TGF-β3与熊果酸抑制人结肠癌细胞增殖作用的研究

摘要

目的：研究 TGF-β3与熊果酸（ursolic acid，UA）抑制结肠癌细胞增殖作用的关系及可能的分子机制。方法采用结晶紫染色法和流式细胞术分析不同浓度 UA 对 HCT116细胞增殖的作用。利用 Western blot 和流式细胞术等方法分析 UA 对 HCT116细胞凋亡的影响。通过 RT-PCR 和（或） Western blot 实验分析 UA 在 HCT116细 胞 中 对 TGF-β3、Smad2／3和β-catenin 表达及磷酸化水平的影响。采用 TGF-β3重组腺病毒和特异性抑制剂以及萤光素酶报告质粒分析TGF-β3介导 UA 抑制结肠癌细胞增殖的可能分子机制。结果UA 能明显抑制 HCT116细胞增殖，诱导 G1期阻滞，并促进其凋亡。UA 能明显降低 TGF-β3的 mRNA 和蛋白表达水平；UA 对 Smad2／3的总蛋白水平无明显影响，但能明显降低 Smad2／3的磷酸化水平；外源性过表达 TGF-β3可部分逆转 UA 对 HCT116细胞增殖的抑制作用，TGF-β3特异性抑制剂则增强 UA 对 HCT116细胞增殖的抑制作用；UA 降低β-catenin 蛋白水平，并明显抑制 Wnt／β-catenin 信号转导；外源性过表达 TGF-β3促进β-catenin 蛋白表达，并部分逆转UA 对β-catenin 蛋白表达的抑制效应；TGF-β3特异性抑制剂增强 UA 对β-catenin 蛋白表达的抑制作用。结论UA 能抑制结肠癌细胞 HCT116增殖并诱导凋亡，其作用可能是通过下调 TGF-β3表达，进而抑制 Wnt／β-catenin 信号转导。%Aim To investigate the role of TGF-β3 in the anti-proliferation effect of ursolic acid(UA)in co-lon cancer cells and the possible molecular mechanism underlying this effect.Methods We introduced crys-tal violet staining,flow cytometry and Western blot as-say to determine the effect of UA on proliferation and apoptosis in HCT1 1 6 cells.The levels of TGF-β3, Smad2 /3 and β-catenin in HCT1 1 6 cell were evaluated by RT-PCR and Western blot.Finally,TGF-β3 inhibi-tor and recombinant adenovirus,and luciferase reporter assay were used to analyze the possible mechanism through which TGF-β3 mediated the anti-cancer effect of UA in HCT1 1 6 cells.Results UA inhibited the proliferation and induced apoptosis apparently in HCT1 1 6 cells.UA down-regulated TGF-β3 both in mRNA and in protein level.Meanwhile,UA decreased the phosphorylation of Smad2 /3 concentration depend-ently,although no significant effect was found on the total protein level of Smad2 /3 in HCT1 1 6 cells.Over-expression of TGF-β3 attenuated the inhibitory effect of UA on the proliferation of HCT1 1 6 cells,while the TGF-β3 inhibitor potentiated this effect. UA sup-pressed the transconduction of Wnt/β-catenin signaling in HCT1 1 6 cells through decreasing the level of β-catenin.Exogenous expression of TGF-β3 increased the level of β-catenin and partly reversed the UA-in-duced decrease of β-catenin.However,TGF-β3 inhib-itor potentiated the inhibitory effect of UA on β-catenin in HCT1 1 6 cells.Conclusion The anti-proliferation activity of UA in colon cancer may be partly mediated through down-regulating TGF-β3 to suppress Wnt/β-catenin signaling at least.