YES1 is a non-receptor tyrosine kinase of the Src family that regulates multiple cellular processes including proliferation, survival, migration, and cell-cell adhesion 1. Upon stimulation by receptor tyrosine kinases, YES1 phosphorylates downstream substrates to promote signaling cascades; notably, it drives membrane anchoring of SRC/YES1 complexes that activate MAPK pathways 2. YES1 participates in the Hippo signaling pathway through YAP regulation, influencing cell proliferation and differentiation 3. In cancer biology, YES1 is amplified or overexpressed in approximately 31-26% of small cell lung cancer cases and various solid tumors, where it promotes cell proliferation and metastasis 41. YES1 elevation correlates with poor prognosis and serves as an independent prognostic predictor 4. Mechanistically in cancer, YES1 activates YAP-dependent transcriptional pathways that drive tumor progression 56. Clinically, YES1 inhibition through novel inhibitors like CH6953755 or dasatinib shows promising antitumor activity in preclinical models and patient-derived xenografts 4. Circulating YES1 in plasma exosomes represents a potential biomarker for patient selection and monitoring 4. YES1 represents an emerging druggable oncogenic target, particularly in cancers with elevated expression 1.