Proteolytic and non-proteolytic regulation of collective cell invasion: tuning by ECM density and organization

A Simple Framework for Agent-Based Modeling with Extracellular Matrix

Extracellular matrix (ECM) is a key component of the cellular microenvironment and critical in multiple disease and developmental processes. Representing ECM and cell-ECM interactions is a challenging multiscale problem as they span molecular-level details to tissue-level dynamics. While several computational frameworks exist for ECM modeling, they often focus on very detailed modeling of individual ECM fibers or represent only a single aspect of the ECM. Using the PhysiCell agent-based modeling platform, we developed a framework of intermediate detail with the ability to capture bidirectional cell-ECM interactions. We represent a small region of ECM, an ECM element, with three variables describing its local microstructure: anisotropy, density, and overall fiber orientation. To spatially model the ECM, we use an array of ECM elements. Cells remodel local ECM microstructure and in turn, local microstructure impacts cellular motility. We demonstrate the utility of this framework and reusability of its core cell-ECM interaction model through examples in cellular invasion, wound healing, basement membrane degradation, and leader-follower collective migration. Despite the relative simplicity of the framework, it is able to capture a broad range of cell-ECM interactions of interest to the modeling community. Furthermore, variables representing the ECM microstructure are accessible through simple programming interfaces. This allows them to impact cell behaviors, such as proliferation and death, without requiring custom code for each interaction, particularly through PhysiCell's modeling grammar, enabling rapid modeling of a diverse range of cell-matrix biology. We make this framework available as a free and open source software package at https://github.com/PhysiCell-Models/collective-invasion .

The Orphan G Protein-Coupled Receptor GPR52 is a Novel Regulator of Breast Cancer Multicellular Organization

G protein-coupled receptors (GPCRs) are the largest class of membrane-bound receptors and transmit critical signals from the extracellular to the intracellular spaces. Transcriptomic data of resected breast tumors shows that low mRNA expression of the orphan GPCR GPR52 correlates with reduced overall survival in breast cancer patients, leading to the hypothesis that loss of GPR52 supports breast cancer progression. CRISPR-Cas9 was used to knockout GPR52 in human triple-negative breast cancer (TNBC) cell lines MDA-MB-468 and MDA-MB-231, and in the non-cancerous breast epithelial cell line, MCF10A. Loss of GPR52 was found to be associated with increased cell-cell interaction in 2D cultures, altered 3D spheroid morphology, and increased propensity to organize and invade collectively in Matrigel. Furthermore, GPR52 loss was associated with features of EMT in MDA-MB-468 cells. To determine the in vivo impact of GPR52 loss, MDA-MB-468 cells were injected into zebrafish and loss of GPR52 was associated with a greater total cancer area compared to control cells. RNA-sequencing and proteomic analyses of GPR52-null breast cancer cells reveal an increased cAMP signaling signature. Consistently, we found that treatment of wild-type (WT) cells with forskolin, which stimulates production of cAMP, induces some phenotypic changes associated with GPR52 loss, and inhibition of cAMP production rescued some of the GPR52 KO phenotypes. Overall, our results reveal GPR52 loss as a potential mechanism by which breast cancer progression may occur and support the investigation of GPR52 agonism as a therapeutic option in breast cancer.

Distinct spectral signatures unfold ECM stiffness-triggered biochemical changes in breast cancer cells

