CBX2 phase-separation contributes to homologous recombination repair and drug resistance in ovarian cancer.

Drug resistance jeopardizes the prognosis of high-grade serous ovarian carcinoma (HGSOC) patients via DNA damage repair-coupled mechanism. The role of biomolecular phase separation in DNA damage repair has loomed. Here we find that CBX2 condensates are associated with drug resistance and contribute to DNA double-strand break (DSB) repair in HGSOC. Specifically, CBX2 condensates facilitate the recruitment of key DSB repair factors PARP1, 53BP1, and BRCA1 to chromatin. Patients with a CBX2-negative pattern exhibit the best prognosis, followed by those with non-condensate CBX2, while the worst outcomes are observed in patients with condensate CBX2. By drug screening, Ibrutinib is identified as an effective inhibitor of HGSOC cells and patient-derived organoids with CBX2 condensates. Overall, CBX2 phase separation enhances DSB repair-mediated drug resistance in HGSOC cells, and Ibrutinib may offer a viable therapeutic option for CBX2-positive HGSOC patients.