The truncated estrogen receptor alpha variant lacking exon 5 is not involved in progesterone receptor expression in meningiomas

Human meningioma tissues are mostly estrogen receptor (ER) negative and pro gesterone receptor (PR) positive in ligand binding and enzyme immune assays . To explain this apparently ER independent PR expression, we investigated the existence of a 'hidden' ER variant, which would be capable of activatin g transcription of the PR gene. Total RNA of seven meningiomas, two breast cancer tissues and of MCF7 cells was analyzed by RT-PCR using primers situa ted in exon 4 and exon 6. Differential hybridization of the PCR transcripts with probes in exon 4 and 5 respectively, revealed a wild type ER (wtER) f ragment and an exon 5 deleted ER variant (ER Delta 5). PCR products of two meningiomas were cloned for sequence analysis. The result confirmed the exi stence of a wtER and ER Delta 5. RT-PCR followed by Southern analysis was performed on mRNA of 23 meningioma s to determine the amount of ER Delta 5 relative to wtER, which was compare d to the PR content of the tissues. In contrast to our initial hypothesis a nd literature data on breast cancer, there was no relationship between the ER Delta 5/wtER ratio and PR protein concentration. It is therefore conclud ed that ER Delta 5 mRNA does not play the dominant role in PR synthesis in meningioma tissue. (C) 2000 Elsevier Science Ltd. All rights reserved.