Tamagawa Yuji, Ishimura Norihisa, Uno Goichi, Aimi Masahito, Oshima Naoki, Yuki Takafumi, Sato Shuichi, Ishihara Shunji, Kinoshita Yoshikazu
Department of Internal Medicine II, Shimane University Faculty of Medicine, Izumo, Shimane, Japan.
Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA.
Lab Invest. 2016 Mar;96(3):325-37. doi: 10.1038/labinvest.2015.137. Epub 2015 Nov 16.
Crosstalk between the Notch signaling pathway and Caudal-related homeobox 2 (Cdx2) has important roles in the development of Barrett's esophagus (BE). We investigated the expression and function of the Notch signaling ligand Delta-like 1 (Dll1) during the development of BE. We determined the expression levels of Dll1 and intracellular signaling molecules related to Notch signaling ((Notch1, Hairy/enhancer of split 1 (Hes1), and Atonal homolog 1 (ATOH1)) in human esophageal squamous and Barrett's epithelium samples. Next, those expression levels in esophageal squamous cells (Het-1A) and Barrett's esophageal cells (CP-A and BAR-T) following stimulation with either bile acids or gamma-secretase inhibitor were investigated. Finally, changes in those expression levels following transfection of a Cdx2 or Dll1 expression vector into Het-1A cells were examined. In addition, changes in those expression levels following knockdown of Cdx2 or Dll1 in CP-A cells were also examined. Dll1 was found to be upregulated and localized in the cell membrane and cytoplasm in BE. Bile acids enhanced cytoplasmic expression of Dll1 in CP-A cells, while cleaved Notch1 expression did not change, suggesting lack of a Dll1 agonistic effect on Notch signaling. Cells transfected with Cdx2 revealed significantly enhanced Dll1, while forced expression of Dll1 enhanced ATOH1, Cdx2, and MUC2 expression levels. Nevertheless, enhanced Dll1 did not induce Hes1 expression, suggesting that Dll1 may primarily function as an intracellular signaling molecule and not a Notch agonistic ligand in the canonical pathway. In addition, knockdown of Cdx2 completely abrogated any increase in Dll1 expression upon treatment with bile acids. Our results revealed a novel function of Dll1: facilitation of intestinal metaplasia in conjunction with Cdx2 expression. Furthermore, they suggest that intracellular induction of Dll1 expression in esophageal epithelial cells due to Cdx2 induction in response to bile acids has important roles in BE development.
Notch信号通路与尾型相关同源框2（Cdx2）之间的串扰在巴雷特食管（BE）的发展中具有重要作用。我们研究了BE发展过程中Notch信号配体Delta样1（Dll1）的表达和功能。我们测定了人食管鳞状上皮和巴雷特上皮样本中Dll1以及与Notch信号相关的细胞内信号分子（Notch1、毛状/分裂增强子1（Hes1）和无调性同源物1（ATOH1））的表达水平。接下来，研究了用胆汁酸或γ-分泌酶抑制剂刺激后人食管鳞状细胞（Het-1A）和巴雷特食管细胞（CP-A和BAR-T）中的这些表达水平。最后，检测了将Cdx2或Dll1表达载体转染到Het-1A细胞后这些表达水平的变化。此外，还检测了CP-A细胞中Cdx2或Dll1敲低后这些表达水平的变化。发现Dll1在BE中上调并定位于细胞膜和细胞质中。胆汁酸增强了CP-A细胞中Dll1的细胞质表达，而切割后的Notch1表达未改变，这表明Dll1对Notch信号缺乏激动作用。转染Cdx2的细胞显示Dll1显著增强，而Dll1的强制表达增强了ATOH1、Cdx2和MUC2的表达水平。然而，增强的Dll1并未诱导Hes1表达，这表明Dll1可能主要作为细胞内信号分子发挥作用，而不是经典途径中的Notch激动配体。此外，Cdx2敲低完全消除了胆汁酸处理后Dll1表达的任何增加。我们的结果揭示了Dll1的一种新功能：与Cdx2表达协同促进肠化生。此外，它们表明，由于胆汁酸诱导Cdx2从而在食管上皮细胞中细胞内诱导Dll1表达在BE发展中具有重要作用。
