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

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

doi:10.1016/S1368-8375(02)00039-8

« Previous Next »Oral Oncology
Volume 38, Issue 8 , Pages 779-784, December 2002

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

H Okamura
- Department of Histology and Oral Histology, School of Dentistry, The University of Tokushima, 3-18-15, Kuramoto, Tokushima 770-8504, Japan
H Morimoto
- Department of Anatomy, School of Dentistry, The University of Tokushima 3-18-15, Kuramoto, Tokushima 770-8504, Japan
M Fujita
- First Department of Oral and Maxillofacial Surgery, Kyushu Dental College, 2-6-1, Manazuru, Kitakyushu 803-8580, Japan
F Nasu
- Department of Histology and Oral Histology, School of Dentistry, The University of Tokushima, 3-18-15, Kuramoto, Tokushima 770-8504, Japan
E Sasaki
- Department of Histology and Oral Histology, School of Dentistry, The University of Tokushima, 3-18-15, Kuramoto, Tokushima 770-8504, Japan
T Haneji
- Department of Histology and Oral Histology, School of Dentistry, The University of Tokushima, 3-18-15, Kuramoto, Tokushima 770-8504, Japan
- Corresponding author. Tel.: +81-88-633-7321; fax: +81-88-633-7342

Received 17 May 2002; accepted 29 May 2002.

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.

Keywords: Dephosphorylation, Egr-1, Okadaic acid, Phosphorylation, SCCKN cells