Discovery And Preclinical Antitumor Efficacy Evaluation Of Fs81, A Fragment-based Designed Heat Shock Protein90Inhibitor

Heat shock protein90(HSP90), a highly conserved molecular chaperone,is involved in many important cellular processes including proliferation, migrationand angiogenesis though stabilizing its client proteins. Recently, more and moreexperimental evidence has demonstrated that overexpression of HSP90is correlatedwith tumor progression. Mechanismly, HSP90can binds to and functions as a keyregulator of many oncoproteins such as kinases and transcription factors to sustaintheir signals. Inhibition of HSP90kinase can trigger many aberrant activatedoncoproteins simultaneously for degradation and further down-regulate their signalingpathways to result in tumor shrinkage. Thus, HSP90has been recognized as apromising therapeutic target in a large variety of human cancer and multiple kinaseinhibitors has been tested in phase1-III clinical trials.In this study, we screened a panel of fragment-based designed HSP90inhibitorsthough fluorescence polarization technology and picked FS81for further systemicevaluation. We observed that FS81displayed potent antiproliferation activities in abroad spectrum of tumor cells where its IC50ranged from11to931nM, which issimilar to a known HSP90inhibitor NVP-AUY922. Further, we found that FS81caninduce the degradation of several key client proteins such as c-Met, EGFR, HER2,ALK and suppress their downstream signals in a dose dependent way. FS81caninduce G2/M phase arrest though inhibiting cdc2and trigger apoptosis in caspasedependent signaling pathway. Wound healing and transwell assay showed that FS81can inhibite the migration of tumor cells dose-dependently and also inhibiteangiogenssis by disrupting tube formation of HUVEC. The hERG assay indicated thatFS81has a lower toxicity. However, in vivo xenograft mouse model established inU87-MG showed that FS81can only inhibit the tumor growth marginally whichmight be resulted from its shorter half-life. Although FS81is not a promisingcandidate for targeting HSP90in vivo, our study hereby supplied a useful scaffold for further structural modification to discover more potent and effective HSP90kinaseinhibitors.