Assessment of Hypermethylated DNA in Two Promoter Regions of the Estrogen Receptor α Gene in Human Endometrial Diseases

Abstract

Objective. DNA methylation in the promoter regions of many genes is associated with the regulation of gene expression. We examined the frequency of DNA hypermethylation at two nucleotide positions, the proximal promoter region (PPR) in exon 1 and the distal promoter region (DPR) in exon 1′, of the estrogen receptor α (ERα) gene in 111 cases of various human endometrial diseases.Methods. The degree of hypermethylation of PPR and DPR was examined by semi-quantitative competitive polymerase chain reaction assay using restriction enzymes (HpaII, NotI, and SacII).Results. Endometrial tissues in the proliferative phase obtained from patients with leiomyomas and/or adenomyosis and no significant hormonal abnormalities did not show hypermethylation at the HpaII cleavage position of DPR. In 6 of 16 (37.5%) cases of simple endometrial hyperplasia, the PPR was hypermethylated, whereas in cases of atypical endometrial hyperplasia and endometrioid adenocarcinoma the frequencies were extremely low. Hypermethylation of these promoter regions did not correlate with lack of ERα protein in the 46 cases that were analyzed by enzyme immunoassay.Conclusions. ERα gene transcription from the distal promoter, rather than from the proximal promoter, is predominant in the proliferative phase of the normal menstrual cycle, because the PPR, but not the DPR, is frequently hypermethylated under those conditions. Conversely, ERα gene transcription from the proximal promoter is predominant in precancerous lesions such as atypical hyperplasia and endometrial cancer. However, hypermethylation at the promoter sites we examined was not related to the loss of ERα protein in endometrial disease.