| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
BRIEF REPORT |
in Human Endometrial Cancer
Department of Obstetrics and Gynecology, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kyoto 602-8566, Japan
Address all correspondence and requests for reprints to: Dr. Yoshiyuki Kinoshita, Department of Obstetrics and Gynecology, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan. E-mail: ykino{at}koto.kpu-m.ac.jp.
| Abstract |
|---|
|
|
|---|
(ERR
) is an orphan member of the nuclear receptor superfamily that is closely related to estrogen receptor
(ER
). ERR
binds an estrogen response element (ERE), directly competes with ER
for binding ERE, and represses ERE-dependent transcription in MCF-7 cells, ER-positive breast cancer cells.
Objective: We investigated whether ERR
modulate some ER-dependent activities in endometrial cancer.
Method: We investigated protein and mRNA expression of ERR
in endometrial cancer using immunohistochemistry and RT-PCR, respectively. After transient transfection using the ERR
expression vector (pCI-ERR
) or ERR
Si, which suppressed the expression of endogenous ERR
, Ishikawa cells were assayed for ERE-dependent luciferase activity. Cells stably overexpressing ERR
were generated and compared with estrogen-dependent and -independent cell growth.
Result: ERR
was detected in human endometrial cancer tissues by immunohistochemistry. An RT-PCR study showed that mRNA of ERR
was expressed in four endometrial cancer cell lines (Ishikawa, Hec1a, KLE, and SNGII) and 11 human endometrial tissues. Overexpression of ERR
repressed estrogen-induced ERE-dependent transcriptional activity in Ishikawa cells. After transfection with ERR
Si1, the expression of endogenous ERR
decreased to 0.5-fold, and estrogen-induced ERE luciferase activity increased to 1.5-fold. The cells stably overexpressing ERR
grew up more slowly than control cells in the presence of 10 nM estradiol.
Conclusion: ERR
is expressed in human endometrial cancer tissues and cell lines and suppresses ERE-dependent transcriptional activity in the presence of estrogen. ERR
modulates estrogen-induced activity in estrogen-dependent endometrial cancer.
| Introduction |
|---|
|
|
|---|
(ERR
) was the first orphan receptor found to share significant sequence similarity to estrogen receptor
(ER
) (2, 3). ERs activate transcription in a ligand-dependent manner, but ERRs do not bind natural estrogen (2).
Estrogens are well known as a growth factor in hormone-dependent cancer, such as breast cancer and endometrial cancer (4, 5). The biological effect of estrogens is mediated by direct interaction of the ER with DNA at the estrogen response element (ERE). In previous studies ERRs were found to bind to the ERE and modulate the transcription of several genes in the absence of estrogen. Because ERR
and ER
share common target genes, ERR
is also thought to modify the activational effect of estrogens on a number of gene promoters both by direct DNA binding competition (6, 7, 8) and through direct interaction between ER and ERR
(9). ERR
competes with ER
for binding to the ERE and inhibits ERE-dependent transcription in ER-positive MCF-7 cells, suggesting that initiation of ERE-dependent gene expression depends on the ratio of ERR
to activated ER
in the cells (8).
ERR
mRNA is expressed in a variety of cells and tissues. ERR
mRNA is expressed and ERR
immunoreactivity is associated with a poor prognosis in breast cancer (10, 11). ERRs play important roles in some types of breast cancer by modulating or substituting for ER-dependent activities. However, the expression of ERR
in human endometrial cancer tissues has not been investigated, and its function remains unknown. Therefore, in this study we investigated the expression of ERR
in endometrial cancer cell lines and tissues and the function of ERR
in ER-positive Ishikawa endometrial cancer cells.
| Materials and Methods |
|---|
|
|
|---|
Ishikawa cells, Hec1a cells, KLE cells, and SNG-II cells are all human endometrial cancer cells. KLE cells were purchased from American Type Culture Collection (Manassas, VA), and SNG-II cells were obtained from Health Science Research Resources Bank (Osaka, Japan). MCF-7 cells, a human breast cancer cell line, were a gift from the Cell Resource Center for Biomedical Research (Institute of Development, Aging, and Cancer, Tohoku University, Tohoku, Japan) and were cultured in RPMI 1640 medium. Ishikawa cells were cultured in MEM, Hec1a cells in McCoys 5a medium, KLE cells in DMEM/Hams F-12, and SNGII cells in Hams F-12, respectively.
