RUVBL1 supports TIP60-associated proteasome adaptation and temozolomide resistance in glioblastoma.

BACKGROUND

Glioblastoma (GBM) remains highly lethal, and resistance to temozolomide (TMZ) is a major barrier to durable therapeutic response. Although MGMT-mediated DNA repair is a well-established mechanism of TMZ resistance, how GBM cells maintain proteostasis under sustained chemotherapy stress remains less defined.

METHODS

We analyzed RUVBL1 expression and clinical relevance in glioma datasets from TCGA and validation cohorts. Functional studies were performed using RUVBL1 knockdown, TMZ-resistant GBM cells, proteasome activity assays, protein aggregation analysis, ER stress assessment, and rescue experiments with wild-type or ATPase-deficient RUVBL1 constructs. The therapeutic effect of pharmacological RUVBL1/2 ATPase inhibition was evaluated using CB-6644 in combination with TMZ in vitro and in orthotopic xenograft models.

RESULTS

RUVBL1 was upregulated in gliomas and associated with higher tumor grade, aggressive molecular features, and poorer patient survival. In TMZ-resistant GBM cells, RUVBL1 supported elevated proteasome-related gene expression and proteasome activity. RUVBL1 knockdown impaired this adaptive proteostasis program, leading to protein aggregate accumulation, ubiquitinated protein buildup, ER stress activation, and enhanced TMZ-induced apoptosis. Mechanistically, RUVBL1 interacted with TIP60 and was associated with maintenance of H3K9/K27 acetylation, NRF1-related proteasome gene expression, and proteasome activity. Rescue experiments showed that wild-type RUVBL1, but not the ATPase-deficient D302N mutant, restored these effects, indicating the requirement of RUVBL1 ATPase activity. Pharmacological inhibition of the RUVBL1/2 ATPase complex by CB-6644 sensitized TMZ-resistant GBM cells to TMZ. In orthotopic xenograft models, CB-6644 combined with TMZ reduced tumor growth and extended survival without obvious systemic toxicity.

CONCLUSIONS

RUVBL1 contributes to TMZ resistance in GBM by supporting TIP60-associated proteasome adaptation and proteostasis maintenance under chemotherapy stress. Targeting the RUVBL1/2 ATPase complex may weaken this adaptive program and enhance TMZ efficacy, suggesting a proteostasis-related therapeutic vulnerability in TMZ-resistant GBM.