Expression of N-ras gene in gliomas.

Expression of N-ras gene was examined by northern blot analysis in two cases of astrocytoma (grade II), four cases of glioblastoma multiforme (six samples including two recurrent tumors), and normal brain tissues. Expression of N-ras gene was only found in the two recurrent glioblastoma multiforme samples. Southern blot analysis found no significant difference in copy numbers of N-ras gene in pre- and post-recurrence samples. The histological diagnosis of the two recurrent tumors was glioblastoma multiforme at both first recurrent presentation. However, the tumors had progressed during recurrence, because of worsened histological findings, such as increased cellularity, pleomorphism, and vascularity. These tumors recurred at very short intervals. Enhanced expression of N-ras gene by disorder of transcription may be a factor in the progression of glioblastoma multiforme.