NCAPD3、MALAT1激活EZH2的分子机制及其在前列腺癌发生和向激素抵抗性发展中的重要性

Prostate cancer (PCa) is one of the most common malignant tumors in men and remains the second leading cause of male cancer death. The high mortality of this disease is mainly caused by castration-resistant PCa (CRPC); and the molecular mechanism is still not well-known. From the reports, activation of cancer promoting protein EZH2, which is the key component of the Polycomb repressive complex 2 (PRC2) and functions as a methyltransferase to promote histone H3 lysine 27 trimethylation (H3K27me3) and to repress tumor suppressor genes, is closely related to the development of prostate cancer. We initially found that NCAPD3, lncRNA MALAT1 and EZH2 were all high expressed and Thr350 of EZH2 was high phosphorylated in human clinical specimen; and it’s corelated to malignant degree of specimen. In PCa cells, we found that NCAPD3 could regulate the expression of MALAT1 and EZH2 genes and the phosphorylation levels of EZH2 Thr350; and MALAT1 could activate PcD function of EZH2 by binding to Thr350-phosphorylated EZH2. Furthermore, we demonstrated that the phosphorylation levels of EZH2 Thr350 were elevated in both intact and castrated PCa, while the phosphorylation level of EZH2 Ser21 (correlated to PcI function of EZH2) was only elevated in castrated PCa in PTEN knockout mice. All these results indicated that activation of PcD function of EZH2 by NCAPD3 and MALAT1 might be closely related to the occurrence and development of prostate cancer. Upon the basis of above researches, we will further define the roles and mechanisms of NCAPD3 and lncRNA MALAT1 in regulation of the gene targeting and oncogenic functions of EZH2 in PCa, and identify the requirement and importance of activation of EZH2 (both PcD and PcI functions) in PTEN deletion-induced PCa development and castration-resistant progression in both PCa cells and mice models. Our results will further strengthen the molecular basis of the etiology of prostate cancer and provide a clue in finding new molecular targets and developing new drugs for the treatment of prostate cancer.

激素抵抗性前列腺癌（CRPC）是引起男性高死亡率的恶性肿瘤之一。研究表明，促癌蛋白EZH2的活性与前列腺癌发生发展密切相关。我们发现：人前列腺癌组织样本中，NCAPD3、lncRNA MALAT1和EZH2高表达，EZH2(Thr350)高度磷酸化，且都与恶性程度相关；前列腺癌细胞中，NCAPD3能上调MALAT1和EZH2的表达及EZH2(Thr350)的磷酸化，MALAT1与Thr350磷酸化的EZH2结合进而激活EZH2；去势和未去势小鼠PTEN缺失诱发的前列腺肿瘤中，EZH2(Thr350)均高度磷酸化。说明NCAPD3和MALAT1激活EZH2与前列腺癌的发生发展密切相关。本课题将继续在细胞和小鼠体内探究NCAPD3和MALAT1激活EZH2的分子机制，揭示NCAPD3、MALAT1激活EZH2在前列腺癌发生和CRPC发展中的重要性，进一步完善前列腺癌CRPC发展的分子基础。

肿瘤是当前严重影响人类身体健康和生命安全的恶性疾病之一，其分子机制的复杂性导致临床难以治愈而致死。因此，探索完善肿瘤分子病因学并阐明肿瘤发生发展的分子机制就显得尤为重要。在该基金支持下，课题组选择临床高发的前列腺癌和结直肠癌为研究对象，并在前面基金项目研究内容的基础上，继续探究前列腺癌和结直肠癌的分子病因学。具体如下：.1、基于临床样本转录组检测结果分析，探究前列腺癌组织中表达异常基因NCAPD3、MALAT1和EZH2之间的相关性及其在前列腺癌发生发展中的重要作用，研究发现：NCAPD3通过提高STAT3和E2F1的表达水平并将它们招募到EZH2启动子区进而促进EZH2基因表达；同时，NCAPD3还通过将STAT3招募到MALAT1启动子区促进其表达，进而共同促进前列腺癌的发生、发展。此外，血液代谢组学检测结果分析表明，奇数脂肪酸与前列腺癌的发生发展有密切关系。.2、下载TCGA和GEO等数据库中有关前列腺癌组学数据（包括基因组、转录组和蛋白质组、ATAC-seq、Hi-C、ChIP-Seq等），从基因组突变与进化、染色质可及性、基因组三维结构、转录因子调控、基因表达水平和单细胞基因表达等多个维度，采用多种生信软件（包括自编小程序）进行多组学、多数据分析，对前列腺癌基因突变、插入和缺失及拷贝数变异进行了统计和肿瘤系统进化分析，发现前列腺癌中存在干细胞亚群，找到包括EZH2在内的一系列干性相关基因及其转录因子，并发现前列腺癌细胞干性与免疫微环境呈负相关性。.3、基于结直肠癌临床样本的RNA-seq结果分析，探究在结直肠癌中异常高表达的NCAPD2基因在结直肠癌发生发展中的功能及其分子机制。结果表明：NCAPD2通过Ca2+/CaMKK2/AMPK/mTORC1通路及PARP-1/SIRT1轴抑制结直肠癌细胞自噬，促进结直肠癌的发生发展，阐明NCAPD2在结直肠癌中是一个促癌因子。.4、在组学数据分析基础上，进一步探究NCAPD3在结直肠癌发生发展中的重要作用及其中的分子机制。实验结果显示：NCAPD3促进结直肠癌细胞糖代谢重编程和细胞中的Warburg效应，增强糖酵解代谢并抑制丙酮酸进入TCA循环，进而促进结直肠癌的发生和发展。.此外，还发现高糖、高脂饮食与前列腺癌和结直肠癌的发生发展密切相关，分子机制正在探究中。这些结果进一步完善了前列腺癌和结直肠癌的分子病因学。