SDC1 and plasma cell myeloma: In myeloma, this initial step requires association of VLA-4 with membrane-bound Sdc1 via its DFTF motif (60) (Figure 2B), although whether this docking plays a role in the integrin’s conformational change that promotes ligand engagement, or in strengthening the adhesion by avidity modulation, or in some other step, is not yet clear.