XAGE1A (X antigen family member 1A) is an X-linked cancer-testis antigen that functions as a protein-binding molecule with emerging roles in cancer diagnosis and prognosis. XAGE1A expression is regulated epigenetically through DNA methylation by DNMT1 and DNMT3b enzymes, which suppress its transcription in normal cells 1. The gene is aberrantly expressed in multiple malignancies including lung cancer, colon cancer, laryngeal squamous cell carcinoma, acute myeloid leukemia, neuroblastoma, head and neck squamous cell carcinoma, and prostate cancer. Clinically, XAGE1A serves as a biomarker for cancer detection and prognosis. In lung cancer, serum anti-XAGE1A autoantibodies combined with IL2RB, CENPB, and TP53 antibodies demonstrated >65.5% sensitivity and >90% specificity for early-stage diagnosis 2. In colon cancer, XAGE1A expression correlated with favorable prognosis 3. XAGE1A was identified among core genes associated with chemotherapy sensitivity in laryngeal cancer 4 and predicted imminent relapse in childhood acute myeloid leukemia when monitored in peripheral blood 2 months before hematologic recurrence 5. In neuroblastoma with MYCN amplification, XAGE1A expression influenced prognosis 6. XAGE1A positivity in head and neck cancers correlated with lymph node metastasis and advanced stage 7. As an immunogenic cancer-testis antigen, XAGE-1b showed potential for antigen-specific immunotherapy in prostate cancer 8.