Evidence for a role of tumor-derived laminin-511 in the metastatic progression of breast cancer

ADAMTS18 deficiency associates extracellular matrix dysfunction with a higher risk of HER2-positive mammary tumorigenesis and metastasis

BACKGROUND

Human epidermal growth factor receptor 2 (HER2)-positive breast cancer accounts for about 20% of all breast cancer cases and is correlated with a high relapse rate and poor prognosis. ADAMTS18 is proposed as an important functional tumor suppressor gene involved in multiple malignancies, including breast cancer. It functions as an extracellular matrix (ECM) modifier. However, it remains unclear whether ADAMTS18 affects mammary tumorigenesis and malignant progression through its essential ECM regulatory function.

METHODS

To elucidate the role of ADAMTS18 in HER2-positive mammary tumorigenesis and metastasis in vivo, we compared the incidence of mammary tumor and metastasis between Adamts18-knockout (MMTV)-Her2/ErbB2/Neu+ transgenic mice (i.e., Her2t/w/Adamts18-/-) and Adamts18-wildtype (MMTV)-Her2/ErbB2/Neu+ transgenic mice (i.e., Her2t/w/Adamts18+/+). The underlying mechanisms by which ADAMTS18 regulates HER2-positive tumorigenesis and metastasis were investigated by pathology, cell culture, Western blot and immunochemistry.

RESULTS

Adamts18 mRNA is mainly expressed in myoepithelial cells of the mammary duct. ADAMTS18 deficiency leads to a significantly increased incidence of mammary tumors and metastasis, as well as mammary hyperplasia in mice, over 30 months of observation. The proliferation, migration and invasion capacities of primary Her2t/w/Adamts18-/- mammary tumor cells are significantly higher than those of primary Her2t/w/Adamts18+/+ mammary tumor cells in vitro. At 30 months of age, the expression levels of laminin (LNα5), fibronectin (FN) and type I collagen (ColI) in the mammary glands of Her2t/w/Adamts18-/- mice are significantly increased, and the activities of integrin-mediated PI3K/AKT, ERK and JNK signaling pathways are enhanced.

CONCLUSIONS

ADAMTS18 deficiency leads to alterations in mammary ECM components (e.g., LNα5, FN, ColI), which are associated with a higher risk of HER2-positive mammary tumorigenesis and metastasis.

Identification of a basement membrane gene signature for predicting prognosis and estimating the tumor immune microenvironment in prostate cancer

Basement membrane plays an important role in tumor invasion and metastasis, which is closely related to prognosis. However, the prognostic value and biology of basement membrane genes (BMGs) in prostate cancer (PCa) remain unknown. In the TCGA training set, we used differentially expressed gene analysis, protein-protein interaction networks, univariate and multivariate Cox regression, and least absolute shrinkage and selection operator regression to construct a basement membrane-related risk model (BMRM) and validated its effectiveness in the MSKCC validation set. Furthermore, the accurate nomogram was constructed to improve clinical applicability. Patients with PCa were divided into high-risk and low-risk groups according to the optimal cut-off value of the basement membrane-related risk score (BMRS). It was found that BMRS was significantly associated with RFS, T-stage, Gleason score, and tumor microenvironmental characteristics in PCa patients. Further analysis showed that the model grouping was closely related to tumor immune microenvironment characteristics, immune checkpoint inhibitors, and chemotherapeutic drug sensitivity. In this study, we developed a new BMGs-based prognostic model to determine the prognostic value of BMGs in PCa. Finally, we confirmed that THBS2, a key gene in BMRM, may be an important link in the occurrence and progression of PCa. This study provides a novel perspective to assess the prognosis of PCa patients and provides clues for the selection of future personalized treatment regimens.

Recent progress on the effect of extracellular matrix on occurrence and progression of breast cancer

Breast cancer (BC) metastasis is an enormous challenge targeting BC therapy. The extracellular matrix (ECM), the principal component of the BC metastasis niche, is the pivotal driver of breast tumor development, whose biochemical and biophysical characteristics have attracted widespread attention. Here, we review the biological effects of ECM constituents and the influence of ECM stiffness on BC metastasis and drug resistance. We provide an overview of the relative signal transduction mechanisms, existing metastasis models, and targeted drug strategies centered around ECM stiffness. It will shed light on exploring more underlying targets and developing specific drugs aimed at ECM utilizing biomimetic platforms, which are promising for breast cancer treatment.

Laminin 332 expression levels predict clinical outcomes and chemotherapy response in patients with pancreatic adenocarcinoma

Poor outcomes and chemotherapy resistance for patients with pancreatic adenocarcinoma (PAAD) are a challenge worldwide, and new or improved prognostic biomarkers are urgently required. Individual laminin family members have been established as cancer-associated markers, predicting patient outcomes in many cancer types, including PAAD. Here, we used multiple modalities including RNAseq and gene chip, and genomic and proteomic data to examine the relationships of all laminin genes in PAAD with clinical outcomes. These analyses identified that LAMA3, LAMB3, and LAMC2 expression levels are increased at the mRNA and protein levels in PAAD tumours with evidence of co-regulation. Increased expression of all three genes was associated with decreased promoter methylation status, TP53 mutations, and altered receptor tyrosine kinase (RTK) pathways. Clinically, high LAMA3, LAMB3, and LAMC2 transcript abundance was each related to an advanced histological grade. Moreover, high expression of these genes individually predicted poor patient survival, while a signature of combined high expression of LAMA3, LAMB3, and LAMC2 was a stronger predictor of patient outcomes than each gene alone. Interestingly, cell lines with high expression of LM332 chains were not sensitive to the commonly used PAAD chemotherapy drugs paclitaxel and gemcitabine; however, increased sensitivity was evident for erlotinib, afatinib, gefitinib, and cetuximab epidermal growth factor (EGFR) RTK inhibitors. To explore possible mechanisms, we investigated co-expressed genes, identifying eight hub genes, namely, GJB3, ITGB6, SERPINB5, GPRC5A, PLEK2, TMPRSS4, P2RY2, and TRIM29, which are co-expressed with all three of LAMA3, LAMB3, and LAMC2. Of these, only SERPINB5 provided a stronger predictive value than the laminin-encoding genes. Together, these multiple integrated analyses suggest that the combined expression of LM332 is a useful prognostic biomarker for PAAD and could help patient stratification and therapeutic selection.

Basal cell adhesion molecule promotes metastasis-associated processes in ovarian cancer

BACKGROUND

Basal cell adhesion molecule (BCAM) is a laminin α5 (LAMA5) binding membrane-bound protein with a putative role in cancer. Besides full-length BCAM1, an isoform lacking most of the cytoplasmic domain (BCAM2), and a soluble form (sBCAM) of unknown function are known. In ovarian carcinoma (OC), all BCAM forms are abundant and associated with poor survival, yet BCAM's contribution to peritoneal metastatic spread remains enigmatic.

METHODS

Biochemical, omics-based and real-time cell assays were employed to identify the source of sBCAM and metastasis-related functions of different BCAM forms. OC cells, explanted omentum and a mouse model of peritoneal colonisation were used in loss- and gain-of-function experiments.

RESULTS

We identified ADAM10 as a major BCAM sheddase produced by OC cells and identified proteolytic cleavage sites proximal to the transmembrane domain. Recombinant soluble BCAM inhibited single-cell adhesion and migration identically to membrane-bound isoforms, confirming its biological activity in OC. Intriguingly, this seemingly anti-tumorigenic potential of BCAM contrasts with a novel pro-metastatic function discovered in the present study. Thus, all queried BCAM forms decreased the compactness of tumour cell spheroids by inhibiting LAMA5 - integrin β1 interactions, promoted spheroid dispersion in a three-dimensional collagen matrix, induced clearance of mesothelial cells at spheroid attachment sites in vitro and enhanced invasion of spheroids into omental tissue both ex vivo and in vivo.

