ACRBP (acrosin binding protein) is a cancer-testis antigen with dual roles in reproductive biology and malignancy. In normal physiology, ACRBP maintains proacrosin as an enzymatically inactive zymogen within the acrosome and regulates acrosome biogenesis through alternative splicing variants 1. ACRBP-W retains proacrosin in its inactive state, while ACRBP-V5 functions in acrosomal granule formation during spermiogenesis 1. ACRBP is normally restricted to testicular tissue but is aberrantly expressed across multiple cancer types. In cancer, ACRBP expression correlates with poor prognosis. High ACRBP expression in ovarian cancer associates with reduced overall and disease-free survival 2, and the protein confers paclitaxel resistance by normalizing mitotic spindle function through interaction with NuMA 3. ACRBP is upregulated in epithelial ovarian cancer, correlating with FIGO stage and chemosensitivity 2, and is also expressed in brain tumors and liposarcomas 4. Anti-ACRBP antibodies are detected in 28.5% of ovarian cancer patients but not healthy controls, with diagnostic sensitivity/specificity of 85.71%/55.0% 2. ACRBP-specific HLA-A2-restricted peptides generate cytotoxic T lymphocyte responses, establishing preclinical foundations for peptide-based cancer vaccines 5. Additionally, ACRBP serves as a biomarker for boar sperm cryopreservation capacity and enables forensic sperm cell isolation from mixed stains 67.