title: In vivo tumor growth is inhibited by cytosolic iron deprivation caused by the expression of mitochondrial ferritin.
abstract: Mitochondrial ferritin (MtFt) is a mitochondrial iron-storage protein whose function and regulation is largely unknown. Our previous results have shown that MtFt overexpression markedly affects intracellular iron homeostasis in mammalian cells. Using tumor xenografts, we examined the effects of MtFt overexpression on tumor iron metabolism and growth. The expression of MtFt dramatically reduced implanted tumor growth in nude mice. Mitochondrial iron deposition in MtFt-expressing tumors was directly observed by transmission electron microscopy. A cytosolic iron starvation phenotype in MtFt-expressing tumors was revealed by increased RNA-binding activity of iron regulatory proteins, and concomitantly both an increase in transferrin receptor levels and a decrease in cytosolic ferritin. MtFt overexpression also led to decreases in total cellular heme content and heme oxygenase-1 levels. In addition, elevated MtFt in tumors was also associated with a decrease in total aconitase activity and lower frataxin protein level. In conclusion, our study shows that high MtFt levels can significantly affect tumor iron homeostasis by shunting iron into mitochondria; iron scarcity resulted in partially deficient heme and iron-sulfur cluster synthesis. It is likely that deprivation of iron in the cytosol is the cause for the significant inhibition of xenograft tumor growth.
authors.affiliation: Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital and Department of Physiology, McGill University, 3755 Cote Ste-Catherine Rd, Montreal, QC H3T 1E2, Canada.
authors.forename: Guangjun
authors.initials: G
authors.lastname: Nie
authors.forename: Guohua
authors.initials: G
authors.lastname: Chen
authors.forename: Alex D
authors.initials: AD
authors.lastname: Sheftel
authors.forename: Kostas
authors.initials: K
authors.lastname: Pantopoulos
authors.forename: Prem
authors.initials: P
authors.lastname: Ponka
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003600:Cytosol / Q000378:metabolism*; D005293:Ferritins / Q000378:metabolism*; D006418:Heme / Q000737:chemistry; D051547:Heme Oxygenase-1 / Q000378:metabolism; D006801:Humans; D007501:Iron / Q000378:metabolism*; D035925:Iron-Regulatory Proteins / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D008928:Mitochondria / Q000378:metabolism*; D009368:Neoplasm Transplantation
chemical_list: D035925:Iron-Regulatory Proteins; D006418:Heme; D005293:Ferritins; D007501:Iron; D051547:Heme Oxygenase-1