Cancer stem cells (CSCs) represent a subset of cells within tumours that exhibit self-renewal properties and the capacity to seed tumours. CSCs are typically refractory to conventional treatments and have been associated to metastasis and relapse. Salinomycin operates as a selective agent against CSCs through mechanisms that remain elusive. Here, we provide evidence that a synthetic derivative of salinomycin, which we named ironomycin (AM5), exhibits a more potent and selective activity against breast CSCs in vitro and in vivo, by accumulating and sequestering iron in lysosomes. In response to the ensuing cytoplasmic depletion of iron, cells triggered the degradation of ferritin in lysosomes, leading to further iron loading in this organelle. Iron-mediated production of reactive oxygen species promoted lysosomal membrane permeabilization, activating a cell death pathway consistent with ferroptosis. These findings reveal the prevalence of iron homeostasis in breast CSCs, pointing towards iron and iron-mediated processes as potential targets against these cells.
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Nieto, M. N., Huang, R. Y.-J., Jackson, R. A. & Thiery, J. P. EMT: 2016. Cell 166, 21–45 (2016).
Tam, W. L. & Weinberg, R. A. The epigenetics of epithelial-mesenchymal plasticity in cancer. Nat. Med. 19, 1438–1449 (2013).
Pattabiraman, D. R. & Weinberg, R. A. Tackling the cancer stem cells–what challenges do they pose? Nature Rev. Drug Discov. 13, 497–512 (2014).
Kelly, P. N., Dakic, A., Adams, J. M., Nutt, S. L. & Strasser, A. Tumor growth need not be driven by rare cancer stem cells. Science 317, 337 (2007).
Quintana, E. et al. Efficient tumour formation by single melanoma cells. Nature 456, 593–598 (2008).
Gupta, P. B. et al. Identification of selective inhibitors of cancer stem cells by high-throughput screening. Cell 138, 645–659 (2009).
Morel, A.-P. et al. Generation of breast cancer stem cells through epithelial–mesenchymal transition. PLoS ONE 3, e2888 (2008).
Germain, A. R. et al. Identification of a selective small molecule inhibitor of breast cancer stem cells. Bioorg. Med. Chem. Lett. 22, 3571–3574 (2012).
Hartwell, K. A. et al. Niche-based screening identifies small-molecule inhibitors of leukemia stem cells. Nat. Chem. Biol. 9, 840–848 (2013).
Paulus, E. F., Kurz, M., Matter, H. & Vértesy, L. Solid-state and solution structure of the salinomycin-sodium complex: stabilization of different conformers for an ionophore in different environments. J. Am. Chem. Soc. 120, 8209–8221 (1998).
Lu, D. et al. Salinomycin inhibits Wnt signaling and selectively induces apoptosis in chronic lymphocytic leukemia cells. Proc. Natl Acad. Sci. USA 108, 13253–13257 (2011).
Yue, W. et al. Inhibition of the autophagic flux by salinomycin in breast cancer stem-like/progenitor cells interferes with their maintenance. Autophagy 9, 714–729 (2013).
Naujokat, C. & Steinhart, R. Salinomycin as a drug for targeting human cancer stem cells. J. Biomed. Biotechnol. 2012, 950658 (2012).
Huczyński, A. et al. Antiproliferative activity of salinomycin and its derivatives. Bioorg. Med. Chem. Lett. 22, 7146–7150 (2012).
Borgström, B. et al. Synthetic modification of salinomycin: selective O-acylation and biological evaluation. Chem. Commun. 49, 9944–9946 (2013).
Huang, X. et al. Semisynthesis of SY-1 for investigation of breast cancer stem cell selectivity of C-ring-modified salinomycin analogues. ACS Chem. Biol. 9, 1587–1594 (2014).
Borgström, B., Huang, X., Chygorin, E., Oredsson, S. & Strand, D. Salinomycin hydroxamic acids: synthesis, structure, and biological activity of polyether ionophore hybrids. ACS Chem. Med. Lett. 7, 635–640 (2016).
Shi, Q. et al. Discovery of a 19F MRI sensitive salinomycin derivative with high cytotoxicity towards cancer cells. Chem. Commun. 52, 5136–5139 (2016).
Borgström, B., Huang, X., Hegardt, C., Oredsson, S . & Strand, D. Structure-activity relationships in salinomycin: cytotoxicity and phenotype selectivity of semi-synthetic derivatives. Chem. Eur. J. 23, 2077–2083 (2017).
Nishi, M. et al. Induction of cells with cancer stem cell properties from nontumorigenic human mammary epithelial cells by defined reprogramming factors. Oncogene 33, 643–652 (2014).
Minta, A. & Tsien, R. Y. Fluorescent indicators for cytosolic sodium. J. Biol. Chem. 264, 19449–19457 (1989).
Charafe-Jauffret, E. et al. ALDH1-positive cancer stem cells predict engraftment of primary breast tumors and are governed by a common stem cell program. Cancer Res. 73, 7290–7300 (2013).
Rodriguez, R. et al. Small-molecule-induced DNA damage identifies alternative DNA structures in human genes. Nat. Chem. Biol. 8, 301–310 (2012).
Larrieu, D., Britton, S., Demir, M., Rodriguez, R. & Jackson, S. P. Chemical inhibition of NAT10 corrects defects of laminopathic cells. Science 344, 527–532 (2014).
