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Notch1 oncoprotein antagonizes TGF-beta/Smad-mediated cell growth suppression via sequestration of coactivator p300

Shigeo Masuda1, Keiki Kumano, Kiyoshi Shimizu

  • 1Department of Hematology, Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo 113-8655, Japan.

Cancer Science
|May 21, 2005
PubMed

Insights

Notch signaling can promote cancer by blocking the growth-inhibiting effects of transforming growth factor-beta (TGF-beta). This occurs when Notch sequesters a protein called p300, preventing it from working with Smad3.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Cancer Research

Background:

  • Notch proteins are transmembrane receptors crucial for cell development.
  • Dysregulated Notch signaling is linked to cancer, but mechanisms remain unclear.
  • Transforming growth factor-beta (TGF-beta) signaling typically inhibits cell proliferation.

Purpose of the Study:

  • To investigate the mechanistic link between Notch and TGF-beta signaling in cancer.
  • To elucidate how Notch signaling interferes with TGF-beta's antiproliferative effects.

Main Methods:

  • Studied the transcriptional cross-talk between Notch and TGF-beta signaling pathways.
  • Utilized constitutively active Notch1 and transcriptional coactivator p300 in experiments.
  • Employed small interfering RNA (siRNA) to suppress Notch1 expression in CaSki cervical carcinoma cells.

Main Results:

  • Constitutively active Notch1 suppresses TGF-beta-mediated transcriptional responses.
  • The inhibitory effect of Notch1 on TGF-beta signaling is dependent on p300.
  • Notch1 sequesters p300 from Smad3, blocking TGF-beta signaling.
  • Suppression of Notch1 in CaSki cells restores TGF-beta responsiveness.

Conclusions:

  • Notch oncoproteins contribute to cancer development by inhibiting TGF-beta's growth-suppressive functions.
  • This inhibition is achieved through the sequestration of p300 from Smad3 by Notch.
  • Targeting this Notch-TGF-beta interaction may offer therapeutic strategies for cancers driven by Notch signaling.

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