Function In Breast Cancer Research Articles

MiR-301b-3p Regulates Breast Cancer Cell Proliferation, Migration, and Invasion by Targeting NR3C2.

Objectives Breast cancer is the most common malignant tumor among females, and miRNAs have been reported to play an important regulatory role in breast cancer progression. This study aimed to explore the function and underlying molecular mechanism of miR-301b-3p in breast cancer. Methods Differential analysis and survival analysis were performed based on the data accessed from the TCGA-BRCA dataset for identification of the target miRNA. Bioinformatics analysis was conducted to predict the downstream target gene of the miRNA. Real-time quantitative PCR was carried out to detect the expression of miR-301b-3p and nuclear receptor subfamily 3 group C member 2 (NR3C2). Western blot was used to assess the protein expression of NR3C2. Cell counting kit-8 assay was performed to evaluate the proliferation of breast cancer cells. Transwell assay was conducted to determine the migratory and invasive abilities of breast cancer cells. Dual-luciferase reporter assay was employed to verify the targeting relationship between miR-301b-3p and NR3C2. Results miR-301b-3p was elevated in breast cancer cell lines and promoted cell proliferation, migration, and invasion in terms of its biological function in breast cancer. NR3C2 was validated as a direct target of miR-301b-3p via bioinformatics analysis and dual-luciferase reporter assay, and NR3C2 was downregulated in breast cancer cell lines. The rescue experiment indicated that NR3C2 was involved in the mechanism by which miR-301b-3p regulated the malignant phenotype of breast cancer cells. Conclusion The present study revealed for the first time that miR-301b-3p could foster breast cancer cell proliferation, migration, and invasion by targeting NR3C2, unveiling that miR-301b-3p is a novel carcinogen in breast cancer.

Prognostic significance of transforming growth factor β receptor II in clinical stage III breast cancer patients - a pilot study.

Transforming growth factor-β (TGFβ) has a dual function in breast cancer, having a tumor suppressor activity in early carcinomas while enhancing tumor metastasis in advanced breast carcinoma. Consequently, the prognostic role of TGFβ and its signaling cascade in breast cancer remain unclear. To investigate the relationship between TβRII expression, clinic-pathological characteristics, and prognostic significance of TβRII expression in clinical stage III breast cancer. Biopsy from the primary tumor was obtained from 30 newly diagnosed clinical stage III breast cancer patients before receiving any therapy. Expression of TβRII, ER, PR, Her2 and Ki-67 was assessed by immunohistochemistry. TβRII expression was positive in 66.7% of cases and was significantly associated with advanced nodal stage and distant metastases. After a median follow up of 42.3 months, TβRII was associated with poor disease-free survival and it was an independent factor for predicting the poor outcome for breast cancer patients, especially in node positive tumors, ER/PR positive and Her2-negative tumors. These findings suggest the usage of therapeutic drugs that target TGFβ in advanced breast cancer patients may be effective. Nevertheless, blockage of the tumor promoting and sparing of the tumor suppressor effect of TGFβ pathway should be taken into consideration. We suggest that these therapies might have more benefit in ER and PR positive tumors.

The Role of STAT1 in T Helper Cell Differentiation during Breast Cancer Progression.

Members of the signal transducer and activator of transcription (STAT) protein family are intracellular transcription factors that facilitate several facets of cellular immunity, proliferation, apoptosis, and differentiation. They are principally stimulated by membrane receptor-associated Janus kinases. Dysregulation of this pathway is often detected in primary tumors and hints at augmented angiogenesis, which enriches tumors persistence and immunosuppression. STAT proteins play indispensable roles in cytokine signaling and T helper (Th) cell differentiation. Among STAT proteins, STAT1 plays a vital role in interferon signaling, which initiates the expression of genes encoding proteins with antitumor and apoptotic roles. STAT1 signaling is essential for Th1 cell differentiation. Several studies have also shown the role of STAT1 as a tumor suppressor in breast cancer, which is the most common intrusive malignancy and the second most common cause of cancer death in women. Herein, we review the intricate STAT1-mediated molecular mechanisms associated with Th cell differentiation and anti-tumor function in breast cancer.

PAK5-mediated AIF phosphorylation inhibits its nuclear translocation and promotes breast cancer tumorigenesis.

