title: Targeting autophagy augments the anticancer activity of the histone deacetylase inhibitor SAHA to overcome Bcr-Abl-mediated drug resistance.
abstract: Novel therapeutic strategies are needed to address the emerging problem of imatinib resistance. The histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) is being evaluated for imatinib-resistant chronic myelogenous leukemia (CML) and has multiple cellular effects, including the induction of autophagy and apoptosis. Considering that autophagy may promote cancer cell survival, we hypothesized that disrupting autophagy would augment the anticancer activity of SAHA. Here we report that drugs that disrupt the autophagy pathway dramatically augment the antineoplastic effects of SAHA in CML cell lines and primary CML cells expressing wild-type and imatinib-resistant mutant forms of Bcr-Abl, including T315I. This regimen has selectivity for malignant cells and its efficacy was not diminished by impairing p53 function, another contributing factor in imatinib resistance. Disrupting autophagy by chloroquine treatment enhances SAHA-induced superoxide generation, triggers relocalization and marked increases in the lysosomal protease cathepsin D, and reduces the expression of the cathepsin-D substrate thioredoxin. Finally, knockdown of cathepsin D diminishes the potency of this combination, demonstrating its role as a mediator of this therapeutic response. Our data suggest that, when combined with HDAC inhibitors, agents that disrupt autophagy are a promising new strategy to treat imatinib-refractory patients who fail conventional therapy.
authors.affiliation: Departments of Biochemistry, St. Jude Children's Research Hospital, Memphis, TN, USA.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Carew
authors.forename: Steffan T
authors.initials: ST
authors.lastname: Nawrocki
authors.forename: Charissa N
authors.initials: CN
authors.lastname: Kahue
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.forename: Chunying
authors.initials: C
authors.lastname: Yang
authors.forename: Linda
authors.initials: L
authors.lastname: Chung
authors.forename: Janet A
authors.initials: JA
authors.lastname: Houghton
authors.forename: Peng
authors.initials: P
authors.lastname: Huang
authors.forename: Francis J
authors.initials: FJ
authors.lastname: Giles
authors.forename: John L
authors.initials: JL
authors.lastname: Cleveland
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D001343:Autophagy / Q000187:drug effects*; D002402:Cathepsin D / Q000502:physiology; D045744:Cell Line, Tumor; D002738:Chloroquine / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D016044:Fusion Proteins, bcr-abl / Q000494:pharmacology; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy* / Q000473:pathology; D000077337:Vorinostat
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D000077337:Vorinostat; D002738:Chloroquine; D016044:Fusion Proteins, bcr-abl; D002402:Cathepsin D