Nampt is a cytoplasmic protein with prognostic relevance in bortezomib-treated MM patients. (A-B) MM cell lines, MM patients’ CD138⁺ cells, and PBMCs from healthy donors or MM patients were used to characterize subcellular distribution patterns of Nampt expression by immunofluorescence (A) or western blot analysis (B) using anti-Nampt and specific antibodies. (C) Expression levels (log₁₀ transformed) for Nampt transcript in CD138⁺ cells from MM patients after bortezomib (n = 163) or dexamethasone (n = 70) therapy, according to gene expression profile arrays generated at Millenium Pharmaceuticals (GSE9782). Nampt expression levels (Affimetrix probeset 217739_s_at) among responders (R) or nonresponders (NR) within Bz (n = 85 for R and n = 78 for NR) or Dex (n = 30 for R and n = 40 for NR) groups were plotted on the horizontal axis against the log₁₀-transformed normalized expression units on the vertical axis. For each therapy group, P values comparing R and NR are shown. (D) Kaplan–Meier overall survival curves of MM patients treated with bortezomib (n = 163) according to Nampt mRNA expression above or below the median value of 250.18, based on gene expression omnibus dataset GSE9782. The blue line indicates a patient group with lower Nampt expression and longer survival, whereas the red line represents a group of patients with higher Nampt expression and shorter survival. Bz, bortezomib; DAPI, 4,6 diamidino-2-phenylindole; Dex, dexamethasone; HMMCs, human multiple myeloma cell lines.