Proliferation Of ER-positive Breast Cancer Cells Research Articles

PFKFB3 regulates breast cancer tumorigenesis and Fulvestrant sensitivity by affecting ERα stability

Estrogen receptor alpha (ERα) is expressed in approximately 70% of breast cancer cases and determines the sensitivity and effectiveness of endocrine therapy. 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase3 (PFKFB3) is a glycolytic enzyme that is highly expressed in a great many human tumors, and recent studies have shown that it plays a significant role in improving drug sensitivity. However, the role of PFKFB3 in regulating ERα expression and the underlying mechanism remains unclear. Here, we find by using immunohistochemistry (IHC) that PFKFB3 is elevated in ER-positive breast cancer and high expression of PFKFB3 resulted in a worse prognosis. In vitro and in vivo experiments verify that PFKFB3 promotes ER-positive breast cancer cell proliferation. The overexpression of PFKFB3 promotes the estrogen-independent ER-positive breast cancer growth. In an estrogen-free condition, RNA-sequencing data from MCF7 cells treated with siPFKFB3 showed enrichment of the estrogen signaling pathway, and a luciferase assay demonstrated that knockdown of PFKFB3 inhibited the ERα transcriptional activity. Mechanistically, down-regulation of PFKFB3 promotes STUB1 binding to ERα, which accelerates ERα degradation by K48-based ubiquitin linkage. Finally, growth of ER-positive breast cancer cells in vivo was more potently inhibited by fulvestrant combined with the PFKFB3 inhibitor PFK158 than for each drug alone. In conclusion, these data suggest that PFKFB3 is identified as an adverse prognosis factor for ER-positive breast cancer and plays a previously unrecognized role in the regulation of ERα stability and activity. Our results further explores an effective approach to improve fulvestrant sensitivity through the early combination with a PFKFB3 inhibitor.

Effect of farrerol on the proliferation of estrogen receptor-positive breast cancer by downregulating oncogenic genes with estrogen receptor response elements.

e12541 Background: Breast cancer (BC) is the most common malignant tumor among women worldwide, the most common of which is estrogen receptor (ER) -positive BC. Farrerol, a noval estrogen-like chemicals, is closely associated with ER positive BC. In this study, we will explore the anticancer effect of farrerol on ER-positive BC and the detailed mechanism. Methods: Cloning formation assay and MTT assay were used to evaluate the effect of farrerol on proliferation ofcells. The affinity of farrerol, estrogen and tamoxifen with ER was tested by molecular docking technique. Point mutation was performed on the possible binding sites of ER according to the results of virtual docking, and Surface Plasmon Resonance (SPR). ER response elements in BC cells with farrerol were evaluated by qPCR. Results: With the increased farrerol concentration, the number of cell clones formed gradually decreased and the volume of clones became smaller in the ER positive McF-7 cell group, while a completely opposite clones was observed in non- ER positive MDA-MB-231 cells. The proliferation inhibition rate of McF-7 cells in the 160 mol/L and 320 mol/L groups was 45.86% and 65.3% respectively, significantly higher than that of MDA-MB-231 and normal mammary epithelial cells (P < 0.05). Both molecular docking technique and SPR experiment showed that farrerol could bind to ER at different sites than estrogen binding. Fiarrerol effectively down-regulated the transcription of the oncogenes MYC and TFF1, and suppressed ER-positive BC. Conclusions: Farrerol has the opposite effect with estrogen, which inhibited the proliferation of ER-positive BC cells, and downregulated the expression of oncogenic genes with ER response elements in BC cells. Therefore, farrerol, as a natural ingredient, could be further developed and applied with its obvious inhibitory effect on ER-positive BC in the future.

Deciphering the Molecular Mechanisms Sustaining the Estrogenic Activity of the Two Major Dietary Compounds Zearalenone and Apigenin in ER-Positive Breast Cancer Cell Lines.

The flavone apigenin and the mycotoxin zearalenone are two major compounds found in the human diet which bind estrogen receptors (ERs), and therefore influence ER activity. However, the underlying mechanisms are not well known. To unravel the molecular mechanisms that could explain the differential effect of zearalenone and apigenin on ER-positive breast cancer cell proliferation, gene-reporter assays, chromatin immunoprecipitation (ChIP) experiments, proliferation assays and transcriptomic analysis were performed. We found that zearalenone and apigenin transactivated ERs and promoted the expression of estradiol (E2)-responsive genes. However, zearalenone clearly enhanced cellular proliferation, while apigenin appeared to be antiestrogenic in the presence of E2 in both ER-positive breast cancer cell lines, MCF-7 and T47D. The transcriptomic analysis showed that both compounds regulate gene expression in the same way, but with differences in intensity. Two major sets of genes were identified; one set was linked to the cell cycle and the other set was linked to stress response and growth arrest. Our results show that the transcription dynamics in gene regulation induced by apigenin were somehow different with zearalenone and E2 and may explain the differential effect of these compounds on the phenotype of the breast cancer cell. Together, our results confirmed the potential health benefit effect of apigenin, while zearalenone appeared to be a true endocrine-disrupting compound.

