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-B-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-AAGmediated 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. (Cancer Res 2005; 65(22): 10536-44)

Antitumor activity and molecular effects of the novel heat shock protein 90 inhibitor, IPI-504, in pancreatic cancer

“…This is closely correlated with MS data on at least three isoforms of Hsp70 proteins (HSPA5, HSPA1B, and HSPA8). This finding is consistent with the results of the in vitro study as well as with earlier studies showing molecular cross-talk between other heat shock family proteins as result of Hsp90 modulation by 17-allylamino,17-demethoxy-geldanamycin (37,38). and establishment of localization (29%) and localized in cytoplasm (70%) and organelle membrane (12%; A and B).…”

A novel, small molecule inhibitor of Hsc70/Hsp70 potentiates Hsp90 inhibitor induced apoptosis in HCT116 colon carcinoma cells

“…Through its ability to control the activity and stability of many client proteins involved in the oncogenic process, targeting Hsp90 has the potential to affect all the hallmarks of cancer. It is well documented that the Hsp70 family of chaperones have an anti-apoptotic function and targeting the induction of Hsp70 following Hsp90 inhibition sensitized tumor cells to Hsp90 inhibition [29][30][31].…”

Up-regulation of Heat Shock Protein 27 Induces Resistance to 17-Allylamino-Demethoxygeldanamycin through a Glutathione-Mediated Mechanism

“…Bagatell et al (11) showed that HSF-1 À/À cells were significantly more sensitive to Hsp90-targeted agents, indicating the potential role of the HSF-1-mediated stress response in 17-AAG resistance. Guo et al (17) showed the importance of Hsp70 in mediating sensitivity to 17-AAG by inhibiting apoptotic signaling in leukemia. This is in agreement with a previous study by Nishimura et al (41) that suggested that Hsp70 is a major factor in determining cell death after heat stress.…”

“…Because these proteins are dramatically up-regulated in response to treatment with Hsp90 inhibitors such as GA or 17-AAG (10)(11)(12), their potential involvement in resistance to Hsp90 inhibitors in the clinic has recently gained interest (16). Other studies have shown the protection of cancer cells from 17-AAG-induced death by Hsp70, which is known to be up-regulated in response to Hsp90-directed agents (17). However, other proteins that are up-regulated in an HSF-1-mediated stress response may also contribute to differences in 17-AAG sensitivity.…”