Amplification and expression of the epidermal growth factor receptor gene during the progression of neuroepithelial tumours in vivo.
The epidermal growth factor receptor (EGFR) gene is homologous to the oncogene c-erbB. The occurrence of amplification and rearrangements at the EGFR gene locus is associated with malignancy in neuroepithelial tumours. Sixteen neuroepithelial tumours from eight patients with recurrence of their neoplasms were analysed for changes at the EGFR gene locus and for expression of EGFR. Ten tumours from five patients lacked changes at the EGFR gene locus. Three of eight individuals showed EGFR gene amplifications in both tumours with a higher grade of amplification in the second tumour. In addition to amplification, a rearrangement was found in both tumours of the first patient. In the second case an amplification of chromosome-7-specific c-met sequences was found in the regrown tumour, suggesting that a polysomy 7 was at least partly responsible for the higher copy number of the EGFR sequences. In both tumours of the third patient with EGFR gene amplification different alleles were amplified. In contrast to the findings at the DNA level the EGFR expression, analysed by immunohistochemical techniques, showed a more heterogeneous pattern after tumour progression.