Although p21 activated kinase 5 (PAK5) is related to the progression of multiple cancers, its biological function in breast cancer remains unclear. Apoptosis-inducing factor (AIF) is a vital apoptosis factor in mitochondria, which can be released from mitochondria and enter the nucleus, causing caspase-independent apoptosis. In this study, we reveal that PAK5 inhibits apoptosis by preventing the nuclear translocation of AIF. PAK5 inhibits the release of AIF from mitochondria in breast cancer cells by decreasing the mitochondria membrane permeability and increasing the membrane potential. Furthermore, PAK5 phosphorylates AIF at Thr281 site to inhibit the formation of AIF/importin α3 complex, leading to decrease AIF nuclear translocation. Functionally, we demonstrate that PAK5-mediated AIF phosphorylation promotes the proliferation of breast cancer cells and accelerates the growth of breast cancer in vivo. Significantly, PAK5 and AIF expression in breast cancer are positively correlated with poor patient prognosis. PAK5 expression is negatively correlated with AIF nuclear translocation. These results suggest that PAK5-AIF signaling pathway may play an essential role in mammary tumorigenesis, providing a new therapeutic target for the treatment of breast cancer.

Glucose Concentration in Cell Culture Medium Influences the BRCA1-Mediated Regulation of the Lipogenic Action of IGF-I in Breast Cancer Cells.

Hyperglycaemia is a common metabolic alteration associated with breast cancer risk and progression. We have previously reported that BRCA1 restrains metabolic activity and proliferative response to IGF-I anabolic actions in breast cancer cells cultured in high glucose. Here, we evaluated the impact of normal physiological glucose on these tumour suppressive roles of BRCA1. Human breast cancer cells cultured in normal physiological and high glucose were treated with IGF-I (0–500 ng/mL). Cellular responses were evaluated using immunoblotting, co-immunoprecipitation, and cell viability assay. As we previously reported, IGF-I induced ACCA dephosphorylation by reducing the association between BRCA1 and phosphorylated ACCA in high glucose, and upregulated FASN abundance downstream of ACCA. However, these effects were not observed in normal glucose. Normal physiological glucose conditions completely blocked IGF-I-induced ACCA dephosphorylation and FASN upregulation. Co-immunoprecipitation studies showed that normal physiological glucose blocked ACCA dephosphorylation by increasing the association between BRCA1 and phosphorylated ACCA. Compared to high glucose, the proliferative response of breast cancer cells to IGF-I was reduced in normal glucose, whereas no difference was observed in normal mammary epithelial cells. Considering these results collectively, we conclude that normal physiological glucose promotes the novel function of BRCA1 as a metabolic restraint of IGF-I actions. These data suggest that maintaining normal glucose levels may improve BRCA1 function in breast cancer and slow down cancer progression.

Overexpression of MTFR2 Predicts Poor Prognosis of Breast Cancer.

BackgroundMitochondrial fission regulator 2 (MTFR2) has been reported to promote proliferation, migration and invasion in tumors; however, little is known about its function in breast cancer. Thus, we investigated the effect of MTFR2 expression on prognosis of breast cancer.MethodsThe expression of MTFR2 in breast cancer tissues was detected by immunohistochemistry, and overall survival (OS) and recurrence free survival (RFS) were evaluated by the Log rank test and Cox model.ResultsWe found that MTFR2 expression was significantly associated with clinical stage (P<0.001), T classification (P=0.005), N classification (P=0.001), M classification (P=0.041), HER2 expression (P= 0.001), and molecular subtypes (P=0.002), respectively. Compared with low MTFR2 expression, the patients with higher expression of MTFR2 exhibited significantly shorter OS and RFS (All P < 0.001). Both univariate and multivariate analyses showed that MTFR2 was an independent prognostic factor for OS (HR, 2.8, 95% CI 1.1–6.8, P = 0.023) and RFS (HR, 2.8, 95% CI 1.2–6.4, P = 0.015) in breast cancer patients. Moreover, in HER2 positive and TNBC subtype, the associations between high MTFR2 expression and poor OS and RFS were more pronounced.ConclusionTaken together, our results demonstrated that high MTFR2 expression was associated with poor prognosis of breast cancer patients, and such an association was more pronounced in the patients with aggressive tumors. Therefore, MTFR2 expression might be a potentially important prognostic biomarker and clinical target for patients with breast cancer.

