MTHFD2调节ZEB1mRNA稳定性促进去势抵抗性前列腺癌转移的功能及机制研究

Metastasis is the leading cause of castration-resistant prostate cancer (CRPC) related death. However, the underlying mechanism is still obscured. We previously confirmed that ZEB1 was involved in prostate cancer metastasis. Furthermore, we found: 1. expression level of MTHFD2 was most obviously up-regulated in CRPC metastasis than that in the primary lesion (RNA-seq data). 2. MTHFD2 knockdown significantly impaired the migration and invasion ability of PC3 cells. 3. After MTHFD2 knockdown, ZEB1 mRNA half-life was shortened, protein level was down-regulated, and AUF1 mRNA level was down-regulated. 4. RPISeq prediction tool showed that AUF1 protein had potential binding ability with ZEB1 3'UTR (non-untranslated region). Therefore, we hypothesized that MTHFD2 could up-regulate the expression of AUF1, and then combination of AUF1 and ZEB1 3'UTR inhibited degradation of ZEB1 mRNA and up-regulated ZEB1 expression, thus promoting CRPC metastasis.This project intends to clarify the molecular mechanism of MTHFD2 mediated CRPC metastasis in vitro and vivo. Finally, providing a theoretical basis for treatment strategy of metastatic CRPC.

转移是去势抵抗性前列腺癌（CRPC）致死的主要原因，发生机制至今不明。我们前期证实ZEB1参与前列腺癌转移，进一步发现：1、MTHFD2在CRPC转移灶中表达明显高于原发灶，上调最为显著（测序）。2、前列腺癌细胞系PC3敲减MTHFD2后，迁移、侵袭能力被显著削弱。3、敲减MTHFD2导致ZEB1mRNA半衰期缩短、蛋白水平下降，同时RNA结合蛋白AUF1转录水平下调。4、RPISeq预测工具显示：AUF1蛋白与ZEB1的3’非翻译区具有潜在的结合能力。因此，我们提出假设：MTHFD2可上调AUF1表达，进而AUF1与ZEB1的3’非翻译区结合抑制ZEB1mRNA降解、促进蛋白合成，最终促使CRPC发生转移。本项目拟在体外阐明MTHFD2调控ZEB1mRNA稳定性促进CRPC转移的分子机制，最后通过体内实验探讨MTHFD2治疗靶标的可行性，为转移性CRPC治疗新策略奠定基础。

肿瘤转移是晚期前列腺癌治疗最为棘手问题，目前缺少关键的有效诊治靶点。亚甲基四氢叶酸脱氢酶2（MTHFD2）是人体内一碳代谢的关键酶，调控体内叶酸的合成代谢。在本研究中，我们发现MTHFD2在前列腺癌细胞中表达上调，高表达的MTHFD2与前列腺癌增殖、转移密切相关。敲低MTHFD2可显著抑制前列腺癌细胞体外增殖、迁移、侵袭能力。机制上我们发现MTHFD2受UHMK1调控，UHMK1可靶向结合NCOA3蛋白促进其在ser857位点磷酸化激活，进而促进ATF4发生核转位，从而促进MTHFD2的表达，进而促进前列腺癌细胞增殖和转移。最后MTHFD2又可上调UHMK1的表达，形成UHMK1/MTHFD2正反馈信号环路。本项目研究揭示UHMK1/MTHFD2正反馈信号环路促进前列腺癌转移、进展的发病机制，有望为前列腺癌的新的治疗思路提供实验依据。