Ivermectin inhibits HSP27 and potentiates efficacy of oncogene targeting in tumor models
Lucia Nappi, … , Gary D. Brayer, Martin Gleave
Lucia Nappi, … , Gary D. Brayer, Martin Gleave
Published December 17, 2019
Citation Information: J Clin Invest. 2020;130(2):699-714. https://doi.org/10.1172/JCI130819.
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Ivermectin inhibits HSP27 and potentiates efficacy of oncogene targeting in tumor models

Abstract

HSP27 is highly expressed in, and supports oncogene addiction of, many cancers. HSP27 phosphorylation is a limiting step for activation of this protein and a target for inhibition, but its highly disordered structure challenges rational structure-guided drug discovery. We performed multistep biochemical, structural, and computational experiments to define a spherical 24-monomer complex composed of 12 HSP27 dimers with a phosphorylation pocket flanked by serine residues between their N-terminal domains. Ivermectin directly binds this pocket to inhibit MAPKAP2-mediated HSP27 phosphorylation and depolymerization, thereby blocking HSP27-regulated survival signaling and client-oncoprotein interactions. Ivermectin potentiated activity of anti–androgen receptor and anti-EGFR drugs in prostate and EGFR/HER2-driven tumor models, respectively, identifying a repurposing approach for cotargeting stress-adaptive responses to overcome resistance to inhibitors of oncogenic pathway signaling.

Authors

Lucia Nappi, Adeleke H. Aguda, Nader Al Nakouzi, Barbara Lelj-Garolla, Eliana Beraldi, Nada Lallous, Marisa Thi, Susan Moore, Ladan Fazli, Dulguun Battsogt, Sophie Stief, Fuqiang Ban, Nham T. Nguyen, Neetu Saxena, Evgenia Dueva, Fan Zhang, Takeshi Yamazaki, Amina Zoubeidi, Artem Cherkasov, Gary D. Brayer, Martin Gleave

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Figure 1

Ivermectin binds to HSP27 phosphorylation pocket.

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Ivermectin binds to HSP27 phosphorylation pocket. (A) FRET assay using H...
(A) FRET assay using HSP27 labeled with QSY21 as negative control (blue triangles), and HSP27-RR alone (green triangles) or combined with IVM (brown circles) as positive controls. Red squares represent IVM effect on subunit exchange. (B) FITC-insulin precipitation in the presence of DMSO or increasing concentrations of IVM. (C) BLI dose-response curves reflect direct binding of IVM to purified HSP27 protein. (D) Protein aggregation in HSF1–/– MEF cells incubated with HSP27 (left) or HSP70 and HSP90 (middle and right) in the presence of IVM (gray) or DMSO (red). Protein lysate without chaperones was used as negative control (black). Results were normalized to HSP values alone. For HSP90 the effect of IVM was compared with that of 17AAG (blue). (E) Ribbon drawing of the HSP27 24-mer down its 3-fold symmetry axis. Arrows represent bisecting 2-fold axes. Monomers A are shown in green and monomers B in brown. (F) Magnified view of the interface between monomers in a dimer unit showing the phosphorylation pocket. Spheres indicate S78 and S82, and the mesh represents the WDPF motif of each monomer. Peptides 6 and 11 conferring chaperone activity are shown in blue and red, respectively. (G) Ribbon representation of the NTD of monomer A (green) fitting into a pocket created by its related monomer B and a neighboring monomer B NTD. (H) Left: Predicted binding pocket between the 2 NTDs of an HSP27 dimer: monomer A (gold), monomer B (cyan), and IVM (violet). Right: S78 and S82 and other amino acids involved in IVM interaction. Hydrogen bonds are shown in green. (I) BLI reported binding of IVM to the HSP27 phosphorylation pocket mutants S78A-S82A (left) and S78D-S82D (right).