title: Targeting of heat shock protein 32 (Hsp32)/heme oxygenase-1 (HO-1) in leukemic cells in chronic myeloid leukemia: a novel approach to overcome resistance against imatinib.
abstract: Resistance toward imatinib and other BCR/ABL tyrosine kinase inhibitors remains an increasing clinical problem in the treatment of advanced stages of chronic myeloid leukemia (CML). We recently have identified the heat shock protein 32 (Hsp32)/heme oxygenase-1 (HO-1) as a BCR/ABL-dependent survival molecule in CML cells. We here show that silencing Hsp32/HO-1 in CML cells by an siRNA approach results in induction of apoptosis. Moreover, targeting Hsp32/HO-1 by either pegylated zinc protoporphyrine (PEG-ZnPP) or styrene maleic acid-micelle-encapsulated ZnPP (SMA-ZnPP) resulted in growth inhibition of BCR/ABL-transformed cells. The effects of PEG-ZnPP and SMA-ZnPP were demonstrable in Ba/F3 cells carrying various imatinib-resistant mutants of BCR/ABL, including the T315I mutant, which exhibits resistance against all clinically available BCR/ABL tyrosine kinase inhibitors. Growth-inhibitory effects of PEG-ZnPP and SMA-ZnPP also were observed in the CML-derived human cell lines K562 and KU812 as well as in primary leukemic cells obtained from patients with freshly diagnosed CML or imatinib-resistant CML. Finally, Hsp32/HO-1-targeting compounds were found to synergize with either imatinib or nilotinib in producing growth inhibition in imatinib-resistant K562 cells and in Ba/F3 cells harboring the T315I mutant of BCR/ABL. In summary, these data show that HO-1 is a promising novel target in imatinib-resistant CML.
authors.affiliation: Department of Internal Medicine I, Division of Hematology and Hemostaseology, Medical University of Vienna, Vienna, Austria. mathias.mayerhofer@meduniwien.ac.at
authors.forename: Matthias
authors.initials: M
authors.lastname: Mayerhofer
authors.forename: Karoline V
authors.initials: KV
authors.lastname: Gleixner
authors.forename: Julia
authors.initials: J
authors.lastname: Mayerhofer
authors.forename: Gregor
authors.initials: G
authors.lastname: Hoermann
authors.forename: Eva
authors.initials: E
authors.lastname: Jaeger
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Aichberger
authors.forename: Rene G
authors.initials: RG
authors.lastname: Ott
authors.forename: Khaled
authors.initials: K
authors.lastname: Greish
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nakamura
authors.forename: Sophia
authors.initials: S
authors.lastname: Derdak
authors.forename: Puchit
authors.initials: P
authors.lastname: Samorapoompichit
authors.forename: Winfried F
authors.initials: WF
authors.lastname: Pickl
authors.forename: Veronika
authors.initials: V
authors.lastname: Sexl
authors.forename: Harald
authors.initials: H
authors.lastname: Esterbauer
authors.forename: Ilse
authors.initials: I
authors.lastname: Schwarzinger
authors.forename: Christian
authors.initials: C
authors.lastname: Sillaber
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Maeda
authors.forename: Peter
authors.initials: P
authors.lastname: Valent
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001549:Benzamides; D001854:Bone Marrow Cells / Q000187:drug effects / Q000473:pathology; D002455:Cell Division / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D005260:Female; D051547:Heme Oxygenase-1 / Q000187:drug effects*; D006801:Humans; D000068877:Imatinib Mesylate; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy* / Q000201:enzymology; D008297:Male; D008875:Middle Aged; D010879:Piperazines / Q000627:therapeutic use*; D011743:Pyrimidines / Q000627:therapeutic use*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1