Overexpression of n-ras oncogene and epidermal growth factor receptor gene in human glioblastomas

Five human glioblastoma cell lines were analyzed for oncogene activation with a panel of probes. Abnormal expression of the epidermal growth factor receptor (EGFr) gene was detected in four of five lines; N-ras oncogene overexpression was found in all five cell lines. These results were subsequently confirmed with fresh brain tumor and nonneoplastic brain tissue biopsy samples; increased expression of the N-ras proto-oncogene was observed in five of five glioblastomas, all of which also showed EGFr gene overex-pression, but not in well-differentiated gliomas or in nonneoplastic brain tis-sue specimens. No significant differ-ences in Ha-ras and Ki-ras expression were observed. Preliminary histochem-ical observations showed that intra-cellular levels of transforming growth factor α, a putative biochemical link between these two oncogenes, were significantly higher in glioblastoma cells than in controls.