Nampt as therapeutic target in MM cells. (A) Expression of Nampt in multiple myeloma (MM) cell lines, patient MM CD138⁺ cells, and peripheral blood mononuclear cells (PBMCs) from healthy donors or MM patients. Whole-cell lysates were subjected to immunoblotting with anti-Nampt antibody. Anti-GAPDH monoclonal antibody served as a loading control. Relative expression in MM cell lines was calculated as the ratio of the densitometry signal for Nampt relative to GAPDH in each sample using ImageJ Version 1.37 software (National Institutes of Health, http://rsb.info.nih.gov/ij/). (B) Dose-response effect in 18 human MM cell lines treated with FK866 (0-30nM for 96 hours). The percentage survival (expressed as percentage of the vehicle-treated control) is visualized in color format according to their values on a linear scale (0%-100%). Data presented are means ± SD of 3 experiments. (C) Relative expression of Nampt protein plotted versus 96h Fk866 cytotoxicity IC₅₀ values. The Pearson correlation coefficient (r) and the P value, calculated using GraphPad Prism Version 5 analysis software are indicated.