ACTN1 (actinin alpha 1) is an F-actin cross-linking cytoskeletal protein that anchors actin filaments to intracellular structures and regulates actin filament organization and bundle assembly. Beyond its canonical cytoskeletal role, ACTN1 has emerged as a critical oncogenic driver across multiple cancer types. In head and neck squamous cell carcinoma, ACTN1 promotes tumorigenesis and cisplatin resistance by enhancing MYH9-dependent GSK-3Ξ² degradation and activating integrin Ξ²1-mediated FAK/PI3K/AKT signaling, with high expression correlating with poor chemotherapy response and reduced overall survival 1. In triple-negative breast cancer, elevated ACTN1 confers chemoresistance and survival advantages in basal epithelial subpopulations 2. Similarly, in thyroid carcinoma, ACTN1 overexpression promotes cell proliferation, migration, invasion, and epithelial-mesenchymal transition through PI3K/AKT/mTOR pathway activation, correlating with metastasis and poor prognosis 3. In glioblastoma, USP14-mediated stabilization of ACTN1 maintains mesenchymal characteristics and drives proneural-to-mesenchymal transition, with elevated expression predicting poor survival 4. Clinically, ACTN1 also serves as a serum extracellular vesicle biomarker for cholangiocarcinoma prognosis 5. Genetically, pathogenic ACTN1 variants cause autosomal dominant macrothrombocytopenia through actin network disorganization 6, and functional compensation by ACTN1 occurs in PLS3-related bone disorders 7.