Myoepithelial mRNA expression profiling reveals a common tumor-suppressor phenotype

Dynamic interplay of nuclear receptors in tumor cell plasticity and drug resistance: Shifting gears in malignant transformations and applications in cancer therapeutics

Recent advances have brought forth the complex interplay between tumor cell plasticity and its consequential impact on drug resistance and tumor recurrence, both of which are critical determinants of neoplastic progression and therapeutic efficacy. Various forms of tumor cell plasticity, instrumental in facilitating neoplastic cells to develop drug resistance, include epithelial-mesenchymal transition (EMT) alternatively termed epithelial-mesenchymal plasticity, the acquisition of cancer stem cell (CSC) attributes, and transdifferentiation into diverse cell lineages. Nuclear receptors (NRs) are a superfamily of transcription factors (TFs) that play an essential role in regulating a multitude of cellular processes, including cell proliferation, differentiation, and apoptosis. NRs have been implicated to play a critical role in modulating gene expression associated with tumor cell plasticity and drug resistance. This review aims to provide a comprehensive overview of the current understanding of how NRs regulate these key aspects of cancer biology. We discuss the diverse mechanisms through which NRs influence tumor cell plasticity, including EMT, stemness, and metastasis. Further, we explore the intricate relationship between NRs and drug resistance, highlighting the impact of NR signaling on chemotherapy, radiotherapy and targeted therapies. We also discuss the emerging therapeutic strategies targeting NRs to overcome tumor cell plasticity and drug resistance. This review also provides valuable insights into the current clinical trials that involve agonists or antagonists of NRs modulating various aspects of tumor cell plasticity, thereby delineating the potential of NRs as therapeutic targets for improved cancer treatment outcomes.

Everybody needs good neighbours: the progressive DCIS microenvironment

Ductal carcinoma in situ (DCIS) is a pre-invasive form of breast cancer where neoplastic luminal cells are confined to the ductal tree. While as many as 70% of DCIS cases will remain indolent, most women are treated with surgery, often combined with endocrine and radiotherapies. Overtreatment is therefore a major issue, demanding new methods to stratify patients. Somewhat paradoxically, the neoplastic cells in DCIS are genetically comparable to those in invasive disease, suggesting the tumour microenvironment is the driving force for progression. Clinical and mechanistic studies highlight the complex DCIS microenvironment, with multiple cell types competing to regulate progression. Here, we examine recent studies detailing distinct aspects of the DCIS microenvironment and discuss how these may inform more effective care.

TGFβ-mediated MMP13 secretion drives myoepithelial cell dependent breast cancer progression

Ductal carcinoma in situ (DCIS) is a non-obligate precursor of invasive breast cancer. Virtually all women with DCIS are treated, despite evidence suggesting up to half would remain with stable, non-threatening, disease. Overtreatment thus presents a pressing issue in DCIS management. To understand the role of the normally tumour suppressive myoepithelial cell in disease progression we present a 3D in vitro model incorporating both luminal and myoepithelial cells in physiomimetic conditions. We demonstrate that DCIS-associated myoepithelial cells promote striking myoepithelial-led invasion of luminal cells, mediated by the collagenase MMP13 through a non-canonical TGFβ - EP300 pathway. In vivo, MMP13 expression is associated with stromal invasion in a murine model of DCIS progression and is elevated in myoepithelial cells of clinical high-grade DCIS cases. Our data identify a key role for myoepithelial-derived MMP13 in facilitating DCIS progression and point the way towards a robust marker for risk stratification in DCIS patients.

Re-evaluation of the myoepithelial cells roles in the breast cancer progression

Over the past decades, luminal epithelial cell lineage has gained considerable attraction as the functionally milk-secreting units and as the most fruitful acreage for breast cancer launching. Recognition of the effective involvement of the myoepithelial cells in mammary gland development and in hampering tumorigenesis has renewed the interest in investigating the biological roles of this second main mammary lineage. The human breast is made up of an extensively branching ductal system intervening by copious lobular units. The ductal system is coated by a chain of luminal epithelial cells (LECs) situated on a layer of myoepithelial cells (MECs) and encompassed by a distinguished basement membrane. Ductal contractility during lactation is a well-known function delivered by the MECs however this is not the only assignment mediated by these cellular populations. It has been well appreciated that the MECs exhibit a natural paracrine power in defeating cancer development and advancement. MECs were found to express numerous proteinase inhibitors, anti-angiogenic factors, and tumour suppressors proteins. Additionally, MECs contributed effectively to maintaining the right luminal cells' polarization and further separating them from the adjacent stroma by making an integrated fence. Indeed, disruption of the MECs layer was reported to facilitate the invasion of the cancer cells to the surrounding stroma. Nonetheless, MECs were also found to exhibit cancer-promoting effects and provoke tumour invasion and dissemination by displaying distinct cancer chemokines. Herein in this review, we aimed to address the roles delivered by MECs in breast cancer progression and decipher the molecular mechanisms regulating proper MECs' physiology, integrity, and terminal differentiation.

Prostate Cancer Tumor Stroma: Responsibility in Tumor Biology, Diagnosis and Treatment

Simple Summary

The crosstalk between prostate stroma and its epithelium is essential to tissue homeostasis. Likewise, reciprocal signaling between tumor cells and the stromal compartment is required in tumor progression to facilitate or stimulate key processes such as cell proliferation and invasion. The aim of the present work was to review the current state of knowledge on the significance of tumor stroma in the genesis, progression and therapeutic response of prostate carcinoma. Additionally, we addressed the future therapeutic opportunities.

Abstract

Prostate cancer (PCa) is a common cancer among males globally, and its occurrence is growing worldwide. Clinical decisions about the combination of therapies are becoming highly relevant. However, this is a heterogeneous disease, ranging widely in prognosis. Therefore, new approaches are needed based on tumor biology, from which further prognostic assessments can be established and complementary strategies can be identified. The knowledge of both the morphological structure and functional biology of the PCa stroma compartment can provide new diagnostic, prognostic or therapeutic possibilities. In the present review, we analyzed the aspects related to the tumor stromal component (both acellular and cellular) in PCa, their influence on tumor behavior and the therapeutic response and their consideration as a new therapeutic target.

Expression Profile of Myoepithelial Cells in DCIS: Do They Change From Protective Angels to Wicked Witches?

The mechanism of transition of ductal carcinoma in situ (DCIS) to invasive cancer is elusive but recently changes in the myoepithelial cells (MECs) have been implicated. The aim of this study is to investigate the changes in gene profile of MECs in DCIS that could compromise their tumor suppressor function leading to promotion of tumor progression. Immuno-laser capture microdissection (LCM) was used to isolate MECs from normal and DCIS breast tissues followed by whole genome expression profiling using Affymetrix HGU-133 plus2.0 arrays. The data were analyzed using Bioconductor packages then validated by using real-time quantitative polymerase chain reaction and immunohistochemistry. Ingenuity Pathways software analysis showed clustering of most of the altered genes in cancer and cell death networks, with the Wnt/B-catenin pathway as the top canonical pathway. Validation revealed a 71.4% correlation rate with the array results. Most dramatic was upregulation of Fibronectin 1 ( FN1 ) in DCIS-associated MECs. Immunohistochemistry analysis for FN1 on normal and DCIS tissues confirmed a strong correlation between FN1 protein expression by MECs and DCIS ( P <0.0001) and between high expression level and presence of invasion ( P =0.006) in DCIS. Other validated alterations in MEC expression profile included upregulation of Nephronectin and downregulation of parathyroid hormone like hormone ( PTHLH ), fibroblast growth factor receptor 2 ( FGFR2 ), ADAMTS5 , TGFBR3 , and CAV1 . In vitro experiments revealed downregulation of PTHLH in DCIS-modified MECs versus normal lines when cultured on Fibronectin matrix. This is the first study to use this in vivo technique to investigate molecular changes in MECs in DCIS. This study adds more evidences to the molecular deviations in MECs toward tumor progression in DCIS through upregulation of the tumor-promoting molecules that may lead to novel predictive and therapeutic targets.

