• Tatsuya Ishibe, Tomitaka Nakayama, Takeshi Okamoto, Tomoki Aoyama, Koichi Nishijo, Kotaro Roberts Shibata, Yasuko Shima, Satoshi Nagayama, Toyomasa Katagiri, Yusuke Nakamura, Takashi Nakamura, and Junya Toguchida.
• Institute for Frontier Medical Sciences, Departments of Orthopaedic Surgery, Surgery Surgical Basic Science, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
• Clin Cancer Res. 2005 Apr 1; 11 (7): 2702-12.

PurposeSynovial sarcoma is a soft tissue sarcoma, the growth regulatory mechanisms of which are unknown. We investigated the involvement of fibroblast growth factor (FGF) signals in synovial sarcoma and evaluated the therapeutic effect of inhibiting the FGF signal.Experimental DesignThe expression of 22 FGF and 4 FGF receptor (FGFR) genes in 18 primary tumors and five cell lines of synovial sarcoma were analyzed by reverse transcription-PCR. Effects of recombinant FGF2, FGF8, and FGF18 for the activation of mitogen-activated protein kinase (MAPK) and the growth of synovial sarcoma cell lines were analyzed. Growth inhibitory effects of FGFR inhibitors on synovial sarcoma cell lines were investigated in vitro and in vivo.ResultsSynovial sarcoma cell lines expressed multiple FGF genes especially those expressed in neural tissues, among which FGF8 showed growth stimulatory effects in all synovial sarcoma cell lines. FGF signals in synovial sarcoma induced the phosphorylation of extracellular signal-regulated kinase (ERK1/2) and p38MAPK but not c-Jun NH2-terminal kinase. Disruption of the FGF signaling pathway in synovial sarcoma by specific inhibitors of FGFR caused cell cycle arrest leading to significant growth inhibition both in vitro and in vivo. Growth inhibition by the FGFR inhibitor was associated with a down-regulation of phosphorylated ERK1/2 but not p38MAPK, and an ERK kinase inhibitor also showed growth inhibitory effects for synovial sarcoma, indicating that the growth stimulatory effect of FGF was transmitted through the ERK1/2.ConclusionsFGF signals have an important role in the growth of synovial sarcoma, and inhibitory molecules will be of potential use for molecular target therapy in synovial sarcoma.

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