AXII-stimulated ERK1/2 and AKT phosphorylation and growth of MM1.S cells. (A) MM1.S cells were incubated with the indicated concentrations (μg/mL) of AXII as described in “Phosphorylation experiment” and cell growth was analyzed using a BrdU kit (Roche). (B) RPMI8226, U266, and ANBL-6 cells were incubated with the 1 μg/mL AXII as described in “Phosphorylation experiment” and cell growth was analyzed. (C) CD138⁺ cells (5 × 10³) from MM patients were stimulated with AXII (1 μg/mL) and cultured for 72 hours. (D) BMSCs from AXII^+/+ mice were cocultured with MM1.S cells for 48 hours. At the end of 48 hours, the MM1.S cells were separated and analyzed for proliferation as described in “Phosphorylation experiment.” (E) AXII was added to either MM1.S cells, MM1.S^shAXIIR, or MM1.S^shControl cells and cell growth was determined. (*P < .05; **P < .01; ***P < .001).