Plasticity Of Breast Cancer Cells Research Articles

Cellular geometry and epithelial-mesenchymal plasticity intersect with PIEZO1 in breast cancer cells.

Differences in shape can be a distinguishing feature between different cell types, but the shape of a cell can also be dynamic. Changes in cell shape are critical when cancer cells escape from the primary tumor and undergo major morphological changes that allow them to squeeze between endothelial cells, enter the vasculature, and metastasize to other areas of the body. A shift from rounded to spindly cellular geometry is a consequence of epithelial-mesenchymal plasticity, which is also associated with changes in gene expression, increased invasiveness, and therapeutic resistance. However, the consequences and functional impacts of cell shape changes and the mechanisms through which they occur are still poorly understood. Here, we demonstrate that altering the morphology of a cell produces a remodeling of calcium influx via the ion channel PIEZO1 and identify PIEZO1 as an inducer of features of epithelial-to-mesenchymal plasticity. Combining automated epifluorescence microscopy and a genetically encoded calcium indicator, we demonstrate that activation of the PIEZO1 force channel with the PIEZO1 agonist, YODA 1, induces features of epithelial-to-mesenchymal plasticity in breast cancer cells. These findings suggest that PIEZO1 is a critical point of convergence between shape-induced changes in cellular signaling and epithelial-mesenchymal plasticity in breast cancer cells.

Abstract B022: Targeting epithelial-mesenchymal plasticity and CD73 to enhance responses of breast cancers to immune checkpoint blockade therapies

Abstract Immune checkpoint blockade (ICB) therapy has generated dramatic responses in certain types of human tumors however, the response of breast cancers has been largely limited. Epithelial-mesenchymal plasticity (EMP) enables carcinoma cells to metastasize, gain tumor-initiating ability and mount resistance to chemotherapies. In addition, we have demonstrated that this plasticity program also contributes to the establishment of an immunosuppressive tumor microenvironment and confers resistance to ICB therapy (Dongre and Weinberg 2019). By establishing novel, preclinical models of more-epithelial or more-mesenchymal breast tumors, we observed that epithelial tumors recruit CD8+ T-cells to their microenvironment and are sensitive to anti-CTLA4 ICB. In contrast, mesenchymal tumors recruit Tregs and M2-like macrophages and are resistant to the same treatment (Dongre et al., 2017). Strikingly, abrogation of CD73 from more-mesenchymal cells completely sensitizes otherwise refractory tumors to anti-CTLA4 ICB (Dongre et al., 2021). These findings demonstrated for the first time that more-mesenchymal breast cancer cells can be completely sensitized to anti-tumor immunity by interrupting certain cell-intrinsic signaling channels. However, the underlying mechanisms of such sensitization remain elusive. Additionally, the regulatory networks that control the expression of CD73 itself in more-mesenchymal but not epithelial breast cancer cells are not well defined. To determine the subset of T-cells that is functionally important in sensitizing mesenchymal tumors lacking CD73, we depleted either conventional CD4+ T-cells or CD8+ cytotoxic T-cells in combinatoin with ICB. While responding mice recruited both T-cells to their tumors, only CD4+ T-cells (and not CD8+ T-cells) were functionally important in driving sensitization. Along these lines, more-mesenchymal cancer cells lacking CD73 failed to respond to anti-CTLA4 ICB when propagated in genetically engineered mice lacking CD4+ T-cells relative to wild type controls. Importantly, depletion of CD4+ T-cells also prevented the recruitment of peripheral CD8+ T-cells to responding tumors, thereby driving resistance to ICB. In addition, we observed that human triple negative breast cancer cell lines expressed the highest amount of CD73 relative to hormone receptor-positive cell lines. Most importantly, activating EMP in human breast cancer cells by doxycycline-controlled expression of various transcription factors, induced the expression of CD73. Taken together, our work demonstrates that (i) the phenotypic plasticity of breast cancer cells can predict responses to ICB (ii) targeting CD73 can completely sensitize more-mesenchymal tumors to anti-CTLA4 ICB in a CD4+ T-cell dependent fashion and; (iii) altering the cellular plasticity of cancer cells can regulate CD73 expression. Given the highly refractory nature of more-mesenchymal cancer cells, our findings hold tremendous potential in aiding translational efforts to target cancer plasticity to enhance responses of breast cancers to ICB therapy. Citation Format: Anushka Dongre. Targeting epithelial-mesenchymal plasticity and CD73 to enhance responses of breast cancers to immune checkpoint blockade therapies [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr B022.

