PAGE5 (CT16) is a cancer-testis antigen encoded on the X chromosome X functions as an intrinsically disordered protein (IDP) with protein-binding capability 1. Structurally, PAGE5 lacks defined tertiary structure but contains molecular recognition regions that facilitate transient protein interactions 12. Functionally, PAGE5 promotes cell survival in melanoma by acting as a positive regulator of antiapoptotic genes (metallothionein 2A and interleukin 8) while suppressing pro-apoptotic dickkopf 1 (DKK1) expression in a p53-independent manner 3. PAGE5 has also been identified as a mediator of chemoresistance in small cell lung cancer 4. Disease relevance includes dysregulation through promoter hypermethylation in colorectal cancer 5 and elevated expression in advanced melanoma 3. Clinically, PAGE5 expression is part of an 11-gene signature associated with poor overall survival and disease progression in head and neck cancer 6. Additionally, autoantibodies against the PAGE protein family N-terminal fragment, including PAGE5, are associated with significantly increased schizophrenia risk in first-episode psychosis patients (odds ratio 6.7) 7. These findings suggest PAGE5 as a potential therapeutic target in multiple cancer types and a biomarker in psychiatric disorders.