In situ hybridization with single-stranded RNA probes to demonstrate infrequently elevated gli mRNA and no increased ras mRNA levels in meningiomas and astrocytomas.

Using computer-assisted digital image-analysis, the level of ras and gli messenger RNA (mRNA) in neoplasms of meningeal and glial origin was determined in an attempt to correlate these parameters with histological tumor severity. We used single-stranded, asymmetric, radiolabelled RNA probes to detect the amount of ras and gli mRNA present in formalin-fixed, paraffin-embedded tumor material. Such archival material can provide an immediate, larger sample base than with fresh samples. The extent of ras mRNA expression in 25 brain tumors was not significantly different than normal cerebellum. However, five of 74 astrocytomas of relatively high malignant potential demonstrated gli mRNA levels above normal cerebellum.