弥漫大B细胞淋巴瘤中PRDM1/BLIMP-1异常失活及化疗耐药机制研究

Diffuse large B-cell lymphoma (DLBCL) is the most common type of lymphomas, accounting for 30%–40% of all non-Hodgkin lymphoma. Gene expression profiling has identified two main distinct types of DLBCL: germinal center B-cell-like and activated B-cell-like (GCB and ABC). Patients with ABC-DLBCL have markedly poorer survival than do patients with GCB-DLBCL. BLIMP-1, encoded by PRDM1, is a zinc-finger-containing DNA-binding transcriptional repressor required for the development of immunoglobulin-secreting cells. Our previous findings suggest that PRDM1/BLIMP-1 is frequently inactivated in ABC-DLBCL and PRDM1/BLIMP-1 disruption is associated with inferior prognosis; that PRDM1 mutations differentially affect prognosis depending on its location within the specific domain; that miRNA regulates BLIMP-1 expression; that loss of BLIMP-1 expression is associated with increased expression of c-Myc. Therefore, we hypothesize that loss of PRDM1/BLIMP-1 function contributes to the overall poor prognosis of ABC-DLBCL patients. In this application, our project intends to investigate PRDM1/BLIMP-1 disruptions (including deletion, mutation and loss of protein expression) in DLBCL; to elucidate miRNA regulation mechanism in BLIMP-1 expression; to explore the molecular basis of PRDM1 mutation as a survival biomarker for DLBCL; to study the transcription repression of PRDM1/BLIMP-1 upon MYC and its relationship with tumor cell survival and chemo-resistance. This project shall provide a detailed investigation regarding the role of PRDM1/BLIMP-1 aberration in ABC-DLBCL, as well as novel therapeutic strategies to overcome relapsed/refractory DLBCL.

弥漫大B细胞淋巴瘤（DLBCL）是最常见的淋巴瘤，其活化B细胞样（ABC）亚型预后显著差于生发中心B细胞样亚型。BLIMP-1蛋白由PRDM1基因编码，参与调节浆细胞转化。我们发现ABC-DLBCL中广泛存在PRDM1/BLIMP-1异常，并与差预后相关；PRDM1基因突变对预后的影响与突变位置有关；miRNA可调控BLIMP-1表达；BLIMP-1缺失与c-Myc高表达相关。由此提出假说：PRDM1/BLIMP-1异常导致ABC-DLBCL预后差及化疗耐药。本课题拟研究DLBCL患者PRDM1基因缺失、突变及BLIMP-1蛋白表达情况；揭示miRNA对BLIMP-1的调控机制；阐明位于不同功能域的PRDM1突变对蛋白功能的影响；探讨BLIMP-1转录抑制MYC，从而抑制肿瘤细胞增殖、生存。通过揭示PRDM1/BLIMP-1异常在ABC-DLBCL化疗耐药中的作用，指导相应靶向治疗的开展。

PRDM1基因位于人类染色体6q21，其编码蛋白BLIMP-1是一种包含锌指结构的转录抑制因子，通过抑制BCL-6、PAX5、CIITA等生发中心B细胞分子，促进B细胞向浆细胞分化。选择性敲除小鼠B淋巴细胞的PRDM1基因可诱导小鼠出现与人类ABC-DLBCL高度相似的淋巴增殖性肿瘤，但PRDM1异常在ABC-DLBCL中的临床意义及作用机制尚不清楚。本研究通过患者标本研究PRDM1在ABC DLBCL的基因和蛋白异常及其临床意义；探讨PRDM1在ABC DLBCL的抑癌作用机制调控网络；并阐述PRDM1突变对ABC DLBCL生存、耐药的影响。研究发现：①初治ABC DLBCL中，8.2%存在PRDM1双等位基因缺失，26%存在PRDM1突变，63.2%PRDM1蛋白表达缺失，其中PRDM1双等位基因缺失和突变均与不良预后相关；②在ABC DLBCL细胞系中过表达PRDM1，细胞增殖受抑；且PRDM1表达水平与p53及其下游分子呈正相关，可能受到p53转录调控，进而转录抑制MYC，起到抑癌作用；③PRDM1突变导致蛋白稳定性差，易于降解，蛋白酶体抑制剂硼替佐米可选择性作用于PRDM1突变的ABC DLBCL细胞系，提高PRDM1蛋白水平，促进肿瘤细胞凋亡。通过以上研究阐明PRDM1异常在ABC DLBCL发病机制和耐药机制中的作用，为开展相应的靶向治疗，以及预测和克服耐药提供理论依据。