KU135, a Novel Novobiocin-Derived C-Terminal Inhibitor of the 90-kDa Heat Shock Protein, Exerts Potent Antiproliferative Effects in Human Leukemic Cells

Abstract

The 90-kDa heat shock protein (Hsp90) assists in the proper folding of numerous mutated or overexpressed signal transduction proteins that are involved in cancer. Consequently, there is considerable interest in developing chemotherapeutic drugs that specifically disrupt the function of Hsp90. Here, we investigated the extent to which a novel novobiocin-derived C-terminal Hsp90 inhibitor, designated KU135, induced antiproliferative effects in Jurkat T-lymphocytes. The results indicated that KU135 bound directly to Hsp90, caused the degradation of known Hsp90 client proteins, and induced more potent antiproliferative effects than the established N-terminal Hsp90 inhibitor 17-allylamino-demethoxygeldanamycin (17-AAG). Closer examination of the cellular response to KU135 and 17-AAG revealed that only 17-AAG induced a strong up-regulation of Hsp70 and Hsp90. In addition, KU135 caused wild-type cells to undergo G 2 /M arrest, whereas cells treated with 17-AAG accumulated in G 1 . Furthermore, KU135 but not 17-AAG was found to be a potent inducer of mitochondria-mediated apoptosis as evidenced, in part, by the fact that cell death was inhibited to a similar extent by Bcl-2/Bcl-x L overexpression or the depletion of apoptotic protease-activating factor-1 (Apaf-1). Together, these data suggest that KU135 inhibits cell proliferation by regulating signaling pathways that are mechanistically different from those targeted by 17-AAG and as such represents a novel opportunity for Hsp90 inhibition.

Neuroprotective effect of paeoniflorin on H2O2-induced apoptosis in PC12 cells by modulation of reactive oxygen species and the inflammatory response

“…PARP may be cleaved by numerous caspase-1-like caspases in vitro and is one of the primary cleavage targets of caspase-3 in vivo. Furthermore, ROS may activate caspase-3, which results in the cleavage of PARP into an 89-kDa fragment (6,(15)(16)(17)20). In the present study, a Hoechst 33258 staining assay indicated that treatment with 200 µM H 2 O 2 alone induced notable cell apoptosis in PC12 cells, while 80 µM PF produced a reduction in the extent of apoptosis-associated nuclear fragmentation (Fig.…”

Endoplasmic Reticulum-resident Heat Shock Protein 90 (HSP90) Isoform Glucose-regulated Protein 94 (GRP94) Regulates Cell Polarity and Cancer Cell Migration by Affecting Intracellular Transport

“…The novobiocin analogue, KU-135, was synthesized as described previously, and purity was verified as Ͼ95% by NMR and mass spectrometry (14). Recombinant human soluble TRAIL was a kind gift from Dr. Thomas Sayers (National Institutes of Health).…”

KU675, a Concomitant Heat-Shock Protein Inhibitor of Hsp90 and Hsc70 that Manifests Isoform Selectivity for Hsp90α in Prostate Cancer Cells

“…Compared with N-terminal inhibitors, the antibiotic novobiocin (NB) binds the C terminus of Hsp90 and, through Hsp90 C-terminal inhibitions, induces client protein degradation without induction of the prosurvival HSR (Burlison et al, 2008;Shelton et al, 2009;Matthews et al, 2010;Eskew et al, 2011). We have previously reported the synthesis and evaluation of NB analogs that exhibit improved potency over NB (Shelton et al, 2009;Matthews et al, 2010;Eskew et al, 2011;Kusuma et al, 2014). In this article, we report a new C-terminal inhibitor, KU675, that exhibits potent antiproliferative effects in prostate cancer cells and a preference for the inhibition of Hsp90a.…”