Primary breast tumor-derived cellular models: characterization of tumorigenic, metastatic, and cancer-associated fibroblasts in dissociated tumor (DT) cultures

Automatic detection of circulating tumor cells and cancer associated fibroblasts using deep learning

Circulating tumor cells (CTCs) and cancer-associated fibroblasts (CAFs) from whole blood are emerging as important biomarkers that potentially aid in cancer diagnosis and prognosis. The microfilter technology provides an efficient capture platform for them but is confounded by two challenges. First, uneven microfilter surfaces makes it hard for commercial scanners to obtain images with all cells in-focus. Second, current analysis is labor-intensive with long turnaround time and user-to-user variability. Here we addressed the first challenge through developing a customized imaging system and data pre-processing algorithms. Utilizing cultured cancer and CAF cells captured by microfilters, we showed that images from our custom system are 99.3% in-focus compared to 89.9% from a top-of-the-line commercial scanner. Then we developed a deep-learning-based method to automatically identify tumor cells serving to mimic CTC (mCTC) and CAFs. Our deep learning method achieved precision and recall of 94% (± 0.2%) and 96% (± 0.2%) for mCTC detection, and 93% (± 1.7%) and 84% (± 3.1%) for CAF detection, significantly better than a conventional computer vision method, whose numbers are 92% (± 0.2%) and 78% (± 0.3%) for mCTC and 58% (± 3.9%) and 56% (± 3.5%) for CAF. Our custom imaging system combined with deep learning cell identification method represents an important advance on CTC and CAF analysis.

Heterotypic clustering of circulating tumor cells and circulating cancer-associated fibroblasts facilitates breast cancer metastasis

BACKGROUND

Cancer-associated fibroblasts (CAFs) are recruited to the tumor microenvironment (TME) and are critical drivers of breast cancer (BC) malignancy. Circulating tumor cells (CTCs) travel through hematogenous routes to establish metastases. CTCs circulate both individually and, more rarely, in clusters with other cell types. Clusters of CTCs have higher metastatic potential than single CTCs. Previously, we identified circulating CAFs (cCAFs) in patients with BC and found that while healthy donors had no CTCs or cCAFs, both were present in most Stage IV patients. cCAFs circulate individually, as cCAF-cCAF homotypic clusters, and in heterotypic clusters with CTCs.

METHODS

In this study, we evaluate CTCs, cCAFs, and heterotypic cCAF-CTC clusters in patients with stage I-IV BC. We evaluate the association of heterotypic clusters with BC disease progression and metastasis in a spontaneous mouse model. Using previously established primary BC and CAF cell lines, we examine the metastatic propensity of heterotypic cCAF-CTC clusters in orthotopic and tail vein xenograft mouse models of BC. Using an in vitro clustering assay, we determine factors that may be involved in clustering between CAF and BC cells.

RESULTS

We report that the dissemination of CTCs, cCAFs, and clusters is an early event in BC progression, and we find these clusters in all clinical stages of BC. Furthermore, cCAFs-CTC heterotypic clusters have a higher metastatic potential than homotypic CTC clusters in vivo. We also demonstrate that the adhesion and stemness marker CD44, found on a subset of CTCs and CAF cells, is  involved in heterotypic clustering of these cells.

CONCLUSION

We identify a novel subset of circulating tumor cell clusters that are enriched with stromal CAF cells in BC patient blood and preclinical mouse models of BC metastasis. Our data suggest that clustering of CTCs with cCAFs augments their metastatic potential and that CD44 might be an important mediator of heterotypic clustering of cCAFs and BC cells.

The LINC01119-SOCS5 axis as a critical theranostic in triple-negative breast cancer

The development of triple-negative breast cancer (TNBC) is critically regulated by certain tumor-microenvironment-associated cells called mesenchymal stem/stromal cells (MSCs), which we and others have shown promote TNBC progression by activating pro-malignant signaling in neighboring cancer cells. Characterization of these cascades would better our understanding of TNBC biology and bring about therapeutics that eliminate the morbidity and mortality associated with advanced disease. Here, we focused on the emerging class of RNAs called long non-coding RNAs or lncRNAs and utilized a MSC-supported TNBC progression model to identify specific family members of functional relevance to TNBC pathogenesis. Indeed, although some have been described to play functional roles in TNBC, activities of lncRNAs as mediators of tumor-microenvironment-driven TNBC development remain to be fully explored. We report that MSCs stimulate robust expression of LINC01119 in TNBC cells, which in turn induces suppressor of cytokine signaling 5 (SOCS5), leading to accelerated cancer cell growth and tumorigenesis. We show that LINC01119 and SOCS5 exhibit tight correlation across multiple breast cancer gene sets and that they are highly enriched in TNBC patient cohorts. Importantly, we present evidence that the LINC01119-SOCS5 axis represents a powerful prognostic indicator of adverse outcomes in TNBC patients, and demonstrate that its repression severely impairs cancer cell growth. Altogether, our findings identify LINC01119 as a major driver of TNBC development and delineate critical non-coding RNA theranostics of potential translational utility in the management of advanced TNBC, a class of tumors in most need of effective and targeted therapy.

