Pax5:Hematopoietic Transcription Factor Involved in ALL

描述（申请人提供）：PAX5是介导b淋巴细胞分化的关键转录因子之一。它通过转录激活和抑制大量基因，这些基因允许b淋巴细胞的发育，并阻止分化为t淋巴细胞或骨髓细胞。我们用SNP芯片检测了633例急性淋巴细胞白血病（ALL）样本的PAX5改变（469例儿童病例，70例儿童复发病例，74例成人病例和50例ALL样本作为异种移植生长）。PAX5基因组异常发生在27%的样本中，包括26个PAX5与其他5个基因中的一个融合。该资助的总体目标是了解ALL中PAX5改变的临床和病理意义。特异性目的1将确定ALL中PAX5基因组异常的频率，并确定其临床影响。特异性目标2将定义和理解PAX5融合和突变蛋白在ALL中的异常功能（体外研究）。研究将包括凝胶阻滞和报告基因分析，以及测试这些蛋白质转录激活选定靶基因的能力。详细的研究将使用两种PAX5融合物[PAX5- etv6；PAX5- C20orf112 (C20)]，包括利用cDNA微阵列分析和高通量ChIP测序研究在ALL中鉴定PAX5融合蛋白的靶基因。综合验证结果将使用多种技术。同时，PAX5融合蛋白对造血细胞分化的影响也将被确定。特异性目的3将使用体内模型来检查PAX5融合和缺失的异常功能。首先，我们将确定PAX5融合蛋白的表达是否会通过损害分化、促进特定细胞室的生存和/或增殖来破坏正常的稳态淋巴系统或造血系统。其次，我们将确定与PAX5融合蛋白协同诱导ALL的次要事件。第三，我们将确定PAX5缺失是否会影响人类Ph1+ ALL异种移植物的病程。综上所述，我们将首次将PAX5的改变与患者的临床和病理特征联系起来，并充分定义这些改变的功能意义。这些研究对该病的分类、提供新的治疗靶点以及加深我们对ALL发病机制的认识具有重要意义。公共卫生相关性：634例ALL样本中约27%的PAX5淋巴样转录因子结构异常。我们的研究将首次为急性淋巴细胞白血病（ALL）中PAX5改变的临床意义提供见解，并为ALL中PAX5改变的功能分支提供理解。我们的研究将为急性白血病提供新的治疗靶点，并对ALL的生物学有更深入的了解。

DESCRIPTION (provided by applicant): PAX5 is one of the key transcription factors mediating differentiation of B-lymphocytes. It transcriptionally activates and represses a very large number of genes that permits the development of B-lymphocytes and prevents differentiation to T-lymphocytes or myeloid cells. We examined by SNP chip 633 acute lymphocytic leukemia (ALL) samples for PAX5 alterations (469 pediatric cases, 70 pediatric relapse cases, 74 adult cases and 50 ALL samples growing as xenografts). PAX5 genomic abnormalities occurred in H 27% of the samples including 26 PAX5 fusions to one of 5 other genes. Overall goal of the grant is to understand the clinical and pathologic significance of PAX5 alterations in ALL. Specific Aim 1 will determine frequency of genomic abnormalities of PAX5 in ALL and determine their clinical impact. Specific Aim 2 will define and understand the aberrant functions of PAX5 fusion and mutant proteins in ALL (Ex Vivo Studies). Studies will include gel retardation and reporter gene analysis as well as testing the ability of these proteins transcriptionally to activate selected target genes. Detailed studies will be done using two of the PAX5 fusions [PAX5-ETV6; PAX5- C20orf112 (C20)] including genome-wide identification of target genes of PAX5 fusion proteins in ALL using cDNA microarray analysis and high through-put ChIP sequencing studies. Comprehensive validation of the results will use a variety of techniques. Also, effect of PAX5 fusion proteins on hematopoietic cell differentiation will be determined. Specific Aim 3 will use in vivo models to examine the aberrant function of PAX5 fusions and deletions. First, we will determine if expression of PAX5 fusion proteins disrupts normal steady-state lymphopoiesis or hematopoiesis by impairing differentiation, promoting survival and/or proliferation of specific compartments? Second, we will identify secondary events that synergize with PAX5 fusion proteins to induce ALL. Third, we will determine if PAX5 deletions affect the course of human Ph1+ ALL xenografts. In summary, we will for the first time, correlate PAX5 alterations with clinical and pathological characteristics of the patients and define fully the functional significance of these alterations. These studies will have importance for classification of the disease, offer new therapeutic targets and foster our understanding of the pathogenesis of ALL. PUBLIC HEALTH RELEVANCE: PAX5 lymphoid transcription factor is structurally abnormal in approximately 27% of 634 ALL samples. Our studies will for the first time provide insights into the clinical significance of PAX5 alterations in acute lymphocyte leukemia (ALL), as well as provide an understanding of the functional ramifications of PAX5 alterations in ALL. Our studies should lead to new therapeutic targets for acute leukemias, as well as provide a greater understanding of the biology of ALL.