CANCER RESEARCH | METABOLISM AND CHEMICAL BIOLOGY Targeting Mitochondrial Iron Metabolism Suppresses Tumor Growth and Metastasis by Inducing Mitochondrial Dysfunction and Mitophagy Cristian Sandoval-Acu~ na 1 , Natalia Torrealba 1 , Veronika Tomkova 1 , Sukanya B. Jadhav 1 , Kristyna Blazkova 1 , Ladislav Merta 2 , Sandra Lettlova 1 , Miroslava K. Adamcov a 3 , Daniel Rosel 2 , Jan Br abek 2 , Jiri Neuzil 1,4 , Jan Stursa 1 , Lukas Werner 1 , and Jaroslav Truksa 1 ABSTRACT ◥ Deferoxamine (DFO) represents a widely used iron chelator for the treatment of iron overload. Here we describe the use of mitochond- rially targeted deferoxamine (mitoDFO) as a novel approach to preferentially target cancer cells. The agent showed marked cytostatic, cytotoxic, and migrastatic properties in vitro, and it significantly suppressed tumor growth and metastasis in vivo. The underlying molecular mechanisms included (i) impairment of iron-sulfur [Fe-S] cluster/heme biogenesis, leading to destabilization and loss of activity of [Fe-S] cluster/heme containing enzymes, (ii) inhibition of mito- chondrial respiration leading to mitochondrial reactive oxygen spe- cies production, resulting in dysfunctional mitochondria with markedly reduced supercomplexes, and (iii) fragmentation of the mitochondrial network and induction of mitophagy. Mitochondrial targeting of deferoxamine represents a way to deprive cancer cells of biologically active iron, which is incompatible with their proliferation and invasion, without disrupting systemic iron metabolism. Our findings highlight the importance of mitochondrial iron metabolism for cancer cells and demonstrate repurposing deferoxamine into an effective anticancer drug via mitochondrial targeting. Significance: These findings show that targeting the iron chelator deferoxamine to mitochondria impairs mitochondrial respiration and biogenesis of [Fe-S] clusters/heme in cancer cells, which suppresses proliferation and migration and induces cell death. Graphical Abstract: http://cancerres.aacrjournals.org/content/ canres/81/9/2289/F1.large.jpg. Mitochondrially targeted deferoxamine (mitoDFO) induces cancer cell death by reducing mitochondrial [Fe-S] cluster biogenesis and mitochondrial respiration. Introduction Iron represents a vital element required for almost all forms of life (1). Because of its ability to transfer electrons by shuttling between ferrous and ferric forms, it is a crucial component participating in the electron transport chain within mitochondria, in DNA repair and replication (2), chromatin remodeling and epigenetic changes (3) and cellular metabolism (4). In biological systems, iron can be incorporated into iron-sulfur [Fe-S] clusters and the heme molecule (2, 5). Both of these iron- containing structures serve as cofactors of many enzymes and are partially synthesized inside mitochondria, making it the central organ- elle in the cellular iron metabolism. At the same time, mitochondria are important for ATP production, metabolic reactions, calcium homeo- stasis, and programmed cell death (2, 4). Dysfunctional mitochondria are degraded by a specific process termed mitophagy, which is induced by iron deficiency (6, 7). Iron is crucial for the rapidly proliferating cancer cells (8) and also for the cancer stem-like cells (9). Therefore, attempts to target iron metabolism to suppress tumor growth have been made (10). In certain cancer types, such as bladder cancer, gallium nitrate has been successfully applied, competitively replacing iron (11). Other approaches including antibodies against transferrin receptor, appli- cation of iron chelators, or a combination of both approaches have shown promising results in vitro (10, 12–14). Yet, the main remain- ing drawbacks of such strategies are the nonselective nature of the treatment and the associated perturbation of the systemic iron metabolism (14). In recent years, a strategy for targeting small molecules into mitochondria via a triphenylphosphonium group (TPP þ ) proposed 1 Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV Research Center, Vestec, Czech Republic. 2 Faculty of Sciences, BIOCEV Research Center, Charles University, Vestec, Czech Republic. 3 Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic. 4 School of Medical Science, Griffith University, Southport, Queensland, Australia. Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). Current address for S. Lettlova, Institute of Clinical Chemistry, University of Zurich and University Hospital Zurich, Zurich, Switzerland. Corresponding Author: Jaroslav Truksa, Laboratory of Tumour Resistance, Institute of Biotechnology of the Czech Academy of Sciences, Pru  myslov a 595, Vestec 25250, Czech Republic. Phone: 420325873735. E-mail: jaroslav.truksa@ibt.cas.cz Cancer Res 2021;81:2289–303 doi: 10.1158/0008-5472.CAN-20-1628 Ó2021 American Association for Cancer Research. AACRJournals.org | 2289 Downloaded from http://aacrjournals.org/cancerres/article-pdf/81/9/2289/3094597/2289.pdf by guest on 23 November 2023