Amplification and/or Overexpression of Platelet-derived Growth Factor Receptors and Epidermal Growth Factor Receptor in Human Glial Tumors

Analysis of genomic organization and expression of platelet-derived growth factor receptors (PDGFR) and epidermal growth factor receptor (EGFR) in human malignant gliomas showed amplification and overexpression of both receptors in distinct subsets of tumors. Amplification of the aPDGFR was detected in 4 of 50 glioblastomas (8%). EGFR was amplified in 9 of the 50 tumors (18%). Western blot analysis showed elevated expression of aPDGFR and EGFR proteins in 4 (24%) and 3 (18%), respectively, of 17 tumor specimens analyzed. Increased production of aPDGFR as well as EGFR proteins was observed in the presence or absence of gene amplification. Three of the 4 tumors with elevated levels of aPDGFR also overexpressed the 0PDGFR, which was present as a single copy gene in all 50 tumors analyzed. Our findings suggest that the amplification and/or overexpression either of EGFR or of the aPDGFR along with the coordinate overexpression of the 0PDGFR can contribute to the malignant phenotype of distinct subsets of human glioblastoma.