Differential expression of inducible nitric oxide synthase mRNA in human brain tumours

Messenger RNA encoding the inducible form of human nitric oxide synthase (iNOS) was quantified by reverse transcription and polymerase chain reaction (RT-PCR) in tissue samples from glioblastomas and meningiomas. iNOS mRNA expression was considerably higher in the glioblastoma than in the meningioma specimens (mean +/- s.e.m., 41.18 +/- 11.5, n = 25, vs 5.31 +/- 0.98, n = 21; p < 0.0001). Moreover, iNOS expression appeared as a polymorphic character among glioblastomas, as individual tumours expressed either high (n = 6), intermediate (n = 10) or low (n = 9) levels of iNOS mRNA.