Analysis of estrogen receptor alpha and beta in endometrial carcinomas: correlation with ER beta and clinicopathologic findings in 45 cases.

Estrogens play important roles in the pathogenesis of the great majority of endometrial endometrioid adenocarcinoma. Recently, a novel estrogen receptor (ER), ER beta, has been characterized, but little is known about the status of ER beta in endometrial carcinoma. We therefore examined expression of both ER alpha and ER beta in 45 cases of endometrioid endometrial adenocarcinoma using mRNA in situ hybridization, reverse transcription and polymerase chain reaction (RT-PCR), and immunohistochemistry. We also correlated the findings with various clinicopathologic parameters in these cases to examine their possible biologic significance. Accumulation of mRNA hybridization signals for both ER alpha and ER beta was detected predominantly in the cytoplasm of carcinoma cells, and to a lesser extent in some stromal cells. ER beta mRNA was detected in 16/45 cases (35.6%), and ER alpha mRNA hybridization signals were detected in 36/45 cases (80.0%). Among the 16 ER beta positive cases, 15 cases also had ER alpha mRNA hybridization signals. In the cases that expressed both ER alpha and ER beta, ER alpha mRNA hybridization signals were more widely distributed than ER beta mRNA. In 21 cases, carcinoma cells had ER alpha mRNA hybridization signals but not ER beta mRNA. There was a statistically significant positive correlation between the results of mRNA in situ hybridization and semiquantitative RT-PCR or immunohistochemistry for both ER alpha and ER beta. There were no significant correlations between ER beta mRNA expression and PR labeling index, Ki67 LI, age, or histologic grade. The results from our study indicate that ER beta is coexpressed with ER alpha, and that the estrogenic effects occur predominantly through ER alpha in endometrial carcinomas.