UCSF researchers discovered that Src kinase, historically considered an intracellular oncogenic driver, can be presented on the exterior membrane of tumor cells through an autophagolysosomal exocytosis mechanism. The team demonstrated that targeting extracellular Src (eSrc) with antibodies carrying cytotoxic payloads or immune‑engaging constructs shrank tumors in preclinical models. The finding opens a translational pathway to exploit a widely expressed oncogene as a tumor‑specific antigen for antibody‑based therapies. The work was published in Science and positions eSrc as a potential pan‑tumor target; clinical development will require validation of tumor selectivity, expression prevalence, and safety across indications.