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PTEN expression elicited by EGR-1 transcription factor in calyculin A-induced apoptotic cells

Hirohiko Okamura1, Kaya Yoshida, Hiroyuki Morimoto

  • 1Department of Histology and Oral Histology, School of Dentistry, The University of Tokushima, Kuramoto, Tokushima 770-8504, Japan. okamura@dent.tokushima-u.ac.jp

Journal of Cellular Biochemistry
|November 2, 2004
PubMed

Insights

Protein phosphatase inhibitor calyculin A induces apoptosis by upregulating PTEN expression and phosphorylating EGR-1 in squamous carcinoma cells. EGR-1 regulates PTEN expression, impacting the apoptotic pathway.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • PTEN is a tumor suppressor regulating cell survival via the PI3K-Akt pathway.
  • EGR-1 is an early response gene crucial for cell growth and differentiation.
  • Protein phosphatase inhibitors like calyculin A induce apoptosis, but mechanisms are unclear.

Purpose of the Study:

  • To investigate PTEN and EGR-1 expression and Akt/EGR-1 phosphorylation in calyculin A-treated human squamous carcinoma cells (SCCTF).

Main Methods:

  • Treatment of SCCTF cells with calyculin A.
  • Analysis of PTEN and EGR-1 expression.
  • Assessment of EGR-1 and Akt phosphorylation status.
  • RNA interference targeting EGR-1.
  • Evaluation of p53-null cells.

Main Results:

  • Calyculin A induced time- and dose-dependent phosphorylation of EGR-1 and upregulation of PTEN expression in SCCTF cells.
  • Increased PTEN expression correlated with decreased phosphorylated Akt.
  • EGR-1 and PTEN expression were induced by calyculin A independently of p53.
  • EGR-1 knockdown inhibited both EGR-1 and PTEN expression.
  • Calyculin A induced apoptosis markers like nuclear fragmentation and chromatin condensation.

Conclusions:

  • PTEN expression levels and Akt phosphorylation are linked to calyculin A-induced apoptosis.
  • EGR-1 regulates PTEN expression during the early stages of the apoptotic pathway.

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