Function In Breast Cancer Cells Research Articles

Oxeiptosis gene expression profiling identified TCN1 as a prognostic factor for breast cancer

Abstract Objectives Oxeiptosis could suppress the progression of breast cancer (BRCA). We aim to identify the prognostic factor associated with BRCA using oxeiptosis gene expression profiling and investigate its role in BRCA. Methods We extracted RNA sequencing data and clinical information on BRCA samples from the Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), and the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) databases using an oxeiptosis-related gene set. Prognosis-related genes for BRCA were screened from the TCGA dataset using bioinformatics analysis. Subsequently, we constructed a prognostic model for BRCA depending on the expression of this predictive factor and analyzed the associated function. The effects of Transcobalamin 1 (TCN1) on BRCA cell function and H2O2-induced oxeiptosis were validated in vitro. Results TCN1 was identified as the most strongly associated factor with BRCA prognosis among the differentially expressed genes in oxeiptosis. Patients with high TCN1 expression demonstrated a better prognosis in BRCA. In BRCA, TCN1 was enriched in response to the oxidative stress pathway. Additionally, TCN1 was associated with the expression of immune checkpoints and gene variations. Compared to normal human breast epithelial cells, TCN1 was downregulated in BRCA cells. Overexpression of TCN1 inhibited the proliferation, migration, and invasion of BRCA cells, and enhanced H2O2-induced oxeiptosis in BRCA cells. Conclusions Based on the oxeiptosis gene set, we identified TCN1 as a prognostic factor associated with BRCA. The findings highlight the potential of TCN1 as a therapeutic target and provide valuable insights into the development of personalized treatment strategies for BRCA.

Identification of Tumor-Suppressive miR-30a-3p Controlled Genes: ANLN as a Therapeutic Target in Breast Cancer.

Our recently created RNA-sequence-based microRNA (miRNA) expression signature in breast cancer clinical specimens revealed that some miR-30 family members were significantly downregulated in cancer tissues. Based on TCGA database analyses, we observed that among the miR-30 family members, miR-30a-3p (the passenger strand derived from pre-miR-30a) was significantly downregulated in breast cancer (BC) clinical specimens, and its low expression predicted worse prognoses. Ectopic expression assays showed that miR-30a-3p transfected cancer cells (MDA-MB-157 and MDA-MB-231) had their aggressive phenotypes significantly suppressed, e.g., their proliferation, migration, and invasion abilities. These data indicated that miR-30a-3p acted as a tumor-suppressive miRNA in BC cells. Our subsequent search for miR-30a-3p controlled molecular networks in BC cells yielded a total of 189 genes. Notably, among those 189 genes, cell-cycle-related genes (ANLN, MKI67, CCNB1, NCAPG, ZWINT, E2F7, PDS5A, RIF1, BIRC5, MAD2L1, CACUL1, KIF23, UBE2S, EML4, SEPT10, CLTC, and PCNP) were enriched according to a GeneCodis 4 database analysis. Moreover, the overexpression of four genes (ANLN, CCNB1, BIRC5, and KIF23) significantly predicted worse prognoses for patients with BC according to TCGA analyses. Finally, our assays demonstrated that the overexpression of ANLN had cancer-promoting functions in BC cells. The involvement of miR-30a-3p (the passenger strand) in BC molecular pathogenesis is a new concept in cancer research, and the outcomes of our study strongly indicate the importance of analyzing passenger strands of miRNAs in BC cells.

LncRNA OIP5-AS1 Upregulates the Cyclin D2 Levels to Promote Metastasis of Breast Cancer by Targeting miR-150-5p.