Plasmid
The ERR
expression plasmid was constructed by inserting the full-length human ERR
gene, amplified from pSG5-ERR
by PCR, into the pCI-neo vector plasmid that has the neomycin-resistance gene (Promega Corp., Madison, WI) at the EcoRI site. The plasmids pSG5-ERR
, pCI-ER
, and pGL3(ERE)3-luciferase (ERE-Luc) were provided by Dr. Shiuan Chen (Beckman Research Institute of the City of Hope, Duarte, CA) (12, 13, 14, 15, 16, 17, 18), and pRL-CMV was purchased from Promega Corp.
For the suppression of endogenous ERR
, we prepared three kinds of small interfering RNA expression plasmid, ERR
Si1, ERR
Si2, and ERR
Si3; piGENE vector plasmid (iGENE, Therapeutics, Inc., Ibaraki, Japan) was used as a control. The pcRURU6 I cassette vector (iGENE) was used for interfering endogenous ERR
according to the manufacturers protocol (Takarabio, Inc., Kyoto, Japan). The pcRURU6 i cassette vector contains a human U6 promoter, a puromycin resistance gene, and two BspMI sites, which are used as sites for cloning a short hairpin sequence. The target sequences of ERR
Si1, ERR
Si2, and ERR
Si3 were 5'-GGAGTATGTTCTACTAAAG-3', 5'-AGAGGAGTATGTTCTACTA-3', and 5'-GCAGAAACCTATCTCAGGG-3', respectively.
Tissues and immunohistochemistry
Nine specimens of endometrial cancer tissue were obtained from 19992003 at Kyoto Prefectural University of Medicine Hospital (Kyoto, Japan). Nine cancer patients (mean age, 62 yr; range, 5275) did not receive chemotherapy or radiation therapy before surgery. Informed consent was obtained from all patients. All specimens were fixed with 10% formalin and embedded in paraffin wax.
Mouse monoclonal antibody for ERR
was purchased from Perseus Proteomics, Inc. (Tokyo, Japan); the dilution was 1:125 (11). The EnVision+ kit (DakoCytomation, Copenhagen, Denmark) was used for immunohistochemical analysis. The antigen-antibody complex was visualized with 3,3'-diaminobenzidine solution and counterstained with hematoxylin. According to a previous report (11), the ERR
labeling index was determined, and values above 10% were considered ERR
positive.
RT-PCR analysis
All endometrial cancer samples were collected after surgery in 2003 or 2004 at Kyoto Prefectural University of Medicine Hospital. Eleven patients (mean age, 53.3 yr; range 3374) did not receive any therapy before surgery. Informed consent was obtained from all patients.
Total mRNA were isolated from five cell lines and 11 tissue specimens by the acid guanidinium phenol chloroform method using Sepasol-RNA I (Nacalai Tesque, Inc., Kyoto, Japan). RT-PCR was performed using ReverTra Ace and rTaq DNA polymerase (Toyobo Co. Ltd., Osaka, Japan). The sequences of the oligonucleotide primers and the amplicon sizes were as follows: ER
forward primer, 5'-GCCAAGGAGACTCGCTACTGT-3'; and reverse primer, 5'-TCCAGAGACTTCAGGGTGCT-3' (875-bp amplicon); ERR
forward primer, 5'-TGGTCCAGCTCCCACTCGCT-3'; and reverse primer, 5-'TGAGACACCAGTGCATTCACTG-3' (483-bp amplicon); and glyceraldehyde-3-phosphate dehydrogenase (G3PDH) forward primer, 5'-TGAAGGTCGGAGTCAACGGATTTGGT-3'; and reverse primer, 5'-CATGTGGGCCATGAGGTCCACCAC-3' (983-bp amplicon). G3PDH was used as an internal PCR control.