The cell of cancer origin provides the most reliable roadmap to its diagnosis, prognosis (biology) and therapy

Cancers arise from single transformed cells from virtually every organ of the body, divide in a relatively uncontrolled manner, and metastasize widely. A search for a "magic bullet" to precisely diagnose, characterize, and ultimately treat cancer has largely failed because cancer cells do not differ significantly from their organ-specific cells of origin. Instead of searching for genomic, epigenetic, transcriptional, and translational differences between cancers and their cells of origin, we should paradoxically focus on what cancer cells have in common with their untransformed cells of origin. This redirected search will lead to improved diagnostic and therapeutic strategies where therapeutic index considerations and drug-limiting toxicities can largely be circumvented. We cite three cancer examples that illustrate this paradigm-shifting strategy: pseudomyxoma peritonei (PP), metastasis of unknown origin (cancers of unknown primary) (MUO), and cancers that arise from potentially dispensable organs (CAD). In each of these examples, the cell of cancer origin still provides the most reliable road map to its diagnosis, prognosis (biology), and therapy.

Two sides of the same coin: Insights into the myoepithelial cells in carcinoma ex pleomorphic adenoma development

The myoepithelial cell seems to play an important role as a tumor suppressor in the development of carcinoma ex pleomorphic adenoma. Nevertheless, interesting aspects concerning the other side of the coin, i.e., the contribution of the myoepithelial cell to cell proliferation, were brought to light. Here we highlighted the studies in which myoepithelial cells were presented as tumor suppressors and promoters in the context of PA malignant transformation. In conclusion, even if in a paracrine way, divergent signals can alter the suppressor role of the myoepithelial cell and induce it to compose a microenvironment propitious to the tumor progression of the malignant cells. This would cause myoepithelial cells to succumb and malignant epithelial cells to initiate progression beyond the basal membrane.

A Complex and Evolutive Character: Two Face Aspects of ECM in Tumor Progression

Tumor microenvironment, including extracellular matrix (ECM) and stromal cells, is a key player during tumor development, from initiation, growth and progression to metastasis. During all of these steps, remodeling of matrix components occurs, changing its biochemical and physical properties. The global and basic cancer ECM model is that tumors are surrounded by activated stromal cells, that remodel physiological ECM to evolve into a stiffer and more crosslinked ECM than in normal conditions, thereby increasing invasive capacities of cancer cells. In this review, we show that this too simple model does not consider the complexity, specificity and heterogeneity of each organ and tumor. First, we describe the general ECM in context of cancer. Then, we go through five invasive and most frequent cancers from different origins (breast, liver, pancreas, colon, and skin), and show that each cancer has its own specific matrix, with different stromal cells, ECM components, biochemical properties and activated signaling pathways. Furthermore, in these five cancers, we describe the dual role of tumor ECM: as a protective barrier against tumor cell proliferation and invasion, and as a major player in tumor progression. Indeed, crosstalk between tumor and stromal cells induce changes in matrix organization by remodeling ECM through invadosome formation in order to degrade it, promoting tumor progression and cell invasion. To sum up, in this review, we highlight the specificities of matrix composition in five cancers and the necessity not to consider the ECM as one general and simple entity, but one complex, dynamic and specific entity for each cancer type and subtype.

Loss of myoepithelial calponin-1 characterizes high-risk ductal carcinoma in situ cases, which are further stratified by T cell composition

A hallmark of ductal carcinoma in situ (DCIS) progression is a loss of the surrounding ductal myoepithelium. However, whether compromise in myoepithelial differentiation, rather than overt cellular loss, can be used to predict the risk of DCIS progression is unknown. Here we address this question utilizing pure and mixed DCIS cases (N = 30) as surrogates for DCIS at low and high risk for progression, respectively. We used multiplex immunohistochemical staining to evaluate the relationship between myoepithelial cell differentiation and lymphoid immune cell types associated with poor prognostic DCIS. Our results show that myoepithelial calponin-1 discriminates between pure and mixed DCIS lesions better than histological subtype, presence of necrosis, or nuclear grade. Additionally, focal loss of myoepithelial cells associated with increased PD-1+CD8+ T cells, which suggests a link between the myoepithelium and immune surveillance. To identify associations between calponin-1 expression and immune response, we performed unsupervised hierarchical clustering of myoepithelial and immune cell biomarkers on 219 DCIS lesions from 30 cases. Notably, the majority of pure (low-risk) DCIS lesions clustered in a high calponin-1, T cell low group, whereas the majority of mixed (high-risk) DCIS lesions clustered in a low calponin-1, T cell high group, specifically with CD8+ and PD-1+CD8+ T cells. However, a subset of pure DCIS lesions had a similar calponin-1 and immune signature as the majority of mixed DCIS lesions, which have low calponin-1 and T cell enrichment-raising the possibility that these pure DCIS lesions might be at a high risk for progression.

Is it ductal carcinoma in situ with microinvasion or "Ductogenesis"? The role of myoepithelial cell markers

Mammary myoepithelial cells have been under-recognized for many years since they were considered less important in breast cancer tumorigenesis compared to luminal epithelial cells. However, in recent years with advances in genomics, cell biology, and research in breast cancer microenvironment, more emphasis has been placed on better understanding of the role that myoepithelial cells play in breast cancer progression. As the result, it has been recognized that the presence or absence of myoepithelial cells play a critical role in the assessment of tumor invasion in diagnostic breast pathology. In addition, advances in screening mammography and breast imaging has resulted in increased detection of ductal carcinoma in situ and consequently more diagnosis of ductal carcinoma in situ with microinvasion. In the present review, we discuss the characteristics of myoepithelial cells, their genomic markers and their role in the accurate diagnosis of ductal carcinoma in situ with microinvasion. We also share our experience with reporting of various morphologic features of ductal carcinoma in situ that may mimic microinvasion and introduce the term of ductogenesis.

Proliferative Activity of Myoepithelial Cells in Normal Salivary Glands and Adenoid Cystic Carcinomas Based on Double Immunohistochemical Labeling

Objective

To investigate the proliferative activity of myoepithelial cells (MEC) in normal salivary glands (NSG) and adenoid cystic carcinomas (ACC)) Study design. Twenty -three salivary gland specimens (13 ACC, 10 NSG) were studied using double immunohistochemical labeling for α smooth muscle actin (a-SMA) and proliferative cell nuclear antigen (PCNA)).

Results

There was a significant difference in PCNA reactivity in normal samples between myoepithelial cells of the parotid glands and of the submandibular glands, rates being higher in the latter. Neoplastic myoepithelial cells exhibited higher expression than neoplastic epithelial cells. In addition, myoepithelial cells of the cribriform type of ACC showed PCNA reactivity lower than those of the tubular type, whereas there was no statistically significant difference in epithelial cell rates. We could not identify myoepithelial cells in solid pattern due to α-SMA negativity; although high PCNA reactivity was evident.

Conclusion

These data suggest that the myoepithelial cell has a key role in ACC oncogenesis, more so than its epithelial cell counterparts. Moreover, the data provide a histopathological interpretation for aggressive clinical features of submandibular ACC, as the myoepithelial cells were less differentiated as compared to those of parotid glands.

Loss of MMP-8 in ductal carcinoma in situ (DCIS)-associated myoepithelial cells contributes to tumour promotion through altered adhesive and proteolytic function

BACKGROUND

Normal myoepithelial cells (MECs) play an important tumour-suppressor role in the breast but display an altered phenotype in ductal carcinoma in situ (DCIS), gaining tumour-promoter functions. Matrix metalloproteinase-8 (MMP-8) is expressed by normal MECs but is lost in DCIS. This study investigated the function of MMP-8 in MECs and the impact of its loss in DCIS.

METHODS

Primary normal and DCIS-associated MECs, and normal (N-1089) and DCIS-modified myoepithelial (β6-1089) cell lines, were used to assess MMP-8 expression and function. β6-1089 lacking MMP-8 were transfected with MMP-8 WT and catalytically inactive MMP-8 EA, and MMP-8 in N-1089 MEC was knocked down with siRNA. The effect on adhesion and migration to extracellular matrix (ECM), localisation of α6β4 integrin to hemidesmosomes (HD), TGF-β signalling and gelatinase activity was measured. The effect of altering MEC MMP-8 expression on tumour cell invasion was investigated in 2D and 3D organotypic models.

