Retinoic acid receptor α1 isoform is induced by estradiol and confers retinoic acid sensitivity in human breast cancer cells (original) (raw)
Related papers
Journal of Cellular Biochemistry, 1993
We and others have shown previously that retinoic acid (RA) selectively inhibits the growth of estrogen receptor (ER)–positive human breast carcinoma (HBC) cells and ER-negative cells are refractory to RA inhibition of growth. The ER-negative cells inherently express lower levels of RARα and retinoic acid response element (RARE)–mediated RA-induced CAT activity. In this study we report that when ER-negative MDA-MB-231 cells were transfected with the ER gene they not only expressed higher levels of RARα and RARE-mediated RA-induced CAT gene expression, but their growth was now inhibited by RA. Estrogen enhanced RARα gene expression not only in established ER-positive cell lines but also in ER-transfected MDA-MB-231 cells. The estrogen effect appears to be direct and at the gene transcription level since it did not alter the stability of RARα mRNA and cycloheximide failed to block estrogen-mediated enhancement of RARα gene expression. Our data strongly suggest that ER-mediated enhancement of RARα levels plays an important role in RA inhibition of HBC growth. In addition, we also report here that HBC cells appear to express a unique isoform(s) of RARα which was detected only when the full-length RARα cDNA was used as a probe; the RARα1 and RARα2 specific probes failed to hybridize with the HBC specific RARα message.
1995
Estrogen receptor (ER)-positive human breast carcinoma (HBC) cell lines express significantly higher levels of retinoic acid receptor alpha (RAR alpha) (isoform 1) mRNA than ER-negative HBCs. Estradiol enhances RAR alpha mRNA expression in different ER-positive HBCs by 2-3-fold, which in turn results in increased sensitivity of ER-positive HBCs to the growth inhibitory effects of retinoic acid. To investigate the regulatory mechanisms of estradiol-mediated enhancement of RAR alpha mRNA expression, the functional promoter for the human RAR alpha isoform 1 was cloned and used to assess estradiol-mediated promoter-dependent enhancement of firefly luciferase reporter gene activity in transiently transfected ER-positive (MCF-7 and T47D) and ER-negative (MDA-MB-231) HBCs. Deletional promoter constructs were obtained to further delineate the promoter region responsible for estradiol-mediated enhancement of promoter activity. Here, we present evidence that approximately 130 bp of the promot...
Cooperative interaction between retinoic acid receptor- and estrogen receptor in breast cancer
Genes & Development, 2010
Retinoic acid receptor-α (RARα) is a known estrogen target gene in breast cancer cells. The consequence of RARα induction by estrogen was previously unknown. We now show that RARα is required for efficient estrogen receptor-α (ER)-mediated transcription and cell proliferation. RARα can interact with ER-binding sites, but this occurs in an ER-dependent manner, providing a novel role for RARα that is independent of its classic role. We show, on a genome-wide scale, that RARα and ER can co-occupy regulatory regions together within the chromatin. This transcriptionally active co-occupancy and dependency occurs when exposed to the predominant breast cancer hormone, estrogen—an interaction that is promoted by the estrogen–ER induction of RARα. These findings implicate RARα as an essential component of the ER complex, potentially by maintaining ER–cofactor interactions, and suggest that different nuclear receptors can cooperate for effective transcriptional activity in breast cancer cells.