Transient transfection and luciferase assay
Before transfection, cells were cultured in phenol red-free RPMI 1640 with 2.5% dextran-coated charcoal-treated FBS for more than 48 h. Transient transfections were performed in 24-well plates using Lipofectamine reagent (Invitrogen Life Technologies, Inc., Carlsbad, CA). After 6 h of transfection, the medium was replaced with fresh medium containing dimethylsulfoxide (DMSO) or 10 nM estradiol (E2). After 36 h, the cells were lysed, and the lysates were assayed for luciferase activity with the Dual-Glo Luciferase Assay System (Promega Corp.). When it was necessary to suppress endogenous ERR
, 5% TCX (Celox Laboratories, Inc., St. Paul, MN), a serum replacement, was used.
Generation of Ishikawa stably expressing ERR
and cell growth assay
Ishikawa cells were transfected with pCI-neo (control) or pCI-ERR
. A transfected cell was cloned, and individual colonies were picked up and numbered. Semiquantitative RT-PCR analysis of ERR
was performed, and the signal intensities of the PCR products were quantified by a gel documentation program, Scion Image (Scion Co., Frederick, MD). The most ERR
-expressing colony clone was cultured for 3 months in the presence of 600 µg/ml G418 (neomycin; Nacalai Tesque). Cells (5 x 103) were placed in each plate, cultured in the presence or absence of 10 nM E2, trypsinized, and counted with a hemocytometer.
| Results |
|---|
|
|
|---|
was strongly detected in two thirds of cancer tissue specimens (Fig. 1A
|
was expressed in all endometrial cancer tissue specimens, and ER
mRNA was expressed in 10 of the 11 endometrial cancer tissue specimens (Fig. 1B
mRNA was detected in all human endometrial cancer cell lines, and both ER
mRNA and ERR
mRNA were expressed in Ishikawa cells.
In the ERR
transiently overexpression experiment, E2 increased ERE-dependent activity by 7-fold compared with DMSO treatment in cells transfected with PCI-neo vector. In contrast, E2 increased this ERE-dependent activity by only 3-fold in the cells transfected with ERR
(Fig. 1D
). It is suggested that ERR
repressed estrogen-induced transcriptional activity in ER-positive Ishikawa cells.
ERR
Si1 decreased the levels of endogenous ERR
to half compared with controls (Fig. 2A
). After transfection with ERR
Si1, ERE-dependent transcriptional activity was decreased in the absence of E2 and serum. In contrast, E2-induced ERE reactivity was increased to 1.5-fold (Fig. 2B
). Suppressing endogenous ERR
decreased E2-independent, ERE-dependent transcriptional activity, but enhanced E2-induced, ERE-dependent transcriptional activity. ERR
clone 4 cells stably overexpressing ERR
expressed ERR
mRNA at levels 1.5-fold higher than control (neo) values (Fig. 2C
). Ishikawa ERR
clone 4 cells grew more slowly than control (neo) cells in the presence of E2 (Fig. 2D
).
|
| Discussion |
|---|
|
|
|---|
is expressed in endometrial cancer tissue at both mRNA and protein levels. Immunoreactivity for ERR
was detected in two thirds of cancer tissue specimens, and ERR
mRNA was detected in all endometrial cancer tissue specimens and cell lines. The expression of ERR
was very high in endometrial cancer. Suzuki et al. (11) detected ERR
immunoreactivity in 55% of breast cancers and found that it was associated with ERR
mRNA levels and positively associated with ER
status. It was suggested that the expression of ERR
in endometrial cancers is higher than that in breast cancers. Although a higher level of ER leads to a better prognosis and treatment of breast cancer, ERR
was associated with a poor prognosis. In our study there is no association between the expression of ERR
and that of ER
, but the relationships among these factors and the association with prognosis in endometrial cancer are not clear.
