Basic study for gene therapy of human liver cancer in terms of regulating signal trnasduction pathway

本研究旨在阐明肝癌的信号转导治疗。在第一个实验中，我们分析了人肝癌组织中丝裂原活化蛋白激酶（MAPK）级联反应的激活，MAPK级联反应是一种参与正常细胞生长的细胞内信号传导系统。MAPK活性在癌组织中比在癌旁组织中更增强。而Raf-1激酶，它是MAPK级联的上游组分之一，在癌组织和非癌组织之间的活性没有显着差异，而MEK激酶，它可以激活MAPK，在癌组织中的活性增加。这些发现表明，MAPK在癌组织中以不同于肝脏正常细胞生长的方式被组成性激活。先前已报道MAPK诱导转录因子的基因表达，随后诱导细胞周期相关基因的基因表达。在人肝癌中，c-fos和c-jun的表达与肝癌的发生、发展密切相关。 ...更多信息 本实验旨在探讨肝癌组织中MAPK级联反应的信号转导通路中的哪些成分可能是导致MAPK级联反应激活的原因。本文重点研究了胰岛素受体底物1（insulin receptor substrate-1，IRS-1）的作用。IRS-1是一种被胰岛素或IGF-1激活的信号转导分子，可激活MAPK级联反应。IRS-1在肝癌中过度表达和活化的观察使我们构建稳定的转染子以观察IRS-1的转化能力。稳定的转染子表现出MAPK活化，导致裸鼠以及软琼脂中的肿瘤形成。这些结果表明IRS-1可能通过激活MAPK级联反应促进肝癌细胞的生长。总之，本研究提示通过抑制信号传导通路，进行信号传导治疗以防止肝癌细胞生长的可能性。少

The present study was aimed to elucidate the signal transduction therapy for human liver cancer. For the first experiment, we analyzed the activation of mitogen-activated protein kinase (MAPK) cascade, an intracellular signal trnasduction system involved in normal cell growth, in human liver cancerous tissues. MAPK activity was more enhanced in cancerous tissues than in adjacent non-cancerous tissues. While Raf-1 kinase, which is one of the upstream components of MAPK cascade, exhibited no significant difference in activity between cancerous and non-cancerous tissues, MEK kinase, which can activate MAPK,was increased in activity in cancerous tissues. These findings indicate that MAPK is consititutively activated in cancerous tissues in a different fashion from normal cell growth of the liver. MAPK has been previously reported to induce gene expression of transcriptional factor, followed by gene expression of the cell cycle-related genes. In human liver cancer, c-fos and c-jun expressio … More n were enhanced, accompanied by increase in cyclin D1 gene expression.Next experiment was attempted to examine which component (s) of signal transduction pathway may account for the activation of MAPK cascade in the cancerous tissues of the liver. We focus on the role of IRS-1 (insulin receptor substrate-1), a signal transducing molecule which is activated by insulin or IGF-1 and can activate MAPK cascade. The observation that IRS-1 was over-expressed and activated in liver cancers led us to construct the stable transfectant to see transformation capability of IRS-1. Stable transfectant exhibited MAPK activation, leading to tumor formation in nude mice as well as soft agar. These findings indicate that IRS-1 may contribute to liver cancer cell growth in term of activation of MAPK cascade. In conclusion, the present study suggests the possibility of signal trnasduction therapy for the prevention of cancerous cell growth of the liver by means of the inhibition of signal trnasdcution pathways. Less