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 1

DAB2 is epigenetically downregulated in squamous carcinoma cell lines.

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DAB2 is epigenetically downregulated in squamous carcinoma cell lines. ...
(A) qRT-PCR analysis of DAB2 mRNA expression in HNSCC and VSCC cell lines. RNA levels in UMSCV2 cells were assigned the arbitrary value of 1. Determinations were performed in triplicate. Mean ± SD (n = 2) are shown. (B and C) Western blot analysis of DAB2 expression in HNSCC (B) and VSCC cell lines (C). Samples in C were run on the same gel but were noncontiguous as indicated by the white line. DAB2 is indicated on the figure. The asterisk indicates cross-reactive nonspecific bands. (D) Analysis of CpG island methylation in SCC cell lines and normal oral keratinocytes (NK). A schematic representation of the CpG island located at the 5′ end of the human DAB2 gene and each of the 53 CpG dinucleotides is shown. DAB2 promoter methylation determined by bisulphite sequencing is represented as a solid square. pyro, pyrosequencing. (E) MSP analysis of SCC cell lines using MSP primers depicted in D. U and M refer to unmethylated and methylated PCR reactions, respectively.