Regulation of EZH2 protein stability: new mechanisms, roles in tumorigenesis, and roads to the clinic

The importance of EZH2 as a key methyltransferase has been well documented theoretically. Practically, the first EZH2 inhibitor Tazemetostat (EPZ6438), was approved by FDA in 2020 and is used in clinic. However, for most solid tumors it is not as effective as desired and the scope of clinical indications is limited, suggesting that targeting its enzymatic activity may not be sufficient. Recent technologies focusing on the degradation of EZH2 protein have drawn attention due to their potential robust effects. This review focuses on the molecular mechanisms that regulate EZH2 protein stability via post-translational modifications (PTMs), mainly including ubiquitination, phosphorylation, and acetylation. In addition, we discuss recent advancements of multiple proteolysis targeting chimeras (PROTACs) strategies and the latest degraders that can downregulate EZH2 protein. We aim to highlight future directions to expand the application of novel EZH2 inhibitors by targeting both EZH2 enzymatic activity and protein stability.

Identification of Glandular (Acinar)/Tubule Formation in Invasive Carcinoma of the Breast: A Study to Determine Concordance Using the World Health Organization Definition

CONTEXT.—

The Nottingham Grading System (NGS) developed by Elston and Ellis is used to grade invasive breast cancer (IBC). Glandular (acinar)/tubule formation is a component of NGS.

OBJECTIVE.—

To investigate the ability of pathologists to identify individual structures that should be classified as glandular (acinar)/tubule formation.

DESIGN.—

A total of 58 hematoxylin-eosin photographic images of IBC with 1 structure circled were classified as tubules (41 cases) or nontubules (17 cases) by Professor Ellis. Images were sent as a PowerPoint (Microsoft) file to breast pathologists, who were provided with the World Health Organization definition of a tubule and asked to determine if a circled structure represented a tubule.

RESULTS.—

Among 35 pathologists, the κ statistic for assessing agreement in evaluating the 58 images was 0.324 (95% CI, 0.314-0.335). The median concordance rate between a participating pathologist and Professor Ellis was 94.1% for evaluating 17 nontubule cases and 53.7% for 41 tubule cases. A total of 41% of the tubule cases were classified correctly by less than 50% of pathologists. Structures classified as tubules by Professor Ellis but often not recognized as tubules by pathologists included glands with complex architecture, mucinous carcinoma, and the "inverted tubule" pattern of micropapillary carcinoma. A total of 80% of participants reported that they did not have clarity on what represented a tubule.

CONCLUSIONS.—

We identified structures that should be included as tubules but that were not readily identified by pathologists. Greater concordance for identification of tubules might be obtained by providing more detailed images and descriptions of the types of structures included as tubules.

A hybrid breast cancer/mesenchymal stem cell population enhances chemoresistance and metastasis

Patients with triple-negative breast cancer remain at risk for metastatic disease despite treatment. The acquisition of chemoresistance is a major cause of tumor relapse and death, but the mechanisms are far from understood. We have demonstrated that breast cancer cells (BCCs) can engulf mesenchymal stem/stromal cells (MSCs), leading to enhanced dissemination. Here, we show that clinical samples of primary invasive carcinoma and chemoresistant breast cancer metastasis contain a unique hybrid cancer cell population coexpressing pancytokeratin and the MSC marker fibroblast activation protein-α. We show that hybrid cells form in primary tumors and that they promote breast cancer metastasis and chemoresistance. Using single-cell microfluidics and in vivo models, we found that there are polyploid senescent cells within the hybrid cell population that contribute to metastatic dissemination. Our data reveal that Wnt Family Member 5A (WNT5A) plays a crucial role in supporting the chemoresistance properties of hybrid cells. Furthermore, we identified that WNT5A mediates hybrid cell formation through a phagocytosis-like mechanism that requires BCC-derived IL-6 and MSC-derived C-C Motif Chemokine Ligand 2. These findings reveal hybrid cell formation as a mechanism of chemoresistance and suggest that interrupting this mechanism may be a strategy in overcoming breast cancer drug resistance.

Triple-negative breast cancer cells invade adipocyte/preadipocyte-encapsulating geometrically inverted mammary organoids

This paper describes the manufacture of geometrically inverted mammary organoids encapsulating primary mammary preadipocytes and adipocytes. Material manipulation in an array of 192 hanging drops induces cells to self-assemble into inside-out organoids where an adipose tissue core is enveloped by a cell-produced basement membrane, indicated by laminin V staining and then a continuous layer of mammary epithelial cells. This inverted tissue structure enables investigation of multiple mammary cancer subtypes, with a significantly higher extent of invasion by triple-negative MDA-MB-231 breast cancer cells compared to MCF7 cells. By seeding cancer cells into co-culture around pre-formed organoids with encapsulated preadipocytes/adipocytes, invasion through the epithelium, then into the adipose core is observable through acquisition of confocal image stacks of whole mount specimens. Furthermore, in regions of the connective tissue core where invasion occurs, there is an accumulation of collagen in the microenvironment. Suggesting that this collagen may be conducive to increased invasiveness, the anti-fibrotic drug pirfenidone shows efficacy in this model by slowing invasion. Comparison of adipose tissue derived from three different donors shows method consistency as well as the potential to evaluate donor cell-based biological variability. Insight box Geometrically inverted mammary organoids encapsulating primary preadipocytes/adipocytes (P/As) are bioengineered using a minimal amount of Matrigel scaffolding. Use of this eversion-free method is key to production of adipose mammary organoids (AMOs) where not only the epithelial polarity but also the entire self-organizing arrangement, including adipose position, is inside-out. While an epithelial-only structure can analyze cancer cell invasion, P/As are required for invasion-associated collagen deposition and efficacy of pirfenidone to counteract collagen deposition and associated invasion. The methods described strike a balance between repeatability and preservation of biological variability: AMOs form consistently across multiple adipose cell donors while revealing cancer cell invasion differences.

Personalized Oncology by In Vivo Chemical Imaging: Photoacoustic Mapping of Tumor Oxygen Predicts Radiotherapy Efficacy

We hereby apply the approach of photoacoustic chemical imaging, performing an in vivo chemical analysis that is spatially resolved (200 μm) and in real time, to predict a given tumor's response to therapy. Using triple negative breast cancer as a model, we took photoacoustic images of tumors' oxygen distributions in patient-derived xenografts (PDXs) in mice using biocompatible, oxygen-sensitive tumor-targeted chemical contrast nanoelements (nanosonophores), which function as contrast agents for photoacoustic imaging. Following radiation therapy, we established a quantitatively significant correlation between the spatial distribution of the initial oxygen levels in the tumor and its spatial distribution of the therapy's efficacy: the lower the local oxygen, the lower the local radiation therapy efficacy. We thus provide a simple, noninvasive, and inexpensive method to both predict the efficacy of radiation therapy for a given tumor and identify treatment-resistant regions within the tumor's microenvironment.

Abstract 2476: Spatiotemporal analyses of preclinical glioma models reveal ‘oncostreams’ as dynamic fascicles regulating tumor mesenchymal transformation, invasion, and malignancy

Glioblastomas multiforme (GBMs) are the most lethal tumors of the brain. Tumoral mesenchymal transformation is a hallmark of GBMs associated with alterations in cellular morphology and dynamic organization. However, little is known about the mechanisms that control this pathological process. Here, we report a comprehensive spatiotemporal study integrating novel intra-tumoral histopathological structures, ‘oncostreams’, with tumor dynamic properties, microenvironment assets and spatial molecular features. Cellular analyses of genetic engineered mouse models of glioma identified that oncostreams are heterogenous structures formed by elongated and aligned neoplastic cells enriched in non-neoplastic cells such as ACTA2+ mesenchymal like cells and CD68+ tumor associated microglia/macrophages (TAM). Deep learning analysis of H&E glioma histological samples from mouse and human gliomas identified that oncostream density correlates with tumor aggressiveness. To determine whether oncostreams fascicles are characterized by a specific gene expression profile, we performed transcriptomic analysis using laser capture microdissection coupled to RNA-sequencing. We found that oncostreams are defined by a transcriptomic signature enriched in mesenchymal genes. Network analyses identified that COL1A1 is a critical gene that regulates oncostream organization and function. Correspondingly, human and mouse high-grade gliomas with high oncostream densities showed prominent alignment of collagen fibers along these fascicles and higher COL1A1 expression compared to low-grade gliomas. To evaluate the functional role of COL1A1 in oncostream formation we generated a COL1A1-deficient GEMM of glioma. We observed that COL1A1 inhibition decreased oncostream formation, impaired tumor cell proliferation and remodeled the tumor microenvironment by diminishing CD68+ TAM cells, CD31+ endothelial vascular proliferation and ACTA2+ perivascular mesenchymal cells, thus increasing animal survival. Further studies, using time lapse confocal imaging in ex vivo glioma explants, and intravital imaging in vivo demonstrated that oncostreams are organized collective dynamic structures present at the tumor core and the invasive tumor border. Oncostreams dynamics increased the intra-tumoral spread of cells within the tumor and foster glioma aggressiveness through collective invasion of the normal brain parenchyma. The analysis of glioma invasion in COL1A1 knockdown tumors exhibited a reduction in collective migration patterns, strongly supporting its importance in tumor progression. We propose that oncostreams represent a novel pathological marker of potential value for diagnosis and COL1A1 depletion within oncostreams is a promising approach and reprogram mesenchymal transformation to reduce the tumor malignancy.

Citation Format: Andrea Comba, Syed Faisal, Patrick J. Dunn, Anna E. Argento, Todd C. Hollon, Wajd N. Al-Holou, Maria L. Varela, Daniel B. Zamler, Gunnar L. Quass, Pierre F. Apostolides, Christine E. Brown, Phillip E. E. Kish, Alon Kahana, Celina G. Kleer, Sebastien Motsch, Maria G. Castro, Pedro R. Lowenstein. Spatiotemporal analyses of preclinical glioma models reveal ‘oncostreams’ as dynamic fascicles regulating tumor mesenchymal transformation, invasion, and malignancy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2476.