Breast cancer (BC) is a cancer that seriously affects women's health. BC cell migration increases the mortality of BC patients. Current studies have shown that long noncoding RNAs (LncRNAs) are related to the metastasis mechanism of BC. This study aimed to explore the function and role of LncRNA OIP5-AS1 in BC. And we analyzed its regulatory mechanism and related modification process. Our study analyzed the expression pattern of OIP5-AS1 in BC tissues and cell lines by qRT-PCR. The effects of OIP5-AS1 on the function of BC cells were detected by CCK-8 and transwell experiments. Bioinformatics analysis and double luciferase reporter gene detection were used to confirm the correlation between OIP5-AS1 and miR-150-5p and between miR-150-5p and Cyclin D2 (CCND2). The rescue test analyzed the effect of miR-150-5p regulating OIP5-AS1. In addition, the N6-methyladenosine (m6A) modification process of OIP5-AS1 was analyzed by RNA m6A dot blot, RIP assay, and double luciferase report experiment. OIP5-AS1 was significantly upregulated in BC tissues and cell lines. OIP5-AS1 knockdown inhibited BC cell viability, migration and invasion. OIP5-AS1 upregulated CCND2 by binding with miR-150-5p. This process affected the metastasis of BC. Higher degree of m6A methylation was confirmed in BC cell lines. There were some binding sites between methyltransferase like 3 (METTL3) and OIP5-AS1. Moreover, the silencing of METTL3 inhibited the OIP5-AS1 expression through decreasing the m6A methylation levels. LncRNA OIP5-AS1 promoted cell viability and metastasis of BC cells by targeting miR-150-5p/CCND2 axis. This process was modified by m6A methylation of METTL3.

Identification and validation of DHCR7 as a diagnostic biomarker involved in the proliferation and mitochondrial function of breast cancer.

Energy metabolism has a complex intersection with pathogenesis and development of breast cancer (BC). This allows for the possibility of identifying energy-metabolism-related genes (EMRGs) as novel prognostic biomarkers for BC. 7-dehydrocholesterol reductase (DHCR7) is a key enzyme of cholesterol biosynthesis involved in many cancers, and in this paper, we investigate the effects of DHCR7 on the proliferation and mitochondrial function of BC. EMRGs were identified from the Gene Expression Omnibus (GEO) and MSigDB databases using bioinformatics methods. Key EMRGs of BC were then identified and validated by functional enrichment analysis, interaction analysis, weighted gene co-expression network analysis (WGCNA), least absolute shrinkage and selection operator (LASSO) regression, Cox analysis, and immune infiltration. Western blot, qRT-PCR, immunohistochemistry (IHC), MTT assay, colony formation assay and flow cytometry assay were then used to analyze DHCR7 expression and its biological effects on BC cells. We identified 31 EMRGs in BC. These 31 EMRGs and related transcription factors (TFs), miRNAs, and drugs were enriched in glycerophospholipid metabolism, glycoprotein metabolic process, breast cancer, and cell cycle. Crucially, DHCR7 was a key EMRG in BC identified and validated by WGCNA, LASSO regression and receiver operating characteristic (ROC) curve analysis. High DHCR7 expression was significantly associated with tumor immune infiltration level, pathological M, and poor prognosis in BC. In addition, DHCR7 knockdown inhibited cell proliferation, induced apoptosis and affected mitochondrial function in BC cells. DHCR7 was found to be a key EMRG up-regulated in BC cells. This study is the first to our knowledge to report that DHCR7 acts as an oncogene in BC, which might become a novel therapeutic target for BC patients.

Regulator of Ribosome Synthesis 1 (RRS1) Stabilizes GRP78 and Promotes Breast Cancer Progression.

Regulator of ribosome synthesis 1 (RRS1), a crucial regulatory factor in ribosome biogenesis, exerts a remarkable impact on the progression of breast cancer (BC). However, the exact mechanisms and pathways have not yet been fully elucidated. To investigate the impact of RRS1 on BC growth and metastasis, along with its underlying mechanisms. We discovered that RRS1 is overexpressed in BC tissues and cell lines. This study aims to regulate the level of RRS1 through lentiviral transfection technology to explore its potential function in BC cells. Knockdown of RRS1 resulted in the inhibition of cell proliferation, invasion, and migration, whereas overexpression had the opposite effects. We firstly identified the interaction between RRS1 and Glucose-Regulated Protein 78 (GRP78) using Co-immunoprecipitation (Co-IP) combined with mass spectrometry analysis, providing evidences of co-localization and positive regulation between RRS1 and GRP78. We observed that RRS1 inhibited the degradation of GRP78 through the ubiquitin-proteasome pathway, resulting in the stabilization of GRP78. In addition, our findings suggested that RRS1 promoted BC progression by activating the GRP78-mediated phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway. In conclusion, this newly discovered RRS1/GRP78 signaling axis provides a molecular and theoretical basis for further exploring the mechanisms of breast cancer invasion and metastasis.

CircSEPT9 promotes breast cancer progression by regulating PTBP3 expression via sponging miR-625-5p.

