肥胖相关基因FTO通过下调肝癌细胞RNA m-6-a抑制肝癌侵袭转移的机制研究

Hepatocellular carcinoma (HCC) is one of most common malignancy worldwide. The prognosis is extremely poor due to low diagnostic rate at early stage and recurrence or metastasis after clinical intervention. Our team found loss of 5hmC in HCC indicates poor prognosis. The down-regulation of TET family enzymes is likely one of the mechanisms underlying 5-hmC loss in HCC. The obesity-related gene (FTO) resembles the TET enzyme, erases RNA from N6-methyladenosine (m-6-A), reversing RNA hypermethylation. It has been reported that dysregulation of FTO is tightly associated with various human malignancies. Interestingly, our results firstly revealed that the expressions of FTO decreased in several HCC cancer cell lines and tissues. The overexpression of m-6-A is an epigenetic hallmark of HCC. Clinical studies revealed that the m-6-A expression was significantly associated with patients’ poor prognosis. Moreover, experimental data showed that FTO was able to significantly inhibit proliferation, migration and invasion of HCC cells in vitro. Meanwhile, our data revealed that FTO prevent the growth and lung metastasis of HCC cells in vivo. Further, RNA-seq revealed that the FTO changed a great deal of genes in HCC cells, involved in the regulation of inflammatory response, lipid metabolism, P53 and so on. Here we plan to determine the major pathways and target genes regulated by FTO using bioinformatics tools such as IPA and validate these genes and pathways antibody array assay. Thus, the aim of this project is to investigate FTO biological functions in the proliferation and metastases of HCC and uncover the underlying mechanisms, thereby expanding the current understanding of FTO and m-6-A in the field of HCC research and providing new targets for molecular intervention for HCC patients.

肝癌是最常见的恶性肿瘤之一，早期诊断率低，术后易复发转移，预后极差。我们课题组发现TET酶异常导致5hmC缺失参与肝癌进展。肥胖相关基因 (FTO)类似TET酶，擦去RNA的N6-甲基腺苷（m-6-A），逆转RNA的高甲基化。研究发现FTO异常表达与人类多种恶性肿瘤有着紧密的联系。我们发现FTO在多个肝癌细胞系及组织中均呈低表达，肝癌组织芯片中m-6-A呈高表达，m-6-A高表达的肝癌患者预后不佳。进一步实验表明FTO显著抑制肝癌细胞生长增殖和迁移侵袭。裸鼠实验证实FTO抑制肝癌细胞生长和肺转移。转录组测序发现过表达FTO改变肝癌细胞多个基因，参与调控炎症反应、脂质代谢、P53等。因此，本项目拟利用生物数据库及蛋白芯片对初步确定的靶基因进行验证和补充。研究FTO对肝癌细胞生长增殖和侵袭转移的作用及分子机制，拓展对FTO和m-6-A 在肝癌领域的认识，并为肝癌的靶向治疗提供新的思路。

肝细胞癌（HCC）是常见的原发性肝脏恶性肿瘤，术后5年复发转移率高达60%-70%。我们发现肝癌组织中FTO的表达水平降低是导致m-6-a异常升高的重要原因，与肝癌术后复发密切相关；体内外实验证实FTO可抑制肝癌细胞增殖、侵袭、原位瘤生长与肺转移；RNA-seq测序鉴定了FTO介导RNA的m-6-a修饰调控肝癌转移复发的特异性RNA（VEGFA、PDGF等）；进一步，蛋白芯片证实FTO介导mRNA m-6-a表观修饰，通过RNA转录后表观修饰，负性调控肝癌转移相关的特异性基因的表达，抑制肝癌侵袭转移。该研究成果投稿于“Cancer Res，审稿”。同时发现HNRNPAB可抑制lnc-ELF209，体内外实验证实lnc-ELF209在抑制肝癌细胞的迁移，侵袭和上皮间质转化(EMT）中起着关键作用。HNRNPAB-IncELF209调控轴在肝癌转移复发过程中起着重要作用。该结果以第一作者，“Int J Cancer" 杂志(2020年，IF=5.145）。我们首先应用系统炎症指数（SIS）评估肝内胆管细胞癌（ICC）术后临床预后，SIS由肿瘤标志物CA19-9水平和淋巴细胞、单核细胞计算生成，发现SIS是判断ICC患者术后OS和TTR 的独立预后因素；另外，我们提出ICC术后2年内肿瘤复发定义为ICC早期复发，ICC术后早期复发（2年内复发）是影响ICC临床预后的独立预后因素；多因素分析发现肿瘤个数、淋巴结转移和血清CA19-9水平是判断ICC患者术后早期复发的独立预后因素；我们研究发现血清CA19-9水平、肿瘤数目、淋巴结转移（LNM）是影响ICC患者术后TTR与OS的独立预后因素。这些结果以第一或通讯作者分别发表在“J Cancer”（2020年，IF=3.565）、“Front. Oncol”(2020年，IF=4.848）和“中国癌症杂志”(2020年，北大核心论文）。以第一作者或通讯作者发表与本课题相关的论文4篇（SCI收录3篇）。受邀至英国伦敦参加"5th World Congress on Cancer Research & Therapy"，并做了大会发言。在本项目资助下，培养博士研究生1人。