Esophageal squamous cell carcinoma (ESCC) is a common malignant tumor with poor prognosis. And different individuals respond to the same drug differently. Increasing evidence has confirmed that metabolism reprogramming was involved in the drug sensitivity of tumor cells. However, the potential molecular mechanism of 5‐fluorouracil (5‐FU) sensitivity remains to be elucidated in ESCC cells. In this study, we found that the 5‐FU sensitivity of TE1 cells was lower than that of EC1 and Eca109 cells. Gas chromatography‐mass spectrometry analysis results showed that nicotinate and nicotinamide metabolism and tricarboxylic acid cycle were significantly different in these three cell lines. Nicotinamide N‐methyltransferase (NNMT), a key enzyme of nicotinate and nicotinamide metabolism, was significantly higher expressed in TE1 cells than that in EC1 and Eca109 cells. Therefore, the function of NNMT on 5‐FU sensitivity was analyzed in vitro and in vivo. NNMT downregulation significantly increased 5‐FU sensitivity in TE1 cells. Meanwhile, the glucose consumption and lactate production were decreased, and the expression of glycolysis‐related enzymes hexokinase 2, lactate dehydrogenase A, and phosphoglycerate mutase 1 were downregulated in NNMT knockdown TE1 cells. Besides, overexpression of NNMT in EC1 and Eca109 cells caused the opposite effects. Moreover, when glycolysis was inhibited by 2‐deoxyglucose, the roles of NNMT on 5‐FU sensitivity was weakened. In vivo experiments showed that NNMT knockdown significantly increased the sensitivity of xenografts to 5‐FU and suppressed the Warburg effect. Overall, these results demonstrated that NNMT decreases 5‐FU sensitivity in human ESCC cells through promoting the Warburg effect, suggesting that NNMT may contribute to predict the treatment effects of the clinical chemotherapy in ESCC.

中文翻译：

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烟酰胺N-甲基转移酶通过代谢重编程和促进Warburg效应降低人食道鳞状细胞癌中的5-氟尿嘧啶敏感性。

食管鳞状细胞癌（ESCC）是一种常见的恶性肿瘤，预后较差。不同的人对同一药物的反应也不同。越来越多的证据证实，代谢重编程与肿瘤细胞的药物敏感性有关。然而，在ESCC细胞中5-氟尿嘧啶（5-FU）敏感性的潜在分子机制仍有待阐明。在这项研究中，我们发现TE1细胞的5-FU敏感性低于EC1和Eca109细胞。气相色谱-质谱分析结果表明，这三种细胞系中的烟酸酯和烟酰胺代谢和三羧酸循环显着不同。烟酰胺N-甲基转移酶（NNMT）是烟酸和烟酰胺代谢的关键酶，在TE1细胞中的表达明显高于在EC1和Eca109细胞中的表达。因此，在体外和体内分析了NNMT对5-FU敏感性的作用。NNMT的下调显着增加了TE1细胞中5–FU的敏感性。同时，在NNMT敲低的TE1细胞中，葡萄糖的消耗和乳酸的产生减少，糖酵解相关酶己糖激酶2，乳酸脱氢酶A和磷酸甘油酸突变酶1的表达下调。此外，NNMT在EC1和Eca109细胞中的过表达引起相反的作用。此外，当糖酵解被2-脱氧葡萄糖抑制时，NNMT对5-FU敏感性的作用减弱。体内实验表明，NNMT敲低显着提高了异种移植物对5-FU的敏感性，并抑制了Warburg效应。总体，