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Updated: Jun 20, 2026
Stimulation of Notch Signaling in Mouse Osteoclast Precursors
Published on: February 28, 2017
Epithelial transformation by KLF4 requires Notch1 but not canonical Notch1 signaling
Zhaoli Liu1, Lihong Teng, Sarah K Bailey
1Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL, USA.
Abstract:
The transcription factors Notch1 and KLF4 specify epithelial cell fates and confer stem cell properties. Suggesting a functional relationship, each gene can act to promote or suppress tumorigenesis in a context-dependent manner, and alteration of KLF4 or Notch pathway genes in mice gives rise to similar phenotypes. Activation of a conditional allele of KLF4 in RK3E epithelial cells rapidly induces expression of Notch1 mRNA and the active, intracellular form of Notch1. KLF4-induced transformation was suppressed by knockdown of endogenous Notch1 using siRNA or an inhibitor of gamma-secretase. Chromatin immunoprecipitation assay shows that KLF4 binds to the proximal Notch1 promoter in human mammary epithelial cells, and siRNA-mediated suppression of KLF4 in human mammary cancer cells results in reduced expression of Notch1. Furthermore, KLF4 and Notch1 expression are correlated in primary human breast tumors (N = 89; Pearson analysis, r > 0.5, p < 0.0001). Like KLF4, Notch1 was previously shown to induce transformation of rat cells immortalized with adenovirus E1A, similar to RK3E cells. We therefore compared the signaling requirements for Notch1- or KLF4-induced malignant transformation of RK3E. As expected, transformation by Notch1 was suppressed by dominant-negative CSL or MAML1, inhibitors of canonical Notch1 signaling. However, these inhibitors did not suppress transformation by KLF4. Therefore, while KLF4-induced transformation requires Notch1, canonical Notch1 signaling is not required, and Notch1 may signal through a distinct pathway in cells with increased KLF4 activity. These results suggest that KLF4 could contribute to breast tumor progression by activating synthesis of Notch1 and by promoting signaling through a non-canonical Notch1 pathway.
Insights
Transcription factor KLF4 activates Notch1, promoting breast tumor progression. While KLF4-induced transformation needs Notch1, it bypasses canonical Notch1 signaling, suggesting a non-canonical pathway in cancer development.
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Biology
Background:
- Notch1 and KLF4 are key transcription factors involved in epithelial cell fate and stemness.
- Both factors play context-dependent roles in tumorigenesis, with alterations leading to similar phenotypes.
- KLF4 and Notch1 pathways are implicated in cell transformation and cancer progression.
Purpose of the Study:
- To investigate the functional relationship between KLF4 and Notch1 in epithelial cell transformation.
- To determine if KLF4-induced transformation relies on canonical Notch1 signaling.
- To explore the role of KLF4-Notch1 interaction in breast tumor progression.
Main Methods:
- Activation of KLF4 in RK3E epithelial cells to assess Notch1 expression.
- Knockdown of Notch1 using siRNA and gamma-secretase inhibitors to study KLF4-induced transformation.
- Chromatin immunoprecipitation assays to detect KLF4 binding to the Notch1 promoter.
- Analysis of KLF4 and Notch1 expression correlation in human breast tumors.
- Comparison of signaling pathways for Notch1- and KLF4-induced transformation.
Main Results:
- KLF4 activation rapidly induces Notch1 mRNA and active intracellular Notch1.
- KLF4-induced transformation is suppressed by Notch1 inhibition, indicating dependence.
- KLF4 binds to the Notch1 promoter, and KLF4 suppression reduces Notch1 expression.
- KLF4 and Notch1 expression are significantly correlated in primary human breast tumors.
- KLF4-induced transformation is not suppressed by inhibitors of canonical Notch1 signaling, unlike Notch1-induced transformation.
Conclusions:
- KLF4 contributes to breast tumor progression by inducing Notch1 synthesis.
- KLF4-induced transformation utilizes Notch1 but not canonical Notch1 signaling, suggesting a non-canonical pathway.
- KLF4 may promote breast cancer through activation of Notch1 and subsequent non-canonical signaling.
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