The transcription factor EGR-1 directly transactivates the fibronectin gene and enhances attachment of human glioblastoma cell line U251.
EGR-1, a transcription factor with important functions in the regulation of growth and differentiation, is highly expressed in brain. Previous studies have shown that EGR-1 suppresses the transformed phenotype. However, the expression and role of EGR-1 in human glioblastoma cells are not yet determined. In this study, we found that the basal expression of the EGR-1 protein is undetectable, but is inducible in four human glioblastoma cell lines. To determine EGR-1 functions, we re-expressed EGR-1 in human glioblastoma U251 cells and found that the secretion of transforming growth factor-beta1 (TGF-beta1), plasminogen activator inhibitor-1 (PAI-1), and fibronectin (FN) was greatly enhanced. Addition of anti-TGF-beta antibodies completely inhibited the secretion of PAI-1, but had little effect on secretion of FN, indicating that PAI-1 is under the control of EGR-1-induced TGF-beta1. An examination of the promoter of the FN gene revealed two EGR-1-binding sites between positions -75 and -52 and positions -4 and +14 that specifically bound EGR-1 in gel mobility shift experiments. Utilizing wild-type and mutant FN promoter/luciferase reporter genes, we demonstrated that EGR-1 positively regulated the activity of the FN gene. In addition, cell adhesion and migration were greatly increased in the EGR-1-expressing cells, and adhesion was reversed by addition of RGD-containing peptides. These results suggest that EGR-1 may regulate cell interaction with the extracellular matrix by coordinated induction of TGF-beta1, FN, and PAI-1 in human glioblastoma cells.
Liu
C
C
Sidney Kimmel Cancer Center, San Diego, California 92121, USA. cliu@skcc.org
Yao
J
J
Mercola
D
D
Adamson
E
E
D000906:Antibodies / Q000494:pharmacology; D001665:Binding Sites; D002448:Cell Adhesion; D002465:Cell Movement; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051766:Early Growth Response Protein 1; D005109:Extracellular Matrix / Q000378:metabolism; D005353:Fibronectins / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D017930:Genes, Reporter; D005909:Glioblastoma; D006801:Humans; D017874:Immediate-Early Proteins; D009154:Mutation; D009842:Oligopeptides / Q000494:pharmacology; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics*; D016212:Transforming Growth Factor beta / Q000276:immunology; D014407:Tumor Cells, Cultured
D000906:Antibodies; D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D005353:Fibronectins; D017874:Immediate-Early Proteins; D009842:Oligopeptides; D017395:Plasminogen Activator Inhibitor 1; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; C047981:arginyl-glycyl-aspartic acid