Scientists at UCSF discovered that the oncogenic kinase Src, long thought to be exclusively intracellular, can appear on the outer membrane of many tumor cells via autophagolysosomal exocytosis. The team demonstrated that antibodies targeting extracellular Src (eSrc) can carry cytotoxic payloads or recruit immune effector cells to kill tumors in mice, and they published their findings in Science. The work revives Src as a druggable surface antigen and expands potential antibody and radioimmunotherapy strategies. eSrc is a tumor‑associated presentation mechanism arising from overwhelmed intracellular recycling in highly proliferative cancers; if validated in human samples, it could create a broadly applicable solid‑tumor target for antibody‑based modalities.