Small molecule sensitization to TRAIL is mediated via nuclear localization, phosphorylation and inhibition of chaperone activity of Hsp27

Abstract

The small chaperone protein Hsp27 confers resistance to apoptosis, and therefore is an attractive anticancer drug target. We report here a novel mechanism underlying the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) sensitizing activity of the small molecule LY303511, an inactive analog of the phosphoinositide 3-kinase inhibitor inhibitor LY294002, in HeLa cells that are refractory to TRAIL-induced apoptosis. On the basis of the fact that LY303511 is derived from LY294002, itself derived from quercetin, and earlier findings indicating that quercetin and LY294002 affected Hsp27 expression, we investigated whether LY303511 sensitized cancer cells to TRAIL via a conserved inhibitory effect on Hsp27. We provide evidence that upon treatment with LY303511, Hsp27 is progressively sequestered in the nucleus, thus reducing its protective effect in the cytosol during the apoptotic process. LY303511-induced nuclear translocation of Hsp27 is linked to its sustained phosphorylation via activation of p38 kinase and MAPKAP kinase 2 and the inhibition of PP2A. Furthermore, Hsp27 phosphorylation leads to the subsequent dissociation of its large oligomers and a decrease in its chaperone activity, thereby further compromising the death inhibitory activity of Hsp27. Furthermore, genetic manipulation of Hsp27 expression significantly affected the TRAIL sensitizing activity of LY303511, which corroborated the Hsp27 targeting activity of LY303511. Taken together, these data indicate a novel mechanism of small molecule sensitization to TRAIL through targeting of Hsp27 functions, rather than its overall expression, leading to decreased cellular protection, which could have therapeutic implications for overcoming chemotherapy resistance in tumor cells.

Pharmacological Targeting of Cell Cycle, Apoptotic and Cell Adhesion Signaling Pathways Implicated in Chemoresistance of Cancer Cells

“…Addition of proteasome inhibitor PS-341 (VELCADE, bortezomib) sensitized prostate cancer cells to TRAIL-induced apoptosis by increasing DR5 inhibiting protein degradation, and elevating DR5 mRNA [ 126 ]. TRAIL-resistant prostate cancer cells, glioma and HeLa cells have also been sensitized by inhibition of heat shock proteins 90 and 27 with geldanamycin, and small molecules 17-AAG and LY303511 [ 127 , 128 , 129 ]. In addition, targeting p53 [ 130 ], autophagy [ 131 ], protein synthesis [ 132 ] and epigenetic modulation [ 133 ] by different agents have been reported to increase sensitivity of breast, myeloid, lung, brain, skin, cervical and colon cancer cells to TRAIL therapy.…”

HSP27 as a Therapeutic Target of Novel Inhibitors and Dietary Phytochemicals in Cancer

“…Furthermore, genetic manipulation of HSP27 expression affected the TRAIL sensitizing activity of LY303511, which further corroborated the HSP27 targeting activity of LY303511. These data suggest a novel mechanism of small molecule sensitization to TRAIL through targeting of HSP27 functions, which could have therapeutic implications for overcoming chemotherapy resistancein HeLa tumor cells [56].…”

Noscapine inhibits human hepatocellular carcinoma growth through inducing apoptosis in vitro and in vivo

“…Western blot analysis. Western blotting assay was carried out as described with little modifi cation [15]. Cells were lysed in RIPA buff er and centrifuged for 15 minutes at 4 °C.…”