XAGE1B (X antigen family member 1B) is a cancer/testis antigen expressed in multiple malignancies with dual roles in tumor promotion and immune targeting. Functionally, XAGE1B promotes oncogenic cell cycle progression and inhibits apoptosis: overexpression shortens G0-G1 phase and prolongs G2-M phase while enhancing resistance to TNF-α and serum deprivation-induced apoptosis in adenoid cystic carcinoma cells 1. The gene actively drives tumor proliferation and metastatic capacity, with overexpression increasing transmembrane invasion and in vivo metastasis while promoting tumor angiogenesis 2. Clinically, XAGE1B is expressed across diverse cancers: 22.2% of acute myeloid leukemias 3, 32.9% of lung cancers with preferential expression in adenocarcinomas 4, and Ewing's family tumors 5. Its cancer/testis antigen nature renders it immunogenic, making it a therapeutic target. Vaccination studies show heteroclitic immune responses against XAGE1B in cancer patients after NY-ESO-1 immunization 6, and XAGE1B-transfected prostate cancer cells demonstrate enhanced immunogenicity with increased IFN-γ secretion and dendritic cell infiltration 7. These findings position XAGE1B as both a therapeutic target for antisense and gene-modified cell vaccines and a prognostic marker for cancer immunotherapy response, particularly in adenocarcinomas and hematologic malignancies.