title: Synthetic siRNA targeting the breakpoint of EWS/Fli-1 inhibits growth of Ewing sarcoma xenografts in a mouse model.
abstract: The EWS/Fli-1 fusion gene, a product of the translocation t(11;22, q24;q12), is detected in 85% of Ewing sarcomas and primitive neuroectodermal tumors. It is thought to be a transcriptional activator that plays a significant role in tumorigenesis. In this study, we developed a novel EWS/Fli-1 blockade system using RNA interference and tested its application for inhibiting the proliferation of Ewing sarcoma cells in vitro and the treatment of mouse tumor xenografts in vivo. We designed and synthesized a small interfering RNA (siRNA) possessing an aromatic compound at the 3'-end targeting the breakpoint of EWS/Fli-1. As this sequence is present only in tumor cells, it is a potentially relevant target. We found that the siRNA targeting EWS/Fli-1 significantly suppressed the expression of EWS/Fli-1 protein sequence specifically and also reduced the expression of c-Myc protein in Ewing sarcoma cells. We further demonstrated that inhibition of EWS/Fli-1 expression efficiently inhibited the proliferation of the transfected cells but did not induce apoptotic cell death. In addition, the siRNA possessing the aromatic compound at the 3'-end was more resistant to nucleolytic degradation than the unmodified siRNA. Administration of the siRNA with atelocollagen significantly inhibited the tumor growth of TC-135, a Ewing sarcoma cell line, which had been subcutaneously xenografted into mice. Moreover, modification of the 3'-end with an aromatic compound improved its efficiency in vivo. Our data suggest that specific downregulation of EWS/Fli-1 by RNA interference is a possible approach for the treatment of Ewing sarcoma.
authors.affiliation: Department of Orthopaedic Surgery, Gifu University Graduate School of Medicine, Gifu, Japan.
authors.forename: Iori
authors.initials: I
authors.lastname: Takigami
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Ohno
authors.forename: Yukio
authors.initials: Y
authors.lastname: Kitade
authors.forename: Akira
authors.initials: A
authors.lastname: Hara
authors.forename: Akihito
authors.initials: A
authors.lastname: Nagano
authors.forename: Gou
authors.initials: G
authors.lastname: Kawai
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Saitou
authors.forename: Aya
authors.initials: A
authors.lastname: Matsuhashi
authors.forename: Kazunari
authors.initials: K
authors.lastname: Yamada
authors.forename: Katsuji
authors.initials: K
authors.lastname: Shimizu
mesh_terms: D000818:Animals; D017209:Apoptosis; D001483:Base Sequence; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D056905:Chromosome Breakpoints; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D015394:Molecular Structure; D015514:Oncogene Proteins, Fusion / Q000235:genetics* / Q000378:metabolism; D051789:Proto-Oncogene Protein c-fli-1 / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000138:chemical synthesis / Q000235:genetics*; D034802:RNA-Binding Protein EWS; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012512:Sarcoma, Ewing / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D047368:Tumor Burden / Q000235:genetics; D023041:Xenograft Model Antitumor Assays / Q000379:methods*
chemical_list: C106031:EWS-FLI fusion protein; D015514:Oncogene Proteins, Fusion; D051789:Proto-Oncogene Protein c-fli-1; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D034802:RNA-Binding Protein EWS