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Epidermal growth factor receptors in human tumors of the central nervous system
L Baugnet-Mahieu1, M Lemaire, J Brotchi
1Department of Radioprotection, CEN-SCK, Mol, Belgium.
Abstract:
Epidermal growth factor receptors (EGF-R) have been measured in human tumors of the Central Nervous System (CNS) by 125I EGF ligand binding. High affinity receptors (Ka congruent to 1 x 10(9) M-1) were detected in nearly all individual specimens of meningiomas and tumors of glial origin (astrocytomas, glioblastomas). The phosphotyrosine kinase activity associated with the EGF-R was evaluated by measuring the incorporation of gamma 32P-ATP, after immunoprecipitation of the receptor with the monoclonal antibody EGFRI. A good relationship was observed between the EGF-binding capacity and the autophosphorylation of the receptor, indicating that in most cases functional molecules of EGF-R were expressed on the tumor membranes. In the group of meningiomas, no relationship could be established between the EGF-R level and the histopathology of the tumors. Astrocytomas exemplify a progression of malignancy, from benign (low grade astrocytomas) towards an increased malignant phenotype (glioblastomas). In this group, our observations indicate a positive relationship between the EGF-R level and phosphokinase activity and the degree of malignancy.
Insights
Epidermal growth factor receptors (EGF-R) are present in most human brain tumors. Higher EGF-R levels correlate with increased malignancy in astrocytomas, suggesting a role in tumor progression.
Area of Science:
- Neuro-oncology
- Molecular biology
- Biochemistry
Background:
- Epidermal growth factor receptors (EGF-R) play a role in cell growth and are implicated in various cancers.
- Understanding EGF-R expression in Central Nervous System (CNS) tumors is crucial for potential therapeutic strategies.
Purpose of the Study:
- To quantify EGF-R expression and associated kinase activity in human CNS tumors.
- To investigate the relationship between EGF-R levels, kinase activity, and tumor malignancy.
Main Methods:
- Quantification of high-affinity EGF-R using 125I EGF ligand binding assays.
- Assessment of EGF-R associated phosphotyrosine kinase activity via gamma 32P-ATP incorporation after immunoprecipitation.
- Correlation analysis between EGF-R levels, kinase activity, and histopathological grading of tumors.
Main Results:
- High-affinity EGF-R were detected in most meningiomas and glial tumors (astrocytomas, glioblastomas).
- A strong correlation was observed between EGF-binding capacity and receptor autophosphorylation, indicating functional EGF-R on tumor cells.
- No correlation was found between EGF-R levels and histopathology in meningiomas.
- In astrocytomas, a positive relationship was identified between EGF-R levels, phosphokinase activity, and the degree of malignancy.
Conclusions:
- Functional EGF-R are expressed on human meningiomas and glial tumors.
- EGF-R levels and activity correlate with malignancy in astrocytomas, suggesting a role in tumor progression.
- These findings may inform targeted therapies for CNS malignancies expressing EGF-R.