Estrogen Receptor Alpha (ER-α) and Beta (ER-β) mRNAs in Normal Ovary, Ovarian Serous Cystadenocarcinoma and Ovarian Cancer Cell Lines: Down-Regulation of ER-β in Neoplastic Tissues

Abstract

The prognosis in ovarian carcinoma, the most lethal of the gynecologic neoplasms, is poor and has changed little in the last three decades. Only a small number respond to antiestrogen therapy, although the classic estrogen receptor, ER-alpha, has been identified in ovarian surface epithelium, from which approximately 90% of ovarian cancers originate. We have previously shown that ER-beta mRNA is most abundant in human fetal ovaries, suggesting that it might play an important role in ovarian development. Therefore, we investigated the mRNA levels of both ERs in normal ovaries, ovarian serous cystadenocarcinomas, granulosa cells from patients undergoing in vitro fertilization (IVF), the ovarian surface epithelium cell line IOSE-Van, and the ovarian cancer cell lines SKOV3, HEY and OCC1. Northern blots of normal and neoplastic ovaries were hybridized with an ER-beta riboprobe that spans the A/B domain. We detected two major hybridizing bands at approximately 8 and 10 kb. An RNase protection assay using the same probe revealed a single band of the expected size. Hybridizing the same blot with an ER-alpha riboprobe showed a strong hybridizing band at approximately 6.5 kb. In ovarian cancer samples, ER-beta mRNA level was decreased when compared to normal ovaries. Using 25 cycles of RT-PCR followed by Southern blotting, we found equal amounts of ER-alpha and -beta mRNAs in normal ovaries in all age groups from 33 to 75 years; however, in ovarian cancer tissue, the level of ER-alpha mRNA was similar or slightly higher, comparable to 10(3) to 10(4) copies of plasmid DNA, but ER-beta mRNA levels were markedly decreased. Granulosa cells from IVF patients expressed high levels of ER-beta mRNA. The OSE cell line expressed a low level of ER-alpha, detectable after 40 cycles of RT-PCR and no ER-beta mRNA. SKOV3 showed a low level of ER-alpha and -beta mRNAs, whereas OCC1 showed a low level of ER-beta and a relatively high level of ER-alpha. HEY did not contain detectable amounts of either ER after 40 cycles of RT-PCR. We found no evidence of differential splicing or major deletions in almost the entire coding region of ER-beta in either normal ovaries or tumor samples.

Changes in Expression of Estrogen Receptors α and β in Relation to Progesterone Receptor and pS2 Status in Normal and Malignant Endometrium

“…In addition, equal or increased ERα mRNA expression in conjunction with a decreased ERβ mRNA expression indicates differential roles for ERα-and ERβ-driven pathways during breast and ovarian tumorigenesis. 7,8) In our results, Wt ERα mRNA showed a stepwise decrease from normal or G1 through to G3 tumors, in line with changes in the protein expression determined by both immunohistochemistry and western blot assay, in contrast to Wt ERβ mRNA or protein expression, which did not alter. It is therefore suggested that changes in the ratio of two ER subtypes may cause alteration in estrogen signaling pathways during endometrial tumorigenesis.…”

“…6) Although changes in the expression of two ER subtypes have been documented during breast and ovarian tumorigenesis, 7,8) little is known about the endometrial carcinoma case.…”

“…4,5) Recently, a novel ERβ subtype has been discovered in human, rat, and mouse tissues, with a high degree of conservation of the DNA-binding domain (96%), and of the ligand-binding domain (58%), as compared to the amino acid sequence of the ERα protein. 6) Although changes in the expression of two ER subtypes have been documented during breast and ovarian tumorigenesis, 7,8) little is known about the endometrial carcinoma case.…”

Targeting estrogen receptor subtypes (ERα and ERβ) with selective ER modulators in ovarian cancer

“…In 1996, a new ER (ERb) was discovered and was found to be genetically distinct from the classical ER (ERa) (Kuiper et al 1996). Since then, ERb has been found in most estrogen-target tissues such as the prostate (Weihua et al 2001) and the ovary (Brandenberger et al 1998). Reduced levels of ERb mRNA expression were found in malignant tissues compared with normal tissues in various estrogendependent tumors such as breast, prostate, and ovarian cancers (Iwao et al 2000, Horvath et al 2001, Skliris et al 2003, Chan et al 2008, indicating that the loss of ERb expression may be involved in carcinogenesis.…”

Estrogen induction and overexpression of fibulin-1C mRNA in ovarian cancer cells

“…Hillier et al (1998) have recently shown that both ERa and ERb are expressed in human normal ovarian surface epithelial cells in culture. Others and we have shown an increase in the ERa:ERb mRNA ratio in ovarian cancers compared to normal ovaries, suggesting the possible involvement of ERa-related genes in ovarian tumor progression Brandenberger et al, 1998;Rutherford et al, 2000).…”