YAP/TAZ蛋白去泛素化机制及其靶分子AREG作为胰腺癌早期诊断标志物的研究

YAP/TAZ proteins is the key effectors in Hippo signaling pathway, amphiregulin (AREG) is the downstream functional target of YAP/TAZ and highly expressed in serum of pancreatic cancer patients. The stability of YAP/TAZ proteins are mainly regulated by ubiquitination and deubiquitination, but deubiquitination mechanism is still unclear. Our previous studies found that ubiquitin specific protease 39 (USP39) expression was up-regulated in pancreatic cancer, and positively correlated with YAP/TAZ expression; Moreover, it could promote pancreatic cancer cell proliferation, cell cycle arrest, inhibition of apoptosis by sitimulating the MAPK/ERK pathway; Previous studies also showed that YAP could activate the MAPK pathway, and silencing ERK expression could accelerate the degradation of YAP. Therefore, we hypothesize that whether USP39 increase stability and expression of YAP/TAZ by promoting ubiquitination of YAP/TAZ, thereby over-activate Hippo and MAPK/ERK pathway, and finally, promote the development of pancreatic cancer? This study will confirm USP39 is ubiquitination enzymes of YAP/TAZ and their underlying mechanism by performing a variety of molecular biology methods; and explore the possibilities of serum AREG，the YAP / TAZ downstrea functional target, as an early noninvasive diagnostic marker of pancreatic cancer. Moreover, our study will clarify the molecular mechanisms in pancreatic cancer development, and shed new light on early diagnostic markers in pancreatic cancer.

YAP/TAZ蛋白为Hippo信号通路的主要效应分子，人类双调蛋白（AREG）为其靶分子,在胰腺癌血清中高表达。YAP/TAZ蛋白的稳定性主要受泛素及去泛素化调节，但去泛素化机制尚不清楚。我们发现泛素特异性蛋白酶39（USP39）在胰腺癌中高表达，促进胰腺癌细胞增殖，阻滞细胞周期，抑制细胞凋亡，并上调ERK磷酸化水平；USP39沉默后YAP/TAZ表达水平下调；既往研究表明YAP能激活MAPK/ERK通路，且沉默ERK可加速YAP的降解。我们推测USP39是否通过去泛素化YAP/TAZ，导致YAP/TAZ稳定性增加，继而引起Hippo及MAPK/ERK通路的过度活化，最终导致胰腺癌的发生发展?本研究将通过多种分子生物学方法证实USP39是YAP/TAZ去泛素化的酶及其作用机制；探索AREG作为胰腺癌早期诊断的血清标志物可能性。为明确胰腺癌发生发展的分子机制、寻找早期诊断标志物开拓新思路。

胰腺癌是常见的消化系统肿瘤，严重威胁着人们的健康和生命。探索胰腺癌的发病机制，对改善治疗效果和患者预后具有十分重要的意义。本项目重点探究了USP39、YAP/TAZ蛋白在胰腺癌发生发展中的作用及机制。首先，通过体外、体内实验，分别证实了USP39及Hippo信号通路主要效应分子YAP/TAZ促进胰腺癌生长的作用，并探讨了胰腺癌组织中USP39的表达情况及USP39抑制胰腺癌细胞生长的机制。进而，利用荧光素酶报告系统筛选出有效抑制YAP/TAZ活性的激酶抑制剂，证实了抑制NTRK1对胰腺癌细胞PANC1和乳腺癌细胞MDA-MB231的影响及对YAP/TAZ活性的影响，明确了NGF-NTRK1通过Hippo信号通路调控YAP/TAZ活性的分子机制。最后，基于体外、体内实验证实了敲低NTRK1会抑制胰腺癌细胞PANC1和乳腺癌细胞MDA-MB231及小鼠移植瘤的生长。综上所述，本项目对YAP/TAZ蛋白在胰腺癌发生发展中作用机制的探究具有重要前景意义，有望为开发胰腺癌的新型治疗靶点、改善治疗效果和患者预后提供坚实理论基础。