Research article
Estrogen receptor of primary breast cancers: evidence for intracellular proteolysis
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* Corresponding author: Guy Leclercq lcanmamm@ulb.ac.be
Institut Jules Bordet, Brussels, Belgium
Breast Cancer Res 2000, 2:444-454 doi:10.1186/bcr92
Published: 6 September 2000Abstract
Iodinated oestradiol-labeled oestrogen receptor (ER) isoforms devoid of amino-terminal ABC domains represent about two-thirds of the whole receptor population detected in cytosol samples from human breast cancers. This high frequency could not be ascribed to the expression of truncated mRNAs, or to the proteolysis of the native ER peptide at the time of homogenization or assay, suggesting an intracellular proteolysis. Free amino-terminal and ligand-binding domains maintained together within oligomeric structure(s); increase of ionic strength separated them. The amino-terminal region was consistently detected in the cell nucleus by specific immunohistochemistry leading to the concept of a potential intranuclear association between ER cleavage products and/or other regulatory proteins.