Cancer progression often accompanies the stiffening of extracellular matrix (ECM) in and around the tumor, owing to extra deposition and cross-linking of collagen. Stiff ECM has been linked with poor prognosis and is known to fuel invasion and metastasis, notably in breast cancer. However, the underlying biochemical or metabolic changes and the cognate molecular signatures remain elusive. Here, we explored Raman spectroscopy to unveil the spectral fingerprints of breast cancer cells in response to extracellular mechanical cues. Using stiffness-tuneable hydrogels, we showed that cells grown on stiff ECM displayed morphological changes with high proliferation. We further demonstrated that Raman Spectroscopy, a label-free and non-invasive technique, could provide comprehensive information about the biochemical environment of breast cancer cells in response to varying ECM stiffness. Raman spectroscopic analysis classified the cells into distinct clusters based on principal component-based linear discriminant analysis (PC-LDA). Multivariate curve resolution-alternating least squares (MCR-ALS) analysis indicated that cells cultured on stiff ECM exhibited elevated nucleic acid content and lesser lipids. Interestingly, increased intensity of Raman bands corresponding to cytochrome-c was also observed in stiff ECM conditions, suggesting mitochondrial modulation. The key findings harboured by spectral profiles were also corroborated by transmission electron microscopy, confirming altered metabolic status as reflected by increased mitochondria number and decreased lipid droplets in response to ECM stiffening. Collectively, these findings not only give the spectral signatures for mechanoresponse but also provide the landscape of biochemical changes in response to ECM stiffening.

Multiscale computational modeling of aortic valve calcification

Calcific aortic valve disease (CAVD) is a common cardiovascular disease that affects millions of people worldwide. The disease is characterized by the formation of calcium nodules on the aortic valve leaflets, which can lead to stenosis and heart failure if left untreated. The pathogenesis of CAVD is still not well understood, but involves several signaling pathways, including the transforming growth factor beta (TGF β ) pathway. In this study, we developed a multiscale computational model for TGF β -stimulated CAVD. The model framework comprises cellular behavior dynamics, subcellular signaling pathways, and tissue-level diffusion fields of pertinent chemical species, where information is shared among different scales. Processes such as endothelial to mesenchymal transition (EndMT), fibrosis, and calcification are incorporated. The results indicate that the majority of myofibroblasts and osteoblast-like cells ultimately die due to lack of nutrients as they become trapped in areas with higher levels of fibrosis or calcification, and they subsequently act as sources for calcium nodules, which contribute to a polydispersed nodule size distribution. Additionally, fibrosis and calcification processes occur more frequently in regions closer to the endothelial layer where the cell activity is higher. Our results provide insights into the mechanisms of CAVD and TGF β signaling and could aid in the development of novel therapeutic approaches for CAVD and other related diseases such as cancer. More broadly, this type of modeling framework can pave the way for unraveling the complexity of biological systems by incorporating several signaling pathways in subcellular models to simulate tissue remodeling in diseases involving cellular mechanobiology.

Modeling the extracellular matrix in cell migration and morphogenesis: a guide for the curious biologist

The extracellular matrix (ECM) is a highly complex structure through which biochemical and mechanical signals are transmitted. In processes of cell migration, the ECM also acts as a scaffold, providing structural support to cells as well as points of potential attachment. Although the ECM is a well-studied structure, its role in many biological processes remains difficult to investigate comprehensively due to its complexity and structural variation within an organism. In tandem with experiments, mathematical models are helpful in refining and testing hypotheses, generating predictions, and exploring conditions outside the scope of experiments. Such models can be combined and calibrated with in vivo and in vitro data to identify critical cell-ECM interactions that drive developmental and homeostatic processes, or the progression of diseases. In this review, we focus on mathematical and computational models of the ECM in processes such as cell migration including cancer metastasis, and in tissue structure and morphogenesis. By highlighting the predictive power of these models, we aim to help bridge the gap between experimental and computational approaches to studying the ECM and to provide guidance on selecting an appropriate model framework to complement corresponding experimental studies.

Interplay of adherens junctions and matrix proteolysis determines the invasive pattern and growth of squamous cell carcinoma