Human Primary Breast Cancer Stem Cells Are Characterized by Epithelial-Mesenchymal Plasticity

Triple-negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer, with only limited treatment options available. Recently, cancer stem cells (CSCs) have emerged as the potential drivers of tumor progression due to their ability to both self-renew and give rise to differentiated progeny. The CSC state has been linked to the process of epithelial-mesenchymal transition (EMT) and to the highly flexible state of epithelial-mesenchymal plasticity (EMP). We aimed to establish primary breast cancer stem cell (BCSC) cultures isolated from TNBC specimens. These cells grow as tumor spheres under anchorage-independent culture conditions in vitro and reliably form tumors in mice when transplanted in limiting dilutions in vivo. The BCSC xenograft tumors phenocopy the original patient tumor in architecture and gene expression. Analysis of an EMT-related marker profile revealed the concomitant expression of epithelial and mesenchymal markers suggesting an EMP state for BCSCs of TNBC. Furthermore, BCSCs were susceptible to stimulation with the EMT inducer TGF-β1, resulting in upregulation of mesenchymal genes and enhanced migratory abilities. Overall, primary BCSC cultures are a promising model close to the patient that can be used both in vitro and in vivo to address questions of BCSC biology and evaluate new treatment options for TNBC.

Spindle assembly checkpoint gene BUB1B is essential in breast cancer cell survival

PURPOSE

The study aimed to investigate the role of spindle assembly checkpoint (SAC) in cancer cells with compromised genomic integrity. Chromosomal instability (CIN) gives cancer cells an adaptive advantage. However, maintaining the balance of this instability is crucial for the survival of cancer cells as it could lead them to the mitotic catastrophe. Therefore, cancer cells adapt to the detrimental effects of CIN. We hypothesized that changes in SAC might be one such adaptation mechanism. The focus of the study was BUB1B, an integral part of the checkpoint.

METHODS

Clinical datasets were analyzed to compare expression levels of SAC genes in normal tissue vs. breast carcinoma. The effects of the reduction of BUB1B expression was examined utilizing RNA interference method with siRNAs. In vitro viability, clonogenicity, apoptosis, and SAC activity levels of a variety of breast cancer (BrCa) cell lines, as well as in vivo tumorigenicity of the triple-negative breast cancer (TNBC) cell line MDA-MB-468, were tested. Additionally, the chromosomal stability of these cells was tested by immunofluorescence staining and flow cytometry.

RESULTS

In clinical breast cancer datasets, SAC genes were elevated in BrCa with BUB1B having the highest fold change. BUB1B overexpression was associated with a decreased probability of overall survival. The knockdown of BUB1B resulted in reduced viability and clonogenicity in BrCa cell lines and a significant increase in apoptosis and cell death. However, the viability and apoptosis levels of the normal breast epithelial cell line, MCF12A, were not affected. BUB1B knockdown also impaired chromosome alignment and resulted in acute chromosomal abnormalities. We also showed that BUB1B knockdown on the MDA-MB-468 cell line decreases tumor growth in mice.

CONCLUSIONS

A functional spindle assembly checkpoint is essential for the survival of BrCa cells. BUB1B is a critical factor in SAC, and therefore breast cancer cell survival. Impairment of BUB1B has damaging effects on cancer cell viability and tumorigenicity, especially on the more aggressive variants of BrCa.

Contrasting activities of estrogen receptor beta isoforms in triple negative breast cancer

PURPOSE

Triple negative breast cancer (TNBC), an aggressive subtype of breast cancer, lacks the three major receptors for predicting outcome or targeting therapy. Hence, our aim was to evaluate the potential of estrogen receptor beta (ERβ) as a possible endocrine therapy target in TNBC.

METHODS

The expression and prognostic effect of ERβ isoforms were analyzed using TCGA breast tumor data, and the expression of ERβ isoform mRNA and protein in TNBC cell lines was assayed. Endogenous ERβ2 and ERβ5 were knocked down with siRNA, and ERβ2, ERβ5, and ERβ1 were upregulated using a doxycycline-inducible lentiviral system. Cell proliferation, migration and invasion, and specific gene expressions were evaluated.

RESULTS

ERβ2 and ERβ5 were the predominant endogenous forms of ERβ in TNBC tumors and cell lines. High ERβ2 predicted worse clinical outcome. Knockdown of endogenous ERβ2/ERβ5 in cell lines suppressed proliferation, migration and invasion, and downregulated proto-oncogene survivin expression. ERβ2/ERβ5 upregulation did the reverse, increasing survivin and these cell activities. ERβ1 was barely detectable in TNBC cell lines, but its upregulation reduced survivin, increased tumor suppressor expression (E-cadherin and cystatins), and suppressed proliferation, migration and invasion in both ligand-independent and dependent manners, suggesting the possible translational benefit of ERβ ligands.