Tumor-educated Gr1+CD11b+ cells drive breast cancer metastasis via OSM/IL-6/JAK-induced cancer cell plasticity.

Cancer cell plasticity contributes to therapy resistance and metastasis, which represent the main causes of cancer-related death, including in breast cancer. The tumor microenvironment drives cancer cell plasticity and metastasis, and unraveling the underlying cues may provide novel strategies for managing metastatic disease. Using breast cancer experimental models and transcriptomic analyses, we show that stem cell antigen-1 positive (SCA1+) murine breast cancer cells enriched during tumor progression and metastasis had higher in vitro cancer stem cell-like properties, enhanced in vivo metastatic ability, and generated tumors rich in Gr1hiLy6G+CD11b+ cells. In turn, tumor-educated Gr1+CD11b+ (Tu-Gr1+CD11b+) cells rapidly and transiently converted low metastatic SCA1- cells into highly metastatic SCA1+ cells via secreted oncostatin M (OSM) and IL-6. JAK inhibition prevented OSM/IL-6-induced SCA1+ population enrichment, while OSM/IL-6 depletion suppressed Tu-Gr1+CD11b+-induced SCA1+ population enrichment in vitro and metastasis in vivo. Moreover, chemotherapy-selected highly metastatic 4T1 cells maintained high SCA1+ positivity through autocrine IL-6 production, and in vitro JAK inhibition blunted SCA1 positivity and metastatic capacity. Importantly, Tu-Gr1+CD11b+ cells invoked a gene signature in tumor cells predicting shorter overall survival (OS), relapse-free survival (RFS), and lung metastasis in breast cancer patients. Collectively, our data identified OSM/IL-6/JAK as a clinically relevant paracrine/autocrine axis instigating breast cancer cell plasticity and triggering metastasis.

Abstract 3311: Tumor cell total mRNA level predicts disease progression across multi-ethnic patient cohorts with triple-negative breast cancer

Abstract Tumor heterogeneity presents a major challenge in the clinical management of breast cancers by impacting patient’s prognosis, therapeutic response, and clinical outcomes. Triple-negative breast cancer (TNBC) carries the worst prognosis among all the breast cancer intrinsic subtypes and has limited treatment options. Currently, TNBC subtypes are mainly refined into four categories: basal-like (BL1 and BL2), luminal androgen receptor (LAR) and mesenchymal (M). Although each of these tumor-specific subtypes represent different gene expression profiles, response to standard treatments and prognosis, further studies did not confirm a prognostic value for these subtypes. Given the distinct outcomes of TNBC patients, there is an urgent need to stratify their prognosis and identify patients who may benefit from potential targeted therapy. TNBC tumors often harbor cancer cells with different features in both genomic and transcriptomic level. With deconvolution of existing genomic and transcriptomic data, we derived a mathematical definition of breast cancer cell plasticity at a patient level. With a total of 765 TNBC patients from The Cancer Genome Atlas (TCGA), Molecular Taxonomy of Breast Cancer International Consortium (METABRIC), Fudan University Shanghai Cancer Center (FUSCC) and Sweden Cancerome Analysis Network-Breast project (SCAN-B), we measured tumor-cell total mRNA expression scores (TmS) through an integrative deconvolution method with matched DNAseq and RNAseq data. In our previous study (Cao et al. Nature Biotechnology 2022), high TmS value is significantly associated with favorable prognosis in both TCGA (n=108) and METABRIC (n=214). We now validated this finding in both FUSCC from Han Chinese (n=245) and SCAN-B from Swedes (n=198). With TmS as a patient-level phenotypic feature, we performed differential expression analysis and gene set enrichment analysis to understand the biological functions indicated by TmS. In all four TNBC cohorts, patients with lower TmS are associated with epithelial to mesenchymal and TGFβ signaling hallmark pathways, with the latter presenting potential molecular targets for TNBC. Gene ontology enrichment revealed patients with higher TmS overexpress genes that are related with immune activities such as B cell and lymphocyte activation. Our results suggest a unique utility of tumor-specific total mRNA level in identifying high-risk TNBC patients across multi-ethnic cohorts and tailoring treatment on individual basis to maximize clinical benefit. Citation Format: Yaoyi Dai, Shaolong Cao, Bora Lim, Johan Staaf, Gloria V. Echeverria, Wenyi Wang. Tumor cell total mRNA level predicts disease progression across multi-ethnic patient cohorts with triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3311.