RESULTS

Assessment of primary cells and MEC lines confirmed expression of MMP-8 in normal MEC and its loss in DCIS-MEC. Over-expression of MMP-8 WT but not MMP-8 EA in β6-1089 cells increased adhesion to ECM proteins and reduced migration. Conversely, knock-down of MMP-8 in N-1089 reduced adhesion and increased migration. Expression of MMP-8 WT in β6-1089 led to greater localisation of α6β4 to HD and reduced retraction fibre formation, this being reversed by MMP-8 knock-down in N-1089. Over-expression of MMP-8 WT reduced TGF-β signalling and gelatinolytic activity. MMP-8 knock-down enhanced TGF-β signalling and gelatinolytic activity, which was reversed by blocking MMP-9 by knock-down or an inhibitor. MMP-8 WT but not MMP-8 EA over-expression in β6-1089 reduced breast cancer cell invasion in 2D and 3D invasion assays, while MMP-8 knock-down in N-1089 enhanced cancer cell invasion. Staining of breast cancer cases for MMP-8 revealed a statistically significant loss of MMP-8 expression in DCIS with invasion versus pure DCIS (p = 0.001).

CONCLUSIONS

These data indicate MMP-8 is a vital component of the myoepithelial tumour-suppressor function. It restores MEC interaction with the matrix, opposes TGF-β signalling and MMP-9 proteolysis, which contributes to inhibition of tumour cell invasion. Assessment of MMP-8 expression may help to determine risk of DCIS progression.

Environmental factors in breast cancer invasion: a mathematical modelling review

This review presents a brief overview of breast cancer, focussing on its heterogeneity and the role of mathematical modelling and simulation in teasing apart the underlying biophysical processes. Following a brief overview of the main known pathophysiological features of ductal carcinoma, attention is paid to differential equation-based models (both deterministic and stochastic), agent-based modelling, multi-scale modelling, lattice-based models and image-driven modelling. A number of vignettes are presented where these modelling approaches have elucidated novel aspects of breast cancer dynamics, and we conclude by offering some perspectives on the role mathematical modelling can play in understanding breast cancer development, invasion and treatment therapies.

Identifying progression predictors of breast ductal carcinoma in situ

Ductal carcinoma in situ (DCIS) refers to neoplastic epithelial cells proliferating within the mammary ducts of the breast, which have not breached the basement membrane nor invaded surrounding tissues. Traditional thinking holds that DCIS represents an early step in a linear progression towards invasive ductal carcinoma (IDC). However, as only approximately half of DCIS cases progress to IDC, important questions around the key determinants of malignant progression need to be answered. Recent studies have revealed that molecular differences between DCIS and IDC cells are not found at the genomic level; instead, altered patterns of gene expression and post-translational regulation lead to distinct transcriptomic and proteomic profiles. Therefore, understanding malignant progression will require a different approach that takes into account the diverse tumour cell extrinsic factors driving changes in tumour cell gene expression necessary for the invasive phenotype. Here, we review the roles of the tumour stroma (including mesenchymal cells, immune cells and the extracellular matrix) and myoepithelial cells in malignant progression and make a case for a more integrated approach to the study and assessment of DCIS and its progression, or lack thereof, to invasive disease.

Development and characterisation of a 3D multi-cellular in vitro model of normal human breast: a tool for cancer initiation studies

Multicellular 3-dimensional (3D) in vitro models of normal human breast tissue to study cancer initiation are required. We present a model incorporating three of the major functional cell types of breast, detail the phenotype and document our breast cancer initiation studies. Myoepithelial cells and fibroblasts were isolated and immortalised from breast reduction mammoplasty samples. Tri-cultures containing non-tumorigenic luminal epithelial cells HB2, or HB2 overexpressing different HER proteins, together with myoepithelial cells and fibroblasts were established in collagen I. Phenotype was assessed morphologically and immunohistochemically and compared to normal breast tissue. When all three cell types were present, polarised epithelial structures with lumens and basement membrane production were observed, akin to normal human breast tissue. Overexpression of HER2 or HER2/3 caused a significant increase in size, while HER2 overexpression resulted in development of a DCIS-like phenotype. In summary, we have developed a 3D tri-cellular model of normal human breast, amenable to comparative analysis after genetic manipulation and with potential to dissect the mechanisms behind the early stages of breast cancer initiation.

Basal cytokeratin phenotypes of myoepithelial cells indicates the origin of ductal carcinomas in situ of the breast

Terminal duct lobular unit (TDLU) is widely accepted as the origin of ductal carcinoma in situ of breast. The differentiation states of myoepithelial cells of breast ductal system hint the development of breast hyperplastic lesions. Basal cytokeratin (CK) phenotypes indicate the differentiation of myoepithelial cells. Using antibodies of CK5/6, CK14, and CK17, this study reports the basal CK phenotypes of myoepithelial cells in 20 foci of normal breast, 20 usual ductal hyperplasias, 36 ductal carcinomas in situ (DCIS), and 28 sclerosing adenosis (SA). The results showed that the positive staining of basal CKs of myoepithelial cells in normal ducts were significantly higher than those in normal lobules. The basal CK expression of myoepithelial cells of DCIS and usual ductal hyperplasia was similar to that of normal duct, whereas that of SA was similar to that of normal lobule. We propose a modified model of TDLU origin of intraductal carcinoma that most of DCIS originate from terminal ducts of TDLU, whereas most SA originate from lobules.

Myoepithelial and luminal breast cancer cells exhibit different responses to all-trans retinoic acid

PURPOSE

Breast cancer is the leading cause of death among women worldwide. The exact role of luminal epithelial (LEP) and myoephitelial (MEP) cells in breast cancer development is as yet unclear, as also how retinoids may affect their behaviour. Here, we set out to evaluate whether retinoids may differentially regulate cell type-specific processes associated with breast cancer development using the bi-cellular LM38-LP murine mammary adenocarcinoma cell line as a model.

MATERIALS AND METHODS

The bi-cellular LM38-LP murine mammary cell line was used as a model throughout all experiments. LEP and MEP subpopulations were separated using inmunobeads, and the expression of genes known to be involved in epithelial to mysenchymal transition (EMT) was assessed by qPCR after all-trans retinoic acid (ATRA) treatment. In vitro invasive capacities of LM38-LP cells were evaluated using 3D Matrigel cultures in conjunction with confocal microscopy. Also, in vitro proliferation, senescence and apoptosis characteristics were evaluated in the LEP and MEP subpopulations after ATRA treatment, as well as the effects of ATRA treatment on the clonogenic, adhesive and invasive capacities of these cells. Mammosphere assays were performed to detect stem cell subpopulations. Finally, the orthotopic growth and metastatic abilities of LM38-LP monolayer and mammosphere-derived cells were evaluated in vivo.

RESULTS

We found that ATRA treatment modulates a set of genes related to EMT, resulting in distinct gene expression signatures for the LEP or MEP subpopulations. We found that the MEP subpopulation responds to ATRA by increasing its adhesion to extracellular matrix (ECM) components and by reducing its invasive capacity. We also found that ATRA induces apoptosis in LEP cells, whereas the MEP compartment responded with senescence. In addition, we found that ATRA treatment results in smaller and more organized LM38-LP colonies in Matrigel. Finally, we identified a third subpopulation within the LM38-LP cell line with stem/progenitor cell characteristics, exhibiting a partial resistance to ATRA.

CONCLUSIONS

Our results show that the luminal epithelial (LEP) and myoephitelial (MEP) mammary LM38-P subpopulations respond differently to ATRA, i.e., the LEP subpopulation responds with increased cell cycle arrest and apoptosis and the MEP subpopulation responds with increased senescence and adhesion, thereby decreasing its invasive capacity. Finally, we identified a third subpopulation with stem/progenitor cell characteristics within the LM38-LP mammary adenocarcinoma cell line, which appears to be non-responsive to ATRA.

The role of FGF-2/HGF and fibronectin matrix on pleomorphic adenoma myoepithelial cell morphology and immunophenotype: an in vitro study

Myoepithelial cells play a central role in glandular tumors, regulating the progression of in situ to invasive neoplasias, with the tumor microenvironment being shown to be involved in both initiation and progression. This study aimed to analyze the in vitro effects of fibroblast growth factor-2 (FGF-2) and hepatocyte growth factor (HGF) in myoepithelial cells under the influence of the fibronectin matrix extracellular protein. Benign myoepithelial cells were obtained from pleomorphic adenoma and cultured on a fibronectin substratum. FGF-2 and HGF were supplemented at different concentrations and time intervals, in order to evaluate cell proliferation, morphology and immunophenotype. Individually, FGF-2 and HGF supplementation did not alter myoepithelial cell proliferation, morphology or immunophenotype. The fibronectin substratum provoked an increase in cell proliferation and immunopositivity for α-smooth muscle actin and FGF-2. The myoepithelial cell morphology changed when the fibronectin substratum and FGF-2 acted together, highlighting the importance of the fibronectin extracellular matrix protein on the behavior of these cells.

