A new HSP90 inhibitor as therapeutic agent for bladder cancer.

Abstract

416 Background: Hsp90 represents one of the most promising biological targets for the treatment of cancer, including bladder cancer. A number of Hsp90 inhibitors that target the N-terminal ATP-binding pocket have demonstrated potent antiproliferative effects. However, a major drawback is that they induce a prosurvival heat shock response (HSR). We demonstrate the effects of a novel Hsp90 beta selective inhibitor on bladder cancer cells, which shows potent antiproliferative effects without inducing HSR. Methods: Cell Titer-Glo luminescent anti-proliferative assay was used to determine the IC50 numbers in UC3 cells. Trypan Blue Cytotoxicity assay was performed for 24h treatment with increasing concentrations of the inhibitor. Effects of the cmpound on Hsp90’s client protein degradation were investigated by Western Blot. Results: This new compound exhibits potent anti-proliferative in bladder cancer cells. IC50 number is determined as 0.30 µM for UC3 cancer cells. The toxicity assay was also performed over UC3 cells at 24h.1uM KU new compound has the similar effects on UC3 cells as 10 uM 17AAG: inhibit the cancer cells growth to half, but maintain over 60% viability of the cells. The western blot were also performed over UC3 cells, and some new target proteins such as FGFR3 and PKM2 were investigated. The data showed that, this new compound would not induce the heat shock response like 17AAG (Hsp27), and did cause some Hsp90β related protein degradation (CXCR4). FGFR3, PKM2, Her2, Hsf-1and B-raf all show degradation to different extent. Conclusions: A novel Hsp90 inhibitor, exhibits potent anti-proliferative and cytotoxic activity along with client protein degradation, without induction of HSR in bladder cancer cell lines. The reduction of Hsp90 beta related client protein caused by this compound suggests the potential to develop isoform specific inhibitors of Hsp90 for better antitumor therapies.