Previous studies found that cortactin may be phosphorylated in breast-cancer cells of some patients,23,31 and that high levels of phosphorylated cortactin associated with enhanced cancer-cell migration, metastasis, and adverse prognosis.18,20,33 We found breast-cancer PDX that expressed high levels of ROR1 had higher levels of Y421-phosphorylated cortactin than breast-cancer PDX with low levels of ROR1 (Supplementary Fig. 1). Here, ROR1 is linked to breast carcinoma.