TEAD4 的新靶标 RBM8A 通过调节 IGF1R 和 IRS-2 促进乳腺癌进展。

BACKGROUND: Breast cancer (BC) is the most common malignant tumor in women worldwide, and further elucidation of the molecular mechanisms involved in BC pathogenesis is essential to improve the prognosis of BC patients. RNA Binding Motif Protein 8 A (RBM8A), with high affinity to a myriad of RNA transcripts, has been shown to play a crucial role in genesis and progression of multiple cancers. We attempted to explore its functional significance and molecular mechanisms in BC. METHODS: Bioinformatics analysis was performed on publicly available BC datasets. qRT-PCR was used to determine the expression of RBM8A in BC tissues. MTT assay, clone formation assay and flow cytometry were employed to examine BC cell proliferation and apoptosis in vitro. RNA immunoprecipitation (RIP) and RIP-seq were used to investigate the binding of RBM8A/EIF4A3 to the mRNA of IGF1R/IRS-2. RBM8A and EIF4A3 interactions were determined by co-immunoprecipitation (Co-IP) and immunofluorescence. Chromatin immunoprecipitation (Ch-IP) and dual-luciferase reporter assay were carried out to investigate the transcriptional regulation of RBM8A by TEAD4. Xenograft model was used to explore the effects of RBM8A and TEAD4 on BC cell growth in vivo. RESULTS: In this study, we showed that RBM8A is abnormally highly expressed in BC and knockdown of RBM8A inhibits BC cell proliferation and induces apoptosis in vitro. EIF4A3, which phenocopy RBM8A in BC, forms a complex with RBM8A in BC. Moreover, EIF4A3 and RBM8A complex regulate the expression of IGF1R and IRS-2 to activate the PI3K/AKT signaling pathway, thereby promoting BC progression. In addition, we identified TEAD4 as a transcriptional activator of RBM8A by Ch-IP, dual luciferase reporter gene and a series of functional rescue assays. Furthermore, we demonstrated the in vivo pro-carcinogenic effects of TEAD4 and RBM8A by xenograft tumor experiments in nude mice. CONCLUSION: Collectively, these findings suggest that TEAD4 novel transcriptional target RBM8A interacts with EIF4A3 to increase IGF1R and IRS-2 expression and activate PI3K/AKT signaling pathway, thereby further promoting the malignant phenotype of BC cells.

背景：乳腺癌（BC）是全球女性最常见的恶性肿瘤，进一步阐明 BC 发病机制中的分子机制对于改善 BC 患者的预后至关重要。RNA 结合基序蛋白 8A（RBM8A）与大量 RNA 转录本具有高亲和力，已被证明在多种癌症的发生和进展中发挥关键作用。我们试图探讨其在 BC 中的功能意义和分子机制。

方法：对公开的 BC 数据集进行生物信息学分析。qRT-PCR 用于检测 BC 组织中 RBM8A 的表达。MTT 测定、克隆形成测定和流式细胞术用于体外检测 BC 细胞增殖和凋亡。RNA 免疫沉淀（RIP）和 RIP-seq 用于研究 RBM8A/EIF4A3 与 IGF1R/IRS-2 mRNA 的结合。通过共免疫沉淀（Co-IP）和免疫荧光检测 RBM8A 和 EIF4A3 的相互作用。染色质免疫沉淀（Ch-IP）和双荧光素酶报告基因检测用于研究 TEAD4 对 RBM8A 的转录调控。通过异种移植模型研究 RBM8A 和 TEAD4 对体内 BC 细胞生长的影响。

结果：在这项研究中，我们表明 RBM8A 在 BC 中异常高表达，并且敲低 RBM8A 可抑制 BC 细胞的增殖并诱导体外凋亡。EIF4A3 在 BC 中与 RBM8A 具有相似表型，可与 RBM8A 在 BC 中形成复合物。此外，EIF4A3 和 RBM8A 复合物调节 IGF1R 和 IRS-2 的表达，激活 PI3K/AKT 信号通路，从而促进 BC 的进展。此外，我们通过 Ch-IP、双荧光素酶报告基因和一系列功能挽救实验鉴定了 TEAD4 是 RBM8A 的转录激活子。此外，我们通过裸鼠异种移植肿瘤实验证明了 TEAD4 和 RBM8A 在体内的致癌作用。

结论：总之，这些发现表明，TEAD4 的新转录靶标 RBM8A 与 EIF4A3 相互作用，增加 IGF1R 和 IRS-2 的表达并激活 PI3K/AKT 信号通路，从而进一步促进 BC 细胞的恶性表型。