Quantitation of estradiol receptors alpha and beta and progesterone receptors in human breast tumors by real-time reverse transcription-polymerase chain reaction. Correlation with protein assays.

Hormone receptor content is the most useful parameter for predicting hormone response therapy in breast cancer. The high frequency of primary and secondary resistance to treatment makes it necessary to find out other parameters in order to improve the prediction of response to treatment. The newly described estrogen receptor beta (ERbeta) is a potential candidate. Using real-time quantitative RT-PCR, we evaluated estrogen receptor alpha (ERalpha), ERbeta, and progesterone receptors (PR) in comparison with ERalpha and PR protein content measured with the enzyme immunoassay (EIA), in a retrospective series of 98 breast tumors. We obtained a highly significant correlation between mRNA and EIA assays for ERalpha and PR (r=0.79 and r=0.71, respectively; P<0.001). We confirmed the low level of ERbeta mRNA transcripts in comparison to ERalpha in breast tumors. We did not find any statistically significant correlation between the absolute ERbeta mRNA level and ERalpha or PR mRNA level, and ERalpha or PR-EIA. We found a significant correlation between ERalpha mRNA and PR mRNA expressions. We did not find any correlation between ERbeta mRNA and clinical features of the patients (age, menopausal status, tumor size, and nodal status), nor with the histological type of the tumor. In conclusion, the accuracy of the present quantitative RT-PCR assay makes it suitable for a routine clinical use. In addition, the present results suggest that, ERbeta mRNA expression is independent of the classical parameters.