Suppression of Egr-1 expression in human oral squamous carcinoma cells by okadaic acid

Hirohiko Okamura, H. Morimoto, M. Fujita, F. Nasu, E. Sasaki, T. Haneji

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8 Citations (Scopus)

Abstract

We examined the expression of early growth response-1 (Egr-1) gene in human oral squamous carcinoma cell lines SCCKN and SCC-25 cells and human osteoblastic cell lines Saos-2 and MG63 cells treated with okadaic acid, a potent inhibitor of protein phosphatases type 1 and type 2A. Western blot analysis revealed that Egr-1 was strongly expressed in SCCKN cells and that okadaic acid decreased the expression of Egr-1 protein in these cells. However, Egr-1 was expressed at lower levels in SCC-25, Saos-2, and MG63 cells and transiently increased with the okadaic acid treatment. Suppression of Egr-1 protein expression in okadaic acid-treated SCCKN cells stemmed from the suppression of the Egr-1 mRNA level, as determined by the RT-RCR method. Formaldehyde-fixed and alcohol-permeabilized cultured SCCKN cells were reacted with the anti-Egr-1 antibody using immunohistochemical methods. Intense fluorescence was observed in the nuclei of the control SCCKN cells interacted with anti-Egr-1 antibody. However, only a weak reaction was observed in the nuclei in SCCKN cells treated with okadaic acid. A gel mobility shift assay showed that treatment of SCCKN cells with okadaic acid suppressed Egr-1 binding to the DIG-labeled Egr-1 consensus oligonucleotide probe. The present results indicate that the alteration of phosphorylation states in SCCKN cells regulates Egr-1 binding to its consensus sequence and its expression at the transcriptional level.

Original languageEnglish
Pages (from-to)779-784
Number of pages6
JournalOral Oncology
Volume38
Issue number8
DOIs
Publication statusPublished - Dec 2002
Externally publishedYes

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Keywords

  • Dephosphorylation
  • Egr-1
  • Okadaic acid
  • Phosphorylation
  • SCCKN cells

ASJC Scopus subject areas

  • Oncology

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