Silencing of syndecan-binding protein enhances the inhibitory effect of tamoxifen and increases cellular sensitivity to estrogen.

Objective:Tamoxifen is used as a complementary treatment for estrogen receptor (ER)-positive breast cancer (BCa), but many patients developed resistance. The aim of this study was to examine the role of syndecan-binding protein (SDCBP) silencing in ER-positive BCa cells.Methods:In MCF-7/T47D cells, the effects of SDCBP silence/overexpression on cell proliferation and estrogenic response were examined. Cell proliferation was examined using the MTT assay and cell cycle regulators were examined by Western blot. Estrogen response was examined from a luciferase activity and evaluation of transcript levels of pS2 and progesterone receptor (PR) upon estrogen administration. Samples of ER-positive BCa were stained with ERα, PR, and SDCBP antibodies, and their expression correlations were analyzed.Results:We found that SDCBP silencing inhibited the proliferation of ER-positive BCa cells and arrested a greater number of cells in the G1 phase of the cell cycle compared to tamoxifen alone, while SDCBP overexpression limited the anti-cancer effects of tamoxifen. SDCBP silencing and overexpression also enhanced and attenuated the estrogenic response, respectively. Expression of SDCBP was negatively correlated with PR, ERα, and the PR/ERα ratio in ER-positive BCa tissue samples.Conclusions:SDCBP may be involved in tamoxifen resistance in ER-positive BCa. Tamoxifen treatment combined with SDCBP silencing may provide a novel treatment for endocrine therapy-resistant BCa.

Abstract P3-05-07: RAD1901, a novel oral, selective estrogen receptor degrader (SERD) with single agent efficacy in an ER+ primary patent derived ESR1 mutant xenograft model

Abstract Despite advances in the treatment of metastatic breast cancer, many women eventually relapse with more aggressive forms of endocrine-resistant disease. Mutations in the ESR1 gene encoding the estrogen receptor (ER) have recently emerged as a potential mechanism for the development of clinical resistance to conventional anti-estrogen therapies, such as fulvestrant. To overcome some of the pharmacokinetic limitations and intramuscular administration challenges associated with fulvestrant endocrine therapy and to combat the development of resistance, there is a significant need for the development of more durable and more effective ER-targeted therapies. Here, we begin to describe and characterize the preclinical efficacy of RAD1901, a novel, orally bioavailable small-molecule SERD, with significant therapeutic potential for treatment of breast cancer. RAD1901 selectively binds to and degrades the ER and is a potent antagonist of ER-positive breast cancer cell proliferation. Importantly, RAD1901 demonstrated profound tumor growth inhibition in MCF-7 xenograft models when compared to fulvestrant and tamoxifen. Importantly, RAD1901 also demonstrated marked single agent efficacy in a primary patient-derived xenograft (PDx) model harboring the ESR1 Y537S mutation indicating the utility of this SERD against clinically relevant ER mutants. Further biochemical binding studies and co-crystallization experiments of RAD1901 bound to the ER further confirms the ability of RAD1901 to bind to both mutant and wild type forms of the ER. RAD1901 is currently undergoing clinical testing in postmenopausal women with ER-positive advanced breast cancer. Citation Format: Garner F, Brown J, Katzenellenbogen J, Lyttle CR, Hattersley G. RAD1901, a novel oral, selective estrogen receptor degrader (SERD) with single agent efficacy in an ER+ primary patent derived ESR1 mutant xenograft model. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-05-07.

RAD1901: a novel, orally bioavailable selective estrogen receptor degrader that demonstrates antitumor activity in breast cancer xenograft models.

