Clinical Implications of the Expression of Estrogen Receptor-α and -β in Primary and Metastatic Lesions of Uterine Endometrial Cancers

Abstract

Novel human estrogen receptor (ER)-β was identified in cDNA libraries from human testes. ER-β specifically expresses in the testis, ovary, thymus, spleen, osteoblasts, fetus and uterine endometrium. ER-β might not conserve the same physiological functions as does ER-α. Therefore, expressions of ER-α and ER-β mRNAs in primary and metastatic lesions of uterine endometrial cancers were investigated. The levels of ER-β mRNA were significantly lower than those of ER-α mRNA in uterine endometrial cancers and in normal uterine endometria. The ratio of ER-β to ER-α mRNA in most primary uterine endometrial cancers was similar to that in normal uterine endometria (<0.4% of ER-β mRNA to ER-α mRNA). On the other hand, in 14 of the 20 lymph node metastasis-positive cases of uterine endometrial cancers, the ratio in the metastatic lesion was significantly higher than that in the primary lesion of the corresponding case, and patient prognosis in these cases was extremely poor. Therefore, it is suggested that the intact synchronized expression of ER-β interacting with ER-α might be disrupted, especially in most metastases of uterine endometrial cancers, leading to poor patient prognosis related to estrogen refractoriness.