Targeting FGFR4, RAS, and PAX3-FOXO1 gene in Rhabdomyosarcoma

横纹肌肉瘤(RMS)是一种罕见的儿童软组织肉瘤，通常分为泡状(ARM)或胚胎型组织学亚型。ARMS在老年患者中观察到，并与染色体易位有关，产生了涉及13号染色体上的FOXO1A和PAX基因家族成员的融合基因。胚胎性RMS的特点是确诊年龄较早，杂合性丧失和基因组印迹模式改变1。所有RMS组织学亚型长期存活率低的一个重要决定因素是是否存在转移性疾病。导致肿瘤进展和转移性疾病的因素还不是很清楚。基因表达模式的分析提高了肿瘤识别的准确性和肉瘤生物学的进展，特别是对转移调控因子的可能机制有了新的见解。我们和其他人已经报道了成纤维细胞生长因子受体(FGFR)基因家族的受体酪氨酸激酶(RTK)成员FGFR4在RMS中高表达，并且mRNA的表达与蛋白质水平相关。这些观察表明，FGFR4可能是一种肿瘤特异性诊断标志物和/或肿瘤生物学决定因素。在其他人类癌症中，常见的编码区(FGFR4 G388R)多态性的存在与肉瘤、结肠癌或乳腺癌患者肿瘤细胞运动性增强和预后相关。FGFR基因在癌症生物学中具有重要的意义，因为它们调控着细胞的生存、运动、发育和血管生成等重要过程。对FGFR编码区的比较表明，FGFR1、FGFR2、FGFR3和FGFR4具有高度的氨基酸保守性。这些副猪的胚系突变已被描述为几种罕见的、高度穿透性的麦德林疾病，包括Crouzon综合征、Pfeiffer综合征和软骨发育不良。在多形性胶质母细胞瘤、乳腺癌、肺癌和子宫内膜癌中，FGFR TK结构域中的同源同源基因的体细胞突变也被观察到。这些观察使我们假设，FGFR4的激活，可能是通过体细胞突变事件，可能是RMS、肉瘤或其他癌症的致癌过程的关键。此外，FGFR4的过度激活可能与晚期疾病和不良预后有关。我们现在已经发表了一篇手稿，证实激活FGFR4突变发生在7.5%或RMS，并且过度表达与更具侵袭性的表型相关。我们团队最近还对横纹肌肉瘤基因组进行了全面的基因组分析，发现在融合阴性的横纹肌肉瘤中，50%的RAS途径基因发生了突变。最后，我们致力于鉴定PAX3/7-FOXO1融合癌基因的分子、表观和功能效应，并开发新的策略来靶向融合阳性横纹肌肉瘤的表观基因组，包括天然产物筛选。因此，我们正在开发针对横纹肌肉瘤的FGFR4、RAS和融合基因的新疗法。

Rhabdomyosarcoma (RMS) is a rare pediatric soft tissue sarcoma typically classified as either alveolar (ARMS) or embryonal histological subtypes. ARMS is observed in older patients and is associated with a chromosomal translocation creating a fusion gene involving FOXO1A on chromosome 13 and members of the PAX gene family. Embryonal RMS is characterized by a younger age at diagnosis, loss of heterozygosity and altered patterns of genomic imprinting1. An important determinant of poor long term survival for all RMS histological subtypes is the presence of metastatic disease. Factors contributing to tumor progression and metastatic disease are not well understood. Analysis of gene expression patterns have led to improved accuracy of tumor identification and advances in sarcoma biology, particularly new insights into possible mechanisms of metastatic regulators. We and others have previously reported that FGFR4, a receptor tyrosine kinase (RTK) member of the fibroblast growth factor receptor (FGFR) gene family, is highly expressed in RMS and mRNA expression correlates with protein levels. These observations suggest that FGFR4 could be a tumor specific diagnostic marker and/or a determinant of tumor biology. In other human cancers, the presence of a common polymorphism in the coding region (FGFR4 G388R) is associated with increased tumor cell motility and prognosis in patients with sarcomas, colon or breast cancer. The FGFR genes are of great interest in cancer biology because they regulate essential processes including cellular survival, motility, development, and angiogenesis. Comparison of the FGFR coding regions indicates segments of high amino acid conservation in FGFR1, FGFR2, FGFR3, and FGFR4. Germline mutations in these paralogs have been described for several rare, highly penetrant Medelian disorders including Crouzon syndrome, Pfeiffer syndrome, and hypochondroplasia. Somatic mutations at the same sites of paralologs have been observed within the FGFR TK domains in glioblastoma multiforme, breast cancer, lung cancer and endometrial carcinoma. These observations lead us to hypothesize that FGFR4 activation, perhaps by somatic mutational events, could be critical to the oncogenic process in RMS, sarcomas, or other cancers. Furthermore, FGFR4 over activity could be associated with advanced stage disease and poor outcome. We have now published a manuscript that confirms that activating FGFR4 mutations occur in 7.5% or RMS and that over expression is associated with a more aggressive phenotype. Our group has also recently performed a comprehensive genomic analysis of the rhabdomyosarcoma genome and found that RAS pathway genes are mutated in 50% of fusion negative rhabdomyosarcoma. Finally we are dedicating considerable efforts in characterizing the molecular, epigentic and functional effects of the PAX3/7- FOXO1 fusion oncogene, and developing novel strategies to target the epigenome of fusion positive rhabdomyosarcoma, including a natural product screen. We are therefore developing new therapies targeting FGFR4, RAS and the fusion gene in rhabdomyosarcoma.