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

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.

• Authors: H Okamura, H Morimoto, M Fujita, F Nasu, E Sasakia, T Haneji
• Journal: Oral oncology (Oral Oncol) Vol. 38 Issue 8 Pg. 779-84 (Dec 2002) ISSN: 1368-8375 [Print] England
• PMID: 12570057 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Carcinogens
• DNA-Binding Proteins
• EGR1 protein, human
• Early Growth Response Protein 1
• Immediate-Early Proteins
• Neoplasm Proteins
• Transcription Factors
• Okadaic Acid

Topics

• Carcinogens (therapeutic use)
• Carcinoma, Squamous Cell (drug therapy, genetics, metabolism)
• DNA-Binding Proteins (genetics, metabolism)
• Down-Regulation
• Early Growth Response Protein 1
• Electrophoresis, Agar Gel (methods)
• Gene Expression Regulation
• Humans
• Immediate-Early Proteins
• Immunohistochemistry (methods)
• Mouth Neoplasms (drug therapy, genetics, metabolism)
• Neoplasm Proteins (genetics, metabolism)
• Okadaic Acid (therapeutic use)
• Reverse Transcriptase Polymerase Chain Reaction (methods)
• Suppression, Genetic
• Transcription Factors (genetics, metabolism)
• Tumor Cells, Cultured