ROR1 and acute lymphoblastic leukemia: Since its identification in 1992, a pro-tumourigenic role for ROR1 signalling has been established in a growing list of both haematological malignancies (including chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL) and acute lymphoblastic leukemia (ALL)), and solid tumours (including ovarian, endometrial, lung and chemotherapy-resistant breast cancer [4,5,6,7,8,9,10].