CONCLUSIONS

ERβ2/ERβ5 and ERβ1 exhibit sharply contrasting activities in TNBC cells. Our findings imply that delineating the absolute amounts and relative ratios of the different ERβ isoforms might have prognostic and therapeutic relevance, and could enable better selection of optimal approaches for treatment of this often aggressive form of breast cancer.

Suppression of Tumor Growth, Metastasis, and Signaling Pathways by Reducing FOXM1 Activity in Triple Negative Breast Cancer

Simple Summary

Triple negative breast cancer is an aggressive subtype of breast cancer that frequently metastasizes. Because the transcription factor FOXM1 is highly upregulated in triple negative breast cancer and controls many cell activities that lead to cancer progression and metastasis, we sought to determine if FOXM1 inhibitory compounds could effectively suppress the invasiveness and progression of triple negative breast cancer cells and tumors. Our findings show that these compounds inhibit cell motility, invasiveness, and the expression of important proteins associated with epithelial to mesenchymal transition. These compounds also suppressed the proliferation and metastatic outgrowth of triple negative breast tumors. Thus, these findings highlight the crucial role of FOXM1 in promoting the progression and metastasis of these cancers, and suggest that FOXM1 inhibitory compounds may have therapeutic potential and prove beneficial in intervention against triple negative breast cancer.

Abstract

Metastasis-related complications account for the overwhelming majority of breast cancer mortalities. Triple negative breast cancer (TNBC), the most aggressive breast cancer subtype, has a high propensity to metastasize to distant organs, leading to poor patient survival. The forkhead transcription factor, FOXM1, is especially upregulated and overexpressed in TNBC and is known to regulate multiple signaling pathways that control many key cancer properties, including proliferation, invasiveness, stem cell renewal, and therapy resistance, making FOXM1 a critical therapeutic target for TNBC. In this study, we test the effectiveness of a novel class of 1,1-diarylethylene FOXM1 inhibitory compounds in suppressing TNBC cell migration, invasion, and metastasis using in vitro cell culture and in vivo tumor models. We show that these compounds inhibit the motility and invasiveness of TNBC MDA-MB-231 and DT28 cells, along with reducing the expression of important epithelial to mesenchymal transition (EMT) associated genes. Further, orthotopic tumor studies in NOD-SCID-gamma (NSG) mice demonstrate that these compounds reduce FOXM1 expression and suppress TNBC tumor growth as well as distant metastasis. Gene expression and protein analyses confirm the decreased levels of EMT factors and FOXM1-regulated target genes in tumors and metastatic lesions in the inhibitor-treated animals. The findings suggest that these FOXM1 suppressive compounds may have therapeutic potential in treating triple negative breast cancer, with the aim of reducing tumor progression and metastatic outgrowth.

In vivo antitumor activity by dual stromal and tumor-targeted oncolytic measles viruses

The tumor stroma acts as a barrier that limits the efficacy of systemically administered oncolytic viruses (OV). We previously demonstrated that stromal-selective, retargeted oncolytic measles viruses (MVs) delay in vivo tumor progression. To further characterize the contribution of stromal targeting to MV's overall in vivo efficacy in an experimental cancer model, a dual targeted oncolytic measles virus (MV-CD46-muPA) able to simultaneously infect murine stromal (via murine uPAR) and human cancer (via CD46) cells was developed. MV-CD46-muPA infected, replicated, and induced cytotoxicity in both murine and human cancer cells. Viral infection was successfully transferred from stromal to tumor cells in vitro, leading to tumor cell oncolysis. Systemic administration of MV-CD46-muPA led to improved antitumor effects in colon (HT-29) cancer xenografts compared to vehicle or CD46 only targeted MVs. These effects were associated with improved tumor viral deposition, increased apoptosis, and decreases in murine stromal endothelial cells and fibroblasts. MV-CD46-muPA modulated cell cycle, survival, proliferation, and metabolic pathways, as determined by functional proteomic analysis of treated tumors. The above findings further validate the concept that dual stromal and tumor cell viral targeting enhances the therapeutic effects of systemically administered OVs and support further preclinical and clinical development of stromal directed virotherapies.

Suppression of FOXM1 activities and breast cancer growth in vitro and in vivo by a new class of compounds

The transcription factor FOXM1 is upregulated and overexpressed in aggressive, therapy-resistant forms of hormone receptor-positive and triple negative breast cancers, and is associated with less good patient survival. FOXM1 signaling is also a key driver in many other cancers. Here, we identify a new class of compounds effective in suppressing FOXM1 activity in breast cancers, and displaying good potency for antitumor efficacy. The compounds bind directly to FOXM1 and alter its proteolytic sensitivity, reduce the cellular level of FOXM1 protein by a proteasome- dependent process, and suppress breast cancer cell proliferation and cell cycle progression and increase apoptosis. RNA-seq and gene set enrichment analyses indicate that the compounds decrease expression of FOXM1-regulated genes and suppress gene ontologies under FOXM1 regulation. Several compounds have favorable pharmacokinetic properties and show good tumor suppression in preclinical breast tumor models. These compounds may be suitable for further clinical evaluation in targeting aggressive breast cancers driven by FOXM1.

