title: Idarubicin induces mTOR-dependent cytotoxic autophagy in leukemic cells.
abstract: We investigated if the antileukemic drug idarubicin induces autophagy, a process of programmed cellular self-digestion, in leukemic cell lines and primary leukemic cells. Transmission electron microscopy and acridine orange staining demonstrated the presence of autophagic vesicles and intracellular acidification, respectively, in idarubicin-treated REH leukemic cell line. Idarubicin increased punctuation/aggregation of microtubule-associated light chain 3B (LC3B), enhanced the conversion of LC3B-I to autophagosome-associated LC3B-II in the presence of proteolysis inhibitors, and promoted the degradation of the selective autophagic target p62, thus indicating the increase in autophagic flux. Idarubicin inhibited the phosphorylation of the main autophagy repressor mammalian target of rapamycin (mTOR) and its downstream target p70S6 kinase. The treatment with the mTOR activator leucine prevented idarubicin-mediated autophagy induction. Idarubicin-induced mTOR repression was associated with the activation of the mTOR inhibitor AMP-activated protein kinase and down-regulation of the mTOR activator Akt. The suppression of autophagy by pharmacological inhibitors or LC3B and beclin-1 genetic knockdown rescued REH cells from idarubicin-mediated oxidative stress, mitochondrial depolarization, caspase activation and apoptotic DNA fragmentation. Idarubicin also caused mTOR inhibition and cytotoxic autophagy in K562 leukemic cell line and leukocytes from chronic myeloid leukemia patients, but not healthy controls. By demonstrating mTOR-dependent cytotoxic autophagy in idarubicin-treated leukemic cells, our results warrant caution when considering combining idarubicin with autophagy inhibitors in leukemia therapy.
authors.affiliation: Institute of Microbiology and Immunology, School of Medicine, University of Belgrade, Dr. Subotica 1, 11000 Belgrade, Serbia.
authors.forename: Biljana
authors.initials: B
authors.lastname: Ristic
authors.affiliation: Institute of Histology and Embryology, School of Medicine, University of Belgrade, Belgrade, Serbia.
authors.forename: Mihajlo
authors.initials: M
authors.lastname: Bosnjak
authors.affiliation: Institute of Microbiology and Immunology, School of Medicine, University of Belgrade, Dr. Subotica 1, 11000 Belgrade, Serbia.
authors.forename: Katarina
authors.initials: K
authors.lastname: Arsikin
authors.affiliation: Institute of Histology and Embryology, School of Medicine, University of Belgrade, Belgrade, Serbia.
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Mircic
authors.affiliation: Institute of Histology and Embryology, School of Medicine, University of Belgrade, Belgrade, Serbia.
authors.forename: Violeta
authors.initials: V
authors.lastname: Suzin-Zivkovic
authors.affiliation: Clinic for Hematology, Clinical Centre of Serbia, School of Medicine, University of Belgrade, Belgrade, Serbia.
authors.forename: Andrija
authors.initials: A
authors.lastname: Bogdanovic
authors.affiliation: Institute of Microbiology and Immunology, School of Medicine, University of Belgrade, Dr. Subotica 1, 11000 Belgrade, Serbia.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Perovic
authors.affiliation: Institute of Histology and Embryology, School of Medicine, University of Belgrade, Belgrade, Serbia.
authors.forename: Tamara
authors.initials: T
authors.lastname: Martinovic
authors.affiliation: Institute of Histology and Embryology, School of Medicine, University of Belgrade, Belgrade, Serbia.
authors.forename: Tamara
authors.initials: T
authors.lastname: Kravic-Stevovic
authors.affiliation: Institute of Histology and Embryology, School of Medicine, University of Belgrade, Belgrade, Serbia.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Bumbasirevic
authors.affiliation: Institute of Microbiology and Immunology, School of Medicine, University of Belgrade, Dr. Subotica 1, 11000 Belgrade, Serbia. Electronic address: vtrajkovic@med.bg.ac.rs.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Trajkovic
authors.affiliation: Institute for Biological Research, University of Belgrade, Belgrade, Despot Stefan Blvd. 142, 11000 Belgrade, Serbia. Electronic address: buajk@yahoo.com.
authors.forename: Ljubica
authors.initials: L
authors.lastname: Harhaji-Trajkovic
mesh_terms: D000328:Adult; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects*; D000071186:Beclin-1; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D015255:Idarubicin / Q000494:pharmacology*; D007124:Immunoenzyme Techniques; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008565:Membrane Proteins / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D010766:Phosphorylation / Q000187:drug effects; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000903:Antibiotics, Antineoplastic; D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D008565:Membrane Proteins; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D015255:Idarubicin
keywords: Apoptosis; Autophagy; Idarubicin; Leukemia; mTOR