Basis of PAX3-FKHR oncogenesis in rhabdomyosarcoma

描述(申请人提供)：肺泡型横纹肌肉瘤(ARMS)是一种高度恶性的肿瘤，它含有独特的t(2；13)染色体易位标记，导致PAX3-FKHR融合转录因子的形成，作为融合过程的结果，PAX3-FKHR获得了调节通常不受Pax3和FKHR调控的基因表达的能力。这种改变的基因靶向性是PAX3-FKHR致癌作用的原因。因此，了解肿瘤特异性激活/失活途径的基础将为患者护理管理的治疗设计提供有用的决定因素。当前拨款提案的目标是表征导致PAX3-FKHR转化细胞恶性表型的肿瘤特异性调控机制。初步研究的两条证据表明，蛋白降解在PAX3-FKHR介导的肿瘤发生中起重要作用。其一，PAX3-FKHR异常激活基质分解素-11基因表达。基质分解素-11基因的异常表达与肿瘤的侵袭和转移表型密切相关，这一特征主要见于手臂。第二，PAX3-FKHR加速26S蛋白小体依赖的周期蛋白激酶抑制物p27Kipl蛋白的降解，p27Kipl蛋白是参与细胞周期调控的关键调节因子。本研究的目的1是为了更好地了解PAX3-FKHR激活基质分解素-1基因的调控机制以及基质分解素-1 1在PAX3-FKHR依赖性肿瘤发生中的作用。这将在融合蛋白和手臂肿瘤的侵袭和转移临床行为之间提供一种机制联系。目的2重点研究PAX3-FKHR下调p27kipl蛋白表达的分子步骤。最后，在目标3中，我们将研究PAX3-FKHR对细胞周期调节蛋白的解除调控在其抑制肌源性分化能力中的作用。AIMS 2和AIMS 3中概述的研究将为手臂细胞的不受控制的生长和分化表型提供分子基础。拟议的研究将进一步加深我们对遗传异常与ARM发病机制之间的联系的理解；它们还将扩大我们利用这些信息进行患者诊断/或预后并设计专门干扰肿瘤功能而不损害正常细胞功能的治疗试剂的能力。

DESCRIPTION (provided by applicant): Alveolar rhabdomyosarcoma (aRMS) is a highly malignant tumor and it harbors a unique t (2;13) chromosomal translocation marker that leads to the formation of PAX3-FKHR fusion transcription factor, As the result of fusion process, PAX3-FKHR gains the ability to regulate expression of genes that are not normally regulated by Pax3 and FKHR. This altered gene targeting property is responsible for the oncogenic action of PAX3-FKHR. Therefore, understanding the basis of tumor-specific activation/inactivation pathways will provide useful determinants in therapeutic designs for patient care management.The objective of the current grant proposal is to characterize tumor-specific regulatory mechanisms that contribute to the malignant phenotype in PAX3-FKHR transformed cells. Two lines of evidence from the preliminary study suggest that protein proteolysis plays an important role in PAX3-FKHR mediated oncogenesis. One, PAX3-FKHR aberrantly activates stromelysin-1 1 gene expression. Abnormal expression of stromelysin-1 1 gene is closely associated with tumor invasion and metastatic phenotypes, a characteristic that is found predominantly in the aRMS. Second, PAX3-FKHR accelerates 26Sproteosome dependent degradation of cyclin kinase inhibitor p27Kipl protein, a key regulator involved in cell cycle regulation. Aim 1 of this research is designed to gain a better understanding of regulatory mechanism involved in stromelysin-1 gene activation by PAX3-FKHR and the functional role of stromelysin-1 1 in PAX3-FKHR dependent tumorigenesis. This will provide a mechanistic link between the fusion protein and invasive and metastatic clinical behavior in aRMS tumors. Aim 2 focuses on characterizing the molecular steps involved in PAX3-FKHR down-regulation of p27kipl protein accumulation. Finally, in Aim 3, we will examine the role of deregulation of cell cycle regulatory proteins by PAX3-FKHR in its ability to inhibit myogenic differentiation. Studies outlined in aims 2 and 3 will provide a molecular basis for the uncontrolled growth and differentiation phenotypes in aRMS cells.The proposed studies will further our understanding of mechanistic association between genetic abnormality and pathogenesis of aRMS; they will also expand our ability to use this information for patient diagnosis/or prognosis and to design therapeutic reagents that specifically interrupt tumor function without damaging normal cell function.