PI3K/Nrf2信号通路协同调控乳腺癌EMT及侵袭转移的分子机制

Invasion and metastasis is the leading cause of death of most patients with breast cancer, which can be induced by Epithelial-Mesenchymal Transition (EMT) in its early stage. Recent studies demonstrated that, as two important signaling pathways, PI3K/Akt pathway and Nrf2/ARE pathway dysregulated in many cancers, including breast cancer. However, what role two pathways cross-talk plays in metastasis of breast cancer is poorly understood. In our previous studies, we found that NQO1, one of downstream gene of Nrf2 pathway, was overexpressed in breast cancer which was closely related with prognosis of patients. We also found that PI3K/mTOR inhibitor BEZ235 could reduce NQO1 protein expression and inverse EMT progress in breast cancer cell line MCF-7. Taken together, we plan to further investigate the effect of dual inhibition of the PI3K/Akt pathway and Nrf2/ARE/NQO1 pathway in breast cancer in vitro and in vivo, explore the mechanism of two pathways co-regulation on tumor EMT and metastasis. These will not only extend the theoretical basis of EMT regulation in breast cancer, but also provide new intervention targets for cancer treatment.

侵袭转移是导致乳腺癌预后不良的主要原因，EMT则是诱发肿瘤浸润和转移的早期重要事件。目前研究表明，PI3K/Akt和Nrf2/ARE通路与多种肿瘤的发生、转移和治疗密切相关，但两条通路协同调控肿瘤EMT及侵袭性的相关机制尚不清楚。项目组前期工作发现，Nrf2通路下游重要因子NQO1蛋白在乳腺癌患者肿瘤组织中的异常高表达与患者预后密切相关；PI3K信号通路特异性抑制剂BEZ235与NQO1特异性抑制剂Dicoumarol联合用药可协同抑制MCF-7乳腺癌细胞增殖，并对EGF诱导的细胞EMT改变具有抑制作用。因此，本项目拟通过细胞实验和裸鼠模型建立，在体内外检测PI3K/Akt通路与Nrf2/ARE/NQO1通路联合抑制对乳腺癌EMT及侵袭性的影响，分析PI3K/Nrf2通路协同调控乳腺癌EMT及侵袭的作用机制，为乳腺癌EMT发生提供新的分子解释，并为乳腺癌转移控制提供新靶点及靶向药物选择。

侵袭转移是导致乳腺癌预后不良的主要原因，EMT则是诱发肿瘤浸润和转移的早期重要事件，受到多条信号通路调控，但通路间协同调控肿瘤EMT及侵袭性的相关机制尚需进一步明确。既往研究表明PI3K/Akt和Nrf2/ARE/NQO1通路与多种肿瘤的发生、转移和治疗密切相关，因此，本项目重在阐明PI3K/Akt和Nrf2/NQO1通路协同调控乳腺癌EMT及侵袭的分子作用机制。.研究主要应用免疫组化、基因芯片、PCR及western blot等分子生物技术，通过体外细胞实验、体内动物模型较深入的探讨了PI3K/Akt和Nrf2/ARE/NQO1通路相互作用并协同调控乳腺癌EMT的进程。项目组还围绕上皮间质化参与乳腺癌细胞增殖侵袭的可能调控机制做了扩展研究，对PI3K/Akt通路与组蛋白去乙酰化酶协同调控乳腺癌增殖及转移进行了机制探讨，得到了有意义的结果。简要总结如下：（1）联合用药分析结果显示，PI3K通路抑制剂（BEZ235）和Nrf2/ARE/NQO1通路抑制（β-拉帕醌）联合用药能够协同抑制乳腺癌细胞增殖能力，构建乳腺癌裸鼠移植瘤模型后的体内联合用药实验结果与体外细胞实验结果相一致；BEZ235与β-拉帕醌两药联用可协同抑制乳腺癌横向及纵向迁移能力；基因芯片检测结果表明联合用药可明显改变乳腺癌细胞生存及死亡信号通路相关mRNA表达情况；进一步的机制研究显示联合用药可通过抑制EMT、血管生成协同调控乳腺癌细胞的侵袭转移能力。（2）PI3K通路抑制剂BEZ235和组蛋白去乙酰化酶抑制剂TSA联合用药体内外均可协同抑制乳腺癌的增殖，进一步的机制研究结果显示诱导依赖caspase途径的细胞凋亡和促进细胞自噬是BEZ235与TSA协同抑制乳腺癌增殖的可能分子机制。本研究提示，PI3K/Akt通路、Nrf2/NQO1通路及组蛋白去乙酰化修饰相互作用共同参与调控乳腺癌EMT过程，进而促进肿瘤的侵袭转移。本项目为乳腺癌EMT发生提供新的分子解释，并为乳腺癌转移控制提供新靶点及靶向药物选择。