Extracellular matrix components in breast carcinomas

Relative Quantification of Proteins in Formalin-Fixed Paraffin-Embedded Breast Cancer Tissue Using Multiplexed Mass Spectrometry Assays

The identification of clinically relevant biomarkers represents an important challenge in oncology. This problem can be addressed with biomarker discovery and verification studies performed directly in tumor samples using formalin-fixed paraffin-embedded (FFPE) tissues. However, reliably measuring proteins in FFPE samples remains challenging. Here, we demonstrate the use of liquid chromatography coupled to multiple reaction monitoring mass spectrometry (LC-MRM/MS) as an effective technique for such applications. An LC-MRM/MS method was developed to simultaneously quantify hundreds of peptides extracted from FFPE samples and was applied to the targeted measurement of 200 proteins in 48 triple-negative, 19 HER2-overexpressing, and 20 luminal A breast tumors. Quantitative information was obtained for 185 proteins, including known markers of breast cancer such as HER2, hormone receptors, Ki-67, or inflammation-related proteins. LC-MRM/MS results for these proteins matched immunohistochemistry or chromogenic in situ hybridization data. In addition, comparison of our results with data from the literature showed that several proteins representing potential biomarkers were identified as differentially expressed in triple-negative breast cancer samples. These results indicate that LC-MRM/MS assays can reliably measure large sets of proteins using the analysis of surrogate peptides extracted from FFPE samples. This approach allows to simultaneously quantify the expression of target proteins from various pathways in tumor samples. LC-MRM/MS is thus a powerful tool for the relative quantification of proteins in FFPE tissues and for biomarker discovery.

Extracellular Matrix Derived from High Metastatic Human Breast Cancer Triggers Epithelial-Mesenchymal Transition in Epithelial Breast Cancer Cells through αvβ3 Integrin

Alterations in the composition and architecture of the extracellular matrix (ECM) can influence cancer growth and dissemination. During epithelial-mesenchymal transition (EMT), epithelial cells assume a mesenchymal cell phenotype, changing their adhesion profiles from cell-cell contacts to cell-matrix interactions, contributing to metastasis. Breast cancer cells present at different stages of differentiation, producing distinct ECMs in the same tumor mass. However, the contribution of ECM derived from metastatic tumor cells to EMT is unclear. Here, we showed the mechanisms involved in the interaction of MCF-7, a low-metastatic, epithelial breast cancer cell line, with the ECM produced by a high metastatic breast tumor cell, MDA-MB-231 (MDA-ECM). MDA-ECM induced morphological changes in MCF-7 cells, decreased the levels of E-cadherin, up-regulated mesenchymal markers, and augmented cell migration. These changes were accompanied by the activation of integrin-associated signaling, with increased phosphorylation of FAK, ERK, and AKT and activation canonical TGF-β receptor signaling, enhancing phosphorylation of SMAD2 and SMAD4 nuclear translocation in MCF-7 cells. Treatment with Kistrin (Kr), a specific ligand of integrin αvβ3 EMT induced by MDA-ECM, inhibited TGF-β receptor signaling in treated MCF-7 cells. Our results revealed that after interaction with the ECM produced by a high metastatic breast cancer cell, MCF-7 cells lost their characteristic epithelial phenotype undergoing EMT, an effect modulated by integrin signaling in crosstalk with TGF-β receptor signaling pathway. The data evidenced novel potential targets for antimetastatic breast cancer therapies.

Baicalein inhibits fibronectin-induced epithelial-mesenchymal transition by decreasing activation and upregulation of calpain-2

