Mechanistic role of heat shock protein 70 in Bcr-Abl-mediated resistance to apoptosis in human acute leukemia cells

Fei Guo, Celia Sigua, Purva Bali, Prince George, Warren Fiskus, Anna Scuto, Srinivas Annavarapu, Abdelmoughite Mouttaki, Gautam Sondarva, Sheng Wei, Jie Wu, Julie Djeu, Kapil Bhalla

Research output: Contribution to journalArticle

138 Scopus citations

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-xL 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-xL 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.

Original languageEnglish (US)
Pages (from-to)1246-1255
Number of pages10
JournalBlood
Volume105
Issue number3
DOIs
StatePublished - Feb 1 2005

ASJC Scopus subject areas

  • Biochemistry
  • Immunology
  • Hematology
  • Cell Biology

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