缺氧环境中lncRNA H19作为ceRNA上调EZH2促进乳腺癌侵袭转移的研究

Hypoxia plays an important role in driving breast cancer metastasis; however, the underlying mechanism remains unclear. Our previous study found that high level of polycomb protein enhancer of zeste homolog 2 (EZH2) was closely associated with tissue hypoxia and metastasis in breast cancer (Oncol Rep, 2014). In addition, hypoxia might upregulate EZH2 expression at post-transcriptional level. Our further study showed that hypoxia significantly induced long noncoding RNA (lncRNA) H19 expression in breast cancer cells, and overexpression of H19 increased EZH2 expression. LncRNAs, acting as competitive endogenous RNAs (ceRNAs), can regulate gene expression at post-transcription level by competitively binding to miRNAs and lowering their bind capacity to target mRNA, leading to increased translations of the mRNA. Moreover, our bioinformatics analysis suggested that both H19 and the 3’ untranslated region (UTR) of EZH2 mRNA harbored the identical miRNAs binding sites. We thus propose that hypoxia induced H19 may function as ceRNA in upregulating EZH2 expression, and EZH2 further promote breast cancer metastasis. This project intends to explore the mechanism of hypoxia induced H19 upregulating EZH2 expression by luciferase reporter gene assay and RNA-binding protein immunoprecipitation (RIP), and validate it in breast cancer tissues with follow-up data. The aims of this project are to reveal a new molecular mechanism of hypoxia promoting breast cancer metastasis, and to provide a scientific evidence for the future targeted therapy in breast cancer.

缺氧可促进乳腺癌侵袭转移，其分子机制尚不清楚。申请人前期研究发现乳腺癌中EZH2高表达与组织缺氧及肿瘤转移密切相关（Oncol Rep, 2014），且缺氧可在转录后水平上调EZH2表达。进一步的研究证实：缺氧可上调乳腺癌细胞中的lncRNA H19 (H19)，而后者可上调EZH2表达。作为竞争性内源RNA (ceRNA)抑制miRNA与靶mRNA结合而上调其蛋白表达是lncRNA在转录后水平调控基因表达的重要机制。申请人基于生物信息学的分析发现H19和EZH2 mRNA 3'UTR含有相同miRNA的结合位点。因此，本项目提出：缺氧时上调的H19可作为ceRNA间接上调EZH2表达，进而促进乳腺癌侵袭转移。本项目拟采用荧光素酶报告基因、RIP等方法，探讨缺氧时H19上调EZH2的机制，并结合临床预后资料进行验证，旨在阐明缺氧促进乳腺癌侵袭转移的新机制，为基于此的靶向治疗提供理论依据。

缺氧可促进乳腺癌侵袭转移，其分子机制尚不清楚。前期研究发现乳腺癌中EZH2与组织缺氧及乳腺癌转移密切相关，且缺氧可在转录后水平上调EZH2表达。本课题发现缺氧可引起长链非编码RNA H19 （H19）表达明显上调，而H19可上调EZH2的表达，进一步研究发现H19可通过ceRNA机制与EZH2竞争性结合miRNA let-7而间接上调EZH2的表达，从而促进肿瘤侵袭转移。这些结果阐明了缺氧微环境促进肿瘤侵袭转移的新机制，也为基于在本课题中发现的在乳腺癌转移中起关键作用的长链非编码RNA和miRNA的抗肿瘤新药的研发提供了理论依据。. 此外，在本基金资助下，我们还对肿瘤的预后因素方面进行了研究，主要有以下发现：一，改良的CLIP评分（ALBI-CLIP）可代替CLIP评分用于预测接受TACE治疗的肝癌患者的预后，比CLIP评分更为简便、客观；二，治疗前血浆纤维蛋白原水平高是肺癌预后差的独立预后因素，为肺癌患者提供了一个可靠的预后标志物；三，ebv-miR-BART10-3p（BART10-3p）和ebv-miR-BART22（BART22）高表达的EBV相关胃癌预后较差，其通过激活Wnt通路促进肿瘤转移。