 (PHD2), an enzyme normally inactivating HIF-1 under normoxia. Consequently, lactate activates several HIF-1-driven pro-angiogenic pathways in normoxic tumor and endothelial cells, thus mimicking hypoxia at distance from hypoxic sites. Based on this new knowledge, we evidenced that lactate signaling can be blocked when targeting MCT1, resulting in decreased tumor angiogenesis and tumor growth in vivo. MCT1 inhibitors simultaneously exert antimetabolic and anti-angiogenic effects, underlying the druggability of this pathway. We therefore studied the influence of the tumor microenvironment on the regulation of MCT1 and of its chaperone protein CD147/basigin, itself involved in the aggressive malignant phenotype. We found that glucose deprivation posttranslationally stabilizes MCT1-CD147 heterocomplexes at the plasma membrane of tumor cells, including in F-actin-positive cell protrusions normally involved in tumor cell migration. While on the one hand the response was evidenced to originate from a mitochondrial activity associated to the generation of reactive oxygen species (ROS), on the other hand MCT1-CD147 was shown to promote tumor cell migration towards glucose. Hence, the use of antioxidants but also importantly the pharmacological inhibition of MCT1 prevented the migration of glucose-starved tumor cells, making MCT1 inhibitors suitable antimigratory/antimetastatic drugs. From a translational point of view, our thesis work demonstrates that, in addition to its well-known antimetabolic effects, MCT1 inhibition exerts anti-angiogenic and antimigratory activities in tumors. The multimodal function of the transporter in tumors and its limited contribution to normal tissue physiology offers clinical relevance for the development of new, specific MCT1 inhibitors.(BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 201

Lactate activates HIF-1 in oxidative but not in Warburg-phenotype human tumor cells

Cancer can be envisioned as a metabolic disease driven by pressure selection and intercellular cooperativeness. Together with anaerobic glycolysis, the Warburg effect, formally corresponding to uncoupling glycolysis from oxidative phosphorylation, directly participates in cancer aggressiveness, supporting both tumor progression and dissemination. The transcription factor hypoxia-inducible factor-1 (HIF-1) is a key contributor to glycolysis. It stimulates the expression of glycolytic transporters and enzymes supporting high rate of glycolysis. In this study, we addressed the reverse possibility of a metabolic control of HIF-1 in tumor cells. We report that lactate, the end-product of glycolysis, inhibits prolylhydroxylase 2 activity and activates HIF-1 in normoxic oxidative tumor cells but not in Warburg-phenotype tumor cells which also expressed lower basal levels of HIF-1. These data were confirmed using genotypically matched oxidative and mitochondria-depleted glycolytic tumor cells as well as several different wild-type human tumor cell lines of either metabolic phenotype. Lactate activates HIF-1 and triggers tumor angiogenesis and tumor growth in vivo, an activity that we found to be under the specific upstream control of the lactate transporter monocarboxylate transporter 1 (MCT1) expressed in tumor cells. Because MCT1 also gates lactate-fueled tumor cell respiration and mediates pro-angiogenic lactate signaling in endothelial cells, MCT1 inhibition is confirmed as an attractive anticancer strategy in which a single drug may target multiple tumor-promoting pathways

Optimization of tumor radiotherapy with modulators of cell metabolism: towards clinical applications

Most solid tumors are characterized by oxygen instabilities creating regions of hypoxia that are detrimental to radiotherapy. Because after surgery radiotherapy alone or in combination with other interventions is a first-line treatment for many malignancies, strategies aimed at increasing the tumor pO2 homogeneously in tumors have been the focus of intense research over the last decades. Among other approaches having proved preclinical and/or clinical utility, those targeting tumor metabolism in order redirect oxygen from a metabolic fate to the stabilization of radiation-induced DNA damage are highly relevant. They include heat therapy (hyperthermia and hypothermia), drugs targeting glucose and lactate metabolism, nitric oxide donors and inducers, anti-inflammatory drugs, and mitogen-activated protein kinase (MAPK) pathway inhibitors. While many of these drugs and interventions are in clinical use often for other pathologies than cancer, their utility as adjuvant treatments with radiotherapy has been proven preclinically, which should foster their clinical evaluation

Lactate stimulates angiogenesis and accelerates the healing of superficial and ischemic wounds in mice.

Wounds notoriously accumulate lactate as a consequence of both anaerobic and aerobic glycolysis following microcirculation disruption, immune activation, and increased cell proliferation. Several pieces of evidence suggest that lactate actively participates in the healing process through the activation of several molecular pathways that collectively promote angiogenesis. Lactate indeed stimulates endothelial cell migration and tube formation in vitro, as well as the recruitment of circulating vascular progenitor cells and vascular morphogenesis in vivo. In this study, we examined whether the pro-angiogenic potential of lactate may be exploited therapeutically to accelerate wound healing. We show that lactate delivered from a Matrigel matrix improves reperfusion and opposes muscular atrophy in ischemic hindlimb wounds in mice. Both responses involve lactate-induced reparative angiogenesis. Using microdialysis and enzymatic measurements, we found that, contrary to poly-L-lactide (PLA), a subcutaneous implant of poly-D,L-lactide-co-glycolide (PLGA) allows sustained local and systemic lactate release. PLGA promoted angiogenesis and accelerated the closure of excisional skin wounds in different mouse strains. This polymer is FDA-approved for other applications, emphasizing the possibility of exploiting PLGA therapeutically to improve wound healing

Cancer : lorsque recycler devient une faiblesse

À l’origine du processus cancéreux, les descendants d’une cellule capable de proliférer de manière débridée envahissent le tissu d’origine pour former une masse tumorale de volume croissant (Figure 1). Or, à distance du vaisseau sanguin le plus proche, l’oxygène nécessaire à la chaîne respiratoire cellulaire (phosphorylations oxydatives) s’amenuise. Un équilibre dynamique s’installe donc entre la prolifération des cellules recevant suffisamment d’oxygène et la mort des cellules hypoxiques, ce qui favorise l’élimination naturelle des microlésions tumorales. Toutefois, l’hypoxie favorise aussi l’émergence de cellules cancéreuses capables de produire la majorité de leur énergie par la glycolyse plutôt que par la chaîne respiratoire. Cette adaptation et sa pérennisation permettent à la tumeur d’entrer en phase de croissance exponentielle