The early growth response gene EGR-1 behaves as a suppressor gene that is down-regulated independent of ARF/Mdm2 but not p53 alterations in fresh human gliomas.
OBJECTIVE
EGR-1 is an immediate early gene with diverse functions that include the suppression of growth. EGR-1 is down-regulated many cancer cell types, suggesting a tumor suppressor role, and may critically involve the p53 pathway. The aim of this work was to measure the expression of EGR-1 and the p16/INK4a/ARF-Mdm2-p53 pathway status in fresh human gliomas.


METHODS
Thirty-one human gliomas with different grades of malignancy were investigated for Egr-1 mRNA and the protein expression, frequency, and spectrum of p53 gene mutations, mdm2 gene amplification, and p16/INK4a/ARF allele loss.


RESULTS
The amplification of Mdm2 and the deletion of the p16/INK4a gene was found in 3 and 5 cases, respectively, whereas mutations of p53, including two novel mutations, were observed in 10 other cases. The three types of changes occurred strictly mutually exclusively, emphasizing that these genes operate in a common pathway critical to glioma progression. EGR-1 mRNA was significantly down-regulated in astrocytomas (14.7 +/- 5.1%) and in glioblastomas (33.6 +/- 10.0%) versus normal brain. Overall, EGR-1 mRNA was strongly suppressed (average, 15.2 +/- 13.9%) in 27 of 31 cases (87%), independent of changes in p16/INK4a/ARF and Mdm2; whereas 4 of 31 cases with residual EGR-1 expression as well as the highest EGR-1 variance segregated with p53 mutations. Immunohistochemical analyses confirmed the suppression of EGR-1 protein.


CONCLUSIONS
These results indicate that EGR-1 is commonly suppressed in gliomas independent of p16/INK4a/ARF and Mdm2 and that suppression is less crucial in tumors bearing p53 mutations, and these results implicate an EGR-1 growth regulatory mechanism as a target of inactivation during tumor progression.
Calogero
A
A
Department of Molecular Pathology, Istituto di Ricovero e Cura a Carattere Scientifico Neuromed, Pozzilli, 86077 Italy. calognant@neuromed.it
Arcella
A
A
De Gregorio
G
G
Porcellini
A
A
Mercola
D
D
Liu
C
C
Lombari
V
V
Zani
M
M
Giannini
G
G
Gagliardi
F M
FM
Caruso
R
R
Gulino
A
A
Frati
L
L
Ragona
G
G
D015152:Blotting, Northern; D001932:Brain Neoplasms / Q000235:genetics* / Q000473:pathology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000737:chemistry / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D051766:Early Growth Response Protein 1; D017353:Gene Deletion; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000235:genetics* / Q000473:pathology; D006801:Humans; D017874:Immediate-Early Proteins; D007150:Immunohistochemistry; D020125:Mutation, Missense; D009687:Nuclear Proteins; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology; D051736:Proto-Oncogene Proteins c-mdm2; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000502:physiology
D019941:Cyclin-Dependent Kinase Inhibitor p16; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D017874:Immediate-Early Proteins; D009687:Nuclear Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D014157:Transcription Factors; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2