stat3-miR-3677-PCDHG信号通路对肝癌细胞增殖与侵袭的影响

Hepatocellular carcinoma (HCC) has been the second leading cause of cancer-related deaths worldwide, with unfavorable prognosis, which highlights the significance of pathogenesis study for HCC. MicroRNAs (miRs) are a family of important regulators post-transcriptionally. With the analysis of miRs expression profiles of HCC from TCGA database, we find that miR-3677 is the most significantly altered and up-regulated miR in HCC. Furthermore, we show that knockdown of miR-3677 could inhibit HCC cell proliferation. These data implicate that miR-3677 probably exerts a tumor-promoting function in HCC. By the approach of bioinformatics, stat3 is predicted as the upstream transcriptional factor of miR-3677, and moreover, inhibition of stat3 function leads to suppression of miR-3677, thus suggesting that stat3 is a potential regulator of miR-3677. According to the prediction of TargetScan algorithm, PCDHG protein families are predicted as putative downstream targets of miR-3677. Besides, overexpression of miR-3677 could inhibit PCDHG expression, implying that miR-3677 takes part in HCC as an oncogene through targeting PCDHG expression. Collectively, we come up with the hypothesis that the transcriptional factor stat3 promotes up-regulation of miR-3677 which subsequently blocks expression of PCDHG, resulting in the development and progression of HCC. It is about to confirm the existence of stat3-miR-3677-PCDHG signaling pathway mediating the tumorigenesis of HCC.

肝癌已是全球癌症死亡第二位主因，生存预后较差，突显其发病机制研究的重要性。MiRs是重要的转录后调控因子。前期分析TCGA数据库肝癌miRs表达谱数据， 发现miR-3677是肝癌中表达差异最显著且上调的miR，且miR-3677下调能抑制肝癌细胞增殖，提示miR-3677可能发挥癌基因功能。生物信息学预测，stat3是miR-3677上游转录因子；而stat3抑制则下调miR-3677表达，提示stat3是miR-3677潜在的调控分子。采用软件预测，PCDHG家族是miR-3677下游靶基因，且miR-3677能够抑制PCDHG蛋白表达，提示miR-3677通过抑制PCDHG表达发挥癌基因功能。我们提出假设，转录因子stat3促进miR-3677表达上调，后者抑制PCDHG表达，从而促进肝癌发生与进展；如证实，则反证存在stat3-miR-3677-PCDHG通路介导肝癌发生与进展。

肝癌是全球癌症死亡第二位主因，临床预后差。microRNA是参与肝癌发生发展的重要小分子。本研究尝试研究miRNAs对肝癌复发转移和增殖的影响。主要研究内容分为两部分：研究miR-3677在肝癌增殖进程中的功能与机制；采用生物信息学与q-PCR验证方法，分析TCGA数据库肝癌组织miRNA表达谱，筛选、鉴定能够预测肝癌复发的miRNA标志物。重要结果：1.miR-3677在肝癌细胞和组织高表达；抑制miR-3677表达，能够抑制细胞增殖和克隆集落形成，导致细胞周期向S期转化减少。2.STAT3在肝癌组织高表达；抑制STAT3功能导致miR-3677表达显著下调，反之，过表达STAT3则促进miR-3677表达。3.过表达肝癌细胞miR-3677，导致下游靶基因PCDHGA3与PCDHGC3蛋白表达下调，反之，抑制miR-3677表达，则上调PCDHGA3与PCDHGC3蛋白表达。4.采用TCGA数据库肝癌标本miRNAs表达谱数据，采用生物信息学分析和q-PCR方法，筛选和鉴定let-7c, miR-22, miR-100-5p与miR-18a可作为肝癌复发的独立预测因子，并且miR-22与 miR-18a亦是肝癌生存期的独立预测标志物。关键数据：1.CCK-8实验与流式分析发现，miR-3677显著抑制细胞增殖，遏制细胞周期演进。2.采用logistic回归分析发现，let-7c, miR-22, miR-100-5p与miR-18a与肝癌复发显著相关；采用COX回归分析发现，miR-22与miR-18a与肝癌生存期显著相关。本研究科学意义在于证实miR-3677为肝癌生长的癌基因，抑制miR-3677能够抑制肝癌生长，发现能预测肝癌复发的miRNA标志物，有临床应用的潜在价值。