TRIM27 Functions as a Novel Oncogene in Non-Triple-Negative Breast Cancer by Blocking Cellular Senescence through p21 Ubiquitination

In the current study, we aimed to explore the correlation between TRIM27 and breast cancer prognosis, as well as the functions of TRIM27 in breast cancer and their underlying mechanisms. Bioinformatics analyses were used to examine the correlation between TRIM27 and breast cancer prognosis. Moreover, TRIM27 knockdown and overexpression in breast cancer cells were performed to investigate its functions in breast cancer. Tamoxifen (TAM) was applied to evaluate the influence of TRIM27 on chemoresistance of breast cancer cells, while co-immunoprecipitation (coIP) was performed to identify the E3 ubiquitin ligase capability of TRIM27. High expression of TRIM27 was found in non-triple-negative breast cancer (non-TNBC) tumor tissues and was positively correlated with the mortality of non-TNBC patients. Moreover, TRIM27 could suppress non-TNBC cell apoptosis and senescence, promote cell viability and tumor growth, counteract the anti-cancer effects of TAM, and mediate ubiquitination of p21. In addition, EP300 could enhance the expression of TRIM27 and its transcription promoter H3K27ac. TRIM27, through ubiquitination of p21, might serve as a prognostic biomarker for non-TNBC prognosis. TRIM27 functions as a novel oncogene in non-TNBC cellular processes, especially suppressing cell senescence and interfering with non-TNBC chemoresistance.

Cancer-Associated Fibroblasts-Derived Exosomes Suppress Immune Cell Function in Breast Cancer via the miR-92/PD-L1 Pathway.

Cancer-associated fibroblasts (CAFs) are an essential component in the tumor microenvironment and have been reported to contribute to tumor progression through many mechanisms; however, the detailed mechanism underlying the immune-suppression effect of CAFs is not clearly defined. In this study, human breast cancer-derived CAFs were cultured, and CAF-derived exosomes in a culture medium were isolated. Using a miRNA profiles assay, we identify a significantly higher level of microRNA-92 isolated in CAFs exosomes. After treatment by CAF-derived exosomes, breast cancer cells express higher programmed cell death receptor ligand 1 (PD-L1), accompanied with increased miR-92 expression. Increased PD-L1 expression, which was induced by CAF-derived exosomes, significantly promotes apoptosis and impaired proliferation of T cells. The underlying mechanism of this effect was studied, proliferation and migration of breast cancer cells were increased after the transfection of miR-92, LATS2 was recognized as a target gene of miR-92, and further confirmed by a luciferase assay. Immunoprecipitation showed that LATS2 can interact with YAP1, chromatin immunoprecipitation confirmed that after nuclear translocation YAP1 could bind to the enhancer region of PD-L1 to promotes transcription activity. Furthermore, the animal study confirmed that CAFs significantly promoted tumor progression and impaired the function of tumor-infiltrated immune cells in vivo. Our data revealed a novel mechanism that can induce immune suppression in the tumor microenvironment.

Upregulated Long Non-Coding RNA LL22NC03-N64E9.1 Promotes the Proliferation and Migration of Human Breast Cancer Cells by Silencing Kruppel-Like Factor 2 Expression.

IntroductionRecently, the significant regulatory effects of lncRNAs on the oncogenesis and growth of tumor have been demonstrated by an increasing number of research projects. A previous study showed that LL22NC03-N64E9.1 could promote the development of colorectal cancer, especially via enhanced cell proliferation. Similarly, this lncRNA should have comparable functions in breast cancer (BC), which requires in-depth investigation. Therefore, this study was designed to explore the correlation of LL22NC03-N64E9.1 with BC.MethodsqRT-PCR was used to assess the relative expression of LL22NC03-N64E9.1 in BC tissues. Cell viability examination and colony formation experiments were performed to investigate the role of LL22NC03-N64E9.1 in BC cell’s proliferation. Transwell assays were used to explore the effects of LL22NC03-N64E9.1 on BC cell’s migration. RNA immunoprecipitation, chromosome immunoprecipitation assay and rescue experiments were performed to analyze the association of LL22NC03-N64E9.1 with target proteins and genes in BC cells.ResultsWe identified that LL22NC03-N64E9.1 is an oncogene, upregulated in BC, which was verified in a cohort of 48 pairs of BC tissues. Based on the loss-of-function experiments, silencing LL22NC03-N64E9.1 expression significantly inhibited malignancy progression. In terms of the mechanism, LL22NC03-N64E9.1 acted on the enhancer of zeste homolog 2 (EZH2) by direct binding, which promoted BC cell growth. Furthermore, in the promoters of KLF2, the trimethylation of H3K27 could be regulated by LL22NC03-N64E9.1 as the mediator.ConclusionRelying on the LL22NC03-N64E9.1/EZH2/KLF2 pathway, the lncRNA LL22NC03-N64E9.1 was significantly associated with BC development and could, therefore, be a potential therapeutic target to block BC growth.