Paget's disease of the nipple in a Her2-positive breast cancer xenograft model

PURPOSE

Paget's disease (PD) of the breast is an uncommon disease of the nipple usually accompanied by an underlying carcinoma, often HER2 + , and accounting for 0.5-5% of all breast cancer. To date, histogenesis of PD of the breast remains controversial, as two theories-transformation and epidermotropic-have been proposed to explain this disease. Currently, animal models recapitulating PD of the nipple have not been described.

METHODS

HER2-enriched DT13 breast cancer cells were injected into the mammary fat pad of NOD scid gamma null (NSG) female mice. Immunohistochemical staining and pathological studies were performed on tumor samples, and diagnosis of PD of the nipple was confirmed by expression of proteins characteristic of Paget cells (epidermal growth factor 2 (HER2), androgen receptor (AR), cytokeratin 7 (CK7), cytokeratin 8/18 (CK8/18), and mucin 1 (MUC1)). In addition, DT13 cells grown in 2D culture and in soft agar assays were sensitive to in vitro treatment with pharmacological inhibitors targeting Her2, adenylyl cyclase, mTOR, and PI3K signaling pathways.

RESULTS

Mice developed tumors and nipple lesions that were detected exclusively on the tumor-bearing mammary fat pad. Tumor cells were positive for proteins characteristic of Paget cells. In vitro, DT13 cells were sensitive to inhibition of Her2, adenylyl cyclase, mTOR, and PI3K signaling pathways.

CONCLUSIONS

Our results suggest that injection of HER2 + DT13 cells into the mammary fat pad of NSG mice recapitulates critical aspects of the pathophysiology of PD of the nipple, supporting the epidermotropic theory as the more likely to explain the histogenesis of this disease.

Microenvironmental Regulation of Long Noncoding RNA LINC01133 Promotes Cancer Stem Cell-Like Phenotypic Traits in Triple-Negative Breast Cancers

The fibrotic tumor microenvironment is a critical player in the pathogenesis of triple-negative breast cancers (TNBCs), with the presence of fibroblastic infiltrates particularly correlating with tumors that are clinically advanced. On this front, we previously demonstrated that TNBCs are highly enriched in fibroblastic stromal progenitor cells called mesenchymal stem/stromal cells (MSCs) and that such cells play critical roles in promoting TNBC initiation and progression. How TNBC cells respond to MSC stimulation, however, is not fully understood, and stands to reveal contextual signals used by TNBC cells during tumor development and provide biomarkers and therapeutic targets of pertinence to TNBC management. Here, we report that MSCs strongly induced the long noncoding RNA (lncRNA) LINC01133 in neighboring TNBC cells. Indeed, although lncRNAs have been tightly associated with cancer development, their contributions to breast cancer in general, and to TNBC pathogenesis in particular, have not been fully elucidated, and we set out to determine if LINC01133 regulated malignant traits in TNBC cells. We establish that LINC01133 is sufficient, on its own, in promoting phenotypic and growth characteristics of cancer stem cell-like cells, and that it is a direct mediator of the MSC-triggered miR-199a-FOXP2 pathway in TNBC models. Furthermore, we show that LINC01133 is a critical regulator of the pluripotency-determining gene Kruppel-Like Factor 4 (KLF4), and that it represents a biomarker and prognosticator of disease outcome in the clinic. Collectively, our findings introduce LINC01133 as a novel functional driver of malignancy and a potential theranostic in TNBC. Stem Cells 2019;37:1281-1292.

A novel RNA aptamer identifies plasma membrane ATP synthase beta subunit as an early marker and therapeutic target in aggressive cancer

PURPOSE

Primary breast and prostate cancers can be cured, but metastatic disease cannot. Identifying cell factors that predict metastatic potential could guide both prognosis and treatment.

METHODS

We used Cell-SELEX to screen an RNA aptamer library for differential binding to prostate cancer cell lines with high vs. low metastatic potential. Mass spectroscopy, immunoblot, and immunohistochemistry were used to identify and validate aptamer targets. Aptamer properties were tested in vitro, in xenograft models, and in clinical biopsies. Gene expression datasets were queried for target associations in cancer.

RESULTS

We identified a novel aptamer (Apt63) that binds to the beta subunit of F1Fo ATP synthase (ATP5B), present on the plasma membrane of certain normal and cancer cells. Apt63 bound to plasma membranes of multiple aggressive breast and prostate cell lines, but not to normal breast and prostate epithelial cells, and weakly or not at all to non-metastasizing cancer cells; binding led to rapid cell death. A single intravenous injection of Apt63 induced rapid, tumor cell-selective binding and cytotoxicity in MDA-MB-231 xenograft tumors, associated with endonuclease G nuclear translocation and DNA fragmentation. Apt63 was not toxic to non-transformed epithelial cells in vitro or adjacent normal tissue in vivo. In breast cancer tissue arrays, plasma membrane staining with Apt63 correlated with tumor stage (p < 0.0001, n = 416) and was independent of other cancer markers. Across multiple datasets, ATP5B expression was significantly increased relative to normal tissue, and negatively correlated with metastasis-free (p = 0.0063, 0.00039, respectively) and overall (p = 0.050, 0.0198) survival.

