分泌型FEN1通过活化MUC1形成作用环路促进乳腺癌进展的分子机制及其作为诊断标志物的临床研究

Early diagnosis of breast cancer is a major clinical problem, so it is very important to find effective early diagnosis markers. Our previous studies showed that flap endonuclease 1(FEN1) secreted into the culture supernatant of breast cancer cells, activated transmembrane protein Mucin 1(MUC1), and in the extracellular promoted cell proliferation and invasion. In addition, FEN1 secretion was regulated by MUC1-mediated mTOR signal transduction pathway. At the same time, serum FEN1 level was significantly increased in breast cancer patients. Therefore, this study aims to investigate whether secreted FEN1 can form a secretory FEN1-MUC1 loop by activating MUC1, so as to promote breast cancer growth, and further study the specific molecular mechanism of this loop. Meanwhile, it is explored whether serum FEN1 can be a new diagnostic marker of breast cancer from the aspects of diagnostic performance, prognosis evaluation and efficacy evaluation. The results will clarify the role and molecular mechanism of secretory FEN1-MUC1 loop in breast cancer, and provide a theoretical basis for the development of breast cancer targeted drugs. In the meantime, serum FEN1 is expected to be an effective and specific marker for early diagnosis, real-time monitoring and prognosis evaluation of breast cancer, which has important scientific significance and potential clinical application value.

乳腺癌早期诊断是临床一大难题，因此，寻找有效的早期诊断标志物至关重要。课题组前期研究发现，核蛋白瓣状内切核酸酶1（FEN1）分泌至乳腺癌细胞培养上清中，活化跨膜蛋白黏蛋白1（MUC1），且在胞外促进细胞增殖和侵袭，而MUC1所介导的mTOR信号转导通路又可调控FEN1分泌；同时乳腺癌患者血清中FEN1水平显著升高。据此，本项目旨在探明分泌型FEN1是否通过活化MUC1，形成分泌型FEN1-MUC1环路，从而促进乳腺癌生长，并深入研究该环路的具体分子机制；同时从诊断性能、预后评估、疗效评价等方面探究血清FEN1可否成为新型乳腺癌诊断标志物。研究结果将阐明在乳腺癌中分泌型FEN1-MUC1环路的作用以及分子机制，为乳腺癌靶向药物开发提供理论依据；同时血清FEN1的检测将有望为乳腺癌的早期诊断、实时监控和预后评价提供有效而特异的标志物，具有重要的科学意义和潜在的临床应用价值。

乳腺癌早期诊断是临床一大难题，因此，寻找有效的早期诊断标志物至关重要。本项目探究FEN1作为乳腺癌肿瘤标志物的临床价值和FEN1促进乳腺癌发生发展的作用机制。经生信分析得到，FEN1在乳腺癌中高表达，且与肿瘤进展和预后相关。（1）收集51例乳腺癌患者、30例乳腺良性疾病患者和28例健康女性的外周血标本，进行ELISA检测，研究发现乳腺癌患者血清FEN1水平明显高于非癌人群（健康人群与乳腺良性疾病人群）。与传统乳腺癌标志物CA153和CEA相比，FEN1具有优良的诊断效能（AUC＞0.800），特别是在早期乳腺癌的诊断方面效能显著（AUC＞0.800）。此外，血清FEN1水平随着乳腺癌的发展而升高，且患者术后FEN1水平降低。（2）构建FEN1高/低表达稳转株，发现FEN1高表达可促进乳腺癌细胞增殖，迁移和侵袭，而敲减FEN1可抑制乳腺癌细胞增殖，迁移和侵袭；利用转录组测序发现IL-6/STAT3信号通路可能参与FEN1对乳腺癌细胞的调控，通过STAT3磷酸化的激活剂（IL-6）和抑制剂（Stattic）的作用，明确FEN1通过IL-6/STAT3信号通路促进乳腺癌细胞转移；最后通过分别构建皮下移植瘤模型和肺转移模型，验证敲低FEN1可减缓乳腺肿瘤生长和转移。综上所述，临床数据表明FEN1具有良好的鉴别诊断和预后预测优势，是一个潜在的乳腺癌肿瘤标志物，基础实验论证了FEN1通过IL-6/STAT3信号通路促进乳腺癌细胞转移。该研究为乳腺癌诊断提供新的标志物，为乳腺癌靶点治疗提供实验依据。