| Co-Investigator(Kenkyū-buntansha) |
ITOH Kazuyuki Osaka Medical Center for Cancer and Cardiovascular Diseases, Biology, Department Head, 研究所, 部長 (20301806)
YOSHIKAWA Hideki Osaka University Graduate School of Medicine, Orthopedic Surgery, Professor, 大学院・医学研究科, 教授 (60191558)
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| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2004: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
The SSX genes were initially identified as fusion partners to the SYT gene in human synovial sarcomas carrying a recurrent t (X;18)(p11.2;q11.2) chromosomal translocation. Besides adult human testis, SSX genes were expressed at varying frequencies in numbers of malignancies thereby categorized as cancer/testis antigens. Using nucleic acid sequence-based amplification, we have reported that the expression level in the malignant tumors (3.8±1.4 copies/μg of total RNA in log10 order) was significantly higher than that in the benign tumors (2.4±0.5,p<0.0001). In order to examine the biological function of SSX, we firstly made stable transfectants with wild type SSX using human osteosarcoma cell line, Saos-2, which moderately expressed SSX. The expression of SSX was mainly localized in the nucleus with patched pattern. The SSX transfectants promoted colony formation in soft agar and tumor formation in nude mice, but showed little change in growth rate in 2D culture. The transfectants also increased motility, chemotaxis and invasiveness using scratch wound assay and Boyden chamber assay. Since the C-terminal region of SSX strongly bound to Histone in the nucleus, we next made stable transfectants with C-terminal deletion mutants of SSX1,using human fibrosarcoma cell line, HT1080, which highly expressed endogenous SSX1. The transfectants showed marked stress fibers and focal adhesions, decreased motility, chemotaxis and invasiveness in vitro, and attenuated tumorigenesis in nude mice. Furthermore, the lowering of the endogenous expression of SSX1 in HT1080 cells by the treatment with specific siRNA markedly decreased chemotaxis, but did not affect cellular proliferation. Collectively, these data suggested that SSX protein regulated several gene expressions leading to the tumor invasion, and could be a new molecular target under clinical setting.
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