Aims: We aimed to investigate the sources of estrogen receptor alpha (ERalpha), estrogen receptor beta (ERbeta) and estimate the value of both ER subtypes in gastric adenocarcinoma and analyze the possible relationship of prothymosin alpha (ProTalpha) to ERs.
Methods: ERs at the mRNA and protein levels in matched advanced gastric adenocarcinomas and surrounding non-cancerous tissues were examined by using reverse transcription-polymerase chain reaction and immunohistochemical (IHC) methods. Cell proliferation related protein ProTalpha was also detected in IHC. The immunoreactive signal, corresponding to the proteins expression level, was quantitatively analyzed.
Results: Both ERalpha and ERbeta mRNAs were detected in most of the cancer and matched normal tissues analyzed. At the protein level, the percentage of ERalpha and ERbeta positive cases changed. ERalpha immunoreactivity was only detected in poorly differentiated adenocarcinoma and ERalpha positive expression correlated with depth of invasion of the tumors. Compared with non-cancerous tissues, gastric tumors showed decreased ERbeta expression and lost ERbeta. Altered ERbeta in gastric adenocarcinoma correlated with decreased differentiation. And the tumors involved lymph node metastasis showed significantly lower expression level of ERbeta. ProTalpha in ERbeta-positive tumors showed higher expression than that in lost ERbeta tumors.
Conclusions: Altered expression of ERalpha and ERbeta in tumors compared with corresponding normal gastric tissues was more common in poorly differentiated adenocarcinomas and related to malignant properties, such as lymph node metastasis. Decreased ERbeta and increased ProTalpha expression in advanced gastric adenocarcinoma indicated that ERbeta may play an anti-proliferation role which is opposed to the role of ProTalpha in gastric epithelium.