Catulin reporter marks a heterogeneous population of invasive breast cancer cells with some demonstrating plasticity and participating in vascular mimicry

Breast cancer is the most commonly diagnosed cancer in women worldwide. The activation of partial or more complete epithelial–mesenchymal transition in cancer cells enhances acquisition of invasive behaviors and expands their generation of cancer stem cells. Increased by EMT plasticity of tumor cells could promote vascular mimicry, a newly defined pattern of tumor microvascularization by which aggressive tumor cells can form vessel-like structures themselves. VM is strongly associated with a poor prognosis, but biological features of tumor cells that form VM remains unknown. Here we show that catulin is expressed in human BC samples and its expression correlates with the tumor progression. Ablation of catulin in hBC cell lines decreases their invasive potential in the 3D assays. Using a novel catulin promoter based reporter we tracked and characterized the small population of invasive BC cells in xenograft model. RNAseq analysis revealed enrichment in genes important for cellular movement, invasion and interestingly for tumor-vasculature interactions. Analysis of tumors unveiled that catulin reporter marks not only invasive cancer cells but also rare population of plastic, MCAM positive cancer cells that participate in vascular mimicry. Ablation of catulin in the xenograft model revealed deregulation of genes involved in cellular movement, and adhesive properties with striking decrease in CD44 which may impact stemness potential, and plasticity of breast cancer cells. These findings show directly that some plastic tumor cells can change the fate into endothelial-like, expressing MCAM and emphasize the importance of catulin in this process and breast cancer progression.

A reciprocal feedback loop between HIF-1α and HPIP controls phenotypic plasticity in breast cancer cells.

While phenotypic plasticity is a critical factor contributing to tumor heterogeneity, molecular mechanisms underlying this process are largely unknown. Here we report that breast cancer cells display phenotypic diversity in response to hypoxia or normoxia microenvironments by operating a reciprocal positive feedback regulation of HPIP and HIF-1α. We show that under hypoxia, HIF-1α induces HPIP expression that establishes cell survival, and also promotes cell migration/invasion, EMT and metastatic phenotypes in breast cancer cells. Mechanistic studies revealed that HPIP interacts with SRP14, a component of signal recognition particle, and stimulates MMP9 synthesis under hypoxic stress. Whereas, in normoxia, HPIP stabilizes HIF-1α, causing the Warburg effect to support cell growth. Concurrently, mathematical modelling corroborates this reciprocal feedback loop in enabling cell-state transitions in cancer cells. Clinical data indicate that elevated levels of HPIP and HIF-1α correlate with unfavorable prognosis and shorter survival rates in breast cancer subjects. Together, this data shows a reciprocal positive feedback loop between HPIP and HIF-1α that was unknown hitherto. It unveils how the tumor microenvironment influences phenotypic plasticity that has an impact on tumor growth and metastasis and, further signifies considering this pathway as a potential therapeutic target in breast cancer.

Coordinate control of basal epithelial cell fate and stem cell maintenance by core EMT transcription factor Zeb1.

Maintenance of undifferentiated, long-lived, and often quiescent stem cells in the basal compartment is important for homeostasis and regeneration of multiple epithelial tissues, but the molecular mechanisms that coordinately control basal cell fate and stem cell quiescence are elusive. Here, we report an epithelium-intrinsic requirement for Zeb1, a core transcriptional inducer of epithelial-to-mesenchymal transition, for mammary epithelial ductal side branching and for basal cell regenerative capacity. Our findings uncover an evolutionarily conserved role of Zeb1 in promoting basal cell fate over luminal differentiation. We show that Zeb1 loss results in increased basal cell proliferation at the expense of quiescence and self-renewal. Moreover, Zeb1 cooperates with YAP to activate Axin2 expression, and inhibition of Wnt signaling partially restores stem cell function to Zeb1-deficient basal cells. Thus, Zeb1 is a transcriptional regulator that maintains both basal cell fate and stem cell quiescence, and it functions in part through suppressing Wnt signaling.