Quantitative Image Analysis as an Adjunct to Manual Scoring of ER, PgR, and HER2 in Invasive Breast Carcinoma

OBJECTIVES

Biomarker expression evaluation for estrogen receptor (ER), progesterone receptor (PgR), and human epidermal growth factor receptor 2 (HER2) is an essential prognostic and predictive parameter for breast cancer and critical for guiding hormonal and neoadjuvant therapy. This study compared quantitative image analysis (QIA) with pathologists' scoring for ER, PgR, and HER2.

METHODS

A retrospective analysis was undertaken of 1,367 invasive breast carcinomas, including all histopathology subtypes, for which ER, PgR, and HER2 were analyzed by manual scoring and QIA. The resulting scores were compared, and in a subset of HER2 cases (n = 373, 26%), scores were correlated with available fluorescence in situ hybridization (FISH) results.

RESULTS

Concordance between QIA and manual scores for ER, PgR, and HER2 was 93%, 96%, and 90%, respectively. Discordant cases had low positive scores (1%-10%) for ER (n = 33), were due to nonrepresentative region selection (eg, ductal carcinoma in situ) or tumor heterogeneity for PgR (n = 43), and were of one-step difference (negative to equivocal, equivocal to positive, or vice versa) for HER2 (n = 90). Among HER2 cases where FISH results were available, only four (1.0%) showed discordant QIA and FISH results.

CONCLUSIONS

QIA is a computer-aided diagnostic support tool for pathologists. It significantly improves ER, PgR, and HER2 scoring standardization. QIA demonstrated excellent concordance with pathologists' scores. To avoid pitfalls, pathologist oversight of representative region selection is recommended.

Abstract P5-06-06: Hybrid cells generated by Mesenchymal Stem/Stromal Cell Engulfment enhance breast cancer metastasis upon Doxorubicin treatment in mouse model

Introduction: Our previous findings evidenced that BCCs engulf MSCs in clinical samples of breast cancer metastasis. Among the BCC-engulfing MSCs, we observed that some of them retain some markers of MSCs, resulting in the generation of hybrid cancer cell population. However, the mechanisms of hybrid cancer cell formation and the phenotypic features of hybrid cancer cells are still unclear. Here, we tested the hypothesis that hybrid cancer cells may acquire in vivo a dormant phenotype, with an increased survival advantage and chemoresistant features. Method: MSC labeled with DsRED (DsRED-MSC) were cultured with MDA-MB-231 labeled with GFP (GFP-231) to generate a hybrid cell-enriched co-culture. Live imaging microscopy, flow cytometry, cytokine array and western blot were used to characterize the hybrid cancer cells. GFP-231 were incubated with phRodo labeled MSC and subjected to phagocytosis assay. In the co-culture of DsRED-MSC with GFP-231 treated with Doxorubicin (Doxo) or untreated, we analyzed the percentage of DsRED+/GFP+ hybrid population. Hybrid-enriched co-culture or GFP-231 in single culture labeled with firefly luciferase were intracardially injected in NOD/SCID mice and monitored for metastases by bioluminescence imaging (BLI), upon Doxo treatment. After collecting the tissues at necropsy, metastases were identified by GFP fluorescence microscopy. Results: In co-cultures, DsRED+/GFP+ hybrid cells had a higher percentage of Ki-67 low in G1 and polyploidy compared to GFP-231+ cells. Hybrid cancer cells have a distinct cytokine profile than control BCCs with increased levels of senescence-associated secretory phenotype (SASP) factors. Hybrid cancer cell formation occurs through a phagocytosis-like mechanism, which involves WNT5A and MSR1. Doxo treatment increased the percentage of DsRED+/GFP+ hybrid cells, whereas reduced the percentage of GFP-231+ cells. In animal study, we observed a lower qualitative BLI intensity in mice injected with hybrid cell-enriched co-cultures compared to control. Doxo treatment increased the metastatic burden in mice inoculated with hybrid cell-enriched co-cultures compared to untreated Conclusions: MSC engulfment by BCCs results in a hybrid multinucleated cell population. Hybrid cells acquire a dormant phenotype characterized by a higher percentage of Ki-67low cells in G1 and a senescent phenotype compared to controls. Hybrid-cell-enriched co-cultures established less metastasis compared to control in vivo, but became resistant and acquire the ability to form metastasis upon doxo treatment.

Citation Format: Giuseppina Augimeri, Maria E. Gonzalez, Daniela Bonofiglio, Sebastiano Andò, Celina G. Kleer. Hybrid cells generated by Mesenchymal Stem/Stromal Cell Engulfment enhance breast cancer metastasis upon Doxorubicin treatment in mouse model [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-06-06.

Depletion of CCN1/CYR61 reduces triple-negative/basal-like breast cancer aggressiveness

Triple-negative/basal-like breast cancer (BC) is characterized by aggressive biological features, which allow relapse and metastatic spread to occur more frequently than in hormone receptor-positive (luminal) subtypes. The molecular complexity of triple-negative/basal-like BC poses major challenges for the implementation of targeted therapies, and chemotherapy remains the standard approach at all stages. The matricellular protein cysteine-rich angiogenic inducer 61 (CCN1/CYR61) is associated with aggressive metastatic phenotypes and poor prognosis in BC, but it is unclear whether anti-CCN1 approaches can be successfully applied in triple-negative/basal-like BC. Herein, we first characterized the prevalence of CNN1 expression in matched samples of primary tumors and metastatic relapse in a series of patients with BC. We then investigated the biological effect of CCN1 depletion on tumorigenic traits in vitro and in vivo using archetypal TNBC cell lines. Immunohistochemical analyses of tissue microarrays revealed a significant increase of the highest CCN1 score in recurrent tissues of triple-negative/basal-like BC tumors. Stable silencing of CCN1 in triple-negative/basal-like BC cells promoted a marked reduction in the expression of the CCN1 integrin receptor α_vβ₃, inhibited anchorage-dependent cell growth, reduced clonogenicity, and impaired migration capacity. In an orthotopic model of triple-negative/basal-like BC, silencing of CCN1 notably reduced tumor burden, which was accompanied by decreased microvessel density and concurrent induction of the luminal epithelial marker E-cadherin. Thus, CNN1/CYR61-targeting strategies might have therapeutic value in suppressing the biological aggressiveness of triple-negative/basal-like BC.

Abstract ES13-1: Targeting EZH2 functions

Anaplasia, or loss of mature specialized features, is a characteristic of malignant cells. Thus, it is not surprising that deregulation of proteins that govern cell type identity may lead to cancer. EZH2, a Polycomb group protein which regulates transcriptional memory in normal cells through H3K27 trimethylation, is overexpressed in breast cancer compared to normal breast, and is a tissue-based biomarker of survival in patients with breast cancer. EZH2 enhances breast cancer initiation and progression, making it a desirable therapeutic target with several inhibitors already in clinical trials. While the main mechanism of EZH2 oncogenic function has been ascribed to trimethylation of H3K27, mounting evidence supports that EZH2 also functions through non-canonical H3K27me3-independent mechanisms, especially in triple negative breast carcinomas (TNBC). These include transcriptional activation through direct binding to the NOTCH1 promoter to regulate cancer stem cells, and EZH2 phosphorylation at specific sites to either reduce affinity for histone H3 and/or increase binding to nonhistone proteins to promote metastasis. This body of work highlights the importance of blocking EZH2 H3K27me3-dependent as well as non-canonical functions in TNBC to improve outcomes. In this Educational Session, I will discuss current insights into EZH2 oncogenic mechanisms in TNBC including metaplastic carcinomas, an aggressive and chemoresistant TNBC subtype. We will also discuss how the discovery of novel EZH2 mechanisms may set the stage for the development of previously unconsidered therapeutic opportunities.

Citation Format: CG Kleer. Targeting EZH2 functions [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr ES13-1.

The matricellular protein CCN6 differentially regulates mitochondrial metabolism in normal epithelium and in metaplastic breast carcinomas

Metaplastic breast carcinoma (MBC) is an aggressive subtype of triple negative breast cancer with undefined precursors, limited response to chemotherapy, and frequent distant metastasis. Our laboratory has reported that CCN6/WISP3, a secreted protein that regulates growth factor signaling, is downregulated in over 85% of MBCs. Through generation of a mammary epithelial cell-specific Ccn6 knockout mouse model (MMTV-cre;Ccn6^fl/fl) we have demonstrated that CCN6 is a tumor suppressor for MBC; MMTV-cre;Ccn6^fl/fl mice develop tumors recapitulating the histopathology and proteogenomic landscape of human MBC, but the mechanisms need further investigation. In this study, we report that preneoplastic mammary glands of 8-week-old MMTV-Cre;Ccn6^fl/fl female mice show significant downregulation of mitochondrial respiratory chain genes compared to controls, which are further downregulated in MBCs of MMTV-Cre;Ccn6^fl/fl mice and humans. We found that CCN6 downregulation in non-tumorigenic breast cells reduces mitochondrial respiration and increases resistance to stress-induced apoptosis compared to controls. Intracellular ectopic CCN6 protein localizes to the mitochondria in MDA-MB-231 mesenchymal-like breast cancer cells, increases mitochondrial respiration and generation of reactive oxygen species, and reverses doxorubicin resistance of MBC cells. Our data highlight a novel function of CCN6 in the regulation of redox states in preneoplastic progression and suggest potential preventative and treatment strategies against MBC based on CCN6 upregulation.

Inhibition of 2-hydroxyglutarate elicits metabolic reprogramming and mutant IDH1 glioma immunity in mice

Mutant isocitrate dehydrogenase 1 (IDH1-R132H; mIDH1) is a hallmark of adult gliomas. Lower grade mIDH1 gliomas are classified into 2 molecular subgroups: 1p/19q codeletion/TERT-promoter mutations or inactivating mutations in α-thalassemia/mental retardation syndrome X-linked (ATRX) and TP53. This work focuses on glioma subtypes harboring mIDH1, TP53, and ATRX inactivation. IDH1-R132H is a gain-of-function mutation that converts α-ketoglutarate into 2-hydroxyglutarate (D-2HG). The role of D-2HG within the tumor microenvironment of mIDH1/mATRX/mTP53 gliomas remains unexplored. Inhibition of D-2HG, when used as monotherapy or in combination with radiation and temozolomide (IR/TMZ), led to increased median survival (MS) of mIDH1 glioma-bearing mice. Also, D-2HG inhibition elicited anti-mIDH1 glioma immunological memory. In response to D-2HG inhibition, PD-L1 expression levels on mIDH1-glioma cells increased to similar levels as observed in WT-IDH gliomas. Thus, we combined D-2HG inhibition/IR/TMZ with anti-PDL1 immune checkpoint blockade and observed complete tumor regression in 60% of mIDH1 glioma-bearing mice. This combination strategy reduced T cell exhaustion and favored the generation of memory CD8+ T cells. Our findings demonstrate that metabolic reprogramming elicits anti-mIDH1 glioma immunity, leading to increased MS and immunological memory. Our preclinical data support the testing of IDH-R132H inhibitors in combination with IR/TMZ and anti-PDL1 as targeted therapy for mIDH1/mATRX/mTP53 glioma patients.

Cancer Cell Invasion of Mammary Organoids with Basal-In Phenotype

This paper describes mammary organoids with a basal-in phenotype where the basement membrane is located on the interior surface of the organoid. A key materials consideration to induce this basal-in phenotype is the use of a minimal gel scaffold that the epithelial cells self-assemble around and encapsulate. When MDA-MB-231 breast cancer cells are co-cultured with epithelial cells from day 0 under these conditions, cells self-organize into patterns with distinct cancer cell populations both inside and at the periphery of the epithelial organoid. In another type of experiment, the robust formation of the basement membrane on the epithelial organoid interior enables convenient studies of MDA-MB-231 invasion in a tumor progression-relevant direction relative to epithelial cell-basement membrane positioning. That is, the study of cancer invasion through the epithelium first, followed by the basement membrane to the basal side, is realized in an experimentally convenient manner where the cancer cells are simply seeded on the outside of preformed organoids, and their invasion into the organoid is monitored. Interestingly, invasion is more prominent when tumor cells are added to day 7 organoids with less developed basement membranes compared to day 16 organoids with more defined ones.

Subcellular localization of EZH2 phosphorylated at T367 stratifies metaplastic breast carcinoma subtypes

BACKGROUND

Metaplastic carcinoma is an aggressive, triple-negative breast cancer (TNBC) with differentiation towards squamous, spindle, or mesenchymal cell types. The molecular underpinnings of the histological subtypes are unclear. Our lab discovered a cytoplasmic function of EZH2, a transcriptional repressor, whereby pEZH2 T367 binds to cytoplasmic proteins in TNBC cells and enhances invasion and metastasis. Here, we investigated the expression and subcellular localization of pEZH2 T367 protein in metaplastic carcinomas.

METHODS

Thirty-five metaplastic carcinomas (17 squamous, 10 mesenchymal, and 8 spindle) were evaluated and immunostained with anti-pEZH2 T367. We analyzed staining intensity (score 1-4), subcellular localization (nuclear/cytoplasmic), and localization within the tumor (center/invasive edge). Protein expression of pEZH2 T367-binding partners was measured from a quantitative multiplex proteomics analysis performed in our lab.

RESULTS

Cytoplasmic pEZH2 T367 was significantly upregulated in squamous (14 of 17, 82%) compared to mesenchymal (4 of 10, 40%) and spindle (2 of 6, 33%) subtypes (p = 0.011). Twenty-five of 34 (73%) tumors with available tumor-normal interface showed accentuated cytoplasmic pEZH2 T367 at the infiltrative edge. Cytoplasmic pEZH2 T367 was upregulated in 9 of 10 (90%) tumors with lymph node metastasis (p = 0.05). Bioinformatics analyses identified an EZH2 protein network in metaplastic carcinomas (p value: < 1.0e-16). Using quantitative proteomics, we found significantly increased expression of cytoplasmic EZH2-binding partners in squamous compared to spindle and mesenchymal subtypes.

CONCLUSIONS

pEZH2 T367 expression and subcellular localization may be useful to distinguish metaplastic carcinoma subtypes. pEZH2 T367 may play a role in the histological diversity and behavior of these tumors.

Abstract 981: Lymphocytic inflammation is a distinct feature of squamous metaplastic breast carcinomas and is associated with metastasis

Metaplastic breast carcinoma (MBC) is a rare subtype of triple negative breast carcinoma with frequent metastasis and poor response to chemotherapy. MBCs are defined by the presence of “metaplastic” components of spindle, squamous, or sarcomatoid histology (e.g. chondroid, osseous). To elucidate the molecular determinants of MBC, our lab analyzed the proteomics landscape of MBC which revealed that squamous MBC are significantly enriched for proteins that mediate inflammation and leukocyte activation, compared to spindle and sarcomatoid MBC. The presence and the significance of inflammation in MBC has not been investigated. To evaluate this, we retrieved 36 MBCs resected from 1988-2015 at our institution. Tumor sections were reviewed by three pathologists, and used to develop a tissue microarray (TMA) in duplicate. H&E whole sections were reviewed for MBC subtype and inflammation. The inflammatory infiltrate was assessed for type (lymphocytes, plasma cells, neutrophils, macrophages), localization (peripheral and/or intratumoral), and degree (0, 1, 2, 3). When the combined degree of inflammation at the periphery and intratumoral was ≥ 4, the degree was considered high. TMAs were immunostained for CD3/CD20 and CD4/CD8 double stains for further characterization. Of the 36 MBCs, 9 (25%) were chondroid, 7 (20%) were spindled, and 20 (55%) were squamous. When present, inflammation was predominantly lymphoid or lymphoplasmacytic (94%). Seventy-five % (15/20) of squamous MBC demonstrated significantly higher intratumoral inflammation (score ≥2) compared to 43% (3/7) and 11% (1/9) of spindle and chondroid, respectively (p=0.005). Squamous MBCs had a significantly higher degree (peripheral and intratumoral) of inflammation (15/20, 75%) compared to spindled (3/7, 43%) and chondroid (1/9, 11%) MBC's (p=0.004). The inflammatory infiltrate consisted of a mixture of B and T lymphocytes. Ninety-five % of cases with a T-cell infiltrate showed a predominance of CD4+ over CD8+ T-cells. Lymph node metastasis was seen in 11/30 MBC, and 9/11 (81%) demonstrated squamous morphology and a high degree of inflammation (p=0.017). Our results demonstrate that squamous MBC have a higher degree of inflammation within and at the periphery of the tumor compared to other MBC subtypes. A high degree of inflammation consisting of B and T lymphocytes in squamous MBC correlates with lymph node metastasis. The inflammatory infiltrate may contribute to the aggressive clinical behavior of squamous MBC, which warrants further investigation.

Citation Format: Emily McMullen, Stephanie L. Skala, Sabra Djomehri, May P. Chan, Celina G. Kleer. Lymphocytic inflammation is a distinct feature of squamous metaplastic breast carcinomas and is associated with metastasis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 981.

Mesenchymal Stem/Stromal Cell Engulfment Reveals Metastatic Advantage in Breast Cancer

Twenty percent of breast cancer (BC) patients develop distant metastasis for which there is no cure. Mesenchymal stem/stromal cells (MSCs) in the tumor microenvironment were shown to stimulate metastasis, but the mechanisms are unclear. Here, we identified and quantified cancer cells engulfing stromal cells in clinical samples of BC metastasis by dual immunostaining for EZH2 and ALDH1 expression. Using flow cytometry and a microfluidic single-cell paring and retrieval platform, we show that MSC engulfment capacity is associated with BC cell metastatic potential and generates cells with mesenchymal-like, invasion, and stem cell traits. Whole-transcriptome analyses of selectively retrieved engulfing BC cells identify a gene signature of MSC engulfment consisting of WNT5A, MSR1, ELMO1, IL1RL2, ZPLD1, and SIRPB1. These results delineate a mechanism by which MSCs in the tumor microenvironment promote metastasis and provide a microfluidic platform with the potential to predict BC metastasis in clinical samples.

Metaplastic Breast Carcinoma: Update on Histopathology and Molecular Alterations

CONTEXT—

Metaplastic carcinoma is a rare, triple-negative carcinoma of the breast that exhibits transformation of part or all of its glandular carcinomatous component into a nonglandular, or metaplastic, component. The World Health Organization currently recognizes 5 variants of metaplastic carcinoma based on their histologic appearance.

OBJECTIVE—

To review the histologic classifications, differential diagnosis, prognosis, and recent laboratory studies of metaplastic breast carcinoma.

DATA SOURCES.—

We reviewed recently published studies that collectively examine metaplastic carcinomas, including results from our own research.

CONCLUSIONS.—

Metaplastic breast carcinoma has a broad spectrum of histologic patterns, often leading to a broad differential diagnosis. Diagnosis can typically be rendered by a combination of morphology and immunohistochemical staining for high-molecular-weight cytokeratins and p63. Recent studies elucidate new genes and pathways involved in the pathogenesis of metaplastic carcinoma, including the downregulation of CCN6 and WNT pathway gene mutations, and provide a novel MMTV-Cre;Ccn6^fl/fl knockout disease-relevant mouse model to test new therapies.

Androgen Receptor and ALDH1 Expression Among Internationally Diverse Patient Populations

Purpose

Population-based incidence rates of breast cancers that are negative for estrogen receptor (ER), progesterone receptor, and human epidermal growth factor receptor 2/neu (triple-negative breast cancer [TNBC]) are higher among African American (AA) compared with white American (WA) women, and TNBC prevalence is elevated among selected populations of African patients. The extent to which TNBC risk is related to East African versus West African ancestry, and whether these associations extend to expression of other biomarkers, is uncertain.

Methods

We used immunohistochemistry to evaluate estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2/neu, androgen receptor and aldehyde dehydrogenase 1 (ALDH1) expression among WA (n = 153), AA (n = 76), Ethiopian (Eth)/East African (n = 90), and Ghanaian (Gh)/West African (n = 286) patients with breast cancer through an institutional review board–approved international research program.

Results

Mean age at diagnosis was 43, 49, 60, and 57 years for the Eth, Gh, AA, and WA patients, respectively. TNBC frequency was higher for AA and Gh patients (41% and 54%, respectively) compared with WA and Eth patients (23% and 15%, respectively; P < .001) Frequency of ALDH1 positivity was higher for AA and Gh patients (32% and 36%, respectively) compared with WA and Eth patients (23% and 17%, respectively; P = .007). Significant differences were observed for distribution of androgen receptor positivity: 71%, 55%, 42%, and 50% for the WA, AA, Gh, and Eth patients, respectively (P = .008).

Conclusion

Extent of African ancestry seems to be associated with particular breast cancer phenotypes. West African ancestry correlates with increased risk of TNBC and breast cancers that are positive for ALDH1.

Perturbed myoepithelial cell differentiation in BRCA mutation carriers and in ductal carcinoma in situ

Myoepithelial cells play key roles in normal mammary gland development and in limiting pre-invasive to invasive breast tumor progression, yet their differentiation and perturbation in ductal carcinoma in situ (DCIS) are poorly understood. Here, we investigated myoepithelial cells in normal breast tissues of BRCA1 and BRCA2 germline mutation carriers and in non-carrier controls, and in sporadic DCIS. We found that in the normal breast of non-carriers, myoepithelial cells frequently co-express the p63 and TCF7 transcription factors and that p63 and TCF7 show overlapping chromatin peaks associated with differentiated myoepithelium-specific genes. In contrast, in normal breast tissues of BRCA1 mutation carriers the frequency of p63⁺TCF7⁺ myoepithelial cells is significantly decreased and p63 and TCF7 chromatin peaks do not overlap. These myoepithelial perturbations in normal breast tissues of BRCA1 germline mutation carriers may play a role in their higher risk of breast cancer. The fraction of p63⁺TCF7⁺ myoepithelial cells is also significantly decreased in DCIS, which may be associated with invasive progression.

A reproducible scaffold-free 3D organoid model to study neoplastic progression in breast cancer

While 3D cellular models are useful to study biological processes, gel-embedded organoids have large variability. This paper describes high-yield production of large (~1 mm diameter), scaffold-free, highly-spherical organoids in a one drop-one organoid format using MCF10A cells, a non-tumorigenic breast cell line. These organoids display a hollow lumen and secondary acini, and express mammary gland-specific and progenitor markers, resembling normal human breast acini. When subjected to treatment with TGF-β, the hypoxia-mimetic reagent CoCl2, or co-culture with mesenchymal stem/stromal cells (MSC), the organoids increase collagen I production and undergo large phenotypic and morphological changes of neoplastic progression, which were reproducible and quantifiable. Advantages of this scaffold-free, 3D breast organoid model include high consistency and reproducibility, ability to measure cellular collagen I production without noise from exogenous collagen, and capacity to subject the organoid to various stimuli from the microenvironment and exogenous treatments with precise timing without concern of matrix binding. Using this system, we generated organoids from primary metaplastic mammary carcinomas of MMTV-Cre;Ccn6fl/fl mice, which retained the high grade spindle cell morphology of the primary tumors. The platform is envisioned to be useful as a standardized 3D cellular model to study how microenvironmental factors influence breast tumorigenesis, and to potential therapeutics.

Atypical Ductal Lesions of the Breast: Criteria, Significance, and Laboratory Updates

Context.—

Atypical ductal hyperplasia (ADH) is a challenging diagnosis defined by cytologic and architectural features that carries an increased risk of subsequent carcinoma when diagnosed in isolation. In addition, ADH may secondarily involve benign breast lesions, wherein it carries variable clinical significance.

Objectives.—

To review the diagnostic criteria and clinical significance of ADH in isolation and as it involves benign breast lesions, and to review the evolving literature on its molecular signature.

Data Sources.—

Recently published studies that collectively examine ADH were reviewed.

Conclusions.—

Atypical ductal hyperplasia carries an increased risk of subsequent carcinoma in isolation and when it involves most benign breast lesions. Identifying which cases of ADH will be upgraded to carcinoma has been challenging, and new laboratory developments, such as EZH2 overexpression, may have a future role.

CCN6 regulates IGF2BP2 and HMGA2 signaling in metaplastic carcinomas of the breast

PURPOSE

Metaplastic breast carcinomas are an aggressive subtype of triple-negative breast cancer (TNBC) in which part or all of the adenocarcinoma transforms into a non-glandular component (e.g., spindled, squamous, or heterologous). We discovered that mammary-specific Ccn6/Wisp3 knockout mice develop mammary carcinomas with spindle and squamous differentiation that share upregulation of the oncofetal proteins IGF2BP2 (IMP2) and HMGA2 with human metaplastic carcinomas. Here, we investigated the functional relationship between CCN6, IGF2BP2, and HMGA2 proteins in vitro and in vivo, and their expression in human tissue samples.

METHODS

MMTV-cre;Ccn6^fl/fl tumors and spindle TNBC cell lines were treated with recombinant CCN6 protein or vehicle. IGF2BP2 was downregulated using shRNAs in HME cells with stable CCN6 shRNA knockdown, and subjected to invasion and adhesion assays. Thirty-one human metaplastic carcinomas were arrayed in a tissue microarray (TMA) and immunostained for CCN6, IGF2BP2, and HMGA2.

RESULTS

CCN6 regulates IGF2BP2 and HMGA2 protein expression in MMTV-cre;Ccn6^fl/fl tumors, in MDA-MB-231 and - 468, and in HME cells. CCN6 recombinant protein reduced IGF2BP2 and HMGA2 protein expression, and decreased growth of MMTV-cre;Ccn6^fl/fl tumors in vivo. IGF2BP2 shRNA knockdown was sufficient to reverse the invasive abilities conferred by CCN6 knockdown in HME cells. Analyses of the TCGA Breast Cancer Cohort (n = 1238) showed that IGF2BP2 and HMGA2 are significantly upregulated in metaplastic carcinoma compared to other breast cancer subtypes. In clinical samples, low CCN6 is frequent in tumors with high IGF2BP2/HMGA2 with spindle and squamous differentiation.

CONCLUSIONS

These data shed light into the pathogenesis of metaplastic carcinoma and demonstrate a novel CCN6/IGF2BP2/HMGA2 oncogenic pathway with biomarker and therapeutic implications.

p38-mediated phosphorylation at T367 induces EZH2 cytoplasmic localization to promote breast cancer metastasis

Overexpression of EZH2 in estrogen receptor negative (ER-) breast cancer promotes metastasis. EZH2 has been mainly studied as the catalytic component of the Polycomb Repressive Complex 2 (PRC2) that mediates gene repression by trimethylating histone H3 at lysine 27 (H3K27me3). However, how EZH2 drives metastasis despite the low H3K27me3 levels observed in ER- breast cancer is unknown. Here we show that in human invasive carcinomas and distant metastases, cytoplasmic EZH2 phosphorylated at T367 is significantly associated with ER- disease and low H3K27me3 levels. p38-mediated EZH2 phosphorylation at T367 promotes EZH2 cytoplasmic localization and potentiates EZH2 binding to vinculin and other cytoskeletal regulators of cell migration and invasion. Ectopic expression of a phospho-deficient T367A-EZH2 mutant is sufficient to inhibit EZH2 cytoplasmic expression, disrupt binding to cytoskeletal regulators, and reduce EZH2-mediated adhesion, migration, invasion, and development of spontaneous metastasis. These results point to a PRC2-independent non-canonical mechanism of EZH2 pro-metastatic function.

Abstract 4219: Breast cancer distribution and survival among Buddhist and Muslim women in southern Thailand

Objective: Thailand is undergoing a period of rapid economic growth, which has led to an epidemiologic transition from infectious to chronic diseases such as cancer. Preliminary research shows a difference in rates of breast cancer incidence and mortality between Buddhist and Muslim women in southern Thailand. This study examines differences in breast cancer and potential explanations for this disparity. Methods: Demographic, diagnostic, and outcome data from breast cancer patients diagnosed from 2001-2015 were collected from a population-based cancer registry in southern Thailand and matched with formalin-fixed paraffin-embedded blocks from Songklanagarind Hospital. This region was selected due to the relatively high proportion of Muslim women. Of 424 cases selected, 369 were Buddhist and 55 were Muslim. Formalin-fixed paraffin-embedded blocks were sent to Michigan Medicine and histological and subtype analyses were performed by two pathologists. Statistical analysis was performed in RStudio using chi-square tests of independence, logistic regression, and Cox proportional hazards models. Results: Muslim women were generally diagnosed at a younger age than Buddhist women (Muslim mean: 46.6 years, Buddhist mean: 52.7 years) and with later stage cancers (Muslim: 36% stage 3 and 14% stage 4, Buddhist: 20% stage 3 and 8% stage 4). Buddhist and Muslim women had similar distributions of Luminal A and B subtypes, but Muslim women were more likely to be diagnosed with Triple Negative breast cancer (Muslim: 30%, Buddhist: 18%), the histological subtype with the worst prognosis. Invasive ductal carcinoma was most common in both groups, but Buddhists had more heterogeneity in subtypes. There were no significant differences in tumor histology or subtype by religion. Conclusions: These analyses show differences in the distribution of breast cancer between Buddhist and Muslim women. Muslim women are diagnosed younger with later stage breast cancers, and with histological differences, which generally lead to lower survival rates. Lack of statistical significance may be due to small sample size, necessitating further studies.

Citation Format: Kali Defever, Katie M. Rentschler, Ana Khazan, Elizabeth Pinkerton, Shama Virani, Hutcha Sriplung, Judy Pang, Celina G. Kleer, Carlos F. Mendes de Leon, Justin A. Colacino, Laura S. Rozek. Breast cancer distribution and survival among Buddhist and Muslim women in southern Thailand [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4219.

Ethnic disparity in breast cancer survival in southern Thai women

BACKGROUND

Breast cancer has the highest incidence in women of all cancers and its burden is expected to continue to increase worldwide, especially in middle-income countries such as Thailand. The southern region of Thailand is unique in that it is comprised of 30% Muslims, whereas the rest of Thailand is 95% Buddhist. Breast cancer incidence and survival differ between these religious groups, but the association between clinical subtype of breast cancer and survival has not yet been assessed.

METHODS

Here we characterized differences in breast cancer survival with consideration to clinical subtype by religious group (Muslim Thai and Buddhist Thai women). We compared distributions of age, stage and clinical subtype and assessed overall survival by religion.

RESULTS

Our findings show that Muslim Thai women with breast cancer are diagnosed at a younger age, at later stages and have shorter overall survival times compared to Buddhist Thai women with breast cancer. We also observe a higher proportion of triple negative tumors characterized in Muslim Thai women.

CONCLUSIONS

Our findings confirm previous studies that have shown lower survival rates in Muslim Thai women compared to Buddhist women with breast cancer and offer novel information on subtype distribution. To date, this is the first study assessing clinical subtypes in southern Thailand by religious status.

IMPACT

Our findings are critical in providing information on the role of clinical subtype in cancer disparities and provide evidence from the Southeast Asian region for global studies on breast cancer survival.

Mesenchymal Stem Cell-Induced DDR2 Mediates Stromal-Breast Cancer Interactions and Metastasis Growth

Increased collagen deposition by breast cancer (BC)-associated mesenchymal stem/multipotent stromal cells (MSC) promotes metastasis, but the mechanisms are unknown. Here, we report that the collagen receptor discoidin domain receptor 2 (DDR2) is essential for stromal-BC communication. In human BC metastasis, DDR2 is concordantly upregulated in metastatic cancer and multipotent mesenchymal stromal cells. In MSCs isolated from human BC metastasis, DDR2 maintains a fibroblastic phenotype with collagen deposition and induces pathological activation of DDR2 signaling in BC cells. Loss of DDR2 in MSCs impairs their ability to promote DDR2 phosphorylation in BC cells, as well as BC cell alignment, migration, and metastasis. Female ddr2-deficient mice homozygous for the slie mutation show inefficient spontaneous BC metastasis. These results point to a role for mesenchymal stem cell DDR2 in metastasis and suggest a therapeutic approach for metastatic BC.

Phyllodes Tumor of the Breast: Histopathologic Features, Differential Diagnosis, and Molecular/Genetic Updates

CONTEXT

-Phyllodes tumor (PT) of the breast is a rare fibroepithelial neoplasm with risks of local recurrence and uncommon metastases. The classification proposed by the World Health Organization for PTs into benign, borderline, and malignant is based on a combination of several histologic features. The differential diagnosis between PT and fibroadenoma and the histologic grading of PT remain challenging. In addition, the molecular pathogenesis of PT is largely unknown.

OBJECTIVE

-To provide an updated overview of pathologic features, diagnostic terminology, and molecular alterations of PT.

DATA SOURCES

-Current English literature related to PT of the breast.

CONCLUSIONS

-Phyllodes tumor shows a wide spectrum of morphology. There are no clearly distinct boundaries between PT and fibroadenoma. Strict histologic assessment of a combination of histologic features with classification can help to achieve the correct diagnosis and provide useful clinical information. The genomic landscapes of PT generated from genomic sequencing provide insights into the molecular pathogenesis of PT and help to improve diagnostic accuracy and identify potential drug targets in malignant PT.

Abstract P4-03-03: Microenvironment induced DDR2 mediates stromal-cancer interactions and metastasis growth in breast cancer

This abstract was not presented at the symposium.

Atypical Apocrine Adenosis: Diagnostic Challenges and Pitfalls

Apocrine change in the breast is an extremely common finding. In most cases, the benign or malignant nature of the lesion is easily recognized. Apocrine adenosis is used to describe sclerosing adenosis with apocrine change. The term apocrine atypia is used when there is significant cytologic atypia in apocrine cells, characterized by a 3-fold nuclear enlargement, prominent/multiple nucleoli, and hyperchromasia. Atypical apocrine adenosis is diagnosed when apocrine adenosis and apocrine atypia are superimposed. However, there are no definite criteria to distinguish atypical apocrine adenosis from apocrine ductal carcinoma in situ. Immunohistochemical markers can be confounding and may lead to erroneous diagnoses. Atypical apocrine features in sclerosing lesions may be misinterpreted as invasive carcinoma if the underlying lesion is not recognized. In the absence of definite features of malignancy, the diagnosis of apocrine ductal carcinoma in situ may be extremely difficult. In the present article, we review atypical apocrine adenosis focusing on diagnostic challenges and their implications on clinical management.

ESR1 and PGR polymorphisms are associated with estrogen and progesterone receptor expression in breast tumors

Hormone receptor-positive (HR+) breast cancers express the estrogen (ERα) and/or progesterone (PgR) receptors. Inherited single nucleotide polymorphisms (SNPs) in ESR1, the gene encoding ERα, have been reported to predict tamoxifen effectiveness. We hypothesized that these associations could be attributed to altered tumor gene/protein expression of ESR1/ERα and that SNPs in the PGR gene predict tumor PGR/PgR expression. Formalin-fixed paraffin-embedded breast cancer tumor specimens were analyzed for ESR1 and PGR gene transcript expression by the reverse transcription polymerase chain reaction based Oncotype DX assay and for ERα and PgR protein expression by immunohistochemistry (IHC) and an automated quantitative immunofluorescence assay (AQUA). Germline genotypes for SNPs in ESR1 (n = 41) and PGR (n = 8) were determined by allele-specific TaqMan assays. One SNP in ESR1 (rs9322336) was significantly associated with ESR1 gene transcript expression (P = 0.006) but not ERα protein expression (P > 0.05). A PGR SNP (rs518162) was associated with decreased PGR gene transcript expression (P = 0.003) and PgR protein expression measured by IHC (P = 0.016), but not AQUA (P = 0.054). There were modest, but statistically significant correlations between gene and protein expression for ESR1/ERα and PGR/PgR and for protein expression measured by IHC and AQUA (Pearson correlation = 0.32-0.64, all P < 0.001). Inherited ESR1 and PGR genotypes may affect tumor ESR1/ERα and PGR/PgR expression, respectively, which are moderately correlated. This work supports further research into germline predictors of tumor characteristics and treatment effectiveness, which may someday inform selection of hormonal treatments for patients with HR+ breast cancer.

Abstract 4481: Phosphorylation regulates EZH2 neoplastic functions in triple-negative breast cancer

Background: Triple negative (estrogen receptor, progesterone receptor, HER2-neu negative) breast cancers (TNBC) comprise 15% of all breast cancers but are responsible for a disproportionately high number of deaths. Overexpression of the histone methyltransferase EZH2 (Enhancer of Zeste Homolog 2) is an independent prognostic biomarker significantly associated with poorly-differentiated TNBCs and poor patient outcome. We previously identified a novel link between EZH2 and the p38 mitogen-activated protein kinase, an important mediator of progression and metastasis of TNBC. We found that EZH2 binds to p38, and that EZH2 and activated p38 are concordantly expressed in the metastases of breast cancer patients. Based on these data and previous in vitro studies, we hypothesized that p38 MAPK may also regulate EZH2 through phosphorylation in breast cancer. We further hypothesized that this phosphorylation event may be important for EZH2 contribution to malignancy.

Methods: In order to test this hypothesis, we performed knockdown rescue experiments in triple-negative breast cancer cell lines MDA-MB-231 and MDA-MB-436. Stable knockdown of EZH2 was achieved using shRNA targeting the 3’UTR. Knockdown of EZH2 was rescued by reintroduction of myc-EZH2 (WT) or a T367A-EZH2 phosphorylation-deficient mutant. Cell lines were then used in functional assays of proliferation, migration, and invasion. In order to further interrogate the importance of this phosphorylation event, we developed a phospho-specific EZH2 T367 antibody.

Results: p38-mediated phosphorylation of EZH2 at T367 contributes to the migratory and invasive properties of TNBC. Mechanistically, phosphorylation by p38 does not affect binding to other PRC2 members but may affect EZH2 activity. We are currently investigating the relevance of pEZH2 as a biomarker of breast cancer survival with our new antibody.

Conclusions: We provide evidence that p38 phosphorylation of EZH2 at T367 contributes to malignancy of triple-negative breast cancers. Our data suggest a new mechanism by which EZH2 is regulated and may offer an additional mechanism by which EZH2 contributes to TNBC progression.

Citation Format: Talha Anwar, Caroline Arellano-Garcia, Boris Burman, Celina G. Kleer. Phosphorylation regulates EZH2 neoplastic functions in triple-negative breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4481.

Abstract 4397: Mesenchymal stem cell-derived collagen I plays a role in organizing breast cancer cell migration and metastasis

Background: Accumulating evidence suggests that mesenchymal stem cells (MSCs) are recruited to the tumor microenvironment and play roles in tumor progression; however the underlying mechanisms by which MSCs promote breast cancer migration and invasion need further investigation. Studies have demonstrated that collagen plays an important role in breast tumorigenesis by activating signaling pathways. We hypothesize that MSCs may promote breast cancer progression through regulating collagen-induced signaling in breast cancer cells.

Methods: We isolated carcinoma-associated MSCs (CA-MSCs) from human breast cancer metastasis to lymph node (LNM) and liver (LM). CA-MSCs were subjected to multilineage differentiation assays and labeled with Ds-Red. COAL I expression and its receptor discoidin domain receptor 2 (DDR2) were downregulated in the CA-MSCs-DsRED using specific shRNA. We established single culture and co-cultures of CA-MSCs with GFP labeled breast cancer cells (BCCs) MDA-MB-231 and MCF10ACA1a which were used for Live Imaging Microscopy, IHC, RT-PCR, WB, immunofluorescence, 3D proliferation and invasion assays, and in vivo xenograft experiments.

Results: CA-MSCs had spindle morphology, normal karyotype, were nontumorigenic in vivo, and possessed tri-lineage differentiation ability (osteoblast, adipocyte, and chondrocyte). CA-MSCs exhibited high mRNA and protein levels of collagen I (COAL I) and its receptor DDR2. ShRNA-mediated knockdown of COAL I or DDR2 in CA-MSCs induced a change in morphology towards epithelial, decreased expression of epithelial to mesenchymal transition (EMT) markers, and impaired migration. Co-culture of CA-MSCs with BCCs led to increased BCC proliferation, EMT, invasion, and increased DDR2 expression in BCCs compared to single cultures of BCCs, which was blocked by COAL1 and DDR2 shRNA in CA-MSCs. Live imaging studies revealed that shCOAL1 and shDDR2 was sufficient to completely disrupt the organized migration pattern of BCCs aligned with CA-MSCs. In vivo, xenografts derived from MDA-MB-231 cells co-cultured with shControl CA-MSCs exhibited increased collagen I deposition in the tumor microenvironment, increased tumor growth, and metastasis compared to the single cultures of MDA-MB-231 cells. Remarkably, shDDR2 in CA-MSCs reduced tumorigenesis and metastasis.

Conclusion: We successfully isolated and characterized CA-MSCs, confirming their presence in human breast cancer metastasis. Our findings suggest that collagen I and its receptor DDR2 play a role in directional migration of breast cancer cells in alignment with CA-MSCs, a function that may be implicated in breast cancer invasion and metastasis. Downregulation of collagen I expression and signaling reduces tumor growth and metastasis in vivo. Modifying tumor microenvironment by manipulating collagen I and/or DDR2 levels in MSCs might be therapeutically useful in preventing metastasis.

Citation Format: Maria E. Gonzalez, Emily Martin, Caroline Arellano-Gracia, Arjun Lama, Celina G. Kleer. Mesenchymal stem cell-derived collagen I plays a role in organizing breast cancer cell migration and metastasis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4397.

Chronic Mastitis in Egypt and Morocco: Differentiating between Idiopathic Granulomatous Mastitis and IgG4-Related Disease

Idiopathic granulomatous mastitis (IGM) is a benign, frequently severe chronic inflammatory lesion of the breast. Its etiology remains unknown and reported cases vary in their presentation and histologic findings with an optimal treatment algorithm yet to be described owing mainly to the disease's heterogeneity. IgG4‐related disease (IgG4‐RD) is a newly recognized systemic fibroinflammatory condition characterized by a dense lymphoplasmacytic infiltrate with many IgG4‐positive plasma cells, storiform fibrosis, and obliterative phlebitis. Immunosuppressive therapy is considered to be an effective first‐line therapy for IgG4‐RD. We sought to clarify and classify chronic mastitis according to the histologic findings of IgG4‐RD mastitis with respect to IGM and to develop a robust diagnostic framework to help select patients for optimal treatment strategies. Using the largest collection to date (43 cases from Egypt and Morocco), we show that despite sharing many features, IGM and IgG4‐RD mastitis are separate diseases. To diagnostically separate the diseases, we created a classification schema—termed the Michigan Classification—based upon our large series of cases, the consensus statement on IgG4‐RD, and the histologic description of IGM in the literature. Using our classification, we discerned 17 cases of IgG4‐RD and 8 cases of IGM among the 43 chronic mastitis cases, with 18 indeterminate cases. Thus, our Michigan Classification can form the basis of rational stratification of chronic mastitis patients between these two clinically and histopathologically heterogeneous diseases.

Abstract 2895: Phosphorylation of EZH2 at T416 by CDK2 promotes development of mammary tumors with basal-like phenotype

Basal-like breast cancer, also referred to as triple negative breast cancer (TNBC) due to the lack of expression of ErbB2, PR, and ER alpha receptors, is considered to be one of the most aggressive breast cancers, which display high rates of tumor cell proliferation, metastasis, and post-surgical re-occurrence. This subtype of breast cancer presents a major challenge for breast cancer oncologists as currently there is no effective therapy available. Here, we show that Cyclin E and EZH2, the methyltransferase component of the polycomb repressive complex 2 (PRC2) are exclusively co-expressed in TNBC tumor tissues. We further show that CDK2, the only known enzymatic partner of Cyclin E, can phosphorylate EZH2 at T416 in vivo. CDK2-mediated modification of EZH2 at T416 leads to gain-of-function, enhancing its ability to promote breast cancer cell migration/invasion, expansion and self-renewal of tumor sphere in vitro, and tumor growth in vivo. In addition, our immunohistochemistry-staining of 247 primary breast tumor tissues validates that high EZH2/T416 phosphorylation correlates with poor survival in TNBC but not in non-TNBC patients. To further attest the oncogenic role of EZH2/T416 phosphorylation by CDK2 in vivo, we generated transgenic mice expressing EZH2T416D mutant, a mimicking phosphorylated form of EZH2, in mammary glands. In contrast to previously reported EZH2WT transgenic mice, which did not develop mammary tumors, our EZH2T416D-expressing mice developed malignant mammary tumor with basal-like and highly metastatic potential phenotypes. These genetic evidence revealed that CDK2/Cyclin E mediated site-specific phosphorylation of EZH2 is capable of inducing the basal-like/TNBC phenotype and maintaining cancer stem cell population of breast cancers so that the T416 phosphorylation of EZH2 might serve as a biomarker for TNBC prognosis and effective therapy.

Citation Format: Lei Nie, Yongkun Wei, Adam LaBaff, Cheng-Chieh Yang, Weiya Xia, Longfei Huo, Dongping Liu, Yi-Hsin Hsu, Gabriel N. Hortobagyi, Jun Yao, Celina G. Kleer, Mien-Chie Hung. Phosphorylation of EZH2 at T416 by CDK2 promotes development of mammary tumors with basal-like phenotype. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2895. doi:10.1158/1538-7445.AM2015-2895

Abstract 4188: Conditional epithelial cell-specific knockout of CCN6/Wisp3 disrupts normal development of the virgin murine mammary gland

Background: Breast cancer remains one of the top causes of morbidity and mortality among cancer patients in the U.S. Inflammatory breast cancer (IBC) is the most lethal form of locally advanced breast cancer. Our laboratory has shown that CCN6/Wisp3, a secreted extracellular matrix-associated protein which belongs to the CCN family, is lost in 80% of IBC compared to stage-matched non-IBC tumors. We have shown previously that CCN6 knockdown in benign human breast cells leads to an epithelial-to-mesenchymal transition and increased resistance to anoikis. Further, CCN6 overexpression in breast cancer cells reduces invasion and growth in vivo and in vitro. However, the consequences of CCN6 knockout in the mammary gland have never been explored. We hypothesized that the conditional deletion of CCN6 in mammary epithelial cells in mice may lead to defects in mammary gland development and may induce mammary tumors.

Methods: We created a novel transgenic mouse model in which CCN6 is conditionally knocked out in mammary epithelial cells using the Cre-Lox recombination system. We collected groups of CCN6 knockout mice and littermate controls at 8 weeks, 4 months, and 12 months of age to observe the effect of CCN6 knockout on the development of the virgin mammary gland and on de novo tumor formation in aged mice. We also collected groups of CCN6 knockout and control mice at early pregnancy, late pregnancy, lactation and involution timepoints. Mammary whole mounts were prepared in order to characterize the phenotype, and portions of the inguinal gland were collected for immunohistochemical, protein and RNA analysis.

Results: Conditional CCN6 knockout in the murine mammary gland results in defective mammary gland development in pubertal (8-week-old) and post-pubertal (4-month-old) virgin female mice compared to controls. At 8 weeks of age, virgin CCN6 knockout mice exhibit significantly fewer terminal end buds and fewer bifurcated terminal end buds. At 4 months of age, virgin CCN6 knockout mice have fewer lobuloalveolar units and a hypobranching phenotype compared to controls. We observed no phenotypic differences in the pregnancy and lactation timepoints between CCN6 knockout mice and controls, and no differences in pup weight or average litter size, suggesting that CCN6 is not critical for pregnancy and lactation. CCN6 knockout did not lead to spontaneous tumorigenesis in aged mice.

Conclusion: We provide new evidence that CCN6 is an important signaling molecule in the mammary gland in vivo, as CCN6 is necessary for normal mammary development in virginal animals. We are currently analyzing the effects of CCN6 knockout in mammary gland involution after lactation, and the signaling pathways affected by CCN6 knockout in vivo. Further studies are needed to investigate effect of CCN6 knockout in breast cancer in vivo; to this end, we are currently crossing our CCN6 knockout line with the oncogenic MMTV-Pymt transgenic line.

Citation Format: Emily E. Martin, Wei Huang, Jun-Lin Guan, Celina G. Kleer. Conditional epithelial cell-specific knockout of CCN6/Wisp3 disrupts normal development of the virgin murine mammary gland. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4188. doi:10.1158/1538-7445.AM2015-4188

Abstract 5078: Human breast carcinoma-associated mesenchymal stem cells promote breast cancer cell proliferation, irreversible EMT and invasion through Collagen I

Background: Accumulating evidence suggests that mesenchymal stem cells (MSCs) are recruited to the tumor microenvironment and play roles in tumor progression; however their specific mechanisms and functions need further investigation. In this study, we identified the presence of carcinoma-associated MSCs (CA-MSCs) isolated from breast cancer metastasis to a human lymph node (LNM) and liver (LM). We hypothesized that CA-MSCs may increase the invasive abilities of breast cancer cells and that they may enhance collagen expression to promote breast cancer progression.

Methods: We isolated CA-MSCs from fresh samples of breast cancer metastasis to a lymph node and liver obtained from the operating room. A portion of each specimen was subjected to H&E staining to confirm the diagnosis, and another portion was mechanically dissected and digested with collagenase. Red blood cells were lysed with ACK buffer and cell suspensions were cultured in Human Epithelial Medium. Once isolated, adherent CA-MSCs were subcultured in MSC medium for up to 12 passages for each experiment. CA-MSCs were subjected to multilineage differentiation assays (osteogenic, chrodrogenic, and adipogenic differentiation), and labeled with Ds-Red and co-cultured with a panel of breast cancer cells including MDA-MB-231, MCF7, DCIS.COM. We performed RT-PCR, WB, 3D proliferation assays, and invasion assays, and immunoshistochemistry. COAL1 expression was downregulated in the CA-MSCs-DsRED using specific shRNA. Control and CA-MSCs-DsRed-shCOAL1 were co-cultured with MDA-MB-231 and MCF7 breast cancer cells, and subjected to proliferation and invasion assays, and to RT-PCR and WB to investigate EMT proteins.

Results: CA-MSCs had spindle morphology, normal karyotype, were nontumorigenic, and possessed tri-lineage differentiation ability (osteoblast, adipocyte, and chondrocyte). In co-cultures, CA-MSCs promote proliferation, invasion, irreversible EMT through serial passages, compared to single cultures of breast cancer cells. CA-MSCs increased COAL1 expression and collagen 1 deposition in the 3D co-cultures by IHC and RT-PCR. COAL1 shRNA knockdown in CA-MSCs rescued the effect in proliferation and invasion of breast cancer cells in the co-cultures.

Conclusion: We successfully isolated and characterized CA-MSCs, confirming their presence in human breast cancer metastasis. We found that CA-MSCs enhance breast cancer cell proliferation, promote irreversible EMT and invasion and increased COAL1 expression and collagen 1 deposition. We demonstrated that COAL1 expression is required for the effect of CA-MSCs on breast cancer cell proliferation and invasion.

Citation Format: Maria E. Gonzalez, Emily E. Martin, Celina G. Kleer. Human breast carcinoma-associated mesenchymal stem cells promote breast cancer cell proliferation, irreversible EMT and invasion through Collagen I. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5078. doi:10.1158/1538-7445.AM2015-5078

Phosphorylation of EZH2 at T416 by CDK2 contributes to the malignancy of triple negative breast cancers

Triple-negative breast cancer (TNBC), which is closely related to basal-like breast cancer, is a highly aggressive subtype of breast cancer that initially responds to chemotherapy but eventually develops resistance. This presents a major clinical challenge as there are currently no effective targeted therapies available due to its lack of HER2 and estrogen receptor expression. Here, we show that cyclin E and the enhancer of zeste 2 (EZH2) are closely co-expressed in TNBC patients, and cyclin E/CDK2 phosphorylates EZH2 at T416 (pT416-EZH2) in vivo. Phosphorylation of EZH2 at T416 enhances the ability of EZH2 to promote TNBC cell migration/invasion, tumorsphere formation, and in vivo tumor growth. In addition, high pT416-EZH2 correlates with poorer survival in TNBC patients. These findings suggest that pT416 has the potential to serve as a therapeutic biomarker for the aggressive forms of breast cancer and provide a rationale for the use of CDK2 inhibitors to treat TNBC.

Tyrosine kinase discoidin domain receptors DDR1 and DDR2 are coordinately deregulated in triple-negative breast cancer

Receptor kinases Discoidin Domain Receptors (DDRs) 1 and 2 are emerging as new therapeutic targets in breast cancer (BC). However, the expression of DDR proteins during BC progression and their association with BC subtypes remain poorly defined. Herein we report the first comprehensive immunohistochemical analyses of DDR protein expression in a wide range of breast tissues. DDR1 and DDR2 expression was investigated by immunohistochemistry in 218 samples of normal breast (n = 10), ductal carcinoma in situ (DCIS, n = 10), and invasive carcinomas (n = 198), arrayed in tissue microarrays with comprehensive clinical and follow-up information. Staining was evaluated for cell type, subcellular localization, percentage and intensity (scores 1-4), and association with disease subtype and outcome. In normal epithelium and DCIS, DDR1 was highly expressed, while DDR2 was negative in normal epithelium, and in DCIS it localized to cells at the epithelial-stromal interface. Of the 198 invasive carcinomas, DDR1 was high in 87 (44 %) and low in 103 (52 %), and DDR2 was high in 110 (56 %) and low in 87 (44 %). High DDR2 was associated with high tumor grade (P = 0.002), triple-negative subtype (TNBC) (P < 0.0001), and worse survival (P = 0.037). We discovered a novel concordant deregulation of DDR expression, with a DDR1(Low)/DDR2(High) profile significantly associated with TNBC, compared to luminal tumors (P = 0.012), and with worse overall survival. In conclusion, DDR2 upregulation occurs in DCIS, before stromal invasion, and may reflect epithelial-stromal cross-talk. A DDR1(Low)/DDR2(High) protein profile is associated with TNBC and may identify invasive carcinomas with worse prognosis.

Next-Gen Sequencing Exposes Frequent MED12 Mutations and Actionable Therapeutic Targets in Phyllodes Tumors

Phyllodes tumors are rare fibroepithelial tumors with variable clinical behavior accounting for a small subset of all breast neoplasms, yet little is known about the genetic alterations that drive tumor initiation and/or progression. Here, targeted next-generation sequencing (NGS) was used to identify somatic alterations in formalin-fixed paraffin-embedded (FFPE) patient specimens from malignant, borderline, and benign cases. NGS revealed mutations in mediator complex subunit 12 (MED12) affecting the G44 hotspot residue in the majority (67%) of cases spanning all three histologic grades. In addition, loss-of-function mutations in p53 (TP53) as well as deleterious mutations in the tumor suppressors retinoblastoma (RB1) and neurofibromin 1 (NF1) were identified exclusively in malignant tumors. High-level copy-number alterations (CNA) were nearly exclusively confined to malignant tumors, including potentially clinically actionable gene amplifications in IGF1R and EGFR. Taken together, this study defines the genomic landscape underlying phyllodes tumor development, suggests potential molecular correlates to histologic grade, expands the spectrum of human tumors with frequent recurrent MED12 mutations, and identifies IGF1R and EGFR as potential therapeutic targets in malignant cases.

IMPLICATIONS

Integrated genomic sequencing and mutational profiling provides insight into the molecular origin of phyllodes tumors and indicates potential druggable targets in malignant disease. Visual Overview: http://mcr.aacrjournals.org/content/early/2015/04/02/1541-7786.MCR-14-0578/F1.large.jpg.

Abstract 1037: WISP3/CCN6 regulates epithelial-mesenchymal transition and tumor initiating cell properties in triple negative breast cancer cells through Slug

Background: Although triple-negative breast cancers (TNBCs) constitute 10%-20% of all breast cancers, they are aggressive tumors with higher recurrence and poorer prognosis than other breast cancer subtypes. TNBCs frequently exhibit features of epithelial to mesenchymal transition (EMT) and are enriched in breast tumor initiating cells (BTICs). Recent studies have demonstrated that aberrant activation of the EMT program induces stem cell features in breast cells, suggesting that blocking the cross-talk between EMT and stemness may be an effective treatment for TNBCs. WISP3/CCN6, a secreted matrix associated protein, is expressed in normal breast tissues and is decreased in aggressive breast cancer samples. We have shown that CCN6 knockdown in nontumorigenic breast cells triggers EMT and invasion. We hypothesize that CCN6 regulates the cross-talk between EMT and BTICs pathways in TNBCs.

Methods: We overexpressed CCN6 in the TNBC cell lines, MDA-MB-231, SUM-159 and MDA-MB-436, which are aggressive and exhibit a mesenchymal-like phenotype and low endogenous CCN6 expression. We tested the effect of CCN6 overexpression in these cell lines using motility and invasion assays in vitro. Stem cell features were investigated by mammosphere assays, and the ALDEFLUOR assay by flow cytometry. We developed mammary xenografts in nude mice using serial dilutions to investigate the role of CCN6 in tumor initiation and metastasis.

Results: Overexpression of CCN6 inhibits cell motility and invasion, and leads to phenotypic changes of mesenchymal-epithelial transition (MET), with downregulation of the mesenchymal cell marker vimentin, increased epithelial marker cytokeratin, and decreased protein levels of the EMT transcription factor Slug. CCN6 overexpression significantly decreased the ALDEFLUOR-positive population and mammosphere formation of TNBC cell lines. In vivo, CCN6 overexpression delayed tumor initiation and reduced metastasis in human breast cancer xenografts. Slug reconstitution was sufficient to rescue the effects of CCN6 on MET and stem cell properties of TNBCs.

Conclusions: These data demonstrate that CCN6 regulates EMT and tumor initiating cell features in TNBC at least in part through Slug. Further, our study suggests that CCN6 may be a novel regulator of the EMT-stem cell cross talk in TNBC, with possible clinical application.

Citation Format: Wei Huang, Kathy A. Toy, Celina G. Kleer. WISP3/CCN6 regulates epithelial-mesenchymal transition and tumor initiating cell properties in triple negative breast cancer cells through Slug. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1037. doi:10.1158/1538-7445.AM2014-1037

Abstract 4802: Human breast carcinoma-associated mesenchymal stem cells from primary breast cancer metastasis promote proliferation, invasion and mammosphere formation in breast cancer

Background: Accumulating evidence suggests that mesenchymal stem cells (MSCs) are recruited to the tumor microenvironment; however controversy exists regarding their role in solid tumors. In this study, we identified the presence of carcinoma-associated MSCs (CA-MSCs) isolated from breast cancer metastasis to a human lymph node (LNM) and liver (LM).

Methods: Tissue harvesting and culture: CA-MSCs were isolated from fresh samples of lymph nodes and liver breast cancer metastasis obtained from the operating room. A portion of each specimen was mechanically dissected and digested with collagenase. Red cells were lysed with ACK buffer and cell suspensions were cultured in Human Epithelial Medium and isolated adherent CA-MSCs were subculture in MSC medium for up to 12 passages for each experiment. Another portion of the tumor samples were subjected to IHC for H&E staining.

Differentiation assays: For bone differentiation cells were plated in StemPro Osteogenesis differentiation or control medium and allowed to grow for 14 days, and then washed and stained with Alizarin Red S.

For cartilage differentiation cells were pelleted and grown in 15 ml tubes for 21 days, immobilized in histogel and stained with Alizarin Blue.

For adipose differentiation cells were plated in StemCell differentiation and control medium, after 21 days the cells were stained with 0.3% Oil Red O.

Proliferation, invasion, mammosphere assays, cytokine array and RT-PCR for EMT signature were performed seeding the same number of cells and comparing the single culture of CA-MSCs with co-culture of CA-MSCs and a panel of breast cancer cells lines

Results: CA-MSCs had spindle morphology, normal karyotype, were nontumorigenic, and possessed tri-lineage differentiation ability (osteoblast, adipocyte, and chondrocyte). When co-cultured with breast cancer cells, CA-MSCs promoted proliferation, invasion, and mammosphere formation, increased IL6 and IL8 secretion into the media, and induced a gene expression profile of EMT when compared to the single cultures.

Conclusion: We successfully isolated and characterized CA-MSCs, confirming their presence in human breast metastasis. We found that they provide a favorable microenvironment for tumor cell growth, enhance mammosphere formation, and promote an EMT signature and invasion in breast cancer cells.

Citation Format: Maria E. Gonzalez, Kathy A. Toy, Celina G. Kleer. Human breast carcinoma-associated mesenchymal stem cells from primary breast cancer metastasis promote proliferation, invasion and mammosphere formation in breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4802. doi:10.1158/1538-7445.AM2014-4802

Characterization of type III TGF-β receptor expression in invasive breast carcinomas: a potential new marker and target for triple negative breast cancer

Invasive breast carcinomas are heterogeneous and exhibit distinct molecular features and biological behavior. Understanding the underlying molecular events that promote breast cancer progression is necessary to improve treatment and prognostication. TGF-β receptor III (TBR3) is a member of the TGF-β signaling pathway, with functions in cell proliferation and migration in malignancies, including breast cancer. Recent studies propose that TBR3 may function as a tumor suppressor and that its loss may correlate with disease progression. However, there are limited data on the expression of TBR3 in breast cancer in relationship to tumor type, hormonal receptor status and HER-2/neu, and patient outcome. In this study, we investigated the expression of TBR3 in a cohort of 205 primary invasive breast carcinomas in tissue microarrays (TMAs), with comprehensive clinical, pathological and follow- up information. Sections were stained for TBR3 and evaluated for intensity of reactivity based on a 4-tiered scoring system (1 to 4; TBR3 low = scores 1-2; TBR3 high = scores 3-4). Of the 205 invasive carcinomas, 123 were luminal type (95 type A, 28 type B), 8 were HER-2 type, and 62 were triple negative (TN). TBR3 was high in 112 (55 %) and low in 93 (45 %) cases. Low TBR3 was associated with higher histological grade and worse disease free and overall survival, all features of biologically aggressive breast carcinomas. TBR3 was significantly associated with the subtype of breast cancer, as low TBR3 was detected in 95 % of TN compared to 22 % of luminal tumors (p < 0.0001). We discovered a significant association between low TBR3 protein expression, TN breast cancer phenotype, and disease progression. These data suggest that TBR3 loss might be linked to the development of TN breast cancers and pave the way to investigating whether restoring TBR3 function may be a therapeutic strategy against TN breast carcinomas.

Re-excision rates of invasive ductal carcinoma with lobular features compared with invasive ductal carcinomas and invasive lobular carcinomas of the breast

BACKGROUND

Invasive ductal carcinoma (IDC) with lobular features (IDC-L) is not recognized as a subtype of breast cancer. We previously showed that IDC-L may be a variant of IDC with clinicopathological characteristics more similar to invasive lobular carcinoma (ILC). We sought to determine the re-excision rates of IDC-L compared with ILC and IDC, and the feasibility of diagnosing IDC-L on core biopsies.

METHODS

Surgical procedure, multiple tumor foci, tumor size, and residual invasive carcinoma on re-excision were recorded for IDC-L (n = 178), IDC (n = 636), and ILC (n = 251). Re-excision rates were calculated by excluding mastectomy as first procedure cases and including only re-excisions for invasive carcinoma. Slides of correlating core biopsies for IDC-L cases initially diagnosed as IDC were re-reviewed.

RESULTS

For T2 tumors (2.1-5.0 cm), re-excision rates for IDC-L (76 %) and ILC (88 %) were higher than that for IDC (42 %) (p = 0.003). Multiple tumor foci were more common in IDC-L (31 %) and ILC (26 %) than IDC (7 %) (p < 0.0001), which was a significant factor in higher re-excision rates when compared with a single tumor focus (p < 0.001). Ninety-two of 149 patients (62 %) with IDC-L were diagnosed on core biopsies. Of the 44 patients initially diagnosed as IDC, 30 were re-reviewed, of which 24 (80 %) were re-classified as IDC-L.

CONCLUSIONS

Similar to ILC, re-excision rates for IDC-L are higher than IDC for larger tumors. Patients may need to be counseled about the higher likelihood of additional procedures to achieve negative margins. This underscores the importance of distinguishing IDC-L from IDC on core biopsies.

Three dimensional cultures: a tool to study normal acinar architecture vs. malignant transformation of breast cells

Invasive breast carcinomas are a group of malignant epithelial tumors characterized by the invasion of adjacent tissues and propensity to metastasize. The interplay of signals between cancer cells and their microenvironment exerts a powerful influence on breast cancer growth and biological behavior(1). However, most of these signals from the extracellular matrix are lost or their relevance is understudied when cells are grown in two dimensional culture (2D) as a monolayer. In recent years, three dimensional (3D) culture on a reconstituted basement membrane has emerged as a method of choice to recapitulate the tissue architecture of benign and malignant breast cells. Cells grown in 3D retain the important cues from the extracellular matrix and provide a physiologically relevant ex vivo system(2,3). Of note, there is growing evidence suggesting that cells behave differently when grown in 3D as compared to 2D(4). 3D culture can be effectively used as a means to differentiate the malignant phenotype from the benign breast phenotype and for underpinning the cellular and molecular signaling involved(3). One of the distinguishing characteristics of benign epithelial cells is that they are polarized so that the apical cytoplasm is towards the lumen and the basal cytoplasm rests on the basement membrane. This apico-basal polarity is lost in invasive breast carcinomas, which are characterized by cellular disorganization and formation of anastomosing and branching tubules that haphazardly infiltrates the surrounding stroma. These histopathological differences between benign gland and invasive carcinoma can be reproduced in 3D(6,7). Using the appropriate read-outs like the quantitation of single round acinar structures, or differential expression of validated molecular markers for cell proliferation, polarity and apoptosis in combination with other molecular and cell biology techniques, 3D culture can provide an important tool to better understand the cellular changes during malignant transformation and for delineating the responsible signaling.

Inflammatory breast cancer in north Africa: comparison of clinical and molecular epidemiologic characteristics of patients from Egypt, Tunisia, and Morocco

Understanding molecular characteristics that distinguish inflammatory breast cancer (IBC) from non-IBC is crucial for elucidating breast cancer etiology and management. We included 3 sets of patients from Egypt (48 IBC and 64 non-IBC), Tunisia (24 IBC and 40 non-IBC), and Morocco (42 IBC and 41 non-IBC). Egyptian IBC patients had the highest combined erythema, edema, peau d'orange, and metastasis among the 3 IBC groups. Egyptian IBC tumors had the highest RhoC expression than Tunisians and Moroccan IBCs (87% vs. 50%, vs. 38.1, for the 3 countries, respectively). Tumor emboli were more frequent in Egyptian IBC than non-IBC (Mean ± SD: 14.1 ± 14.0 vs. 7.0 ± 12.9, respectively) (P < 0.001) and Tunisians (Mean ± SD: 3.4 ± 2.5 vs. 1.9 ± 2.0, respectively) (P < 0.01). There was no difference of emboli in Moroccan tumors (1.7 ± 1.2 vs. 1.8 ± 1.2 for IBC and non-IBC, respectively (P=0.66). This study illustrates that RhoC overexpression and tumor emboli are more frequent in IBC relative to non-IBC from Egypt and Tunisia. Tumors of Moroccans were significantly different from Egyptian and Tunisian tumors for RhoC expression and emboli. Future studies should focus on relating epidemiologic factors and clinical pictures to molecular features of IBC in these and other populations.