SHC4 (SHC adaptor protein 4) is a signaling adaptor protein that functions as a key regulator in both developmental and pathological processes. Primary function: SHC4 activates Ras-dependent and Ras-independent migratory pathways and regulates receptor tyrosine kinase signaling 1. Mechanism: SHC4 interacts with Src kinase and maintains its autophosphorylated activation state, which activates β-catenin independent of canonical Wnt signaling, subsequently upregulating metastasis-associated genes CD44 and MMP7 1. Additionally, SHC4 enhances mesenchymal stem cell migration and hematopoietic niche establishment 2. Disease relevance: SHC4 is upregulated in triple-negative breast cancer (TNBC) with high expression correlating to poor prognosis and increased metastatic potential 1. SHC4 regulates BDNF-induced MAPK activation and has been associated with depressive symptoms severity in bipolar disorder 3. SHC4 is also implicated in prostate cancer progression through regulation of extracellular vesicle secretion 4, and differentially methylated regions of SHC4 associate with general psychopathology in childhood 5. Clinical significance: SHC4 represents a potential prognostic marker and therapeutic target in TNBC 1, with targeting its interaction with Src kinase offering a novel therapeutic strategy for aggressive cancers.