Cancers, such as squamous cell carcinoma, frequently invade as multicellular units. However, these invading units can be organised in a variety of ways, ranging from thin discontinuous strands to thick 'pushing' collectives. Here we employ an integrated experimental and computational approach to identify the factors that determine the mode of collective cancer cell invasion. We find that matrix proteolysis is linked to the formation of wide strands but has little effect on the maximum extent of invasion. Cell-cell junctions also favour wide strands, but our analysis also reveals a requirement for cell-cell junctions for efficient invasion in response to uniform directional cues. Unexpectedly, the ability to generate wide invasive strands is coupled to the ability to grow effectively when surrounded by extracellular matrix in three-dimensional assays. Combinatorial perturbation of both matrix proteolysis and cell-cell adhesion demonstrates that the most aggressive cancer behaviour, both in terms of invasion and growth, is achieved at high levels of cell-cell adhesion and high levels of proteolysis. Contrary to expectation, cells with canonical mesenchymal traits - no cell-cell junctions and high proteolysis - exhibit reduced growth and lymph node metastasis. Thus, we conclude that the ability of squamous cell carcinoma cells to invade effectively is also linked to their ability to generate space for proliferation in confined contexts. These data provide an explanation for the apparent advantage of retaining cell-cell junctions in squamous cell carcinomas.

Development of a coupled modeling for tumor growth, angiogenesis, oxygen delivery, and phenotypic heterogeneity

Analysis of the evolution and growth dynamics of tumors is crucial for understanding cancer and the development of individually optimized therapies. During tumor growth, a hypoxic microenvironment around cancer cells caused by excessive non-vascular tumor growth induces tumor angiogenesis that plays a key role in the ensuing tumor growth and its progression into higher stages. Various mathematical simulation models have been introduced to simulate these biologically and physically complex hallmarks of cancer. Here, we developed a hybrid two-dimensional computational model that integrates spatiotemporally different components of the tumor system to investigate both angiogenesis and tumor growth/proliferation. This spatiotemporal evolution is based on partial diffusion equations, the cellular automation method, transition and probabilistic rules, and biological assumptions. The new vascular network provided by angiogenesis affects tumor microenvironmental conditions and drives individual cells to adapt themselves to spatiotemporal conditions. Furthermore, some stochastic rules are involved besides microenvironmental conditions. Overall, the conditions promote some commonly observed cellular states, i.e., proliferative, migrative, quiescent, and cell death, depending on the condition of each cell. Altogether, our results offer a theoretical basis for the biological evidence that regions of the tumor tissue near blood vessels are densely populated by proliferative phenotypic variants, while poorly oxygenated regions are sparsely populated by hypoxic phenotypic variants.

Unusual Suspects: Bone and Cartilage ECM Proteins as Carcinoma Facilitators

The extracellular matrix (ECM) is the complex three-dimensional network of fibrous proteins and proteoglycans that constitutes an essential part of every tissue to provide support for normal tissue homeostasis. Tissue specificity of the ECM in its topology and structure supports unique biochemical and mechanical properties of each organ. Cancers, like normal tissues, require the ECM to maintain multiple processes governing tumor development, progression and spread. A large body of experimental and clinical evidence has now accumulated to demonstrate essential roles of numerous ECM components in all cancer types. Latest findings also suggest that multiple tumor types express, and use to their advantage, atypical ECM components that are not found in the cancer tissue of origin. However, the understanding of cancer-specific expression patterns of these ECM proteins and their exact roles in selected tumor types is still sketchy. In this review, we summarize the latest data on the aberrant expression of bone and cartilage ECM proteins in epithelial cancers and their specific functions in the pathogenesis of carcinomas and discuss future directions in exploring the utility of this selective group of ECM components as future drug targets.

The modeling study of the effect of morphological behaviors of extracellular matrix fibers on the dynamic interaction between tumor cells and antitumor immune response

Low response rate limits the effective application of immunotherapy, in which the interactions between tumor cells and immune cells play a significant role. The strength of regulation could be mediated by extracellular matrix (ECM) fibers, which is still insufficiently investigated. In the study, the cellular potts model was utilized to explore the role of morphological properties of ECM in tumor-immune interactions. It was observed that high-density random ECM fibers delayed the interaction between tumor cells and T cells. Moreover, the tumor-immune interactions were ECM morphology-specific. Radial ECM fibers exhibited weaker inhibitory role in the process of contact between tumor cells and T cells. This study provided the useful mechanism of tumor-immune interactions from the viewpoint of morphological effect of ECM fibers, facilitating improving the efficiency of immunotherapy.

