| Co-Investigator(Kenkyū-buntansha) |
FUJI Nobuaki Kyoto Prefectural University of Medicine, Graduate School of Medical Science, Department of Surgery and Oncology of Digestive System, Assistant Professor, 医学研究科, 助手 (90332949)
FUJIWARA Hitoshi Kyoto Prefectural University of Medicine, Graduate School of Medical Science, Department of Surgery and Oncology of Digestive System, Assistant Professor, 医学研究科, 助手 (20332950)
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| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2003: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2002: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2001: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
NK4,an internal fragment of hepatocyte growth factor (HGF) manufactured by elastase. digestion, has been known to exert antitumor effect as a strong angiogenesis inhibitor just like another antiangionesis factor named "Angiostatin". In addition, NK4 strongly inhibits tumor-cell invasion and metastasis with the action of "HGF-antagonist". Based on these facts, we designed a new strategy to suppress the tumor growth in vivo by the expression of "elastase" via its gene transfer, which could induce endogenous NK4 and/or angiostatin in vivo. Unfortunately, we could not overcome the problems such as cellular toxicity and poor efficacy of proteolytic induction of target molecules.
As another project focused on NK4 function, we established a genetically modified mouse colorectal cancer cell line (CT26) to produce high amount of NK4 (CT26-NK4), and investigated antitumor effect of NK4 expression in vitro and in vivo. In in vitro analysis, CT26-NK4 strongly blocked the cell invasion, migration dr
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iven by HGF. In in vivo subcutaneous tumor-inoculation model, NK4 expression significantly suppressed tumor growth in vivo and prolonged animal survival. These therapeutic effects were introduced by the some kinds of biological action of NK4 such as (1)antiangiogenesis, (2)induction of tumor apoptosis, and (3)inhibition of tumor-cell proliferation. Interestingly, we recently found a new mechanism that NK4 expression in tumor cells suppressed HGF production from surrounded stromal cells via inhibition of "HGF-inducers" from tumor cells ((4)break-down of tumor-stromal interactions with HGF). Furthermore, we confirmed a possibility that NK4 could enhance the cell-mediated immunity in vivo, being supported with following findings,1)markedly increased infiltration of T cells was observed in CT26-NK4 tumors,2)IFN-γ production from splenocytes increased in mice bearing CT26-NK4 tumors. In hepatic, pulmonary, and peritoneal metastases models mimicked clinical condition, NK4 expression also significantly suppressed metastases and prolonged survival. To chase the another mechanism, we analyzed the changes of gene expression in CT26-NK4 using DNA microarray, decrease in mRNA expression of some of integrin family was found. In in vitro bioassay, inhibition of CT26-NK4 cell adhesion to extracellular matrix, such as fibronectin and collagen, was confirmed. Less
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