ROR1 and B-cell chronic lymphocytic leukemia: In contrast, pre-treatment of the CLL cells with ibrutinib, a BTK inhibitor that blocks CXCR4 signaling, did not inhibit the capacity of Wnt5a to enhance release of MMP-9, indicating that Wnt5a-induced ROR1-signaling promotes expression and release of MMP-9 independent of BTK or CXCR4 signaling.