AXII-stimulated growth of MM.1S cells either by AKT or ERK1/2 MAPK pathways. (A) MM1.S cells (2 × 10⁶) were serum-starved for 16 hours, followed by addition of 1 μg/mL AXII for the indicated time periods. Total protein was extracted and analyzed by Western blotting. Ratios of phospho-ERK1/2 to total-ERK1/2 and phospho-AKT to total-AKT were determined by Image J. (B) MM1.S cells (2 × 10⁵) were incubated with either LY294002 (LY) or PD98059 (PD) for 1 hour followed by stimulation with AXII. After 72 hours, the total number of MM1.S cells was counted. Both LY and PD inhibited the growth of AXII-stimulated MM1.S cells. (C) BMSCs from AXII^+/+ and 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 ERK1/2 phosphorylation and total ERK1/2 levels as described in “Phosphorylation experiment.”