多功能Tudor-SN蛋白泛素化在肝细胞癌化疗敏感性中的作用机制

Reduction of hepatocellular carcinoma (HCC) chemosensitivity is a major cause of chemotherapy failure, which turns out to be a tough problem in clinical treatment of hepatocarcinoma. Stress Granules (SGs) are a type of cellular anti-apoptotic foci structure, which aggregate in response to environmental stress stimuli and are associated with the reduction of chemosensitivity. Previously, we found that Tudor-SN protein is ubiquitinated and modulates the SGs assembly, and knockdown of Tudor-SN enhances the sensitivity of HCC cells to chemotherapy drugs. Based on the above, this program aims at further investigating the role of stress protein Tudor-SN ubiquitination in the HCC chemosensitivity. We speculate that: After the stimulation of chemotherapy drugs, the K388, K389, K758 sites of Tudor-SN protein are ubiquitinated by E3 ubiquitin-protein ligase UHRF1; Then ubiquitinated Tudor-SN regulates the chemosensitivity via the SGs dependent or independent ways. Based on "drug-resistant HCC cell model" and "drug-resistant HCC in situ model", the crispr, FPLC, co-IP, MTS, Q-PCR, and other technologies will be used to verify our hypothesis, providing the theoretical basis for the reversal of HCC chemoresistance.

肝细胞癌（HCC）对化疗药物敏感性的降低是导致化疗失败的主要原因，为临床肝癌治疗的一大难题。应激颗粒（SGs）是细胞在受到外界刺激时形成的具有抗凋亡作用的颗粒结构，与化疗药物敏感性的降低相关。本课题组前期发现Tudor-SN蛋白可发生泛素化修饰，参与并调控SGs形成；沉默HCC细胞中的Tudor-SN能够增强其对化疗药物的敏感性。基于此，本项目旨在深入探讨应激颗粒蛋白Tudor-SN的泛素化在HCC化疗敏感性中的作用机制。推测：当HCC细胞受到化疗药物刺激时，E3酶UHRF1介导Tudor-SN蛋白K388、K389、K758位点发生泛素化修饰；泛素化的Tudor-SN通过SGs依赖或非依赖性途径降低对化疗药物的敏感性。本项目拟以“HCC细胞耐药模型”和“原位肝癌化疗耐药模型”为基础，利用crispr、FPLC、co-IP、MTS、Q-PCR等技术验证假设，为逆转肝癌治疗耐药提供理论依据。

肝癌耐药的发生机制复杂，从接受化疗药物刺激信号到肿瘤细胞内发生一系列信号通路传导，上调一些促进存活的基因和促进药物泵出的基因表达，产生对化疗药物的耐受。在这一过程中，肿瘤细胞在化疗药物刺激下的抗凋亡机制发挥着重要作用。Tudor-SN蛋白，又称为SND1蛋白，是一个进化上高度保守的多功能蛋白质，可作为转录共激活因子、RISC复合物成员等促进肝癌的发生发展。我们通过研究发现Tudor-SN在HCC中高表达，但Tudor-SN的表达水平与患者生存率之间并无明显差异。干扰Tudor-SN或LncRNA UCA1的表达可增强HCC对化疗药物5-Fu的敏感性，增加HCC细胞的凋亡水平，而干扰Tudor-SN同时回复LncRNA UCA1的表达可抵消因干扰Tudor-SN产生的5-Fu诱导HCC凋亡水平增加。Tudor-SN通过与转录因子MYB结合，共同激活LncRNA UCA1的表达，在HCC抵抗化疗药物致凋亡的过程中发挥作用。本项目深入探究了Tudor-SN蛋白在HCC细胞抗凋亡的机制，具有抗凋亡作用的Tudor-SN蛋白具有作为改善HCC化疗抵抗的潜在药物靶向。首次发现Tudor-SN蛋白与LncRNA之间的相关性，首次发现LncRNA UCA1在HCC中具有抗凋亡的作用。目前发表该基金资助SCI论文6篇。