title: Mechanistic role of heat shock protein 70 in Bcr-Abl-mediated resistance to apoptosis in human acute leukemia cells.
abstract: Bcr-Abl-expressing primary or cultured leukemia cells display high levels of the antiapoptotic heat shock protein (hsp) 70 and are resistant to cytarabine (Ara-C), etoposide, or Apo-2L/TRAIL (TNF-related apoptosis-inducing ligand)-induced apoptosis. Conversely, a stable expression of the cDNA of hsp70 in the reverse orientation attenuated not only hsp70 but also signal transducers and activators of transcription 5 (STAT5) and Bcl-x(L) levels. This increased apoptosis induced by cytarabine, etoposide, or Apo-2L/TRAIL. Ectopic expression of hsp70 in HL-60 cells (HL-60/hsp70) inhibited Ara-C and etoposide-induced Bax conformation change and translocation to the mitochondria; attenuated the accumulation of cytochrome c, Smac, and Omi/HtrA2 in the cytosol; and inhibited the processing and activity of caspase-9 and caspase-3. Hsp70 was bound to death receptors 4 and 5 (DR4 and DR5) and inhibited Apo-2L/TRAIL-induced assembly and activity of the death-inducing signaling complex (DISC). HL-60/hsp70 cells exhibited increased levels and DNA binding activity of STAT5, which was associated with high levels of Pim-2 and Bcl-x(L) and resistance to apoptosis. Expression of the dominant negative (DN) STAT5 resensitized HL-60/hsp70 cells to cytarabine, etoposide, and Apo-2L/TRAIL-induced apoptosis. Collectively, these findings suggest that hsp70 inhibits apoptosis upstream and downstream of the mitochondria and is a promising therapeutic target for reversing drug-resistance in chronic myeloid leukemia-blast crisis and acute myeloid leukemia cells.
authors.affiliation: Department of Interdisciplinary Oncology, H. Lee Moffitt Cancer Center, Tampa, FL 33612, USA.
authors.forename: Fei
authors.initials: F
authors.lastname: Guo
authors.forename: Celia
authors.initials: C
authors.lastname: Sigua
authors.forename: Purva
authors.initials: P
authors.lastname: Bali
authors.forename: Prince
authors.initials: P
authors.lastname: George
authors.forename: Warren
authors.initials: W
authors.lastname: Fiskus
authors.forename: Anna
authors.initials: A
authors.lastname: Scuto
authors.forename: Srinivas
authors.initials: S
authors.lastname: Annavarapu
authors.forename: Abdelmoughite
authors.initials: A
authors.lastname: Mouttaki
authors.forename: Gautam
authors.initials: G
authors.lastname: Sondarva
authors.forename: Sheng
authors.initials: S
authors.lastname: Wei
authors.forename: Jie
authors.initials: J
authors.lastname: Wu
authors.forename: Julie
authors.initials: J
authors.lastname: Djeu
authors.forename: Kapil
authors.initials: K
authors.lastname: Bhalla
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D045744:Cell Line, Tumor; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D016044:Fusion Proteins, bcr-abl / Q000502:physiology*; D018922:HL-60 Cells; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000502:physiology*; D006801:Humans; D019169:Jurkat Cells; D015470:Leukemia, Myeloid, Acute; D008894:Milk Proteins / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050799:STAT5 Transcription Factor; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
chemical_list: C494826:BAX protein, human; C494811:BCL2L1 protein, human; D017931:DNA Primers; D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; D008894:Milk Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D016044:Fusion Proteins, bcr-abl