Expression of transcription factors in endometrium during natural cycles.

PurposeThe sex steroid control of the endometrial cycle is mediated by transcription factors, four of which are the estrogen and progesterone receptors, c-jun and c-fos, all expressed by the endometrium. The aim of this study was to analyze the distribution of the transcription factors in the different endometrial compartments during natural cycles.MethodsWe studied 53 reproductively-normal women, of whom 26 were in the proliferative phase and 27 in the secretory phase. An endometrial biopsy was performed and serum values of LH, FSH, estradiol, and progesterone were determined. We studied the expression of transcription factors using monoclonal antibodies.ResultsA correlation between estrogen receptor and c-jun and c-fos expression was observed in stroma and epithelia, and progesterone receptor expression correlated with c-jun expression in epithelia. C-jun and c-fos presented greater expression in the proliferative phase than in the secretory phase, in the stroma and in both epithelia. No relation was found between estradiol serum levels and any transcription factor, but progesterone serum levels correlated significantly with most such factors.ConclusionThe two proto-oncogenes could play a decisive role in regulating the endometrial cycle; they could mediate the effects induced by sex steroid, and could be related to other transcription factors.