Text-Mining Approach to Identify Hub Genes of Cancer Metastasis and Potential Drug Repurposing to Target Them

Metastasis accounts for the majority of cancer-related deaths. Despite decades of research, the prevention and suppression of metastasis remain an elusive goal, and to date, only a few metastasis-related genes have been targeted therapeutically. Thus, there is a strong need to find potential genes involved in key driver traits of metastasis and their available drugs. In this study, we identified genes associated with metastasis and repurposable drugs that potentially target them. First, we use text mining of PubMed citations to identify candidate genes associated with metastatic processes, such as invadopodia, motility, movement, metastasis, invasion, wound healing, EMT (epithelial to mesenchymal transition), and podosome. Next, we annotated the top genes involved in each process as a driver, tumor suppressor, or oncogene. Then, a total of 185 unique cancer genes involved in metastasis-related processes were used for hub gene analysis using bioinformatics tools. Notably, a total of 77 hub genes were identified. Further, we used virtual screening data of druggable candidate hub genes involved in metastasis and identified potential drugs that can be repurposed as anti-metastatic drugs. Remarkably, we found a total of 50 approved drugs that have the potential to be repurposed against 19 hub genes involved in metastasis-related processes. These 50 drugs were also found to be validated in different cancer cell lines, such as dasatinib, captopril, leflunomide, and dextromethorphan targeting SRC, MMP2, PTK2B, and RAC1 hub genes, respectively. These repurposed drugs potentially target metastasis, provide pharmacodynamic insight, and offer a window of opportunity for the development of much-needed antimetastatic drugs.

Cluster size distribution of cells disseminating from a primary tumor

The first stage of the metastatic cascade often involves motile cells emerging from a primary tumor either as single cells or as clusters. These cells enter the circulation, transit to other parts of the body and finally are responsible for growth of secondary tumors in distant organs. The mode of dissemination is believed to depend on the EMT nature (epithelial, hybrid or mesenchymal) of the cells. Here, we calculate the cluster size distribution of these migrating cells, using a mechanistic computational model, in presence of different degree of EMT-ness of the cells; EMT is treated as given rise to changes in their active motile forces (μ) and cell-medium surface tension (Γ). We find that, for (μ > μ_min, Γ > 1), when the cells are hybrid in nature, the mean cluster size, N¯∼Γ2.0/μ2.8, where μ_min increases with increase in Γ. For Γ ≤ 0, N¯=1, the cells behave as completely mesenchymal. In presence of spectrum of hybrid states with different degree of EMT-ness (motility) in primary tumor, the cells which are relatively more mesenchymal (higher μ) in nature, form larger clusters, whereas the smaller clusters are relatively more epithelial (lower μ). Moreover, the heterogeneity in μ is comparatively higher for smaller clusters with respect to that for larger clusters. We also observe that more extended cell shapes promote the formation of smaller clusters. Overall, this study establishes a framework which connects the nature and size of migrating clusters disseminating from a primary tumor with the phenotypic composition of the tumor, and can lead to the better understanding of metastasis.

In the process of metastasis, tumor cells disseminate from the primary tumor either as single cells or multicellular clusters. These clusters are potential contributor to the initiation of secondary tumor in distant organs. Our computational model captures the size distribution of migrating clusters depending on the adhesion and motility of the cells (which determine the degree of their EMT nature). Furthermore, we investigate the effect of heterogeneity of cell types in the primary tumor on the resultant heterogeneity of cell types in clusters of different sizes. We believe that the understanding the formation and nature of these clusters, dangerous actors in the deadly aspect of cancer progression, will be useful for improving prognostic methods and eventually better treatments.

