The molecular biology of hormone and growth factor receptors in meningiomas

Expression of a number of steroid hormone and growth factor receptors is characteristic of meningiomas. This paper reviews the analysis of receptors for progesterone, estrogen, androgen and platelet derived growth factor (PDGF) in human meningioma tissue specimens. Progesterone receptor was assessed by Northern blot analysis and immunohistochemistry in meningioma tissue specimens. Progesterone receptor mRNA was expressed in 64% of the meningiomas examined. Immunohistochemical data correlated well with the Northern blot analysis. The staining was clearly nuclear. Expression was more common in meningioma tissue from women than from men. Analysis of receptor expression in tissue culture derived from meningioma specimens demonstrated the loss of progesterone receptor within one to two passages. It was shown that the progesterone receptor mRNA expression which is present in meningiomas is functional by transfection techniques. The estrogen receptor was undetectable by Northern blot analysis; a small amount could be detected in meningioma tissue specimens by polymerase chain reaction (PCR). The androgen receptor was found in 67% of the specimens examined. Like the progesterone receptor, it was more common in women than in men (69% vs. 31%). The immunohistochemical data correlated well with the Northern blot analysis, with the receptor predominantly found in the nucleus. Unlike progesterone receptor, androgen receptor expression was not lost in cell culture. The subunits for PDGF were expressed in various quantities in meningiomas. Only the PDGF beta-receptor (PDGFR-beta) not alpha-receptor, was found in meningioma tissue specimens. In contrast, the ligands PDGF A and PDGF B were expressed in all tumors. The functionality of the PDGF beta-R was determined by examining the induction of the protooncogene C-fos by PDGF BB in meningioma cell cultures. A significant increase in C-fos protein was observed with the addition of PDGF BB to meningioma cultures.