Ductal carcinoma in situ of the breast: morphological and molecular features implicated in progression

The spread of mammographic screening programmes around the world, including in developing countries, has substantially contributed to the diagnosis of small non-palpable lesions, which has increased the detection rate of DCIS (ductal carcinoma in situ). DCIS is heterogeneous in several ways, such as its clinical presentation, morphology and genomic profile. Excellent outcomes have been reported; however, many questions remain unanswered. For example, which patients groups are overtreated and could instead benefit from minimal intervention and which patient groups require a more traditional multidisciplinary approach. The development of a comprehensive integrated analysis that includes the radiological, morphological and genetic aspects of DCIS is necessary to answer these questions. This review focuses on discussing the significant findings about the morphological and molecular features of DCIS and its progression that have helped to uncover the biological and genetic heterogeneity of this disease. The knowledge gained in recent years might allow the development of tailored clinical management for women with DCIS in the future.

Atbf1 regulates pubertal mammary gland development likely by inhibiting the pro-proliferative function of estrogen-ER signaling

ATBF1 is a candidate tumor suppressor that interacts with estrogen receptor (ER) to inhibit the function of estrogen-ER signaling in gene regulation and cell proliferation control in human breast cancer cells. We therefore tested whether Atbf1 and its interaction with ER modulate the development of pubertal mammary gland, where estrogen is the predominant steroid hormone. In an in vitro model of cell differentiation, i.e., MCF10A cells cultured in Matrigel, ATBF1 expression was significantly increased, and knockdown of ATBF1 inhibited acinus formation. During mouse mammary gland development, Atbf1 was expressed at varying levels at different stages, with higher levels during puberty, lower during pregnancy, and the highest during lactation. Knockout of Atbf1 at the onset of puberty enhanced ductal elongation and bifurcation and promoted cell proliferation in both ducts and terminal end buds of pubertal mammary glands. Enhanced cell proliferation primarily occurred in ER-positive cells and was accompanied by increased expression of ER target genes. Furthermore, inactivation of Atbf1 reduced the expression of basal cell markers (CK5, CK14 and CD44) but not luminal cell markers. These findings indicate that Atbf1 plays a role in the development of pubertal mammary gland likely by modulating the function of estrogen-ER signaling in luminal cells and by modulating gene expression in basal cells.

In vitro evaluation of the suppressor potential of conditioned medium from benign myoepithelial cells from pleomorphic adenoma in malignant cell invasion

Tumoral invasion process is the result of a complex interaction between the tumor cells and microenvironment which plays an important role in modulating the growth and invasion of the cancer. The myoepithelial cells, present in glandular organs such as the breast and salivary glands, seem to exert paracrine effects on the glandular epithelium, acting as natural tumor suppressors. To verify the influence of the benign myoepithelial cells in the invasion of malignant cells, simulating an in situ carcinoma ex pleomorphic adenoma, we have cultured three different high-potential invasive malignant tumors (breast ductal adenocarcinoma, melanoma and oral squamous cell carcinoma) in conditioned medium of myoepithelial cells from salivary gland pleomorphic adenomas using transwell chambers with 8-μm pores membrane coated with matrigel. After 96 h, quantitative analyses of the results were performed by calculating the invasion index (number of cells that invaded in relation to the total number of cells). The results showed that there was a reduction of the invasion index mean for the three different malignant tumors. This study supports a tumoral suppressor function of the myoepithelial cells from pleomorphic adenoma in in vitro invasion process.

CD44 Promotes Epithelial Mammary Gland Development and Exhibits Altered Localization during Cancer Progression

The basal cell layer has emerged as a critical player in cancer progression, and understanding the molecular contribution of specific cell types is important in treatment and prevention. The adhesion receptor CD44, which mediates epithelial-stromal and cell-cell interactions, has been shown to both promote and suppress tumor progression. To better understand the normal function of CD44, we have investigated its role in mouse mammary gland development and its expression in human breast and prostate cancer. We have found that CD44 is expressed in the myoepithelium of the developing mammary gland and modulates ductal development of FVB/N mice. The loss of CD44 results in defective luminal-myoepithelial cell-cell adhesion and promotes the mixing of luminal and myoepithelial layers, disrupting epithelial bilayer organization, and CD44-null mice experience delayed ductal outgrowth and impaired terminal end bud formation. The myoepithelial expression of CD44 is also relevant to its expression in cancer, as CD44 is expressed in the basal cells of early-stage breast and prostate cancer but exhibits altered localization with increasing tumorigenicity and is strongly expressed by tumor epithelium.

Singular v dual inhibition of SNF2L and its isoform, SNF2LT, have similar effects on DNA damage but opposite effects on the DNA damage response, cancer cell growth arrest and apoptosis

SNF2L, an ATPase chromatin remodeling gene nearly ubiquitously expressed in diverse tissues, cancers, and derived cell lines, contributes to the chromatin remodeling complex that facilitates transcription. Because of this near ubiquitous expression, it has not been exploited as a cancer therapeutic target. However, in a recent study, we found that highly malignant cancer cells, although expressing SNF2L at similar levels as their normal counterparts, were sensitive to its knockdown. Only the highly malignant (HM) lines showed significant growth inhibition, DNA damage, a DNA damage response, and phosphorylation of checkpoint proteins and marked apoptosis. In studying SNF2L, we discovered a novel truncated isoform, SNF2LT which, when compared to full length SNF2L, lacked three important domains: HAND, SANT and SLIDE. Although truncated isoforms usually have antagonistic functions to their parental molecule, here SNF2LT knockdown had similar effects to the knockdown of its parental molecule, SNF2L, of inducing DNA damage, a DNA damage response, cell cycle arrest and apoptosis selectively in cancer cell lines. However dual SNF2L and SNF2LT knockdown, while inducing DNA damage, did not result in a DNA damage response, a cell cycle arrest and apoptosis. In fact HM lines subjected to dual knockdown paradoxically exhibited sustained cell growth. Our findings indicate that the ratio of SNF2L to its isoform tightly regulates the cancer cell's response to DNA damage. Cancer cell lines which endogenously express low levels of both SNF2L and its isoform mimic the situation of dual knockdown and permit DNA damage which is allowed to propagate unchecked.

Active roles of tumor stroma in breast cancer metastasis

Metastasis is the major cause of death for breast cancer patients. Tumors are heterogenous cellular entities composed of cancer cells and cells of the microenvironment in which they reside. A reciprocal dynamic interaction occurs between the tumor cells and their surrounding stroma under physiological and pathological conditions. This tumor-host communication interface mediates the escape of tumor cells at the primary site, survival of circulating cancer cells in the vasculature, and growth of metastatic cancer at secondary site. Each step of the metastatic process is accompanied by recruitment of stromal cells from the microenvironment and production of unique array of growth factors and chemokines. Stromal microenvironment may play active roles in breast cancer metastasis. Elucidating the types of cells recruited and signal pathways involved in the crosstalk between tumor cells and stromal cells will help identify novel strategies for cotargeting cancer cells and tumor stromal cells to suppress metastasis and improve patient outcome.

Fabrication and biological evaluation of uniform extracellular matrix coatings on discontinuous photolithography generated micropallet arrays

The recent identification of rare cell populations within tissues that are associated with specific biological behaviors, for example, progenitor cells, has illuminated a limitation of current technologies to study such adherent cells directly from primary tissues. The micropallet array is a recently developed technology designed to address this limitation by virtue of its capacity to isolate and recover single adherent cells on individual micropallets. The capacity to apply this technology to primary tissues and cells with restricted growth characteristics, particularly adhesion requirements, is critically dependent on the capacity to generate functional extracellular matrix (ECM) coatings. The discontinuous nature of the micropallet array surface provides specific constraints on the processes for generating the desired ECM coatings that are necessary to achieve the full functional capacity of the micropallet array. We have developed strategies, reported herein, to generate functional coatings with various ECM protein components: fibronectin, EHS tumor basement membrane extract, collagen, and laminin-5; confirmed by evaluation for rapid cellular adherence of four dissimilar cell types: fibroblast, breast epithelial, pancreatic epithelial, and myeloma. These findings are important for the dissemination and expanded use of micropallet arrays and similar microtechnologies requiring the integrated use of ECM protein coatings to promote cellular adherence.