Manipulating Extracellular Matrix Organizations and Parameters to Control Local Cancer Invasion

Metastasis contributes to over 90 percent of cancer mortalities and may be influenced by the extracellular matrix (ECM). ECM microenvironments differ in matrix organization, cell-matrix adhesions, and fiber rigidity, which may affect cancer migration and, thus, should be investigated. To understand the interactions between cancer cells and the ECM, we simulate local invasion through ECM organizations of varying determinants. Randomly curved organizations of normal ovarian stroma exhibit minimal local invasion. In contrast, wave-like and parallel linear structures in reorganized ECM organizations provide contact guidance, which increases cancer invasiveness. ECM organizations with strong cell-matrix attachments generate cell pseudopodia, which aid in increasing invasion rate, while weaker attachments prevent the cells from attaching to the fibers and forming pseudopodia, limiting local invasion. ECM organizations with rigid fibers elongate the cell body, allowing them to form cell protrusions and spread rapidly. Conversely, soft fibers stimulate cell rounding and limit migration. Optimizing cell-matrix adhesions and fiber rigidity results in below 10 percent local invasion and reinforces the importance of using computational modeling to discover novel approaches to restricting cancer movement.

Multiscale modeling in disease

Multiscale computational modeling aims to connect the complex networks of effects at different length and/or time scales. For example, these networks often include intracellular molecular signaling, crosstalk, and other interactions between neighboring cell populations, and higher levels of emergent phenomena across different regions of tissues and among collections of tissues or organs interacting with each other in the whole body. Recent applications of multiscale modeling across intracellular, cellular, and/or tissue levels are highlighted here. These models incorporated the roles of biochemical and biomechanical modulation in processes that are implicated in the mechanisms of several diseases including fibrosis, joint and bone diseases, respiratory infectious diseases, and cancers.

Mechanical Pressure Driving Proteoglycan Expression in Mammographic Density: a Self-perpetuating Cycle?

Regions of high mammographic density (MD) in the breast are characterised by a proteoglycan (PG)-rich fibrous stroma, where PGs mediate aligned collagen fibrils to control tissue stiffness and hence the response to mechanical forces. Literature is accumulating to support the notion that mechanical stiffness may drive PG synthesis in the breast contributing to MD. We review emerging patterns in MD and other biological settings, of a positive feedback cycle of force promoting PG synthesis, such as in articular cartilage, due to increased pressure on weight bearing joints. Furthermore, we present evidence to suggest a pro-tumorigenic effect of increased mechanical force on epithelial cells in contexts where PG-mediated, aligned collagen fibrous tissue abounds, with implications for breast cancer development attributable to high MD. Finally, we summarise means through which this positive feedback mechanism of PG synthesis may be intercepted to reduce mechanical force within tissues and thus reduce disease burden.

Matrix adhesion and remodeling diversifies modes of cancer invasion across spatial scales

The metastasis of malignant epithelial tumors begins with the egress of transformed cells from the confines of their basement membrane (BM) to their surrounding collagen-rich stroma. Invasion can be morphologically diverse: when breast cancer cells are separately cultured within BM-like matrix, collagen I (Coll I), or a combination of both, they exhibit collective-, dispersed mesenchymal-, and a mixed collective-dispersed (multimodal)- invasion, respectively. In this paper, we asked how distinct these invasive modes are with respect to the cellular and microenvironmental cues that drive them. A rigorous computational exploration of invasion was performed within an experimentally motivated Cellular Potts-based modeling environment. The model comprised of adhesive interactions between cancer cells, BM- and Coll I-like extracellular matrix (ECM), and reaction-diffusion-based remodeling of ECM. The model outputs were parameters cognate to dispersed- and collective- invasion. A clustering analysis of the output distribution curated through a careful examination of subsumed phenotypes suggested at least four distinct invasive states: dispersed, papillary-collective, bulk-collective, and multimodal, in addition to an indolent/non-invasive state. Mapping input values to specific output clusters suggested that each of these invasive states are specified by distinct input signatures of proliferation, adhesion and ECM remodeling. In addition, specific input perturbations allowed transitions between the clusters and revealed the variation in the robustness between the invasive states. Our systems-level approach proffers quantitative insights into how the diversity in ECM microenvironments may steer invasion into diverse phenotypic modes during early dissemination of breast cancer and contributes to tumor heterogeneity.

