| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2004: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Research Abstract |
Background and Aim : RUNK3 is a candidate tumor-suppressor gene localized in Ip36, a region commonly inactivated by deletion and methylation in various human tumors. The aim of this study was to elucidate the role of RUNX3 in TGF-β signaling in a biliary tract cancer cell line.
Materials and Methods : We transfected a biliary tract cancer cell line, Mz-ChA-2 cells, which do not express RUNX3 but have intact TGF-β receptor II and SMAD4, with the RUNX3 expression plasmid pcDNA3.1/RUNX3 or with the vector pcDNA3.1 as a control. The responses of the RUNK3-transfected cells and control cells (mock) to TGF-β stimulation were compared.
Results : Four Mz-ChA-2/RUNK3 clones and one control clone were obtained. Although TGF-β1 only slightly inhibited growth of the control cells, growth inhibition and TGF-β-dependent G1 arrest were significantly enhanced in the RUNK3-transfected clones. None of the clones, however, exhibited apoptosis. The slightly increased TGF-β1-induced p21 expression in the control clone, which was strongly enhanced in the RUAX3-transfected clones, was accompanied by augmented decreases in the expression of cyclins D1 and E. When RUNX3 siRNA was added, TGF-β-dependent induction of p21 was reduced in the RUNX3-transfected clones. Moreover, TGF-β-dependent FOXO3A induction was significantly enhanced in proportion to the expression levels of RUNX3 in the RUNX3-transfected clones. Xenografts of the clones in nude mice demonstrated that tumorigenicity was significantly decreased in the RUNK3-transfected clones in inverse proportion to the expression levels of RUNX3.
Conclusion : Restoration of RUNX3 expression enhanced TGF-β-dependent G1 arrest in association with up-regulation of p21 in a biliary tract cancer cell line. Thus, RUNX3 appears to be involved in TGF-β-induced expression of p21 and the resulting induction of TGF-β-dependent G1 arrest.
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