The lymphovascular embolus of inflammatory breast cancer exhibits a Notch 3 addiction

Inflammatory breast carcinoma (IBC) is characterized by exaggerated lymphovascular invasion (LVI), recapitulated in our human xenograft, MARY-X. This model exhibited lymphovascular emboli in vivo and corresponding spheroids in vitro. Owing to the morphological and gene profile resemblance of these spheroids to embryonal blastocysts, we wondered whether they might exhibit embryonic stem cell signaling. Specifically we investigated Notch and observed selective Notch 3 activation by expression profiling, reverse transcriptase- and real-time PCR, western blot and immunofluorescence in vitro, and immunohistochemistry in vivo. Notch 3 intracellular domain (N3icd) and six target genes, HES-5, HEY-1, c-Myc, Deltex-1, NRARP and PBX1, markedly increased in MARY-X. In addition, a significant percentage of MARY-X cells expressed aldehyde dehydrogenase (ALDH), a stem cell marker. Only the ALDH(+) cells were capable of secondary spheroidgenesis, tumorigenicity and self-renewal. Inhibiting Notch 3 activation in vitro with γ-secretase inhibitors (GSIs) or small interfering RNA resulted in a downregulation of Notch target genes, including CD133, and an induction of caspase 3-mediated apoptosis. Transfection of N3icd but not Notch 1 intracellular domain into normal human mammary epithelial cells resulted in increased expression of Notch target genes and induction of spheroidgenesis. GSI in vivo resulted in inhibitory but diffusion-limited effects on Notch 3 signaling, resulting in xenograft growth reduction. The lymphovascular emboli of human IBC exhibited dual N3icd and ALDH1 immunoreactivities independently of molecular subtype. This Notch 3 addiction of lymphovascular emboli might be exploited in future therapeutic strategies.

Use and validation of epithelial recognition and fields of view algorithms on virtual slides to guide TMA construction

While tissue microarrays (TMAs) are a form of high-throughput screening, they presently still require manual construction and interpretation. Because of predicted increasing demand for TMAs, we investigated whether their construction could be automated. We created both epithelial recognition algorithms (ERAs) and field of view (FOV) algorithms that could analyze virtual slides and select the areas of highest cancer cell density in the tissue block for coring (algorithmic TMA) and compared these to the cores manually selected (manual TMA) from the same tissue blocks. We also constructed TMAs with TMAker, a robot guided by these algorithms (robotic TMA). We compared each of these TMAs to each other. Our imaging algorithms produced a grid of hundreds of FOVs, identified cancer cells in a stroma background and calculated the epithelial percentage (cancer cell density) in each FOV. Those with the highest percentages guided core selection and TMA construction. Algorithmic TMA and robotic TMA were overall approximately 50% greater in cancer cell density compared with Manual TMA. These observations held for breast, colon, and lung cancer TMAs. Our digital image algorithms were effective in automating TMA construction.

ERalpha signaling through slug regulates E-cadherin and EMT

The ERalpha signaling pathway is one of the most important and most studied pathways in human breast cancer, yet numerous questions still exist such as how hormonally responsive cancers progress to a more aggressive and hormonally independent phenotype. We have noted that human breast cancers exhibit a strong direct correlation between ERalpha and E-cadherin expression by immunohistochemistry, suggesting that ERalpha signaling might regulate E-cadherin and implying that this regulation might influence epithelial-mesenchymal transition (EMT) and tumor progression. To investigate this hypothesis and the mechanisms behind it, we studied the effects of ERalpha signaling in ERalpha-transfected ERalpha-negative breast carcinoma cell lines, the MDA-MB-468 and the MDA-MB-231 and the effects of ERalpha knockdown in naturally expressing ERalpha-positive lines, MCF-7 and T47D. When ERalpha was overexpressed in the ERalpha-negative lines, 17beta-estradiol (E2) decreased slug and increased E-cadherin. Clones maximally exhibiting these changes grew more in clumps and became less invasive in Matrigel. When ERalpha was knocked down in the ERalpha-positive lines, slug increased, E-cadherin decreased, cells became spindly and exhibited increased Matrigel invasion. ERalpha signaling decreased slug expression by two different mechanisms: directly, by repression of slug transcription by the formation of a corepressor complex of ligand-activated ERalpha, HDAC inhibitor (HDAC1), and nuclear receptor corepressor (N-CoR) that bound the slug promoter in three half-site estrogen response elements (EREs); indirectly by phosphorylation and inactivation of GSK-3beta through phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt). The GSK-3beta inactivation, in turn, repressed slug expression and increased E-cadherin. In human breast cancer cases, there was a strong inverse correlation between slug and ERalpha and E-cadherin immunoreactivity. Our findings indicate that ERalpha signaling through slug regulates E-cadherin and EMT.

FGF-2, TGFbeta-1, PDGF-A and respective receptors expression in pleomorphic adenoma myoepithelial cells: an in vivo and in vitro study

Myoepithelial cells have an important role in salivary gland tumor development, contributing to a low grade of aggressiveness of these tumors. Normal myoepithelial cells are known by their suppressor function presenting increased expression of extracellular matrix genes and protease inhibitors. The importance of stromal cells and growth factors during tumor initiation and progression has been highlighted by recent literature. Many tumors result from the alteration of paracrine growth factors pathways. Growth factors mediate a wide variety of biological processes such as development, tissue repair and tumorigenesis, and also contribute to cellular proliferation and transformation in neoplastic cells.

OBJECTIVES

This study evaluated the expression of fibroblast growth factor-2 (FGF-2), transforming growth factor beta-1 (TGFbeta-1), platelet-derived growth factor-A (PDGF-A) and their respective receptors (FGFR-1, FGFR-2, TGFbetaR-II and PDGFR-alpha) in myoepithelial cells from pleomorphic adenomas (PA) by in vivo and in vitro experiments.

MATERIAL AND METHODS

Serial sections were obtained from paraffin-embedded PA samples obtained from the school's files. Myoepithelial cells were obtained from explants of PA tumors provided by surgery from different donors. Immunohistochemistry, cell culture and immunofluorescence assays were used to evaluate growth factor expression.

RESULTS

The present findings demonstrated that myoepithelial cells from PA were mainly positive to FGF-2 and FGFR-1 by immunohistochemistry and immunofluorescence. PDGF-A and PDGFR-alpha had moderate expression by immunohistochemistry and presented punctated deposits throughout cytoplasm of myoepithelial cells. FGFR-2, TGFbeta-1 and TGFbetaR-II were negative in all samples.

CONCLUSIONS

These data suggested that FGF-2 compared to the other studied growth factors has an important role in PA benign myoepithelial cells, probably contributing to proliferation of these cells through the FGFR-1.

The effect of proteoglycans inhibited by RNA interference on metastatic characters of human salivary adenoid cystic carcinoma

BACKGROUND

Salivary adenoid cystic carcinoma (SACC) is one of the most common malignancies of salivary gland. Recurrence or/and early metastasis is its biological properties. In SACC, neoplastic myoepithelial cells secrete proteoglycans unconventionally full of the cribriform or tubular and glandular structures of SACC. Literatures have demonstrated that extracellular matrix provided an essential microenvironment for the biological behavior of SACC. However, there is rare study of the effect of proteoglycans on the potential metastasis of SACC.In this study, human xylosyltransferase-I (XTLY-I) gene, which catalyzes the rate-limited step of proteoglycans biosynthesis, was knocked down by RNA interference (RNAi) to inhibit the proteoglycans biosynthesis in SACC cell line with high tendency of lung metastasis (SACC-M). The impact of down-regulated proteoglycans on the metastasis characters of SACC-M cells was analyzed and discussed. This research could provide a new idea for the clinical treatment of SACC.

METHODS

The eukaryotic expression vector of short hairpin RNA (shRNA) targeting XTLY-I gene was constructed and transfected into SACC-M cells. A stably transfectant cell line named SACC-M-WJ4 was isolated. The XTLY-I expression was measured by real-time PCR and Western blot; the reduction of proteoglycans was measured. The invasion and metastasis of SACC-M-WJ4 cells were detected; the effect of down-regulated proteoglycans on the potential lung metastasis of nude mice was observed, respectively.

