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The epidermal growth factor receptor in glioblastoma: genomic amplification, protein expression, and patient survival
Abstract:
Human glioblastomas were evaluated for overexpression of the epidermal growth factor receptor (EGFR) in a therapeutic trial with the anti-EGFR antibody EMD 55900. A total of 55 cases were examined by immunohistochemistry using 4 different monoclonal antibodies on frozen or on paraffin sections: EGFR-1 (Amersham), E 62 (Merck), E 30 (Merck), and EMD 55900 (MAB 425, Merck). Definition for inclusion in clinical trials of EMD 55900 was an immunohistochemical overexpression of grade 4+ or 3+ in a scale of 4 grades of staining quality. The use of the 4 different antibodies gave essentially equal results. In 21 cases, the immunohistochemical results were supplemented by molecular genetic analysis of EGFR amplification on the corresponding locus of chromosome 7, using frozen tissue from the same blocks after screening for vital tumor areas. Since no other material was available, the differential polymerase chain reaction technique was applied. Interferon-gamma (IFN-gamma) served as a reference gene. In a preliminary experimental series with cases of known EGFR amplification, a densitometric EGFR/IFN-gamma ratio higher than 3 was determined as indicator for amplification of the EGFR gene. With this experimental approach we were able to identify an amplified EGFR gene in 13 specimens including 2 from recurrent glioblastomas in the same patients. All of these showed an increased immunoreactivity for EGFR protein. The degree of EGFR amplification (EGFR/IFN-gamma ratio as measured by DNA densitometry) showed a positive correlation with the grade of immunohistochemical protein expression, both in regard to the fraction of positive cells and to the overall staining intensity.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
This study investigated epidermal growth factor receptor (EGFR) overexpression in glioblastomas using immunohistochemistry and genetic analysis. Results show a correlation between EGFR gene amplification and protein expression, aiding in patient selection for targeted therapies.
Area of Science:
- Oncology
- Molecular Biology
- Immunohistochemistry
Background:
- Glioblastomas often exhibit epidermal growth factor receptor (EGFR) overexpression.
- Targeted therapies using anti-EGFR antibodies are being explored for glioblastoma treatment.
- Accurate assessment of EGFR status is crucial for patient selection in clinical trials.
Purpose of the Study:
- To evaluate EGFR overexpression in human glioblastomas for a therapeutic trial with the anti-EGFR antibody EMD 55900.
- To correlate immunohistochemical findings with molecular genetic analysis of EGFR amplification.
- To establish criteria for patient inclusion in clinical trials based on EGFR expression levels.
Main Methods:
- Immunohistochemistry was performed on 55 glioblastoma cases using four different monoclonal antibodies.
- Molecular genetic analysis (differential polymerase chain reaction) of EGFR amplification was conducted on a subset of cases.
- A densitometric EGFR/Interferon-gamma (IFN-gamma) ratio >3 was used to indicate EGFR gene amplification.
Main Results:
- Four antibodies yielded comparable results for EGFR protein detection.
- EGFR gene amplification was identified in 13 of 21 analyzed specimens.
- A positive correlation was observed between the degree of EGFR gene amplification and protein expression levels.
Conclusions:
- Immunohistochemistry and molecular genetic analysis are complementary methods for assessing EGFR status in glioblastomas.
- EGFR amplification correlates with increased protein expression, supporting its role as a therapeutic target.
- These findings aid in defining patient populations for anti-EGFR antibody-based therapies.