The cellular kinase Src (or c-Src) plays a role in cell adhesion, motility and proliferation. In cancers, its expression and activity are often elevated, promoting the malignant properties of tumors across different types.[1] A study by Delaveris et al. on page 1124 of this issue of Science shows that many cancer cells with high Src expression also produce extracellular Src (e-Src) that reaches the outer surface of the cell membrane.[1] This exposed e-Src has been successfully targeted by immunotherapy in preclinical tumor models.[1] The discovery highlights a new therapeutic option because Src is not normally found on the outside of the plasma membrane.[1]