Activation of Notch1 signaling is required for β-catenin–mediated human primary melanoma progression
Klara Balint, … , Meenhard Herlyn, Zhao-Jun Liu
Klara Balint, … , Meenhard Herlyn, Zhao-Jun Liu
Published November 1, 2005
Citation Information: J Clin Invest. 2005;115(11):3166-3176. https://doi.org/10.1172/JCI25001.
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Research Article Oncology

Activation of Notch1 signaling is required for β-catenin–mediated human primary melanoma progression

Abstract

Notch is a highly conserved transmembrane receptor that determines cell fate. Notch signaling denotes cleavage of the Notch intracellular domain, its translocation to the nucleus, and subsequent activation of target gene transcription. Involvement of Notch signaling in several cancers is well known, but its role in melanoma remains poorly characterized. Here we show that the Notch1 pathway is activated in human melanoma. Blocking Notch signaling suppressed whereas constitutive activation of the Notch1 pathway enhanced primary melanoma cell growth both in vitro and in vivo yet had little effect on metastatic melanoma cells. Activation of Notch1 signaling enabled primary melanoma cells to gain metastatic capability. Furthermore, the oncogenic effect of Notch1 on primary melanoma cells was mediated by β-catenin, which was upregulated following Notch1 activation. Inhibiting β-catenin expression reversed Notch1-enhanced tumor growth and metastasis. Our data therefore suggest a β-catenin–dependent, stage-specific role for Notch1 signaling in promoting the progression of primary melanoma.

Authors

Klara Balint, Min Xiao, Chelsea C. Pinnix, Akinobu Soma, Imre Veres, Istvan Juhasz, Eric J. Brown, Anthony J. Capobianco, Meenhard Herlyn, Zhao-Jun Liu

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Activation of Notch1 signaling stabilizes β-catenin in primary melanoma ...
Activation of Notch1 signaling stabilizes β-catenin in primary melanoma cell lines. (A) Immunoblotting analysis demonstrates increased levels of β-catenin in NIC–GFP-transfected RGP and VGP primary melanomas but not in NIC–GFP-transfected melanocytes or metastatic melanoma cells. Levels of β-actin are shown for equal loading conditions. (B) DAPT treatment inhibits β-catenin expression in melanoma cells. Cells were treated with 1 μM DAPT for 24 hours, and whole-cell lysates were analyzed by immunoblotting assays. Levels of β-actin are shown for equal loading conditions. (C) Introducing exogenous β-catenin overrides the inhibitory effect of DAPT on primary melanoma cell growth. β-catenin/adenovirus–transfected melanoma cells were treated with DAPT (1 μM) or DMSO. Overexpression of β-catenin accelerated cell growth as measured by MTT assay. Inner panel shows detection of β-catenin expression by immunoblot. Although DAPT suppressed cell proliferation, the growth rate was comparable to that of parental cells not treated with DAPT. Results are mean ± SD of 3 independent experiments. *P < 0.01, Student’s t test. (D) Luciferase assay demonstrates an enhanced TCF-mediated transcription activity in NIC–GFP-transfected cells compared with control cells. Data were normalized by setting the luciferase activities of control cells as 100. Results are mean ± SD of 3 independent experiments. **P < 0.001, Student’s t test. (E) RT-PCR analysis demonstrates that RNA levels of β-catenin are not concurrently upregulated in the NIC–GFP-transfected RGP and VGP cell lines, suggesting a posttranscriptional mechanism in stabilizing β-catenin. β-actin was used as control.