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

• Published in: Oral oncology Vol. 38; no. 8; pp. 779 - 784
• Main Authors: Okamura, H, Morimoto, H, Fujita, M, Nasu, F, Sasaki, E, Haneji, T
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.12.2002; Elsevier
• Subjects: Biological and medical sciences; Carcinogens - therapeutic use; Carcinoma, Squamous Cell - drug therapy; Carcinoma, Squamous Cell - genetics; Carcinoma, Squamous Cell - metabolism; Dephosphorylation; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Down-Regulation; Early Growth Response Protein 1; Egr-1; Electrophoresis, Agar Gel - methods; Ent. Stomatology; Gene Expression Regulation; Humans; Immediate-Early Proteins; Immunohistochemistry - methods; Medical sciences; Mouth Neoplasms - drug therapy; Mouth Neoplasms - genetics; Mouth Neoplasms - metabolism; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; Okadaic acid; Okadaic Acid - therapeutic use; Otorhinolaryngology. Stomatology; Pharmacology. Drug treatments; Phosphorylation; Reverse Transcriptase Polymerase Chain Reaction - methods; SCCKN cells; Suppression, Genetic; Transcription Factors - genetics; Transcription Factors - metabolism; Tumor Cells, Cultured; Tumors; Upper respiratory tract, upper alimentary tract, paranasal sinuses, salivary glands: diseases, semeiology; Egr-1; Okadaic acid; Phosphorylation; Dephosphorylation; SCCKN cells; Squamous cell carcinoma; Stomatology; Immunocytochemistry; Suppression; Malignant tumor; Experimental study; Pathology; Oral cavity; Chemotherapy; Cell line; Treatment; Oral cavity disease; Biological effect; Molecular biology; Reverse transcription polymerase chain reaction
• ISSN: 1368-8375; 1879-0593
• DOI: 10.1016/S1368-8375(02)00039-8

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.