Combinatorial chemoprevention reveals a novel smoothened-independent role of GLI1 in esophageal carcinogenesis

Cancer Res. 2010 Sep 1;70(17):6787-96. doi: 10.1158/0008-5472.CAN-10-0197. Epub 2010 Jul 20.

Abstract

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenocarcinoma / genetics
  • Adenocarcinoma / metabolism
  • Adenocarcinoma / pathology
  • Adenocarcinoma / prevention & control*
  • Animals
  • Anticarcinogenic Agents / administration & dosage*
  • Aspirin / administration & dosage*
  • Barrett Esophagus / drug therapy
  • Barrett Esophagus / genetics
  • Barrett Esophagus / metabolism
  • Barrett Esophagus / pathology
  • Cell Growth Processes / drug effects
  • Cyclin-Dependent Kinase 2 / biosynthesis
  • Cyclin-Dependent Kinase 2 / genetics
  • Cyclin-Dependent Kinase 2 / metabolism
  • Disease Models, Animal
  • Down-Regulation / drug effects
  • Esophageal Neoplasms / genetics
  • Esophageal Neoplasms / metabolism
  • Esophageal Neoplasms / pathology
  • Esophageal Neoplasms / prevention & control*
  • Humans
  • Oncogene Proteins / genetics
  • Oncogene Proteins / metabolism
  • Oncogene Proteins / physiology*
  • Promoter Regions, Genetic / drug effects
  • Protein Binding
  • Rats
  • Trans-Activators / genetics
  • Trans-Activators / metabolism
  • Trans-Activators / physiology*
  • Transfection
  • Ursodeoxycholic Acid / administration & dosage*
  • Zinc Finger Protein GLI1

Substances

  • Anticarcinogenic Agents
  • Oncogene Proteins
  • Trans-Activators
  • Zinc Finger Protein GLI1
  • Ursodeoxycholic Acid
  • Cyclin-Dependent Kinase 2
  • Aspirin