Mechanisms of metastasis and development of resistance to therapy in breast cancer. A clinical case of the effectiveness of ixabepilone in hormone-receptorpositive breast cancer with multidrug resistance

Metastatic breast cancer occupies a leading position in the structure of mortality among women with oncological diseases worldwide. At the same time, the control of metastatic disease remains a significant problem for clinical oncology despite the improvement of early screening indicators, as well as the introduction of targeted therapy in clinical practice. An increase in the tumor stemness and the epithelial-mesenchymal transition in the primary tumor leads to the plasticity of the tumor cell. This is realized in the progression of the disease, resistance to the therapy and the appearance of distant metastases. Numerous signaling pathways, including PI3K/APK, STAT3, Wnt, Hedgehog, and Notch, play a key role in maintaining cellular plasticity in breast cancer. Understanding the cellular mechanisms of breast cancer cell plasticity with the development of multidrug resistance is a prerequisite for the development of effective therapeutic strategies against metastatic breast cancer in late-line therapy. The article presents an overview of the current understanding of the biological mechanism of the metastatic cascade and resistance to therapy. It is from the point of view of the plasticity of the tumor cell and the increase in the stemness of the tumor that the resistance to treatment is considered. The effectiveness of the representative of Ixabepilone was analyzed in the case of its use in the late-line therapy of hormone-receptor-positive breast cancer with multidrug resistance.

BIO-LGCA: A cellular automaton modelling class for analysing collective cell migration.

Collective dynamics in multicellular systems such as biological organs and tissues plays a key role in biological development, regeneration, and pathological conditions. Collective tissue dynamics—understood as population behaviour arising from the interplay of the constituting discrete cells—can be studied with on- and off-lattice agent-based models. However, classical on-lattice agent-based models, also known as cellular automata, fail to replicate key aspects of collective migration, which is a central instance of collective behaviour in multicellular systems. To overcome drawbacks of classical on-lattice models, we introduce an on-lattice, agent-based modelling class for collective cell migration, which we call biological lattice-gas cellular automaton (BIO-LGCA). The BIO-LGCA is characterised by synchronous time updates, and the explicit consideration of individual cell velocities. While rules in classical cellular automata are typically chosen ad hoc, rules for cell-cell and cell-environment interactions in the BIO-LGCA can also be derived from experimental cell migration data or biophysical laws for individual cell migration. We introduce elementary BIO-LGCA models of fundamental cell interactions, which may be combined in a modular fashion to model complex multicellular phenomena. We exemplify the mathematical mean-field analysis of specific BIO-LGCA models, which allows to explain collective behaviour. The first example predicts the formation of clusters in adhesively interacting cells. The second example is based on a novel BIO-LGCA combining adhesive interactions and alignment. For this model, our analysis clarifies the nature of the recently discovered invasion plasticity of breast cancer cells in heterogeneous environments.

CRIPTO antagonist ALK4L75A-Fc inhibits breast cancer cell plasticity and adaptation to stress

BackgroundCRIPTO is a multi-functional signaling protein that promotes stemness and oncogenesis. We previously developed a CRIPTO antagonist, ALK4L75A-Fc, and showed that it causes loss of the stem cell phenotype in normal mammary epithelia suggesting it may similarly inhibit CRIPTO-dependent plasticity in breast cancer cells.MethodsWe focused on two triple negative breast cancer cell lines (MDA-MB-231 and MDA-MB-468) to measure the effects of ALK4L75A-Fc on cancer cell behavior under nutrient deprivation and endoplasmic reticulum stress. We characterized the proliferation and migration of these cells in vitro using time-lapse microscopy and characterized stress-dependent changes in the levels and distribution of CRIPTO signaling mediators and cancer stem cell markers. We also assessed the effects of ALK4L75A-Fc on proliferation, EMT, and stem cell markers in vivo as well as on tumor growth and metastasis using inducible lentiviral delivery or systemic administration of purified ALK4L75A-Fc, which represents a candidate therapeutic approach.ResultsALK4L75A-Fc inhibited adaptive responses of breast cancer cells under conditions of nutrient and ER stress and reduced their proliferation, migration, clonogenicity, and expression of EMT and cancer stem cell markers. ALK4L75A-Fc also inhibited proliferation of human breast cancer cells in stressed tumor microenvironments in xenografts and reduced both primary tumor size and metastatic burden.ConclusionsCancer cell adaptation to stresses such as nutrient deprivation, hypoxia, and chemotherapy can critically contribute to dormancy, metastasis, therapy resistance, and recurrence. Identifying mechanisms that govern cellular adaptation, plasticity, and the emergence of stem-like cancer cells may be key to effective anticancer therapies. Results presented here indicate that targeting CRIPTO with ALK4L75A-Fc may have potential as such a therapy since it inhibits breast cancer cell adaptation to microenvironmental challenges and associated stem-like and EMT phenotypes.

