Immunoblot analysis of anti-cortactin or anti-ARHGEF1 i.p. by using lysates made from ROR1+ breast-cancer PDX cells revealed that ARHGEF1 associated with cortactin (Supplementary Fig. 9a, b), and more specifically Y421-phosphorylated cortactin (Supplementary Fig. 9c). Here, CTTN is linked to breast cancer.