title: Abrogation of heat shock protein 70 induction as a strategy to increase antileukemia activity of heat shock protein 90 inhibitor 17-allylamino-demethoxy geldanamycin.
abstract: 17-Allylamino-demethoxy geldanamycin (17-AAG) inhibits the chaperone association of heat shock protein 90 (hsp90) with the heat shock factor-1 (HSF-1), which induces the mRNA and protein levels of hsp70. Increased hsp70 levels inhibit death receptor and mitochondria-initiated signaling for apoptosis. Here, we show that ectopic overexpression of hsp70 in human acute myelogenous leukemia HL-60 cells (HL-60/hsp70) and high endogenous hsp70 levels in Bcr-Abl-expressing cultured CML-BC K562 cells confers resistance to 17-AAG-induced apoptosis. In HL-60/hsp70 cells, hsp70 was bound to Bax, inhibited 17-AAG-mediated Bax conformation change and mitochondrial localization, thereby inhibiting the mitochondria-initiated events of apoptosis. Treatment with 17-AAG attenuated the levels of phospho-AKT, AKT, and c-Raf but increased hsp70 levels to a similar extent in the control HL-60/Neo and HL-60/hsp70 cells. Pretreatment with 17-AAG, which induced hsp70, inhibited 1-beta-D-arabinofuranosylcytosine or etoposide-induced apoptosis in HL-60 cells. Stable transfection of a small interfering RNA (siRNA) to hsp70 completely abrogated the endogenous levels of hsp70 and blocked 17-AAG-mediated hsp70 induction, resulting in sensitizing K562/siRNA-hsp70 cells to 17-AAG-induced apoptosis. This was associated with decreased binding of Bax to hsp70 and increased 17-AAG-induced Bax conformation change. 17-AAG-mediated decline in the levels of AKT, c-Raf, and Bcr-Abl was similar in K562 and K562/siRNA-hsp70 cells. Cotreatment with KNK437, a benzylidine lactam inhibitor of hsp70 induction and thermotolerance, attenuated 17-AAG-mediated hsp70 induction and increased 17-AAG-induced apoptosis and loss of clonogenic survival of HL-60 cells. Collectively, these data indicate that induction of hsp70 attenuates the apoptotic effects of 17-AAG, and abrogation of hsp70 induction significantly enhances the antileukemia activity of 17-AAG.
authors.affiliation: Department of Interdisciplinary Oncology, H. Lee Moffitt Cancer Center, Tampa, Florida 33612, USA.
authors.forename: Fei
authors.initials: F
authors.lastname: Guo
authors.forename: Kathy
authors.initials: K
authors.lastname: Rocha
authors.forename: Purva
authors.initials: P
authors.lastname: Bali
authors.forename: Michael
authors.initials: M
authors.lastname: Pranpat
authors.forename: Warren
authors.initials: W
authors.lastname: Fiskus
authors.forename: Sandhya
authors.initials: S
authors.lastname: Boyapalle
authors.forename: Sandhya
authors.initials: S
authors.lastname: Kumaraswamy
authors.forename: Maria
authors.initials: M
authors.lastname: Balasis
authors.forename: Benjamin
authors.initials: B
authors.lastname: Greedy
authors.forename: E Simon M
authors.initials: ES
authors.lastname: Armitage
authors.forename: Nicholas
authors.initials: N
authors.lastname: Lawrence
authors.forename: Kapil
authors.initials: K
authors.lastname: Bhalla
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001559:Benzhydryl Compounds / Q000494:pharmacology; D016227:Benzoquinones; D003131:Combined Modality Therapy; D003561:Cytarabine / Q000494:pharmacology; D004357:Drug Synergism; D005047:Etoposide / Q000494:pharmacology; D018922:HL-60 Cells; D018840:HSP70 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis* / Q000235:genetics; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D006801:Humans; D020014:K562 Cells; D047029:Lactams, Macrocyclic; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D011487:Protein Conformation / Q000187:drug effects; D011760:Pyrrolidinones / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D017828:Rifabutin / Q000031:analogs & derivatives* / Q000494:pharmacology; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D001559:Benzhydryl Compounds; D016227:Benzoquinones; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; C410027:KNK 437; D047029:Lactams, Macrocyclic; D011760:Pyrrolidinones; D034741:RNA, Small Interfering; D051028:bcl-2-Associated X Protein; D003561:Cytarabine; D017828:Rifabutin; C112765:tanespimycin; D005047:Etoposide