Combined heterogeneity in cell size and deformability promotes cancer invasiveness

Phenotypic heterogeneity is increasingly acknowledged to confer several advantages to cancer progression and drug resistance. Here, we probe the collective importance of heterogeneity in cell size and deformability in breast cancer invasion. A computational model of invasion of a heterogeneous cell aggregate predicts that combined heterogeneity in cell size and deformability enhances invasiveness of the whole population, with maximum invasiveness at intermediate cell-cell adhesion. We then show that small cells of varying deformability, a subpopulation predicted to be enriched at the invasive front, exhibit considerable overlap with the biophysical properties of cancer stem cells (CSCs). In MDA-MB-231 cells, these include CD44 ^hi CD24^- mesenchymal CSCs, which are small and soft, and CD44 ^hi CD24⁺ hybrid CSCs, which exhibit a wide range of size and deformability. We validate our predictions by tracking the pattern of cell invasion from spheroids implanted in three-dimensional collagen gels, wherein we show temporal enrichment of CD44 ^hi cells at the invasive front. Collectively, our results illustrate the advantages imparted by biophysical heterogeneity in enhancing cancer invasiveness.This article has an associated First Person interview with the first author of the paper.

Heterogeneity in 2,6-Linked Sialic Acids Potentiates Invasion of Breast Cancer Epithelia

Heterogeneity in phenotypes of malignantly transformed cells and aberrant glycan expression on their surface are two prominent hallmarks of cancers that have hitherto not been linked to each other. In this paper, we identify differential levels of a specific glycan linkage: α2,6-linked sialic acids within breast cancer cells in vivo and in culture. Upon sorting out two populations with moderate, and relatively higher, cell surface α2,6-linked sialic acid levels from the triple-negative breast cancer cell line MDA-MB-231, both populations (denoted as medium and high 2,6-Sial cells, respectively) stably retained their levels in early passages. Upon continuous culturing, medium 2,6-Sial cells recapitulated the heterogeneity of the unsorted line whereas high 2,6-Sial cells showed no such tendency. Compared with high 2,6-Sial cells, the medium 2,6-Sial counterparts showed greater adhesion to reconstituted extracellular matrices (ECMs) and invaded faster as single cells. The level of α2,6-linked sialic acids in the two sublines was found to be consistent with the expression of a specific glycosyl transferase, ST6GAL1. Stably knocking down ST6GAL1 in the high 2,6-Sial cells enhanced their invasiveness. When cultured together, medium 2,6-Sial cells differentially migrated to the edge of growing tumoroid-like cocultures, whereas high 2,6-Sial cells formed the central bulk. Multiscale simulations in a Cellular Potts model-based computational environment calibrated to our experimental findings suggest that differential levels of cell-ECM adhesion, likely regulated by α2,6-linked sialic acids, facilitate niches of highly invasive cells to efficiently migrate centrifugally as the invasive front of a malignant breast tumor.

Tactics of cancer invasion: solitary and collective invasion

Much attention has been paid on the mechanism of cancer invasion from the viewpoint of the behaviour of individual cancer cells. On the other hand, histopathological analyses of specimens from cancer patients and of cancer invasion model animals have revealed that cancer cells often exhibit collective invasion, characterized by sustained cell-to-cell adhesion and polarized invasion as cell clusters. Interestingly, it has recently become evident that during collective invasion of cancer cells, the cells localized at invasion front (leader cells) and the cells following them (follower cells) exhibit distinct cellular characteristics, and that there exist the cells expressing representative proteins related to both epithelial and mesenchymal properties simultaneously, designated as hybrid epithelial-to-mesenchymal transition (EMT)-induced cells, in cancer tissue. Furthermore, the findings that cells adopted in hybrid EMT state form clusters and show collective invasion in vitro emphasize an importance of hybrid EMT-induced cells in collective cancer invasion. In this article, we overview recent findings of the mechanism underlying collective invasion of cancer cells and discuss the possibility of controlling cancer invasion and metastasis by targeting this process.