Breast cancer (BC) is a common malignancy which threatens the health of women. Circular RNAs (circRNAs) are critical factors in multiple cancers, including BC. The aim of this experiment was to investigate the molecular mechanisms of circRNA Septin 9 (circSEPT9) in the progression of BC. CircSEPT9, microRNA-625-5p (miR-625-5p) and polypyrimidine tract-binding protein 3 (PTBP3) levels were determined by quantitative real-time polymerase chain reaction (qRT-PCR). Western blot was performed to detect the protein levels of PTBP3, E-cadherin and vimentin. Cell counting kit-8 assay (CCK8) and thymidine analog 5-ethynyl-2'-deoxyuridine (EDU) was utilized for proliferation examination. Flow cytometry was conducted to measure apoptosis. Transwell assay and wound healing assay to investigate the migration of BC cells. Glucose uptake and lactate production were determined by specific kits. Additionally, dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were utilized to verify the interaction. A murine xenograft model was established to investigate the function of circSEPT9 in BC in vivo. Overexpression of circSEPT9 was found in BC tissues and cells. Silencing circSEPT9 impeded BC cell proliferation, migration, epithelial-mesenchymal transition (EMT) and glycolytic metabolism but facilitated cell apoptosis in vitro. Meanwhile, circSEPT9 knockdown constrained tumor growth in vivo. MiR-625-5p was targeted by circSEPT9. The influence of silencing circSEPT9 on BC cell function was regained by miR-625-5p inhibitor. Furthermore, miR-625-5p regulated BC cell malignant phenotypes via downregulating PTBP3. circSEPT9 contributed to the malignant progression of BC by up-regulating PTBP3 via sponging miR-625-5p.

Chemotherapy-induced exosomal circBACH1 promotes breast cancer resistance and stemness via miR-217/G3BP2 signaling pathway

BackgroundChemoresistance involves metastasis and aggressiveness of breast cancer (BC). Chemotherapy-elicited exosomes have been reported to be associated with drug resistance and pro-metastatic capacity of BC cells. Non-coding RNAs (ncRNAs) are enriched in exosomes, which participated in generation, progression, and resistance of BC. However, the mechanism underlying the chemoresistance and metastasis in BC cells mediated by the BC-derived exosomal ncRNAs remained to be elucidated.MethodsThe effects of PTX-induced exosomal circBACH1 on BC cell function were assessed using RNA Binding Protein Immunoprecipitation (RIP), dual luciferase reporter gene, tube formation, CCK-8, and Western Blot assays. The circBACH1 and miR-217 expression levels were detected using quantitative real-time PCR (RT-qPCR) and Immunohistochemistry (IHC) assays in BC tissues and precancerous tissues of BC patients.ResultsCircBACH1 expression was increased in paclitaxel-treated BC-derived exosomes (PTX-EXO) and BC tissue. PTX-EXO was shown to promote PTX-resistance and angiogenesis through upregulation circBACH1. Downregulation of circBACH1 improved PTX-sensitiveness by suppressing the cell viability, stemness, migration, and angiogenesis of BC cells. Moreover, we found that miR-217 interacted with circBACH1 and targeted GTPase-activating SH3 domain-binding protein 2 (G3BP2) in BC cells. CircBACH1 combined miR-217 cotransfection suppressed the expression of G3BP2 proteins compared with circBACH1 treatment in MCF-7 cells. In addition, downregulation of G3BP2 suppressed BC cell migration.ConclusionsThese results demonstrated that PTX-induced exosomal circBACH1 promoted stemness and migration of BC cells by sponging miR-217 to upregulate the expression of G3BP2, which provided a new therapeutic target for PTX-resistance and progression of BC via circBACH1/miR-217/G3BP2 axis.