The Journal of Steroid Biochemistry and Molecular Biology, 2003
Transcriptional cross-talk exists between the estrogen receptor (ER␣) and retinoic acid receptor (RAR) pathways in human breast cancer cells. We have previously shown that re-expression of ER␣ in ER-negative cells stimulates the transcriptional and growth inhibitory effects of all-trans-retinoic acid (tRA) by a mechanism that is independent of the ER ligands estradiol and tamoxifen. In this study, we generated cell lines stably expressing ER␣-deletion mutants to elucidate the mechanism whereby ER␣ modulates RAR transcriptional activity. Using RT-PCR and RNAse protection assays, we observed that expression of ER␣ suppresses basal expression of the RA-responsive gene RAR2, while allowing it to be strongly induced by tRA. Repression of basal RAR2 transcription was confirmed by transient expression of the reporter plasmid RE-tk-CAT, containing the RAR2 promoter. In the ER␣-negative cells, on the other hand, transcription was only weakly induced by RA. We further determined that this effect of ER␣ on RAR induction required the N-terminal AF-1-containing region, including the DNA-binding domain, but was independent of the C-terminal ligand-binding domain. Consistent with these results, the ER agonist estradiol and the AF-2 antagonist 4-hydroxytamoxifen had no significant effect on RARE activity. Conversely, the full ER antagonist ICI 182,780, which blocks ER␣ AF-1 activity, was able to completely relieve repression of basal RARE activity. The effect of ER␣ is specific for RAR-mediated transcription and does not occur on promoters containing typical response elements for the Vitamin D or thyroid hormone receptors. Moreover, the cross-talk between ER␣ and RAR does not seem to be mediated by sequestration of a number of common co-regulators, suggesting a novel mechanism whereby the N-terminal region of ER␣ modulates the transcriptional activity of RAR. (W.H. Miller Jr.). tain two independent transactivation functions (AFs). The N-terminal AF-1 domain, in the A/B region of the receptor, provides basal activity in the absence of ligand, whereas the C-terminal AF-2 domain, located in region E, is dependent on binding of ligand to the receptor. In order to activate transcription via the AF-1 and AF-2 domains, the receptor also requires binding to a response element in the promoter of specific genes, via its C-domain [1-3].
Breast Cancer Research and Treatment, 1999
To elucidate the role of RAR-dependent gene transcription in inhibiting breast cell growth, we have investigated the ability of retinoids to suppress growth of normal, immortal, and malignant breast cells. We compared the ability of all trans retinoic acid (atRA) to activate retinoid receptors in normal, immortal, and malignant breast cells, with its ability to inhibit the growth of these cells. Our studies demonstrate that normal breast cells are more sensitive to the growth inhibitory effect of atRA than are immortal nonmalignant breast cells and breast cancer cells. atRA activated RAR-dependent gene transcription in both atRA-sensitive and-resistant breast cells as determined by transfection of a RARE-containing reporter gene. These results demonstrate that activation of RAR-dependent gene transcription by atRA is not sufficient to inhibit growth in atRA-resistant breast cancer cells. To determine whether activation of RAR-dependent gene transcription by atRA is necessary for growth inhibition, we tested the growth suppressive effect of a retinoid (BMS453) which binds RAR receptors and transrepresses AP-1 but does not activate RAR-dependent gene expression. This retinoid inhibited the growth of normal breast cells (HMEC and 184) and T47D breast cancer cells. Breast cancer cells which were resistant to atRA, were also resistant to BMS453. Normal human breast cells were most sensitive to the anti-proliferative effects of BMS453. These results indicate that in some breast cells RAR-dependent transactivation is not necessary for retinoids to inhibit growth. Instead, retinoids may suppress growth by inhibiting transcription factors such as AP-1 through transcription factor crosstalk.
Estrogen-Induced Retinoic Acid Receptor α1 Gene Expression: Role of Estrogen Receptor-Sp1 Complex
Molecular Endocrinology, 1998
Retinoic acid receptor ␣1 (RAR␣1) gene expression is induced by 17-estradiol (E 2) in estrogen receptor (ER)-positive breast cancer cells, and the ؊100 to ؊49 region of the RAR␣1 gene promoter was previously shown to be required for E 2responsiveness. This region of the RAR␣1 promoter was further analyzed using the following oligonucleotides: ؊100 to ؊49 (RAR4); ؊79 to ؊56 (RAR3); ؊79 to ؊49 (RAR2); ؊100 to ؊58 (RAR1); and their derived promoter reporter constructs (pRAR4, pRAR3, pRAR2, and pRAR1). In transient transfection studies in MCF-7 human breast cancer cells, pRAR2 and pRAR1 were E 2-responsive; both of the RAR␣1 gene promoter inserts contained two GC-rich sites and bound Sp1 protein in gel mobility shift assays. Using wild-type [ 32 P]RAR2 and oligonucleotides mutated in one or both GC-rich sites, it was shown that ER enhanced Sp1 binding to both sites, but a ternary ER-Sp1-DNA complex was not observed in gel mobility shift assays. In transient transfection assays, each of the GC-rich motifs were sufficient for E 2-induced transactivation. In ER-negative MDA-MB-231 cells transiently transfected with pRAR2, E 2 responsiveness was observed only in cells cotransfected with wild-type ER or 11C-ER containing a deletion of the DNA-binding domain but not with ER variants that express activation function-1 (AF-1) or AF-2. Using a similar approach, it was shown that the GC-rich sites in RAR1 were also sufficient for ER activation. These results demonstrate that interaction of a transcriptionally active ER/Sp1 complex with GCrich motifs is required for hormone inducibility of the downstream region of the RAR␣1 gene promoter. (Molecular Endocrinology 12: 882-890, 1998)
Molecular Endocrinology, 2005
The identification of estrogen receptor (ER␣) target genes is crucial to our understanding of its predominant role in breast cancer. In this study, we used a chromatin immunoprecipitation (ChIP)-cloning strategy to identify ER␣-regulatory modules and associated target genes in the human breast cancer cell line MCF-7. We isolated 12 transcriptionally active genomic modules that recruit ER␣ and the coactivator steroid receptor coactivator (SRC)-3 to different intensities in vivo. One of the ER␣-regulatory modules identified is located 3.7 kb downstream of the first transcriptional start site of the RARA locus, which encodes retinoic acid receptor ␣1 (RAR␣1).
