Notch 家族四个蛋白质在人胰腺癌细胞 HPAC 中对 YY1 和 EGFR水平的影响

Notch信号通路是肿瘤形成过程中一种重要的信号通路，其中心分子为Notch受体. Notch受体为细胞膜上的单次跨膜蛋白，介导细胞间信号转导，哺乳动物细胞内包括Notch1、Notch2、Notch3和Notch4的4个成员. Notch家族4个蛋白质在结构和功能上存在差异.前期研究显示，Notch1信号通路与转录因子YY1（YING-YANG 1）、表皮生长因子受体（EGFR）间存在调控作用. 本研究在人胰腺癌细胞HPAC中，采用RNA干扰技术，分别降低细胞中Notch家族4个蛋白质的表达，检测YY1和EGFR在mRNA和蛋白质水平上的表达；并构建相应的激活形式的Notch受体--Notch胞内结构域（Notch intracellular domain，NICD）真核表达质粒，在HPAC细胞中分别过表达4种NICD，检测其对YY1和EGFR表达水平的影响. 结果显示，降低细胞中Notch1或Notch3的表达,均使HPAC细胞中EGFR mRNA和蛋白质水平升高（P<0.05），而降低Notch2和Notch4后,EGFR mRNA和蛋白质水平没有改变（P>0.05）.分别降低4个Notch的表达，对YY1的蛋白质和mRNA表达水平均没有改变（P>0.05）. 在HPAC细胞中过表达N1ICD和N3ICD后，YY1和EGFR的蛋白质水平降低（P<0.05），而过表达N2ICD和N4ICD后，YY1和EGFR蛋白质水平没有改变（P>0.05）.分别过表达4种NICD均没有改变YY1和EGFR的mRNA表达水平（P>0.05）.初步得出结论是,在HPAC细胞中，Notch信号通路经Notch1和Notch3影响EGFR的表达. Notch1和Notch3对EGFR的表达可能具有负调控作用. 在Notch1和Notch3过度激活时，这种调控作用通过YY1介导. 本文可为深入研究Notch信号通路对胰腺癌发生发展的作用机制提供有意义的参考.

Effects of Notch Family Proteins on the Expression of YY1 and EGFR in Pancreatic Cancer HPAC Cells

Notch signal pathway plays a vital role in tumorigenesis of many cancers. The Notch family contains Notch1, Notch2, Notch3 and Notch4 protein receptors. They are different from one another in structure and function. Previous studies have showed that Notch1 interacts with YY1(YING-YANG 1) and EGFR(epidermal growth factor receptor). In the present study, we knocked down the four Notch receptors respectively and then observed the expression levels of YY1 and EGFR. The plasmids of four Notch intracellular domain (NICDs) were constructed, and then they were transfected into HPAC cells to investigate the effects of overexpression of NICD on the YY1 and EGFR expression. The results showed that knocking down of Notch1 or Notch3 increased both mRNA and protein level of EGFR(P<0.05), while knocking down the Notch2 or Notch4 did not (P>0.05). Knocking down none of the Notchs changed the YY1 level. Overexpression of N1ICD and N3ICD reduced YY1 and EGFR protein expressions (P<0.05), but overexpression of N2ICD and N4ICD did not. Overexpression of none of NICDs changes the YY1 and EGFR mRNA level. We concluded that EGFR is regulated by Notch1 and Notch3, but not Notch2 and Notch4 at protein level in HPAC cells. When Notch1 or Notch3 is over activated, they might regulate EGFR via YY1.