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Specific transcriptional response of four blockers of estrogen receptors on estradiol-modulated genes in the mouse mammary gland

ABSTRACT: The efficacy and exceptionally good tolerance of estrogen blockade in the treatment of breast cancer is well recognized but novel agents are required, especially to take advantage of the multiple consecutive responses obtained in breast cancer progressing following previous hormone therapy, thus delaying the use of cytotoxic chemotherapy with its usually serious side effects. Acolbifene (ACOL) is a novel and unique antiestrogen completely free of estrogen-like activity in both the mammary gland and uterus while preventing bone loss. From the preclinical and clinical data so-far available, this new antiestrogen represents a unique opportunity for a highly potent and specific blockade of estrogen action in the mammary gland and uterus while exerting estrogen-like beneficial effects in other tissues (selective estrogen receptor modulator or SERM activity). In order to better understand the specificity of action of acolbifene, we have used Affymetrix GeneChips containing 45,000 probe sets to analyze 34,000 genes to determine the specificity of this compound compared to the pure antiestrogen fulvestrant, as well as the mixed antagonists/agonists tamoxifen and raloxifene to block the effect of estradiol (E2) and to induce effects of their own on gene expression in the mouse mammary gland. The genes modulated by E2 were those identified in two separate experiments and validated by quantitative real-time PCR (Q_RT-PCR). Three hours after the single subcutaneous injection of E2 (0.05 ug), the simultaneous administration of acolbifene, fulvestrant, tamoxifen and raloxifene blocked by 98%, 62%, 43% and 92% the number of E2-upregulated genes, respectively. On the other hand, 70%, 10%, 25% and 55% of the genes down-regulated by E2 were blocked by the same compounds. Acolbifene was also the compound which, when used alone, modulated the smallest number of genes also influenced by E2, namely 4%, thus possibly explaining the potent tumoricidal action of this compound in human breast cancer xenografts where 61% of tumors disappeared, thus bringing a new paradigm in the hormonal therapy of breast cancer.

ORGANISM(S): Mus musculus

PROVIDER: GSE35206 | GEO | 2012/12/05

SECONDARY ACCESSION(S): PRJNA150697

REPOSITORIES: GEO

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Project description:The efficacy and exceptionally good tolerance of estrogen blockade in the treatment of breast cancer is well recognized but novel agents are required, especially to take advantage of the multiple consecutive responses obtained in breast cancer progressing following previous hormone therapy, thus delaying the use of cytotoxic chemotherapy with its usually serious side effects. Acolbifene (ACOL) is a novel and unique antiestrogen completely free of estrogen-like activity in both the mammary gland and uterus while preventing bone loss. From the preclinical and clinical data so-far available, this new antiestrogen represents a unique opportunity for a highly potent and specific blockade of estrogen action in the mammary gland and uterus while exerting estrogen-like beneficial effects in other tissues (selective estrogen receptor modulator or SERM activity). In order to better understand the specificity of action of acolbifene, we have used Affymetrix GeneChips containing 45,000 probe sets to analyze 34,000 genes to determine the specificity of this compound compared to the pure antiestrogen fulvestrant, as well as the mixed antagonists/agonists tamoxifen and raloxifene to block the effect of estradiol (E2) and to induce effects of their own on gene expression in the mouse mammary gland. The genes modulated by E2 were those identified in two separate experiments and validated by quantitative real-time PCR (Q_RT-PCR). Three hours after the single subcutaneous injection of E2 (0.05 ug), the simultaneous administration of acolbifene, fulvestrant, tamoxifen and raloxifene blocked by 98%, 62%, 43% and 92% the number of E2-upregulated genes, respectively. On the other hand, 70%, 10%, 25% and 55% of the genes down-regulated by E2 were blocked by the same compounds. Acolbifene was also the compound which, when used alone, modulated the smallest number of genes also influenced by E2, namely 4%, thus possibly explaining the potent tumoricidal action of this compound in human breast cancer xenografts where 61% of tumors disappeared, thus bringing a new paradigm in the hormonal therapy of breast cancer. Female C57BL6 mice were ovariectomized (OVX). One week after OVX, mice were treated with EM-652.HCl (acolbifene), tamoxifen citrate, raloxifene or ICI 182780 (fulvestrant). Compounds were administered to OVX mice or to OVX mice simultaneously treated with 17b-estradiol (E2). Control groups received an injection of the vehicle alone. All animals were sacrificed after 3h of treatment.Mammary glands from all mice of the same group were collected and pooled. Total mRNA was isolated and converted to biotinylated cRNA.A microarray analysis was performed using Murine U74Av2 Affymetrix microarrays.

Project description:Altered expression of microRNAs (miRNAs), an abundant class of small non-protein-coding RNAs that mostly function as negative regulators of protein-coding gene expression, is common in cancer. Here we analyze the regulation of miRNA expression in response to estrogen, a steroid hormone that is involved in the development and progression of breast carcinomas and that is acting via the estrogen receptors (ER) transcription factors. We set out to thoroughly describe miRNA expression, by using miRNA microarrays and real time RTPCR experiments, in various breast tumor cell lines in which estrogen signaling has been induced by 17β-estradiol (E2). We show that the expression of a broad set of miRNAs decreases following E2 treatment in an ER-dependent manner. We further show that enforced expression of several of the repressed miRNAs reduces E2-dependent cell growth, thus linking expression of specific miRNAs with estrogen-dependent cellular response. In addition, a transcriptome analysis revealed that the E2-repressed miR-26a and miR-181a regulate many genes associated with cell growth and proliferation, including the progesterone receptor gene, a key actor in estrogen signaling. Strikingly, miRNA expression is also regulated in breast cancers of women who had received antiestrogen neoadjuvant therapy thereby showing an estrogen-dependent in vivo regulation of miRNA expression. Overall, our data indicates that the extensive alterations in miRNA regulation upon estrogen signalling pathway plays a key role in estrogen-dependent functions and highlights the utility of considering miRNA expression in the understanding of antiestrogen resistance of breast cancer. 9 samples analyzed. Triplicates were done. MCF-7+miR26a+E2 (n=1 to 3) ; MCF7+miRctrl+E2 (n=1 to 3) ; MCF7+miRctrl+vehicle (n=1 to 3). We generated pairwise comparisons using EASANA from GenoSplice technology: MCF-7+miR26a+E2 versus MCF7+miRctrl+E2 and MCF-7+miRctrl+E2 versus MCF7+miRctrl+vehicle. Fold change ≥1.5 were selected.

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Specific transcriptional response of four blockers of estrogen receptors on estradiol-modulated genes in the mouse mammary gland

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