Molecular Pathogenic Mechanism of Rhabdomyosarcoma

为了了解PAX3-FKHR在RMS发生发展中的分子致病机制，我们利用CHIP-SEQ技术在RMS细胞中定位了与1072个基因相关的PAX3-FKHR基因组结合位点。I.数据显示，PAX3-FKHR在MYF5、FGFR4的增强子以及先前被证明位于PAX3调控下游的MYOD核心增强子上与PAX3结合到相同的位点。此外，我们的数据集具有快速识别和验证MYOD和FGFR4增强子活性所需的新的和特定序列的精度。全基因组分析表明，绝大多数PAX3-FKHR位点位于转录起始点的远端；2)保守；3)富含PAX3基序；4)在PAX3-FKHR阳性的RMS细胞和肿瘤中与过度表达的基因密切相关。在我们的数据集中，几乎没有证据表明PAX3-FKHR与启动子结合。在一个例子中，我们的数据为MET建立了两个内含子增强子元件，而不是在前面描述的启动子上。全基因组分析进一步表明，这些结合位点上的PAX3和E-box基序之间存在很强的关联，这表明许多靶基因存在共同的共同调节。PAX3-FKHR结合位点图为PAX3和PAX3-FKHR的功能提供了新的联系，为RMS的治疗提供了新的靶点。我们的研究确定了对肢体发生的不同方面至关重要的基因，作为PAX3-FKHR的直接靶点。此外，我们将IGF1R确定为PAX3-FKHR的直接靶点。在一些携带PAX3-FKHR的RMS细胞中，IGF1R的生存依赖使其成为治疗这种癌症的理想靶点。

To understand the molecular pathogenic mechanism of PAX3-FKHR in the development of RMS, we used ChIP-seq to map PAX3-FKHR genomic binding sites associated with 1072 genes in RMS cells. I. The data shows that PAX3-FKHR binds to the same sites as PAX3 at enhancers for MYF5, FGFR4, as well as the MYOD core enhancer previously shown to be downstream of PAX3 regulation. Moreover, our dataset has the precision for a rapid identification and validation of novel and specific sequences required for the enhancer activity for MYOD and FGFR4. II. The genome wide analysis reveals that the vast majority of PAX3-FKHR sites are: 1) distal to transcription start sites; 2) conserved; 3) enriched for PAX3 motifs; 4) strongly associated with genes over-expressed in PAX3-FKHR positive RMS cells and tumors. There is little evidence in our dataset for PAX3-FKHR binding at the promoters. In one instance, our data establishes two intronic enhancer elements for MET, rather than at the previously described promoter. The genome-wide analysis further illustrates a strong association between PAX3 and E-box motifs in these binding sites, suggestive of a common co-regulation for many target genes. III. The map of PAX3-FKHR binding sites provides new links for PAX3 and PAX3-FKHR functions and new targets for RMS therapy. Our study identifies genes that are critically important for different aspects of limb-genesis, as direct PAX3-FKHR targets. Further, we identify IGF1R as a direct target for PAX3-FKHR. The dependence on IGF1R for survival in some RMS cells with PAX3-FKHR makes it an ideal therapeutic target for this cancer.