Abstract 3793: Characterization of the mechanism of action of a novel small molecule inhibitor of HSP70

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL The stress-induced heat shock protein HSP70 is an ATP dependent molecular chaperone that plays a role in the folding of nascent peptides, assembly of multi-protein complexes, and transport of proteins across membranes and overall. Additionally, HSP70 has significant cytoprotective and anti-apoptotic functions. High levels of HSP70 can be found in many cancers, and are associated with poor therapeutic response and poor patient prognosis. These findings suggest that HSP70 may be a desirable molecular therapeutic target, in addition to being a useful tumor prognostic marker. Previously we demonstrated that the compound 2-phenylethynesulfonamide (PES) interacts with HSP70 and antagonizes HSP70 function by disrupting the interaction between HSP70 and its co-chaperones and client proteins. We showed that PES is toxic to cancer cells but not non-transformed cells. Moreover, PES was able to significantly extend the lifespan of mice in a Myc-driven model of lymphoma (p<0.02; Leu et al., Mol Cell 36:15-27, 2009; Leu et al, Mol Can Res 9:936-47, 2011). Here we utilized binding assays, molecular modeling and in silico docking in order to predict the binding site for PES with HSP70. We were able to verify this binding site by identifying point mutants of HSP70 that fail to bind to PES. We used this information in order to predict potentially superior analogues, and we report that a novel analogue, 2-(3-chlorophenyl) ethynesulfonamide (PES-Cl) shows superior toxicity to tumor cells, and greater efficacy as an anti-cancer agent in Myc-driven lymphoma, compared to the parent compound (p<0.0006). Moreover, we report that treatment with PES-Cl causes cell cycle arrest in G2/M, and that a significant fraction of tumor cells escape this checkpoint and die by apoptosis. These data implicate HSP70 in G2/M progression, and identify PES-Cl as a promising anti-cancer therapeutic. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3793. doi:1538-7445.AM2012-3793