Respiratory Center, Asahikawa Medical University, Asahikawa, Hokkaido, Japan.
J Thorac Oncol. 2012 Jan;7(1):49-56. doi: 10.1097/JTO.0b013e318233d686.
Non-small cell lung cancer (NSCLC) often has an epidermal growth factor receptor (EGFR) gene mutation. Growth of EGFR-gene-mutated NSCLC depends predominantly on EGFR signaling and requires a large amount of intracellular ATP to activate EGFR signal transduction. Nicotinamide phosphoribosyltransferase (NAMPT) is a rate-limiting enzyme in nicotinamide adenine dinucleotide biosynthesis, and it regulates intracellular ATP levels in mammalian cells. The effect of NAMPT inhibition on NSCLC has not been completely understood.
We aimed to clarify the hypothesis that NAMPT inhibition suppresses growth of EGFR-gene-mutated NSCLC through reduction of intracellular ATP levels, using NAMPT-siRNA transfection and NAMPT inhibitor FK866. We used four lung adenocarcinoma cell lines, including H358 (Wild type EGFR), LC2 (EGFR), PC9 (EGFR), and H1975 (EGFR), and evaluated the effect of FK866 on these cells and its mechanisms, using cell proliferation, Western blot, ATP, and apoptosis assay.
We found that (1) H358, LC2, and H1975 cell lines highly expressed NAMPT-mRNA; (2) NAMPT-specific siRNA and FK866 suppressed proliferation of these NSCLCs; (3) FK866 reduced intracellular ATP levels in H1975 cells; (4) FK866 dephosphorylated EGFR signal proteins, including EGFR, Akt, Map kinase kinase 1/2, and extracellular signal-regulated kinase 1/2 (ERK 1/2); (5) FK866 induced apoptosis of H1975 cells; and (6) FK866 suppressed growth of H1975 xenograft tumors and attenuated expression of phospho-ERK 1/2 in the tumors in a tumor-bearing mouse model.
These findings indicate that NAMPT is a potent therapeutic target in the treatment of EGFR-gene-mutated NSCLC.
非小细胞肺癌（NSCLC）常存在表皮生长因子受体（EGFR）基因突变。EGFR 基因突变型 NSCLC 的生长主要依赖于 EGFR 信号，需要大量的细胞内 ATP 来激活 EGFR 信号转导。烟酰胺磷酸核糖转移酶（NAMPT）是烟酰胺腺嘌呤二核苷酸生物合成的限速酶，它调节哺乳动物细胞内的 ATP 水平。NAMPT 抑制对 NSCLC 的影响尚未完全阐明。
我们旨在通过降低细胞内 ATP 水平，用 NAMPT-siRNA 转染和 NAMPT 抑制剂 FK866 来验证 NAMPT 抑制通过减少细胞内 ATP 水平抑制 EGFR 基因突变型 NSCLC 生长的假说。我们使用了包括 H358（野生型 EGFR）、LC2（EGFR）、PC9（EGFR）和 H1975（EGFR）在内的四种肺腺癌细胞系，评估了 FK866 对这些细胞的作用及其机制，包括细胞增殖、Western blot、ATP 和凋亡检测。
我们发现：（1）H358、LC2 和 H1975 细胞系高表达 NAMPT-mRNA；（2）NAMPT 特异性 siRNA 和 FK866 抑制这些 NSCLC 的增殖；（3）FK866 降低 H1975 细胞内的 ATP 水平；（4）FK866 使 EGFR 信号蛋白磷酸化，包括 EGFR、Akt、Map kinase kinase 1/2 和细胞外信号调节激酶 1/2（ERK 1/2）去磷酸化；（5）FK866 诱导 H1975 细胞凋亡；（6）FK866 抑制 H1975 异种移植瘤的生长，并在荷瘤小鼠模型中减弱肿瘤中磷酸化 ERK 1/2 的表达。
这些发现表明 NAMPT 是治疗 EGFR 基因突变型 NSCLC 的一种潜在治疗靶点。
