Human myeloma cells express ADAM-9. (A) Western blot analysis of ADAM-9 expression in human myeloma cells demonstrated a single product. (B) Flow cytometric analysis of ADAM-9 expression (red histograms) in RPMI-8226 cells demonstrated expression in both permeabilized (Perm) and nonpermeabilized (Nonperm) cells when compared with an isotype control (blue histograms). (C) Two-color fluorescence immunocytochemical analysis of bone marrow mononuclear cells demonstrated expression of the restricted light chain (red) staining in a proportion of mononuclear cells. Light chain–positive cells were shown to stain positively for ADAM-9 (green). Nuclei were counterstained with DAPI and examined at an objective magnification of × 40 (0.7 numeric aperture [NA]). (D) Flow cytometric analysis of bone marrow mononuclear cells showing cIgLC^- and cIgLC⁺ staining. (E) Flow cytometric analysis demonstrated ADAM-9 expression in both cIgCL^- (green histogram) and cIgLC⁺ (red histogram) cells. (F) Analysis of mean fluorescence values (±95% CI) for cIgCL^- and cIgCL⁺ cells isolated from patients with multiple myeloma demonstrated significantly greater expression in cIgLC⁺ cells. ^*P < .01 by Wilcoxon matched pairs test.