ELUDICATION OF ASSOCIATION AND SIGNAL TRANSDUCTION PATHWAY BETWEEN BETA-KATENIN AND GROWTH FACTOR RECEPTOR AT THE CANCER INVASION

1)用表皮生长因子（EGF）和转化生长因子α（TGF α）等生长因子下调钙粘蛋白介导的细胞粘附和β-连环蛋白酪氨酸磷酸化。证实β-连环蛋白的酪氨酸磷酸化存在于人结肠癌组织中的侵袭性前沿，其中癌细胞从单个细胞中的癌巢中解离。2）使用β-连环蛋白的缺失突变体证实β-连环蛋白和c-erB-2之间的物理关联。位于β-catenin中心的第12个Armadillo重复序列与EGF受体和c-erB-2等生长因子受体结合。EGF和TGF α刺激可引起第12个犰狳重复序列的酪氨酸磷酸化。这些结果表明生长因子受体和β-catenin之间存在信号转导途径。3）利用酪氨酸磷酸化肽制备了识别酪氨酸磷酸化β-catenin第12个犰狳重复序列的单克隆抗体。该抗体可通过生长因子受体激活β-catenin并刺激α-catenin和β-catenin解离来分析钙粘蛋白介导的细胞粘附系统功能障碍的分子机制。4）人结肠癌组织中β-catenin的免疫组化染色显示，B-catenin的酪氨酸磷酸化水平明显高于正常人结肠癌组织。在第12个犰狳重复序列处的连环蛋白特异性地出现在癌细胞从癌巢分离的侵入前沿。这些结果证实了生长因子受体和β-catenin之间的信号转导通路在人类肿瘤组织中的存在以及这种信号转导在肿瘤侵袭和转移中的重要性。

1) Down regulation of the cadherin-mediated cell adhesion and tyrosine phosphoryaltion of β-catenin was stimulated by growth factors as epidermal growth factor (EGF) and transforming growth factor α (TGF α) using human cancer cell lines. Tyrosine phosphrylation of β-catenin was confirmed to be present in human colon cancer tissue at the invasive front where cancer cells dissociate from cancer nests in a single cells.2) Physical association between β-catenin and c-erB-2 was confirmed using deletion mutants of β-catenin. The 12th armadillo repeat which locates at the center of β-catenin was found to bind the growth factor receptors as EGF receptor and c-erB-2. Tyrosine phosphoryaltion of the 12th armadillo repeat was occurred by EGF and TGF α stimulation. These results indicate the presence of signal transduction pathway between growth factor receptor and β-catenin.3) A monoclonal antibody which recognizes tyrosine phosphorylated 12th armadillo repeat of β-catenin was generated using tyrosine phosphoryalted peptides. This antibody allows us to analyze the molecular mechanism of dysfunction of cadherin-mediated cell adhesion system through the growth factor receptor that activation of growth factor receptor phosphoryaltes β-catenin and stimulates dissociation between α and β-catenin.4) Immunohistochemical staining of β-catenin in human colon cancer tissues showed that tyrosine phosphorylation of b-catenin at the 12th armadillo repeat specifically occurs at the invasive front where cancer cells dissociate from cancer nests. These results confirm the presence of signal transduction pathway between growth factor receptor and β-catenin in human cancer tissues and importance of this signal transduction in the cancer invasion and metastasis.