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

Monitoring the fate of metastatic tumor cells using magnetic cell tracking approaches (MRI and EPR)

Cancer is a leading cause of death worldwide. Despite recent advances in cancer research, metastasis, the leading cause of death linked to cancer, remains poorly uncharacterized. The understanding of metastasis is rendered difficult by the extraordinary biological complexity of the process and the challenges for imaging the different steps of the metastatic cascade. The presence of metastasis dramatically affects the prognosis of patients. Improvements in cancer patients’ survival are more likely due to recent progress in early diagnosis rather than break-through therapies. Still, the development of whole body imaging methods for elucidating the metastatic process in order to finally develop specific “anti-metastatis” drugs is needed. The aim of this thesis was to implement MRI cell tracking for assessing the homing of metastatic cancer cells in distant organs. This technique relies on the visualization of cells previously labeled with MRI contrast agents. For such purpose, cells were first labeled ex vivo with superparamagnetic iron oxides, which induce signal voids on T2-, T2*-weighted images. An efficient labeling of cancer cells with iron oxides is a prerequisite step for valid MRI cell tracking studies. For this purpose, we first described the use of Electron Paramagnetic Resonance (EPR) for quantifying the intracellular iron oxide content in cells. EPR is a spectrometric technique which is used for the detection of free radical species and (super)paramagnetic molecules. The EPR technique was found to be sensitive and reliable compared to standard iron quantification methods such as inductively coupled plasma mass spectroscopy (ICP-MS). The specificity of EPR for iron oxides quantification is another advantage as measurements are not affected by endogenous iron. The ability of MRI to track iron oxide-labeled renal cancer cells after injection was next questioned. Bioluminescence imaging (BLI) was also used to track cancer cells as these cells stably expressed the luciferase reporter protein. It was found that labeled cancer cells entrapped in the liver could not be visualized on T2-,T2*-weighted images, whereas ex vivo EPR measurements confirmed the presence of iron oxides in this organ. Moreover, the dilution of the intracellular iron oxide content with cell division was shown to limit the monitorable period. On the other hand, BLI was shown to assess accurately the late colonization of organs by cancer cells. Third, it was aimed to image the homing of breast cancer cells in the mouse brain. MRI was found to be sensitive to detect iron oxide-labeled cells in the brain parenchyma and the complementary role of ex vivo EPR to quantify the number of iron oxide-labeled cells in MRI cell tracking studies was highlighted. Last, the impact of cell detachment, a feature associated with cancer progression, on cell metabolism was investigated. It was found that mitochondrial respiration was severely impaired upon detachment. At the same time, the ATP content was decreased and the ratio between the lactate produced and the glucose consumed was increased, suggesting a glycolytic compensation for OXPHOS defects. Conclusively, magnetic labeling approaches (EPR and MRI) hold promises in preclinical models for assessing brain metastasis development from the initial entrapment of tumor cells. However, reporter gene-based methods such as BLI remain necessary for the long-term assessment of the fate of metastatic cells.(BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 201

Anticancer drug-loaded hydrogels as drug delivery systems for the local treatment of glioblastoma.

Among central nervous system tumors, Glioblastoma (GBM) is the most common, aggressive and neurological destructive primary brain tumor in adults. Standard care therapy for GBM consists in surgical resection of the accessible tumor (without causing neurological damage) followed by chemoradiation. However, several obstacles limit the assessment of tumor response and the delivery of cytotoxic agents at the tumor site, leading to a lack of effectiveness of conventional treatments against GBM and fatal outcome. Despite the efforts of the scientific community to increase the long-term benefits of GBM therapy, at the moment GBM remains incurable. Among the strategies that have been adopted in the last two decades to find new and efficacious therapies for the treatment of GBM, the local delivery of chemotherapeutic drugs in the tumor resection cavity emerged. In this review, our aim is to provide an overview on hydrogels loaded with anticancer drugs for the treatment of GBM recently used in preclinical and clinical studies, their advantages and major limitations for clinical translation. This review is divided in three parts: the first one describes the context of GBM and its current treatments, with a highlight on the role of local delivery in GBM treatment and the development of GBM resection murine models. Then, recent developments in the use of anticancer drug-loaded hydrogels for the treatment of GBM will be detailed. The final section will be focused on the limitations for in vivo studies, clinical translation and the clinical perspectives to the development of hydrogels

Electron paramagnetic resonance: a powerful tool to support magnetic resonance imaging research

The purpose of this paper is to describe some of the areas where electron paramagnetic resonance (EPR) has provided unique information to MRI developments. The field of application mainly encompasses the EPR characterization of MRI paramagnetic contrast agents (gadolinium and manganese chelates, nitroxides) and superparamagnetic agents (iron oxide particles). The combined use of MRI and EPR has also been used to qualify or disqualify sources of contrast in MRI. Illustrative examples are presented with attempts to qualify oxygen sensitive contrast (i.e. T1 - and T2 *-based methods), redox status or melanin content in tissues. Other areas are likely to benefit from the combined EPR/MRI approach, namely cell tracking studies. Finally, the combination of EPR and MRI studies on the same models provides invaluable data regarding tissue oxygenation, hemodynamics and energetics. Our description will be illustrative rather than exhaustive to give to the readers a flavour of 'what EPR can do for MRI'

Tumor targeting by RGD-grafted PLGA-based nanotheranostics loaded with Paclitaxel and superparamagnetic iron oxides

Theranostic nanoparticles have the potential to revolutionize cancer diagnosis and therapy. Many groups have demonstrated differential levels of tumor growth between tumors treated by targeted or untargeted nanoparticles; however, only few have shown in vivo efficacy in both therapeutic and diagnostic approach. Herein, we first develop and characterize dual-paclitaxel (PTX)/superparamagnetic iron oxide (SPIO)-loaded PLGA-based nanoparticles grafted with the RGD peptide, for a theranostic purpose. Second, we compare in vivo different strategies in terms of targeting capabilities: (1) passive targeting via the EPR effect, (2) active targeting of αvβ3 integrin via RGD grafting, (3) magnetic guidance via a magnet placed on the tumor, and (4) the combination of the magnetic guidance and the active targeting of αvβ3 integrin. In this chapter, we present the general flowchart applied for this project: (1) the polymer and SPIO synthesis, (2) the physicochemical characterization of the nanoparticles, (3) the magnetic properties of the nanoparticles, and (4) the in vivo evaluation of the nanoparticles for their therapeutic and diagnosis purposes. We employ the electron spin resonance spectroscopy and magnetic resonance imaging to both quantify and visualize the accumulation of theranostic nanoparticles into the tumors