Department of Pathology, Aichi Medical University School of Medicine, Nagakute, Aichi, Japan.
Oncogene. 2011 Feb 10;30(6):714-23. doi: 10.1038/onc.2010.459. Epub 2010 Oct 25.
The Krüppel-like zinc-finger protein GLI1 functions as a downstream transcription factor of Hedgehog signaling and plays a pivotal role in the cellular proliferation of many types of tumors, including pancreatic ductal adenocarcinoma (PDA). PDA develops from dysplastic lesions called pancreatic intraepithelial neoplasia (PanIN) through a multistep carcinogenesis process that changes its cellular characteristics, including a mucin expression profile. Increased expression of a gel-forming mucin, MUC5AC, was previously revealed as a major biomarker for the poor prognosis of PDA patients, but the molecular mechanisms responsible for its expression and correlation with poor prognosis are not fully understood. Here we show that MUC5AC is a direct transcriptional target of GLI1 in PDA cells. Overexpression of GLI1 enhanced MUC5AC expression, and a double knockdown of GLI1 and GLI2 suppressed endogenous MUC5AC expression in PDA cells. Luciferase reporter assays revealed that GLI1 and GLI2 can activate the MUC5AC promoter through its conserved CACCC-box-like cis-regulatory elements. We also found that GLI1-upregulated MUC5AC was expressed in the intercellular junction between cultured PDA cells and interfered with the membrane localization of E-cadherin, leading to decreased E-cadherin-dependent cell-cell adhesion and promoting the migration and invasion of PDA cells. Consistently, GLI1 induced the nuclear accumulation and target gene expression of β-catenin in a MUC5AC-dependent manner. Finally, immunohistochemical analysis revealed that GLI1 expression statistically correlated with MUC5AC expression and also with altered subcellular localization of E-cadherin and β-catenin in PanIN lesions and PDA. This evidence revealed a new aspect of GLI1 function in modulating E-cadherin/β-catenin-regulated cancer cell properties through the expression of a gel-forming mucin.
Krüppel 样锌指蛋白 GLI1 作为 Hedgehog 信号通路的下游转录因子发挥作用，在包括胰腺导管腺癌 (PDA) 在内的多种肿瘤的细胞增殖中起着关键作用。PDA 由称为胰腺上皮内瘤变 (PanIN) 的发育不良病变发展而来，通过多步致癌过程改变其细胞特征，包括粘蛋白表达谱。以前曾发现凝胶形成粘蛋白 MUC5AC 的表达增加是 PDA 患者预后不良的主要生物标志物，但导致其表达及其与不良预后相关性的分子机制尚不完全清楚。在这里，我们表明 MUC5AC 是 PDA 细胞中 GLI1 的直接转录靶标。GLI1 的过表达增强了 MUC5AC 的表达，并且 GLI1 和 GLI2 的双重敲低抑制了 PDA 细胞中内源性 MUC5AC 的表达。荧光素酶报告基因检测显示，GLI1 和 GLI2 可以通过其保守的 CACCC 盒样顺式调节元件激活 MUC5AC 启动子。我们还发现，GLI1 上调的 MUC5AC 表达在培养的 PDA 细胞之间的细胞连接处，并干扰 E-钙粘蛋白的膜定位，导致 E-钙粘蛋白依赖性细胞-细胞粘附减少，并促进 PDA 细胞的迁移和侵袭。一致地，GLI1 以 MUC5AC 依赖的方式诱导 β-连环蛋白的核积累和靶基因表达。最后，免疫组织化学分析表明，GLI1 表达与 MUC5AC 表达以及 E-钙粘蛋白和 β-连环蛋白在 PanIN 病变和 PDA 中的亚细胞定位改变呈统计学相关。这些证据揭示了 GLI1 通过表达凝胶形成粘蛋白调节 E-钙粘蛋白/β-连环蛋白调节的癌细胞特性的新方面。