CONCLUSION

Ecto-ATP5B binding by Apt63 may disrupt an essential survival mechanism in a subset of tumors with high metastatic potential, and defines a novel category of cancers with potential vulnerability to ATP5B-targeted therapy. Apt63 is a unique tool for elucidating the function of surface ATP synthase, and potentially for predicting and treating metastatic breast and prostate cancer.

Vitamin C supplementation expands the therapeutic window of BETi for triple negative breast cancer

Background

Bromodomain and extra-terminal inhibitors (BETi) have shown efficacy for the treatment of aggressive triple negative breast cancer (TNBC). However, BETi are plagued by a narrow therapeutic window as manifested by severe toxicities at effective doses. Therefore, it is a limitation to their clinical implementation in patient care.

Methods

The impact of vitamin C on the efficacy of small compounds including BETi was assessed by high-throughput screening. Co-treatment of TNBC by BETi especially JQ1 and vitamin C was evaluated in vitro and in vivo.

Findings

High-throughput screening revealed that vitamin C improves the efficacy of a number of structurally-unrelated BETi including JQ1, I-BET762, I-BET151, and CPI-203 in treating TNBC cells. The synergy between BETi and vitamin C is due to suppressed histone acetylation (H3ac and H4ac), which is in turn caused by upregulated histone deacetylase 1 (HDAC1) expression upon vitamin C addition. Treatment with JQ1 at lower doses together with vitamin C induces apoptosis and inhibits the clonogenic ability of cultured TNBC cells. Oral vitamin C supplementation renders a sub-therapeutic dose of JQ1 able to inhibit human TNBC xenograft growth and metastasis in mice.

Interpretation

Vitamin C expands the therapeutic window of BETi by sensitizing TNBC to BETi. Using vitamin C as a co-treatment, lower doses of BETi could be used to achieve an increased therapeutic index in patients, which will translate to a reduced side effect profile.

Fund

University of Miami Sylvester Comprehensive Cancer Center, Bankhead Coley Cancer Research program (7BC10), Flight Attendant Medical Research Institute, and NIH R21CA191668 (to GW) and 1R56AG061911 (to CW and CHV).

Proteomic analysis identifies highly expressed plasma membrane proteins for detection and therapeutic targeting of specific breast cancer subtypes

In recent years, there has been an emphasis on personalizing breast cancer treatment in order to avoid the debilitating side effects caused by broad-spectrum chemotherapeutic drug treatment. Development of personalized medicine requires the identification of proteins that are expressed by individual tumors. Herein, we reveal the identity of plasma membrane proteins that are overexpressed in estrogen receptor α-positive, HER2-positive, and triple negative breast cancer cells. The proteins we identified are involved in maintaining protein structure, intracellular homeostasis, and cellular architecture; enhancing cell proliferation and invasion; and influencing cell migration. These proteins may be useful for breast cancer detection and/or treatment.

Molecular Effects of Stromal-Selective Targeting by uPAR-Retargeted Oncolytic Virus in Breast Cancer

The tumor microenvironment (TME) is a relevant target for novel biological therapies. MV-m-uPA and MV-h-uPA are fully retargeted, species-specific, oncolytic measles viruses (MV) directed against murine or human urokinase receptor (PLAUR/uPAR), expressed in tumor and stromal cells. The effects of stromal-selective targeting by uPAR-retargeted MVs were investigated. In vitro infection, virus-induced GFP expression, and cytotoxicity by MV-h-uPA and MV-m-uPA were demonstrated in human and murine cancer cells and cancer-associated fibroblasts in a species-specific manner. In a murine fibroblast/human breast cancer 3D coculture model, selective fibroblast targeting by MV-m-uPA inhibited breast cancer cell growth. Systemic administration of murine-specific MV-m-uPA in mice bearing human MDA-MB-231 xenografts was associated with a significant delay in tumor progression and improved survival compared with controls. Experiments comparing tumor (MV-h-uPA) versus stromal (MV-m-uPA) versus combined virus targeting showed that tumor and stromal targeting was associated with improved tumor control over the other groups. Correlative studies confirmed in vivo viral targeting of tumor stroma by MV-m-uPA, increased apoptosis, and virus-induced differential regulation of murine stromal genes associated with inflammatory, angiogenesis, and survival pathways, as well as indirect regulation of human cancer pathways, indicating viral-induced modulation of tumor-stroma interactions. These data demonstrate the feasibility of stromal-selective targeting by an oncolytic MV, virus-induced modulation of tumor-stroma pathways, and subsequent tumor growth delay. These findings further validate the critical role of stromal uPAR in cancer progression and the potential of oncolytic viruses as antistromal agents.Implications: The current report demonstrates for the first time the biological, in vitro, and in vivo antitumor and molecular effects of stromal selective targeting by an oncolytic virus. Mol Cancer Res; 15(10); 1410-20. ©2017 AACR.

