HSP27 Provides Stress-Adaptive Proteostasis Buffering in Glioblastoma and Is Therapeutically Vulnerable.

Glioblastoma, isocitrate dehydrogenase (IDH)-wildtype (GBM), remains one of the most aggressive primary brain tumors, and its proteostasis machinery represents a potential therapeutic target. Here we identify HSP27 as a key regulator-associated proteostasis in glioblastoma, IDH-wildtype, where it is linked to protein synthesis, folding, stress-granule dynamics and ubiquitin-mediated turnover. Ribo-seq showed HSP27 depletion reduced global protein synthesis, while TME labeling coupled to mass spectrometry revealed increased accumulation of unfolded proteins, indicating proteotoxic stress. Proteomic analysis of isolated stress granules (SGs) revealed enhanced sequestration of translational regulators, including EIF4E, mTOR, EIF3M and QKI, into stress granules (SGs), thereby reinforcing translational repression. Ubiquitinome profiling further revealed increased ubiquitination and proteasome-dependent loss of oncogenic and translational regulators, including AKT2, PARP1, EIF4G1, EIF4A3, and DDX5. Functionally, targeting HSP27 inhibits tumor growth and sensitizes glioblastoma to translational blockade. In orthotopic models, antisense oligonucleotide targeting HSP27 in combination with Didemnin B suppressed tumor progression and prolonged survival compared with either single agent. These findings associate HSP27 with proteostasis in glioblastoma, IDH-wildtype, and suggest HSP27-dependent proteostasis buffering as a therapeutic vulnerability.