CONCLUSIONS

Membrane-bound BCAM as well as sBCAM shed by ADAM10 act as decoys rather than signalling receptors to modulate metastasis-related functions. While BCAM appears to have tumour-suppressive effects on single cells, it promotes the dispersion of OC cell spheroids by regulating LAMA5-integrin-β1-dependent compaction and thereby facilitating invasion of metastatic target sites. As peritoneal dissemination is majorly mediated by spheroids, these findings offer an explanation for the association of BCAM with a poor clinical outcome of OC, suggesting novel therapeutic options.

The biomimetic extracellular matrix: a therapeutic tool for breast cancer research

A deeper knowledge of the functional versatility and dynamic nature of the ECM has improved the understanding of cancer biology. Translational Significance: This work provides an in-depth view of the importance of the ECM to develop more mimetic breast cancer models, which aim to recreate the components and architecture of tumor microenvironment. Special focus is placed on decellularized matrices derived from tissue and cell culture, both in procurement and applications, as they have achieved great success in cancer research and pharmaceutical sector. The extracellular matrix (ECM) is increasingly recognized as a master regulator of cell behavior and response to breast cancer (BC) treatment. During BC progression, the mammary gland ECM is remodeled and altered in the composition and organization. Accumulated evidence suggests that changes in the composition and mechanics of ECM, orchestrated by tumor-stromal interactions along with ECM remodeling enzymes, are actively involved in BC progression and metastasis. Understanding how specific ECM components modulate the tumorigenic process has led to an increased interest in the development of biomaterial-based biomimetic ECM models to recapitulate key tumor characteristics. The decellularized ECMs (dECMs) have emerged as a promising in vitro 3D tumor model, whose recent advances in the processing and application could become the biomaterial by excellence for BC research and the pharmaceutical industry. This review offers a detailed view of the contribution of ECM in BC progression, and highlights the application of dECM-based biomaterials as promising personalized tumor models that more accurately mimic the tumorigenic mechanisms of BC and the response to treatment. This will allow the design of targeted therapeutic approaches adapted to the specific characteristics of each tumor that will have a great impact on the precision medicine applied to BC patients.

Laboratory Models for Investigating Breast Cancer Therapy Resistance and Metastasis

While numerous therapies are highly efficacious in early-stage breast cancers and in particular subsets of breast cancers, therapeutic resistance and metastasis unfortunately arise in many patients. In many cases, tumors that are resistant to standard of care therapies, as well as tumors that have metastasized, are treatable but incurable with existing clinical strategies. Both therapy resistance and metastasis are multi-step processes during which tumor cells must overcome diverse environmental and selective hurdles. Mechanisms by which tumor cells achieve this are numerous and include acquisition of invasive and migratory capabilities, cell-intrinsic genetic and/or epigenetic adaptations, clonal selection, immune evasion, interactions with stromal cells, entering a state of dormancy or senescence, and maintaining self-renewal capacity. To overcome therapy resistance and metastasis in breast cancer, the ability to effectively model each of these mechanisms in the laboratory is essential. Herein we review historic and the current state-of-the-art laboratory model systems and experimental approaches used to investigate breast cancer metastasis and resistance to standard of care therapeutics. While each model system has inherent limitations, they have provided invaluable insights, many of which have translated into regimens undergoing clinical evaluation. We will discuss the limitations and advantages of a variety of model systems that have been used to investigate breast cancer metastasis and therapy resistance and outline potential strategies to improve experimental modeling to further our knowledge of these processes, which will be crucial for the continued development of effective breast cancer treatments.

Integrin α3β1 Represses Reelin Expression in Breast Cancer Cells to Promote Invasion

Simple Summary

Breast cancer remains the second leading cause of cancer-related deaths in women, and about 1 in 8 women in the United States develops invasive breast cancer in her lifetime. Integrin α3β1 has been linked to breast cancer progression, but mechanisms whereby it promotes tumor invasion remain unclear. The goal of our study was to determine how α3β1 drives invasion, towards exploiting this integrin as a therapeutic target for breast cancer. We found that α3β1 represses the expression of Reelin, a secreted glycoprotein that inhibits invasion and for which loss of expression is associated with poor prognosis in breast cancer. We also show that increased Reelin expression following RNAi-mediated suppression of α3β1 causes a significant decrease in breast cancer cell invasion. Our findings demonstrate a critical role for α3β1 in promoting cell invasion through repression of Reelin, highlighting the potential value of this integrin as a therapeutic target for breast cancer.

Abstract

Integrin α3β1, a cell adhesion receptor for certain laminins, is known to promote breast tumor growth and invasion. Our previous gene microarray study showed that the RELN gene, which encodes the extracellular glycoprotein Reelin, was upregulated in α3β1-deficient (i.e., α3 knockdown) MDA-MB-231 cells. In breast cancer, reduced RELN expression is associated with increased invasion and poor prognosis. In this study we demonstrate that α3β1 represses RELN expression to enhance breast cancer cell invasion. RELN mRNA was significantly increased upon RNAi-mediated α3 knockdown in two triple-negative breast cancer cell lines, MDA-MB-231 and SUM159. Modulation of baseline Reelin levels altered invasive potential, where enhanced Reelin expression in MDA-MB-231 cells reduced invasion, while RNAi-mediated suppression of Reelin in SUM159 cells increased invasion. Moreover, treatment of α3β1-expressing MDA-MB-231 cells with culture medium that was conditioned by α3 knockdown MDA-MB-231 cells led to decreased invasion. RNAi-mediated suppression of Reelin in α3 knockdown MDA-MB-231 cells mitigated this effect of conditioned-medium, identifying secreted Reelin as an inhibitor of cell invasion. These results demonstrate a novel role for α3β1 in repressing Reelin in breast cancer cells to promote invasion, supporting this integrin as a potential therapeutic target.

The Tumor Microenvironment as a Driving Force of Breast Cancer Stem Cell Plasticity

Simple Summary

Breast cancer stem cells are a subset of transformed cells that sustain tumor growth and can metastasize to secondary organs. Since metastasis accounts for most cancer deaths, it is of paramount importance to understand the cellular and molecular mechanisms that regulate this subgroup of cells. The tumor microenvironment (TME) is the habitat in which transformed cells evolve, and it is composed by many different cell types and the extracellular matrix (ECM). A body of evidence strongly indicates that microenvironmental cues modulate stemness in breast cancer, and that the coevolution of the TME and cancer stem cells determine the fate of breast tumors. In this review, we summarize the studies providing links between the TME and the breast cancer stem cell phenotype and we discuss their specific interactions with immune cell subsets, stromal cells, and the ECM.

Abstract

Tumor progression involves the co-evolution of transformed cells and the milieu in which they live and expand. Breast cancer stem cells (BCSCs) are a specialized subset of cells that sustain tumor growth and drive metastatic colonization. However, the cellular hierarchy in breast tumors is rather plastic, and the capacity to transition from one cell state to another depends not only on the intrinsic properties of transformed cells, but also on the interplay with their niches. It has become evident that the tumor microenvironment (TME) is a major player in regulating the BCSC phenotype and metastasis. The complexity of the TME is reflected in its number of players and in the interactions that they establish with each other. Multiple types of immune cells, stromal cells, and the extracellular matrix (ECM) form an intricate communication network with cancer cells, exert a highly selective pressure on the tumor, and provide supportive niches for BCSC expansion. A better understanding of the mechanisms regulating these interactions is crucial to develop strategies aimed at interfering with key BCSC niche factors, which may help reducing tumor heterogeneity and impair metastasis.

