Genomic EWS-FLI1 Fusion Sequences in Ewing Sarcoma Resemble Breakpoint Characteristics of Immature Lymphoid Malignancies

Chromosomal translocations between the EWS gene and members of the ETS gene family are characteristic molecular features of the Ewing sarcoma. The most common translocation t(11;22)(q24;q12) fuses the EWS gene to FLI1, and is present in 85–90% of Ewing sarcomas. In the present study, a specifically designed multiplex long-range PCR assay was applied to amplify genomic EWS-FLI1 fusion sites from as little as 100 ng template DNA. Characterization of the EWS-FLI1 fusion sites of 42 pediatric and young adult Ewing sarcoma patients and seven cell lines revealed a clustering in the 5′ region of the EWS-breakpoint cluster region (BCR), in contrast to random distribution of breakpoints in the FLI1-BCR. No association of breakpoints with various recombination-inducing sequence motifs was identified. The occurrence of small deletions and duplications at the genomic junction is characteristic of involvement of the non-homologous end-joining (NHEJ) repair system, similar to findings at chromosomal breakpoints in pediatric leukemia and lymphoma.EWS基因与ETS基因家族成员之间的染色体易位（Chromosomal translocations）是尤文肉瘤（Ewing sarcoma）的特征性分子标志。最常见的易位t(11;22)(q24;q12)可将EWS基因与FLI1基因融合，在85%~90%的尤文肉瘤病例中均可检测到该易位。本研究采用定制设计的多重长距离聚合酶链式反应（multiplex long-range PCR）检测法，仅需低至100 ng的模板DNA即可扩增得到基因组EWS-FLI1融合位点。对42例儿科及青年成人尤文肉瘤患者与7株细胞系的EWS-FLI1融合位点进行特征分析后发现，EWS断点簇区（BCR）内的断点呈现5'端区域聚集的分布特征，而FLI1断点簇区（FLI1-BCR）内的断点则呈随机分布。未发现断点与各类重组诱导序列基序存在关联。基因组连接区域出现的小片段缺失与重复现象，提示非同源末端连接（NHEJ）修复系统参与了该融合过程，这与儿童白血病及淋巴瘤中染色体断点的相关研究结果相符。