pre-mRNA剪接因子PRPF3在肝癌发生发展中的作用及其分子机制研究

Hepatocellular carcinoma (HCC) is among the most lethal of human malignancies. Chromosome copy number variation (CNV) is an important event in HCC development, proto-oncogenes is often hides in the area of copy number amplification. Gain of chromosome 1q21 copy is one of the most frequently detected alterations in primary HCC cases. A better understanding of the target genes within 1q21 amplicon will significantly improve our knowledge in HCC pathogenesis, and may lead to novel markers or therapeutic targets of HCC bearing amplification of 1q21. The pre-mRNA processing factor 3 (PRPF3) is a recently identified oncogene localized at 1q21.1. It has been reported that PRPF3 is novel candidate genes targeted by hepatic transcription factor HNF4α in HCC, but its roles in the progress of HCC has not been studied yet. Our preliminary studies revealed that PRPF3 expression was significantly increased in HCC tissue compared to paracancerous tissue, and the expression level of PRPF3 was related to tumor size, TNM stage, the overall survival rate and disease-free survival rate of HCC patients. Afterwards, we found that downregulation of PRPF3 significantly inhibited while overexpression of PRPF3 promoted the growth of HCC in vivo and in vitro. To clarify the PRPF3 dependent pathway in HCC process, we will go further to reveal how PRPF3 expression is modulated by genetics and epigenetic factors and the target pre-mRNA regulated by this splicing factor.

肝细胞癌(HCC)是人类死亡率最高的恶性肿瘤之一。染色体拷贝数变异(CNV)是HCC发生发展过程中的重要事件，DNA拷贝数扩增区常常存在潜在的癌基因。1q21扩增在HCC患者中发生频率最高，因此对该扩增子上基因的研究将有助于我们对HCC发病机制的认识，为HCC患者寻找新的肝癌标志物或治疗靶点提供理论依据。pre-mRNA剪接因子3(PRPF3)正位于高频扩增区1q21.1，其表达受肝转录因子HNF4α的调控，但是它在HCC发生发展中的作用国内外鲜有报道。我们初步研究发现，PRPF3在肝癌组织中表达显著高于癌旁组织，且其表达水平与肿瘤大小、TNM分期、病人的预后密切相关。我们在体内和体外水平已明确，下调PRPF3能够抑制肝癌生长，而上调PRPF3则促进肝癌生长。本课题将深入研究PRPF3在肝癌中表达上调的遗传学和表观遗传学调控机制，明确其剪接调控的靶基因，揭示其发挥作用的上下游通路。

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PRPF3正位于高频扩增区1q21.1。我们在研究中首次发现，PRPF3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、TNM分期、病人总生存率及无病生存率显著相关。在肝癌细胞系中PRPF3 mRNA和蛋白水平表达量都显著高于正常肝细胞。且其表达水平与其他参与U4/U6小核核糖蛋白(snRNPs)蛋白组份表达水平具有一致性。通过细胞功能实验已明确，下调PRPF3抑制肝癌细胞活力和克隆形成能力、抑制肝癌细胞侵袭和迁移能力。通过皮下异体移植瘤实验已明确，PRPF3促进肝癌细胞增值和异体成瘤能力。通过HCC数据库相关资料进行分析，我们发现PRPF3 基因拷贝数显著增加。进一步通过TCGA测序数据和RNA-seq分析，发现PRPF3可以剪接调控116个靶基因转录本，包括支架蛋白靶基因DLG1。本课题将进一步深入研究PRPF3在肝癌中表达上调的遗传学和表观遗传学调控机制，并阐明其通过调控支架蛋白DLG1的可变剪接促进肝癌发展的具体分子机制。