Addressing the tumour microenvironment in early drug discovery: a strategy to overcome drug resistance and identify novel targets for cancer therapy

The tumour microenvironment (TME) comprises not only malignant and non-malignant cells, but also the extracellular matrix (ECM), secreted factors, and regulators of cellular functions. In addition to genetic alterations, changes of the biochemical/biophysical properties or cellular composition of the TME have been implicated in drug resistance. Here, we review the composition of the ECM and different elements of the TME contributing to drug resistance, including soluble factors, hypoxia, extracellular acidity, and cell adhesion properties. We discuss selected approaches for modelling the TME, current progress, and their use in low-and high-throughput assays for preclinical studies. Lastly, we summarise the status quo of advanced 3D cancer models compatible with high-throughput screening (HTS), the technical practicalities and challenges.

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.

The Tumor Microenvironment: Focus on Extracellular Matrix

The extracellular matrix (ECM) regulates the development and maintains tissue homeostasis. The ECM is composed of a complex network of molecules presenting distinct biochemical properties to regulate cell growth, survival, motility, and differentiation. Among their components, proteoglycans (PGs) are considered one of the main components of ECM. Its composition, biomechanics, and anisotropy are exquisitely tuned to reflect the physiological state of the tissue. The loss of ECM's homeostasis is seen as one of the hallmarks of cancer and, typically, defines transitional events in tumor progression and metastasis. In this chapter, we discuss the types of proteoglycans and their roles in cancer. It has been observed that the amount of some ECM components is increased, while others are decreased, depending on the type of tumor. However, both conditions corroborate with tumor progression and malignancy. Therefore, ECM components have an increasingly important role in carcinogenesis and this leads us to believe that their understanding may be a key in the discovery of new anti-tumor therapies. In this book, the main ECM components will be discussed in more detail in each chapter.

Beyond proteases: Basement membrane mechanics and cancer invasion

In epithelial cancers, cells must invade through basement membranes (BMs) to metastasize. The BM, a thin layer of extracellular matrix underlying epithelial and endothelial tissues, is primarily composed of laminin and collagen IV and serves as a structural barrier to cancer cell invasion, intravasation, and extravasation. BM invasion has been thought to require protease degradation since cells, which are typically on the order of 10 µm in size, are too large to squeeze through the nanometer-scale pores of the BM. However, recent studies point toward a more complex picture, with physical forces generated by cancer cells facilitating protease-independent BM invasion. Moreover, collective cell interactions, proliferation, cancer-associated fibroblasts, myoepithelial cells, and immune cells are all implicated in regulating BM invasion through physical forces. A comprehensive understanding of BM structure and mechanics and diverse modes of BM invasion may yield new strategies for blocking cancer progression and metastasis.

[10]-Gingerol Affects Multiple Metastatic Processes and Induces Apoptosis in MDAMB- 231 Breast Tumor Cells

Background:

Triple Negative Breast Cancer (TNBC) represents the approximately 15% of breast cancers that lack expression of Estrogen (ER) and Progesterone Receptors (PR) and do not exhibit amplification of the human epidermal growth factor receptor 2 (HER2) gene, imposing difficulties to treatment. Interactions between tumor cells and their microenvironment facilitate tumor cell invasion in the surrounding tissues, intravasation through newly formed vessels, and dissemination to form metastasis. To treat metastasis from breast and many other cancer types, chemotherapy is one of the most extensively used methods. However, its efficacy and safety remain a primary concern, as well as its toxicity and other side effects. Thus, there is increasing interest in natural antitumor agents. In a previous work, we have demonstrated that [10]-gingerol is able to revert malignant phenotype in breast cancer cells in 3D culture and, moreover, to inhibit the dissemination of TNBC to multiple organs including lung, bone and brain, in spontaneous and experimental in vivo metastasis assays in mouse model.

Objective:

This work aims to investigate the in vitro effects of [10]-gingerol, using human MDA-MB-231TNBC cells, in comparison to non-tumor MCF-10A breast cells, in order to understand the antitumor and antimetastatic effects found in vivo and in a 3D environment.

Methods:

We investigated different steps of the metastatic process in vitro, such as cell migration, invasion, adhesion and MMP activity. In addition, we analyzed the anti-apoptotic and genotoxic effects of [10]-gingerol using PEAnnexin, DNA fragmentation, TUNEL and comet assays, respectively.

Results:

[10]-gingerol was able to inhibit cell adhesion, migration, invasion and to induce apoptosis more effectively in TNBC cells, when compared to non-tumor cells, demonstrating that these mechanisms can be involved in the antitumor and antimetastatic effects of [10]-gingerol, found both in 3D culture and in vivo.

Conclusion:

Taken together, results found here are complementary to previous studies of our group and others and demonstrate that additional mechanisms, besides apoptotic cell death, is used by [10]-gingerol to accomplish its antitumor and antimetastatic effects. Our results indicate a potential for this natural compound as an antitumor molecule or as an adjuvant for chemotherapeutics already used in the clinic.

Decellularized Extracellular Matrix for Cancer Research

Genetic mutation and alterations of intracellular signaling have been focused on to understand the mechanisms of oncogenesis and cancer progression. Currently, it is pointed out to consider cancer as tissues. The extracellular microenvironment, including the extracellular matrix (ECM), is important for the regulation of cancer cell behavior. To comprehensively investigate ECM roles in the regulation of cancer cell behavior, decellularized ECM (dECM) is now used as an in vitro ECM model. In this review, I classify dECM with respect to its sources and summarize the preparation and characterization methods for dECM. Additionally, the examples of cancer research using the dECM were introduced. Finally, future perspectives of cancer studies with dECM are described in the conclusions.

Integrin α6 and EGFR signaling converge at mechanosensitive calpain 2

Cells sense and respond to mechanical cues from the extracellular matrix (ECM) via integrins. ECM stiffness is known to enhance integrin clustering and response to epidermal growth factor (EGF), but we lack information on when or if these mechanosensitive growth factor receptors and integrins converge intracellularly. Towards closing this knowledge gap, we combined a biomaterial platform with transcriptomics, molecular biology, and functional assays to link integrin-mediated mechanosensing and epidermal growth factor receptor (EGFR) signaling. We found that high integrin α6 expression controlled breast cancer cell adhesion and motility on soft, laminin-coated substrates, and this mimicked the response of cells to EGF stimulation. The mechanisms that drove both mechanosensitive cell adhesion and motility converged on calpain 2, an intracellular protease important for talin cleavage and focal adhesion turnover. EGF stimulation enhanced adhesion and motility on soft substrates, but required integrin α6 and calpain 2 signaling. In sum, we identified a new role for integrin α6 mechanosensing in breast cancer, wherein cell adhesion to laminin on soft substrates mimicked EGF stimulation. We identified calpain 2, downstream of both integrin α6 engagement and EGFR phosphorylation, as a common intracellular signaling node, and implicate integrin α6 and calpain 2 as potential targets to inhibit the migration of cancer cells in stiff tumor environments.

Drosophila Embryonic Hemocytes Produce Laminins to Strengthen Migratory Response

The most prominent developmental function attributed to the extracellular matrix (ECM) is cell migration. While cells in culture can produce ECM to migrate, the role of ECM in regulating developmental cell migration is classically viewed as an exogenous matrix presented to the moving cells. In contrast to this view, we show here that Drosophila embryonic hemocytes deposit their own laminins in streak-like structures to migrate efficiently throughout the embryo. With the help of transplantation experiments, live microscopy, and image quantification, we demonstrate that autocrine-produced laminin regulates hemocyte migration by controlling lamellipodia dynamics, stability, and persistence. Proper laminin deposition is regulated by the RabGTPase Rab8, which is highly expressed and required in hemocytes for lamellipodia dynamics and migration. Our results thus support a model in which, during embryogenesis, the Rab8-regulated autocrine deposition of laminin reinforces directional and effective migration by stabilizing cellular protrusions and strengthening otherwise transient adhesion states.

