细胞周期调节蛋白8(CDK8)促进胰腺癌对吉西他滨耐药的分子机制研究

Pancreatic cancer is one of the common malignancies in the world,and chemoresistance is an important reason for its extremely low five-year survival rate. Our previous study found that CDK8 is highly expressed in pancreatic cancer, and over-expression of CDK8 could promote pancreatic cancer cell chemoresistance to gemcitabine, the first-line chemotherapy drug. And during this process, autophagy was enhanced. Testing by Expression Profiling Chip and bioinformatics analysis, we found that over-expression of CDK8 could inhibit PIK3R5 (PI3K subunit) expression. Several studies have shown that it is a significant part of PI3K, the decreased expression of this protein may indicate PI3K / AKT / mTOR pathway was inhibited, and this signal pathway is closely related with autophagy. On the basis of summarizing our predecessors and our own previous studies, we hypothesized that CDK8 negatively regulates PIK3R5 (PI3K subunit) expression, thereby inhibiting the PI3K / AKT / mTOR pathway to promote autophagy and enhancing pancreatic cancer cell resistance to gemcitabine. In this study, we will firstly investigate how CDK8 regulates the expression of PIK3R5 (PI3K subunit). Secondly, we will explore the role of PI3K / AKT / mTOR pathway in autophagy and drug resistance of pancreatic cancer by in vitro and in vivo experiments. At last, we will study what is the role of enhanced DNA repair, maintenance of mitochondrial homeostasis, and promotion of ROS metabolism in autophagy-induced drug resistance in pancreatic cancer. This study provides a good theoretical and experimental basis for the mechanism of drug resistance and the development of new drugs in pancreatic cancer.

胰腺癌是世界上常见的恶性肿瘤之一，化疗耐药是其五年生存率极低的重要原因。我们前期研究发现胰腺癌组织中CDK8呈高表达，过表达CDK8可以促进胰腺癌细胞对吉西他滨耐药，且该过程中可以检测到自噬增强；进一步通过表达谱芯片及生物信息学分析等发现，过表达CDK8能抑制PIK3R5（PI3K亚基）表达，其表达降低表明与自噬关系密切的PI3K/AKT/mTOR通路可能受抑制。由此，我们提出：高表达CDK8可能通过负性调控PIK3R5表达，抑制PI3K/AKT/mTOR通路来增强自噬，最终促进胰腺癌细胞对吉西他滨耐药。本项目拟通过体内外实验明确：CDK8可抑制PIK3R5基因的表达，CDK8是否通过PI3K/AKT/mTOR信号通路促进自噬，以及促进自噬后导致细胞耐药的原因是否为增强DNA修复、维持线粒体稳态或促进氧自由基代谢。研究结果为胰腺癌耐药机制的阐明及寻找新的靶向治疗提供实验依据和理论基础。

胰腺癌是世界上常见的恶性肿瘤之一，化疗不敏感是其五年生存率极低的重要原因。我们前期研究发现胰腺癌组织中CDK8呈高表达，过表达CDK8可以促进胰腺癌细胞对吉西他滨不敏感。有氧糖酵解，也被称为瓦伯格效应，是癌症组织的标志。既往研究发现CDK8表达与细胞糖酵解密切相关，而微生物组成与细胞代谢物的形成密不可分。因而课题组就胰腺癌，CDK8表达，微生物组成及化疗不敏感之间的联系，展开了一系列研究。一、构建CDK8过表达细胞模型，探究CDK8过表达细胞对吉西他滨敏感性，发现CDK8过表达细胞对吉西他滨不敏感。动物实验发现CDK8过表达肿瘤体积更大。肠道微生物高通量测序发现嗜酸拟杆菌在CDK8过表达动物模型中显著降低。二、构建皮下移植瘤模型，补充嗜酸拟杆菌，探究嗜酸拟杆菌对吉西他滨治疗胰腺癌的辅助作用，发现嗜酸拟杆菌显著促进了吉西他滨的化疗作用，并增加了胰腺癌小鼠生存期。该研究的开展对吉西他滨治 疗胰腺癌提供了新的见解，为临床用药起到指导作用，奠定基础研究的基石。