The DNA/RNA Helicase SETX Maintains R-Loop Homeostasis to Promote Chemoresistance in Ovarian Cancer.

Ovarian cancer is a lethal malignancy that frequently develops resistance to platinum-based chemotherapies. Elucidating the genes that regulate DNA damage repair could lead to more effective treatments for ovarian cancer. Senataxin (SETX), an RNA-DNA helicase, maintains R-loop homeostasis to ensure replication fork progression, and its deficiency is linked to neurodegenerative diseases. However, its clinical relevance to solid tumors is not understood. We aimed to investigate the clinical significance and functional role of SETX in ovarian cancer progression and chemotherapy resistance. SETX expression was analyzed in ovarian cancer tissues, followed by CRISPR-Cas9-mediated knockout, mechanistic analyses, and RNASEH1 rescue experiments to investigate its role in ovarian cancer progression and chemoresistance. SETX was significantly overexpressed in ovarian tumors, and its high expression was correlated with cisplatin resistance and poor patient survival. SETX depletion significantly impaired tumor cell proliferation and invasion and sensitized cells to cisplatin-induced apoptosis. Mechanistically, SETX deficiency triggered pathological R-loop accumulation, which was accompanied by replication stress, DNA double-strand breaks, and activation of DNA damage response. RNA-seq analysis also revealed splicing alterations and U2AF1 interaction. Critically, R-loop degradation induced by RNASEH1 overexpression rescued the DNA damage phenotype and growth defects induced by SETX loss. These findings reveal a dual oncogenic role for SETX. Maintaining R-loop homeostasis supports malignant progression while conferring chemotherapy resistance. Therefore, SETX represents a promising therapeutic target, as its inhibition simultaneously suppresses tumor growth and overcomes chemotherapy resistance in ovarian cancer.