Comprehensive analysis of the NME gene family functions in breast cancer.

BackgroundAn increasing amount of research over recent years on the anti-metastasis function of the non-metastatic (NME) gene family has been challenged, with some studies identifying its involvement in the promotion of oncogenesis. Therefore, the specific functions of the NME gene family require redefining through a comprehensive analysis of tumor heterogeneity and survival benefit. However, the functions of NME genes have not been comprehensively investigated in breast cancer (BC).MethodsIn this study, ONCOMINE, GEPIA, Kaplan-Meier plotter, cBioPortal, String, and metascape databases were utilized for comparison of the mRNA expression, patient survival and network analysis of NME-associated signaling pathways in BC patients.ResultsThe mRNA expression of NME1 and NME2 was significantly increased in BC. Additionally, high NME 1 and NME2 levels were related to poor overall survival (OS), while the upregulated expression of NME3, NME5, and NME7 indicated prolonged survival. Moreover, increased mRNA level, amplification, or deep deletions in the NME gene family were identified in approximately 41% (450/1098) of all included BC specimens. NME1 and NME2 genes displayed the highest correlation with genetic correlations of the human NME genes in BC. The following pathways were regulated by NME gene upregulation: R-HAS-380270: Recruitment of mitotic centrosome and complexes; GO:0006228: UTP biosynthetic process; R-HAS-380259: Loss of NlP from mitotic centrosomes; hsa03410: Base excision repair; and CORUM:3714: Pericenrin-GCP complex, which was significantly modulated by changes influencing the NME genes.ConclusionsCollectively, our findings revealed that the elevated expression of NME1 and NME2 could act as a biomarker and predictive tool for BC patients with poor prognosis. Furthermore, our findings indicated that NME3, NME5, and NME7 might play the roles of tumor suppressor genes, which require validation through further experiments.

Noncanonical pS727 post translational modification dictates major STAT3 activation and downstream functions in breast cancer

Activation of STAT3 via Y705-phosphorylation is well documented across multiple cancer types and thus forms the basis of canonical pathway to judge STAT3 activation. Recently, important roles of two other post translational modification (PTM) sites, i.e. S727-phosphorylation and K685-acetylation, leading to STAT3 activation are reported. However, their critical mode of function in controlling STAT3 dimerization and signaling, independent of canonical activation remains elusive. Therefore, to understand the functional relevance of each STAT3 PTMs in breast cancer (BC), cell models are developed by stable overexpression of PTM-site specific point mutants, i.e. Y705F, S727A or K685R, in a 3′UTR-STAT3 knockdown BC cell background. Results using this model system reveal novel findings showing that phosphorylation at S727 can lead to STAT3 activation independent of phosphoY705. We also demonstrate that loss of pS727 or K685ac significantly affects functional phenotypes such as cell survival and proliferation as well as downstream transcriptional activity (Twist 1, Socs3, c-Myc, Bcl-1 and Mcl-1) of STAT3. Thereafter, by utilizing a BRET biosensor for measuring STAT3 phosphorylation in live cells, a crucial role of pS727 in dictating STAT3 activation and homodimerization formation is uncovered. Further by performing retrospective IHC analysis of total and phospho-forms of STAT3 in a cohort of 76 triple negative breast cancer (TNBC) patient samples, a significant dominant expression of phosphoS727 over phosphoY705 PTM (p < 0.001) is found in STAT3 positive cases. We also focus on validating known STAT3 inhibitor molecules for their action against both pY705 and pS727 activation. This study for the first time demonstrates that an anti-helminth drug compound, Niclosamide, is capable of inactivating both phospho-PTM sites on STAT3 and exhibits excellent anticancer efficacy in preclinical TNBC tumour model.

An H3K4me3 reader, BAP18 as an adaptor of COMPASS-like core subunits co-activates ERα action and associates with the sensitivity of antiestrogen in breast cancer.