The Biology of Exosomes in Breast Cancer Progression: Dissemination, Immune Evasion and Metastatic Colonization.

In recent decades, the study of exosome biology has gained growing interest, representing an active area of cancer research with many potential clinical applications. Exosomes are small lipid bilayer particles released by cells with pleiotropic functions that have been reported to regulate the complex intracellular pathway involved in all steps of breast cancer development—from initiation to progression toward a metastatic dissemination. Particularly, the role of these microvesicles has been explored in metastasis, which represents the leading cause of breast cancer morbidity and mortality worldwide. Reports highlight that the plasticity of breast cancer cells, fundamental for the establishment of distant metastasis, may be in part attributed to exosome-carried signals shared between adjacent cells and long-distance cells in the body. In the present review, we will discuss the functions of exosomes in the metastatic breast cancer process and secondary site outgrowth. The possibility to decode the exosome functions in advanced diseases may offer new opportunities for early detection, molecular targeted therapies and exosome-based therapeutics in breast cancer.

Dedifferentiation of MCF-7 Breast Cancer Continuous Cell Line, Development of Breast Cancer Stem Cells (BCSCs) Enriched Culture and Biomarker Analysis

BACKGROUND: Cancer stem cells (CSCs) eradication might serve as a robust approach for cancer eradication. MCF-7 as breast cancer continuous cell line is known to contain breast CSCs (BCSCs) for its capability to maintain its original tumor population. CSCs enriched culture is a fundamental tool for CSCs targeted therapy development. Effective and unsophisticated CSCs dedifferentiation protocol for producing CSCs enriched culture is needed.METHODS: MCF-7 cells were cultured initially in Dulbecco's Modified Eagle Medium (DMEM) low glucose medium then changed to DMEM:F12. Serum starvation was performed during each medium refreshment gradually with fetal bovine serum (FBS) concentration of 10%, 5%, 2.5% until reaching 1% FBS concentration. Stable MCF-7 culture was then adapted to serum free culture system, containing DMEM:F12, epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), and B27 supplement as dedifferentiation protocol for 18 days. Cluster of differentiation (CD)44 and CD24 double staining immunocytochemistry was performed to evaluate cell stemness.RESULTS: The population of cells expressing BCSCs markers (CD44+/CD24low) in non-adherent single cells subpopulation was significantly increased after the dedifferentiation procedure (70.39%) compared to control groups (0.71%) (p<0.05). In contrast, the expression of BCSCs marker in adherent single cells subpopulation and for both adherent and non-adherent mammosphere the BCSCs markers showed a stable expression.CONCLUSION: BCSCs enrichment of breast cancer cell cultures from MCF-7 breast cancer cell line can be performed. Breast cancer cell plasticity is observed during the dedifferentiation protocol. Development of dedifferentiation inducing protocols can serve as an important foundation for breast cancer therapy development through BCSCs elimination.KEYWORDS: breast neoplasms, cell line, dedifferentiation, immunohistochemistry, neoplastic stem cells

Translational control of breast cancer plasticity

Plasticity of neoplasia, whereby cancer cells attain stem-cell-like properties, is required for disease progression and represents a major therapeutic challenge. We report that in breast cancer cells NANOG, SNAIL and NODAL transcripts manifest multiple isoforms characterized by different 5’ Untranslated Regions (5’UTRs), whereby translation of a subset of these isoforms is stimulated under hypoxia. The accumulation of the corresponding proteins induces plasticity and “fate-switching” toward stem cell-like phenotypes. Mechanistically, we observe that mTOR inhibitors and chemotherapeutics induce translational activation of a subset of NANOG, SNAIL and NODAL mRNA isoforms akin to hypoxia, engendering stem-cell-like phenotypes. These effects are overcome with drugs that antagonize translational reprogramming caused by eIF2α phosphorylation (e.g. ISRIB), suggesting that the Integrated Stress Response drives breast cancer plasticity. Collectively, our findings reveal a mechanism of induction of plasticity of breast cancer cells and provide a molecular basis for therapeutic strategies aimed at overcoming drug resistance and abrogating metastasis.

