THE EPIDERMAL GROWTH-FACTOR RECEPTOR IN GLIOBLASTOMA - GENOMIC AMPLIFICATION, PROTEIN EXPRESSION, AND PATIENT SURVIVAL-DATA IN A THERAPEUTIC TRIAL

Human glioblastomas were evaluated for overexpression of the epidermal growth factor receptor (EGFR) in a therapeutic trial with the anti-EG FR antibody EMD 55900. A total of 55 cases were examined by immunohist ochemistry using 4 different monoclonal antibodies on frozen or on par affin sections: EGFR-1 (Amersham), E 62 (Merck), E 30 (Merck), and EMD 55900 (MAB 425, Merck). Definition for inclusion in clinical trials o f 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 differe nt antibodies gave essentially equal results. In 21 cases, the immunoh istochemical results were supplemented by molecular genetic analysis o f EGFR amplification on the corresponding locus of chromosome 7, using frozen tissue from the same blocks after screening for vital tumor ar eas. Since no other material was available, the differential polymeras e chain reaction technique was applied. Interferon-gamma (IFN-gamma) s erved as a reference gene. In a preliminary experimental series with c ases of known EGFR amplification, a densitometric EGFR/IFN-gamma ratio higher than 3 was determined as indicator for amplification of the EG FR gene. With this experimental approach we were able to identify an a mplified EGFR gene in 13 specimens including 2 from recurrent glioblas tomas in the same patients. All of these showed an increased immunorea ctivity for EGFR protein. The degree of EGFR amplification (EGFR/IFN-g amma ratio as measured by DNA densitometry) showed a positive correlat ion with the grade of immunohistochemical protein expression, both in regard to the fraction of positive cells and to the overall staining i ntensity. Evaluation of the survival data indicated a trend for a nega tive correlation between the survival time and the degree of EGFR ampl ification.