Estrogen receptor alpha (ERα) signaling pathway is essential for ERα-positive breast cancer progression and endocrine therapy resistance. Bromodomain PHD Finger Transcription Factor (BPTF) associated protein of 18kDa (BAP18) has been recognized as a crucial H3K4me3 reader. However, the whole genomic occupation of BAP18 and its biological function in breast cancer is still elusive. Here, we found that higher expression of BAP18 in ERα-positive breast cancer is positively correlated with poor prognosis. ChIP-seq analysis further demonstrated that the half estrogen response elements (EREs) and the CCCTC binding factor (CTCF) binding sites are the significant enrichment sites found in estrogen-induced BAP18 binding sites. Also, we provide the evidence to demonstrate that BAP18 as a novel co-activator of ERα is required for the recruitment of COMPASS-like core subunits to the cis-regulatory element of ERα target genes in breast cancer cells. BAP18 is recruited to the promoter regions of estrogen-induced genes, accompanied with the enrichment of the lysine 4-trimethylated histone H3 tail (H3K4me3) in the presence of E2. Furthermore, BAP18 promotes cell growth and associates the sensitivity of antiestrogen in ERα-positive breast cancer. Our data suggest that BAP18 facilitates the association between ERα and COMPASS-like core subunits, which might be an essential epigenetic therapeutic target for breast cancer.

Polycomb repressor complex 2 function in breast cancer (Review)

Epigenetic modifications are important contributors to the regulation of genes within the chromatin. The poly-comb repressive complex 2 (PRC2) is a multi-subunit protein complex that is involved in silencing gene expression through the trimethylation of lysine 27 at histone 3 (H3K27me3). The dysregulation of this modification has been associated with tumorigenicity through the increased repression of tumour suppressor genes via condensing DNA to reduce access to the transcription start site (TSS) within tumor suppressor gene promoters. In the present review, the core proteins of PRC2, as well as key accessory proteins, will be described. In addition, mechanisms controlling the recruitment of the PRC2 complex to H3K27 will be outlined. Finally, literature identifying the role of PRC2 in breast cancer proliferation, apoptosis and migration, including the potential roles of long non-coding RNAs and the miR-200 family will be summarized as will the potential use of the PRC2 complex as a therapeutic target.

Studying Adipose Tissue in the Breast Tumor Microenvironment In Vitro: Progress and Opportunities.

The breast cancer microenvironment contains a variety of stromal cells that are widely implicated in worse patient outcomes. While many in vitro models of the breast tumor microenvironment have been published, only a small fraction of these feature adipocytes. Adipocytes are a cell type increasingly recognized to have complex functions in breast cancer. In this review, we examine findings from recent examples of in vitro experiments modeling adipocytes within the local breast tumor microenvironment. Both two-dimensional and three-dimensional models of adipocytes in the breast tumor microenvironment are covered in this review and both have uncovered interesting phenomena related to breast tumor progression. Certain aspects of breast cancer and associated adipocyte biology: extracellular matrix effects, cell-cell contact, and physiological mass transport can only be examined with a three-dimensional culture platform. Opportunities remain for innovative improvements to be made to in vitro models that further increase what is known about adipocytes during breast cancer progression.

MiR-548c-3p inhibits the proliferation, migration and invasion of human breast cancer cell by targeting E2F3.

MiR-548 has been reported to be involved in a variety of tumor processes, but its function in breast cancer remains unclear. In this study, we foundthat miR-548 was low expressed in breast cancer tissues and cells compared with normal control. We then examined whether up-regulation of miR-548could improve the progression of breast cancer. Our results indicate that up-regulation of miR-548 significantly inhibits cell proliferation, migration andinvasion, and induces apoptosis in breast cancer cells. Further studies showed that miR-548 could specifically inhibit E2F3 expression. Moreover, rescuetest showed that up-regulation of E2F2 could reverse the effect of miR-548 on proliferation, migration, invasion and apoptosis of breast cancer cells. Ingeneral, miR-548 could improve the progression of breast cancer. By targeting E2F2, which may make a potential target for the treatment of breast cancer.

The Development and Treatment of Lymphatic Dysfunction in Cancer Patients and Survivors.