EMBO molecular medicine, 2015
Forty-two cell lines recapitulating mammary carcinoma heterogeneity were profiled for all-trans retinoic acid (ATRA) sensitivity. Luminal and ER(+) (estrogen-receptor-positive) cell lines are generally sensitive to ATRA, while refractoriness/low sensitivity is associated with a Basal phenotype and HER2 positivity. Indeed, only 2 Basal cell lines (MDA-MB157 and HCC-1599) are highly sensitive to the retinoid. Sensitivity of HCC-1599 cells is confirmed in xenotransplanted mice. Short-term tissue-slice cultures of surgical samples validate the cell-line results and support the concept that a high proportion of Luminal/ER(+) carcinomas are ATRA sensitive, while triple-negative (Basal) and HER2-positive tumors tend to be retinoid resistant. Pathway-oriented analysis of the constitutive gene-expression profiles in the cell lines identifies RARα as the member of the retinoid pathway directly associated with a Luminal phenotype, estrogen positivity and ATRA sensitivity. RARα3 is the major tr...
Cancer Research, 1996
Retinoids are known to inhibit the growth of a wide variety of cancer cells, including breast cancer cells. Advances made in recent years in the understanding of the molecular mechanisms of retinoid action have al lowed the design of retinoids with selective activities. Such selective retinoids are of particular interest, because they may reduce the number of undesirable side effects observed with natural compounds. Here, we have compared the growth-inhibitory activities of natural retinoids with vari ous selective retinoids, including anti-activator protein (AP)-l selective compounds on estrogen receptor-positive and -negative breast cancer cell lines. In addition, we have investigated cooperativity between selective retinoids and IFNs and have begun to analyze the pathways that these two different growth inhibitors use for antagonizing breast cancer cell prolif eration. We observe that several selective retinoids can inhibit breast cancer cells as efficiently as the natural compounds. Anti-AP-1-selective retinoids are as effective as retinoic acid receptor (RAR)-ß/y-selective compounds. This lets us conclude that retinoid-induced inhibition of breast cancer cell growth does not require retinoid receptor transactiva-
Genomic Antagonism between Retinoic Acid and Estrogen Signaling in Breast Cancer
Cell, 2009
Retinoic acid (RA) triggers antiproliferative effects in tumor cells, and therefore RA and its synthetic analogs have great potential as anticarcinogenic agents. Retinoic acid receptors (RARs) mediate RA effects by directly regulating gene expression. To define the genetic network regulated by RARs in breast cancer, we identified RAR genomic targets using chromatin immunoprecipitation and expression analysis. We found that RAR binding throughout the genome is highly coincident with estrogen receptor a (ERa) binding, resulting in a widespread crosstalk of RA and estrogen signaling to antagonistically regulate breast cancer-associated genes. ERa-and RARbinding sites appear to be coevolved on a large scale throughout the human genome, often resulting in competitive binding activity at nearby or overlapping cis-regulatory elements. The highly coordinated intersection between these two critical nuclear hormone receptor signaling pathways provides a global mechanism for balancing gene expression output via local regulatory interactions dispersed throughout the genome.