A variant of Smurf2 protects mice against colitis-associated colon cancer by inducing transforming growth factor β

Heike Dornhoff1, Christoph Becker, Stefan Wirtz

  • 1Department of Medicine, University of Erlangen-Nuremberg, Erlangen and Nuremberg, Germany.

Gastroenterology
|February 16, 2012
PubMed
Abstract

Insights

A novel splice variant of Smad ubiquitin regulating factor 2 (Smurf2), named ΔE2Smurf2, was identified and found to protect against colon cancer in mice. T cell-specific ΔE2Smurf2 up-regulates TGF-β signaling, reducing tumor growth and inflammation.

Area of Science:

  • Oncology
  • Molecular Biology
  • Immunology

Background:

  • Transforming growth factor (TGF)-β signaling is crucial for development but its dysregulation, particularly down-regulation by E3 ubiquitin ligase Smad ubiquitin regulating factor 2 (Smurf2), promotes cancer.
  • A novel splice variant of Smurf2, designated ΔE2Smurf2, was identified, prompting investigation into its role in colon carcinogenesis.

Purpose of the Study:

  • To investigate the role of the newly identified ΔE2Smurf2 splice variant in mouse models of colon cancer.
  • To determine the molecular mechanisms by which ΔE2Smurf2 influences tumor growth and inflammation.

Main Methods:

  • Colitis-associated colon cancer was induced in mice using azoxymethane and dextran sodium sulfate.
  • Messenger RNA levels of Smurf2 and ΔE2Smurf2 were quantified using quantitative polymerase chain reaction.
  • Lymphocyte and cytokine levels in tumor and tissue samples were measured.

Main Results:

  • Tumor-infiltrating CD4(+) cells showed higher ΔE2Smurf2 expression compared to nontumor tissues.
  • T cell-specific overexpression of ΔE2Smurf2 enhanced TGF-β signaling by reducing Smurf2 and increasing TGF-β receptor type II levels.
  • Transgenic mice overexpressing ΔE2Smurf2 exhibited protection against colitis-associated tumors and reduced proinflammatory cytokines like interleukin-6.

Conclusions:

  • T cell-specific ΔE2Smurf2 degrades wild-type Smurf2, thereby controlling intestinal tumor growth in mice.
  • ΔE2Smurf2 exerts its tumor-suppressive effects by up-regulating TGF-β receptor type II, consequently reducing cell proliferation and the production of proinflammatory cytokines.
  • A lower Smurf2/ΔE2Smurf2 ratio was observed in patients with chronic inflammatory bowel disease, suggesting a potential role in human disease.