食管鳞癌（ESCC）一线顺铂耐药是治疗失败和死亡的主要原因，有研究表明铁死亡抵抗是肿瘤化疗耐药重要机制。申请人既往发现NADPH生成关键酶通过维持谷胱甘肽稳态促进胃肠肿瘤铂化疗耐药，谷胱甘肽耗竭诱发脂质过氧化是铁死亡关键分子事件，但NADPH生成关键酶在ESCC铁死亡及顺铂耐药中的作用及调控机制尚不清楚。为此，我们前期通过文库筛选锁定了NADPH生成关键酶MTHFD1是ESCC铁死亡的关键负向调控分子；鉴定出了MTHFD1互作蛋白PRMT5（精氨酸甲基转移酶5）；证实了PRMT5可甲基化MTHFD1并上调其酶活性。本项目拟进一步明确PRMT5与MTHFD1互作结构域及甲基化位点；阐明MTHFD1甲基化促进ESCC铁死亡抵抗及化疗耐药机制；探求PRMT5抑制剂逆转ESCC顺铂耐药的作用，及PRMT5/甲基化MTHFD1轴在临床标本中的预后病理意义。从而为ESCC治疗及逆转耐药提供潜在靶点。

Resistance to cisplatin in the first-line treatment of ESCC is the main reason leading to therapy failure and cancer related death. Recent evidences have demonstrated that ferroptosis underlies the key mechanism of chemoresistance. Our previous studies have confirmed that key enzymes in NADPH production promote therapy-resistance of gastrointestinal tumors through maintaining the intracellular glutathione homeostasis. Glutathione depletion induced lipid peroxidation was reported as a key molecular characteristic of ferroptosis. However, roles and mechanisms of key enzymes in NADPH production in ferroptosis remain unclear. We therefore constructed a siRNA library targeting key enzymes in NADPH production and screened out MTHFD1 (methyl tetrahydrofolate reductase 1) as the critical negative regulator of ferroptosis in esophageal squamous cell carcinoma (ESCC). The arginine methyltransferase PRMT5 was identified as the MTHFD1 interacting protein. Moreover, methylation of MTHFD1 by PRMT5 resulted in upregulation of its enzymic activity. In this project, we are aiming to specify the modification site and interaction motifs between MTHFD1 and PRMT5, to clarify the roles of methylated MTHFD1 in ferroptosis and therapy-resistance, to explore the roles of PRMT5 inhibitor to reverse cisplatin resistance and the clinicopathological significance of PRMT5/methylated MTHFD1 axis in ESCC. This project will uncover underlying mechanism of ferroptosis regulation and provide potential targets for therapeutic strategy to reverse chemoresistance in ESCC.