Isolation of model mouse generating Ewing sarcoma and analysis of the mechanism of sarcoma-genesis

本研究的目的是通过在肿瘤组织中表达肿瘤特异性EWS-FLI融合癌基因，分离出尤文肉瘤和外周神经外胚层肿瘤（PNET）模型小鼠，并鉴定EWS-FLI融合癌基因产物肿瘤特异性转录因子调控的基因。分离到两个EWS-FLI转基因小鼠品系，发现它们具有繁殖能力，并且能够生长，没有任何明显的失败。为了允许通过Cre-loxP技术在体内进行DNA重组，将EWS-FLI小鼠与经操作以在神经嵴来源的细胞中表达DNA重组酶的Cre转基因小鼠杂交。由于携带重组DNA的小鼠产生的频率较低，我们目前无法确定是否产生肿瘤。通过培育不同品系的EWS-FLI小鼠品系，将提高重组小鼠的出生率。另一方面，我们发现了几个基因的表达与肉瘤特异性融合癌基因，而不是与其正常对应的改变。一种是与肿瘤进展相关的细胞外基质组分腱生蛋白-C。另一个是转录因子Id 2。研究了它们在尤文肉瘤中的生物学意义（Genes Chromosomes & Cancer 2003 ; Oncogene 2002）。融合癌基因上调c-myc表达，下调TGF-β 2和Smad 3表达。这些可能与尤文肉瘤细胞的高增殖潜力有关。为了阐明肉瘤发生的机制，需要进一步分析靶基因。

The purposes of this study is to isolate a model mouse generating Ewing sarcoma and peripheral neuroectodermal tumor (PNET) by expressing the sarcoma-specific EWS-FLI fusion oncogene in the mouse tissue limited for generation of sarcoma, and to identify the genes regulated by tumor-specific transcription factor, the product of EWS-FLI fusion oncogene. Two EWS-FLI transgenic mouse strains with fusion oncogene were isolated and found to be reproductive and able to grow up without any significant failures. To allow DNA recombination in vivo by the Cre-loxP techniques, EWS-FLI mice were crossbred with the Cre transgenic mice manipulated to express the DNA recombinase in neural crest-derived cells. Since mice with the recombined DNA yielded at lower frequency, we were currently unable to determine whether tumor is generated or not. By breeding a different line of EWS-FLI mouse strains, the birth of recombinant mice will be improved. On the other hand, we found several genes whose expressions were altered with the sarcoma-specific fusion oncogene but not with its normal counterpart. One is the extra-cellular matrix component Tenascin-C associated with tumor progression. The other is transcription factor Id2. Their biological significance in Ewing sarcoma was investigated (Genes Chromosomes & Cancer 2003 ; Oncogene 2002). Also we found up-regulation of c-myc and down-regulation of TGF-beta2 and Smad3 expressions by fusion oncogene. These may be associated with higher proliferating potential of Ewing sarcoma cells. To elucidate the mechanism of sarcoma-genesis, further analysis of target genes will be required.