Agents that inhibit estrogen production, such as aromatase inhibitors or those that directly block estrogen receptor (ER) activity, such as selective estrogen receptor modulators and selective estrogen receptor degraders, are routinely used in the treatment of ER-positive breast cancers. However, although initial treatment with these agents is often successful, many women eventually relapse with drug-resistant breast cancers. To overcome some of the challenges associated with current endocrine therapies and to combat the development of resistance, there is a need for more durable and more effective ER-targeted therapies. Here we describe and characterize a novel, orally bioavailable small-molecule selective estrogen receptor degrader, RAD1901, and evaluate its therapeutic potential for the treatment of breast cancer. RAD1901 selectively binds to and degrades the ER and is a potent antagonist of ER-positive breast cancer cell proliferation. Importantly, RAD1901 produced a robust and profound inhibition of tumor growth in MCF-7 xenograft models. In an intracranial MCF-7 model, RAD1901-treated animals survived longer than those treated with either control or fulvestrant, suggesting the potential benefit of RAD1901 in the treatment of ER-positive breast cancer that has metastasized to the brain. Finally, RAD1901 preserved ovariectomy-induced bone loss and prevented the uterotropic effects of E2, suggesting that it may act selectively as an agonist in bone but as an antagonist in breast and uterine tissues. RAD1901 is currently under clinical study in postmenopausal women with ER-positive advanced breast cancer.

Abstract 5568: CYP17A1 and abiraterone: Implications for breast cancer endocrine therapy

Abstract The cytochrome P450 17A1 (CYP17A1) inhibitor abiraterone, which blocks synthesis of all steroid hormones including androgens and estrogens, is an effective treatment for castrate resistant prostate cancer. Its utility for treating hormone receptor-positive breast cancer has yet to be established. In prostate cancer, the anti-proliferative effects of abiraterone are mediated by inhibiting CYP17A1 activity resulting in a significant reduction in circulating concentrations of the sex steroids dehydroepiandrosterone (DHEA), androstenedione, testosterone, and dihydrotestosterone (DHT). Recently, it has been proposed that the reduction in aromatizable androgens by abiraterone may make this drug useful for the management of hormone-dependent breast cancer. However, data from our lab suggests that abiraterone has estrogenic properties and can induce proliferation in breast cancer cells expressing the estrogen receptor (ER). Crystal violet assays were used to assess abiraterone-induced proliferation in the ER-positive, estrogen-dependent breast cancer cell lines MCF-7 and T47D. We show that abiraterone induced a dose dependent increase in cell proliferation with an IC50 of 3.7 μM and maximal stimulation (200%) observed at 8μM, compared to vehicle treated cells. Abiraterone also induced the expression of the ER response gene, GREB1. Abiraterone-induced proliferation and gene expression was blocked by increasing doses of the selective estrogen receptor down-regulator (SERD) fulvestrant. Abiraterone induced the dose-dependent expression of luciferase in MCF-7 cells transfected with an estrogen responsive luciferase reporter construct. In conclusion, our data suggest that abiraterone can induce ER-positive breast cancer cell proliferation in vitro by acting as a weak ER agonist. Further studies are underway to determine whether estrogenic effects of abiraterone are also observed using in vivo models of ER response. If abiraterone exhibits estrogenic effects in vivo then these data would suggest that abiraterone should be combined with an ER antagonist if used for the clinical management of women with ER+ tumors. Citation Format: Cameron P. Capper, Michael D. Johnson, José M. Larios, James M. Rae. CYP17A1 and abiraterone: Implications for breast cancer endocrine therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5568. doi:10.1158/1538-7445.AM2014-5568

Dietary fat without body weight gain increases in vivo MCF‐7 human breast cancer cell growth and decreases natural killer cell cytotoxicity

High-calorie (HC) diet contributes to the increased incidence of obesity, which is a risk factor for breast cancer in postmenopausal women, and in particular for estrogen receptor (ER) positive tumors. This study investigated whether an HC diet increases human ER-positive breast cancer progression and modulates natural killer (NK) cell functions. Four-week-old female BALB/c athymic nude mice were fed a HC diet (5320 kcal/kg) or standard calorie diet (SC, 2820 kcal/kg) for 6 mo. After 5 mo, the mice were randomly implanted with MCF-7 breast cancer cells (SCT and HCT) or received an isovolumic injection (SC and HC) in both inguinal fat pads. Tumor growth was greater in the HCT group than in the SC group without change in body weight. The HC diet decreased the tumor expression of genes involved in the citrate cycle and in adiponectin and lipid metabolism but increased that of genes controlling glycolysis and angiogenesis. The tumor expression level of Ki67 was increased while that of the cleaved caspase 3 and the ER-β and progesterone receptors was reduced. Tumor development in response to the HC diet was associated with smaller numbers and lower cytotoxicity of splenic NK cells. These results indicate that an HC diet without body weight gain increases ER-positive breast cancer cell proliferation and reduces tumor apoptosis. The underlying mechanisms might involve a downexpression of tumor hormonal receptor and reduced NK cell functions, and might also result in the regulation of genes involved in several cellular functions.