PAK5调控Slug的转录激活在肾癌转移中的作用及机制研究

p21-activated kinases 5 (PAK5) is a serine/threonine kinase and has recently attracted considerable attention as that it is found closely related with carcinogenesis and tumor progression. Our previous study showed that miR-106a-5p could inhibit the cell migration and invasion of RCC cells via PAK5, which indicated that PAK5 could promote the renal cancer metastasis and serve as a potential therapeutic target. However, the exact regulatory mechanism is unknown. Our preliminary data showed that PAK5 could promote the expression of N-cadherin and the phosphorylation of Slug. Moreover，the tansactivation ability of Slug increased in the present of PAK5. On the basis of these findings, we propose the hypothesis that PAK5 phosphorylates Slug and promotes its tansactivation ability. The Slug can bind to the promoter of N-cadherin and activate the transcription of N-cadherin, ultimately increase the migration and invasion of renal carcinoma cells. Thus, by using renal carcinoma specimens, cultured renal carcinoma cells and mice, we intend to study the mechanism underlying the PAK5 mediated renal cancer metastasis at molecular, cellular and animal levels. Our expected results will not only elucidate the cancer metastasis mechanism and discover a new signal pathway account for of renal cancer metastasis, but also provide valuable idea for finding potential targets for molecular therapy of renal carcinoma.

PAK5是一类丝氨酸/苏氨酸蛋白激酶，近年的研究发现PAK5与肿瘤的发生发展密切相关。我们前期研究结果显示miR-106a-5p通过靶向PAK5从而抑制肾癌细胞的迁移侵袭能力，提示PAK5能促进肾癌转移并且作为肾癌转移的治疗靶点，但具体作用机制及其调控模式尚不清楚。我们的预实验结果发现PAK5可以促进N-cadherin的表达和Slug的磷酸化，并且可以激活Slug的转录激活能力，据此提出科学假说：PAK5通过磷酸化Slug，进而增强其转录激活能力，Slug进一步结合到N-cadherin启动子上激活其转录从而引起肾癌细胞EMT发生及肾癌转移。.本项目拟以肾癌标本、培养的肾癌细胞及裸鼠为研究对象，从分子、细胞与整体水平研究PAK5介导肾癌转移的机制。预期研究结果将阐明肾癌转移的机制，揭示PAK5-Slug通路是调控肾癌转移的新的信号通路；为肾癌转移的分子靶向治疗提供理论依据和治疗靶点。

PAK5是一类丝氨酸/苏氨酸蛋白激酶，近年的研究发现PAK5与肿瘤的发生发展密切相关。我们前期研究结果显示miR-106a-5p通过靶向PAK5从而抑制肾癌细胞的迁移侵袭能力，提示PAK5能促进肾癌转移并且作为肾癌转移的治疗靶点，但具体作用机制及其调控模式尚不清楚。因此在本课题中我们首先探索了PAK5是否能够在体内外具有促进肾癌细胞转移的能力。我们使用免疫组化来分析组织标本中PAK5和Slug的表达情况，之后我们使用蛋白质印迹，染色质免疫沉淀以及 Phos-tag技术研究PAK5是否可以磷酸化肾癌细胞中的Slug并促进其转录激活能力。结果表明，与邻近的正常组织相比，RCC组织中PAK5和Slug的表达均显著升高。我们结果证明PAK5可以促进Slug的磷酸化和N-cadherin的表达，并且可以激活Slug的转录激活能力。Slug进一步结合到N-cadherin启动子上激活其转录从而引起肾癌细胞EMT发生及肾癌转移。总之，PAK5介导的Slug ser87的磷酸化以及Slug转录激活N-cadherin最终促进了肾癌转移。我们的研究结果初步阐明了肾癌转移的机制，揭示了调控肾癌转移的新的信号通路；为肾癌的分子靶向治疗提供理论依据和治疗靶点。