RESULTS

The shRNA plasmid targeting XTLY-I gene showed powerful efficiency of RNAi. The mRNA level of target gene decreased by 86.81%, the protein level was decreased by 80.10%, respectively. The silence of XTLY-I gene resulted in the reduction of proteoglycans significantly in SACC-M-WJ4 cells. The inhibitory rate of proteoglycans was 58.17% (24 h), 66.06% (48 h), 57.91% (72 h), 59.36% (96 h), and 55.65% (120 h), respectively. The reduction of proteoglycans suppressed the adhesion, invasion and metastasis properties of SACC-M cells, and decreased the lung metastasis of SACC-M cells markedly either.

CONCLUSION

The data suggested that the silence of XTLY-I gene in SACC-M cells could suppress proteoglycans biosynthesis and secretion significantly. The reduction of proteoglycans inhibited cell adhesion, invasion and metastasis of SACC-M cells. There is a close relationship between proteoglycans and the biological behavior of SACC.

ERalpha suppresses slug expression directly by transcriptional repression

Two of the most common signalling pathways in breast cancer are the ER (oestrogen receptor) ligand activation pathway and the E-cadherin snai1 slug EMT (epithelial-mesenchymal transition) pathway. Although these pathways have been thought to interact indirectly, the present study is the first to observe direct interactions between these pathways that involves the regulation of slug expression. Specifically we report that ligand-activated ERalpha suppressed slug expression directly by repression of transcription and that knockdown of ERalpha with RNA interference increased slug expression. More specifically, slug expression was down-regulated in ERalpha-negative MDA-MB-468 cells transfected with ERalpha after treatment with E2 (17beta-oestradiol). The down-regulation of slug in the ERalpha-positive MCF-7 cell line was mediated by direct repression of slug transcription by the formation of a co-repressor complex involving ligand-activated ERalpha protein, HDAC1 (histone deacetylase 1) and N-CoR (nuclear receptor co-repressor). This finding was confirmed by sequential ChIP (chromatin immunoprecipitation) studies. In the MCF-7 cell line, slug expression normally was low. In addition, knockdown of ERalpha with RNA interference in this cell line increased slug expression. This effect could be partially reversed by treatment of the cells with E2. The efficacy of the effect of ERalpha on slug repression was dependent on the overall level of ERalpha. These observations confirmed that slug was an E2-responsive gene.

Are complex carcinoma of the feline mammary gland and other invasive mammary carcinoma identical tumours? Comparison of clinicopathologic features, DNA ploidy and follow up

Feline mammary carcinomas are known for their unfavourable prognosis due to a strong tendency to local recurrence and metastasis. We studied 73 spontaneous primary mammary carcinomas and identified eight cases presenting a biphasic nature, with neoplastic epithelial and myoepithelial cells (complex carcinoma). These cases presented histopathologic features associated with a better prognosis; they were also associated with higher overall survival and disease-free survival rates compared to other common invasive mammary carcinomas of non-specified type. Complex carcinoma appears to be a low-grade malignancy.

Progestin-regulated luminal cell and myoepithelial cell-specific responses in mammary organoid culture

Normal mammary gland development requires the coordinated proliferation and morphogenesis of both mammary luminal epithelial cells (LECs) and myoepithelial cells (MECs). Cell proliferation in cultured mammary organoids containing both LECs and MECs is not increased by progestin (R5020) or 17beta-estradiol (E2) alone or R5020+E2 but is increased by E2-regulated, mammary stroma-derived Hepatocyte growth factor (HGF) and further increased by HGF+R5020. We investigated the effects of HGF and/or R5020 on morphology and LEC- and MEC-specific in vitro proliferation in organoids. HGF-induced tubulogenesis was initiated and carried out by LECs starting with cellular extensions, followed by the formation of chains and cords, and culminating in tubule formation. MECs did not appear to have an active role in this process. Whereas HGF by itself caused maximal proliferation of LECs, HGF+R5020 produced a synergistic and specific increase in MEC proliferation. Because only LECs expressed progesterone receptors (PRs), we investigated the role of receptor activator of nuclear factor-kappaB ligand (RANKL), a progestin-induced paracrine factor, in mediating increased MEC proliferation. Quantitative RT-PCR showed that RANKL mRNA was induced by R5020 or HGF+R5020 and RANKL protein colocalized with PRs in LECs. The increased proliferation of MECs in response to HGF+R5020 could be blocked by neutralizing antibody to RANKL and reproduced by treatment with HGF plus exogenous RANKL in place of R5020. Neither R5020, nor exogenously administered RANKL increased proliferation of LECs. These results led us to conclude that RANKL, induced by progestin in PR-positive cells, is secreted and interacts with HGF to specifically increase proliferation of PR-negative MECs.

Breast cancer: origins and evolution

Breast cancer is not a single disease, but rather is composed of distinct subtypes associated with different clinical outcomes. Understanding this heterogeneity is key for the development of targeted cancer-preventative and -therapeutic interventions. Current models explaining inter- and intratumoral diversity are the cancer stem cell and the clonal evolution hypotheses. Although tumor initiation and progression are predominantly driven by acquired genetic alterations, recent data implicate a role for microenvironmental and epigenetic changes as well. Comprehensive unbiased studies of tumors and patient populations have significantly advanced our molecular understanding of breast cancer, but translating these findings into clinical practice remains a challenge.

Autocrine factors that sustain glioma invasion and paracrine biology in the brain microenvironment

Invasion is a defining hallmark of glioblastoma multiforme, just as metastasis characterizes other high-grade tumors. Glial tumors invariably recur due to the regrowth of invasive cells, which are unaffected by standard treatment modalities. Drivers of glioma invasion include autocrine signals propagated by secreted factors that signal through receptors on the tumor. These secreted factors are able to diffuse through the peritumoral stroma, thereby influencing parenchymal cells that surround the tumor mass. Here we describe various autocrine motility factors that are expressed by invasive glioma cells and explore the effects that they may have on normal cells present in the path of invasion. Conversely, normal brain parenchymal cells secrete ligands that can stimulate receptors on invasive glioma cells and potentially facilitate glioma invasion or create a permissive microenvironment for malignant progression. Parallel observations have been made for solid tumors of epithelial origin, in which parenchymal and stromal cells either support or suppress tumor invasion. Most autocrine and paracrine interactions involved in glioma invasion constitute known signaling systems in stages of central nervous system development that involve the migration of precursor cells that populate the developing brain. Key paracrine interactions between glioma cells and the brain microenvironment can influence glioma pathobiology and therefore contribute to its poor prognosis. Current therapies for glioma that could have an impact on paracrine communication between tumors and normal cells are discussed. We suggest that cells in the normal brain parenchyma be considered as potential targets for adjuvant therapies to control glioma growth because such cells are less likely to develop resistance than glioma cells.

Myoepithelial molecular markers in human breast carcinoma PMC42-LA cells are induced by extracellular matrix and stromal cells

The microenvironment plays a key role in the cellular differentiation of the two main cell lineages of the human breast, luminal epithelial, and myoepithelial. It is not clear, however, how the components of the microenvironment control the development of these cell lineages. To investigate how lineage development is regulated by 3-D culture and microenvironment components, we used the PMC42-LA human breast carcinoma cell line, which possesses stem cell characteristics. When cultured on a two-dimensional glass substrate, PMC42-LA cells formed a monolayer and expressed predominantly luminal epithelial markers, including cytokeratins 8, 18, and 19; E-cadherin; and sialomucin. The key myoepithelial-specific proteins alpha-smooth muscle actin and cytokeratin 14 were not expressed. When cultured within Engelbreth-Holm- Swarm sarcoma-derived basement membrane matrix (EHS matrix), PMC42-LA cells formed organoids in which the expression of luminal markers was reduced and the expression of other myoepithelial-specific markers (cytokeratin 17 and P-cadherin) was promoted. The presence of primary human mammary gland fibroblasts within the EHS matrix induced expression of the key myoepithelial-specific markers, alpha-smooth muscle actin and cytokeratin 14. Immortalized human skin fibroblasts were less effective in inducing expression of these key myoepithelial-specific markers. Confocal dual-labeling showed that individual cells expressed luminal or myoepithelial proteins, but not both. Conditioned medium from the mammary fibroblasts was equally effective in inducing myoepithelial marker expression. The results indicate that the myoepithelial lineage is promoted by the extracellular matrix, in conjunction with products secreted by breast-specific fibroblasts. Our results demonstrate a key role for the breast microenvironment in the regulation of breast lineage development.

