CASS4 (Cas scaffold protein family member 4) is a docking protein that functions as a scaffolding adapter in tyrosine kinase-based signaling pathways essential for cell adhesion, migration, and spreading 1. As the fourth member of the CAS protein family, CASS4 lacks enzymatic activity but contains specific recognition and binding sites for assembly of larger signaling complexes 1. The protein regulates focal adhesion kinase (FAK) activity and associates with FAK and SRC family kinases to activate downstream effectors that control the actin cytoskeleton 1. CASS4 promotes cell invasion through activation of the AKT signaling pathway, which leads to inhibition of E-cadherin expression and enhanced invasive capacity in non-small cell lung cancer cells 2. Disease relevance includes associations with Alzheimer's disease risk, where genome-wide association studies have identified CASS4 as one of the risk genes implicated in AD pathogenesis 34. The protein also shows involvement in immune system function and has been implicated in various pathological conditions including cancer, autoimmune disorders, and developmental diseases 1. Clinical significance extends to its role as a potential biomarker and therapeutic target, particularly given its involvement in cancer metastasis and neurodegeneration 5.