NFκB-Mediated Mechanisms Drive PEDF Expression and Function in Pre- and Post-Menopausal Oestrogen Levels in Breast Cancer

Pigment epithelium-derived factor (PEDF) protein regulates normal bone, with anti-tumour roles in bone and breast cancer (BC). Pre- and post-menopausal oestrogen levels may regulate PEDF expression and function in BC, though the mechanisms behind this remain unknown. In this study, in vitro models simulating pre- and post-menopausal bone microenvironments were used to evaluate if PEDF regulates pro-metastatic biomarker expression and downstream functional effects on BC cells. PEDF treatment reduced phosphorylated-nuclear factor-κB p65 subunit (p-NFκB-p65), tumour necrosis factor-α (TNFα), C-X-C chemokine receptor type-4 (CXCR4), and urokinase plasminogen activator receptor (uPAR) in oestrogen receptor (ER)+/human epidermal growth factor receptor-2 (HER2)- BC cells under post-menopausal oestrogen conditions. In triple negative BC (TNBC) cells, PEDF treatment reduced pNFκB-p65 and uPAR expression under pre-menopausal oestrogen conditions. A potential reciprocal regulatory axis between p-NFκB-65 and PEDF in BC was identified, which was BC subtype-specific and differentially regulated by menopausal oestrogen conditions. The effects of PEDF treatment and NFκB inhibition on BC cell function under menopausal conditions were also compared. PEDF treatment exhibited superior anti-viability effects, while combined PEDF and NFκB-p65 inhibitor treatment was superior in reducing BC cell colony formation in a subtype-specific manner. Lastly, immunohistochemical evaluation of p-NFκB-p65 and PEDF expression in human BC and bone metastases specimens revealed an inverse correlation between nuclear PEDF and NFκB expression in bone metastases. We propose that menopausal status is associated with a PEDF/NFκB reciprocal regulatory axis, which drives PEDF expression and anti-metastatic function in a subtype-specific manner. Altogether, our findings identify pre-menopausal TNBC and post-menopausal ER+/HER2- BC patients as target populations for future PEDF research.

LINC00092 Modulates Oxidative Stress and Glycolysis of Breast Cancer Cells via Pyruvate Carboxylase-Mediated AKT/mTOR Pathway.

Background The discovery of noncoding RNAs (ncRNAs) offers new options for cancer-targeted therapy. This study is aimed at exploring the regulatory function of LINC00092 on breast cancer (BC) oxidative stress and glycolysis, along with internal mechanism concerning pyruvate carboxylase (PC). Methods Bioinformatics analysis was used to explore LINC00092 (or friend leukemia virus integration 1 (FLI1)) expression on BC progression, as well as oxidative stress and glycolysis in BC. After LINC00092 overexpression or silence, BC cell viability, proliferation, migration, invasion, oxidative stress, glycolysis, and AKT/mTOR pathway were detected. Following 2-DG, SC79, or MK2206 treatment, effects of LINC00092 on BC cells were measured. Moreover, regulatory activity of LINC00092 in PC expression was analyzed. Whether PC participated in the modulation of LINC00092 on BC cell functions was explored. Results LINC00092 was lowly expressed in BC and negatively related to BC progression. FLI1 bound to LINC00092 promoter to positively modulate LINC00092. LINC00092 overexpression inhibited BC cell proliferation, migration, invasion, oxidative stress, glycolysis, and AKT/mTOR pathway and likewise suppressed BC growth in vivo. Silence of LINC00092 had opposite influences. 2-DG partially reversed the LINC00092 silence-resulted increase of BC cell proliferation. SC79 alleviated the function of LINC00092 overexpression on BC cell functions. MK2206 had the contrary influence of SC79. Besides, LINC00092 bound to PC to modulate ubiquitination degradation of PC protein. PC took part in the influences of LINC00092 on BC cell functions. Conclusions LINC0092 modulates oxidative stress and glycolysis of BC cells via the PC-mediated AKT/mTOR pathway, which is possibly a target for BC diagnosis and therapy.

Long non-coding RNA NORAD inhibition upregulates microRNA-323a-3p to suppress tumorigenesis and development of breast cancer through the PUM1/eIF2 axis