Cellular Plasticity in Breast Cancer Progression and Therapy.

With the exception of non-melanoma skin cancer, breast cancer is the most frequently diagnosed malignant disease among women, with the majority of mortality being attributable to metastatic disease. Thus, even with improved early screening and more targeted treatments which may enable better detection and control of early disease progression, metastatic disease remains a significant problem. While targeted therapies exist for breast cancer patients with particular subtypes of the disease (Her2+ and ER/PR+), even in these subtypes the therapies are often not efficacious once the patient's tumor metastasizes. Increases in stemness or epithelial-to-mesenchymal transition (EMT) in primary breast cancer cells lead to enhanced plasticity, enabling tumor progression, therapeutic resistance, and distant metastatic spread. Numerous signaling pathways, including MAPK, PI3K, STAT3, Wnt, Hedgehog, and Notch, amongst others, play a critical role in maintaining cell plasticity in breast cancer. Understanding the cellular and molecular mechanisms that regulate breast cancer cell plasticity is essential for understanding the biology of breast cancer progression and for developing novel and more effective therapeutic strategies for targeting metastatic disease. In this review we summarize relevant literature on mechanisms associated with breast cancer plasticity, tumor progression, and drug resistance.

Abstract PD8-09: Genome-scale systems biology analyses reveal potentially targetable signaling networks in breast cancer brain metastases

Abstract Background: Roughly 10-30% of metastatic breast cancer patients will develop brain metastases (BM) over the course of their disease. The prognosis for breast cancer patients with BM remains poor due to the deficiency of effective targeted therapies in this setting. A comprehensive characterization of deregulated signaling networks in breast cancer brain metastases would enable the delineation of pathways mediating metastases to the brain thus improving treatment options for this deadly disease. Using our novel systems biology paradigm (InFlo) that robustly infers deregulated signaling networks in individual tumor samples (Oncogene, 2017), we report genome-scale characterization of signaling network deregulations in breast cancer BM and matched primary tumor samples. Methods: Pathology records were searched for patients who underwent surgical resection of breast cancer BM and primary breast tumors (PB). Archival FFPE material and clinical data was obtained for a total of 76 breast cancer patients. Tumor DNA/RNA was extracted from 2 mm macrodissected FFPE cores followed by transcriptome profiling using Affymetrix HTA 2.0 arrays. Transcriptome profiles for a total of 133 FFPE samples included 72 BM and 31 PB, counting 31 BM/PB pairs from the same patient. PAM50 subtypes were derived for BM and PB samples, and InFlo was employed to interrogate genome scale signaling network deregulations in BM and PB as compared to normal breast controls. InFlo-derived signaling deregulations in the 72 BM were contrasted against the 31 PB using a Wilcoxon rank-sum test, followed by paired analyses in the matched 31 BM/PB pairs using the Wilcoxon signed-rank test. The immune microenvironment of BM/PB was assessed using model-based deconvolution of transcriptomic profiles, along with independent assessment of tumor infiltrating lymphocytes (TILs) in accordance with the International TILs Working Group standards. Results: We identified subtype switching between BM and matched PB in 5/31 pairs (16.1%) and loss of ER in 6/31 pairs (19.4%). Changes in receptor status were not associated with concurrent BM and only occurred in patients with two or more years between excision of the primary tumor and diagnosis/resection of BM. Consistent with prior studies, BM exhibited significantly lower TILs as compared to PB (P = 0.001) by both pathologist assessment and transcriptomic deconvolution. InFlo-based analyses revealed recurrent and subtype-independent hyperactivation of signaling networks in BM as compared to PB, including RhoA (62.5% of BM; P = 0.023) and anti-apoptotic BCL signaling (69.4% of BM; P = 0.003). In contrast, PPARα signaling was activated in 15.3% of BM (P = 0.003) and FGFR2 signaling was activated in 11.1% of BM (P = 0.005), with the Basal-like subtype exhibiting the highest rates of activation of these networks (PPARα, 21.7%; FGFR2, 17.4%). Activated HER3 signaling was observed in 13.9% of BM (P = 0.023) with the highest activation rates (28.6%) occurring within the Luminal A subtype. Conclusions: This first of its kind systems biology interrogation of genome-scale signaling network deregulations in BM in breast cancer reveals highly recurrent and subtype-specific pathway activations. The highly recurrent activation of pro-survival BCL-signaling specific to BM has high translational significance given recent positive developments of BH3 mimetics in the clinic. Furthermore, our observance of substantial differences in signaling network activities in brain metastases as compared to matched primary tumors points to the plasticity of breast cancer cells as they adapt to their metastatic niche. Overall, our study underscores the need to decode the molecular dependencies of metastatic lesions in order to develop effective therapeutic interventions targeting breast cancer metastases to the brain. Citation Format: Hannah Elizabeth Hill, Salendra Singh, Kristy Miskimen, Paula Silverman, Jill Barnholtz-Sloan, Andrew Sloan, Hannah Gilmore, Vinay Varadan. Genome-scale systems biology analyses reveal potentially targetable signaling networks in breast cancer brain metastases [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr PD8-09.

