Characterization of the Regulation and Gene Targets of TBX2 in Rhabdomyosarcoma

我的实验室致力于了解导致骨骼转变的分子事件 横纹肌肉瘤（RMS）肿瘤细胞的肌肉前体细胞，希望提出治疗策略， 降低这种儿童癌症的致癌潜力。我们发现TBX 2，一个T-box家族， 成员，是RMS肿瘤细胞中的新癌基因。TBX 2通常在癌细胞中过度表达， 通过抑制p14 ARF和p21来绕过细胞生长控制。细胞周期调节因子p21是 骨骼肌细胞终末分化所需，在RMS细胞中沉默。我们发现 TBX 2抑制RMS细胞中的p21、p14 ARF和肿瘤抑制因子PTEN，并抑制 通过与MYOG和MYOD 1结合的生肌调节因子。因此，TBX 2既促进增殖， 并抑制终末分化。考虑到TBX 2在驱动肿瘤细胞增殖中的至关重要性， RMS，重要的是要了解TBX 2的调节。在其他细胞中，TBX 2受PAX 3调节，PAX 3是一种成对的- 骨骼肌祖细胞所必需的box转录因子。RMS细胞的特征是表达 而更具侵袭性的RMS亚型含有一个易位，将PAX 3与 在一个实施方案中，所述方法包括使用产生PAX 3-FOXO 1融合蛋白的叉头转录因子的反式激活结构域。FGF 在其他系统中，信号传导已被证明可以激活PAX 3和TBX 2，这表明这可能发生在 骨骼肌也是。我们还发现，高度相关的T-Box因子TBX 3抑制TBX 2。 正常骨骼肌和RMS，但TBX 3本身被多梳抑制复合物（PRC 2）沉默， RMS。我们的数据表明，TBX 2是在增殖的细胞中表达的正常调节程序的一部分， 成肌细胞，其在发育期间在分化的细胞中沉默。本提案的目的是 研究RMS细胞中TBX 2的调控和其他基因靶点，这将提供所需的 分子洞察力，以潜在地利用TBX 2的表达或功能治疗。在我们的第一个目标中，我们 将通过确定PAX 3/PAX-FOXO 1和FGF是否能够调节TBX 2的表达来确定调节TBX 2表达的机制。 信号通路激活TBX 2。在第二个目标中，我们将描述新的肿瘤抑制基因 由TBX 2调节，包括TP 53和TCEAL 7。P53是一种众所周知的肿瘤抑制因子， 在RMS中进行了广泛的研究，但我们的数据是第一个在任何系统中暗示TBX 2沉默TP 53的数据。 并表明TP 53在ARMS中是转录沉默的。TCEAL 7在RMS中的功能尚未探索 并且可能代表新的治疗靶点。最后，我们将分析TBX 2在基因组上的结合，以确定所有 RMS中TBX 2结合的基因。总之，这项工作将提供必要的洞察力的作用， 调节RMS细胞中的新癌基因TBX 2，从而为RMS提供新的治疗靶点。 了解基因调控通路的异常对于了解癌症的病理学至关重要 细胞和设计有效的治疗策略以改善横纹肌肉瘤的治疗。

My lab is focused on understanding the molecular events that result in the transition of a skeletal muscle precursor cell to a rhabdomyosarcoma (RMS) tumor cell in hopes to suggest therapeutic strategies to reduce the oncogenic potential of this childhood cancer. We have discovered that TBX2, a T-box family member, is a novel oncogene in RMS tumor cells. TBX2 is often over expressed in cancer cells and is thought to function in bypassing cell growth control by the repression of p14ARF and p21. The cell cycle regulator p21 is required for the terminal differentiation of skeletal muscle cells and is silenced in RMS cells. We have found that TBX2 represses p21, p14ARF and the tumor suppressor PTEN in RMS cells and inhibits the activity of the myogenic regulatory factors through binding to MYOG and MYOD1. Thus, TBX2 both promotes proliferation and represses terminal differentiation. Given the crucial importance of TBX2 in driving tumor cell proliferation in RMS, it is important to understand the regulation of TBX2. In other cells, TBX2 is regulated by PAX3, a paired- box transcription factor essential in skeletal muscle progenitor cells. RMS cells are characterized by expression of PAX3 and the more aggressive subtype of RMS contains a translocation that fuses PAX3 with the transactivation domain of a forkhead transcription factor producing a PAX3-FOXO1 fusion protein. FGF signaling has been shown to activate both PAX3 and TBX2 in other systems, suggesting that this may occur in skeletal muscle as well. We have also found that the highly related T-Box factor, TBX3, represses TBX2 in normal skeletal muscle and RMS, but TBX3 is itself silenced by the polycomb repressive complex (PRC2) in RMS. Our data suggest that TBX2 is part of the normal regulatory program expressed in proliferating myoblasts which is silenced in differentiated cells during development. The goal of this proposal is to investigate the regulation and additional gene targets of TBX2 in RMS cells, which will provide the needed molecular insight to potentially harness the expression or function of TBX2 therapeutically. In our first aim, we will identify mechanisms regulating TBX2 expression by determining if PAX3/PAX-FOXO1 and the FGF signaling pathway activate TBX2. In the second aim, we will characterize novel tumor suppressor genes regulated by TBX2 including TP53 and TCEAL7. P53 is a well known tumor suppressor that has been extensively studied in RMS, but our data are the first to implicate TBX2 in the silencing of TP53 in any system and suggest that TP53 is transcriptionally silenced in ARMS. The function of TCEAL7 is unexplored in RMS and may represent a novel therapeutic target. Finally, we will profile TBX2 binding on the genome to identify all genes bound by TBX2 in RMS. Taken together, this work will provide essential insight into the role and regulation of the novel oncogene TBX2 in RMS cells, thus providing a novel therapeutic target for RMS. Understanding abnormalities in gene regulatory pathways is crucial for understanding the pathology of cancer cells and for designing effective therapeutic strategies to improve treatment of rhabdomyosarcoma.