ABSTRACT Long non-coding RNAs (lncRNAs) are known to competitively bind with microRNAs (miRNAs) to participate in human cancers. We aim to explore the role of non-coding RNA activated by DNA damage (NORAD) binding to miR-323a-3p in breast cancer (BC) with the involvement of pumilio RNA-binding family member 1 (PUM1)/eukaryotic initiation factor 2 (eIF2) axis. Expression of NORAD, miR-323a-3p and PUM1 in tissues and cell lines was detected, and the correlation between NORAD expression and clinicopathological features of BC patients was analyzed. The screened cell line was respectively transfected with altered NORAD or miR-323a-3p to reveal their roles in viability, migration, invasion and apoptosis of BC cells in vitro. The tumor growth in vivo was observed in nude mice. The binding relationships among NORAD, miR-323a-3p and PUM1 were analyzed, and the regulatory role of NORAD and miR-323a-3p in the eIF2 signaling pathway was assessed. NORAD and PUM1 were upregulated and miR-323a-3p was downregulated in BC. High NORAD expression indicated a poor prognosis of BC patients. NORAD inhibition or miR-323a-3p elevation inhibited malignant behaviors of BC cells. The in vivo assay revealed that NORAD inhibition or miR-323a-3p elevation inhibited tumor growth as well. MiR-323a-3p inhibition reversed the role of NORAD knockdown in the biological functions of BC cells while silencing PUM1 reversed the influence of NORAD overexpression on BC cells. NORAD bound with miR-323a-3p and miR-323a-3p targeted PUM1. NORAD and miR-323a-3p functioned through the PUM1/eIF2 axis. NORAD inhibition or miR-323a-3p elevation suppresses the development of BC through the PUM1/eIF2 axis.

Killing Action of Cuprous Oxide Nanoparticles on Breast Cancer Cells

Breast cancer (BC), a common malignancy, is intractable at present. Cuprous oxide nanoparticles (Conps) are new nanoparticles crucial in inhibiting tumor progression according to early studies, but their role in BC remains unclear. Field emission-scanning electron microscopy (FESEM) and field emission–transmission electron microscopy (FETEM) were used for the morphological observation of Conps, and energy-dispersive X-ray spectroscopy was used for their elemental composition analysis. Multipoint nitrogen adsorption was used to determine the Brunauer–Emmet–Teller of Conps, and their mean hydrodynamic size and zeta potential in water and intact cell medium were determined by dynamic light scattering (DLS). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, Cell Counting Kit-8, Transwell assay, and flow cytometry were used to determine the effects of Conps on the biological function of BC cells. Western blotting was used to determine the changes in apoptosis-related proteins. Using FESEM and FETEM based on DLS and zeta potential determination, Conps was successfully constructed. Conps significantly lowered the viability of BC cells in a dose-dependent manner, significantly inhibited cell proliferation, invasion, and migration activities, and induced cell apoptosis. Western blotting demonstrated that Conps up-regulated Bax and caspase-3 proteins and down-regulated Bcl-2 protein. The results suggest that Conps can suppress the proliferation, invasion, and migration of BC cells and accelerate their apoptosis. This is a new potential strategy for the clinical treatment of BC.

MiR-566 protects the malignant progression of breast cancer by negatively regulating WNT6.

To elucidate the relationship between microRNA-566 (miR-566) and prognosis in breast cancer (BC) and to clarify the influences of miR-566 and WNT6 in its locus region on BC progression. MiR-566 and WNT6 levels in 44 pairs of BC samples were detected by quantitative real-time polymerase chain reaction (qRT-PCR). The influences of miR-566 on clinical features and prognosis in BC patients were analyzed. According to the differential expressions of miR-566 in the tested BC cell lines, MDA-MB-231 and MCF-7 cells were selected for generating miR-566 knockdown and overexpression models, respectively. Cell counting kit-8 (CCK-8), 5-Ethynyl-2'-deoxyuridine (EdU) and transwell assays were conducted to explore the role of miR-566 in BC cell functions. Besides, the regulatory interaction between miR-566 and its downstream gene WNT6 was assessed by performing Dual-Luciferase reporter assay. Finally, the co-regulation of miR-566 and WNT6 in BC cell functions was examined. MiR-566 was downregulated in BC tissues. BC patients with a low expression level of miR-566 were prone to suffering a large tumor size, advanced tumor grade, high incidence of lymphatic metastasis and poor prognosis. Overexpression of miR-566 weakened proliferative and migratory abilities in MCF-7 cells, whereas knockdown of miR-566 produced the opposite results in MDA-MB-231 cells. WNT6 was the target gene binding to miR-566, and they displayed a negative expression correlation in BC tissues. Regulatory effects of miR-566 on BC progression could be reversed by WNT6. MiR-566 is closely related to tumor size, tumor grade, lymphatic metastasis and prognosis in BC. It protects the malignant progression of BC by negatively regulating WNT6.

MicroRNA-296 functions as a tumor suppressor in breast cancer by targeting FGFR1 and regulating the Wnt/β-catenin signaling pathway.

