Interestingly, activation of VLA-4 and lymphocyte function-associated antigen 1 (LFA-1, which is composed of CD11a and CD18—also known as αLβ2 integrin) is triggered by CXCL12 produced by MSCs (74, 77), notably via the Janus kinase 2 (JAK2) pathway (78) but also by BCR stimulation, reinforcing the adhesive capacities of CLL B cells (79). Here, JAK2 is linked to B-cell chronic lymphocytic leukemia.