CAGE1 (cancer antigen 1) is a cancer-testis antigen located on chromosome 6 with protein binding capacity. As a cancer-testis antigen, CAGE1 is predominantly expressed in testicular tissue with restricted normal tissue distribution, making it a candidate immunotherapy target 1. In canine melanoma studies, CAGE1 showed only weak or absent expression in oral melanoma, distinguishing it from other CTAs like MAGE and PRAME 1. In spermatogenesis, CAGE1 was identified as a potential key regulatory gene downstream of piR-1207 and piR-2107, suggesting involvement in sperm motility and morphology 2. CAGE1 also functions as a transcriptional regulatory element; it was identified as a conserved genomic region (Cage1) capable of potently inducing FOXP3 expression when targeted by CRISPRa-mediated transcriptional activation, with therapeutic implications for immune modulation 3. Clinically, CAGE1 has relevance as a tumor-associated autoantigen in gastric cancer, where serum anti-CAGE1 autoantibodies are elevated and contribute to diagnostic panels (AUC=0.885 with six other autoantibodies) 4. CAGE1 was also identified among concurrent mutations in pulmonary benign metastasizing leiomyoma and early placental villi, indicating broader tissue involvement 5, 6. Rare deletions of CAGE1 have been associated with intellectual disability and dysmorphic features 7.