The extracellular matrix protein fibronectin (FN) facilitates tumorigenesis and the development of breast cancer. Inhibition of the FN-induced cellular response is a potential strategy for breast cancer treatment. In the present study, we investigated the effects of the flavonoid baicalein on FN-induced epithelial–mesenchymal transition (EMT) in MCF-10A breast epithelial cells and in a transgenic mouse MMTV-polyoma middle T antigen breast cancer model (MMTV-PyMT). Baicalein inhibited FN-induced migration, invasion, and F-actin remodeling. Baicalein also suppressed FN-induced downregulation of the epithelial markers E-cadherin and ZO-1 and upregulation of the mesenchymal markers N-cadherin, vimentin, and Snail. Further investigation revealed that calpain-2 was involved in baicalein suppression of FN-induced EMT. Baicalein significantly decreased FN-enhanced calpain-2 expression and activation by suppressing its plasma membrane localization, substrate cleavage, and degradation of its endogenous inhibitor calpastatin. Overexpression of calpain-2 in MCF-10A cells by gene transfection partially blocked the inhibitory effect of baicalein on FN-induced EMT changes. In addition, baicalein inhibited calpain-2 by decreasing FN-increased intracellular calcium ion levels and extracellular signal-regulated protein kinases activation. Baicalein significantly decreased tumor onset, growth, and pulmonary metastasis in a spontaneous breast cancer MMTV-PyMT mouse model. Baicalein also reduced the expression of FN, calpain-2, and vimentin, but increased E-cadherin expression in MMTV-PyMT mouse tumors. Overall, these results revealed that baicalein markedly inhibited FN-induced EMT by inhibiting calpain-2, thus providing novel insights into the pharmacological action and mechanism of baicalein. Baicalein may therefore possess therapeutic potential for the treatment of breast cancer though interfering with extracellular matrix–cancer cell interactions.

ColXα1 is a stromal component that colocalizes with elastin in the breast tumor extracellular matrix

The tumor microenvironment regulates tissue development and homeostasis, and its dysregulation contributes to neoplastic progression. Increased expression of type X collagen α‐1 (ColXα1) in tumor‐associated stroma correlates with poor pathologic response to neoadjuvant chemotherapy in estrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2)‐positive breast cancers. Evaluation of ColXα1 expression patterns suggests a potential connection with elastin fibers. To investigate the possible interaction between ColXα1 and elastin, we evaluated the expression of ColXα1 in relation to elastin fibers in normal breast tissue, ductal carcinoma in situ, and invasive breast carcinomas at cellular and subcellular levels. Our findings demonstrate that ColXα1 colocalizes with elastin in invasive breast cancer‐associated stroma by immunohistochemistry, immunofluorescence, and electron microscopy. In 212 invasive breast carcinomas, this complex was aberrantly and selectively expressed in tumor extracellular matrix in 79% of ER+/HER2−, 80% of ER+/HER2+, 76% of ER−/HER2+, and 58% of triple negative breast cancers. In contrast, ColXα1 was generally absent, while elastin was present perivascularly in normal breast tissue. ColXα1 and elastin were coexpressed in 58% of ductal carcinoma in situ (DCIS) in periductal areas. In mass‐forming DCIS with desmoplastic stroma, the complex was intensely expressed in periductal areas as well as within the tumor‐associated stroma in all cases. Our data suggest that the breast carcinoma neoplastic process may involve aberrant expression of ColXα1 and elastin in the tumor microenvironment emerging early at the DCIS stage. Enrichment of these complexes in tumor‐associated stroma may represent a stromal signature indicative of intrinsic differences between breast cancers. These findings shed light on investigation into the role of aberrant collagen complex expression in tumorigenesis and tumor progression which may be leveraged in therapeutic and theranostic applications.

Inhibition of FASN and ERα signalling during hyperglycaemia-induced matrix-specific EMT promotes breast cancer cell invasion via a caveolin-1-dependent mechanism

Since disturbed metabolic conditions such as obesity and diabetes can be critical determinants of breast cancer progression and therapeutic failure, we aimed to determine the mechanism responsible for their pro-oncogenic effects. Using non-invasive, epithelial-like ERα-positive MCF-7 and T47D human breast cancer cells we found that hyperglycaemia induced epithelial to mesenchymal transition (EMT), a key programme responsible for the development of metastatic disease. This was demonstrated by loss of the epithelial marker E-cadherin together with increases in mesenchymal markers such as vimentin, fibronectin and the transcription factor SLUG, together with an enhancement of cell growth and invasion. These phenotypic changes were only observed with cells grown on fibronectin and not with those plated on collagen. Analyzing metabolic parameters, we found that hyperglycaemia-induced, matrix-specific EMT promoted the Warburg effect by upregulating glucose uptake, lactate release and specific glycolytic enzymes and transporters. We showed that silencing of fatty acid synthase (FASN) and the downstream ERα, which we showed previously to mediate hyperglycaemia-induced chemoresistance in these cells, resulted in suppression of cell growth: however, this also resulted in a dramatic enhancement of cell invasion and SLUG mRNA levels via a novel caveolin-1-dependent mechanism.

