Epigenetic downregulation of human disabled homolog 2 switches TGF-β from a tumor suppressor to a tumor promoter
Adèle Hannigan, … , Tim Crook, Gareth J. Inman
Adèle Hannigan, … , Tim Crook, Gareth J. Inman
Published July 1, 2010
Citation Information: J Clin Invest. 2010;120(8):2842-2857. https://doi.org/10.1172/JCI36125.
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Research Article Oncology

Epigenetic downregulation of human disabled homolog 2 switches TGF-β from a tumor suppressor to a tumor promoter

Abstract

The cytokine TGF-β acts as a tumor suppressor in normal epithelial cells and during the early stages of tumorigenesis. During malignant progression, cancer cells can switch their response to TGF-β and use this cytokine as a potent oncogenic factor; however, the mechanistic basis for this is poorly understood. Here we demonstrate that downregulation of disabled homolog 2 (DAB2) gene expression via promoter methylation frequently occurs in human squamous cell carcinomas (SCCs) and acts as an independent predictor of metastasis and poor prognosis. Retrospective microarray analysis in an independent data set indicated that low levels of DAB2 and high levels of TGFB2 expression correlate with poor prognosis. Immunohistochemistry, reexpression, genetic knockout, and RNAi silencing studies demonstrated that downregulation of DAB2 expression modulated the TGF-β/Smad pathway. Simultaneously, DAB2 downregulation abrogated TGF-β tumor suppressor function, while enabling TGF-β tumor-promoting activities. Downregulation of DAB2 blocked TGF-β–mediated inhibition of cell proliferation and migration and enabled TGF-β to promote cell motility, anchorage-independent growth, and tumor growth in vivo. Our data indicate that DAB2 acts as a tumor suppressor by dictating tumor cell TGF-β responses, identify a biomarker for SCC progression, and suggest a means to stratify patients with advanced SCC who may benefit clinically from anti–TGF-β therapies.

Authors

Adèle Hannigan, Paul Smith, Gabriela Kalna, Cristiana Lo Nigro, Clare Orange, Darren I. O’Brien, Reshma Shah, Nelofer Syed, Lindsay C. Spender, Blanca Herrera, Johanna K. Thurlow, Laura Lattanzio, Martino Monteverde, Meghan E. Maurer, Francesca M. Buffa, Jelena Mann, David C.K. Chu, Catharine M.L. West, Max Patridge, Karin A. Oien, Jonathan A. Cooper, Margaret C. Frame, Adrian L. Harris, Louise Hiller, Linda J. Nicholson, Milena Gasco, Tim Crook, Gareth J. Inman

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Figure 5

DAB2 levels correlate with TGF-β responses in SCC cell lines.

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DAB2 levels correlate with TGF-β responses in SCC cell lines. (A and B) ...
(A and B) Cell lines were treated with 1 ng/ml TGF-β for 48 hours, and [3H]thymidine incorporation assays were performed. Results are represented as the relative [3H]thymidine incorporation, where untreated samples are assigned an arbitrary mean value of 1. Data are represented as mean ± SD (n = 3). TGF-β inhibits proliferation in cell lines that express high levels of DAB2 (A) but does not in cell lines that express low levels of DAB2 (B). (C and D). Indicated cell lines were grown to confluency and serum starved, and then scratch assays were performed and cell motility was monitored using time lapse microscopy. Unstimulated directional motility rates were assigned an arbitrary mean value of 1. Data are represented as the mean ± SD (n = 6). TGF-β inhibits motility in cell lines that express high levels of DAB2 (C) and promotes motility in cell lines that express low levels of DAB2 (D). (E and F) TGF-β promotes anchorage-independent growth in cell lines with low-level DAB2 expression. (E) Representative images of soft agar assays from the indicated cell lines untreated (–) or treated with TGF-β. Scale bar: 0.5 mm. (F) Graphical analysis of soft agar assays. Data represent the mean ± SD (n = 3). Statistical analyses were performed with paired 2 tailed t tests throughout. *P < 0.05, **P < 0.01, ***P < 0.001.