Loss of the Transcription Factor GLI1 Identifies a Signaling Network in the Tumor Microenvironment Mediating KRAS Oncogene-Induced Transformation

J Biol Chem. 2013 Apr 26;288(17):11786-94. doi: 10.1074/jbc.M112.438846. Epub 2013 Mar 12.


Although the biological role of KRAS is clearly established in carcinogenesis, the molecular mechanisms underlying this phenomenon are not completely understood. In this study, we provide evidence of a novel signaling network regulated by the transcription factor GLI1 mediating KRAS-induced carcinogenesis. Using pancreatic cancer (a disease with high prevalence of KRAS mutations) as a model, we show that loss of GLI1 blocks the progression of KRAS-induced pancreatic preneoplastic lesions in mice with pancreas-specific Cre-activated oncogenic mutant kras. Mice lacking GLI1 develop only low-grade lesions at low frequency, and in most cases, the pancreata are histologically normal. Further characterization of the phenotype showed a decrease in the activation of STAT3 in pancreatic preneoplastic lesions; STAT3 is a transcription factor required for the development of premalignant lesions and their progression into pancreatic cancer. Analysis of the mechanisms revealed a key role for GLI1 in maintaining the levels of activated STAT3 through the modulation of IL-6 signaling. GLI1 binds to the IL-6 mouse promoter and regulates the activity and expression of this cytokine. This newly identified GLI1/IL-6 axis is active in fibroblasts, a known source of IL-6 in the tumor microenvironment. Sonic hedgehog induces GLI1 binding to the IL-6 promoter and increases IL-6 expression in fibroblasts in a paracrine manner. Finally, we demonstrate that mutant KRAS initiates this cascade by inducing the expression of Sonic hedgehog in cancer cells. Collectively, these results define a novel role for GLI1 in carcinogenesis acting as a downstream effector of oncogenic KRAS in the tumor microenvironment.

Publication types

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

MeSH terms

  • Animals
  • Cell Transformation, Neoplastic / genetics
  • Cell Transformation, Neoplastic / metabolism*
  • Cell Transformation, Neoplastic / pathology
  • Fibroblasts / metabolism
  • Fibroblasts / pathology
  • Gene Expression Regulation, Neoplastic*
  • Hedgehog Proteins / genetics
  • Hedgehog Proteins / metabolism
  • Interleukin-6 / biosynthesis
  • Interleukin-6 / genetics
  • Kruppel-Like Transcription Factors / genetics
  • Kruppel-Like Transcription Factors / metabolism*
  • Mice
  • Mice, Knockout
  • Pancreatic Neoplasms / genetics
  • Pancreatic Neoplasms / metabolism*
  • Pancreatic Neoplasms / pathology
  • Proto-Oncogene Proteins p21(ras) / biosynthesis*
  • Proto-Oncogene Proteins p21(ras) / genetics
  • STAT3 Transcription Factor / genetics
  • STAT3 Transcription Factor / metabolism
  • Tumor Microenvironment*
  • Zinc Finger Protein GLI1


  • Gli1 protein, mouse
  • Hedgehog Proteins
  • Interleukin-6
  • Kruppel-Like Transcription Factors
  • STAT3 Transcription Factor
  • Shh protein, mouse
  • Stat3 protein, mouse
  • Zinc Finger Protein GLI1
  • Hras protein, mouse
  • Proto-Oncogene Proteins p21(ras)