Multiple Cryptic Binding Sites are Necessary for Robust Fibronectin Assembly: An In Silico Study

The mechanism of assembly of the extracellular matrix protein fibronectin (FN) into elastic, insoluble fibrils is still poorly understood. FN fibrillogenesis requires cell-generated forces, which expose cryptic FN-FN binding sites buried in FN Type III domains. The number and location of cryptic binding sites have been debated, but experimental evidence suggests multiple domains may contain FN-FN binding sites. The requirement of cell-dependent forces to generate FN fibrils restricts investigation of the mechanism of assembly. To address this, we use a recently developed biophysical model of fibrillogenesis to test competing hypotheses for the location and number of cryptic FN-FN binding sites and quantify the effect of these molecular alterations on assembled FN fibril properties. Simulations predict that a single FN-FN binding site facilitates either negligible fibrillogenesis or produces FN fibrils that are neither robust nor physiological. However, inclusion of multiple FN-FN binding sites predicts robust fibrillogenesis, which minimally depends on individual domain properties. Multiple FN-FN binding site models predict a heterogeneous fibril population that contains two distinct phenotypes with unique viscoelastic properties, which we speculate may play a key role in generating heterogeneous mechanical signaling in the extracellular matrix of developing and regenerating tissues.

Fibronectin fibrils regulate TGF-β1-induced Epithelial-Mesenchymal Transition

Epithelial-Mesenchymal Transition (EMT) is a dynamic process through which epithelial cells transdifferentiate from an epithelial phenotype into a mesenchymal phenotype. Previous studies have demonstrated that both mechanical signaling and soluble growth factor signaling facilitate this process. One possible point of integration for mechanical and growth factor signaling is the extracellular matrix. Here we investigate the role of the extracellular matrix (ECM) protein fibronectin (FN) in this process. We demonstrate that inhibition of FN fibrillogenesis blocks activation of the Transforming Growth Factor-Beta (TGF-β) signaling pathway via Smad2 signaling, decreases cell migration and ultimately leads to inhibition of EMT. Results show that soluble FN, FN fibrils, or increased contractile forces are insufficient to independently induce EMT. We further demonstrate that inhibition of latent TGF-β1 binding to FN fibrils via either a monoclonal blocking antibody against the growth factor binding domain of FN or through use of a FN deletion mutant that lacks the growth factor binding domains of FN blocks EMT progression, indicating a novel role for FN in EMT in which the assembly of FN fibrils serves to localize TGF-β1 signaling to drive EMT.

Breast cancer stromal elastosis is associated with mammography screening detection, low Ki67 expression and favourable prognosis in a population-based study

Background

Mammography screen-detected breast cancers have a better prognosis than predicted from established prognostic markers. A search for additional features that are characteristic for these tumours and their prognosis is needed to reduce overtreatment, a recognized challenge in breast cancer patient management today. Here, we have investigated the occurrence and importance of tumour elastosis.

Methods

We performed a population based retrospective study of breast cancers detected in the Norwegian Breast Cancer Screening Programme in Vestfold County during 2004–2009. In total, 197 invasive screen-detected cancers and 75 interval cancers in patients aged 50–69 years were compared with regard to standard clinico-pathological parameters and tumour shape, as well as ER, PR, HER2 and Ki67 expression. In particular, the presence of elastotic material in tumours was graded on a 4-tiered scale (score 0–3).

Results

Screen-detected cancers had a significantly higher content of stromal elastosis than interval cancers (p < 0.001). High content of elastosis (score 3) correlated strongly with stellate tumour shape, low histological grade, and ER+/HER2- status. Further, high elastosis score was significantly associated with lower Ki67 expression. In survival analyses, cases with high elastosis demonstrated increased recurrence free (p = 0.03) and disease-specific survival (p = 0.11) compared to cases with low elastosis.

