Basis of PAX3-FKHR oncogenesis in rhabdomyosarcoma

描述（申请人提供）：肺泡横纹肌肉瘤（Alveolar rhabdomyosarcoma, aRMS）是一种高度恶性肿瘤，其具有独特的t（2;13）染色体易位标记，可导致Pax3 -FKHR融合转录因子的形成，通过融合过程，Pax3 -FKHR获得了正常情况下Pax3和FKHR无法调节的基因的表达能力。这种改变的基因靶向特性是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。当前拨款提案的目的是表征导致PAX3-FKHR转化细胞恶性表型的肿瘤特异性调节机制。初步研究的两项证据表明，蛋白水解在PAX3-FKHR介导的肿瘤发生中起重要作用。一，PAX3-FKHR异常激活基质溶解素- 11基因表达。基质溶素- 11基因的异常表达与肿瘤侵袭和转移表型密切相关，这一特征主要在aRMS中发现。其次，PAX3-FKHR加速26Sproteosome依赖性细胞周期蛋白激酶抑制剂p27Kipl蛋白的降解，p27Kipl蛋白是参与细胞周期调节的关键调节因子。本研究的目的1旨在更好地了解基质融解素-1基因被PAX3-FKHR激活的调控机制以及基质融解素- 11在PAX3-FKHR依赖性肿瘤发生中的功能作用。这将提供融合蛋白与aRMS肿瘤侵袭性和转移性临床行为之间的机制联系。Aim 2的重点是表征PAX3-FKHR下调p27kipl蛋白积累的分子步骤。最后，在Aim 3中，我们将研究PAX3-FKHR对细胞周期调节蛋白的解除管制在其抑制肌源性分化的能力中的作用。目标2和3中概述的研究将为aRMS细胞不受控制的生长和分化表型提供分子基础。本研究将进一步加深我们对遗传异常与aRMS发病机制的认识；他们还将扩大我们将这些信息用于患者诊断/或预后的能力，并设计治疗试剂，专门中断肿瘤功能而不损害正常细胞功能。

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.