SOX2转录上调SLC7A11促进肿瘤干细胞抵抗铁死亡的机制研究

Cancer stem cells play a key role in tumor initiation, metastasis and drug resistance. Iron is an essential trace element for life, which is very important for cell growth and proliferation, whereas excessive iron can promote ROS production and lead to ferroptosis. Some studies has shown that the content of free-iron in cancer stem cells is significantly higher than that in bulk tumor cells, whereas the mechanism of resistance to iron-induced ferroptosis in cancer stem cells remains elusive. Cystine plays a pivotal role in intracellular glutathione synthesis and anti-ferroptosis, the expression regulation of cystine transporter SLC7A11 is tightly relevance to ferroptosis. The applicant's previous study found that: (1) SLC7A11 is enriched in cancer stem cells; (2) screening and validating that the stem cell transcriptional factor SOX2 could bind to SLC7A11 promoter directly and activate its expression; (3) SOX2 could enhance cystine uptake and glutathione synthesis, thus protect cells from ferroptosis. Based on this, the project proposes that cancer stem cells transcriptionally up-regulate the expression of SLC7A11 through SOX2 and uptake more cystine to protect cancer stem cells from ferroptosis. The applicant intends to further study the mechanism and function of SOX2-SLC7A11 pathway mediating resistance to ferroptosis of cancer stem cells and tumorigenesis, so as to provide a new theoretical basis and drug targets for cancer stem cell targeted therapy.

肿瘤干细胞在肿瘤的发生、转移及耐药中发挥关键作用。铁元素是生命必需的微量元素，对细胞的生长和增殖至关重要，而铁过量则会诱导ROS产生并导致铁死亡。研究表明肿瘤干细胞内游离铁含量显著增高，但其如何抵抗铁过量诱发的铁死亡仍不清楚。胱氨酸是细胞内合成谷胱甘肽并抵抗铁死亡的关键分子，胱氨酸转运体SLC7A11的表达与铁死亡密切相关。申请人前期研究发现：（1）SLC7A11在肿瘤干细胞中富集；（2）筛选并验证干性转录因子SOX2可直接结合到SLC7A11的启动子区激活其表达；（3）SOX2可增强胱氨酸摄取和谷胱甘肽合成，保护细胞抵抗铁死亡。基于此，本项目提出：肿瘤干细胞可通过SOX2转录上调SLC7A11的表达，增加胱氨酸的摄入，抵抗铁死亡的发生。申请人拟进一步深入研究上述机制，探索其在介导肿瘤干细胞抵抗铁死亡和肿瘤发生中的功能，为肿瘤干细胞靶向治疗提供新的理论基础和药物靶点。

利用小分子药物诱导肿瘤细胞铁死亡是肿瘤治疗的有效策略，然而部分肺癌会对铁死亡诱导药物产生耐药性。肿瘤干细胞在肿瘤的发生、转移及耐药中发挥关键作用。研究表明肿瘤干细胞内游离铁含量显著增高，但其如何抵抗铁过量诱发的铁死亡仍不清楚。解析肿瘤干细胞抵抗铁死亡的机制将为肿瘤干细胞靶向治疗提供新的理论基础和药物靶点。胱氨酸是细胞内合成谷胱甘肽并抵抗铁死亡的关键分子，胱氨酸转运体SLC7A11的表达与铁死亡密切相关。我们研究发现：.1. 肺癌干细胞抵抗铁死亡诱导药物Erastin的杀伤，胱氨酸转运体SLC7A11在肿瘤干细胞中表达上调；.2. 筛选并验证干性转录因子SOX2可直接结合到SLC7A11的启动子区激活其表达；.3. SOX2可通过上调SLC7A11增强胱氨酸摄取和谷胱甘肽合成，保护肺癌细胞抵抗铁死亡；.4. 胱氨酸缺乏可诱导SOX2-Cys265发生氧化修饰并抑制其活性，形成反馈调控通路；.5. 在KrasG12D/+;Lkb1lox/lox (KL)自发肺癌小鼠模型中，SOX2高表达的肿瘤更耐受铁死亡诱导药物；.6. 在肺癌病人组织样本中SLC7A11与SOX2的表达水平呈正相关。