Glioblastoma (GBM) cells require high levels of nicotinamide adenine dinucleotide (NAD) to fuel metabolic reactions, regulate their cell cycle and support DNA repair in response to chemotherapy and radiation. Inhibition of a key enzyme in NAD biosynthesis, NAMPT, has demonstrated significant anti-neoplastic activity. Here, we sought to characterise NAD biosynthetic pathways in GBM to determine resistance mechanisms to NAD inhibitors. GBM cells were treated with the NAMPT inhibitor FK866 with and without NAD precursors, and were analysed by qPCR, Western blot and proliferation assays (monolayer and spheroid). We also measured changes in the cell cycle, apoptosis, NAD/NADH levels and energy production. We performed orthoptic xenograft experiments in athymic nude mice to test the efficacy of FK866 in combination with temozolomide (TMZ). We show that the expression of key genes involved in NAD biosynthesis is highly variable across GBM tumours. FK866 inhibits proliferation, reduces NAD levels and limits oxidative metabolism, leading to G2/M cell cycle arrest; however, this can be reversed by supplementation with specific NAD precursors. Furthermore, FK866 potentiates the effects of radiation and TMZ in vitro and in vivo. NAMPT inhibitors should be considered for the treatment of GBM, with patients stratified based on their expression of key enzymes in other NAD biosynthetic pathways.
胶质母细胞瘤（GBM）细胞需要高水平的烟酰胺腺嘌呤二核苷酸（NAD）来驱动代谢反应、调控细胞周期，并在化疗和放疗后支持DNA修复。抑制NAD生物合成中的关键酶NAMPT已显示出显著的抗肿瘤活性。本研究旨在阐明GBM中NAD生物合成途径，以确定其对NAD抑制剂的耐药机制。通过使用NAMPT抑制剂FK866单独或联合NAD前体处理GBM细胞，并采用qPCR、Western印迹和增殖实验（单层及球体培养）进行分析。同时检测了细胞周期、凋亡、NAD/NADH水平及能量产生的变化。通过裸鼠原位移植瘤实验评估FK866联合替莫唑胺（TMZ）的疗效。结果显示，参与NAD生物合成的关键基因在GBM肿瘤中表达高度异质。FK866能抑制细胞增殖、降低NAD水平并限制氧化代谢，导致G2/M期细胞周期阻滞；但该作用可通过补充特定NAD前体逆转。此外，FK866在体外和体内均能增强放疗与TMZ的疗效。NAMPT抑制剂应考虑用于GBM治疗，并建议根据患者其他NAD生物合成途径关键酶的表达水平进行分层治疗。
Distinct Capabilities in NAD Metabolism Mediate Resistance to NAMPT Inhibition in Glioblastoma
肿瘤(癌症)患者之家