Breast-cancer-acquired lymphedema is routinely diagnosed from the appearance of irreversible swelling that occurs as a result of lymphatic dysfunction. Yet in head and neck cancer survivors, lymphatic dysfunction may not always result in clinically overt swelling, but instead contribute to debilitating functional outcomes. In this review, we describe how cancer metastasis, lymph node dissection, and radiation therapy alter lymphatic function, as visualized by near-infrared fluorescence lymphatic imaging. Using custom gallium arsenide (GaAs)-intensified systems capable of detecting trace amounts of indocyanine green administered repeatedly as lymphatic contrast for longitudinal clinical imaging, we show that lymphatic dysfunction occurs with cancer progression and treatment and is an early, sub-clinical indicator of cancer-acquired lymphedema. We show that early treatment of lymphedema can restore lymphatic function in breast cancer and head and neck cancer patients and survivors. The compilation of these studies provides insights to the critical role that the lymphatics and the immune system play in the etiology of lymphedema and associated co-morbidities.

Abstract 3439: FOXA1 mutations reveal distinct chromatin profiles and influence therapeutic response in breast cancer

Abstract FOXA1 is an evolutionary conserved pioneer factor that binds to condensed chromatin allowing the recruitment of other transcription factors to the DNA. Although mutations in FOXA1 are a hallmark of estrogen receptor-positive (ER+) breast cancers, it is currently unknown whether and how these mutations affect breast cancer development and response to endocrine therapies. In this work, we studied how the genome-wide chromatin recruitment, accessibility and transcriptional outcomes of recurrent FOXA1 mutations can affect therapeutic response in ER+ breast cancer. By examining the landscape of FOXA1 mutations in a cohort of 4,952 breast cancer patients, we identified several hotspot mutations, some of them present also in other malignancies and some others specific to breast cancer. In particular, we characterized three mutations in the Wing2 region and a breast-cancer specific third β strand mutation, namely SY242CS. We also showed that FOXA1 mutations are enriched in metastatic tumors and mutually exclusive with ESR1 mutations, well-known drivers of resistance to endocrine therapy. Using a clinico-genomicaly curated cohort of patients, together with in vitro and in vivo breast models, we associated FOXA1 missense mutations with a lower response to endocrine therapy. Mechanistically, by means of ChIP-seq, ATAC-seq and RNA-seq analyses, we found that FOXA1 mutations in the Wing2 loop display increased chromatin binding affinity at ER loci upon estrogen stimulation, and an enhanced ER-mediated transcription without changes in chromatin accessibility, decoupling FOXA1 Wing2 mutant binding from their pioneering function. These data correlated with the highly organized 3D conformation conferred by FOXA1 Wing2 mutations we predicted by structural modeling. Thus. the enhanced chromatin binding affinity gained by FOXA1 Wing2 mutations might be a mechanism to sustain active estrogen response even in the presence of therapeutic pressure. In contrast, breast specific SY242CS mutant shows neomorphic properties including the ability to open novel chromatin regions, and activate an alternative cistrome and transcriptome. Using an engineered luciferase reporter system, we validated that a non-canonical motif, shared by both gained accessibility and binding sites, is SY242CS-specific. Structural modeling of the binding of WT or SY242CS FOXA1 to this new motif revealed that SY242CS undergoes conformational change that results in a tight interaction with the new DNA motif, not observed in WT FOXA1. Taken together, our findings provide mechanistic insights into how FOXA1 mutations modulate its function in breast cancer to dictate malignant progression and response to endocrine therapy. More broadly, these results position FOXA1 mutations as potential biomarkers of response and potential targets for the treatment of metastatic ER+ breast cancer. Citation Format: Amaia Arruabarrena-Aristorena, Jesper LV Maag, Srushti Kittane, Yanyan Cai, Jane Park, Pedram Razavi, Lorenzo Ferrando, Pier Selenica, Wouter R. Karthaus, Srinivasaraghavan Kannan, Emiliano Cocco, Sik Y. Ho, Daisylyn Senna Tan, Mirna Sallaku, Charles L. Sawyers, Jorge S. Reis-Fihlo, Chandra S. Verma, Ralf Jauch, Richard Koche, José Baselga, Eneda Toska, Maurizio Scaltriti. FOXA1 mutations reveal distinct chromatin profiles and influence therapeutic response in breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3439.

