The changes of estrogen receptor-beta variants expression in breast carcinogenesis: Decrease of estrogen receptor-beta2 expression is the key event in breast cancer development.

Background And Objectives: Although more than five variant forms of estrogen receptor-beta (ERbeta) have been identified, their role has not been identified. This study was carried out to investigate the changes of ERbeta variants in breast cancer development.

Methods: Using reverse transcription polymerase chain reaction (RT-PCR) and triple primer PCR (TP-PCR), the expression levels of ERbeta variants mRNA were measured in 66 paired normal and cancer tissues. The relative expression level of ERbeta variants were compared between normal and cancer tissues, and also compared according to various clinicopathological parameters.

Results: Among ERbeta variants, ERbeta2 and ERbeta5 consist of the major proportion of ERbeta expression both in normal and cancer tissues. The ERbeta and ERbeta2 expression levels decreased significantly in the cancers compared with corresponding normal tissues, particularly in ERalpha-expressing cancers. However, ERbeta5 expression level increased significantly in the cancers, especially in those of postmenopausal patients. The relative increase of ERbeta5 expression in cancer tissues was associated with favorable differentiation.

Conclusions: Decrease of ERbeta2 is thought to be the key reason for the decrease in ERbeta expression in cancer tissues, and it is particularly associated with the development of ERalpha-expressing breast cancer.