Role of LEDGF/p75 in MLL chemoresistance. Role of LEDGF/p75 in MLL chemoresistance

The study has been focused on the characterization of the role of LEDGF/p75 in chemiresistance in pediatric leukemia Abstract: MLL is an aggressive subtype of leukemia with a poor prognosis that mostly affects pediatric patients. MLL-rearranged fusion proteins (MLLr) induce aberrant target gene expression resulting in leukemogenesis. MLL and its fusions are tethered to chromatin by LEDGF/p75, a transcriptional co-activator that specifically recognizes H3K36me2/3. LEDGF/p75 is ubiquitously expressed and associated with regulation of gene expression, autoimmune responses and HIV replication. LEDGF/p75 was proven to be essential for leukemogenesis in MLL. Apart from MLL, LEDGF/p75 has been linked to lung, breast and prostate cancer. Intriguingly, LEDGF/p75 interacts with Med-1, which co-localizes with BRD4. Both are known as co-activators of super-enhancers. Here, we describe LEDGF/p75-dependent chemoresistance of MLLr cell lines. Investigation of the underlying mechanism revealed a role of LEDGF/p75 in the cell cycle and in survival pathways and showed that LEDGF/p75 protects against apoptosis during chemotherapy. Remarkably, LEDGF/p75 levels also affected expression of BRD4 and Med1. Altogether, our data suggest a role of LEDGF/p75 in cancer survival, stem cell renewal, and activation of nuclear super enhancers. Overall design: 2 groups of #4 samples each. In group 1 we have analyzed ThpI cells shMOCK as a control group in comparison with group 2 constituted by ThpI cells shLEDGF/p75

本研究聚焦于解析晶状体上皮源性生长因子p75（LEDGF/p75）在儿童白血病化疗耐药中的作用特征。摘要：混合谱系白血病（Mixed Lineage Leukemia, MLL）是一类侵袭性强、预后极差的白血病亚型，多发于儿童患者。MLL重排融合蛋白（MLL-rearranged fusion proteins, MLLr）可诱导靶基因异常表达，进而引发白血病发生。MLL蛋白及其融合蛋白可通过LEDGF/p75锚定至染色质，该转录共激活因子可特异性识别组蛋白H3K36me2/3修饰位点。LEDGF/p75在机体各组织中广泛表达，参与基因表达调控、自身免疫应答及HIV复制过程。已有研究证实，LEDGF/p75对MLL相关白血病的发生至关重要。除MLL白血病外，LEDGF/p75还与肺癌、乳腺癌及前列腺癌的发生发展密切相关。值得注意的是，LEDGF/p75可与中介体复合物亚基1（Mediator complex subunit 1, Med-1）相互作用，而Med-1与溴结构域蛋白4（Bromodomain-containing protein 4, BRD4）共定位，二者均被鉴定为超级增强子的共激活因子。本研究阐明了MLLr细胞系中LEDGF/p75依赖性的化疗耐药表型。对潜在机制的探究显示，LEDGF/p75可参与细胞周期调控及细胞存活通路，并能减轻化疗诱导的细胞凋亡。此外，LEDGF/p75的表达水平还可调控BRD4与Med1的基因表达。综上，本研究数据表明LEDGF/p75在肿瘤细胞存活、干细胞自我更新及核内超级增强子激活过程中发挥关键作用。总体实验设计：共设置2组，每组含4份样本。第1组为转染对照短发夹RNA（shMOCK）的ThpI细胞，作为对照组；第2组为转染靶向LEDGF/p75的短发夹RNA（shLEDGF/p75）的ThpI细胞。