VEGFA links self-renewal and metastasis by inducing Sox2 to repress miR-452, driving Slug

Cancer stem cells (CSC) appear to have increased metastatic potential, but mechanisms underlying this are poorly defined. Here we show that VEGFA induction of Sox2 promotes EMT and tumor metastasis. In breast lines and primary cancer culture, VEGFA rapidly upregulates SOX2 expression, leading to SNAI2 induction, EMT, increased invasion and metastasis. We show Sox2 downregulates miR-452, which acts as a novel metastasis suppressor to directly target the SNAI2 3′-untranslated region (3′-UTR). VEGFA stimulates Sox2- and Slug-dependent cell invasion. VEGFA increases lung metastasis in vivo, and this is abrogated by miR-452 overexpression. Furthermore, SNAI2 transduction rescues metastasis suppression by miR-452. Thus, in addition to its angiogenic action, VEGFA upregulates Sox2 to drive stem cell expansion, together with miR-452 loss and Slug upregulation, providing a novel mechanism whereby cancer stem cells acquire metastatic potential. Prior work showed EMT transcription factor overexpression upregulates CSC. Present work indicates that stemness and metastasis are a two-way street: Sox2, a major mediator of CSC self-renewal, also governs the metastatic process.

Integration of Breast Cancer Secretomes with Clinical Data Elucidates Potential Serum Markers for Disease Detection, Diagnosis, and Prognosis

Cancer cells secrete factors that influence adjacent cell behavior and can lead to enhanced proliferation and metastasis. To better understand the role of these factors in oncogenesis and disease progression, estrogen and progesterone receptor positive MCF-7 cells, triple negative breast cancer MDA-MB-231, DT22, and DT28 cells, and MCF-10A non-transformed mammary epithelial cells were grown in 3D cultures. A special emphasis was placed on triple negative breast cancer since these tumors are highly aggressive and no targeted treatments are currently available. The breast cancer cells secreted factors of variable potency that stimulated proliferation of the relatively quiescent MCF-10A cells. The conditioned medium from each cell line was subjected to mass spectrometry analysis and a variety of secreted proteins were identified including glycolytic enzymes, proteases, protease inhibitors, extracellular matrix proteins, and insulin-like growth factor binding proteins. An investigation of the secretome from each cell line yielded clues about strategies used for breast cancer proliferation and metastasis. Some of the proteins we identified may be useful in the development of a serum-based test for breast cancer detection, diagnosis, prognosis, and monitoring.

Interactions between Adipocytes and Breast Cancer Cells Stimulate Cytokine Production and Drive Src/Sox2/miR-302b-Mediated Malignant Progression

Consequences of the obesity epidemic on cancer morbidity and mortality are not fully appreciated. Obesity is a risk factor for many cancers, but the mechanisms by which it contributes to cancer development and patient outcome have yet to be fully elucidated. Here, we examined the effects of coculturing human-derived adipocytes with established and primary breast cancer cells on tumorigenic potential. We found that the interaction between adipocytes and cancer cells increased the secretion of proinflammatory cytokines. Prolonged culture of cancer cells with adipocytes or cytokines increased the proportion of mammosphere-forming cells and of cells expressing stem-like markers in vitro. Furthermore, contact with immature adipocytes increased the abundance of cancer cells with tumor-forming and metastatic potential in vivo. Mechanistic investigations demonstrated that cancer cells cultured with immature adipocytes or cytokines activated Src, thus promoting Sox2, c-Myc, and Nanog upregulation. Moreover, Sox2-dependent induction of miR-302b further stimulated cMYC and SOX2 expression and potentiated the cytokine-induced cancer stem cell-like properties. Finally, we found that Src inhibitors decreased cytokine production after coculture, indicating that Src is not only activated by adipocyte or cytokine exposures, but is also required to sustain cytokine induction. These data support a model in which cancer cell invasion into local fat would establish feed-forward loops to activate Src, maintain proinflammatory cytokine production, and increase tumor-initiating cell abundance and metastatic progression. Collectively, our findings reveal new insights underlying increased breast cancer mortality in obese individuals and provide a novel preclinical rationale to test the efficacy of Src inhibitors for breast cancer treatment.

Identification of Cancer-Associated Fibroblasts in Circulating Blood from Patients with Metastatic Breast Cancer

Metastasis is facilitated by cancer-associated fibroblasts (CAF) in the tumor microenvironment through mechanisms yet to be elucidated. In this study, we used a size-based microfilter technology developed by our group to examine whether circulating CAF identified by FAP and α-SMA co-expression (cCAF) could be distinguished in the peripheral blood of patients with metastatic breast cancer. In a pilot study of patients with breast cancer, we detected the presence of cCAFs in 30/34 (88%) patients with metastatic disease (MET group) and in 3/13 (23%) patients with localized breast cancer (LOC group) with long-term disease-free survival. No cCAFs as defined were detected in healthy donors. Further, both cCAF and circulating tumor cells (CTC) were significantly greater in the MET group compared with the LOC group. Thus, the presence of cCAF was associated with clinical metastasis, suggesting that cCAF may complement CTC as a clinically relevant biomarker in metastatic breast cancer.