Conclusion

There is a strong correlation between the presence of tumour elastosis, stellate tumour shape and mammography detection of breast cancers. To our knowledge, this is the first time elastosis has been studied in relation to breast cancer detection method. Presence of elastosis is associated with low tumour cell proliferation (Ki67) and a good prognosis.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_230

Tumors perturbing extracellular matrix biosynthesis. The case of von Recklinghausen's disease

This is a short review of neurofibromatosis-1 or von Recklinghausen's disease, due to a loss of function mutation of the gene neurofibromin-1, which normally inhibits the Ras MAPK-pathways. Among its symptoms, the strong oversynthesis of several collagen types designates this disease as producing a deregulation of extracellular matrix biosynthesis involved in tumor formation. Up to about 40% of the skin tumors consist of collagens. A short summary of the clinical manifestations and pathological and genetic mechanisms are also described.

TGFβ and matrix-regulated epithelial to mesenchymal transition

BACKGROUND

The progression of cancer through stages that guide a benign hyperplastic epithelial tissue towards a fully malignant and metastatic carcinoma, is driven by genetic and microenvironmental factors that remodel the tissue architecture. The concept of epithelial-mesenchymal transition (EMT) has evolved to emphasize the importance of plastic changes in tissue architecture, and the cross-communication of tumor cells with various cells in the stroma and with specific molecules in the extracellular matrix (ECM).

SCOPE OF THE REVIEW

Among the multitude of ECM-embedded cytokines and the regulatory potential of ECM molecules, this article focuses on the cytokine transforming growth factor β (TGFβ) and the glycosaminoglycan hyaluronan, and their roles in cancer biology and EMT. For brevity, we concentrate our effort on breast cancer.

MAJOR CONCLUSIONS

Both normal and abnormal TGFβ signaling can be detected in carcinoma and stromal cells, and TGFβ-induced EMT requires the expression of hyaluronan synthase 2 (HAS2). Correspondingly, hyaluronan is a major constituent of tumor ECM and aberrant levels of both hyaluronan and TGFβ are thought to promote a wounding reaction to the local tissue homeostasis. The link between EMT and metastasis also involves the mesenchymal-epithelial transition (MET). ECM components, signaling networks, regulatory non-coding RNAs and epigenetic mechanisms form the network of regulation during EMT-MET.

GENERAL SIGNIFICANCE

Understanding the mechanism that controls epithelial plasticity in the mammary gland promises the development of valuable biomarkers for the prognosis of breast cancer progression and even provides new ideas for a more integrative therapeutic approach against disease. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

HAS2 and CD44 in breast tumorigenesis

Metastatic spread of breast cancer cells, facilitated by the epithelial-mesenchymal transition (EMT) process, is responsible for the majority of breast cancer mortality. Increased levels of hyaluronan due to deregulation of hyaluronan-synthesizing enzymes, like HAS2, and expression of CD44, the key receptor for hyaluronan, are correlated to poor outcome of patients with basal-like breast cancer. TGFβ induces HAS2 and CD44, both of which are required in the course of efficient TGFβ-induced EMT processes by mammary epithelial cells. Elucidation of the molecular mechanisms underlying tumor-stroma interactions in breast cancer including the regulation of HAS2 and CD44 expression may contribute to the development of better strategies to treat breast cancer patients.

Mammary epithelial cell interactions with fibronectin stimulate epithelial-mesenchymal transition

In the mammary gland, the stromal extracellular matrix (ECM) undergoes dramatic changes during development and in tumorigenesis. For example, normal adult breast tissue is largely devoid of the ECM protein fibronectin (FN) whereas high FN levels have been detected in the stroma of breast tumors. FN is an established marker for epithelial-mesenchymal transition (EMT), which occurs during development and has been linked to cancer. During EMT, epithelial cell adhesion switches from cell-cell contacts to mainly cell-ECM interactions raising the possibility that FN may have a role in promoting this transition. Using MCF-10A mammary epithelial cells, we show that exposure to exogenous FN induces an EMT response including up-regulation of the EMT markers FN, Snail, N-cadherin, vimentin, the matrix metalloprotease MMP2, α-smooth muscle actin, and phospho-Smad2 as well as acquisition of cell migratory behavior. FN-induced EMT depends on Src kinase and ERK/MAP kinase signaling but not on the immediate early gene EGR-1. FN initiates EMT under serum-free conditions; this response is partially reversed by a TGFβ neutralizing antibody suggesting that FN enhances the effect of endogenous TGFβ. EMT marker expression is up-regulated in cells on a fragment of FN containing the integrin-binding domain but not other domains. Differences in gene expression between FN and MG are maintained with addition of a sub-threshold level of TGFβ1. Together, these results show that cells interacting with FN are primed to respond to TGFβ. The ability of FN to induce EMT shows an active role for the stromal ECM in this process and supports the notion that the increased levels of FN observed in breast tumors facilitate tumorigenesis.