ERRs bind to the ERE and modulate the transcription of at least several genes, such as pS2 (10), aromatase (12, 13, 14), and lactoferrin (9, 19), in the absence of estrogen, but ERR
activity depends on a serum compound that is removed by charcoal treatment, which, according to previous report (20), suggests the existence of a regulating factor present in serum. In this study to identify the function of endogenous ERR
in endometrial cancer cells, we used a serum replacement for the suppressing study. Transient transfection with ERR
Si1 suppressed the expression of endogenous ERR
in Ishikawa cells and decreased ERE-dependent transcriptional activity in the absence of estrogen. This implies that endogenous ERR
had already activated ERE in the absence of serum and estrogen. Furthermore, estrogen-induced ERE luciferase activity was increased by the suppression of endogenous ERR
. In addition, the overexpression of ERR
repressed estrogen-induced, ERE-dependent transcriptional activity. It was also reported that both ER
and ERR
directly compete for binding to EREs and down-modulate the transcriptional response to estrogen in an ERE-dependent manner (7, 8). Our data support the hypothesis that endogenous ERR
suppresses ER-dependent estrogen-induced, ERE-dependent transcriptional activity in endometrial cancer as well as breast cancer. Using an ERR
expression plasmid, we found that cells stably overexpressing ERR
grew more slowly than control cells in the presence of estrogen. ERR
, therefore, functions as a repressor of the ER
-dependent promoter in ER
-positive cells in the presence of estrogen. ERR
operates as an activator or repressor of ERE-dependent transcription based upon other properties of the cell.
In summary, we have shown that ERR
is expressed in endometrial cancers, and that the transcriptional function of ERR
involves binding to an ERE. ERR
immunoreactivity was detected in many endometrial cancer tissue specimens, but it is not clear whether the expression of ERR
is associated with endometrial carcinogenesis, because data from normal endometrium were not investigated. ERR
down-modulated estrogen-induced, ERE-dependent transcriptional activity in ER-positive endometrial cancer cells, and the cells stably overexpressing ERR
grew more slowly than control cells in the presence of estrogen. It is suggested that ERR
regulated cell growth differently in the absence and presence of estrogen in endometrial cancer.
| Footnotes |
|---|
First Published Online February 7, 2006
Abbreviations: DMSO, Dimethylsulfoxide; E2, estradiol; ER, estrogen receptor; ERE, estrogen response element; ERR
, estrogen-related receptor
; G3PDH, glyceraldehyde-3-phosphate dehydrogenase; NR, nuclear hormone receptor.
Received September 6, 2005.
Accepted January 27, 2006.
| References |
|---|
|
|
|---|
1 functionally binds as a monomer to extended half-site sequences including ones contained within estrogen-response elements. Mol Endocrinol 11:342352
and estrogen receptor-related receptor
1 compete for binding and coactivator. Mol Cell Endocrinol 172:223233[CrossRef][Medline]
1 actively antagonizes estrogen receptor-regulated transcription in MCF-7 mammary cells. J Biol Chem 277:2482624834
in human breast carcinoma as a potent prognostic factor. Cancer Res 64:46704676
-1 orphan receptor. Cancer Res 58:56955700
-1 orphan receptor. Cancer Res 59:45194524
. Cancer Res 63:35463555
-1. J Biol Chem 276:2846528470
1 interacts with coactivator and constitutively activates the estrogen response elements of the human lactoferrin gene. J Biol Chem 275:2083720846
(estrogen receptor-related receptor-
). Mol Endocrinol 13:764773
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |