Ethnicity-Dependent and -Independent Heterogeneity in Healthy Normal Breast Hierarchy Impacts Tumor Characterization

Clinicopathological features associated with CD44 and CD63 expression in breast cancer

Background

CD44 is a cell-surface transmembrane glycoprotein that participates in the regulation of many cellular processes, including cell division, adhesion, migration and stem-like characteristics. CD63 is involved in the exocytosis process.

Objective

To evaluate the relationship between CD44 and CD63 expression and clinicopathological features, including tumor-infiltrating lymphocytes (TILs), phosphoinositide 3-kinase (PIK3CA) mutation and survival.

Methodology

CD44 and CD63 were stained in samples from 101 breast cancer cases from Peruvian women.

Results

Median age was 52 years, most were most were grade-3 (68%), estrogen receptor (ER)+ (64%) and stage II-III (92%). Median ki67 was 30%, median stromal TIL was 30% and PIK3CA mutation was found in 49%. Longer survival was associated with earlier stages (p = 0.016), lower ki67 (p = 0.023), ER+ (p = 0.034), luminal phenotype (p = 0.029) and recurrence (p < 0.001). CD44 was classified as high cell density staining in 57% and high intensity in 55%. High CD44 density was associated with younger age (p = 0.043), triple-negative phenotype (p = 0.035) and shorter survival (p = 0.005). High CD44 expression was associated with short survival (p = 0.005). High CD63 cell density was found in 56% of cases and was associated with ER-positive (p = 0.045), low TIL levels (p = 0.007), Luminal-A (p = 0.015) and low CD44 intensity (p = 0.032).

Conclusion

CD44 expression was associated with aggressive features and low CD63 density staining.

Organoid Cultures for the Study of Mammary Biology and Breast Cancer: The Promise and Challenges

During the last decade, biomedical research has experienced a resurgence in the use of three-dimensional culture models for studies of normal and cancer biology. This resurgence has been driven by the development of models in which primary cells are grown in tissue-mimicking media and extracellular matrices to create organoid or organotypic cultures that more faithfully replicate the complex architecture and physiology of normal tissues and tumors. In addition, patient-derived tumor organoids preserve the three-dimensional organization and characteristics of the patient tumors ex vivo, becoming excellent preclinical models to supplement studies of tumor xenografts transplanted into immunocompromised mice. In this perspective, we provide an overview of how organoids are being used to investigate normal mammary biology and as preclinical models of breast cancer and discuss improvements that would enhance their utility and relevance to the field.

Unlocking Translational Potential: Conditionally Reprogrammed Cells in Advancing Breast Cancer Research

Preclinical in vitro models play an important role in studying cancer cell biology and facilitating translational research, especially in the identification of drug targets and drug discovery studies. This is particularly relevant in breast cancer, where the global burden of disease is quite high based on prevalence and a relatively high rate of lethality. Predictive tools to select patients who will be responsive to invasive or morbid therapies (radiotherapy, chemotherapy, immunotherapy, and/or surgery) are relatively lacking. To be clinically relevant, a model must accurately replicate the biology and cellular heterogeneity of the primary tumor. Addressing these requirements and overcoming the limitations of most existing cancer cell lines, which are typically derived from a single clone, we have recently developed conditional reprogramming (CR) technology. The CR technology refers to a co-culture system of primary human normal or tumor cells with irradiated murine fibroblasts in the presence of a Rho-associated kinase inhibitor to allow the primary cells to acquire stem cell properties and the ability to proliferate indefinitely in vitro without any exogenous gene or viral transfection. This innovative approach fulfills many of these needs and offers an alternative that surpasses the deficiencies associated with traditional cancer cell lines. These CR cells (CRCs) can be reprogrammed to maintain a highly proliferative state and reproduce the genomic and histological characteristics of the parental tissue. Therefore, CR technology may be a clinically relevant model to test and predict drug sensitivity, conduct gene profile analysis and xenograft research, and undertake personalized medicine. This review discusses studies that have applied CR technology to conduct breast cancer research.

Stromal heterogeneity may explain increased incidence of metaplastic breast cancer in women of African descent

The biologic basis of genetic ancestry-dependent variability in disease incidence and outcome is just beginning to be explored. We recently reported enrichment of a population of ZEB1-expressing cells located adjacent to ductal epithelial cells in normal breasts of women of African ancestry compared to those of European ancestry. In this study, we demonstrate that these cells have properties of fibroadipogenic/mesenchymal stromal cells that express PROCR and PDGFRα and transdifferentiate into adipogenic and osteogenic lineages. PROCR + /ZEB1 + /PDGFRα+ (PZP) cells are enriched in normal breast tissues of women of African compared to European ancestry. PZP: epithelial cell communication results in luminal epithelial cells acquiring basal cell characteristics and IL-6-dependent increase in STAT3 phosphorylation. Furthermore, level of phospho-STAT3 is higher in normal and cancerous breast tissues of women of African ancestry. PZP cells transformed with HRasG12V ± SV40-T/t antigens generate metaplastic carcinoma suggesting that these cells are one of the cells-of-origin of metaplastic breast cancers.

A human skeletal muscle stem/myotube model reveals multiple signaling targets of cancer secretome in skeletal muscle

Skeletal muscle dysfunction or reprogramming due to the effects of the cancer secretome is observed in multiple malignancies. Although mouse models are routinely used to study skeletal muscle defects in cancer, because of species specificity of certain cytokines/chemokines in the secretome, a human model system is required. Here, we establish simplified multiple skeletal muscle stem cell lines (hMuSCs), which can be differentiated into myotubes. Using single nuclei ATAC-seq (snATAC-seq) and RNA-seq (snRNA-seq), we document chromatin accessibility and transcriptomic changes associated with the transition of hMuSCs to myotubes. Cancer secretome accelerated stem to myotube differentiation, altered the alternative splicing machinery and increased inflammatory, glucocorticoid receptor, and wound healing pathways in hMuSCs. Additionally, cancer secretome reduced metabolic and survival pathway associated miR-486, AKT, and p53 signaling in hMuSCs. hMuSCs underwent myotube differentiation when engrafted into NSG mice and thus providing a humanized in vivo skeletal muscle model system to study cancer cachexia.

TONSL Is an Immortalizing Oncogene and a Therapeutic Target in Breast Cancer

Study of genomic aberrations leading to immortalization of epithelial cells has been technically challenging due to the lack of isogenic models. To address this, we used healthy primary breast luminal epithelial cells of different genetic ancestry and their hTERT-immortalized counterparts to identify transcriptomic changes associated with immortalization. Elevated expression of TONSL (Tonsoku-like, DNA repair protein) was identified as one of the earliest events during immortalization. TONSL, which is located on chromosome 8q24.3, was found to be amplified in approximately 20% of breast cancers. TONSL alone immortalized primary breast epithelial cells and increased telomerase activity, but overexpression was insufficient for neoplastic transformation. However, TONSL-immortalized primary cells overexpressing defined oncogenes generated estrogen receptor-positive adenocarcinomas in mice. Analysis of a breast tumor microarray with approximately 600 tumors revealed poor overall and progression-free survival of patients with TONSL-overexpressing tumors. TONSL increased chromatin accessibility to pro-oncogenic transcription factors, including NF-κB and limited access to the tumor-suppressor p53. TONSL overexpression resulted in significant changes in the expression of genes associated with DNA repair hubs, including upregulation of several genes in the homologous recombination (HR) and Fanconi anemia pathways. Consistent with these results, TONSL-overexpressing primary cells exhibited upregulated DNA repair via HR. Moreover, TONSL was essential for growth of TONSL-amplified breast cancer cell lines in vivo, and these cells were sensitive to TONSL-FACT complex inhibitor CBL0137. Together, these findings identify TONSL as a regulator of epithelial cell immortalization to facilitate cancer initiation and as a target for breast cancer therapy.

SIGNIFICANCE

The chr.8q24.3 amplicon-resident gene TONSL is upregulated during the initial steps of tumorigenesis to support neoplastic transformation by increasing DNA repair and represents a potential therapeutic target for treating breast cancer.

Mapping hormone-regulated cell-cell interaction networks in the human breast at single-cell resolution

The rise and fall of estrogen and progesterone across menstrual cycles and during pregnancy regulates breast development and modifies cancer risk. How these hormones impact each cell type in the breast remains poorly understood because they act indirectly through paracrine networks. Using single-cell analysis of premenopausal breast tissue, we reveal a network of coordinated transcriptional programs representing the tissue-level response to changing hormone levels. Our computational approach, DECIPHER-seq, leverages person-to-person variability in breast composition and cell state to uncover programs that co-vary across individuals. We use differences in cell-type proportions to infer a subset of programs that arise from direct cell-cell interactions regulated by hormones. Further, we demonstrate that prior pregnancy and obesity modify hormone responsiveness through distinct mechanisms: obesity reduces the proportion of hormone-responsive cells, whereas pregnancy dampens the direct response of these cells to hormones. Together, these results provide a comprehensive map of the cycling human breast.

Acquisition, processing, and single-cell analysis of normal human breast tissues from a biobank

The Komen Tissue Bank is the only biorepository in the world for normal breast tissues from women. Below we report the acquisition and processing of breast tissue from volunteer donors and describe an experimental and analysis pipeline to generate a single-cell atlas. This atlas is based on single-cell RNA-seq and is useful to derive breast epithelial cell subcluster-specific gene expression signatures, which can be applied to breast cancer gene expression data to identify putative cell-of-origin.

For complete details on the use and execution of this protocol, please refer to Bhat-Nakshatri et al. (2021).

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Breast core biopsies from healthy donors are suitable for single-cell RNA-seq

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Cryopreserved biopsies are as good as fresh biopsies for the analysis

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Biopsies from five donors can be combined to yield required cell number

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Multiple cell types including epithelial, endothelial, and pericytes can be mapped

Bidirectional Regulatory Cross-Talk between Cell Context and Genomic Aberrations Shapes Breast Tumorigenesis

Breast cancers are classified into five intrinsic subtypes and 10 integrative clusters based on gene expression patterns and genomic aberrations, respectively. Although the cell-of-origin, adaptive plasticity, and genomic aberrations shape dynamic transcriptomic landscape during cancer progression, how interplay between these three core elements governs obligatory steps for a productive cancer progression is unknown. Here, we used genetic ancestry-mapped immortalized breast epithelial cell lines generated from breast biopsies of healthy women that share gene expression profiles of luminal A, normal-like, and basal-like intrinsic subtypes of breast cancers and breast cancer relevant oncogenes to develop breast cancer progression model. Using flow cytometry, mammosphere growth, signaling pathway, DNA damage response, and in vivo tumorigenicity assays, we provide evidence that establishes cell context-dependent effects of oncogenes in conferring plasticity, self-renewal/differentiation, intratumor heterogeneity, and metastatic properties. In contrast, oncogenic aberrations, independent of cell context, shaped response to DNA damage-inducing agents. Collectively, this study reveals how the same set of genomic aberration can have distinct effects on tumor characteristics based on cell-of-origin of tumor and highlights the need to utilize multiple "normal" epithelial cell types to decipher oncogenic properties of a gene of interest. In addition, by creating multiple isogenic cell lines ranging from primary cells to metastatic variants, we provide resources to elucidate cell-intrinsic properties and cell-oncogene interactions at various stages of cancer progression. IMPLICATIONS: Our findings demonstrate that how an interplay between the normal cell type that encountered genomic aberrations and type of genomic aberration influences heterogeneity, self-renewal/differentiation, and tumor properties including propensity for metastasis.

High-throughput surface marker screen on primary human breast tissues reveals further cellular heterogeneity

BACKGROUND

Normal human breast tissues are a heterogeneous mix of epithelial and stromal subtypes in different cell states. Delineating the spectrum of cellular heterogeneity will provide new insights into normal cellular properties within the breast tissue that might become dysregulated in the initial stages of cancer. Investigation of surface marker expression provides a valuable approach to resolve complex cell populations. However, the majority of cell surface maker expression of primary breast cells have not been investigated.

METHODS

To determine the differences in expression of a range of uninvestigated cell surface markers between the normal breast cell subpopulations, primary human breast cells were analysed using high-throughput flow cytometry for the expression of 242 cell surface proteins in conjunction with EpCAM/CD49f staining.

RESULTS

We identified 35 surface marker proteins expressed on normal breast epithelial and/or stromal subpopulations that were previously unreported. We also show multiple markers were equally expressed in all cell populations (e.g. CD9, CD59, CD164) while other surface markers were confirmed to be enriched in different cell lineages: CD24, CD227 and CD340 in the luminal compartment, CD10 and CD90 in the basal population, and CD34 and CD140b on stromal cells.

CONCLUSIONS

Our dataset of CD marker expression in the normal breast provides better definition for breast cellular heterogeneity.

A single-cell atlas of the healthy breast tissues reveals clinically relevant clusters of breast epithelial cells

Single-cell RNA sequencing (scRNA-seq) is an evolving technology used to elucidate the cellular architecture of adult organs. Previous scRNA-seq on breast tissue utilized reduction mammoplasty samples, which are often histologically abnormal. We report a rapid tissue collection/processing protocol to perform scRNA-seq of breast biopsies of healthy women and identify 23 breast epithelial cell clusters. Putative cell-of-origin signatures derived from these clusters are applied to analyze transcriptomes of ~3,000 breast cancers. Gene signatures derived from mature luminal cell clusters are enriched in ~68% of breast cancers, whereas a signature from a luminal progenitor cluster is enriched in ~20% of breast cancers. Overexpression of luminal progenitor cluster-derived signatures in HER2+, but not in other subtypes, is associated with unfavorable outcome. We identify TBX3 and PDK4 as genes co-expressed with estrogen receptor (ER) in the normal breasts, and their expression analyses in >550 breast cancers enable prognostically relevant subclassification of ER+ breast cancers.

Ancestry-associated transcriptomic profiles of breast cancer in patients of African, Arab, and European ancestry

Breast cancer largely dominates the global cancer burden statistics; however, there are striking disparities in mortality rates across countries. While socioeconomic factors contribute to population-based differences in mortality, they do not fully explain disparity among women of African ancestry (AA) and Arab ancestry (ArA) compared to women of European ancestry (EA). In this study, we sought to identify molecular differences that could provide insight into the biology of ancestry-associated disparities in clinical outcomes. We applied a unique approach that combines the use of curated survival data from The Cancer Genome Atlas (TCGA) Pan-Cancer clinical data resource, improved single-nucleotide polymorphism-based inferred ancestry assignment, and a novel breast cancer subtype classification to interrogate the TCGA and a local Arab breast cancer dataset. We observed an enrichment of BasalMyo tumors in AA patients (38 vs 16.5% in EA, p = 1.30E - 10), associated with a significant worse overall (hazard ratio (HR) = 2.39, p = 0.02) and disease-specific survival (HR = 2.57, p = 0.03). Gene set enrichment analysis of BasalMyo AA and EA samples revealed differences in the abundance of T-regulatory and T-helper type 2 cells, and enrichment of cancer-related pathways with prognostic implications (AA: PI3K-Akt-mTOR and ErbB signaling; EA: EGF, estrogen-dependent and DNA repair signaling). Strikingly, AMPK signaling was associated with opposing prognostic connotation (AA: 10-year HR = 2.79, EA: 10-year HR = 0.34). Analysis of ArA patients suggests enrichment of BasalMyo tumors with a trend for differential enrichment of T-regulatory cells and AMPK signaling. Together, our findings suggest that the disparity in the clinical outcome of AA breast cancer patients is likely related to differences in cancer-related and microenvironmental features.

Combination of circulating miR-145-5p/miR-191-5p as biomarker for breast cancer detection

Background

Breast cancer (BC) is the most common cancer among women worldwide. At present, there is a need to search for new, accurate, reliable, minimally invasive and cheap biomarkers in addition to existing methods for the diagnosis and prognosis of BC. The main goal of this study was to test the diagnostic value of six circulating miRNAs in Kazakh women.

Materials and methods

TaqMan-based miRNA profiling was conducted using plasma specimens from 35 BC women patients and 33 healthy women samples (control group).

Results

The level of all seven miRNAs (including endogenous control) normalized by synthetic cel-miR-39 were significantly elevated in the group of BC patients. Normalization using miR-222-3p as endogenous control reduced differences in level of miRNAs between groups; as a result, only three miRNAs were significantly upregulated in the group of BC patients—miR-145-5p (P = 6.5e−12), miR-191-5p (P = 3.7e−10) and miR-21-5p (P = 0.0034). Moreover, ROC analysis showed that the use of miR-145-5p and miR-191-5p, both individually (AUC = 0.931 and 0.904, respectively) or in combination (AUC = 0.984), allows to accurately differentiate BC patients from healthy individuals.

Conclusions

Two plasma miRNAs—miR-145-5p and miR-191-5p—are potential biomarkers for diagnosis of BC in the Kazakh population. The findings need to be further substantiated using a more representative sample.

Cancer stem cells: Culprits in endocrine resistance and racial disparities in breast cancer outcomes

Breast cancer stem cells (BCSCs) promote endocrine therapy (ET) resistance, also known as endocrine resistance in hormone receptor (HR) positive breast cancer. Endocrine resistance occurs via mechanisms that are not yet fully understood. In vitro, in vivo and clinical data suggest that signaling cascades such as Notch, hypoxia inducible factor (HIF), and integrin/Akt promote BCSC-mediated endocrine resistance. Once HR positive breast cancer patients relapse on ET, targeted therapy agents such as cyclin dependent kinase inhibitors are frequently implemented, though secondary resistance remains a threat. Here, we discuss Notch, HIF, and integrin/Akt pathway regulation of BCSC activity and potential strategies to target these pathways to counteract endocrine resistance. We also discuss a plausible link between elevated BCSC-regulatory gene levels and reduced survival observed among African American women with basal-like breast cancer which lacks HR expression. Should future studies reveal a similar link for patients with luminal breast cancer, then the use of agents that impede BCSC activity could prove highly effective in improving clinical outcomes among African American breast cancer patients.

Breast Cancer Cell Detection and Characterization from Breast Milk-Derived Cells

Radiologic techniques remain the main method for early detection for breast cancer and are critical to achieve a favorable outcome from cancer. However, more sensitive detection methods to complement radiologic techniques are needed to enhance early detection and treatment strategies. Using our recently established culturing method that allows propagation of normal and cancerous breast epithelial cells of luminal origin, flow cytometry characterization, and genomic sequencing, we show that cancer cells can be detected in breast milk. Cells derived from milk from the breast with cancer were enriched for CD49f⁺/EpCAM^-, CD44⁺/CD24^-, and CD271⁺ cancer stem-like cells (CSC). These CSCs carried mutations within the cytoplasmic retention domain of HDAC6, stop/gain insertion in MORF4L1, and deletion mutations within SWI/SNF complex component SMARCC2. CSCs were sensitive to HDAC6 inhibitors, BET bromodomain inhibitors, and EZH2 inhibitors, as mutations in SWI/SNF complex components are known to increase sensitivity to these drugs. Among cells derived from breast milk of additional ten women not known to have breast cancer, two of them contained cells that were enriched for the CSC phenotype and carried mutations in NF1 or KMT2D, which are frequently mutated in breast cancer. Breast milk-derived cells with NF1 mutations also carried copy-number variations in CDKN2C, PTEN, and REL genes. The approach described here may enable rapid cancer cell characterization including driver mutation detection and therapeutic screening for pregnancy/postpartum breast cancers. Furthermore, this method can be developed as a surveillance or early detection tool for women at high risk for developing breast cancer. SIGNIFICANCE: These findings describe how a simple method for characterization of cancer cells in pregnancy and postpartum breast cancer can be exploited as a surveillance tool for women at risk of developing breast cancer.

Hybrid Stem Cell States: Insights Into the Relationship Between Mammary Development and Breast Cancer Using Single-Cell Transcriptomics

Similarities between stem cells and cancer cells have implicated mammary stem cells in breast carcinogenesis. Recent evidence suggests that normal breast stem cells exist in multiple phenotypic states: epithelial, mesenchymal, and hybrid epithelial/mesenchymal (E/M). Hybrid E/M cells in particular have been implicated in breast cancer metastasis and poor prognosis. Mounting evidence also suggests that stem cell phenotypes change throughout the life course, for example, through embryonic development and pregnancy. The goal of this study was to use single cell RNA-sequencing to quantify cell state distributions of the normal mammary (NM) gland throughout developmental stages and when perturbed into a stem-like state in vitro using conditional reprogramming (CR). Using machine learning based dataset alignment, we integrate multiple mammary gland single cell RNA-seq datasets from human and mouse, along with bulk RNA-seq data from breast tumors in the Cancer Genome Atlas (TCGA), to interrogate hybrid stem cell states in the normal mammary gland and cancer. CR of human mammary cells induces an expanded stem cell state, characterized by increased expression of embryonic stem cell associated genes. Alignment to a mouse single-cell transcriptome atlas spanning mammary gland development from in utero to adulthood revealed that NM cells align to adult mouse cells and CR cells align across the pseudotime trajectory with a stem-like population aligning to the embryonic mouse cells. Three hybrid populations emerge after CR that are rare in NM: KRT18+/KRT14+ (hybrid luminal/basal), EPCAM+/VIM+ (hybrid E/M), and a quadruple positive population, expressing all four markers. Pseudotime analysis and alignment to the mouse developmental trajectory revealed that E/M hybrids are the most developmentally immature. Analyses of single cell mouse mammary RNA-seq throughout pregnancy show that during gestation, there is an enrichment of hybrid E/M cells, suggesting that these cells play an important role in mammary morphogenesis during lactation. Finally, pseudotime analysis and alignment of TCGA breast cancer expression data revealed that breast cancer subtypes express distinct developmental signatures, with basal tumors representing the most “developmentally immature” phenotype. These results highlight phenotypic plasticity of normal mammary stem cells and provide insight into the relationship between hybrid cell populations, stemness, and cancer.

Breast Heterogeneity: Obstacles to Developing Universal Biomarkers of Breast Cancer Initiation and Progression

BACKGROUND

Predicting outcomes and response to therapy through biomarkers is a major challenge in cancer research. In previous studies, we suggested that inappropriate "normal" tissue samples used for comparison with tumors, inter-individual heterogeneity in gene expression, and genetic ancestry all influence biomarker expression in tumors. The aim of this study was to investigate these factors in breast cancer using breast tissues from healthy women and normal tissue adjacent to tumor (NAT) with matrix metalloproteinase 7 (MMP7) as a candidate biomarker.

STUDY DESIGN

RNA sequencing was performed on primary luminal progenitor cells from healthy breast, NATs, and tumors to identify transcriptomes enriched in NATs and breast cancer. Expression of select genes was validated via quantitative reverse transcription polymerase chain reaction of RNA and via immunohistochemistry of a tissue microarray of normal, NAT, and tumor samples of different genetic ancestry.

RESULTS

Twenty-six genes were significantly overexpressed in NATs and tumors compared with healthy controls at messenger RNA level and formed a para-inflammatory network. MMP7 had the greatest expression in tumor cells, with upregulation confirmed by quantitative reverse transcription polymerase chain reaction. Tumor-enriched but not NAT-enriched expression of MMP7 compared with healthy controls was reproduced at protein levels. When stratified by genetic ancestry, tumor-specific increase of MMP7 reached statistical significance in women of European ancestry.

CONCLUSIONS

Transcriptome differences across healthy, NAT, and tumor tissue in breast cancer demonstrate an active para-inflammatory network in NATs and indicate unsuitability of NATs as "normal controls" in biomarker discovery. The discordance between transcriptomic and proteomic MMP7 expression in NATs and the influence of genetic ancestry on its protein expression highlight the complexity in developing universally acceptable biomarkers of breast cancer and the importance of genetic ancestry in biomarker development.

Organoid cultures from normal and cancer-prone human breast tissues preserve complex epithelial lineages

Recently, organoid technology has been used to generate a large repository of breast cancer organoids. Here we present an extensive evaluation of the ability of organoid culture technology to preserve complex stem/progenitor and differentiated cell types via long-term propagation of normal human mammary tissues. Basal/stem and luminal progenitor cells can differentiate in culture to generate mature basal and luminal cell types, including ER+ cells that have been challenging to maintain in culture. Cells associated with increased cancer risk can also be propagated. Single-cell analyses of matched organoid cultures and native tissues by mass cytometry for 38 markers provide a higher resolution representation of the multiple mammary epithelial cell types in the organoids, and demonstrate that protein expression patterns of the tissue of origin can be preserved in culture. These studies indicate that organoid cultures provide a valuable platform for studies of mammary differentiation, transformation, and breast cancer risk.

Organoid technology has enabled the generation of several breast cancer organoids. Here, the authors combine propagation of normal human mammary tissues with mass cytometry to evaluate the ability of organoid culture technologies to preserve stem cells and differentiated cell types.

Environmental exposures, stem cells, and cancer

An estimated 70-90% of all cancers are linked to exposure to environmental risk factors. In parallel, the number of stem cells in a tissue has been shown to be a strong predictor of risk of developing cancer in that tissue. Tumors themselves are characterized by an acquisition of "stem cell" characteristics, and a growing body of evidence points to tumors themselves being sustained and propagated by a stem cell-like population. Here, we review our understanding of the interplay between environmental exposures, stem cell biology, and cancer. We provide an overview of the role of stem cells in development, tissue homeostasis, and wound repair. We discuss the pathways and mechanisms governing stem cell plasticity and regulation of the stem cell state, and describe experimental methods for assessment of stem cells. We then review the current understanding of how environmental exposures impact stem cell function relevant to carcinogenesis and cancer prevention, with a focus on environmental and occupational exposures to chemical, physical, and biological hazards. We also highlight key areas for future research in this area, including defining whether the biological basis for cancer disparities is related to effects of complex exposure mixtures on stem cell biology.

Inadequate DNA Damage Repair Promotes Mammary Transdifferentiation, Leading to BRCA1 Breast Cancer

Loss of BRCA1 p220 function often results in basal-like breast cancer (BLBC), but the underlying disease mechanism is largely opaque. In mammary epithelial cells (MECs), BRCA1 interacts with multiple proteins, including NUMB and HES1, to form complexes that participate in interstrand crosslink (ICL) DNA repair and MEC differentiation control. Unrepaired ICL damage results in aberrant transdifferentiation to a mesenchymal state of cultured, human basal-like MECs and to a basal/mesenchymal state in primary mouse luminal MECs. Loss of BRCA1, NUMB, or HES1 or chemically induced ICL damage in primary murine luminal MECs results in persistent DNA damage that triggers luminal to basal/mesenchymal transdifferentiation. In vivo single-cell analysis revealed a time-dependent evolution from normal luminal MECs to luminal progenitor-like tumor cells with basal/mesenchymal transdifferentiation during murine BRCA1 BLBC development. Growing DNA damage accompanied this malignant transformation.

Genetic Ancestry-dependent Differences in Breast Cancer-induced Field Defects in the Tumor-adjacent Normal Breast

PURPOSE

Genetic ancestry influences evolutionary pathways of cancers. However, whether ancestry influences cancer-induced field defects is unknown. The goal of this study was to utilize ancestry-mapped true normal breast tissues as controls to identify cancer-induced field defects in normal tissue adjacent to breast tumors (NATs) in women of African American (AA) and European (EA) ancestry.

EXPERIMENTAL DESIGN

A tissue microarray comprising breast tissues of ancestry-mapped 100 age-matched healthy women from the Komen Tissue Bank (KTB) at Indiana University (Indianapolis, IN) and tumor-NAT pairs from 100 women (300 samples total) was analyzed for the levels of ZEB1, an oncogenic transcription factor that is central to cell fate, mature luminal cell-enriched estrogen receptor alpha (ERα), GATA3, FOXA1, and for immune cell composition.

RESULTS

ZEB1+ cells, which were localized surrounding the ductal structures of the normal breast, were enriched in the KTB-normal of AA compared with KTB-normal of EA women. In contrast, in EA women, both NATs and tumors compared with KTB-normal contained higher levels of ZEB1+ cells. FOXA1 levels were lower in NATs compared with KTB-normal in AA but not in EA women. We also noted variations in the levels of GATA3, CD8+ T cells, PD1+ immune cells, and PDL1+ cell but not CD68+ macrophages in NATs of AA and EA women. ERα levels did not change in any of our analyses, pointing to the specificity of ancestry-dependent variations.

CONCLUSIONS

Genetic ancestry-mapped tissues from healthy individuals are required for proper assessment and development of cancer-induced field defects as early cancer detection markers. This finding is significant in light of recent discoveries of influence of genetic ancestry on both normal biology and tumor evolution.

Dual TGFβ/BMP Pathway Inhibition Enables Expansion and Characterization of Multiple Epithelial Cell Types of the Normal and Cancerous Breast

Functional modeling of normal breast epithelial hierarchy and stromal-epithelial cell interactions have been difficult due to inability to obtain sufficient stem-progenitor-mature epithelial and stromal cells. Recently reported epithelial reprogramming assay has partially overcome this limitation, but cross-contamination of cells from the feeder layer is a concern. The purpose of this study was to develop a feeder-layer-independent and inexpensive method to propagate multiple cell types from limited tissue resources. Cells obtained after enzymatic digestion of tissues collected at surgery or by core-needle biopsies were plated on tissue culture dishes precoated with laminin-5-rich-conditioned media from the rat bladder tumor cell line 804G and a defined growth media with inhibitors of ROCK, TGFβ, and BMP signaling. Cells were characterized by flow cytometry, mammosphere assay, 3D cultures, and xenograft studies. Cells from the healthy breasts included CD10⁺/EpCAM^- basal/myoepithelial, CD49f⁺/EpCAM⁺ luminal progenitor, CD49f^-/EpCAM⁺ mature luminal, CD73⁺/EpCAM⁺/CD90^- rare endogenous pluripotent somatic stem, CD73⁺/CD90⁺/EpCAM^-, estrogen receptor alpha-expressing ALCAM (CD166)⁺/EpCAM⁺, and ALDFLUOR⁺ stem/luminal progenitor subpopulations. Epithelial cells were luminal (KRT19⁺), basal (KRT14⁺), or dual-positive luminal/basal hybrid cells. While breast cells derived from BRCA1, BRCA2, and PALB2 mutation carriers did not display unique characteristics, cells from women with breast cancer-protective alleles showed enhanced differentiation. Cells could also be propagated from primary tumors and metastasis of breast, ovarian, and pancreatic cancer-neuroendocrine subtype. Xenograft studies confirmed tumorigenic properties of tumor-derived cells. IMPLICATIONS: Our method expands the scope of individualized studies of patient-derived cells and provides resources to model epithelial-stromal interactions under normal and pathologic conditions.

Free Fatty Acids Rewire Cancer Metabolism in Obesity-Associated Breast Cancer via Estrogen Receptor and mTOR Signaling

Obesity is a risk factor for postmenopausal estrogen receptor alpha (ERα)-positive (ER⁺) breast cancer. Molecular mechanisms underlying factors from plasma that contribute to this risk and how these mechanisms affect ERα signaling have yet to be elucidated. To identify such mechanisms, we performed whole metabolite and protein profiling in plasma samples from women at high risk for breast cancer, which led us to focus on factors that were differentially present in plasma of obese versus nonobese postmenopausal women. These studies, combined with in vitro assays, identified free fatty acids (FFA) as circulating plasma factors that correlated with increased proliferation and aggressiveness in ER⁺ breast cancer cells. FFAs activated both the ERα and mTOR pathways and rewired metabolism in breast cancer cells. Pathway preferential estrogen-1 (PaPE-1), which targets ERα and mTOR signaling, was able to block changes induced by FFA and was more effective in the presence of FFA. Collectively, these data suggest a role for obesity-associated gene and metabolic rewiring in providing new targetable vulnerabilities for ER⁺ breast cancer in postmenopausal women. Furthermore, they provide a basis for preclinical and clinical trials where the impact of agents that target ERα and mTOR signaling cross-talk would be tested to prevent ER⁺ breast cancers in obese postmenopausal women. SIGNIFICANCE: These findings show that obesity-associated changes in certain blood metabolites rewire metabolic programs in cancer cells, influence mammary epithelial cell tumorigenicity and aggressiveness, and increase breast cancer risk.

Lung cancer health disparities

Compared with all other racial and ethnic groups in the United States, African Americans are disproportionally affected by lung cancer, both in terms of incidence and survival. It is likely that smoking, as the main etiological factor associated with lung cancer, contributes to these disparities, but the precise mechanism is still unclear. This paper seeks to explore the history of lung cancer disparities and review to the literature regarding the various factors that contribute to them.

Racial Disparity and Triple-Negative Breast Cancer in African-American Women: A Multifaceted Affair between Obesity, Biology, and Socioeconomic Determinants

Triple negative breast cancer (TNBC) is a molecularly heterogeneous disease whose incidence is disproportionately higher in African American (AA) women compared to European American (EA) women. Earlier onset, more advanced stage at diagnosis, and aggressive tumor phenotype are some of the characteristic features of TNBC in women with African ethnicity in comparison to EA women, denoting one of the most significant examples of racial disparity in oncology. It is still contentious whether health disparities result in aggressive behavior of TNBC in AA women or it is indeed a molecularly distinct disease. Given the “gaps-in-knowledge” surrounding racial disparity in TNBC, this review discusses various socioeconomic factors and the genetic predispositions contributing to poor prognosis of TNBC in AA women. While socioeconomic factors may contribute to poorer survival, multiple preclinical and clinical studies suggest inherent genetic risk factors and aberrant activation of oncogenic pathways in AA TNBC. Additionally, AA women are more likely to be obese and obesity is known to drive a molecular circuitry resulting in aggressive tumor progression indicating a potential obesity-TNBC axis at work in AA women. Given the multifactorial nature of AA TNBC, a transdisciplinary approach may help bridge the disparity that exists between AA and EA TNBC.

Comparative Transcriptome Profiling Reveals Coding and Noncoding RNA Differences in NSCLC from African Americans and European Americans

Purpose: To determine whether racial differences in gene and miRNA expression translates to differences in lung tumor biology with clinical relevance in African Americans (AAs) and European Americans (EAs).Experimental Design: The NCI-Maryland Case Control Study includes seven Baltimore City hospitals and is overrepresented with AA patients (∼40%). Patients that underwent curative NSCLC surgery between 1998 and 2014 were enrolled. Comparative molecular profiling used mRNA (n = 22 AAs and 19 EAs) and miRNA (n = 42 AAs and 55 EAs) expression arrays to track differences in paired fresh frozen normal tissues and lung tumor specimens from AAs and EAs. Pathway enrichment, predicted drug response, tumor microenvironment infiltration, cancer immunotherapy antigen profiling, and miRNA target enrichment were assessed.Results: AA-enriched differential gene expression was characterized by stem cell and invasion pathways. Differential gene expression in lung tumors from EAs was primarily characterized by cell proliferation pathways. Population-specific gene expression was partly driven by population-specific miRNA expression profiles. Drug susceptibility predictions revealed a strong inverse correlation between AA resistance and EA sensitivity to the same panel of drugs. Statistically significant differences in M1 and M2 macrophage infiltration were observed in AAs (P < 0.05); however, PD-L1, PD-L2 expression was similar between both.Conclusions: Comparative transcriptomic profiling revealed clear differences in lung tumor biology between AAs and EAs. Increased participation by AAs in lung cancer clinical trials are needed to integrate, and leverage, transcriptomic differences with other clinical information to maximize therapeutic benefit in both AAs and EAs. Clin Cancer Res; 23(23); 7412-25. ©2017 AACR.

Normal Breast-Derived Epithelial Cells with Luminal and Intrinsic Subtype-Enriched Gene Expression Document Interindividual Differences in Their Differentiation Cascade

Cell-type origin is one of the factors that determine molecular features of tumors, but resources to validate this concept are scarce because of technical difficulties in propagating major cell types of adult organs. Previous attempts to generate such resources to study breast cancer have yielded predominantly basal-type cell lines. We have created a panel of immortalized cell lines from core breast biopsies of ancestry-mapped healthy women that form ductal structures similar to normal breast in 3D cultures and expressed markers of major cell types, including the luminal-differentiated cell-enriched ERα-FOXA1-GATA3 transcription factor network. We have also created cell lines from PROCR (CD201)⁺/EpCAM^- cells that are likely the "normal" counterpart of the claudin-low subtype of breast cancers. RNA-seq and PAM50-intrinsic subtype clustering identified these cell lines as the "normal" counterparts of luminal A, basal, and normal-like subtypes and validated via immunostaining with basal-enriched KRT14 and luminal-enriched KRT19. We further characterized these cell lines by flow cytometry for distribution patterns of stem/basal, luminal-progenitor, mature/differentiated, multipotent PROCR⁺ cells, and organogenesis-enriched epithelial/mesenchymal hybrid cells using CD44/CD24, CD49f/EpCAM, CD271/EpCAM, CD201/EpCAM, and ALDEFLUOR assays and E-cadherin/vimentin double staining. These cell lines showed interindividual heterogeneity in stemness/differentiation capabilities and baseline activity of signaling molecules such as NF-κB, AKT2, pERK, and BRD4. These resources can be used to test the emerging concept that genetic variations in regulatory regions contribute to widespread differences in gene expression in "normal" conditions among the general population and can delineate the impact of cell-type origin on tumor progression.Significance: In addition to providing a valuable resource for the breast cancer research community to investigate cell-type origin of different subtypes of breast cancer, this study highlights interindividual differences in normal breast, emphasizing the need to use "normal" cells from multiple sources as controls to decipher the effects of cancer-specific genomic aberrations. Cancer Res; 78(17); 5107-23. ©2018 AACR.

Dependence receptor UNC5A restricts luminal to basal breast cancer plasticity and metastasis

Background

The majority of estrogen receptor-positive (ERα⁺) breast cancers respond to endocrine therapies. However, resistance to endocrine therapies is common in 30% of cases, which may be due to altered ERα signaling and/or enhanced plasticity of cancer cells leading to breast cancer subtype conversion. The mechanisms leading to enhanced plasticity of ERα-positive cancer cells are unknown.

Methods

We used short hairpin (sh)RNA and/or the CRISPR/Cas9 system to knockdown the expression of the dependence receptor UNC5A in ERα⁺ MCF7 and T-47D cell lines. RNA-seq, quantitative reverse transcription polymerase chain reaction, chromatin immunoprecipitation, and Western blotting were used to measure the effect of UNC5A knockdown on basal and estradiol (E2)-regulated gene expression. Mammosphere assay, flow cytometry, and immunofluorescence were used to determine the role of UNC5A in restricting plasticity. Xenograft models were used to measure the effect of UNC5A knockdown on tumor growth and metastasis. Tissue microarray and immunohistochemistry were utilized to determine the prognostic value of UNC5A in breast cancer. Log-rank test, one-way, and two-way analysis of variance (ANOVA) were used for statistical analyses.

Results

Knockdown of the E2-inducible UNC5A resulted in altered basal gene expression affecting plasma membrane integrity and ERα signaling, as evident from ligand-independent activity of ERα, altered turnover of phosphorylated ERα, unique E2-dependent expression of genes effecting histone demethylase activity, enhanced upregulation of E2-inducible genes such as BCL2, and E2-independent tumorigenesis accompanied by multiorgan metastases. UNC5A depletion led to the appearance of a luminal/basal hybrid phenotype supported by elevated expression of basal/stem cell-enriched ∆Np63, CD44, CD49f, epidermal growth factor receptor (EGFR), and the lymphatic vessel permeability factor NTN4, but lower expression of luminal/alveolar differentiation-associated ELF5 while maintaining functional ERα. In addition, UNC5A-depleted cells acquired bipotent luminal progenitor characteristics based on KRT14⁺/KRT19⁺ and CD49f⁺/EpCAM⁺ phenotype. Consistent with in vitro results, UNC5A expression negatively correlated with EGFR expression in breast tumors, and lower expression of UNC5A, particularly in ERα⁺/PR⁺/HER2⁻ tumors, was associated with poor outcome.

Conclusion

These studies reveal an unexpected role of the axon guidance receptor UNC5A in fine-tuning ERα and EGFR signaling and the luminal progenitor status of hormone-sensitive breast cancers. Furthermore, UNC5A knockdown cells provide an ideal model system to investigate metastasis of ERα⁺ breast cancers.

Electronic supplementary material

The online version of this article (10.1186/s13058-018-0963-5) contains supplementary material, which is available to authorized users.

Heterogeneity of Human Breast Stem and Progenitor Cells as Revealed by Transcriptional Profiling

During development, the mammary gland undergoes extensive remodeling driven by stem cells. Breast cancers are also hierarchically organized and driven by cancer stem cells characterized by CD44⁺CD24^low/− or aldehyde dehydrogenase (ALDH) expression. These markers identify mesenchymal and epithelial populations both capable of tumor initiation. Less is known about these populations in non-cancerous mammary glands. From RNA sequencing, ALDH⁺ and ALDH⁻CD44⁺CD24⁻ human mammary cells have epithelial-like and mesenchymal-like characteristics, respectively, with some co-expressing ALDH⁺ and CD44⁺CD24⁻ by flow cytometry. At the single-cell level, these cells have the greatest mammosphere-forming capacity and express high levels of stemness and epithelial-to-mesenchymal transition-associated genes including ID1, SOX2, TWIST1, and ZEB2. We further identify single ALDH⁺ cells with a hybrid epithelial/mesenchymal phenotype that express genes associated with aggressive triple-negative breast cancers. These results highlight single-cell analyses to characterize tissue heterogeneity, even in marker-enriched populations, and identify genes and pathways that define this heterogeneity.

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Isolation and RNA-seq of ALDH⁺ and CD44⁺CD24⁻ breast cells

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Unlike in cancer, there is substantial overlap in ALDH⁺ and CD44⁺CD24⁻ populations

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Single-cell analysis of ALDH⁺ cells identifies unexpected subpopulation structure

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Hybrid epithelial/mesenchymal ALDH⁺ cells have a cancer-like expression signature

Characterization of primary human mammary epithelial cells isolated and propagated by conditional reprogrammed cell culture

Purpose

Conditional reprogramming methods allow for the inexhaustible in vitro proliferation of primary epithelial cells from human tissue specimens. This methodology has the potential to enhance the utility of primary cell culture as a model for mammary gland research. However, few studies have systematically characterized this method in generating in vitro normal human mammary epithelial cell models.

Results

We show that cells derived from fresh normal breast tissues can be propagated and exhibit heterogeneous morphologic features. The cultures are composed of CK18, desmoglein 3, and CK19-positive luminal cells and vimentin, p63, and CK14-positive myoepithelial cells, suggesting the maintenance of in vivo heterogeneity. In addition, the cultures contain subpopulations with different CD49f and EpCAM expression profiles. When grown in 3D conditions, cells self-organize into distinct structures that express either luminal or basal cell markers. Among these structures, CK8-positive cells enclosing a lumen are capable of differentiation into milk-producing cells in the presence of lactogenic stimulus. Furthermore, our short-term cultures retain the expression of ERα, as well as its ability to respond to estrogen stimulation.

Materials and Methods

We have investigated conditionally reprogrammed normal epithelial cells in terms of cell type heterogeneity, cellular marker expression, and structural arrangement in two-dimensional (2D) and three-dimensional (3D) systems.

Conclusions

The conditional reprogramming methodology allows generation of a heterogeneous culture from normal human mammary tissue in vitro. We believe that this cell culture model will provide a valuable tool to study mammary cell function and malignant transformation.

Race Disparities in the Contribution of miRNA Isoforms and tRNA-Derived Fragments to Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a breast cancer subtype characterized by marked differences between White and Black/African-American women. We performed a systems-level analysis on datasets from The Cancer Genome Atlas to elucidate how the expression patterns of mRNAs are shaped by regulatory noncoding RNAs (ncRNA). Specifically, we studied isomiRs, that is, isoforms of miRNAs, and tRNA-derived fragments (tRF). In normal breast tissue, we observed a marked cohesiveness in both the ncRNA and mRNA layers and the associations between them. This cohesiveness was widely disrupted in TNBC. Many mRNAs become either differentially expressed or differentially wired between normal breast and TNBC in tandem with isomiR or tRF dysregulation. The affected pathways included energy metabolism, cell signaling, and immune responses. Within TNBC, the wiring of the affected pathways with isomiRs and tRFs differed in each race. Multiple isomiRs and tRFs arising from specific miRNA loci (e.g., miR-200c, miR-21, the miR-17/92 cluster, the miR-183/96/182 cluster) and from specific tRNA loci (e.g., the nuclear tRNA^Gly and tRNA^Leu, the mitochondrial tRNA^Val and tRNA^Pro) were strongly associated with the observed race disparities in TNBC. We highlight the race-specific aspects of transcriptome wiring by discussing in detail the metastasis-related MAPK and the Wnt/β-catenin signaling pathways, two of the many key pathways that were found differentially wired. In conclusion, by employing a data- and knowledge-driven approach, we comprehensively analyzed the normal and cancer transcriptomes to uncover novel key contributors to the race-based disparities of TNBC.Significance: This big data-driven study comparing normal and cancer transcriptomes uncovers RNA expression differences between Caucasian and African-American patients with triple-negative breast cancer that might help explain disparities in incidence and aggressive character. Cancer Res; 78(5); 1140-54. ©2017 AACR.

A system for detecting high impact-low frequency mutations in primary tumors and metastases

Tumor complexity and intratumor heterogeneity contribute to subclonal diversity. Despite advances in next-generation sequencing (NGS) and bioinformatics, detecting rare mutations in primary tumors and metastases contributing to subclonal diversity is a challenge for precision genomics. Here, in order to identify rare mutations, we adapted a recently described epithelial reprograming assay for short-term propagation of epithelial cells from primary and metastatic tumors. Using this approach, we expanded minor clones and obtained epithelial cell-specific DNA/RNA for quantitative NGS analysis. Comparative Ampliseq Comprehensive Cancer Panel sequence analyses were performed on DNA from unprocessed breast tumor and tumor cells propagated from the same tumor. We identified previously uncharacterized mutations present only in the cultured tumor cells, a subset of which has been reported in brain metastatic but not primary breast tumors. In addition, whole-genome sequencing identified mutations enriched in liver metastases of various cancers, including Notch pathway mutations/chromosomal inversions in 5/5 liver metastases, irrespective of cancer types. Mutations/rearrangements in FHIT, involved in purine metabolism, were detected in 4/5 liver metastases, and the same four liver metastases shared mutations in 32 genes, including mutations of different HLA-DR family members affecting OX40 signaling pathway, which could impact the immune response to metastatic cells. Pathway analyses of all mutated genes in liver metastases showed aberrant tumor necrosis factor and transforming growth factor signaling in metastatic cells. Epigenetic regulators including KMT2C/MLL3 and ARID1B, which are mutated in >50% of hepatocellular carcinomas, were also mutated in liver metastases. Thus, irrespective of cancer types, organ-specific metastases may share common genomic aberrations. Since recent studies show independent evolution of primary tumors and metastases and in most cases mutation burden is higher in metastases than primary tumors, the method described here may allow early detection of subclonal somatic alterations associated with metastatic progression and potentially identify therapeutically actionable, metastasis-specific genomic aberrations.

Racial Differences in Cancer Susceptibility and Survival: More Than the Color of the Skin?

Epidemiological studies point to race as a determining factor in cancer susceptibility. In US registries recording cancer incidence and survival by race (distinguishing 'black versus white'), individuals of African ancestry have a globally increased risk of malignancies compared with Caucasians and Asian Americans. Differences in socioeconomic status and health-care access play a key role. However, the lesser disease susceptibility of Hispanic populations with comparable lifestyles and socioeconomic status as African Americans (Hispanic paradox) points to the concomitant importance of genetic determinants. Here, we overview the molecular basis of racial disparity in cancer susceptibility ranging from genetic polymorphisms and cancer-driver gene mutations to obesity, chronic inflammation, and immune responses. We discuss implications for race-adapted cancer screening programs and clinical trials to reduce disparities in cancer burden.

Individualized Breast Cancer Characterization through Single-Cell Analysis of Tumor and Adjacent Normal Cells

There is a need to individualize assays for tumor molecular phenotyping, given variations in the differentiation status of tumor and normal tissues in different patients. To address this, we performed single-cell genomics of breast tumors and adjacent normal cells propagated for a short duration under growth conditions that enable epithelial reprogramming. Cells analyzed were either unselected for a specific subpopulation or phenotypically defined as undifferentiated and highly clonogenic ALDH⁺/CD49f⁺/EpCAM⁺ luminal progenitors, which express both basal cell and luminal cell-enriched genes. We analyzed 420 tumor cells and 284 adjacent normal cells for expression of 93 genes that included a PAM50-intrinsic subtype classifier and stemness-related genes. ALDH⁺/CD49f⁺/EpCAM⁺ tumor and normal cells clustered differently compared with unselected tumor and normal cells. PAM50 gene-set analyses of ALDH⁺/CD49f⁺/EpCAM⁺ populations efficiently identified major and minor clones of tumor cells, with the major clone resembling clinical parameters of the tumor. Similarly, a stemness-associated gene set identified clones with divergent stemness pathway activation within the same tumor. This refined expression profiling technique distinguished genes truly deregulated in cancer from genes that identify cellular precursors of tumors. Collectively, the assays presented here enable more precise identification of cancer-deregulated genes, allow for early identification of therapeutically targetable tumor cell subpopulations, and ultimately provide a refinement of precision therapeutics for cancer treatment. Cancer Res; 77(10); 2759-69. ©2017 AACR.

Distinct Effects of Adipose-Derived Stem Cells and Adipocytes on Normal and Cancer Cell Hierarchy

Adipose-derived stem cells (ASC) have received considerable attention in oncology because of the known direct link between obesity and cancer as well as the use of ASCs in reconstructive surgery after tumor ablation. Previous studies have documented how cancer cells commandeer ASCs to support their survival by altering extracellular matrix composition and stiffness, migration, and metastasis. This study focused on delineating the effects of ASCs and adipocytes on the self-renewal of stem/progenitor cells and hierarchy of breast epithelial cells. The immortalized breast epithelial cell line MCF10A, ductal carcinoma in situ (DCIS) cell lines MCF10DCIS.com and SUM225, and MCF10A-overexpressing SRC oncogene were examined using a mammosphere assay and flow cytometry for the effects of ASCs on their self-renewal and stem-luminal progenitor-differentiated cell surface marker profiles. Interestingly, ASCs promoted the self-renewal of all cell types except SUM225. ASC coculture or treatment with ASC conditioned media altered the number of CD49f(high)/EpCAM(low) basal/stem-like and CD49f(medium)/EpCAM(medium) luminal progenitor cells. Among multiple factors secreted by ASCs, IFNγ and hepatocyte growth factor (HGF) displayed unique actions on epithelial cell hierarchy. IFNγ increased stem/progenitor-like cells while simultaneously reducing the size of mammospheres, whereas HGF increased the size of mammospheres with an accompanying increase in luminal progenitor cells. ASCs expressed higher levels of HGF, whereas adipocytes expressed higher levels of IFNγ. As luminal progenitor cells are believed to be prone for transformation, IFNγ and HGF expression status of ASCs may influence susceptibility for developing breast cancer as well as on outcomes of autologous fat transplantation on residual/dormant tumor cells.

IMPLICATIONS

This study suggests that the ratio of ASCs to adipocytes influences cancer cell hierarchy, which may impact incidence and progression. Mol Cancer Res; 14(7); 660-71. ©2016 AACR.