BCL11B在蕈样肉芽肿细胞凋亡抵抗中的作用及其机制

BCL11B is a key transcription factor in T cell development. As a repressive transcription factor, BCL11B inhibits gene transcription by recruiting histone de-acetylase (HDAC) to its N-terminal, which serves as a docking site for the formation of chromatin-modifying complex. It is showed that over-expressed BCL11B could inhibit cell apoptosis in immature T cells by inhibit the transcription of pro-apoptotic genes. In a previous study performed by the applicant, BCL11B was found to be up-regulated in the infiltrating malignant T cells in mycosis fungoides. Besides, the expression level of BCL11B increased with the progression of tumor stage. Mycosis fungoides (MF) is the most frequent subtype of cutaneous T cell lymphoma. However, the pathogenesis of this disease is largely unknown. Recently, people have attributed the progression of MF to the apoptosis resistance of those infiltrating malignant T cells. However, the mechanism of this apoptosis resistance is still unknown. Our previous study indicated the potential role BCL11B played in the pathogenesis of MF. Thus, this proposed study will focus on the role of BCL11B in the apoptosis resistance of MF cells and the molecular mechanism underlying it. By restoring or knocking-down BCL11B expression in MF cell line, the role of BCL11B expression in cell apoptosis, cell cycle, as well as in vitro/in vivo tumor forming will be observed. Further, the molecular pathway downstream BCL11B will be investigated, as well as the epigenetic mechanism of how BCL11B effect on the transcription of target genes. In conclusion, this study aims to demonstrate the role of aberrant BCL11B expression in the disease progression of MF and its underlying molecular pathway. BCL11B may serve as a novel molecular target for developing new therapies for MF, which currently does not have a cure.

BCL11B是新近发现的抑制性转录因子，在T细胞发育中十分重要，可以抑制胸腺细胞的凋亡。但其在成熟T细胞及其疾病中的作用尚不清楚。本课题组前期研究发现：BCL11B基因高表达于蕈样肉芽肿(MF)皮损中肿瘤性的T细胞上，且表达量随着疾病的进展而增加。MF是最常见的皮肤T细胞淋巴瘤，其发生发展的机制尚不清楚。近年来MF细胞对凋亡的抵抗被认为是肿瘤发展的重要原因。我们的前期研究提示BCL11B与MF疾病进展的关系。本项目拟以MF细胞系为体外研究模型，通过基因转导过表达及敲减BCL11B的表达，观察其对细胞增殖、凋亡的影响，以及体外、体内肿瘤形成的影响；并进一步阐明BCL11B影响MF细胞凋亡的通路及分子机制，证实BCL11B与靶基因启动子结合后，通过其蛋白质N端招募组蛋白乙酰化酶，抑制靶基因启动子活性，诱导MF细胞凋亡抵抗，促进疾病进展。本研究将为阐明MF的发病机制、开发靶向药物提供重要理论基础

由于发病机制不甚清楚，进展期皮肤T细胞淋巴瘤（CTCL）尚缺乏有效的治疗手段。组蛋白去乙酰化酶抑制剂（HDACi）是一种可用于进展期、难治性CTCL治疗的较新型药物，但客观反应率较低且药物疗效难以预测。本课题组前期研究发现，与良性炎症性皮肤病相比，蕈样肉芽肿（MF）皮损中T细胞分化发育关键调控蛋白BCL11B的表达异常升高。本研究旨在探索CTCL中B细胞白血病/淋巴瘤11B（BCL11B）表达水平与HDACi治疗反应间的关系及其内在机制，寻找可用于HDACi疗效预测的分子标记，探索CTCL治疗新靶点。本研究主要从以下五个方面进行了研究并取得相应结果：1. BCL11B表达水平与CTCL细胞系对HDACi敏感性间关系研究。7株CTCL细胞系间BCL11B表达水平差异显著，BCL11B高表达细胞系（H9、Hut78、HH）对SAHA诱导凋亡作用的敏感性显著高于低表达组（Myla、MJ、PB2B、Sz4）。2. 证实抑制BCL11B表达与HDACi处理具有协同促凋亡作用。H9、HH敲减BCL11B后，细胞活力显著下降，凋亡率显著升高，且细胞对SAHA凋亡诱导作用的敏感性增加。3. 证实H9中存在BCL11B与HDAC1/2的结合结构，该结构对BCL11B高表达细胞系的生存及凋亡抵抗具有重要作用。4. BCL11B与HDAC共同调控下游凋亡相关基因分析研究。表达谱芯片分析筛选出261个表达显著升高的基因，进行GO及KEGG通路分析证实差异基因主要富集在细胞凋亡与周期、细胞分解代谢调控等通路。5. MF皮损中BCL11B表达水平与HDACi临床疗效间的关系研究。检测46例MF皮损标本，T3期皮损BCL11B mRNA水平显著高于T1/2期，且采用伏立诺他单药治疗至少6个月的4例患者中，BCL11B表达水平高者（1例）治疗3月后疾病达到部分缓解（PR），BCL11B表达水平低者（3例）治疗无效。因此，本研究的科学意义在于证实了 BCL11B介导的表观遗传抑制对BCL11B高表达CTCL细胞系的生存及凋亡抵抗具有重要意义，同时也是HDACi治疗的重要靶点。CTCL患者皮损中BCL11B的表达水平可能作为HDACi的疗效预测指标。