TMSB4X (thymosin beta 4 X-linked) encodes thymosin β4, a multifunctional protein with diverse roles in cellular processes and disease pathogenesis. The protein functions as an actin-binding protein that sequesters actin monomers and inhibits actin filament polymerization, thereby regulating cytoskeletal dynamics 1. TMSB4X serves as a potent inhibitor of bone marrow-derived stem cell differentiation by preventing hematopoietic pluripotent stem cells from entering S-phase. In cancer contexts, TMSB4X exhibits complex roles across different malignancies. It shows high expression in tumor regions of colorectal cancer and diffuse high-grade gliomas, suggesting potential utility as a tumor marker 23. In glioma progression, TMSB4X interacts with TAGLN2 and promotes angiogenesis and tumor growth 1. The protein also regulates mitophagy in lung adenocarcinoma through AMPK pathway modulation 4. Notably, TMSB4X demonstrates neuroprotective properties in Alzheimer's disease, where its expression decreases in familial AD organoids and neurons, and thymosin β4 treatment rescues neurodevelopmental deficits and reduces amyloid-β formation 5. Additionally, TMSB4X shows potential as a diagnostic biomarker in psoriatic arthritis 6 and exhibits prognostic significance in osteosarcoma 7.