Breast cancer (BC) is a common malignancy all over the world. However, the detailed mechanism underlying BC progression remains incompletely understood. MicroRNAs (miRNAs) have been observed to play crucial roles in tumorigenesis. The present study aimed to determine the expression and function of miR-296 in BC. MiR-296 expressions in BC tissue samples and cell lines were examined by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). After that, we performed functional assays, including MTT (3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assays and transwell assays, to show the functions of miR-296 in BC cell proliferation, invasion and migration. Immunological histological chemistry (IHC) assays were carried out to detect the expression levels of fibroblast growth factor receptor 1 (FGFR1) in BC tissue samples. Western blot was used to explore potential mechanisms of miR-296 in regulating BC progression. A Luciferase reporter assay was carried out to confirm the target gene of miR-296. Quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) results demonstrated a significant decrease of miR-296 expressions in BC when compared to the corresponding normal controls. In addition, the decreased miR-296 was correlated with the malignant phenotypes and poorer prognosis of BC patients. The functional assays indicated that miR-296 restoration could repress the proliferation, invasion and migration abilities of BC cells. Moreover, the results of the current study revealed that miR-296 exerted the repressive functions in BC cells via regulating FGFR1, the Wnt/β-catenin signaling pathway and EMT. Additionally, miR-296 up-regulation could inhibit in vivo BC cell growth. All these findings indicated that miR-296 exerted anti-BC functions, providing novel therapeutic strategies in BC treatment.

CircRNA_100876 promote proliferation and metastasis of breast cancer cells through adsorbing microRNA-361-3p in a sponge form.

This study was designed to investigate the expression level of circRNA_100876 in breast cancer (BC) tissues or cells, and to further explore whether it can promote cell metastasis and proliferative capacity via targeting microRNA- 361-3 p. Quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) was performed to examine the expression of circRNA_100876 in 50 pairs of BC tissue specimens and corresponding adjacent ones, and the correlation between circRNA_100876 expression and prognosis of patients with BC was analyzed. Meanwhile, qRT-PCR was further performed to verify circRNA_100876 level in BC cell lines. In addition, circRNA_100876 knockdown model was constructed using lentivirus and transfected in BC cells. Subsequently, the impact of circRNA_100876 on BC cell function was analyzed using Cell Counting Kit-8 (CCK-8), transwell and clone formation assays. The interplay between circRNA_100876 and microRNA- 361-3 p was verified using the Luciferase reporter gene assay and cell reverse experiment. QRT-PCR results showed that circRNA_100876 level in BC tissues was conspicuously higher than that in the adjacent tissues, and the patients with distant metastasis had higher expression than those without. Moreover, patients with a high expression of circRNA_100876 had a relatively lower overall survival rate. Compared with the NC group, the cell proliferation and invasion ability of circRNA_100876 knockdown group was conspicuously decreased. QRT-PCR revealed that microRNA-361-3p and circRNA_100876 showed a negative correlation in the expression level of genes in BC tissues. In addition, the results of the Luciferase reporter gene assay confirmed that circRNA_100876 can be targeted by microRNA-361-3p through their binding site. High expression of circRNA_100876 is conspicuously positively relevant to poor prognosis of BC patients. Additionally, circRNA_100876 is able to promote BC metastasis as well as proliferative capacity by modulating microRNA-361-3p expression.

Post-transcriptional Regulation of Human Breast Cancer Cell Proteome by Unliganded Estrogen Receptor β via microRNAs

Estrogen receptor β (ERβ) is a member of the nuclear receptor family of homeostatic regulators that is frequently lost in breast cancer (BC), where its presence correlates with a better prognosis and a less aggressive clinical outcome of the disease. In contrast to ERα, its closest homolog, ERβ shows significant estrogen-independent activities, including the ability to inhibit cell cycle progression and regulate gene transcription in the absence of the ligand. Investigating the nature and extent of this constitutive activity of ERβ in BC MCF-7 and ZR-75.1 cells by means of microRNA (miRNA) sequencing, we identified 30 miRNAs differentially expressed in ERβ+ versus ERβ- cells in the absence of ligand, including up-regulated oncosuppressor miRs such miR-30a. In addition, a significant fraction of >1,600 unique proteins identified in MCF-7 cells by iTRAQ quantitative proteomics were either increased or decreased by ERβ, revealing regulation of multiple cell pathways by ligand-free receptors. Transcriptome analysis showed that for a large number of proteins regulated by ERβ, the corresponding mRNAs are unaffected, including a large number of putative targets of ERβ-regulated miRNAs, indicating a central role of miRNAs in mediating BC cell proteome regulation by ERβ. Expression of a mimic of miR-30a-5p, a direct target and downstream effector of ERβ in BC, led to the identification of several target transcripts of this miRNA, including 11 encoding proteins whose intracellular concentration was significantly affected by unliganded receptor. These results demonstrate a significant effect of ligand-free ERβ on BC cell functions via modulation of the cell proteome and suggest that miRNA regulation might represent a key event in the control of the biological and clinical phenotype of hormone-responsive BC by this nuclear receptor.

