转录因子HOXB9通过调控miR-203促进原发性肝癌侵袭和转移的机制研究

Our previous study have shown that transcription factor HOXB9 could promote the invasion and metastasis of primary hepatocellular carcinoma（PHC）（Cancer Research 2014）. However, its downstream effectors is not clear. The studies have showed that miR-203 was downregulated in PHC tissues and was associated with the occurrence and development of tumor.Our previous CHIP-Seq results showed that HOXB9 could bind to the miR-203 upstream. The expression of HOXB9 was negatively correlated with miR-203 expression in HCC tissues.We further found that knockdown of HOXB9 could increase the miR-203 expression level and inhibit the migration and invasion of HCC cells. Therefore, we speculated that HOXB9 affects the invasion and metastasis of HCC by regulating the miR-203 expression. To test this hypothesis, we will firstly observe the effect of HOXB9 regulating miR-203 on HCC invasion and metastasis both in vitro and in vivo. Secondly, we will further clarify the mechanism through which HOXB9 regulates miR-203 by CHIP-on-CHIP and CHIP-qPCR. Finally, we will explore the collection and clinical significance of HOXB9 and miR-203 expression in HCC tissues. This study will provide the new theoretical basis for clarifying the mechanism of HCC invasion and metastasis.

我们前期发现转录因子HOXB9可促进原发性肝癌侵袭和转移（Cancer Research, 2014），但其下游效应分子尚不清楚。研究报道miR-203在肝癌中低表达且与肝癌发生发展相关。预实验应用CHIP-Seq等技术发现HOXB9可以结合miR-203上游区域；HOXB9与miR-203在肝癌组织中表达呈负相关；降低肝癌细胞MHCC97H中HOXB9表达可导致miR-203表达升高及侵袭和迁移能力下降。因此，我们推测HOXB9可能通过调节miR-203表达从而影响肝癌侵袭和转移。为验证这一假说，本研究拟先通过体外和体内实验明确HOXB9通过miR-203影响肝癌侵袭转移；然后应用CHIP-on-CHIP及CHIP-qPCR等技术进一步确定HOXB9调控miR-203机制；最后分析HOXB9和miR-203在肝癌组织中的表达及其临床意义；本研究将为阐明肝癌发生侵袭和转移机制提供理论依据。

miR-203可作为致癌基因亦可作为抑癌基因，然而它在原发性肝癌中的作用及调控机制并不清楚。在本研究中，我们发现miR-203在肝癌组织及细胞株中低表达，miR-203低表达的肝癌患者预后更差。过表达miR-203抑制肝癌细胞的侵袭转移。进一步，我们证实miR-203是转录因子HOXB9的下游靶基因，HOXB9通过调控miR-203的表达影响肝癌细胞侵袭和转移能力。机制方面，CHIP及荧光素酶报告基因实验结果提示HOXB9抑制miR-203的转录。HOXB9通过招募组蛋白甲基转移酶EZH2，导致miR-203的启动子区域组蛋白H3第27位赖氨酸三甲基化(H3K27me3)增加，进而抑制miR-203的转录和表达。最后，我们分析了肝癌组织中HOXB9与miR-203表达的相关性及其临床意义，结果表明HOXB9与miR-203的表达呈负相关，HOXB9高表达miR-203低表达提示肝癌患者预后最差。我们的研究揭示了一种对非编码RNA新的调控机制，将为防治肝癌发生侵袭和转移提供新的治疗靶点。