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Drosophila embryonic hemocytes use autocrine-produced laminins for their migration

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Autocrine laminins regulate lamellipodia dynamics, stability, and persistence

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Rab8 regulates laminin deposition and lamellipodia dynamics in migrating hemocytes

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Laminins deposit in tracks around hemocytes and in a fibrillar mesh over the VNC

Systematic analysis of tumour cell-extracellular matrix adhesion identifies independent prognostic factors in breast cancer

Tumour cell-extracellular matrix (ECM) interactions are fundamental for discrete steps in breast cancer progression. In particular, cancer cell adhesion to ECM proteins present in the microenvironment is critical for accelerating tumour growth and facilitating metastatic spread. To assess the utility of tumour cell-ECM adhesion as a means for discovering prognostic factors in breast cancer survival, here we perform a systematic phenotypic screen and characterise the adhesion properties of a panel of human HER2 amplified breast cancer cell lines across six ECM proteins commonly deregulated in breast cancer. We determine a gene expression signature that defines a subset of cell lines displaying impaired adhesion to laminin. Cells with impaired laminin adhesion showed an enrichment in genes associated with cell motility and molecular pathways linked to cytokine signalling and inflammation. Evaluation of this gene set in the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) cohort of 1,964 patients identifies the F12 and STC2 genes as independent prognostic factors for overall survival in breast cancer. Our study demonstrates the potential of in vitro cell adhesion screens as a novel approach for identifying prognostic factors for disease outcome.

Integrated bioinformatics analysis reveals key candidate genes and pathways in breast cancer

Breast cancer (BC) is the leading malignancy in women worldwide, yet relatively little is known about the genes and signaling pathways involved in BC tumorigenesis and progression. The present study aimed to elucidate potential key candidate genes and pathways in BC. Five gene expression profile data sets (GSE22035, GSE3744, GSE5764, GSE21422 and GSE26910) were downloaded from the Gene Expression Omnibus (GEO) database, which included data from 113 tumorous and 38 adjacent non-tumorous tissue samples. Differentially expressed genes (DEGs) were identified using t-tests in the limma R package. These DEGs were subsequently investigated by pathway enrichment analysis and a protein-protein interaction (PPI) network was constructed. The most significant module from the PPI network was selected for pathway enrichment analysis. In total, 227 DEGs were identified, of which 82 were upregulated and 145 were downregulated. Pathway enrichment analysis results revealed that the upregulated DEGs were mainly enriched in ‘cell division’, the ‘proteinaceous extracellular matrix (ECM)’, ‘ECM structural constituents’ and ‘ECM-receptor interaction’, whereas downregulated genes were mainly enriched in ‘response to drugs’, ‘extracellular space’, ‘transcriptional activator activity’ and the ‘peroxisome proliferator-activated receptor signaling pathway’. The PPI network contained 174 nodes and 1,257 edges. DNA topoisomerase 2-a, baculoviral inhibitor of apoptosis repeat-containing protein 5, cyclin-dependent kinase 1, G2/mitotic-specific cyclin-B1 and kinetochore protein NDC80 homolog were identified as the top 5 hub genes. Furthermore, the genes in the most significant module were predominantly involved in ‘mitotic nuclear division’, ‘mid-body’, ‘protein binding’ and ‘cell cycle’. In conclusion, the DEGs, relative pathways and hub genes identified in the present study may aid in understanding of the molecular mechanisms underlying BC progression and provide potential molecular targets and biomarkers for BC.

Modulation of fibronectin and laminin expression by Rhodium (II) citrate-coated maghemite nanoparticles in mice bearing breast tumor

Degradation of cellular matrix is one of the important processes related to the progression of breast cancer. Tumor cells have the ability to exhibit necessary conditions for growth and survival, promoting degradation processes of extracellular matrix proteins, such as laminin (LN) and fibronectin (FN). In this study, we evaluated whether treatments, based on free rhodium (II) citrate (Rh₂(H₂cit)₄), maghemite nanoparticles coated with citrate (Magh-cit) and maghemite nanoparticles coated with rhodium (II) citrate (Magh-Rh₂(H₂cit)₄), in murine metastatic breast carcinoma models can modulate the expression of laminin and fibronectin proteins. Synthesized nanoparticles were characterized using X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy and dynamic light scattering. The expression of FN and LN was assessed using immunohistochemistry and western blotting. The gene expression of FN1 and LAMA1 were evaluated using real-time PCR. The FN1 and LAMA1 transcripts from the Magh-Rh₂(H₂cit)₄ treated group were 95% and 94%, respectively, lower than the control group. Significant reduction in tumor volume for animals treated with Magh-Rh₂(H₂cit)₄ was observed, of about 83%. We witnessed statistically significant reductions of FN and LN expression following treatment with Magh-Rh₂(H₂cit)₄. We have demonstrated that the antitumor effects of Magh-Rh₂(H₂cit)₄ and Rh₂(H₂cit)₄ regulate the expression of FN and LN in metastatic breast tumors.

Migration of breast cancer cell lines in response to pulmonary laminin 332

Because tumor cell motility is a requirement for metastasis, we hypothesized that lung tissue harbors substances that induce tumor cell migration. MCF-7 breast carcinoma cells exposed to small airway epithelial cells and conditioned medium exhibited dose-dependent tumor cell migration. Among the extracellular matrix proteins in the conditioned medium identified by mass spectrometry, laminin 332 (LM332) had the greatest contribution to the migration of MCF-7 cells. Immunoblotting and immunohistochemistry for LM332-specific chains identified LM332 in the lung and in pulmonary epithelial cells. Antibodies to either LM332 or its integrin receptor inhibited MCF-7 motility, and knockdown of LM332 chains also reduced its migration-inducing activity. Taken together, these findings implicate LM332 as a component of lung tissue that can induce motility in breast carcinoma cells that have been transported to lung during metastasis. Earlier studies on LM332 in tumor progression have examined LM332 expression in tumor cells. This investigation, in comparison, provides evidence that the tumor promoting potential of LM332 may originate in the lung microenvironment rather than in tumor cells alone. Furthermore, this study provides evidence that the motility-inducing properties of the microenvironment can reside in epithelial cells. The findings raise the possibility that LM332 plays a role in the pulmonary metastases of breast carcinoma and may provide a target for antimetastasis therapy.

The extracellular matrix in breast cancer

The extracellular matrix (ECM) is increasingly recognized as an important regulator in breast cancer. ECM in breast cancer development features numerous changes in composition and organization when compared to the mammary gland under homeostasis. Matrix proteins that are induced in breast cancer include fibrillar collagens, fibronectin, specific laminins and proteoglycans as well as matricellular proteins. Growing evidence suggests that many of these induced ECM proteins play a major functional role in breast cancer progression and metastasis. A number of the induced ECM proteins have moreover been shown to be essential components of metastatic niches, promoting stem/progenitor signaling pathways and metastatic growth. ECM remodeling enzymes are also markedly increased, leading to major changes in the matrix structure and biomechanical properties. Importantly, several ECM components and ECM remodeling enzymes are specifically induced in breast cancer or during tissue regeneration while healthy tissues under homeostasis express exceedingly low levels. This may indicate that ECM and ECM-associated functions may represent promising drug targets against breast cancer, providing important specificity that could be utilized when developing therapies.

The extracellular matrix in breast cancer predicts prognosis through composition, splicing, and crosslinking

The extracellular matrix in the healthy breast has an important tumor suppressive role, whereas the abnormal ECM in tumors can promote aggressiveness, and has been linked to breast cancer relapse, survival and resistance to chemotherapy. This review article gives an overview of the elements of the ECM which have been linked to prognosis of breast cancers, including changes in ECM protein composition, splicing, and microstructure.

