FEN1通过SUMO1抑制Nrf2泛素化促进肝癌细胞抵抗铁死亡的机制研究

铁代谢失衡可诱导铁死亡并与肝癌进展密切相关，但其调控机制尚未阐明。我们前期报道FEN1在肝癌中高表达并促进肝癌侵袭和转移。后续转录测序及细胞实验发现FEN1非酶活性调控胞内铁离子含量并参与肝癌细胞铁死亡，机制挖掘提示该过程依赖于Nrf2。文献报道SUMO化是Nrf2重要的蛋白翻译后修饰，预实验提示SUMO1能够结合FEN1并参与FEN1对Nrf2的调控，泛素-蛋白酶体参与SUMO1对Nrf2的调控，由此我们推测，FEN1与SUMO1结合抑制Nrf2泛素化降解，减少胞内Fe2+含量并抑制Lipid ROS累积，最终抑制肝癌细胞铁死亡。本项目拟在前期工作基础上，鉴定FEN1结合SUMO1的蛋白序列位点，并构建突变体验证其对Nrf2和肝癌细胞铁死亡的调控效应，进一步利用裸鼠肝脏原位瘤模型获得体外、体内双重证据。最后，组织样本中检测表达并与临床因素做相关性和预后分析，揭示新分子靶点的临床转化意义。

Iron metabolism imbalance can induce ferroptosis and is closely related to the progression of hepatocellular carcinoma (HCC), but its regulatory mechanism has not been elucidated. We previously reported that flap endonuclease 1 (FEN1) was highly expressed in HCC and promoted invasion and metastasis of HCC. Subsequent transcriptional sequencing and cell experiments show that FEN1 regulates intracellular iron content through non enzymatic activity and participates in ferroptosis of HCC cells. Mechanism Mining hints that this process depends on nuclear factor erythroid-2 related factor 2 (Nrf2). It has been reported that sumoylation is an important post-translational modification of Nrf2. Preliminary experiments suggest that small ubiquitin-related modifier 1 (SUMO1) could bind to FEN1 and participates in the regulation of FEN1 on Nrf2. Ubiquitin proteasome is involved in the regulation of SUMO1 on Nrf2. Therefore, we speculate that FEN1 binding to SUMO1 can inhibit the ubiquitination degradation of Nrf2, reduce the intracellular Fe2+ content and inhibit lipid ROS accumulation, and ultimately inhibit the ferroptosis in hepatocellular carcinoma. Based on the previous work, this project intends to identify the protein sequence site of FEN1 binding to SUMO1, then the mutants are constructed and its regulatory effect on Nrf2 and ferroptosis are verified. The orthotopic liver tumor model in nude mice is further utilized to obtain the dual evidence in vitro and in vivo. Finally, the expression of all indexes are detected in HCC tissues, and the correlation with clinical factors and prognosis are analyzed to reveal the clinical transformation significance of the new molecular targets.