Secondary anchor targeted cell release

Personalized medicine offers the promise of tailoring therapy to patients, based on their cellular biomarkers. To achieve this goal, cellular profiling systems are needed that can quickly and efficiently isolate specific cell types without disrupting cellular biomarkers. Here we describe the development of a unique platform that facilitates gentle cell capture via a secondary, surface-anchoring moiety, and cell release. The cellular capture system consists of a glass surface functionalized with APTES, d-desthiobiotin, and streptavidin. Biotinylated mCD11b and hIgG antibodies are used to capture mouse macrophages (RAW 264.7) and human breast cancer (MCF7-GFP) cell lines, respectively. The surface functionalization is optimized by altering assay components, such as streptavidin, d-desthiobiotin, and APTES, to achieve cell capture on 80% of the functionalized surface and cell release upon biotin treatment. We also demonstrate an ability to capture 50% of target cells within a dual-cell mixture. This engineering advancement is a critical step towards achieving cell isolation platforms for personalized medicine.

Hierarchical paracrine interaction of breast cancer associated fibroblasts with cancer cells via hMAPK-microRNAs to drive ER-negative breast cancer phenotype

Multiple juxtacrine and paracrine interactions occur between cancer cells and non-cancer cells of the tumor microenvironment (TME) that direct tumor progression. Cancer Associated Fibroblasts (CAFs) are an integral component of the TME, and the majority of breast tumor stroma is comprised of CAFs. Heterotypic interactions between cancer cells and non-cancer cells of the TME occur via soluble agents, including cytokines, hormones, growth factors, and secreted microRNAs. We previously identified a microRNA signature indicative of hyperactive MAPK signaling (hMAPK-miRNA signature) that significantly associated with reduced recurrence-free and overall survival. Here we report that the hMAPK-miRNA signature associates with a high metric of stromal cell infiltrate, and we investigate the role of microRNAs, particularly hMAPK-microRNAs, secreted by CAFs on estrogen receptor (ER) expression in breast cancer cells. ER-positive MCF-7/ltE2- cells were treated with conditioned media (CM) from CAFs derived from breast cancers of different PAM50 subtypes (CAFBAS, CAFHER2, and CAFLA). CAF CM isolated specifically from ER-negative primary breast tumors led to ER repression in vitro. Nanoparticle tracking analysis and transmission electron microscopy confirmed the presence of CAF-secreted exosomes in CM and the uptake of these exosomes by the ER+ MCF-7/ltE2- cells. Differentially expressed microRNAs in CAF CM as well as in MCF-7/ltE2- cells treated with this CM were identified. Knockdown of miR-221/222 in CAFBAS resulted in knockdown of miR221/222 levels in the conditioned media and the CM from CAFBAS; miR221/222 knockdown rescued ER repression in ER-positive cell lines treated with CAFBAS-CM. Collectively, our results demonstrate that CAF-secreted microRNAs are directly involved in ER-repression, and may contribute to the MAPK-induced ER repression in breast cancer cells.

Modelling circulating tumour cells for personalised survival prediction in metastatic breast cancer

Ductal carcinoma is one of the most common cancers among women, and the main cause of death is the formation of metastases. The development of metastases is caused by cancer cells that migrate from the primary tumour site (the mammary duct) through the blood vessels and extravasating they initiate metastasis. Here, we propose a multi-compartment model which mimics the dynamics of tumoural cells in the mammary duct, in the circulatory system and in the bone. Through a branching process model, we describe the relation between the survival times and the four markers mainly involved in metastatic breast cancer (EPCAM, CD47, CD44 and MET). In particular, the model takes into account the gene expression profile of circulating tumour cells to predict personalised survival probability. We also include the administration of drugs as bisphosphonates, which reduce the formation of circulating tumour cells and their survival in the blood vessels, in order to analyse the dynamic changes induced by the therapy. We analyse the effects of circulating tumour cells on the progression of the disease providing a quantitative measure of the cell driver mutations needed for invading the bone tissue. Our model allows to design intervention scenarios that alter the patient-specific survival probability by modifying the populations of circulating tumour cells and it could be extended to other cancer metastasis dynamics.