Blockage of Squamous Cancer Cell Collective Invasion by FAK Inhibition Is Released by CAFs and MMP-2

Simple Summary

Cancers include a diverse collection of cells harboring distinct molecular signatures with different levels of pro-metastatic activities. This intratumoral heterogeneity and phenotypic plasticity are major causes of targeted therapeutic failure and it should be considered when developing prognostic tests. Through the analysis of the Focal Adhesion Kinase (FAK) protein and the matrix metalloprotease MMP-2, both implicated in multiple steps of the metastatic spectrum, in complex multicellular tumor spheroids we show that cancer cell populations over-expressing MMP-2 or cancer-associated fibroblasts can release FAK-deficient cancer cells from their constrained metastatic fitness. Consistently, MMP-2, not FAK, serves as an independent prognostic factor in head and neck squamous cell carcinomas. Measurement of intratumor heterogeneity facilitate the development of more efficient biomarkers to predict the risk of metastasis and of more-effective personalized cancer therapies.

Abstract

Metastasis remains a clinically unsolved issue in cancer that is initiated by the acquisition of collective migratory properties of cancer cells. Phenotypic and functional heterogeneity that arise among cancer cells within the same tumor increase cellular plasticity and promote metastasis, however, their impact on collective cell migration is incompletely understood. Here, we show that in vitro collective cancer cell migration depends on FAK and MMP-2 and on the presence of cancer-associated fibroblasts (CAFs). The absence of functional FAK rendered cancer cells incapable of invading the surrounding stroma. However, CAFs and cancer cells over-expressing MMP-2 released FAK-deficient cells from this constraint by taking the leader positions in the invasive tracks, pushing FAK-deficient squamous cell carcinoma (SCC) cells towards the stroma and leading to the transformation of non-invasive cells into invasive cells. Our cell-based studies and the RNAseq data from the TCGA cohort of patients with head and neck squamous cell carcinomas reveal that, although both FAK and MMP-2 over-expression are associated with epithelial–mesenchymal transition, it is only MMP-2, not FAK, that functions as an independent prognostic factor. Given the significant role of MMP-2 in cancer dissemination, targeting of this molecule, better than FAK, presents a more promising opportunity to block metastasis.

Plasticity of cancer cell invasion: Patterns and mechanisms

Cancer cell migration and invasion are integral components of metastatic disease, which is the major cause of death in cancer patients. Cancer cells can disseminate and migrate via several alternative mechanisms including amoeboid cell migration, mesenchymal cell migration, and collective cell migration. These diverse movement strategies display certain specific and distinct hallmarks in cell-cell junctions, actin cytoskeleton, matrix adhesion, and protease activity. During tumor progression, cells pass through complex microenvironments and adapt their migration strategies by reversible mesenchymal-amoeboid and individual-collective transitions. This plasticity in motility patterns enables cancer cells disseminate further and thus limit the efficiency of anti-metastasis therapies. In this review, we discuss the modes and mechanisms of cancer cell migration and focus on the plasticity of tumor cell movement as well as potential emerging therapeutic options for reducing cancer cell invasion.

COL4A family: potential prognostic biomarkers and therapeutic targets for gastric cancer

Background

The type IV collagen alpha chain (COL4A) family is a major component of the basement membrane (BM) that has recently been found to be involved in tumor angiogenesis and progression. However, the expression levels and the exact roles of distinct COL4A family members in gastric cancer (GC) have not been completely understood.

Methods

Here, the expression levels of COL4As in GC and normal gastric tissues were calculated by using TCGA datasets and the predicted prognostic values by the GEPIA tool. Furthermore, the cBioPortal and Metascape tools were integrated to analyze the genetic alterations, correlations and potential functions of COL4As, and their frequently altered neighboring genes in GC.