Functional and molecular characterisation of EO771.LMB tumours, a new C57BL/6-mouse-derived model of spontaneously metastatic mammary cancer

The translation of basic research into improved therapies for breast cancer patients requires relevant preclinical models that incorporate spontaneous metastasis. We have completed a functional and molecular characterisation of a new isogenic C57BL/6 mouse model of breast cancer metastasis, comparing and contrasting it with the established BALB/c 4T1 model. Metastatic EO771.LMB tumours were derived from poorly metastatic parental EO771 mammary tumours. Functional differences were evaluated using both in vitro assays and spontaneous metastasis assays in mice. Results were compared to non-metastatic 67NR and metastatic 4T1.2 tumours of the 4T1 model. Protein and transcript levels of markers of human breast cancer molecular subtypes were measured in the four tumour lines, as well as p53 (Tp53) tumour-suppressor gene status and responses to tamoxifen in vivo and in vitro. Array-based expression profiling of whole tumours identified genes and pathways that were deregulated in metastatic tumours. EO771.LMB cells metastasised spontaneously to lung in C57BL/6 mice and displayed increased invasive capacity compared with parental EO771. By immunohistochemical assessment, EO771 and EO771.LMB were basal-like, as was the 4T1.2 tumour, whereas 67NR had a luminal phenotype. Primary tumours from all lines were negative for progesterone receptor, Erb-b2/Neu and cytokeratin 5/6, but positive for epidermal growth factor receptor (EGFR). Only 67NR displayed nuclear estrogen receptor alpha (ERα) positivity. EO771 and EO771.LMB expressed mutant p53, whereas 67NR and 4T1.2 were p53-null. Integrated molecular analysis of both the EO771/EO771.LMB and 67NR/4T1.2 pairs indicated that upregulation of matrix metalloproteinase-3 (MMP-3), parathyroid hormone-like hormone (Pthlh) and S100 calcium binding protein A8 (S100a8) and downregulation of the thrombospondin receptor (Cd36) might be causally involved in metastatic dissemination of breast cancer.

Tumour but not stromal expression of β3 integrin is essential, and is required early, for spontaneous dissemination of bone-metastatic breast cancer

Although many preclinical studies have implicated β3 integrin receptors (αvβ3 and αIIbβ3) in cancer progression, β3 inhibitors have shown only modest efficacy in patients with advanced solid tumours. The limited efficacy of β3 inhibitors in patients could arise from our incomplete understanding of the precise function of β3 integrin and, consequently, inappropriate clinical application. Data from animal studies are conflicting and indicate heterogeneity with respect to the relative contributions of β3-expressing tumour and stromal cell populations in different cancers. Here we aimed to clarify the function and relative contributions to metastasis of tumour versus stromal β3 integrin in clinically relevant models of spontaneous breast cancer metastasis, with particular emphasis on bone metastasis. We show that stable down-regulation of tumour β3 integrin dramatically impairs spontaneous (but not experimental) metastasis to bone and lung without affecting primary tumour growth in the mammary gland. Unexpectedly, and in contrast to subcutaneous tumours, orthotopic tumour vascularity, growth and spontaneous metastasis were not altered in mice null for β3 integrin. Tumour β3 integrin promoted migration, protease expression and trans-endothelial migration in vitro and increased vascular dissemination in vivo, but was not necessary for bone colonization in experimental metastasis assays. We conclude that tumour, rather than stromal, β3 expression is essential and is required early for efficient spontaneous breast cancer metastasis to bone and soft tissues. Accordingly, differential gene expression analysis in cohorts of breast cancer patients showed a strong association between high β3 expression, early metastasis and shorter disease-free survival in patients with oestrogen receptor-negative tumours. We propose that β3 inhibitors may be more efficacious if used in a neoadjuvant setting, rather than after metastases are established.

Expression of integrin α3β1 and cyclooxygenase-2 (COX2) are positively correlated in human breast cancer

BACKGROUND

Expression of integrin α3β1 is associated with tumor progression, metastasis, and poor prognosis in several cancers, including breast cancer. Moreover, preclinical studies have revealed important pro-tumorigenic and pro-metastatic functions for this integrin, including tumor growth, survival, invasion, and paracrine induction of angiogenesis. Our previously published work in a preclinical breast cancer model showed that integrin α3β1 promotes expression of cyclooxygenase-2 (COX2/PTGS2), a known driver of breast cancer progression. However, the clinical significance of this regulation was unknown. The objective of the current study was to assess the clinical relevance of the relationship between integrin α3β1 and COX2 by testing for their correlated expression among various forms of human breast cancer.

METHODS

Immunohistochemistry was performed to assess co-expression of α3 and COX2 in specimens of human invasive ductal carcinoma (IDC), either on a commercial tissue microarray (n = 59 samples) or obtained from Albany Medical Center archives (n = 68 samples). Immunostaining intensity for the integrin α3 subunit or COX2 was scored, and Spearman's rank correlation coefficient analysis was performed to assess their co-expression across and within different tumor subtypes or clinicopathologic criteria.

RESULTS

Although expression of integrin α3 or COX2 varied among clinical IDC samples, a statistically significant, positive correlation was detected between α3 and COX2 in both tissue microarrays (r(s) = 0.49, p < 0.001, n = 59) and archived samples (r(s) = 0.59, p < 0.0001, n = 68). In both sample sets, this correlation was independent of hormone receptor status, histological grade, or disease stage.

CONCLUSIONS

COX2 and α3 are correlated in IDC independently of hormone receptor status or other clinicopathologic features, supporting the hypothesis that integrin α3β1 is a determinant of COX2 expression in human breast cancer. These results support the clinical relevance of α3β1-dependent COX2 gene expression that we reported previously in breast cancer cells. The findings also suggest that COX2-positive breast carcinomas of various subtypes might be vulnerable to therapeutic strategies that target α3β1, and that α3 expression might serve as an independent prognostic biomarker.

Bone-derived soluble factors and laminin-511 cooperate to promote migration, invasion and survival of bone-metastatic breast tumor cells

Tumor intrinsic and extrinsic factors are thought to contribute to bone metastasis but little is known about how they cooperate to promote breast cancer spread to bone. We used the bone-metastatic 4T1BM2 mammary carcinoma model to investigate the cooperative interactions between tumor LM-511 and bone-derived soluble factors in vitro. We show that bone conditioned medium cooperates with LM-511 to enhance 4T1BM2 cell migration and invasion and is sufficient alone to promote survival in the absence of serum. These responses were associated with increased secretion of MMP-9 and activation of ERK and AKT signaling pathways and were partially blocked by pharmacological inhibitors of MMP-9, AKT-1/2 or MEK. Importantly, pre-treatment of 4T1BM2 cells with an AKT-1/2 inhibitor significantly reduced experimental metastasis to bone in vivo. Promotion of survival and invasive responses by bone-derived soluble factors and tumor-derived LM-511 are likely to contribute to the metastatic spread of breast tumors to bone.

Pharmacological levels of Withaferin A (Withania somnifera) trigger clinically relevant anticancer effects specific to triple negative breast cancer cells

Withaferin A (WA) isolated from Withania somnifera (Ashwagandha) has recently become an attractive phytochemical under investigation in various preclinical studies for treatment of different cancer types. In the present study, a comparative pathway-based transcriptome analysis was applied in epithelial-like MCF-7 and triple negative mesenchymal MDA-MB-231 breast cancer cells exposed to different concentrations of WA which can be detected systemically in in vivo experiments. Whereas WA treatment demonstrated attenuation of multiple cancer hallmarks, the withanolide analogue Withanone (WN) did not exert any of the described effects at comparable concentrations. Pathway enrichment analysis revealed that WA targets specific cancer processes related to cell death, cell cycle and proliferation, which could be functionally validated by flow cytometry and real-time cell proliferation assays. WA also strongly decreased MDA-MB-231 invasion as determined by single-cell collagen invasion assay. This was further supported by decreased gene expression of extracellular matrix-degrading proteases (uPA, PLAT, ADAM8), cell adhesion molecules (integrins, laminins), pro-inflammatory mediators of the metastasis-promoting tumor microenvironment (TNFSF12, IL6, ANGPTL2, CSF1R) and concomitant increased expression of the validated breast cancer metastasis suppressor gene (BRMS1). In line with the transcriptional changes, nanomolar concentrations of WA significantly decreased protein levels and corresponding activity of uPA in MDA-MB-231 cell supernatant, further supporting its anti-metastatic properties. Finally, hierarchical clustering analysis of 84 chromatin writer-reader-eraser enzymes revealed that WA treatment of invasive mesenchymal MDA-MB-231 cells reprogrammed their transcription levels more similarly towards the pattern observed in non-invasive MCF-7 cells. In conclusion, taking into account that sub-cytotoxic concentrations of WA target multiple metastatic effectors in therapy-resistant triple negative breast cancer, WA-based therapeutic strategies targeting the uPA pathway hold promise for further (pre)clinical development to defeat aggressive metastatic breast cancer.