Loss of the E3 ubiquitin ligase HACE1 results in enhanced Rac1 signaling contributing to breast cancer progression

The transition from ductal carcinoma in situ (DCIS) to invasive breast cancer (IBC) is a crucial step in breast cancer progression. The specific alterations that govern this transition have not been elucidated. HER2/neu is frequently overexpressed in DCIS but is less common in IBC, thereby suggesting additional requirements for transformation. To identify genes capable of cooperating with HER2/neu to fully transform mammary epithelial cells, we used an insertional mutagenesis screen on cells isolated from wild-type neu expressing mice and identified the E3 ligase HACE1 as HER2 cooperative tumor suppressor gene. Loss of HACE1 expression is commonly seen in clinical breast cancer data sets. HACE1 downregulation in normal human mammary epithelial cells (HMECs) results in the accumulation of the activated GTP-bound Rac1 partially transforming these cells. Overexpression of HER2 activates Rac1, which further accumulates upon HACE1 loss resulting in Rac1 hyperactivation. Although the knockdown of HACE1 or overexpression of HER2 alone in HMECs is not sufficient for tumorigenesis, HER2 overexpression combined with HACE1 downregulation fully transforms HMECs resulting in robust tumor formation. The pharmaceutical interference of Rac function abrogates the effects of HACE1 loss both in vitro and in vivo, resulting in marked reduction in tumor burden. Our work supports a critical role for HACE1 in breast cancer progression and identifies patients that may benefit from Rac-targeted therapies.

MSC-regulated microRNAs converge on the transcription factor FOXP2 and promote breast cancer metastasis

Mesenchymal stem/stromal cells (MSCs) are progenitor cells shown to participate in breast tumor stroma formation and to promote metastasis. Despite expanding knowledge of their contributions to breast malignancy, the underlying molecular responses of breast cancer cells (BCCs) to MSC influences remain incompletely understood. Here, we show that MSCs cause aberrant expression of microRNAs, which, led by microRNA-199a, provide BCCs with enhanced cancer stem cell (CSC) properties. We demonstrate that such MSC-deregulated microRNAs constitute a network that converges on and represses the expression of FOXP2, a forkhead transcription factor tightly associated with speech and language development. FOXP2 knockdown in BCCs was sufficient in promoting CSC propagation, tumor initiation, and metastasis. Importantly, elevated microRNA-199a and depressed FOXP2 expression levels are prominent features of malignant clinical breast cancer and are associated significantly with poor survival. Our results identify molecular determinants of cancer progression of potential utility in the prognosis and therapy of breast cancer.

Transcriptional repression of ER through hMAPK dependent histone deacetylation by class I HDACs

Anti-estrogen therapies are not effective in ER- breast cancers, thus identifying mechanisms underlying lack of ER expression in ER- breast cancers is imperative. We have previously demonstrated that hyperactivation of MAPK (hMAPK) downstream of overexpressed EGFR or overexpression/amplification of Her2 represses ER protein and mRNA expression. Abrogation of hMAPK in ER- breast cancer cell lines and primary cultures causes re-expression of ER and restoration of anti-estrogen responses. This study was performed to identify mechanisms of hMAPK-induced transcriptional repression of ER. We found that ER promoter activity is significantly reduced in the presence of hMAPK signaling, yet did not identify specific promoter sequences responsible for this repression. We performed an epigenetic compound screen in an ER- breast cancer cell line that expresses hMAPK yet does not exhibit ER promoter hypermethylation. A number of HDAC inhibitors were identified and confirmed to modulate ER expression and estrogen signaling in multiple ER- cell lines and tumor samples lacking ER promoter methylation. siRNA-mediated knockdown of HDACs 1, 2, and 3 reversed the mRNA repression in multiple breast cancer cell lines and primary cultures and ER promoter-associated histone acetylation increased following MAPK inhibition. These data implicate histone deacetylation downstream of hMAPK in the observed ER mRNA repression associated with hMAPK. Importantly, histone deacetylation appears to be a common mechanism in the transcriptional repression of ER between ER- breast cancers with or without ER promoter hypermethylation.

Plasma membrane proteomics of human breast cancer cell lines identifies potential targets for breast cancer diagnosis and treatment

The use of broad spectrum chemotherapeutic agents to treat breast cancer results in substantial and debilitating side effects, necessitating the development of targeted therapies to limit tumor proliferation and prevent metastasis. In recent years, the list of approved targeted therapies has expanded, and it includes both monoclonal antibodies and small molecule inhibitors that interfere with key proteins involved in the uncontrolled growth and migration of cancer cells. The targeting of plasma membrane proteins has been most successful to date, and this is reflected in the large representation of these proteins as targets of newer therapies. In view of these facts, experiments were designed to investigate the plasma membrane proteome of a variety of human breast cancer cell lines representing hormone-responsive, ErbB2 over-expressing and triple negative cell types, as well as a benign control. Plasma membranes were isolated by using an aqueous two-phase system, and the resulting proteins were subjected to mass spectrometry analysis. Overall, each of the cell lines expressed some unique proteins, and a number of proteins were expressed in multiple cell lines, but in patterns that did not always follow traditional clinical definitions of breast cancer type. From our data, it can be deduced that most cancer cells possess multiple strategies to promote uncontrolled growth, reflected in aberrant expression of tyrosine kinases, cellular adhesion molecules, and structural proteins. Our data set provides a very rich and complex picture of plasma membrane proteins present on breast cancer cells, and the sorting and categorizing of this data provides interesting insights into the biology, classification, and potential treatment of this prevalent and debilitating disease.