Novel markers for differentiation of lobular and ductal invasive breast carcinomas by laser microdissection and microarray analysis

Background

Invasive ductal and lobular carcinomas (IDC and ILC) are the most common histological types of breast cancer. Clinical follow-up data and metastatic patterns suggest that the development and progression of these tumors are different. The aim of our study was to identify gene expression profiles of IDC and ILC in relation to normal breast epithelial cells.

Methods

We examined 30 samples (normal ductal and lobular cells from 10 patients, IDC cells from 5 patients, ILC cells from 5 patients) microdissected from cryosections of ten mastectomy specimens from postmenopausal patients. Fifty nanograms of total RNA were amplified and labeled by PCR and in vitro transcription. Samples were analysed upon Affymetrix U133 Plus 2.0 Arrays. The expression of seven differentially expressed genes (CDH1, EMP1, DDR1, DVL1, KRT5, KRT6, KRT17) was verified by immunohistochemistry on tissue microarrays. Expression of ASPN mRNA was validated by in situ hybridization on frozen sections, and CTHRC1, ASPN and COL3A1 were tested by PCR.

Results

Using GCOS pairwise comparison algorithm and rank products we have identified 84 named genes common to ILC versus normal cell types, 74 named genes common to IDC versus normal cell types, 78 named genes differentially expressed between normal ductal and lobular cells, and 28 named genes between IDC and ILC. Genes distinguishing between IDC and ILC are involved in epithelial-mesenchymal transition, TGF-beta and Wnt signaling. These changes were present in both tumor types but appeared to be more prominent in ILC. Immunohistochemistry for several novel markers (EMP1, DVL1, DDR1) distinguished large sets of IDC from ILC.

Conclusion

IDC and ILC can be differentiated both at the gene and protein levels. In this study we report two candidate genes, asporin (ASPN) and collagen triple helix repeat containing 1 (CTHRC1) which might be significant in breast carcinogenesis. Besides E-cadherin, the proteins validated on tissue microarrays (EMP1, DVL1, DDR1) may represent novel immunohistochemical markers helpful in distinguishing between IDC and ILC. Further studies with larger sets of patients are needed to verify the gene expression profiles of various histological types of breast cancer in order to determine molecular subclassifications, prognosis and the optimum treatment strategies.

Decreased expression of annexin A1 is correlated with breast cancer development and progression as determined by a tissue microarray analysis

Annexin A1 (ANXA1) is a calcium- and phospholipid-binding protein and a known mediator of glucocorticoid-regulated inflammatory responses. Using a combined multiple high-throughput approach, we recently identified a reduced expression of ANXA1 in human breast cancer. The finding was confirmed at the gene level by quantitative reverse transcription-polymerase chain reaction and at the protein level by immunohistochemical staining of normal, benign, and malignant breast tissues. In this study, we constructed and used a high-density human breast cancer tissue microarray to characterize the expressional pattern of ANXA1 according to histopathologies. The tissue microarray contains 1,158 informative breast tissue cores of different histologies including normal tissues, hyperplasia, in situ and invasive tumors, and lymph node metastases. Our results showed that there was a significant decrease in glandular expression of ANXA1 in ductal carcinoma in situ and invasive ductal carcinoma compared with either normal breast tissue or hyperplasia (P < .0001). Moreover, in benign breast tissue, myoepithelial cells showed strong expression of ANXA1. There was a decrease of ANXA1 expression in myoepithelial cells in ductal carcinoma in situ lesions compared with the same cell population in either normal or hyperplastic lesions. These results suggest that suppressed ANXA1 expression in breast tissue is correlated with breast cancer development and progression.

Mechanisms of disease: breast tumor pathogenesis and the role of the myoepithelial cell

Breast cancer and precancer cells are influenced by important paracrine regulation from the breast microenvironment, which might be as great a determinant of breast cancer behavior as the specific oncogenic or tumor-suppressive alterations occurring within malignant breast cells. Myoepithelial cells exert profound effects on breast tumor cell behavior, and lie in juxtaposition to abnormally proliferating breast epithelial cells in precancerous disease states such as ductal carcinoma in situ (DCIS). Myoepithelial cells also form a natural border separating breast epithelial cells from stromal angiogenesis. These anatomical relationships suggest that myoepithelial cells might inhibit both the progression of DCIS to invasive breast cancer, and carcinoma-induced angiogenesis. Our ability to study myoepithelial cells has been fostered by recent technical advances in cell selection and sorting procedures, improved selective media, and high throughput technologies, which are able to assess the gene and protein expression profiles within cells. In addition, the establishment of a number of immortalized cell lines and xenografts of myoepithelial cells derived from benign human myoepithelial tumors of diverse sources has provided a self-renewing cell source through which to study the phenotype of myoepithelial cells. Studies of primary and immortalized myoepithelial cell lines indicate that these cells exhibit a natural tumor suppressor function. Functional studies show that these cells have anti-invasive and antiangiogenic phenotypes.

Immunoprofile of reactive salivary myoepithelial cells in intraductal areas of carcinoma ex-pleomorphic adenoma

The myoepithelial cell (MC) is a component of various secretory glands, including salivary glands. Besides its function, a tumor suppressor and a tumor facilitating functions have been attributed to this cell. We investigated the immunoprofile of benign MC in intraductal areas of carcinoma ex-pleomorphic adenoma (CXPA), comparing them with the MC in duct-like areas of pleomorphic adenoma, origin of the malignant tumor. Antibodies against myoepithelial markers-CK14, alpha-SMA, calponin, P63, CD10, and D2-40-plus laminin and maspin was applied in four selected cases of intracapsular and minimal invasive CXPA with only luminal differentiation presenting areas of intraductal carcinoma. The immunohistochemical reactions of all the antibodies showed stronger staining in benign MC surrounding the malignant epithelial cells than in benign MC in duct-like areas of pleomorphic adenoma, thus revealing that in the malignization process the benign MC become differentiated and produce important proteins related to the tumor suppressor function.

P190-B Rho GTPase-activating protein overexpression disrupts ductal morphogenesis and induces hyperplastic lesions in the developing mammary gland

p190-B Rho GTPase activating protein is essential for mammary gland development because p190-B deficiency prevents ductal morphogenesis. To investigate the role of p190-B during distinct stages of mammary gland development, tetracycline-regulatable p190-B-overexpressing mice were generated. Short-term induction of p190-B in the developing mammary gland results in abnormal terminal end buds (TEBs) that exhibit aberrant budding off the neck, histological anomalies, and a markedly thickened stroma. Overexpression of p190-B throughout postnatal development results in increased branching, delayed ductal elongation, and disorganization of the ductal tree. Interestingly, overexpression of p190-B during pregnancy results in hyperplastic lesions. Several cellular and molecular alterations detected within the aberrant TEBs may contribute to these phenotypes. Signaling through the IGF pathway is altered, and the myoepithelial cell layer is discontinuous at sites of aberrant budding. An increase in collagen and extensive infiltration of macrophages, which have recently been implicated in branching morphogenesis, is observed in the stroma surrounding the p190-B-overexpressing TEBs. We propose that the stromal response, disruption of the myoepithelial layer, and alterations in IGF signaling in the p190-B-overexpressing mice impact the TEB architecture, leading to disorganization and increased branching of the ductal tree. Moreover, we suggest that alterations in tissue architecture and the adjacent stroma as a consequence of p190-B overexpression during pregnancy leads to loss of growth control and the formation of hyperplasia. These data demonstrate that precise control of p190-B Rho GTPase-activating protein activity is critical for normal branching morphogenesis during mammary gland development.

Establishment of the epithelial-specific transcriptome of normal and malignant human breast cells based on MPSS and array expression data

INTRODUCTION

Diverse microarray and sequencing technologies have been widely used to characterise the molecular changes in malignant epithelial cells in breast cancers. Such gene expression studies to identify markers and targets in tumour cells are, however, compromised by the cellular heterogeneity of solid breast tumours and by the lack of appropriate counterparts representing normal breast epithelial cells.

