Zhang Jun, Chen Shuaijun, Wei Sitian, Cheng Shuangshuang, Shi Rui, Zhao Rong, Zhang Wei, Zhang Qi, Hua Teng, Feng Dilu, Yu Zhicheng, Wang Hongbo
Department of Obstetrics and Gynecology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, 430022, China.
Department of Pathology, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430014, China.
Redox Biol. 2022 Nov;57:102493. doi: 10.1016/j.redox.2022.102493. Epub 2022 Sep 26.
Endometrial cancer (EC) is one of the most common gynecological cancers. Ferroptosis is a newly identified form of cell death characterized by iron-dependent lipid peroxide accumulation. Circular RNAs (circRNAs) have emerged as critical regulators for cancer development. However, circRNA-mediated modulation of ferroptosis in EC is yet to be clarified. In this study, we found that circRAPGEF5 expression was elevated in EC tissues compared to the normal endometrial tissues. In vitro and in vivo functional analysis demonstrated that circRAPGEF5 facilitates rapid proliferation of EC cells. RNA binding protein fox-1 homolog 2 (RBFOX2), a splicing regulator, was identified as the protein interacts with circRAPGEF5. Further studies revealed that circRAPGEF5 can bind to the Fox-1 C-terminal domain of RBFOX2 and induces specific exon exclusion of TFRC through obstructing the binding of RBFOX2 to pre-mRNA. As a result, elevated levels of circRAPGEF5 lead to ferroptosis resistance via the decreased labile iron pool and attenuated lipid peroxide production in EC cells. Additionally, a series of gain- and loss-of-function experiments demonstrated that knocking down or overexpressing RBFOX2 reversed the effects of knocking down or overexpressing circRAPGEF5 in EC cells. Finally, it is revealed that circRAPGEF5 promote the formation of TFRC with exon-4 skipping and confer ferroptosis resistance in EC cells through the interaction with RBFOX2. Collectively, these findings provide new insight into the molecular mechanism in which circRNAs mediate mediates ferroptosis via modulating alternative splicing, and circRAPGEF5/RBFOX2 splicing axis could be a promising therapeutic target for treating EC.
子宫内膜癌（EC）是最常见的妇科癌症之一。铁死亡是一种新发现的细胞死亡形式，其特征是铁依赖性脂质过氧化物积累。环状RNA（circRNA）已成为癌症发展的关键调节因子。然而，circRNA介导的EC中铁死亡的调节作用尚待阐明。在本研究中，我们发现与正常子宫内膜组织相比，circRAPGEF5在EC组织中的表达升高。体外和体内功能分析表明，circRAPGEF5促进EC细胞的快速增殖。RNA结合蛋白fox-1同源物2（RBFOX2），一种剪接调节因子，被鉴定为与circRAPGEF5相互作用的蛋白质。进一步研究表明，circRAPGEF5可以与RBFOX2的Fox-1 C末端结构域结合，并通过阻碍RBFOX2与前体mRNA的结合诱导TFRC的特定外显子排除。结果，circRAPGEF5水平升高导致EC细胞中不稳定铁池减少和脂质过氧化物产生减弱，从而产生铁死亡抗性。此外，一系列功能获得和丧失实验表明，敲低或过表达RBFOX2可逆转敲低或过表达circRAPGEF5对EC细胞的影响。最后，研究表明circRAPGEF5通过与RBFOX2相互作用促进外显子4跳跃的TFRC形成，并赋予EC细胞铁死亡抗性。总的来说，这些发现为circRNA通过调节可变剪接介导铁死亡的分子机制提供了新的见解，并且circRAPGEF5/RBFOX2剪接轴可能是治疗EC的一个有前景的治疗靶点。