Association of ITGA3 gene polymorphisms with susceptibility and clinicopathological characteristics of osteosarcoma

Integrin controls cell adhesion to extracellular matrix and plays an important role in regulating the proliferation and apoptosis of cells. In order to explore the role of ITGA3 gene polymorphisms in the pathogenesis and clinicopathological characteristics of osteosarcoma, we embarked on a study including a group of 118 patients and a group of 126 healthy controls. TaqMan PCR genotyping technology was used to detect the genotypes of ITGA3 gene SNPs (rs2230392, rs2285524 and rs16948627) in the peripheral blood. Then, associations of the SNP (rs2230392, rs2285524 and rs16948627) genotypes with the incidence risk and tumor characteristics of osteosarcoma were evaluated. A significant difference (P = 0.02) in the genotype frequency distribution of rs2230392 was observed between case and control groups. The analysis showed that patients carrying AA genotype had a higher risk of osteosarcoma (OR 2.34, 95 % CI 1.18-4.64) than those with GG genotype. Regarding rs2230392, men carrying AA genotype had a higher risk of osteosarcoma (OR 3.37, 95 % CI 1.25-9.11). Compared with those with GG genotype, patients carrying AA genotype had a twofold increased risk of osteosarcoma metastasis (OR 2.46, 95 % CI 1.09-5.57). Survival analysis showed that for rs2230392, survival time of osteosarcoma patients with three different genotypes was significantly different. Polymorphisms of ITGA3 gene rs2230392 may affect the incidence, metastasis and survival of osteosarcoma, which may clinically become a new target for predicting the risk of osteosarcoma, and have prognostic value.

Chain-specific antibodies for laminin-511

Mouse monoclonal antibodies (mAbs) that bind to specific chains of laminin-511 (LM-511) have been developed. Antibody 2F12 binds to the LMα5 chain, 3G10 binds to the LMβ1 chain and 3C12 binds to the LMγ1 chain. These antibodies can be used to purify LM-511, to detect LM-511 in cell extracts or to detect the location of LM-511 in tissue by immunohistochemistry. In combination, the antibodies recognize all three chains of LM-511 and combinations of the antibodies can be used to quantitate levels of LM-511 in physiological fluids. One of the antibodies (3G10) is a potent inhibitor of the activity of LM-511 in cell adhesion, spreading and proliferation assays.

Integrin α3β1 can function to promote spontaneous metastasis and lung colonization of invasive breast carcinoma

Significant evidence implicates α3β1 integrin in promoting breast cancer tumorigenesis and metastasis-associated cell behaviors in vitro and in vivo. However, the extent to which α3β1 is actually required for breast cancer metastasis remains to be determined. We used RNA interference to silence α3 integrin expression by approximately 70% in 4T1 murine mammary carcinoma cells, a model of aggressive, metastatic breast cancer. Loss of α3 integrin reduced adhesion, spreading, and proliferation on laminin isoforms, and modestly reduced the growth of orthotopically implanted cells. However, spontaneous metastasis to lung was strikingly curtailed. Experimental lung colonization after tail vein injection revealed a similar loss of metastatic capacity for the α3-silenced (α3si) cells, suggesting that critical, α3-dependent events at the metastatic site could account for much of α3β1's contribution to metastasis in this model. Reexpressing α3 in the α3si cells reversed the loss of metastatic capacity, and silencing another target, the small GTPase RhoC, had no effect, supporting the specificity of the effect of silencing α3. Parental, α3si, and α3-rescued cells, all secreted abundant laminin α5 (LAMA5), an α3β1 integrin ligand, suggesting that loss of α3 integrin might disrupt an autocrine loop that could function to sustain metastatic growth. Analysis of human breast cancer cases revealed reduced survival in cases where α3 integrin and LAMA5 are both overexpressed.

IMPLICATIONS

α3 integrin or downstream effectors may be potential therapeutic targets in disseminated breast cancers, especially when laminin α5 or other α3 integrin ligands are also over-expressed.

Breast cancer cell behaviors on staged tumorigenesis-mimicking matrices derived from tumor cells at various malignant stages

Extracellular matrix (ECM) has been focused to understand tumor progression in addition to the genetic mutation of cancer cells. Here, we prepared "staged tumorigenesis-mimicking matrices" which mimic in vivo ECM in tumor tissue at each malignant stage to understand the roles of ECM in tumor progression. Breast tumor cells, MDA-MB-231 (invasive), MCF-7 (non-invasive), and MCF-10A (benign) cells, were cultured to form their own ECM beneath the cells and formed ECM was prepared as staged tumorigenesis-mimicking matrices by decellularization treatment. Cells showed weak attachment on the matrices derived from MDA-MB-231 cancer cells. The proliferations of MDA-MB-231 and MCF-7 was promoted on the matrices derived from MDA-MB-231 cancer cells whereas MCF-10A cell proliferation was not promoted. MCF-10A cell proliferation was promoted on the matrices derived from MCF-10A cells. Chemoresistance of MDA-MB-231 cells against 5-fluorouracil increased on only matrices derived from MDA-MB-231 cells. Our results showed that the cells showed different behaviors on staged tumorigenesis-mimicking matrices according to the malignancy of cell sources for ECM preparation. Therefore, staged tumorigenesis-mimicking matrices might be a useful in vitro ECM models to investigate the roles of ECM in tumor progression.

Prostate specific membrane antigen produces pro-angiogenic laminin peptides downstream of matrix metalloprotease-2

Prostate specific membrane antigen (PSMA) is a pro-angiogenic cell-surface protease that we previously demonstrated regulates blood vessel formation in a laminin and integrin β1-dependent manner. Here, we examine the principal mechanism of PSMA activation of integrin β1. We show that digesting laminin sequentially with recombinant matrix metalloprotease-2 (MMP-2) and PSMA generates small peptides that enhance endothelial cell adhesion and migration in vitro. We also provide evidence that these laminin peptides activate adhesion via integrin α6β1 and focal adhesion kinase. Using an in vivo Matrigel implant assay, we show that these MMP/PSMA-derived laminin peptides also increase angiogenesis in vivo. Together, our results reveal a novel mechanism of PSMA activation of angiogenesis by processing laminin downstream of MMP-2.

A novel monoclonal antibody to human laminin α5 chain strongly inhibits integrin-mediated cell adhesion and migration on laminins 511 and 521

Laminins, a large family of αβγ heterotrimeric proteins mainly found in basement membranes, are strong promoters of adhesion and migration of multiple cell types, such as tumor and immune cells, via several integrin receptors. Among laminin α (LMα) chains, α5 displays the widest tissue distribution in adult life and is synthesized by most cell types. Here, we have generated and characterized five novel monoclonal antibodies (mAbs) to the human LMα5 chain to further study the biological relevance of α5 laminins, such as laminins 511 (α5β1γ1) and 521 (α5β2γ1). As detected by ELISA, immunohistochemistry, immunoprecipitation and Western blotting, each antibody displayed unique properties when compared to mAb 4C7, the prototype LMα5 antibody. Of greatest interest, mAb 8G9, but not any other antibody, strongly inhibited α3β1/α6β1 integrin-mediated adhesion and migration of glioma, melanoma, and carcinoma cells on laminin-511 and, together with mAb 4C7, on laminin-521. Accordingly, mAb 8G9 abolished the interaction of soluble α3β1 integrin with immobilized laminins 511 and 521. Binding of mAb 8G9 to laminin-511 was unaffected by the other mAbs to the LMα5 chain but largely hindered by mAb 4E10 to a LMβ1 chain epitope near the globular domain of laminin-511. Thus, mAb 8G9 defines a novel epitope localized at or near the integrin-binding globular domain of the LMα5 chain, which is essential for cell adhesion and migration, and identifies a potential therapeutic target in malignant and inflammatory diseases.