METHODS

Malignant neoplastic epithelial cells from primary breast cancers and luminal and myoepithelial cells isolated from normal human breast tissue were isolated by immunomagnetic separation methods. Pools of RNA from highly enriched preparations of these cell types were subjected to expression profiling using massively parallel signature sequencing (MPSS) and four different genome wide microarray platforms. Functional related transcripts of the differential tumour epithelial transcriptome were used for gene set enrichment analysis to identify enrichment of luminal and myoepithelial type genes. Clinical pathological validation of a small number of genes was performed on tissue microarrays.

RESULTS

MPSS identified 6,553 differentially expressed genes between the pool of normal luminal cells and that of primary tumours substantially enriched for epithelial cells, of which 98% were represented and 60% were confirmed by microarray profiling. Significant expression level changes between these two samples detected only by microarray technology were shown by 4,149 transcripts, resulting in a combined differential tumour epithelial transcriptome of 8,051 genes. Microarray gene signatures identified a comprehensive list of 907 and 955 transcripts whose expression differed between luminal epithelial cells and myoepithelial cells, respectively. Functional annotation and gene set enrichment analysis highlighted a group of genes related to skeletal development that were associated with the myoepithelial/basal cells and upregulated in the tumour sample. One of the most highly overexpressed genes in this category, that encoding periostin, was analysed immunohistochemically on breast cancer tissue microarrays and its expression in neoplastic cells correlated with poor outcome in a cohort of poor prognosis estrogen receptor-positive tumours.

CONCLUSION

Using highly enriched cell populations in combination with multiplatform gene expression profiling studies, a comprehensive analysis of molecular changes between the normal and malignant breast tissue was established. This study provides a basis for the identification of novel and potentially important targets for diagnosis, prognosis and therapy in breast cancer.

Typical medullary breast carcinomas have a basal/myoepithelial phenotype

Medullary breast cancer (MBC) is a rare, diagnostically difficult, pathological subtype. Despite being high grade, it has a good prognosis. MBC patients have an excess of BRCA1 germ-line mutation and reliable identification of MBC could help to identify patients at risk of carrying germline BRCA1 mutations or in whom chemotherapy could be avoided. The aim of this study was therefore to improve diagnosis by establishing an MBC protein expression profile using immunohistochemistry (IHC) on tissue-microarrays (TMA). Using a series of 779 breast carcinomas ('EC' set), diagnosed initially as MBC, a double-reading session was carried out by several pathologists on all of the histological material to establish the diagnosis as firmly as possible using a 'medullary score'. Only MBCs with high scores, i.e. typical MBC (TMBC) (n=44) and non-TMBC grade III with no or low scores (n=160), were included in the IHC study. To validate the results obtained on this first set, a control series of TMBC (n=17) and non-MBC grade III cases (n=140) ('IPC' set) was studied. The expression of 18 proteins was studied in the 61 TMBCs and 300 grade III cases from the two sets. The global intra-observer concordance of the first reading for the diagnosis of TMBC was 94%, with almost perfect kappa (kappa) of 0.815. TMBC was characterized by a high degree of basal/myoepithelial differentiation. In multivariate analysis with logistic regression, TMBC was defined by the association of P-cadherin (R=2.29), MIB1 > 50 (R=3.80), ERBB2 negativity (R=2.24) and p53 positivity (RR=1.45).

Modelling glandular epithelial cancers in three-dimensional cultures

Little is known about how the genotypic and molecular abnormalities associated with epithelial cancers actually contribute to the histological phenotypes observed in tumours in vivo. 3D epithelial culture systems are a valuable tool for modelling cancer genes and pathways in a structurally appropriate context. Here, we review the important features of epithelial structures grown in 3D basement membrane cultures, and how such models have been used to investigate the mechanisms associated with tumour initiation and progression.

Myoepithelial cells: good fences make good neighbors

The mammary gland consists of an extensively branched ductal network contained within a distinctive basement membrane and encompassed by a stromal compartment. During lactation, production of milk depends on the action of the two epithelial cell types that make up the ductal network: luminal cells, which secrete the milk components into the ductal lumen; and myoepithelial cells, which contract to aid in the ejection of milk. There is increasing evidence that the myoepithelial cells also play a key role in the organizational development of the mammary gland, and that the loss and/or change of myoepithelial cell function is a key step in the development of breast cancer. In this review we briefly address the characteristics of breast myoepithelial cells from human breast and mouse mammary gland, how they function in normal mammary gland development, and their recently appreciated role in tumor suppression.

Do myoepithelial cells hold the key for breast tumor progression?

Mammary myoepithelial cells have been a neglected facet of breast cancer biology, largely ignored since they have been considered to be less important for tumorigenesis than luminal epithelial cells from which most of breast carcinomas are thought to arise. In recent years as our knowledge of stem cell biology and the cellular microenvironment has been increasing, myoepithelial cells are slowly starting to gain more attention. Emerging data raise the hypothesis whether myoepithelial cells play a key role in breast tumor progression by regulating the in situ to invasive carcinoma transition and that myoepithelial cells are part of the mammary stem cell niche. Paracrine interactions between myoepithelial and luminal epithelial cells are known to be important for regulation of cell cycle progression, establishing epithelial cell polarity, and inhibiting cell migration and invasion. Based on these functions, normal mammary myoepithelial cells have been called "natural tumor suppressors." However, during tumor progression myoepithelial cells seem to loose these properties, and eventually this cell population diminishes as tumors become invasive. Better understanding of myoepithelial cell function and their role in tumor progression may lead to their exploitation for cancer therapeutic and preventative measures.

Myoepithelial cells: autocrine and paracrine suppressors of breast cancer progression

Host cellular paracrine regulation of tumor progression is an important determinant of tumor biology but one cell that has been ignored in this regulation is the myoepithelial cell. Myoepithelial cells surround normal ducts and precancerous lesions, especially of the breast and form a natural border separating proliferating epithelial cells from proliferating endothelial cells (angiogenesis). Myoepithelial cells may thus negatively regulate tumor invasion and metastasis. Whereas epithelial cells are susceptible targets for transforming events, myoepithelial cells are resistant. Therefore, it can be said that myoepithelial cells function as both autocrine as well as paracrine tumor suppressors. Our laboratory has found that myoepithelial cells secrete a number of suppressor molecules including high amounts of diverse proteinase inhibitors and angiogenic inhibitors but low amounts of proteinases and angiogenic factors compared to common malignant cell lines. This observation has been made in vitro, in mice, and in humans and suggests that myoepithelial cells exert pleiotropic suppressive effects on tumor progression. The gene expression profile of myoepithelial cells may explain the pronounced anti-invasive and anti-angiogenic effects of myoepithelial cells on carcinoma cells and may also account for the reduced malignancy of myoepithelial tumors, which are devoid of appreciable angiogenesis and invasive behavior.

Differentiation of tumours of ductal and lobular origin: II. Genomics of invasive ductal and lobular breast carcinomas

Breast cancer is considered to be a multifactorial disorder caused by both genetic and non-genetic factors. Different histological types of breast cancer differ in response to treatment and may have a divergent clinical course. Breast tissue is heterogeneous, with components of epithelial, mesenchymal, endothelial and lymphopoietic derivation. The genetic heterogeneity of invasive breast cancer is reflected by the wide spectrum of histological types and differentiation grades. Nevertheless, the influences of these cell types on the tumour's total pattern of gene expression can be estimated analytically. Microarrays permit total tissue analysis and provide a stable molecular portrait of tumours. Some investigations suggest differences in the gene expression profiling for ductal and lobular carcinomas. It has been reported that inactivating mutations of the E-cadherin gene are very frequent in infiltrating lobular breast carcinomas. Other than altered expression of E-cadherin, little is known about the underlying biology that distinguishes ductal and lobular tumour subtypes. However, about 8 genes have been identified differentially which are expressed in lobular and ductal cancers: E-CD, survivin, cathepsin B, TPI1, SPRY1, SCYA14, TFAP2B, and thrombospondin 4, osteopontin, HLA-G, and CHC1. Expression profiling of breast cancers can be used diagnostically to distinguish individual histologic subclassifications and may guide the selection of target therapeutics. However, future approaches will need to include methods for high throughput clinical validation and the ability to analyze microscopic samples.