谷胱甘肽合成限速酶GCLC调控三阴性乳腺癌细胞铁死亡的代谢性分子机理研究

Triple negative breast cancer (TNBC) is highly malignant, invasive, metastatic, with poor prognosis, and lack of effective targeted treatment strategy. Ferroptosis is a recently recognized form of programmed cell death, relied on iron-dependent lipid peroxidation, and TNBC was reported to be sensitive to ferroptosis. Our preliminary study found that distinct differences in sensitivity to ferroptosis among different subtypes of breast cancer cells: MDA-MB-231 cells (TNBC phenotype) showed a strong dependence on cystine, and cystine deprivation could induce ferroptosis and an obvious cytotoxicity; MCF-7 cells (Luminal phenotype) were not sensitive to cystine deprivation, whereas cystine supplement significantly enhanced anti-tumor effects of chemotherapeutic drugs. Additionally, cystine supplement or deprivation not only significantly affected GCLC, the rate-limiting enzyme of glutathione (GSH) synthesis, but also showed evident differences in metabolic disturbance between MDA-MB-231 cells and MCF-7 cells. It indicated that there was a closely correlation between GCLC and sensitivity to anti-tumor drugs with ferroptosis. Our studies intended to explore that whether/how GCLC regulate ferroptosis of TNBC cells on a cellular or animal level, and to provide a new strategy for clinical targeted therapy.

三阴性乳腺癌 (TNBC) 恶性度大、转移率高、预后差，临床无针对性治疗策略。近年研究发现铁依赖脂质过氧化可引起程序性细胞死亡——铁死亡，且报道显示TNBC对铁死亡敏感。初步研究发现不同分型乳腺癌细胞对铁死亡敏感性差异很大：TNBC型 MDA-MB-231细胞对胱氨酸依赖性强，剥夺胱氨酸诱发铁死亡并产生极强细胞毒作用；而Luminal 型MCF-7细胞对胱氨酸剥夺不敏感，相反，补充胱氨酸大幅提升细胞对抗肿瘤药物治疗的敏感性。另外发现胱氨酸补充或剥夺不仅显著影响限速酶GCLC、谷胱甘肽合成，还对两细胞产生明显的差异代谢扰动，提示谷胱甘肽合成及其限速酶与肿瘤细胞铁死亡及抗肿瘤药物敏感性密切相关。课题在前期研究基础上，在细胞和模型动物水平深入研究铁死亡和GCLC调控对乳腺癌细胞株细胞毒作用及代谢特征的影响，进一步探索GCLC调控铁死亡及上游信号通路相关分子机理，为临床精准、高效治疗提供新策略。

本课题着眼于GSH合成代谢在抗氧化过程中的调节功能，重点讨论了GSH合成途径蛋氨酸代谢与肿瘤细胞耐药性发展之间的关系。首先比较正常乳腺上皮细胞和不同分型乳腺癌细胞之间，以及敏感MCF-7细胞和耐药MCF-7细胞之间的蛋氨酸代谢水平差异。接着从细胞、动物水平评价胞内蛋氨酸代谢的原料、关键代谢酶对MCF-7细胞GSH合成、ROS生成、P-gp表达的调控作用。最后研究并揭示了调控蛋氨酸代谢的上游分子机制，涉及IL-6/STAT3信号通路。本课题研究成果有助于阐明肿瘤细胞与蛋氨酸代谢相关的适应性改变，更好地了解GSH调节在肿瘤细胞耐药性形成、发展中的作用，为临床基于氧化还原系统靶点逆转耐药的新治疗方法提供依据。