PAK5磷酸化DDX17对Her2阳性乳腺癌侵袭转移的影响及机制研究

Human epidermal growth factor receptor type II (HER2) positive breast cancer represents a clinical challenge for current therapy. The mechanism of Her2 positive breast cancer is still unclear. Her2 has been associated with poor prognosis. Our previous study found that PAK5 could promote expression of breast cancer marker Her2 and was associated with Her2 expression. The DEAD (Asp-Glu-Ala-Asp) box helicase 17-DDX17 was identified a novel PAK5-interacting protein by Protein mass spectrometry technology. It was comfirmed that DDX17 inhibited Her2 expression, while PAK5 phosphorylated DDX17..In this project, we aim to confirm the interaction of PAK5 with DDX17 and find new phosphorylation site in DDX17 and to explore the mechanism for PAK5 modulating DDX17 expression. We plan to investigate the effects of DDX17 on invasion and metastasis of breast cancer and elucidate the new mechanisms for DDX17 regulating Her2 expression. We want to know the correlation between the PAK5-DDX17 interaction and clinical molecular subtype, patients survival and prognosis. This project will make us understanding of mechanistic role of PAK5-mediated DDX17 phosphorylation in metastasis, providing a new molecular marker and therapeutic target for breast cancer treatment.

Her2阳性乳腺癌是最凶恶的乳腺癌。Her2阳性意味着肿瘤细胞恶性程度高、疾病进展快、易转移和复发、且预后不佳。但它的机制尚未清晰阐明。本项目前期工作发现，PAK5能促进 Her2表达，临床数据表明PAK5与Her2表达呈正相关。采用蛋白质谱分析技术，筛选出PAK5新的互作蛋白-DDX17。已初步证实DDX17能抑制Her2蛋白表达，同时，PAK5能磷酸化DDX17。本课题旨在进一步证实PAK5与DDX17的相互作用并发现新的磷酸化位点；阐述DDX17调节乳腺癌转移及复发标记物-Her2蛋白的机制；明确PAK5与DDX17相互作用与临床乳腺癌分子分型、病人生存和预后的关系。通过上述研究，我们将明确信号分子PAK5介导DDX17磷酸化在乳腺癌侵袭转移及预后分析中的作用及机制，为临床治疗提供重要的理论基础。

乳腺癌是严重危害女性健康的致死性疾病，Her2阳性乳腺癌作为最凶恶的乳腺癌亚型，易复发，预后差。Her2蛋白出现在癌细胞表面，促进癌细胞分裂生长和侵袭转移，因此，研究Her2蛋白网络通路调控，将为乳腺癌的临床治疗提供重要的理论依据。.PAK5是丝氨酸/苏氨酸激酶，在乳腺癌组织中高表达，但PAK5与乳腺癌临床分子分型的关系尚无报道。本课题中我们发现PAK5在乳腺癌组织中高表达，且与Her2阳性呈显著相关性，PAK5促进Her2的表达。采用蛋白质谱分析技术，在乳腺癌细胞中筛选PAK5新的互作蛋白-DDX17。证实PAK5能磷酸化DDX17 S522位点，并证实DDX17能抑制Her2蛋白表达，且这种抑制作用依赖于PAK5的磷酸化。此外，我们发现PAK5也能磷酸化DDX17的同家族成员-DDX5。研究发现PAK5能磷酸化DDX5 T69位点，并促进DDX5的类泛素化和DDX5与Drosha/DGCR8的结合，进而促进肿瘤相关miRNA-10b和miRNA-199a的成熟，加速乳腺癌的进程。通过对本课题的深入研究我们得出结论：1、PAK5能促进Her2表达，临床数据表明PAK5与Her2表达呈正相关；2、PAK5与DDX17相互作用并磷酸化其丝氨酸522位点；3、DDX17能抑制Her2蛋白表达，且依赖于PAK5的磷酸化；4、PAK5与DDX5相互作用并磷酸化其苏氨酸69位点；5、PAK5对DDX5的磷酸化能促进DDX5的类泛素化，并上调DDX5蛋白水平；6、PAK5对DDX5的磷酸化能促进DDX5与Drosha/DGCR8复合物的结合，进而促进肿瘤相关miRNA-10b和miRNA-199a的成熟；7、确定了PAK5与DDX5临床表达的相关性，二者高表达与患者预后差相关。综上所述，PAK5可能是参与乳腺癌进展的关键因子，有望成为临床乳腺癌诊断治疗及预后分析的可能靶点。