Division of Gastroenterology and Hepatology, Schulze Center for Novel Therapeutics, Mayo Clinic, Rochester, MN, USA.
Cancer Res. 2010 Sep 1;70(17):6787-96. doi: 10.1158/0008-5472.CAN-10-0197. Epub 2010 Jul 20.
Reflux-induced injury promotes esophageal adenocarcinoma, one of the most rapidly increasing, highly lethal cancers in Western countries. Here, we investigate the efficacy of a combinatorial chemoprevention strategy for esophageal adenocarcinoma and characterize the underlying molecular mechanisms. Specifically, our approach involves the use of ursodeoxycholic acid (Urso) due to its ability to decrease injury-inducing bile salts in combination with Aspirin to mitigate the consequences of injury. We find that Urso-Aspirin combination reduces the risk of adenocarcinoma in vivo in animals with reflux, decreases the proliferation of esophageal adenocarcinoma cells, and downregulates a key cell cycle regulator, CDK2. Mechanistically, using cell growth, luciferase reporter, expression, and chromatin immunoprecipitation assays, we identify GLI1, a Hedgehog-regulated transcription factor, as a novel target of Urso-Aspirin combination. We show that GLI1 is upregulated during esophageal carcinogenesis, and GLI1 can bind to the CDK2 promoter and activate its expression. Although the Urso-Aspirin combination downregulates GLI1, the GLI1 overexpression not only abrogates the effect of this combination on proliferation but it also restores CDK-2 expression. These findings support that the chemopreventive effect of the Urso-Aspirin combination occurs, at least in part, through a novel GLI1-CDK2-dependent mechanism. To further understand the regulation of CDK2 by GLI1, both pharmacologic and RNAi-mediated approaches show that GLI1 is a transcriptional activator of CDK2, and this regulation occurs independent of Smoothened, the central transducer of the Hedgehog canonical pathway. Collectively, these results identify a novel GLI1-to-CDK2 pathway in esophageal carcinogenesis, which is a bona fide target for effective combinatorial chemoprevention with Urso and Aspirin.
反流诱导的损伤促进了食管腺癌的发生，这是西方国家发病率增长最快、致死率最高的癌症之一。在这里，我们研究了一种食管腺癌的联合化学预防策略的疗效，并对其潜在的分子机制进行了表征。具体来说，我们的方法涉及使用熊去氧胆酸（Urso），因为它能够降低损伤诱导的胆汁盐，同时联合使用阿司匹林来减轻损伤的后果。我们发现，Urso-阿司匹林联合用药可降低动物反流模型中腺癌的风险，降低食管腺癌细胞的增殖，并下调关键的细胞周期调节剂 CDK2。在机制上，我们通过细胞生长、荧光素酶报告基因、表达和染色质免疫沉淀实验，确定了 Hedgehog 调节转录因子 GLI1 是 Urso-阿司匹林联合用药的一个新靶点。我们表明，在食管癌变过程中 GLI1 上调，GLI1 可以结合 CDK2 启动子并激活其表达。尽管 Urso-阿司匹林联合用药下调了 GLI1，但 GLI1 的过表达不仅消除了这种联合用药对增殖的影响，而且还恢复了 CDK-2 的表达。这些发现支持 Urso-阿司匹林联合用药的化学预防作用至少部分是通过一种新的 GLI1-CDK2 依赖机制发生的。为了进一步了解 GLI1 对 CDK2 的调控，药理学和 RNAi 介导的方法都表明 GLI1 是 CDK2 的转录激活剂，这种调控发生在 Hedgehog 经典途径的中央转导子 Smoothened 之外。总之，这些结果确定了在食管癌变过程中 GLI1 到 CDK2 的新途径，这是 Urso 和阿司匹林进行有效联合化学预防的一个真正的靶点。
