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Differentiation-inducing factor-1 induces cyclin D1 degradation through the phosphorylation of Thr286 in squamous

Jun Mori1, Fumi Takahashi-Yanaga, Yoshikazu Miwa

  • 1Department of Clinical Pharmacology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.

Experimental Cell Research
|September 13, 2005
PubMed

Insights

Differentiation-inducing factor 1 (DIF-1) inhibits oral cancer cell proliferation by halting the cell cycle. It triggers cyclin D1 degradation via glycogen synthase kinase-3beta (GSK-3beta) activation, specifically targeting Thr286 phosphorylation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • Differentiation-inducing factors (DIFs) are key morphogens in Dictyostelium development.
  • Previous research indicates DIF-1 and DIF-3 can inhibit proliferation and induce differentiation in mammalian cells.

Purpose of the Study:

  • To investigate the effects of DIF-1 on oral squamous cell carcinoma (OSCC) cell lines.
  • To elucidate the molecular mechanisms underlying DIF-1's impact on OSCC proliferation and cell cycle regulation.

Main Methods:

  • Treatment of OSCC cell lines (NA and SAS) with DIF-1.
  • Cell cycle analysis using flow cytometry.
  • Western blotting to assess protein expression and degradation (cyclin D1, GSK-3beta).
  • Analysis of GSK-3beta activity using inhibitors and RNA interference.
  • Investigation of DIF-1 effects on cyclin D1 mutants.

Main Results:

  • DIF-1 inhibited proliferation of both well-differentiated (NA) and poorly differentiated (SAS) OSCC cell lines in a dose-dependent manner.
  • DIF-1 restricted the cell cycle in the G0/G1 phase without inducing differentiation markers.
  • DIF-1 induced cyclin D1 degradation, a process dependent on glycogen synthase kinase-3beta (GSK-3beta) activation.
  • DIF-1 activated GSK-3beta by dephosphorylating it at Ser9 and promoting nuclear translocation.
  • Phosphorylation at Thr286 of cyclin D1 was critical for DIF-1-induced degradation.

Conclusions:

  • DIF-1 inhibits OSCC cell proliferation by arresting the cell cycle at G0/G1.
  • The mechanism involves DIF-1-induced activation of GSK-3beta, leading to the degradation of cyclin D1.
  • Targeting the GSK-3beta/cyclin D1 pathway may offer therapeutic strategies for oral squamous cell carcinoma.

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