COP1通过p53—Brn-3a调控Bcl-2的表达在CLL发病中的作用机制研究

Chronic lymphocytic leukemia (CLL) is the most common type of leukemia characterized by clonal B-cell proliferation. A key feature of CLL cells is the high expression level of the anti-apoptotic protein Bcl-2, which maintains apoptotic resistance and confers a consistent-accumulation phenotype. However, the pathogenesy was unclear in the development of CLL via regulation of Bcl-2 pathway. COP1, an E3 ubiquitinligase, has been reported to be involved in proliferation and apoptosis in cancer cells through regulating the ubiquitin degradation of p53. As yet, the effect of COP1 in CLL has not been reported. Our previous study showed that the expression of Bcl-2 was regulated by p53-Brn-3a complex in CLL cells. In addition, high expression level of COP1 in CLL sample and cell line inhibited the formation of p53-Brn-3a complex, which further promoted the expression of Bcl-2, suggesting the involvement of COP1 in the pathogenesy of CLL. The purpose of this project is to elucidate how the COP1 regulated the expression of Bcl-2 through p53-Brn-3a complex, involving the pathogenesy of CLL. This study would improve the understanding of CLL pathogenesy.

慢性淋巴细胞白血病（CLL）是B细胞克隆性增殖疾病中最常见的一类。Bcl-2的高表达是维持其抗凋亡并持续积累的重要因素，然而调控Bcl-2信号通路参与CLL发病的分子机制目前尚不清楚。COP1是调控p53泛素化降解、参与肿瘤细胞增殖与凋亡进程的泛素连接酶，但迄今，COP1在CLL发病中的作用未见报道。我们研究显示，在CLL细胞中，Bcl-2的表达受p53—Brn-3a复合物的调节。进一步发现，COP1在CLL病例中高表达，并通过抑制CLL细胞系中p53—Brn-3a复合物的形成促进Bcl-2表达，提示COP1可能参与CLL的发病过程。本研究拟进一步结合CLL临床病例，体外及动物实验，阐明COP1通过p53—Brn-3a复合物调控Bcl-2表达在CLL发病中的分子机制。如期完成后，可加深对CLL发病机制的认识。

慢性淋巴细胞白血病是一种典型的B细胞过度积累导致的疾病，大多由于基因突变或者异常表达导致细胞表现出抗凋亡或发生细胞周期G0/G1 期阻滞。我们研究显示，光组成形蛋白COP1在Binet C期的白血病患者外周血有核细胞中呈高表达趋势，并且COP1主要参与调控DNA损伤，我们推测COP1的高表达可能与CLL细胞表现出的抗凋亡特性有关。我们首先构建了过表示COP1的CLL细胞株HG3-GFP以及HG3-COP1，体外及体内检测2组细胞对药物诱导的细胞凋亡的反应。研究结果现实，过表达COP1延迟氟达拉宾诱导的细胞凋亡。进一步的机制分析显示，COP1 通过泛素化降解p53 ，扰乱p53对Brn-3a的拮抗作用，激活了Bcl-2的转录活性，促进细胞存活。此外，体内实验显示，当给予实验小鼠氟达拉宾联合环磷酰胺治疗时，与对照组相比，HG3-COP1的移植小鼠显示了更短的存活时间，更显著的CLL在脾脏及骨髓的累积，且细胞凋亡程度明显减弱。本研究说明COP1在CLL患者中的高表达是促使CLL细胞对氟达拉宾表现出凋亡抗性的重要的原因。