Dispensary of Traditional Chinese Medicine, The First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, Zhejiang, China (mainland).
Department of Respiration, Quzhou People's Hospital, Quzhou, Zhejiang, China (mainland).
Med Sci Monit. 2018 Oct 21;24:7499-7507. doi: 10.12659/MSM.910265.
BACKGROUND Non-small cell lung cancer (NSCLC) accounts for about 85% of all types of lung cancer. Methylenetetrahydrofolate dehydrogenase 1 (MTHFD1) is involved in DNA methylation, and DNA methylation is related to tumorigenesis. The role of MTHFD1 in NSCLC was examined in our study. MATERIAL AND METHODS The correlation between the expression of MTHFD1 and the clinicopathological features of patients diagnosed with lung cancer was investigated using the chi-square test. The viability and apoptosis of NCI-H1299 cells was respectively detected using cell counting kit-8 and flow cytometry assays. The expression levels of MTHFD1, apoptosis-related factors and DNA methyltransferase-related factors were assessed by quantitative real-time PCR (qRT-PCR) and western blot assays. RESULTS We found that MTHFD1 expression in the tumor tissues and cells was higher than that of adjacent normal tissues and cells. The survival time of patients with high MTHFD1 expression was shorter than those with low MTHFD1 expression. The expression level of MTHFD1 was related to tumor size, TNM stage, histologic grade, and metastasis, but not linked to gender and age. Besides, si-MTHFD1 significantly decreased the viability of cells in a time-dependent manner, and increased cell apoptosis. When cells were transfected with MTHFD1-siRNA, the levels of surviving and B-cell lymphoma-2 (Bcl-2) were attenuated, while p53 and Bcl-2 associated X protein (Bax) levels were enhanced. Moreover, si-MTHFD1 markedly downregulated the expression levels of DNA methyltransferase 1 (DNMT1), DNMT3a, and DNMT3b. CONCLUSIONS Collectively, our results proved that MTHFD1 silencing obviously reduced the proliferation and enhanced the apoptosis of NSCLC via suppressing DNA methylation.
非小细胞肺癌（NSCLC）约占所有肺癌类型的 85%。亚甲基四氢叶酸脱氢酶 1（MTHFD1）参与 DNA 甲基化，而 DNA 甲基化与肿瘤发生有关。本研究旨在探讨 MTHFD1 在 NSCLC 中的作用。
采用卡方检验研究 MTHFD1 表达与肺癌患者临床病理特征的相关性。通过细胞计数试剂盒-8 和流式细胞术分别检测 NCI-H1299 细胞的活力和凋亡。通过定量实时 PCR（qRT-PCR）和 Western blot 检测 MTHFD1、凋亡相关因子和 DNA 甲基转移酶相关因子的表达水平。
我们发现肿瘤组织和细胞中的 MTHFD1 表达高于相邻正常组织和细胞。MTHFD1 高表达患者的生存时间短于 MTHFD1 低表达患者。MTHFD1 的表达水平与肿瘤大小、TNM 分期、组织学分级和转移有关，但与性别和年龄无关。此外，si-MTHFD1 可显著降低细胞活力，并增加细胞凋亡。当细胞转染 MTHFD1-siRNA 时，存活蛋白和 B 细胞淋巴瘤-2（Bcl-2）的水平降低，而 p53 和 Bcl-2 相关 X 蛋白（Bax）的水平升高。此外，si-MTHFD1 明显下调了 DNA 甲基转移酶 1（DNMT1）、DNMT3a 和 DNMT3b 的表达水平。
总之，我们的研究结果证明，MTHFD1 沉默通过抑制 DNA 甲基化显著降低了 NSCLC 的增殖并增强了其凋亡。
