CDCA5 (cell division cycle associated 5, also called sororin) is a cohesin regulatory protein essential for sister chr11 cohesion during cell division. Mechanistically, CDCA5 stabilizes cohesin complex association with chr11 by antagonizing WAPL-mediated cohesin dissociation 1. At the molecular level, CDCA5 forms monomeric complexes with individual cohesin rings at sister chr11 cohesion sites, enabling co-entrapment of sister DNAs 2. CDCA5 also functions in DNA double-strand break repair and chr11 loop extrusion through cohesin dynamics regulation 3. Clinically, CDCA5 is significantly overexpressed across 22 cancer types, with elevated expression correlating to poor survival in 13 tumor types 4. In ovarian cancer, CDCA5 promotes cell invasion and migration via TGF-β1/Smad2/3 pathway activation and inhibits apoptosis while evading DNA damage responses 5. Similarly, in epithelial ovarian carcinoma, CDCA5 upregulation driven by transcription factor KLF5 promotes proliferation and metastasis while suppressing P53-mediated apoptosis 6. In hepatocellular carcinoma, CDCA5 overexpression cooperates with cell cycle regulators to promote tumor development 7. CDCA5 expression also correlates with immune cell infiltration and superior response to anti-PD-L1 immunotherapy 4, positioning CDCA5 as a promising prognostic biomarker and therapeutic target across multiple malignancies.