Islet-1调控的磷酸戊糖途径异常在弥漫大B细胞淋巴瘤中的作用及分子机制

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of malignant tumor in lymphatic system. For the heterogeneity and chemoresistance, DLBCL causes high mortality. Therefore, the elucidation of molecular mechanisms responsible for DLBCL tumorigenesis and development is urgently required to improve current therapeutic approaches. In previous studies, we found that elevated pentose phosphate pathway (PPP) might be positively correlated to DLBCL heterogeneity and chemoresistance, and might be regulated by an aberrant overexpressed factor Islet-1 in DLBCL. In the present study, we will determine the correlation between PPP dysregulation and malignant degree, chemoresistance or prognosis in DLBCL by clinical specimens analysis. Through the establishment of cell and animal model, we attempt to provide evidences that Islet-1 might be able to activate Sirtuin2 expression and improve the key enzyme G6PD dimerization and activation by forming a Islet-1/Sirtuin2/G6PD deacetylating complex. Furthermore, Islet-1 has the potential to increase glucose uptake through promoting Glut1 gene transcription. Based on these two mechanisms, the Islet-1 stimulated PPP dysregulation might be able to counteract CHOP induced oxidative damage. Taken together, our study plans to uncover a previously unknown mechanism by which Islet-1 mediates abnormal PPP to reduce chemosensitive in DLBCL, and these results may shed lights on a novel promising approach for the treatment of DLBCL with Islet-1 overexpression and PPP dysregulation.

弥漫大B细胞淋巴瘤（DLBCL）是淋巴系统恶性肿瘤中最常见亚型，其高死亡率的主要因素为高度异质性和耐药性的产生。因此，进一步阐明DLBCL的发生发展机制一直是其基础和临床研究的关键。我们发现，磷酸戊糖途径异常可能与DLBCL异质性及CHOP方案耐药性存在联系，并可能受到胰岛因子1（Islet-1）的调控。在本课题中，我们将对临床标本进行检测，确定磷酸戊糖途径异常与DLBCL恶性程度、耐药性及预后的相关性。通过细胞和动物模型的建立，探讨DLBCL代谢异常的功能及Islet-1对其调控的具体分子机制：Islet-1可能通过Islet-1/Sirtuin2/G6PD复合体而去乙酰化激活关键酶G6PD，并促进Glut1表达和葡萄糖摄入，从而增强磷酸戊糖途径并降低CHOP药物敏感性。本课题是由肿瘤代谢异常的机理来探讨DLBCL异质性和耐药性的新视角，其顺利完成可为DLBCL有效靶向治疗提供新的线索。

弥漫大B细胞淋巴瘤（DLBCL）是淋巴系统恶性肿瘤中最常见亚型，其高死亡率的主要因素为高度异质性和耐药性的产生。因此，进一步阐明DLBCL的发生发展机制一直是其基础和临床研究的关键。我们发现，磷酸戊糖途径异常可能与DLBCL异质性及CHOP方案耐药性存在联系，并可能受到胰岛因子1（Islet-1）的调控。在本课题中，我们通过对临床标本进行检测，发现DLBCL中存在磷酸戊糖途径异常激活以及G6PD表达和活性的增加，并且在高危的Non-GCB亚型中G6PD表达强阳性率较高，而在恶性程度较低的GCB亚型中表达强度及阳性率相对较低。G6PD的高表达与肿瘤大小及结外淋巴侵袭成正相关，并提示患者不良预后。细胞水平检测发现，Non-GCB-DLBCL细胞中存在明显的G6PD和Islet-1表达水平升高。进一步，应用酶检测试剂盒对各DLBCL细胞系中的G6PD活性进行检测，结果提示G6PD在Non-GCB-DLBCL细胞系中的激活更为明显。Non-GCB-DLBCL细胞的CHOP IC50高于GCB-DLBCL细胞，且Iselt1、G6PD表达水平与DLBCL细胞的CHOP化疗药物耐药性呈正相关。通过稳定细胞构建及CHOP刺激检测，发现Islet-1调控的磷酸戊糖代谢异常可能通过清除ROS而抑制CHOP引起的细胞凋亡及增殖抑制。在动物模型中，应用CHOP、G6PD抑制剂及二者联合用药治疗，发现Islet-1、G6PD高表达可显著促进肿瘤体积增加、生存期明显缩短。并且，G6PD抑制剂可明显增加CHOP药物的敏感性。以上细胞和动物水平检测确定了Islet-1调控的磷酸戊糖途径异常在DLBCL具有抑制凋亡的作用。进一步通过Real-time RT-PCR、Western blot、荧光素酶报告、染色质免疫共沉淀、Co-IP等技术，揭示了Islet-1可转录调控Glut1和Sirtuin2基因表达，并通过Islet-1/Sirtuin2/G6PD复合体调控G6PD酶活性，从而导致DLBCL磷酸戊糖途径异常激活。本课题是由肿瘤代谢异常的机理来探讨DLBCL异质性和耐药性的新视角，将为DLBCL有效靶向治疗提供新的线索。