实验性大鼠肝脏癌变过程中转化生长因子-β1/Smads信号通路系列变化的研究

Changes in TGF-β1/Smads signaling pathway in rats with chemical hepatocarcinogenesis

目的本研究通过大鼠肝癌模型的建立,观察正常肝脏发展成肝癌过程中转化生长因子β1(TGF-β1)/Smads信号通路变化,对肝癌形成的机制进行一定的探索。方法用二乙基亚硝胺溶液(DENA)诱导大鼠肝癌模型,免疫组化的方法检测不同时期TGF-β1、磷酸化Smad2、Smad4和Smad7蛋白的表达,半定量RT-PCR检测Smad4 mRNA的表达。结果正常细胞时TGF-β1和Smad4很少表达,随着肝硬化的发展,两者的表达均明显增强,但DENA处理22周后的肝组织中Smad4表达明显下降,肝癌降低更显著;正常细胞可有较多磷酸化Smad2的表达,DENA处理8周时表达明显减少,后逐渐增多,DENA处理16周、22周时磷酸化Smad2的表达接近正常水平,但肿瘤内表达明显减少,并显著低于DENA处理8周时;正常肝细胞可见Smad7的表达,随着肝硬化的发展而加重,DENA处理22周时的肝组织达到最高,肝癌的表达仅略低于22周时的肝组织。结论肝癌的发生机制非常复杂,大鼠肝硬化晚期Smad4表达的减少、甚至消失,TGF-β1和Smad7的过高表达,磷酸化Smad2的减少,在大鼠肝癌的发生、发展中都起着非常重要的作用。

Objective To investigate the changes in transforming growth factor beta 1 （TGF-β1）/Smads signaling pathway in rats with chemical hepatocarcinogenesis. Methods Fresh diethylnitrosamine （DENA） solution was administered in SD rats to induce hepatocellular carcinoma （HCC）. The protein expressions of TGF-β1, phosphorylated Smad2, Smad4 and Smad7 were detected in these rats with immunohistochemistry, and the mRNA expression of Smad4 was evaluated with RT-PCR. Results Cirrhotic nodules occurred in the rats 8 weeks after DENA treatment, and HCC nodules were found 16 weeks after the treatment. In the normal liver tissue, very low levels of TGF-β1 and Smad4 expressions, low Smad7 expression and high phosphorylated Smad2 expression were detected. The development of liver cirrhosis was accompanied by increased expressions ofTGF-β1, Smad4 and Smad7 but at 8 weeks after DENA treatment, the expression ofphosphorylated Smad2 was significantly decreased, followed then by gradual increment till nearly the normal level. Twenty-two weeks after DENA treatment, Smad4 expression in liver tissue decreased markedly as compared with the levels at 8 and 16 weeks. The expressions of Smad4 and phosphorylated Smad2 in the HCC tissue was significantly lower than those in normal liver tissue. Conclusion Hepatocarcinogenesis involves very complex mechanisms, can can be related partially to the decreased Smad4 and phosphorylated Smad2 expression and TGF-β1 and Smad7 overexpression in advanced stage of liver cirrhosis.