Abstract P5-06-04: Nicastrin Reveals Gamma-Secretase Independent Function in Breast Cancer Cells and Can Be Targeted by a Blocking Monoclonal Antibody To Reduce Breast Cancer Cell Proliferation and Invasion

Abstract BACKGROUND: Nicastrin (NCT) is a structural and functional part of the gamma-secretase (GS) enzyme, implicated in tumorigenesis and resistance to treatment in multiple cancer types. However, its mechanism(s) of action and biological functions are poorly understood. We investigated functional and biological effects of inhibiting NCT in breast cancer (BC)cells by means of gene silencing and blocking antibodies, as well as the prognostic value of NCT expression in BC tissue. METHODS: NCT siRNA (Dahrmacon) was used at 40nM. A polyclonal antibody (pcAb) against NCT extracellular domain was developed at Biogenes (GE), and anti-NCT monoclonal antibodies (mAbs) at Genovac (GE). We tested the Abs for their ability to recognize endogenous NCT in BC cells by FACS and Western blot. Best Abs were tested in vitro, using a transwell cell invasion assay and proliferation assay. Anti-NCT Ab (Sigma, N1660) was used for immunohistochemistry (IHC) staining of BC tissues (n = 1050). Cases were scored as NCT negative (0), 1+, 2+ or 3+. Kaplan Meier analysis was used to investigate impact of NCT expression on survival. Illumina (Agilent) oligonucleotide arrays were used to investigate NCT siRNA effects on gene expression in BC cells. Both PcAb and mAbs recognized endogenous NCT in BC cells. In vitro, blocking NCT in MDA-MB231 BC cells with the PcAb, reduced cell proliferation in a dose dependent manner; by 50% and 70% at concentrations of 50μg/ml and 100μg/ml, respectively. mAbs reduced proliferation by 50% (clones 2H6 and 10C5) and 70% clone 10C11, (P<0.01). In transwell cell invasion assay, anti-NCT pcAb induced a dose dependent reduction of invasion, by 35% at the 5μg/ml, peaking at > 60% reduction at 50μg/ml (P<0.001). mAbs reduced cell invasion by 40-50% (clone 10C5 and 10C11) and by >65% (clone 2H6) (P<001). IHC data showed that NCT was highly expressed (2+, 3+) in 47.5% of BC tissues. High NCT expression correlated with worse overall survival (OS) in ERnegative patients (p=0.05). To elucidate the effects of NCT loss, compared to those induced by GSIs or silencing Notch receptors, we examined cDNA from MDA231 treated independently with NCT, Notch1, Notch2, Notch4 siRNAs and GSI MK-003, on Illumina expression arrays. Thirteen of the 18 genes maximally affected by GSI were similarly affected by NCT siRNA. NCT knockdown also affected 1745 other genes that by large were not affected by GSI or Notch knockdowns. This suggests that NCT has GS-and Notch-independent cellular functions and may have different biological properties as a therapeutic target than GS. Among NCT siRNA affected genes, some are tumor suppressors: CST4 increased 8 fold; pro-invasive genes like GNG11 decreased 4 fold; cell adhesion genes: CTGF increased 4.5 fold etc. CONCLUSIONS: NCT is overexpressed in 47.5% of BC cases where it infers adverse OS in the ER-vecohort of patients. Anti-NCT mAbs recognize endogenous NCT in BC cells and reduce BC cell proliferation and invasion. Silencing NCT in invasive BC cells induces extensive gene expression changes that only partially overlap with those caused by GSIs or Notch siRNAs. We conclude that NCT has GS-independent functions in BC cells and that an anti-NCT mAb may be a promising therapeutic approach for invasive BC. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-06-04.