Activation of Wnt signaling pathway by human papillomavirus E6 and E7 oncogenes in HPV16-positive oropharyngeal squamous carcinoma cells

Theodore Rampias, Eleni Boutati, Eirini Pectasides, Clarence Sasaki, Panteleimon Kountourakis, Paul Weinberger, Amanda Psyrri

Research output: Contribution to journalArticle

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Abstract

We sought to determine the role of human papillomavirus (HPV) E6 and E7 oncogenes in nuclear β-catenin accumulation, a hallmark of activated canonical Wnt signaling pathway. We used HPV16-positive oropharyngeal cancer cell lines 147T and 090, HPV-negative cell line 040T, and cervical cell lines SiHa (bearing integrated HPV16) and HeLa (bearing integrated HPV18) to measure the cytoplasmic and nuclear β-catenin levels and the β-catenin/Tcf transcriptional activity before and after E6/E7 gene silencing. Repression of HPV E6 and E7 genes induced a substantial reduction in nuclear β-catenin levels. Luciferase assay showed that transcriptional activation of Tcf promoter by β-catenin was lower after silencing. The protein levels of β-catenin are tightly regulated by the ubiquitin/proteasome system. We therefore performed expression analysis of regulators of β-catenin degradation and nuclear transport and showed that seven in absentia homologue (Siah-1) mRNA and protein levels were substantially upregulated after E6/E7 repression. Siah-1 protein promotes the degradation of β-catenin through the ubiquitin/proteasome system. To determine whether Siah-1 is important for the proteasomal degradation of β-catenin in HPV16-positive oropharyngeal cancer cells, we introduced a Siah-1 expression vector into 147T and 090 cells and found substantial reduction of endogenous β-catenin in these cells. Thus, E6 and E7 are involved in β-catenin nuclear accumulation and activation of Wnt signaling in HPV-induced cancers. In addition, we show the significance of the endogenous Siah-1-dependent ubiquitin/ proteasome pathway for β-catenin degradation and its regulation by E6/E7 viral oncoproteins in HPV16-positive oropharyngeal cancer cells.

Original languageEnglish (US)
Pages (from-to)433-443
Number of pages11
JournalMolecular Cancer Research
Volume8
Issue number3
DOIs
StatePublished - Mar 1 2010

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Catenins
Wnt Signaling Pathway
Oncogenes
Squamous Cell Carcinoma
Oropharyngeal Neoplasms
Proteasome Endopeptidase Complex
Ubiquitin
Cell Line
Cell Nucleus Active Transport
Oncogene Proteins
Gene Silencing
Luciferases
Transcriptional Activation
Proteolysis

ASJC Scopus subject areas

  • Molecular Biology
  • Cancer Research
  • Oncology

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Activation of Wnt signaling pathway by human papillomavirus E6 and E7 oncogenes in HPV16-positive oropharyngeal squamous carcinoma cells. / Rampias, Theodore; Boutati, Eleni; Pectasides, Eirini; Sasaki, Clarence; Kountourakis, Panteleimon; Weinberger, Paul; Psyrri, Amanda.

In: Molecular Cancer Research, Vol. 8, No. 3, 01.03.2010, p. 433-443.

Research output: Contribution to journalArticle

Rampias, Theodore ; Boutati, Eleni ; Pectasides, Eirini ; Sasaki, Clarence ; Kountourakis, Panteleimon ; Weinberger, Paul ; Psyrri, Amanda. / Activation of Wnt signaling pathway by human papillomavirus E6 and E7 oncogenes in HPV16-positive oropharyngeal squamous carcinoma cells. In: Molecular Cancer Research. 2010 ; Vol. 8, No. 3. pp. 433-443.
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