PAG1 (phosphoprotein membrane anchor with glycosphingolipid microdomains 1) is a transmembrane adaptor protein that functions as a critical regulator of cellular signaling and cancer biology. In immune cells, PAG1 negatively regulates T-cell receptor signaling by promoting CSK activation and recruitment to lipid rafts, resulting in LCK inhibition 1. The protein directs SRC-family kinase intracellular localization, controlling their activity and mediating receptor tyrosine kinase-induced differentiation in neuronal cells 1. In cancer contexts, PAG1 exhibits complex roles. It promotes radioresistance in laryngeal carcinoma through STAT3 activation and integrin β1 complex formation 2, and stimulates proliferation and metastasis in nasopharyngeal carcinoma by downregulating PTEN 3. Conversely, PAG1 overexpression suppresses proliferation, anchorage-independent growth, and invasive ability in prostate cancer cells 4. Genome-wide association studies have identified PAG1 variants associated with bladder cancer risk, particularly in interaction with smoking 5. PAG1 has also been implicated as a necroptosis-related biomarker in diabetic nephropathy 6. These findings highlight PAG1's context-dependent roles in cellular signaling, cancer progression, and disease susceptibility.