SUMO化调控CARMA1信号在ABC型弥漫大B细胞淋巴瘤发病中的作用及机制

Activated B cell-like subtype of diffuse large B cell lymphoma (ABC DLBCL) threatening human health and life a lot, is a kind of hematopoitic malignancy, whose oncogenic mechanisms still remain unclear. A hallmark of ABC DLBCL oncogenesis is constitutive activation of the NF-κB pathway, and the CARMA1/BCL10/MALT1 (CBM) complex is the crucial regulator of NF-κB constiutive activation. It has been identified that CARMA1 is a lymphocyte-specific oncogene with high frequency oncogenic mutations in ABC DLBCL. However, the regulationary mechanisms of CARMA1, especially for its post-translational modification, are not very clear. Our previous studies demonstrated that CARMA1 is a new substrate of SUMO1, suggesting that the sumoylation of CARMA1 may play an impotant role in ABC DLBCL oncogenesis. In this project, we will further confirm the regulation of CARMA1 by SUMO, elucidate the regulationary mechanisms of CARMA1 sumoylation on the formation of CBM complex and activation of NF-κB pathway, and clarify the role of CARMA1 sumoylation in ABC DLBCL oncogenesis by in vitro and in vivo experiments. This study may benefit us in understanding the pathogenesis of ABC DLBCL and provide theoretical support for the development of novel therapeutic agents.

ABC型弥漫大B细胞淋巴瘤（DLBCL）是一种严重威胁人类健康和生命的血液系统肿瘤，其发生机制未明。NF-κB信号通路的持续、过度激活是其发病的关键，而CARMA1、BCL10与MALT1形成CBM复合体是NF-κB激活的关键调控子。CARMA1被鉴定为淋巴系统肿瘤特异表达的致癌基因，且在ABC型DLBCL中具有高突变频率。但是，CARMA1的调控机制，特别是其翻译后修饰调控所知甚少。我们前期发现CARMA1是SUMO1修饰的新底物，并提出其SUMO化修饰在ABC型DLBCL的发病中具有重要作用。本项目拟进一步明确CARMA1的SUMO化修饰；探明CARMA1的SUMO化修饰对CBM复合体形成及NF-κB通路激活的调控机制；体外、体内实验阐明其对ABC型DLBCL发生发展的影响。如期完成，可加深对ABC型DLBCL发病的认识，并为靶向CARMA1的药物设计提供新的活性结合位点。

NF-κB信号通路的持续、过度激活是ABC型弥漫大B细胞淋巴瘤（DLBCL）发病的关键因素之一。CARMA1、BCL10与MALT1形成CBM复合体是NF-κB激活的关键调控子，但CARMA1的后修饰调控机制还未完阐明。本研究分析了CARMA1基因在不同血液肿瘤中的表达及对预后的影响；SUMO化修饰对CARMA1的调控及其在DLBCL细胞增殖中的作用。结果：（1）CARMA1基因在不同DLBCL患者中的表达差异较大，而MALT1和BCL10基因差异较小，CARMA1基因高表达组的患者预后差。（2）通过在各种血液肿瘤中筛选，发现CARMA1基因还在T细胞淋巴细胞白血病（T-ALL）细胞中高表达，其表达与预后具有显著相关性。但是，MALT1和BCL10基因对预后的表达无显著影响。说明在CBM复合体中，MALT1和BCL10基因可能是组成性表达，而CARMA1基因是调节性表达。（3）CARMA1基因沉默可显著抑制ABC型DLBCL和T-ALL细胞活性和增殖速率，并阻断细胞周期进程。（4）CARMA1蛋白可以被SUMO化修饰，具有3个SUMO化修饰典型的修饰位点。（5）SUMO化位点突变后，CARMA1蛋白的稳定性和磷酸化水平显著降低，CBM复合体形成能力降低，下游NF-κB通路转录活性也显著降低。说明SUMO化对其功能具有重要调控作用。（6）CARMA1蛋白的SUMO化修饰位点突变后，DLBCL细胞的增殖速率显著降低，在小鼠体内的成瘤能力也显著降低。（7）靶向阻断CARMA1\NF-κB通路可抑制ABC型DLBCL细胞的增殖。综上，本研究阐明了CARMA1蛋白的SUMO化修饰在调控ABC型DLBCL细胞增殖中具有重要作用。本研究还加深了对ABC型DLBCL发病的认识，为靶向CARMA1的药物设计提供实验基础。