Laminin-511: a multi-functional adhesion protein regulating cell migration, tumor invasion and metastasis

Laminins are major constituents of basement membranes. At least 16 isoforms have now been described, each with distinct spatio-temporal expression patterns and functions. The laminin-511 heterotrimer (α5β1γ1) is one of the more recent isoforms to be identified and a potent adhesive and pro-migratory substrate for a variety of normal and tumor cell lines in vitro. As our understanding of its precise function in normal tissues and in pathologies is rapidly unraveling, current evidence suggests an important regulatory role in cancer. This review describes published data on laminin-511 expression in several malignancies and experimental evidence from both in vitro and in vivo studies supporting its functional role during tumor progression. A particular emphasis is put on more recent studies from our laboratory and that of others indicating that laminin-511 contributes to tumor dissemination and metastasis in advanced breast carcinomas and other tumor types. Collectively, the experimental evidence suggests that high expression of laminin-511 has prognostic significance and that targeting tumor-laminin-511 interactions may have therapeutic potential in advanced cancer patients.

Abnormal Wnt and PI3Kinase signaling in the malformed intestine of lama5 deficient mice

Laminins are major constituents of basement membranes and are essential for tissue homeostasis. Laminin-511 is highly expressed in the intestine and its absence causes severe malformation of the intestine and embryonic lethality. To understand the mechanistic role of laminin-511 in tissue homeostasis, we used RNA profiling of embryonic intestinal tissue of lama5 knockout mice and identified a lama5 specific gene expression signature. By combining cell culture experiments with mediated knockdown approaches, we provide a mechanistic link between laminin α5 gene deficiency and the physiological phenotype. We show that laminin α5 plays a crucial role in both epithelial and mesenchymal cell behavior by inhibiting Wnt and activating PI3K signaling. We conclude that conflicting signals are elicited in the absence of lama5, which alter cell adhesion, migration as well as epithelial and muscle differentiation. Conversely, adhesion to laminin-511 may serve as a potent regulator of known interconnected PI3K/Akt and Wnt signaling pathways. Thus deregulated adhesion to laminin-511 may be instrumental in diseases such as human pathologies of the gut where laminin-511 is abnormally expressed as it is shown here.

Breast cancer cell-derived matrix supports vascular morphogenesis

The extracellular matrix (ECM), important for maintaining tissue homeostasis, is abnormally expressed in mammary tumors and additionally plays a crucial role in angiogenesis. We hypothesize that breast cancer cells (BCCs) deposit ECM that supports unique patterns of vascular morphogenesis of endothelial cells (ECs). Evaluation of ECM expression revealed that a nontumorigenic cell line (MCF10A), a tumorigenic cell line (MCF7), and a metastatic cell line (MDA-MB-231) express collagens I and IV, fibronectin, and laminin, with tenascin-C limited to MCF10A and MCF7. The amount of ECM deposited by BCCs was found to be higher in MCF10A compared with MCF7 and MDA231, with all ECM differing in their gross structure but similar in mean fiber diameter. Nonetheless, deposition of ECM from BCC lines was overall difficult to detect and insufficient to support capillary-like structure (CLS) formation of ECs. Therefore, a coculture approach was undertaken in which individual BCC lines were cocultured with fibroblasts. Variation in abundance of deposited ECM, deposition of ECM proteins, such as absent collagen I deposition from MDA231-fibroblast cocultures, and fibril organization was found. Deposited ECM from fibroblasts and each coculture supported rapid CLS formation of ECs. Evaluation of capillary properties revealed that CLS grown on ECM deposited from MDA231-fibroblast cocultures possessed significantly larger lumen diameters, occupied the greatest percentage of area, expressed the highest levels of von Willebrand factor, and expressed the greatest amount of E-selectin, which was upregulated independent of exposure to TNF-α. To our knowledge, this is the first study to report tumor cell ECM-mediated differences in vascular capillary features, and thus offers the framework for future investigations interrogating the role of the tumor ECM in supporting vascular morphogenesis.

Genome-wide Runx2 occupancy in prostate cancer cells suggests a role in regulating secretion

Runx2 is a metastatic transcription factor (TF) increasingly expressed during prostate cancer (PCa) progression. Using PCa cells conditionally expressing Runx2, we previously identified Runx2-regulated genes with known roles in epithelial-mesenchymal transition, invasiveness, angiogenesis, extracellular matrix proteolysis and osteolysis. To map Runx2-occupied regions (R2ORs) in PCa cells, we first analyzed regions predicted to bind Runx2 based on the expression data, and found that recruitment to sites upstream of the KLK2 and CSF2 genes was cyclical over time. Genome-wide ChIP-seq analysis at a time of maximum occupancy at these sites revealed 1603 high-confidence R2ORs, enriched with cognate motifs for RUNX, GATA and ETS TFs. The R2ORs were distributed with little regard to annotated transcription start sites (TSSs), mainly in introns and intergenic regions. Runx2-upregulated genes, however, displayed enrichment for R2ORs within 40 kb of their TSSs. The main annotated functions enriched in 98 Runx2-upregulated genes with nearby R2ORs were related to invasiveness and membrane trafficking/secretion. Indeed, using SDS-PAGE, mass spectrometry and western analyses, we show that Runx2 enhances secretion of several proteins, including fatty acid synthase and metastasis-associated laminins. Thus, combined analysis of Runx2's transcriptome and genomic occupancy in PCa cells lead to defining its novel role in regulating protein secretion.

Integrin α3β1 as a breast cancer target

INTRODUCTION

Integrin receptors for cell adhesion to the extracellular matrix have important roles in all stages of cancer progression and metastasis. Since the integrin family was discovered in the early 1980's, many studies have identified critical adhesion and signaling functions for integrins expressed on tumor cells, endothelial cells and other cell types of the tumor microenvironment, in controlling proliferation, survival, migration and angiogenesis. In recent years, the laminin-binding integrin α3β1 has emerged as a potentially promising anti-cancer target on breast cancer cells.

AREAS COVERED

Studies from the past decade that implicate integrins as promising anti-cancer targets and the development of integrin antagonists as anti-cancer therapeutics. Recent preclinical studies that have identified the laminin-binding integrin α3β1 as an appealing anti-cancer target and the knowledge gaps that must be closed to fully exploit this integrin as a therapeutic target for breast cancer.

EXPERT OPINION

Although the tumor-promoting functions of α3β1 implicate this integrin as a promising therapeutic target on breast cancer cells, successful exploitation of this integrin as an anti-cancer target will require a better understanding of the molecular mechanisms whereby it regulates specific tumor cell behaviors and the identification of the most appropriate α3β1 functions to antagonize on breast cancer cells.

