SDF-1 stimulation induces migration and Ral activation in MM cells. (A) The MM cell lines OPM-1 and NCI-H929, and the malignant plasma cells from a MM patient, were allowed to migrate for 4 hours in the absence (−) or presence (+) of 100 ng/mL SDF-1 in the upper or lower compartment of Trans-wells, as indicated (shown as the mean ± SD of triplicates). All relevant comparisons (eg, migration in absence versus migration in presence of SDF-1) were significantly different (P < .05), and the results are representative of 3 independent experiments and of freshly isolated malignant plasma cells from 3 MM patients. (B) NCI-H929, OPM-1, and XG-1 MM cell lines, and primary human MM cells, were stimulated for the indicated periods of time with 100 ng/mL SDF-1 and lysed, and the amount of Ral-GTP in the lysates was determined by pull-down assay (PD) using GST-RalBP-RBD fusion protein. As a control, total lysates (TLs) were immunoblotted and probed using anti-Ral antibodies. The results are representative of at least 2 independent experiments.