pre-mRNA剪接因子SF3B4通过可变剪接调控脂质代谢促进肝癌发展的分子机制研究

Hepatocellular carcinoma (HCC) is one of the most lethal of human malignancies. During human multistep hepatocarcinogenesis, genomic gain represents an important mechanism in the activation of proto-oncogenes. Gain of chromosome 1q21 is the most frequent minimal amplifying region in HCC. A better understanding of the roles of target genes within 1q21 amplicon will significantly improve our knowledge in HCC pathogenesis, and may lead to a much more effective management of HCC. The splicing factor SF3B4 (SF3B4) is located in recurrently altered region Chr1q21.2. Its roles in the progress of HCC has not been studied yet. Our preliminary studies revealed that SF3B4 expression was significantly increased in HCC tissue compared to paracancerous tissue, and the expression level of SF3B4 was related to tumor size, TNM stage, the overall survival rate and relapse-free survival rate of HCC patients. Afterwards, we found that downregulation of SF3B4 significantly inhibited growth of HCC in vivo and in vitro. We will go further to reveal how SF3B4 expression is modulated by genetics and the molecular mechanisms of SF3B4 in regulating HCC growth.

肝细胞癌(HCC)是原发性肝癌最常见的类型，致死率极高。基因组拷贝数扩增是HCC的一个重要特征,其中1q21区域扩增的发生频率最高且与HCC的早期发生密切相关。剪接因子SF3B4位于染色体1q21.2区域，能够与pre-mRNA直接结合。我们在前期研究中首次发现，SF3B4在肝癌组织中的表达显著高于癌旁组织，且其表达水平与肿瘤大小、Grad分级、TNM分期、病人总生存率及无病生存率显著相关。通过shRNA干扰SF3B4的表达，能够显著抑制肝癌细胞在体内和体外的生长，进一步通过RNA测序和数据分析，筛选出SF3B4可以剪接调控的脂代谢相关靶基因ACSS2。本课题将深入研究SF3B4在肝癌中高表达的调控机理，并进一步阐明其通过调控ACSS2的可变剪接促进肝癌发展的具体分子机制。

我们通过对HCC高频扩增区域1Q21处的基因进行筛选，发现剪接因子SF3B4在肝癌组织中的表达显著高于癌旁组织，且其表达水平与肿瘤大小、Grad分级、TNM分期、病人总生存率及无病生存率显著相关。利用shRNA慢病毒干扰，下调SF3B4的表达能够显著抑制肝癌细胞在体内和体外的生长；通过RNA测序和数据分析，筛选出SF3B4可以剪接调控的脂代谢相关靶基因ACSS2。ACSS2-S2在HCC中的相对高表达与病人生存预后显著负相关；免疫荧光实验显示ACSS2-S2主要定位于细胞核中，能够促进HCC细胞的增殖和迁移；进一步的GSEA分析显示，ACSS2-S2促进HCC细胞中核糖体合成。通过本项目研究，我们发现SF3B4不仅具有作为预后标志物的潜力，还具有HCC新的治疗靶点的潜力。