Clinical Report: Inhibition of Proteasome Activity Triggers a BRCAness Phenotype

Overview

This study demonstrates that proteasome inhibitors, particularly ixazomib citrate, can sensitize homologous recombination-proficient (HRP) ovarian cancer models to PARP inhibitors by inducing a BRCAness phenotype.

Background

Ovarian cancer is a leading cause of cancer-related mortality among women, with high-grade serous ovarian cancer often exhibiting homologous recombination proficiency (HRP). PARP inhibitors have shown significant benefits in HR-deficient tumors, but their effectiveness in HRP tumors is limited. Understanding mechanisms to induce a functional HRD-like state in HRP tumors is crucial for expanding treatment options.

Data Highlights

Key Findings

• Proteasome inhibitors were identified as the most effective sensitizing agents in HRP ovarian cancer models.
• Ixazomib citrate disrupted RAD51 recruitment to DNA damage sites, inducing a BRCAness phenotype.
• Combination therapy with ixazomib citrate and olaparib significantly suppressed tumor growth in xenograft models.
• Proteasome inhibition enhanced tumor-surface MHC class I expression, potentially increasing immune recognition.
• In vitro assays indicated increased susceptibility to CD8+ T-cell-mediated killing following proteasome inhibition.

Clinical Implications

Further exploration in clinical settings is warranted to validate these preclinical results.

Conclusion

Proteasome inhibition sensitizes HRP ovarian cancer to PARP inhibitors.

Related Resources & Content

1. The ASCO Post, 2015 -- PARP Inhibitors: The First Potential Treatment of Hereditary Ovarian Cancers
2. The ASCO Post, 2025 -- Study Identifies Biologic Reasons for Selective Benefit of PARP Inhibitors
3. Frontiers in Immunology, 2026 -- PARylation-centric crosstalk: orchestrating immune evasion and multidrug resistance in ovarian cancer
4. The ASCO Post — PARP Rechallenge Slows Ovarian Cancer Progression in Platinum-Sensitive Disease KEY POINTS Related Articles
5. NCCN Ovarian Cancer Guidelines
6. Overall Survival With Maintenance Olaparib at a 7-Year Follow-Up