Coexpression index of estrogen receptor alpha mRNA isoforms in simple, complex hyperplasia without atypia, complex atypical hyperplasia and adenocarcinoma

Objective.Estrogen receptor isoforms are postulated to play an important role in modulating the estrogen response. To clarify the molecular mechanisms through which malignant changes are activated in endometrium, this study aims to examine the expression profiles of wild-type ER-alpha and their splice variants and to assess the number of coexisting mRNA isoforms of ER-alpha in normal endometrium as well as in endometrial hyperplasia and endometrial endometrioid adenocarcinoma.Methods.Human endometrium and specimens including endometrial hyperplasia and endometrial cancer were obtained during surgery. Endometrial data were classified into four groups: simple hyperplasia (n = 24), complex hyperplasia (n = 15), atypical hyperplasia (n = 11), endometrial endometrioid adenocarcinoma (n = 19) (grade 1, grade 2 morphological degree) and proliferative endometrium (n = 24) as a control group. Total cellular RNA was extracted from endometrial tissues using Total RNA Prep Plus. A real-time quantitative RT-PCR assay was developed to quantify the wild-type ER-alpha and ER-alpha mRNA isoforms copy numbers. We have evaluated the variation in ERs mRNA level between normal endometrium and endometrial hyperplasia and adenocarcinoma. We also evaluated the “sharing indicator”. It is a factor of mRNA ER-alpha holding shares in whole mRNA it assume quotient of ER-alpha slicing variant to all variants of mRNA ER-alpha.Results.It was found that the number of coexisting mRNA isoforms was significantly higher in adenocarcinoma endometrium than that evaluated for various degrees of hyperplasia endometrium and normal proliferative endometrium (p < 0.05, the Kruskal–Wallis test).Conclusion.The risk for progression of endometrial hyperplasia to atypical hyperplasia and eventually endometrioid adenocarcinoma may be accompanied by an increase in the number of alternative splicing variants of mRNA ER-alpha.