NAD⁺ biosynthesis of MM cells predominantly relies on PH and salvage pathways, and its dysregulation predicts the clinical outcome. (A) Box plot of expression levels for indicated NAD⁺ biosynthetic genes in MM samples included in the CoMMpass study. Red, green, and purple bars represent de novo, PH-, and salvage pathway–related genes, respectively. Orange bars represent genes shared by all the NAD⁺-generating pathways. The abscissa represents the gene name, whereas the ordinate displays its expression as log₁₀ transcripts per million (TPM). (B) Immunohistochemical analysis of a representative BM biopsy collected from patients with NDMM. Hematoxylin and Eosin (H&E), GIEMSA staining, along with CD138, NADSYN, NAPRT, and NAMPT markers are shown (scale bar is 100 μm). (C) Perturbation effects of NAD⁺-producing enzymes expressed as CERES score across MM cell lines assessed via genomic CRISPR screening as part of the DepMap project. A CERES score of −1 identifies an essential gene. NAMPT and NAPRT have the highest dependency in MM cells. (D) Heat map of 797 patients with MM included in the CoMMpass study ordered in 3 groups by standardizing a NADome signature with a “min-max” method. Genes are categorized as either NAD⁺ consumers or producers, which are assigned to specific NAD⁺ biosynthetic pathways as in panel A. (E) Kaplan-Meier curves showing the prognostic impact of NADome signature, in terms of PFS and OS, using the CoMMpass data set. Log-rank test is used to compute the P value. Patients with high, intermediate (Int), and low MM expressing the signature are respectively reported in red, green, and blue. (F) Flux values of indicated NAD⁺ biosynthetic reactions obtained after integrating the MM-NADnet model with transcriptome data from patients with MM . The x-axis represents reactions, and the y-axis represents log₂ flux values (μM/sec). Orange, green, light blue, and purple bars represent de novo– (R6a and R7), de novo–PH shared– (R8, R10 and R11), PH (R9), and salvage pathway–related (R19, R21, and R24) reactions, respectively. (G) Correlogram between gene log₂ fold change (FC) values and metabolite log₂ FC values. Rows represent metabolites and columns represent genes. The red color corresponds to positive correlation, the blue color corresponds to negative correlation, the area covered in the square corresponds to the absolute value of the correlation, and the black squares correspond to significant correlations (P < .05). (H) Analysis of NADome, NAMPT, and NAPRT expression in the CoMMpass database across patients with MM carrying indicated cytogenetic abnormalities. The expression of the NADome signature was standardized using the min-max method (gene based), and the mean gene set variation analysis (GSVA) score was subsequently calculated. The NAPRT and NAMPT expression data (expressed as log₂ [TPM +1]) were obtained by selecting baseline expression data for each patient. Statistical significance between patient groups was calculated using the nonparametric Kolmogorov-Smirnov test; P value is indicated in each insert.