American Association for Cancer Research
15417786mcr120547t-sup-fig2.pdf (280.36 kB)

Supplementary Figure 2 from A Modified HSP70 Inhibitor Shows Broad Activity as an Anticancer Agent

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journal contribution
posted on 2023-04-03, 16:06 authored by Gregor M. Balaburski, Julia I.-Ju Leu, Neil Beeharry, Seth Hayik, Mark D. Andrake, Gao Zhang, Meenhard Herlyn, Jessie Villanueva, Roland L. Dunbrack, Tim Yen, Donna L. George, Maureen E. Murphy

PDF file - 280K, A) Chemical structures of PES and synthesized derivatives. P=pyrrolidine; CM= carboxymethyl; Cl=chloride. B) MTT cell viability analyses of H1299 and PANC1 cells after 48 hour treatment with 10 uM PES, PES-P, PES-PCM and PES-PCl. The values shown are the averaged results from three independent experiments, and error bars mark standard deviations. C) Immunoblot analysis of H1299 cells following treatment with 10 uM of the compounds indicated for the timepoints indicated, using antisera to the autophagy (p62SQSTM1 and LC3) and apoptosis (cleaved lamin A) markers indicated, as well as HSP70 and actin (control). The arrows mark monomeric and oligomeric forms of p62SQSTM1, as well as cleaved and lipidated forms of LC3 I and II.



The stress-induced HSP70 is an ATP-dependent molecular chaperone that plays a key role in refolding misfolded proteins and promoting cell survival following stress. HSP70 is marginally expressed in nontransformed cells, but is greatly overexpressed in tumor cells. Silencing HSP70 is uniformly cytotoxic to tumor but not normal cells; therefore, there has been great interest in the development of HSP70 inhibitors for cancer therapy. Here, we report that the HSP70 inhibitor 2-phenylethynesulfonamide (PES) binds to the substrate-binding domain of HSP70 and requires the C-terminal helical “lid” of this protein (amino acids 573–616) to bind. Using molecular modeling and in silico docking, we have identified a candidate binding site for PES in this region of HSP70, and we identify point mutants that fail to interact with PES. A preliminary structure–activity relationship analysis has revealed a derivative of PES, 2-(3-chlorophenyl) ethynesulfonamide (PES-Cl), which shows increased cytotoxicity and ability to inhibit autophagy, along with significantly improved ability to extend the life of mice with pre-B-cell lymphoma, compared with the parent compound (P = 0.015). Interestingly, we also show that these HSP70 inhibitors impair the activity of the anaphase promoting complex/cyclosome (APC/C) in cell-free extracts, and induce G2–M arrest and genomic instability in cancer cells. PES-Cl is thus a promising new anticancer compound with several notable mechanisms of action. Mol Cancer Res; 11(3); 219–29. ©2013 AACR.

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