Methylation of estrogen receptor beta promoter correlates with loss of ER-beta expression in mammary carcinoma and is an early indication marker in premalignant lesions.
The function of estrogen receptor beta (ER-beta) in mammary tissue is not completely understood. While early observations were often conflicting, more recent data suggest an important role as a tumor-suppressor gene. A decrease of ER-beta expression has been observed in ductal carcinoma in situ and invasive carcinoma as compared with benign mammary epithelial cells. The loss of ER-beta resulted in abnormal growth of mammary epithelial cells. We have previously shown that the mRNA expression of the ER-beta gene is almost totally suppressed in breast carcinomas from patients with a poor prognosis. Here we analyzed whether methylation changes in the different promoters of ER-beta are responsible for the loss of expression of the gene. A methylation assay with high specificity and sensitivity was developed, and a panel of breast tissue samples (n = 175) was characterized for methylation status. In contrast to benign breast, more than two-thirds of invasive breast cancers showed a high degree of methylation. Importantly, increased methylation was also detectable in numerous premalignant lesions. By analysis of breast tumors, previously characterized by gene-expression profiling, methylation was predominantly detected in a subgroup of patients with an unfavorable prognosis, suggesting a possible prognostic value of the ER-beta methylation status. We also investigated the structural characteristics of the two ER-beta promoters, which were both found to be closely associated with a second, downstream, localized and opposite-oriented promoter. However, we could not detect endogenous antisense RNA transcribed from these promoters, which may be involved in epigenetic gene silencing. We also failed to induce ER-beta promoter methylation by expressing siRNAs in cell lines. Interestingly, by comparing the promoter sequences of ER-beta with other genes known to be epigenetically inactivated in breast cancers, we identified a sequence motif possibly involved in promoter methylation.
Rody
A
A
Department of Gynecology, Johann Wolfgang Goethe University, Frankfurt, Germany.
Holtrich
U
U
Solbach
C
C
Kourtis
K
K
von Minckwitz
G
G
Engels
K
K
Kissler
S
S
Gätje
R
R
Karn
T
T
Kaufmann
M
M
D001483:Base Sequence; D014408:Biomarkers, Tumor / Q000235:genetics; D001943:Breast Neoplasms / Q000175:diagnosis / Q000235:genetics*; D002277:Carcinoma / Q000175:diagnosis / Q000235:genetics*; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000378:metabolism; D044127:Epigenesis, Genetic; D047629:Estrogen Receptor beta / Q000235:genetics* / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D008969:Molecular Sequence Data; D011230:Precancerous Conditions / Q000175:diagnosis* / Q000235:genetics; D011379:Prognosis; D011401:Promoter Regions, Genetic / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics
D014408:Biomarkers, Tumor; D004273:DNA, Neoplasm; D047629:Estrogen Receptor beta; D034741:RNA, Small Interfering