Detection of oestrogen receptor variants in endometrium, myometrium, leiomyoma and peripheral blood mononuclear cells: comparison to variants present in breast cancer

Abstract

Oestradiol has mitogenic and regulatory effects on various organs and cells, mediated mainly by its nuclear receptor (ER). The presence of aberrant ER forms in Oestrogen-dependent tumours has been discussed in correlation with tumour progression. ER variants, generated by alternative splicing, have been detected in human breast cancer, but also in normal mammary glands, therefore their role in tumorigenesis has been questioned. We have investigated, by the use of the reverse transcription polymerase chain reaction amplification technique, the possible existence of ER variants in other normal oestrogen target organs and cells, such as uterus (myometrium and endometrium), in peripheral blood mononuclear cells and in a benign uterus tumour (leiomyoma). We have detected variant ER in these samples and have compared the variant profile to that observed in breast cancer. All tissues and cells studied expressed both wild-type ER and variant species. Variant forms encompassed ER with deletions of exons 2, 5 and 7. Variants with exon 5 deleted were detected only in peripheral blood mononuclear cells and in breast cancer. Variants with exons 2 and 7 deleted were present in all specimens tested. These results corroborate previous findings that the presence of ER variants is not a characteristic of breast cancer. The physiological significance and possible clinical relevance of the variant ER forms remain to be elucidated.

Reduced alternative splicing of estrogen receptor alpha in the endometrium of women with endometriosis

“…Our data also showed that the ERαDel.2 variant was expressed at the lowest level of all variants, and in some samples was even undetectable, even by qPCR. This finding concurs with previous studies, which found minimal levels of ERαDel.2 in a range of other tissues and conditions, including patients with Alzheimer's disease (AD) [ 19 , 22 ]. In contrast, the other ER splice variants, ERαDel.4, ERαDel.7 and ERαDel.3,4, were expressed at much higher levels.…”

Steroid Receptors in the Uterus: Implications in Endometriosis

“…ERα and ERβ exhibit high homology (96%) in their DNA binding domains, a 53% homology in their ligand binding domain, and a low homology (30%) in the AF‐1 domain. Differential splicing of the two receptor genes results in various ERα and ERβ variants, which lack certain exons 15,16. These variants are coexpressed with the wild‐type receptors in various tissues, show characteristic subcellular distribution, display an extreme reduction in ligand binding and DNA binding to EREs, and have a dominant negative effect on wild‐type ER transcriptional activity 17…”

“…Differential splicing of the two receptor genes results in various ERα and ERβ variants, which lack certain exons. 15,16 These variants are coexpressed with the wild-type receptors in various tissues, show characteristic subcellular distribution, display an extreme reduction in ligand binding and DNA binding to EREs, and have a dominant negative effect on wild-type ER transcriptional activity. 17 ERα and ERβ exhibit distinct interactions with common or specific cofactors, show differential binding to a variety of ligands, and may act by way of different response elements, exhibiting altered specificity and affinity.…”

“…3). The region of the gene encoding the aminoterminal part of AR contains CAG repeats of varying length, [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] translated in polyglutamine tracts. In addition, partly methylated islands of GC are present, methylation playing a possible role in the gene's inactivation.…”

Influence of surgical trauma on the mRNA expression of sex hormone receptors in PBMCs in male and female patients

“…These intron-spanning primers were obtained from published literature [13][14][15] or newly designed and custom-synthesized by Metabion GmbH (Martinsried/Germany). The samples were amplified in 50 μl of PCR mixture containing 1×Taq DNA Polymerase buffer, 0.2 mM dNTP mix (Roche), 1 U Taq DNA Polymerase (Roche), and 1 μM each of forward and reverse primers.…”