Aim: To determine the expression of estrogen receptor (ER) beta in Chinese colorectal carcinoma (CRC) patients.
Methods: ERbeta expression in CRC was investigated by immunohistochemical staining of formalin-fixed, paraffin-embedded tissue sections from 40 CRCs, 10 colonic adenomas, and 10 normal colon mucosa biopsies. The percentage of positive cells was recorded, mRNA expression of ERalpha and ERbeta in 12 CRC tissues and paired normal colon tissues were detected by RT-PCR.
Results: Positive ER immunoreactivity was present in part of normal epithelium of biopsy (2/10), adenomas (3/10), and the sections of CRC tissue, most of them were nuclear positive. In CRCs, nuclear ERbeta immunoreactivity was detected in over 10% of the cancer cells in 57.5% of the cases and was always associated with cytoplasmic immunoreactivity. There was no statistical significance between ERbeta positive and negative groups in regard to depth of invasion and nodal metastases. Of the 12 CRC tissues and paired normal colon tissues, the expression rate of ERalpha mRNA in CRC tissue and corresponding normal colon tissue was 25% and 16.6%, respectively. ERbeta mRNA was expressed in 83.3% CRC tissue and 91.7% paired normal colon tissue, respectively. There was no significant difference in ERbeta mRNA level between CRC tissues and paired normal colon tissues.
Conclusion: A large number of CRCs are positive for ERbeta, which can also be detected in normal colonic epithelia. There is a different localization of ERbeta immunoreactivity among normal colon mucosae, adenomas and CRCs. ERalpha and ERbeta mRNA can be detected both in CRC tissue and in corresponding normal colon tissue. A post-transcriptional mechanism may account for the decrease of ERbeta protein expression in CRC tissues.