Notch1 is an effector of Akt and hypoxia in melanoma development
Barbara Bedogni, … , Amato J. Giaccia, Marianne Broome Powell
Barbara Bedogni, … , Amato J. Giaccia, Marianne Broome Powell
Published October 16, 2008
Citation Information: J Clin Invest. 2008;118(11):3660-3670. https://doi.org/10.1172/JCI36157.
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Notch1 is an effector of Akt and hypoxia in melanoma development

Abstract

Melanomas are highly aggressive neoplasms resistant to most conventional therapies. These tumors result from the interaction of altered intracellular tumor suppressors and oncogenes with the microenvironment in which these changes occur. We previously demonstrated that physiologic skin hypoxia contributes to melanomagenesis in conjunction with Akt activation. Here we show that Notch1 signaling is elevated in human melanoma samples and cell lines and is required for Akt and hypoxia to transform melanocytes in vitro. Notch1 facilitated melanoma development in a xenograft model by maintaining cell proliferation and by protecting cells from stress-induced cell death. Hyperactivated PI3K/Akt signaling led to upregulation of Notch1 through NF-κB activity, while the low oxygen content normally found in skin increased mRNA and protein levels of Notch1 via stabilization of HIF-1α. Taken together, these findings demonstrate that Notch1 is a key effector of both Akt and hypoxia in melanoma development and identify the Notch signaling pathway as a potential therapeutic target in melanoma treatment.

Authors

Barbara Bedogni, James A. Warneke, Brian J. Nickoloff, Amato J. Giaccia, Marianne Broome Powell

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Figure 3

Notch1 is transcriptionally regulated by Akt through NF-κB activity.

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Notch1 is transcriptionally regulated by Akt through NF-κB activity. (A)...
(A) Western blot analysis for p65 in nuclei of Akt-expressing melanocytes stably transfected with IκBαM. Tata-binding protein (TBP) was used as loading control for nuclear protein lysates. (B) qRT-PCR analysis of cells in A for IκBα and c-myc. (C) NF-κB reporter assay in melanocytes expressing an empty vector (pBabe), Akt, or Akt/IκBαM. (D) Western blot for TM-Notch1 and Notch1-NIC protein in Akt cells expressing either an empty vector (pBabe) or IκBαM. Tata-binding protein and α-tubulin were used as loading controls for nuclear protein lysates and total protein lysates, respectively. (E) qRT-PCR analysis of cells in D for Notch1. (F and G) Notch1 activity measured as induction of HES1 and HEY1 mRNAs by qRT-PCR. Data in B, C, and E–G are mean ± SD. *P < 0.05 versus pBabe control; #P < 0.05 versus Akt alone; Student’s t test for all comparisons.