CTTN and breast cancer: Amplification of the gene encoding cortactin is observed in at least 15% of metastatic breast carcinomas.31,32 High-level breast-cancer-cell expression and phosphorylation of cortactin associates with an unfavorable prognosis for patients with breast cancer.33–36 In this study, we examined whether Wnt5a could stimulate ROR1 to complex with cortactin and thereby recruit and activate ARHGEF1 to enhance activation of RhoA and promote breast-cancer-cell migration/metastasis.