Abstract 5034: Effect of estrogen on heteronemin-induced anti-proliferation in breast cancer cells

Abstract Estrogen, 17β-estradiol (E2) has multiple functions in breast cancers including stimulating cancer growth and interfering with chemotherapeutic efficacy. Heteronemin, a marine sesterterpenoid-type natural product, processes anti-proliferative effect in cancer cells. In the current study, we investigate the antitumor mechanism of heteronemin in breast cancer cells and further explore its molecular targets. Heteronemin exhibited potent cytotoxic effects against breast cancer cells. On the other hand, E2 stimulated cancer cell growth. Heteronemin and E2 showed different effects on gene expression of proliferation, angiogenesis or growth factor receptors in breast cancer cells. NanoString® analysis was further used to detect mRNAs, heteronemin repressed gene expression of transforming growth factor (TGF)-β, mothers against decapentaplegic homolog (SMAD) and PCNA, whose protein products play important roles in regulating cell growth, angiogenesis, and metastasis. The results indicate that heteronemin was able to modulate cell adhesion, expression of extracellular matrix (ECM) receptors, TGF-β pathway, cell motility, membrane integration, metastasis response, matrix metalloproteinase (MMP) remodeling, regulation of metabolism, sprouting angiogenesis, transcription factors, and vasculogenesis in breast cancer cells. However, those effects were partially reversed by E2. Furthermore, Heteronemin and E2 altered several signaling transduction pathways. In summary, this study provides insight into the complex pathways by which anti-proliferation is induced by heteronemin in E2-depleted and -repleted environments. Citation Format: Zi-Lin Li, Yi-shin Pan, Tung-Yung Huang, Ya-Jung Shih, Yi-Ru Chen, Heng-Yuan Tang, Jacqueline Whang-Peng, Hung-Yun Lin, Paul J. Davis, Kuan Wang. Effect of estrogen on heteronemin-induced anti-proliferation in breast cancer cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5034.

MicroRNA‑137 exerts protective effects on hypoxia‑induced cell injury by inhibiting autophagy/mitophagy and maintaining mitochondrial function in breast cancer stem‑like cells.

Breast cancer stem-like cells (BCSCs) have been identified and proven to play critical roles in tumorigenesis and progression. Hypoxia is a common pathologic feature of breast cancer and potentially, at least in part, regulates the initiation, progression, and recurrence of breast cancer. However, less is known about how hypoxia regulates BCSCs. As several well-known microRNAs respond to hypoxia, we aimed to determine how hypoxia regulates the physiological processes of BCSCs by regulating the corresponding microRNAs. As expected, microRNA-137 (miRNA-137 or miR-137) was downregulated upon hypoxic exposure, indicating that it may play critical roles in BCSCs. Introduction of miR-137 mimics promoted cell cycle entry and inhibited hypoxia-induced cell apoptosis as determined by cell cycle assay and apoptosis assay. By detecting mitochondrial reactive oxygen species (ROS), it was found that miR-137 inhibited ROS accumulation induced by hypoxic exposure and thus suppressed cell apoptosis. Introduction of miR-137 mimics under hypoxia inhibited mitophagy/autophagy by targeting FUN14 domain containing 1 (Fundc1) and thus promoted mitochondrial functions, including mitochondrial mass, ATP synthesis and mitochondrial transcriptional activity, which was similar to the effects of Fundc1 knockdown by specific siRNA. Based on these observations, we hypothesized that the survival of BCSCs under hypoxia was mediated by miR-137 by regulating mitochondrial dysfunction. We demonstrated here that the introduction of exogenous miR-137 promoted mitochondrial function, indicating that it may be a potential therapeutic target in BCSCs.

MiR-204/COX5A axis contributes to invasion and chemotherapy resistance in estrogen receptor-positive breast cancers.

Breast cancer is the most common cancer among women worldwide, with 70% being estrogen receptor-positive (ER+). Although ER-targeted treatment is effective in treating ER+breast cancer, chemoresistance and metastasis still prevail. Outcome-predictable biomarkers can help improve patient prognosis. Through the analysis of the Array Express database, The Cancer Genome Atlas-Breast Cancer datasets, and breast tumor tissue array results, we found that cytochrome c oxidase subunit 5a (COX5A) was related to poor prognosis of ER+breast cancer. Further studies revealed that COX5A was positively associated with metastasis and chemoresistance in ER+breast cancer. In vitro experiments showed that knockdown of COX5A was accompanied by a decrease in ERα expression, cell cycle arrest, and epithelial-mesenchymal transition blockade, resulting in an inhibition of proliferation and invasion. Knockdown of COX5A enhanced the chemosensitivity of breast cancer cells by decreasing adenosine triphosphate and increasing reactive oxygen species levels. We report that miR-204 can target and inhibit the expression of COX5A, thus, reversing the functions of COX5A in ER+breast cancer cells. We found that COX5A may serve as a prognostic biomarker in ER+breast cancer.