抑制烟酰胺磷酸核糖转移酶(NAMPT)损害细胞活力、影响能量代谢、诱导DNA损伤，并在神经母细胞瘤临床前模型中驱动肿瘤消退

Cancer cell metabolism is altered to meet increased metabolic demands of proliferating cancer cells. Reprogrammed metabolic pathways represent cell type and context specific therapeutic opportunities. Targeting NAD + production via inhibition of the NAD + salvage pathway presents one potential opportunity, as NAD + is essential for energy metabolism and other downstream processes. Presently, NAMPT is the only clinically targetable enzyme in this pathway. We conducted a high-throughput cancer cell line screen and identified that neuroblastoma (NB) cells are significantly more sensitive to NAMPT inhibitors (NAMPTis) than most other solid tumors, with IC50 values >20-fold less than the cell line panel average. NB is the most common extracranial solid tumor in children, accounting for 15% of pediatric cancer deaths. We used 2 clinical NAMPTis under early phase study (OT-82 and KPT-9274) to validate our drug screen results in 10 molecularly diverse NB cell lines including 2 NB PDX-derived cell lines. We investigated the mechanistic effects of NAMPT inhibition on NAD + -dependent pathways and analyzed the in vivo effects of OT-82 in 3 orthotopic NB models. Treatment of NB cell lines with NAMPTis results in failure of cells to proliferate following replacement with drug-free media at 48h, suggesting irreversible cell death. Furthermore, NAMPTi treatment results in neither apoptotic nor necroptotic cell death but induces autophagy. NAMPTis reduce intracellular NAD + levels and co-treatment with NMN, the product of NAMPT, fully rescues cell viability, verifying NAD + -dependence and on-target activity of each NAMPTi. Moreover, we observed reductions in ATP of 50% and >90% after 24h and 72h of treatment, respectively. Examination of drug effects on glucose metabolism using extracellular flux and metabolomics analyses demonstrated cell line-specific effects, including reduction in oxidative phosphorylation and/or glycolysis with depletion of metabolites produced via NAD + -consuming enzymes. Investigation of the effects of NAMPTis on other key NAD + consuming enzymes including sirtuin 1 (SIRT1) and poly (ADP-ribose) polymerase (PARP), demonstrated significant loss of activity of both enzymes in a time-dependent manner. As loss of PARP and SIRT1 activity can compromise DNA repair, comet assays were used to assess the extent of DNA damage, revealing increased DNA damage upon NAMPTi treatment in all models. In vivo studies of OT-82 in orthotopic xenografts demonstrated significant tumor shrinkage. Across models, 23/26 mouse tumors had average volume reductions of 67% (range 10%-99%). Together, these data demonstrate that in NB, multiple critical pathways are impacted by the loss of NAD + mediated by NAMPT inhibition and suggest NAMPTis may have translational potential as a novel agent against NB.