Fluorescent mouse pheochromocytoma spheroids expressing hypoxia-inducible factor 2 alpha: Morphologic and radiopharmacologic characterization

Article type: Research Article

Authors: Seifert, Verena^a | Liers, Josephine^{a; b} | Kniess, Torsten^c | Richter, Susan^{b; d} | Bechmann, Nicole^d | Feldmann, Anja^e | Bachmann, Michael^{b; e; g; h} | Eisenhofer, Graeme^{b; d; f} | Pietzsch, Jens^{a; i; 1} | Ullrich, Martin^{a; 1; *}

Affiliations: [a] Department of Radiopharmaceutical and Chemical Biology, Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Dresden, Germany | [b] Technische Universität Dresden, School of Medicine, Faculty of Medicine Carl Gustav Carus, Dresden, Germany | [c] Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Department of GMP Radiopharmaceuticals Production, Dresden, Germany | [d] Technische Universität Dresden, University Hospital Carl Gustav Carus, Institute of Clinical Chemistry and Laboratory Medicine, Dresden, Germany | [e] Department of Radioimmunology, Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Dresden, Germany | [f] Department of Internal Medicine III, Technische Universität Dresden, University Hospital Carl Gustav Carus, Dresden, Germany | [g] Technische Universität Dresden, University Hospital Carl Gustav Carus, Universitäts Krebs Centrum (UCC), Tumorimmunology, Dresden, Germany | [h] Technische Universität Dresden, National Center for Tumor Diseases (NCT), Dresden, Germany | [i] Technische Universität Dresden, School of Science, Faculty of Chemistry and Food Chemistry, Dresden, Germany

Correspondence: [*] Corresponding author: Dr. Martin Ullrich, Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Dept. of Radiopharmaceutical and Chemical Biology, Bautzner Landstraße 400, 01328 Dresden, Germany. Tel.: +49 351 2604046; E-mail: [email protected].

Note: [1] These authors contributed equally to this work.

Abstract: BACKGROUND:Pheochromocytomas and paragangliomas (PPGLs) are rare catecholamine-producing tumors arising from chromaffin tissue. In a PPGL subgroup, dysregulation of hypoxia signaling pathways, in particular mediated through stabilization of hypoxia-inducible factor 2 alpha (HIF2α), have been suggested to drive tumorigenesis through altering downstream transcriptional activity. OBJECTIVE:This study evaluated the use of mCherry-transgenic mouse pheochromocytoma (MPCmCherry) spheroids as in vitro models for investigating consequences of HIF2α expression on aggregation behavior, morphology, growth, glucose consumption, amino acid uptake, and somatostatin type 2 receptors under stable hypoxic conditions. METHODS:MPCmCherry spheroids were monitored using confocal laser scanning microscopy. Hypoxic regions were detected using pimonidazole. Radiotracer incubation was performed using 2-[18F]fluoro-2-deoxyglucose ([18F]FDG), O-3-(2[18F]fluoroethoxy)-4-hydroxyphenylalanine ([18F]OFED), and [68Ga]Ga-(Tyr3)octreotate ([68Ga]Ga-DOTA-TATE). RESULTS:Both HIF2α-expressing and empty vector (EV) control spheroids showed regions of stable cellular hypoxia. Expression of HIF2α in MPCmCherry spheroids was associated with less symmetric morphology, faster growth, and decreased uptake of [68Ga]Ga-DOTA-TATE (somatostatin type 2 receptors) compared to controls, whereas, uptake of [18F]FDG (glucose transporter 1 and hexokinases) and [18F]OFED (system L amino acid transporter 1) remained unaffected. CONCLUSIONS:The recent study proved MPCmCherry spheroids to be complex three-dimensional tumor cell models for investigating morphologic and metabolic consequences of dysregulated hypoxia pathways under hypoxic conditions.

Keywords: Amino acid transporters, confocal laser scanning microscopy, neuroendocrine tumors, paraganglioma, pimonidazole, positron emitters, radiotracer uptake, somatostatin receptors

DOI: 10.3233/JCB-199005

Journal: Journal of Cellular Biotechnology, vol. 5, no. 2, pp. 135-151, 2019