Interstitial Fluid and Lymph Formation and Transport: Physiological Regulation and Roles in Inflammation and Cancer

The interstitium describes the fluid, proteins, solutes, and the extracellular matrix (ECM) that comprise the cellular microenvironment in tissues. Its alterations are fundamental to changes in cell function in inflammation, pathogenesis, and cancer. Interstitial fluid (IF) is created by transcapillary filtration and cleared by lymphatic vessels. Herein we discuss the biophysical, biomechanical, and functional implications of IF in normal and pathological tissue states from both fluid balance and cell function perspectives. We also discuss analysis methods to access IF, which enables quantification of the cellular microenvironment; such methods have demonstrated, for example, that there can be dramatic gradients from tissue to plasma during inflammation and that tumor IF is hypoxic and acidic compared with subcutaneous IF and plasma. Accumulated recent data show that IF and its convection through the interstitium and delivery to the lymph nodes have many and diverse biological effects, including in ECM reorganization, cell migration, and capillary morphogenesis as well as in immunity and peripheral tolerance. This review integrates the biophysical, biomechanical, and biological aspects of interstitial and lymph fluid and its transport in tissue physiology, pathophysiology, and immune regulation.

Fibronectin expression modulates mammary epithelial cell proliferation during acinar differentiation

The mammary gland consists of a polarized epithelium surrounded by a basement membrane matrix that forms a series of branching ducts ending in hollow, sphere-like acini. Essential roles for the epithelial basement membrane during acinar differentiation, in particular laminin and its integrin receptors, have been identified using mammary epithelial cells cultured on a reconstituted basement membrane. Contributions from fibronectin, which is abundant in the mammary gland during development and tumorigenesis, have not been fully examined. Here, we show that fibronectin expression by mammary epithelial cells is dynamically regulated during the morphogenic process. Experiments with synthetic polyacrylamide gel substrates implicate both specific extracellular matrix components, including fibronectin itself, and matrix rigidity in this regulation. Alterations in fibronectin levels perturbed acinar organization. During acinar development, increased fibronectin levels resulted in overproliferation of mammary epithelial cells and increased acinar size. Addition of fibronectin to differentiated acini stimulated proliferation and reversed growth arrest of mammary epithelial cells negatively affecting maintenance of proper acinar morphology. These results show that expression of fibronectin creates a permissive environment for cell growth that antagonizes the differentiation signals from the basement membrane. These effects suggest a link between fibronectin expression and epithelial cell growth during development and oncogenesis in the mammary gland.

The effect of cell-matrix interactions and aging on the malignant process

The malignant process, transformation of normal cells, proliferation, and metastasis formation, was considered as if originating from one single cell. Although the intrinsic mechanisms of transformation from the normal to the malignant state were both confirmed, an increasing body of evidence points to the surrounding matrix and cell-matrix interactions as major players in this process. Some of the most important arguments in favor of this contention are cited and commented in this chapter. Another important question concerns the relationship between the aging process and malignant transformation. A few decades ago, the frequency of clinically manifest tumors of several organs and tissues appeared to increase with age. As, however, average life expectancy increased rapidly over the last decades, clinical frequency of malignant tumors did not follow this tendency. It was argued that late in life the malignant process appears to decline. This justly inspired several teams to study the relationship between cellular senescence and malignant transformation. This is now an actively growing field which deserves special attention. Some of the pertinent experimental and theoretical arguments in favor of an antioncogene-mediated switch between these two processes are also reviewed with the caveat that this important and new subject of basic and clinical research on the malignant process is just at its beginning. It will certainly take an increasing importance during the coming years and decades with the hope to contribute to answer one of the most burning questions concerning the aging process: will life expectancy continue to increase linearly as predicted by some gerontologists, or will life expectancy level off or even decline as predicted by other epidemiologists. The relationship between cellular senescence and malignant transformation will play in this respect an important role.