The Exosome And Breast Cancer Cell Plasticity.

Cancer cell plasticity is the ability of cancer cells to reversibly interchange between distinct cell status, which plays a key role in cancer progression. Cancer cell plasticity is now known to be shaped by the secreted nanoparticles termed exosomes which transport proteins and lipids as well as nucleic acids. These aspects have emerged as key determinants of tumor progression and targeting, with approaches such as immunotherapy showing promise in the clinic. While significant strides have been made in this research area, some very interesting questions still warrant more and deeper investigation. We provide a review of the interplay between exosomes and breast cancer cell plasticity, and the potential implication in metastases and drug-resistance.

Mitochondrial Flexibility of Breast Cancers: A Growth Advantage and a Therapeutic Opportunity.

Breast cancers are very heterogeneous tissues with several cell types and metabolic pathways together sustaining the initiation and progression of disease and contributing to evasion from cancer therapies. Furthermore, breast cancer cells have an impressive metabolic plasticity that is regulated by the heterogeneous tumour microenvironment through bidirectional interactions. The structure and accessibility of nutrients within this unstable microenvironment influence the metabolism of cancer cells that shift between glycolysis and mitochondrial oxidative phosphorylation (OXPHOS) to produce adenosine triphosphate (ATP). In this scenario, the mitochondrial energetic pathways of cancer cells can be reprogrammed to modulate breast cancer’s progression and aggressiveness. Moreover, mitochondrial alterations can lead to crosstalk between the mitochondria and the nucleus, and subsequently affect cancer tissue properties. This article reviewed the metabolic plasticity of breast cancer cells, focussing mainly on breast cancer mitochondrial metabolic reprogramming and the mitochondrial alterations influencing nuclear pathways. Finally, the therapeutic strategies targeting molecules and pathways regulating cancer mitochondrial alterations are highlighted.

CXADR-Mediated Formation of an AKT Inhibitory Signalosome at Tight Junctions Controls Epithelial-Mesenchymal Plasticity in Breast Cancer.

Tight junctions (TJ) act as hubs for intracellular signaling pathways controlling epithelial cell fate and function. Deregulation of TJ is a hallmark of epithelial-mesenchymal transition (EMT), which contributes to carcinoma progression and metastasis. However, the signaling mechanisms linking TJ to the induction of EMT are not understood. Here, we identify a TJ-based signalosome, which controls AKT signaling and EMT in breast cancer. The coxsackie and adenovirus receptor (CXADR), a TJ protein with an essential yet uncharacterized role in organogenesis and tissue homeostasis, was identified as a key component of the signalosome. CXADR regulated the stability and function of the phosphatases and AKT inhibitors PTEN and PHLPP2. Loss of CXADR led to hyperactivation of AKT and sensitized cells to TGFβ1-induced EMT. Conversely, restoration of CXADR stabilized PHLPP2 and PTEN, inhibited AKT, and promoted epithelial differentiation. Loss of CXADR in luminal A breast cancer correlated with loss of PHLPP2 and PTEN and poor prognosis. These results show that CXADR promotes the formation of an AKT-inhibitory signalosome at TJ and regulates epithelial-mesenchymal plasticity in breast cancer cells. Moreover, loss of CXADR might be used as a prognostic marker in luminal breast cancer. SIGNIFICANCE: The tight junction protein CXADR controls epithelial-mesenchymal plasticity in breast cancer by stabilizing the AKT regulators PTEN and PHLPP2.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/1/47/F1.large.jpg.

