Suppression of Egr-1 expression in human oral squamous carcinoma cells by okadaic acid.
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.
Okamura
H
H
Department of Histology and Oral Histology, School of Dentistry, The University of Tokushima, 3-18-15, Kuramoto, Tokushima 770-8504, Japan.
Morimoto
H
H
Fujita
M
M
Nasu
F
F
Sasakia
E
E
Haneji
T
T
D002273:Carcinogens / Q000627:therapeutic use*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D051766:Early Growth Response Protein 1; D004587:Electrophoresis, Agar Gel / Q000379:methods; D005786:Gene Expression Regulation; D006801:Humans; D017874:Immediate-Early Proteins; D007150:Immunohistochemistry / Q000379:methods; D009062:Mouth Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D019319:Okadaic Acid / Q000627:therapeutic use*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013489:Suppression, Genetic; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D002273:Carcinogens; D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D017874:Immediate-Early Proteins; D009363:Neoplasm Proteins; D014157:Transcription Factors; D019319:Okadaic Acid