CS1 enhances MM cell adhesion to bone marrow stroma. (A) Binding of CS1-overexpressing or control MM cells to BMSCs was determined by 30-minute adhesion assay in a fluorescence plate reader. Experiments were done in triplicates, and a representative experiment was shown. a.u. indicates arbitrary units. (B) CS1 was detectable in control U266 cells after long exposure (7 minutes) compared with short exposure (40 seconds) in immunoblotting analysis. CS1 expression in U266 cells in suspension versus adherent U266 cells was analyzed by flow cytometry and immunoblotting. (C) Cell morphology and colony formation were examined in methylcellulose-based culture at 6 days after plating U266CS1 versus control U266 transfectants. Images were taken using a Leica DFC300FX with a 40×/0.6 NA objective and Leica IM50 Image Manager (original magnification, ×400). (D) Colonies were stained and visualized with a Leica DM LB research microscope and quantitated in panel E. P < .01.