Microenvironment of the involuting mammary gland mediates mammary cancer progression

Breast cancer diagnosed after a completed pregnancy has higher metastatic potential and therefore a much poorer prognosis. We hypothesize that following pregnancy the process of mammary gland involution, which returns the gland to its pre-pregnant state, co-opts some of the programs of wound healing. The pro-inflammatory milieu that results, while physiologically normal, promotes tumor progression. In this review, the similarities between mammary gland involution after cessation of milk-production and pathological tissue remodeling are discussed in light of emerging data demonstrating a role for pathological tissue remodeling in cancer.

Dystroglycan expression is reduced during prostate tumorigenesis and is regulated by androgens in prostate cancer cells

Prostate cancer, the most frequently diagnosed cancer in Western men, can display a high variability in term of clinical aggressiveness and prognosis and none of the available markers is able to accurately predict its clinical course. Dystroglycan (DG), a non-integrin adhesion molecule, is a complex formed by two subunits, alpha- and beta-DG, which bind to extracellular matrix molecules and cytoskeleton, respectively. DG expression is frequently reduced in human cancers and has been related to tumor grade and aggressiveness. This study investigated the role of DG in human prostate tumorigenesis and its suitability as a prognostic marker. The expression level of extracellular alpha-DG subunit was frequently reduced in human prostate cancer cell lines and primary tumors and the percentage of positive tumor cells was significantly further decreased in vivo following androgen ablation therapy (median = 1%) compared to pre-treatment samples (median = 28%). A significant relationship was observed between alpha-DG staining on the post-treatment samples and tumor recurrence. A dose- and time-dependent decrease of DG expression also occurred in human prostate cancer cells following treatment with the anti-androgen flutamide. Stable expression of an exogenous DG cDNA in the LNCaP human prostate carcinoma cell line resulted in a marked inhibition of both anchorage-dependent and independent growth and of the in vivo tumorigenicity. These findings confirm and extend previous evidence that disturbances in the function of the DG complex might contribute to the definition of the malignant behavior of prostate cancer cells and suggest that androgens might regulate DG expression in these cells.

Analysis of dystroglycan regulation and functions in mouse mammary epithelial cells and implications for mammary tumorigenesis

Abnormalities in the interactions of cells with the extracellular matrix (ECM) play an important role in the development and progression of many types of cancer and are a hallmark of malignant transformation. The dystroglycan (DG) complex is a transmembrane glycoprotein that forms a continuous link from the ECM to the actin cytoskeleton, providing structural integrity and perhaps transducing signal, in a manner similar to integrins. Deregulated expression of DG has been reported in a variety of human malignancies and related to tumor differentiation and aggressiveness. In breast cancer, reduced DG expression has been associated with patient survival and with loss of differentiation of tumor cells. Limited data are available on DG physiology in epithelial cells. In this study, we used the HC11 spontaneously immortalized murine mammary epithelial cells to study DG function(s) and regulation in normal cells. We found that expression of DG protein and mRNA is cell-cycle and cell-density regulated in these cells. Moreover, expression of both DG subunits increased upon lactogenic differentiation of the HC11 cells. The turnover of cell-surface-expressed DG was evaluated in the same cells and half-life of DG subunits was evaluated to be about 12 h. DG-specific small inhibitory RNAs were used to analyze the effects of a reduced expression of DG in these cells. Cells in which DG expression was suppressed were growth inhibited, accumulated in the S-phase of the cell cycle, failed to undergo lactogenic differentiation, and displayed an increase in the percentage of apoptotic cells. Moreover, changes were observed in the expression and/or activity of several molecules involved in cell growth control. These results demonstrate that DG expression is tightly regulated in normal mammary epithelial cells and support the hypothesis that DG is involved in several functions other than structural integrity in these cells. This finding provides new insight into the roles played by DG in epithelial cell physiology and will contribute to our understanding of its involvement in the process of epithelial cell transformation.