ROR1 and cancer: HS1 also can complex with ROR1 at proline 841 to enhance chemokine-directed migration of CLL cells in response to Wnt5a.15,16 HS1 is not expressed in cancers derived from non-hematopoietic cells, such as breast cancer.17 Instead, we find that the ROR1–cortactin interaction is critical for enhanced migration and metastasis of breast-cancer cells independent of expression of HS1.