Wnt-3a induces migration and invasion by MM cell lines and CD138⁺primary plasma cells. MM cells (H929 [A,C] and OPM-2 [B,D]) were starved in serum-free medium for 3 hours and added to transwell chambers containing a polycarbonate pore membrane (5-μM pore size) on which HUVECs (A-B) or bone marrow stromal cell lines (C-D) were pregrown for 24 hours. Wnt-3a CM diluted in con-CM (vol/vol) (A-B) or undiluted (C-D,E) was added to the lower chamber and after 4 hours of incubation cells in lower chamber were harvested and counted. The results are shown as mean ± SE (n = 3). Results are representative of 3 independent experiments. Primary plasma cells purified from bone marrow of patients with myeloma (E) were assayed for transmigration through HS-5 bone marrow stromal cell as described for panel C using IGF-I as a positive control for migration. The results are shown as mean ± SE (n = 3). ^*P < .05, ^**P < .01, ^***P < .001 versus control.