Integrin-dependent response to laminin-511 regulates breast tumor cell invasion and metastasis

The basement membrane protein, laminin (LM)-511, is a potent adhesive and migratory substrate for metastatic breast tumor cells in vitro. Its expression correlates with tumor grade and metastatic potential in vivo. These observations suggest that responsiveness to autocrine or paracrine-derived LM-511 may be an important property regulating breast cancer metastasis in vivo. To address this, we compared the metastatic potential of 4T1 mammary carcinoma cells to that of 4T1 variants isolated by repeated chemotactic migration toward LM-511 in vitro (4T1LMF4) followed by serial injection into the mammary gland and recovery of spontaneous metastases from bone (4T1BM2). Variant subpopulations exhibited a distinct morphology on LM-511 and increased expression of β1 and β4 integrins compared to parental 4T1 cells. Importantly, mice inoculated with 4T1LMF4 and 4T1BM2 variants showed a 2.5- to 4-fold increase in the incidence of spontaneous metastasis to bone compared to 4T1 tumor-bearing mice. Functionally, 4T1BM2 variants were more adherent and more invasive toward LM-511 than parental 4T1 cells. Treatment of 4T1BM2 cells with lebein-1, a disintegrin with selectivity toward LM-type integrin receptors, potently inhibited their migration and invasion toward LM-511. Similarly, α3β1 integrin-dependent migration and invasion of human MDA-MB-231 breast carcinoma cells toward LM-511 were significantly inhibited by lebein-1. Taken together, these results provide strong evidence that LM-511 contributes to the metastasis of breast tumors and suggest that targeting integrin-LM-511 interactions with lebein-1 or other inhibitors of LM-511 receptors may have therapeutic potential for patients with advanced breast cancer.

Analysis of cellular migration using a two-chamber methodology

Directed cell migration is fundamental to both physiological and pathophysiological processes such as embryogenesis, wound healing, and cancer metastasis. A complex series of events are required for directional cell migration, which is initiated by a migration-promoting or chemotactic stimulus, resulting in cellular polarization and entry into a cyclical pattern of leading edge protrusion, adhesion, and retraction of the trailing edge allowing cell movement. Heat shock proteins such as Hsp27, Hsp90, alphaB-crystallin, as well as heat shock transcription factors, are important players in both physiological and pathophysiological cell migration. A variety of techniques are currently available to assess cell migration, and among the most commonly utilized are those that employ a two-chamber methodology, such as that developed by Stephen Boyden in the early 1960s. Herein, we describe the use of a multiwell microchemotaxis migration assay that has the advantages of being reusable, inexpensive, highly reproducible, and requiring only a small volume of reagents.

Melanoma cells produce multiple laminin isoforms and strongly migrate on α5 laminin(s) via several integrin receptors

Melanoma cells express and interact with laminins (LMs) and other basement membrane components during invasion and metastasis. In the present study we have investigated the production and migration-promoting activity of laminin isoforms in melanoma. Immunohistochemistry of melanoma specimens and immunoprecipitation/western blotting of melanoma cell lines indicated expression of laminin-111/121, laminin-211, laminin-411/421, and laminin-511/521. Laminin-332 was not detected. In functional assays, laminin-111, laminin-332, and laminin-511, but not laminin-211 and laminin-411, strongly promoted haptotactic cell migration either constitutively or following stimulation with insulin-like growth factors. Both placenta and recombinant laminin-511 preparations were highly active, and the isolated recombinant IVa domain of LMα5 also promoted cell migration. Function-blocking antibodies in cell migration assays revealed α6β1 integrin as the major receptor for laminin-111, and both α3β1 and α6β1 integrins for laminin-332 and laminin-511. In contrast, isolated LMα5 IVa domain-promoted melanoma cell migration was largely mediated via αVβ3 integrin and inhibited by RGD peptides. Given the ubiquitous expression of α5 laminins in melanoma cells and in melanoma-target tissues/anatomical structures, as well as the strong migration-promoting activity of these laminin isoforms, the α5 laminins emerge as putative primary extracellular matrix mediators of melanoma invasion and metastasis via α3β1 and other integrin receptors.

Suppression of integrin alpha3beta1 in breast cancer cells reduces cyclooxygenase-2 gene expression and inhibits tumorigenesis, invasion, and cross-talk to endothelial cells

Integrin receptors for cell adhesion to extracellular matrix have important roles in promoting tumor growth and progression. Integrin alpha3beta1 is highly expressed in breast cancer cells in which it is thought to promote invasion and metastasis; however, its roles in regulating malignant tumor cell behavior remain unclear. In the current study, we used short-hairpin RNA (shRNA) to show that suppression of alpha3beta1 in a human breast cancer cell line, MDA-MB-231, leads to decreased tumorigenicity, reduced invasiveness, and decreased production of factors that stimulate endothelial cell migration. Real-time PCR revealed that suppression of alpha3beta1 caused a dramatic reduction in expression of the cyclooxygenase-2 (COX-2) gene, which is frequently overexpressed in breast cancers and has been exploited as a therapeutic target. Decreased COX-2 was accompanied by reduced prostaglandin E2 (PGE(2)), a major prostanoid produced downstream of COX-2 and an important effector of COX-2 signaling. shRNA-mediated suppression of COX-2 showed that it has a role in tumor cell invasion and cross-talk to endothelial cells. Furthermore, treatment with PGE(2) restored these functions in alpha3beta1-deficient MDA-MB-231 cells. These findings identify a role for alpha3beta1 in regulating two properties of tumor cells that facilitate cancer progression: invasiveness and ability to stimulate endothelial cells. They also reveal a novel role for COX-2 as a downstream effector of alpha3beta1 in tumor cells, thereby identifying alpha3beta1 as a potential therapeutic target to inhibit breast cancer.

Disruption of laminin-integrin-CD151-focal adhesion kinase axis sensitizes breast cancer cells to ErbB2 antagonists

Resistance to anti-ErbB2 agents is a significant problem in the treatment of human ErbB2+ breast cancers. We show here that adhesion of human ErbB2+ breast cancer cells to basement membrane laminin-5 provides substantial resistance to trastuzumab and lapatinib, agents that respectively target the extracellular and kinase domains of ErbB2. Knockdown of laminin-binding integrins (alpha6beta4, alpha3beta1) or associated tetraspanin protein CD151 reversed laminin-5 resistance and sensitized ErbB2+ cells to trastuzumab and lapatinib. CD151 knockdown, together with trastuzumab treatment, inhibited ErbB2 activation and downstream signaling through Akt, Erk1/2, and focal adhesion kinase (FAK). Hence, ErbB2 function in mammary tumor cells is promoted by integrin-mediated adhesion to laminin-5, with strong support by CD151, leading to signaling through FAK. Consequently, removal or inhibition of any of these components (laminin-5, integrin, CD151, FAK) markedly sensitizes cells to anti-ErbB2 agents. These new insights should be useful when devising strategies for overcoming drug resistance in ErbB2+ cancers.

Role of dermal-epidermal basement membrane zone in skin, cancer, and developmental disorders

The dermal-epidermal basement membrane zone is an important epithelial and stromal interface, consisting of an intricately organized collection of intracellular, transmembrane, and extracellular matrix proteins. The basement membrane zone has several main functions including acting as a permeability barrier, forming an adhesive interface between epithelial cells and the underlying matrix, and controlling cellular organization and differentiation. This article identifies key molecular players of the dermal-epidermal membrane zone, and highlights recent research studies that have identified structural and functional roles of these components in the context of various blistering, neoplastic, and developmental syndromes.

Stromal cell expression of caveolin-1 predicts outcome in breast cancer

Caveolin-1 has been linked to tumor progression and clinical outcome in breast cancer, but a clear resolution of its role as a prognostic marker is lacking. We assessed caveolin-1 levels in normal breast tissue and two breast cancer cohorts for which outcome data were available. We found that caveolin-1 was not expressed in normal breast luminal epithelium but was present in the epithelial compartment of some tumors. We found no association between caveolin-1 expression in the epithelial compartment and clinical outcome. However, high levels of caveolin-1 in the stromal tissue surrounding the tumor, rather than within tumor cells, associated strongly with reduced metastasis and improved survival (P < 0.0001). The onset of mammary tumors driven by Her2/neu overexpression was accelerated in mice lacking caveolin-1, thereby supporting the observation that the presence of caveolin-1 in the tumor microenvironment modulates tumor development. These studies suggest that stromal caveolin-1 expression may be a potential therapeutic target and a valuable prognostic indicator of breast cancer progression.