We examined the expression of estrogen receptor (ER) messenger RNAs (ER-α, ER-β, and ER-β isoforms) in colorectal tumor samples and corresponding normal mucosa, paying particular attention exons 3 and 5 of both ER mRNA subtypes that likely suffer deletions, and may encode proteins that have lost either DNA- or ligand-binding moieties. Then we correlated these findings with the clinicopathological properties of the tumors. Our results demonstrated that in all patients the two ER subtype mRNAs were coexpressed in wild-type form. In 10% of the patients the ER-α mRNA was also present as an exon-5-deleted form that encoded any aberrant protein. Immunohistochemical analysis revealed that the ER-β protein was present in tumor stroma, but not in infiltrating lymphocytes. ER-β1 and ER-β2, isoforms of ER-β, were up-regulated in malignant tissues, whereas the ER-β5 isoform, was found to be equally expressed; at very low levels, in the two tissue compartments. No correlations between ER levels and clinicopathological parameters were found. This suggests that the ER-β mRNA levels are independent of the tumor characteristics.
- Colorectal adenocarcinoma
- Estrogen receptor alpha
- Estrogen receptor beta
- Estrogen receptor variant form
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