MBNL1通过选择性剪切调控肝细胞癌发生发展机制的研究

HCC is one of the most common lethal malignancies in China for its aggressive property and limited therapeutic options. Previously studies suggested that aberrant alternative splicing (AS) promoted HCC genesis and development by activating oncogenic variants or inactivating tumor suppressors. Additionally, different spliced variants of the same gene, such as Numb PRR, KIAA0101 and TCF-4, could display antagonistic biological functions in HCC. .In our recently work, we found that AS factor MBNL1 was expressed much lower in HCC tumor than peritumoral tissues. Furthermore, we certificated that knocking-down of MBNL1 could significantly promote HCC cells proliferation, colony formation and stem maintain. These results indicate that MBNL1 might play a negative role in tumor genesis. In addition, results showed that the expression of MBNL1 was associated with AS variants of Numb PRR, KIAA0101 and TCF-4 in HCC tissues. Moreover, we found the expression of Numb PRRS, KIAA0101 tv2 and TCF-4C were increased, while Numb PRRL, KIAA0101 tv1 and TCF-4D were decreased, when we overexpressed the MBNL1 in HCC cells. Since MBNL1 protein can combine to Numb PRR RNA, we assume that MBNL1 could inhibit the HCC genesis and progress by mediating specific gene AS. However, the molecular mechanism of MBNL1 regulating in Numb PRR, KIAA0101 and TCF-4 gene AS on HCC genesis and progress are unclear. .In this project, we aim to provide a perspective that MBNL1 mediated AS is a critical mechanism for the development of HCC. Importantly, both MBNL1 and different variants may aid in the development of novel molecular targets of HCC therapy.

选择性剪切是决定生物蛋白质多态性的重要因素，与原发性肝癌（HCC）的发生、发展及耐药密切相关。MBNL1（Muscleblind-like 1）是一种具有基因选择性剪切活性的RNA结合蛋白。项目组前期研究发现MBNL1能够抑制肝癌细胞系的克隆形成、增殖和干性维持，与细胞命运决定子Numb PRR/TCF-4/KIAA0101等HCC相关基因的选择性剪切密切相关，参与上述基因剪切变异体的表达调控，在HCC肿瘤组织中表达明显降低，由此我们推断：剪切因子MBNL1可以通过直接/间接影响HCC特定基因的选择性剪切来抑制HCC的发生发展，在肝癌中处于功能缺陷状态。项目组拟通过氢氘交换质谱、RNA pull down、NOD-SCID模型等试验，系统地阐明MBNL1调控特定基因选择性剪切的分子机制，影响HCC的发生发展，并针对MBNL1探索新的治疗靶点，最终有效减缓或控制HCC的进展。

原发性肝癌是高度恶性且治疗靶点有限的肿瘤。本课题组前期研究表明：与癌旁组织相比较，MBNL1在肝癌干细胞及肝癌组织中异常高表达。敲低MBNL1可促进肝癌增殖及肿瘤的形成能力，而过表达MBNL1可促进肝癌增殖及肿瘤的形成能力；进一步发现并阐明了MBNL1可促进下游基因Numb、TCF4等基因的可变剪切，调控相应基因的表达和促进/抑制肝癌进程。研究结果揭示MBNL1可作为靶向治疗肝癌新的靶点。.我们的结果表明，组蛋白去甲基酶GASC1信号与肝癌患者的晚期预后差密切相关，GASC1缺失能抑制肝癌增殖和肿瘤生长。在HCC细胞群中存在GASC1水平的异质性表达，提示肿瘤起始生长能力差异。从机制上说，GASC1参与调节Rho GTPase信号通路的几个组成部分，包括其下游靶点ROCK2。GASC1去甲基酶活性抑制FBXO42（一种ROCK2蛋白泛素连接酶）的转录水平，从而通过K63连接的多泛素化水平调控ROCK2降解。另一方面，用GASC1抑制剂SD70治疗HCC细胞和HCC小鼠移植瘤模型，均可提高HCC细胞对标准化疗的敏感性。本研究提示GASC1是HCC治疗的潜在靶点，GASC1特异性治疗是HCC患者治疗的新希望。