Abstract 4915: Alcohol-induced reprogramming of tumor plasticity is mediated via suppression of CCN5 signaling in breast cancer cells

Abstract Background and Objective: The epidemiological and experimental studies suggest that alcohol consumption is associated with increased risk for breast cancer development and metastasis. However, the mechanisms of alcohol-induced breast cancer progression and metastasis remain unknown. In this study, we examined the roles of CCN5, a tumor suppressor gene in alcohol induced breast cancer cell migration/invasion, epithelial to mesenchymal transition (EMT) and stemness. Methods: Estrogen receptor-positive (ER+) human breast cancer cell line MCF-7 and immortalized normal human epithelial breast cell line MCF-12A were treated with ethanol at various concentrations in the presence and absence of human recombinant human CCN5 protein (hrCCN5) . Invasive/migratory ability of treated and untreated cells was measured by Boyden chamber assays. The mRNA and protein expression level of CCN5 was determined by real-time qRT-PCR and Western blot. EMT and stemness markers were evaluated by Western blot. Single-cell suspensions from pre-treated cells were re-suspended at a density of 500 cells/ml mammocult media in ultralow attachment dishes. Number as well as the size of the mammosphere in specified experimental set-up was monitored and recorded alternate day for 8-10 days. Results: The studies demonstrated that alcohol promotes significantly the invasive/migratory ability and EMT phenotypes of breast cancer cells through the suppression of CCN5. Interestingly, hrCCN5 protein treatment suppresses the effect of alcohol and reprograms MET (mesenchymal to epithelial transition). In addition, alcohol-induced mammosphere formation efficiency is also suppressed by hrCCN5 protein-treatment. Conclusions: Our findings suggest that the CCN5 signaling plays a preventive role in alcohol-induced reprogramming of tumor plasticity in breast cancer cells. Citation Format: Inamul Haque, Arvind Subramanian, Vijayalaxmi Gupta, Sandipto Sarkar, Snigdha Banerjee, Sushanta K. Banerjee. Alcohol-induced reprogramming of tumor plasticity is mediated via suppression of CCN5 signaling in breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4915. doi:10.1158/1538-7445.AM2017-4915

The lncRNA H19 mediates breast cancer cell plasticity during EMT and MET plasticity by differentially sponging miR-200b/c and let-7b.

Metastasis is a multistep process by which tumor cells disseminate from their primary site and form secondary tumors at a distant site. The pathophysiological course of metastasis is mediated by the dynamic plasticity of cancer cells, which enables them to shift between epithelial and mesenchymal phenotypes through a transcriptionally regulated program termed epithelial-to-mesenchymal transition (EMT) and its reverse process, mesenchymal-to-epithelial transition (MET). Using a mouse model of spontaneous metastatic breast cancer, we investigated the molecular mediators of metastatic competence within a heterogeneous primary tumor and how these cells then manipulated their epithelial-mesenchymal plasticity during the metastatic process. We isolated cells from the primary mammary tumor, the circulation, and metastatic lesions in the lung in TA2 mice and found that the long noncoding RNA (lncRNA) H19 mediated EMT and MET by differentially acting as a sponge for the microRNAs miR-200b/c and let-7b. We found that this ability enabled H19 to modulate the expression of the microRNA targets Git2 and Cyth3, respectively, which encode regulators of the RAS superfamily member adenosine 5'-diphosphate (ADP) ribosylation factor (ARF), a guanosine triphosphatase (GTPase) that promotes cell migration associated with EMT and disseminating tumor cells. Decreasing the abundance of H19 or manipulating that of members in its axis prevented metastasis from grafts in syngeneic mice. Abundance of H19, GIT2, and CYTH3 in patient samples further suggests that H19 might be exploited as a biomarker for metastatic cells within breast tumors and perhaps as a therapeutic target to prevent metastasis.