ESTROGEN-RECEPTOR INDEPENDENT EXPRESSION OF PROGESTIN RECEPTORS IN HUMAN MENINGIOMA - A REVIEW

Human meningiomas are rich in progestin receptors (PR), which are expr essed in this tissue in an oestrogen independent fashion. In the searc h for an explanation of this observation, the existence of a protein i n human meningioma cytosol which is capable of binding to a synthetic oestrogen responsive element (ERE) has been demonstrated. Using revers e transcriptase, PCR mRNA encoding for the wild-type oestrogen recepto r (ER) was found. In addition, several splice variants of ER mRNA have been identified in human meningioma tissue, including variants lackin g exons 4, 5 and 7. We found the ER Delta 4 protein to have no transcr iptional activity and the ER Delta 7 protein reportedly is dominant ne gative. These mutants therefore probably are not responsible for the a utonomous PR synthesis in human meningioma. The ER Delta 5 protein, by contrast, has been reported to have oestrogen independent transcripti onal activity and it is tempting to speculate that this protein is sim ilar or identical to the ERE binding protein we have found in human me ningioma. The role of wild type ER mRNA is presently unclear. Activati on of other signal transduction pathways in meningioma does not lead t o an increased PR concentration. The promoter area of the meningioma P R gene should be investigated for the possible sensitivity to other tr anscription factors.