Epichaperome Inhibition by PU-H71-Mediated Targeting of HSP90 Sensitizes Glioblastoma Cells to Alkylator-Induced DNA Damage
Abstract
Background: Targeted therapies have generally failed to effectively treat glioblastoma (GBM) due to the tumor’s heterogeneity and both intrinsic and adaptive resistance to treatment. Simultaneously targeting multiple pro-survival pathways may help overcome these challenges and improve therapeutic outcomes. Heat shock protein 90 (HSP90), a key component of the epichaperome complex, is essential for the proper folding and activation of various pro-survival oncogenic proteins that contribute to GBM progression.
Methods: We employed a range of biochemical and biological assays to evaluate HSP90 expression and its downstream targets, as well as the impact of PU-H71, a highly specific and potent HSP90 inhibitor, on target modulation, downstream biochemical changes, cell cycle progression, proliferation, migration, and apoptosis. Experiments were conducted using patient-derived glioma stem-like cells (GSCs) exhibiting molecular features characteristic of GBM, commercial glioma cell lines, and normal human astrocytes (NHAs).
Results: Inhibition of HSP90 by PU-H71 in GSCs significantly decreased cell proliferation, colony formation, wound healing, migration, and angiogenesis. In glioma cells—but not in NHAs—PU-H71-mediated HSP90 inhibition led to downregulation of pro-survival client proteins including EGFR, MAPK, AKT, and S6. This suppression of pro-survival signaling enhanced glioma cells’ sensitivity to temozolomide, a monofunctional alkylating agent. Combination treatment with PU-H71 and temozolomide demonstrated greater anticancer efficacy than either drug alone.
Conclusions: These findings confirm that HSP90 acts as a critical pro-survival factor in molecularly diverse gliomas and support further investigation of epichaperome inhibition with HSP90 inhibitors as a therapeutic strategy for gliomas Zelavespib.
Keywords: HSP70; HSP90 effector proteins; PU-H71; heat shock protein 90; malignant glioma