Abell, N. S., Mercado, M., Cañeque, T., Rodriguez, R. & Xhemalce, B. Click quantitative mass spectrometry identifies PIWIL3 as a mechanistic target of RNA interference activator enoxacin in cancer cells. J. Am. Chem. Soc. 139, 1400–1403 (2017).
Cañeque, T. et al. Synthesis of marmycin A and investigation into its cellular activity. Nat. Chem. 7, 744–751 (2015).
Pantopoulos, K., Porwal, S. K., Tartakoff, A. & Devireddy, L. Mechanisms of mammalian iron homeostasis. Biochemistry 51, 5705–5724 (2012).
Asano, T. et al. Distinct mechanisms of ferritin delivery to lysosomes in iron-depleted and iron-replete cells. Mol. Cell Biol. 10, 2040–2052 (2011).
Hirayama, T., Okuda, K. & Nagasawa, H. A highly selective turn-on fluorescent probe for iron(II) to visualize labile iron in living cells. Chem. Sci. 4, 1250–1256 (2013).
Li, T. et al. Salinomycin induces cell death with autophagy through activation of endoplasmic reticulum stress in human cancer cells. Autophagy 9, 1057–1068 (2013).
Dixon, S. J. & Stockwell, B. R. The role of iron and reactive oxygen species in cell death. Nat. Chem. Biol. 10, 9–17 (2014).
Boya, P. & Kroemer, G. Lysosomal membrane permeabilization in cell death. Oncogene 27, 6434–6451 (2008).
Aits, S. & Jäättelä, M. Lysosomal cell death at a glance. J. Cell Sci. 126, 1905–1912 (2013).
Galluzzi, L., Bravo-San Pedro, J. M. & Kroemer, G. Organelle-specific initiation of cell death. Nat. Cell. Biol. 16, 728–736 (2014).
Dixon, S. J. et al. Ferroptosis: an iron-dependent form of nonapoptotic cell death. Cell 149, 1060–1072 (2012).
Yang, W. S. et al. Regulation of ferroptotic cancer cell death by GPX4. Cell 156, 317–331 (2014).
Conrad, M., Angeli, J. P. F., Vandenabeele, P. & Stockwell, B. R. Regulated necrosis: disease relevance and therapeutic opportunities. Nat. Rev. Drug. Discov. 15, 348–366 (2016).
Yang, W. S. & Stockwell, B. R. Ferroptosis: death by lipid peroxidation. Trends Cell Biol. 26, 165–176 (2016).
Cao, J. Y. & Dixon, S. J. Mechanisms of ferroptosis. Cell. Mol. Life Sci. 73, 2195–2209 (2016).
Torti, S. V. & Torti, F. M. Iron and cancer: more ore to be mined. Nat. Rev. Cancer 13, 342–355 (2013).
Takebe, N. et al. Targeting Notch, Hedgehog, and Wnt pathways in cancer stem cells: clinical update. Nature Rev. Clin. Oncol. 12, 445–464 (2015).
West, N. R., Murray, J. I. & Watson, P. H. Oncostatin-M promotes phenotypic changes associated with mesenchymal and stem cell-like differentiation in breast cancer. Oncogene 33, 1485–1494 (2014).
Schonberg, D. L. et al. Preferential iron trafficking characterizes glioblastoma stem-like cells. Cancer Cell 28, 441–455 (2015).
Pinnix, Z. K. et al. Ferroportin and iron regulation in breast cancer progression and prognosis. Sci. Transl. Med. 2, 43ra56 (2010).
Yamane, K. et al. PLU-1 is an H3K4 demethylase involved in transcriptional repression and breast cancer cell proliferation. Mol. Cell 25, 801–812 (2007).
Yamamoto, S. et al. JARID1B is a luminal lineage-driving oncogene in breast cancer. Cancer Cell 25, 762–777 (2014).
Greer, E. L. & Shi, Y. Histone methylation: a dynamic mark in health, disease and inheritance. Nat. Rev. Genet. 13, 343–357 (2012).
Shen, L. et al. Genome-wide analysis reveals TET- and TDG-dependent 5-methylcytosine oxidation dynamics. Cell 153, 692–706 (2013).
Tsai, Y.-P. et al. TET1 regulates hypoxia-induced epithelial-mesenchymal transition by acting as a co-activator. Genome Biol. 15, 513 (2014).
Hu, X. et al. Tet and TDG mediate DNA demethylation essential for mesenchymal-to-epithelial transition in somatic cell reprogramming. Cell Stem Cell 14, 512–522 (2014).
We thank the CNRS, INSERM and SATT IDF Innov for generous funding. Research in the R.R. laboratory is supported by the European Research Council (grant number 647973), Fondation pour la Recherche Médicale (grant reference AJE20141031486), Emergence Ville de Paris and Ligue Contre le Cancer. A.Ha. is funded by the Fondation de France. We acknowledge the PICT-IBiSA@Pasteur Imaging Facility of Institut Curie, member of the France-BioImaging national research infrastructure. We thank P. Le Bacon for assistance with high-resolution microscopy, J.-F. Gallard, N. Birlirakis and C. Gaillet for assistance with NMR spectroscopy and J. Poupon for electrothermal atomic absorption spectrometry experiments. We thank A. Puisieux for providing us with HMLER cells and V. Mitz for mammary tissues obtained from reduction mammoplasty.
The authors declare no competing financial interests.
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Mai, T., Hamaï, A., Hienzsch, A. et al. Salinomycin kills cancer stem cells by sequestering iron in lysosomes. Nature Chem 9, 1025–1033 (2017). https://doi.org/10.1038/nchem.2778
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