Results

Notably, the expression levels of COL4A1/2/4 in GC were higher to those in normal gastric tissues, while the expression levels of COL4A3/5/6 were lower in GC than normal. Survival analysis revealed that lower expression levels of COL4A1/5 led to higher overall survival (OS) rate. Multivariate analysis using the Cox proportional-hazards model indicated that age, gender, pathological grade, metastasis and COL4A5 expression, are independent prognostic factors for OS. However, TNM stage, lymph node metastasis, Lauren’s classification, COL4A1-4 and COL4A6 were associated with poor OS but not independent prognostic factors. Function-enriched analysis of COL4As and their frequently altered neighboring genes was involved in tumor proliferation and metastasis in GC.

Conclusions

These results implied that COL4A1/2 were potential therapeutic targets for GC. COL4A3/4/6 might have an impact on gastric carcinogenesis and subsequent progression, whereas COL4A5 was an independent prognostic marker for GC.

The prognostic value and potential mechanism of Matrix Metalloproteinases among Prostate Cancer

Background: Matrix Metalloproteinases (MMPs) play an indispensable role in the initial alteration and development of PCa. We tried to generate an MMP-related prognostic signature (MMPS) in prostate cancer (PCa). Methods: TCGA-PRAD, MSKCC/GSE21032, GSE116918, GSE70769 cohorts were enrolled to assess the prognostic value of MMPs. The least absolute shrinkage and selection operator (LASSO) Cox regression was employed to generate the MMPS signature. The log-rank test and Kaplan-Meier (K-M) survival curve were applied to show the difference RFS, The receiver operating characteristic (ROC) curve and area under the ROC curve (AUC) was plotted to predict the accuracy of signature. CIBERSORT was conducted to analyze the different immune infiltration in MMPS-H and MMPS-L groups. Potential signaling pathways activated in the MMPS-H groups by Metascape. Results: MMP1, MMP7, MMP11, MMP24 and MMP26 were selected by LASSO regression and established the MMPS predict signature. The MMPS showed the high prognostic value in TCGA-PRAD training cohort (AUC=0.714) and validation cohorts (GSE116918: AUC=0.976, GSE70769: AUC=0.738, MSKCC: AUC=0.793). Pid integrin1 pathway, G2M checkpoint, and response to growth factor signaling pathways were activated in MMPS-H group, patients with the high MMPS risk score and low M2 macrophage showed the worst recurrence-free survival (RFS). Conclusion: MMPs involved and played an essential role in the tumorigenesis and biochemical recurrence in PCa patients. The MMPS signature could accurately predict the recurrence of PCa patients and validated in several cohorts.

Matrix degradation regulates osteoblast protrusion dynamics and individual migration

Protrusions are one of the structures that cells use to sense their surrounding environment in a probing and exploratory manner as well as to communicate with other cells. In particular, osteoblasts embedded within a 3D matrix tend to originate a large number of protrusions compared to other type of cells. In this work, we study the role that mechanochemical properties of the extracellular matrix (ECM) play on the dynamics of these protrusions, namely, the regulation of the size and number of emanating structures. In addition, we also determine how the dynamics of the protrusions may lead the 3D movement of the osteoblasts. Significant differences were found in protrusion size and cell velocity, when degradation activity due to metalloproteases was blocked by means of an artificial broad-spectrum matrix metalloproteinase inhibitor, whereas stiffening of the matrix by introducing transglutaminase crosslinking, only induced slight changes in both protrusion size and cell velocity, suggesting that the ability of cells to create a path through the matrix is more critical than the matrix mechanical properties themselves. To confirm this, we developed a cell migration computational model in 3D including both the mechanical and chemical properties of the ECM as well as the protrusion mechanics, obtaining good agreement with experimental results.

Adhesion modulates cell morphology and migration within dense fibrous networks

One of the most fundamental abilities required for the sustainability of complex life forms is active cell migration, since it is essential in diverse processes from morphogenesis to leukocyte chemotaxis in immune response. The movement of a cell is the result of intricate mechanisms, that involve the coordination between mechanical forces, biochemical regulatory pathways and environmental cues. In particular, epithelial cancer cells have to employ mechanical strategies in order to migrate through the tissue's basement membrane and infiltrate the bloodstream during the invasion stage of metastasis. In this work we explore how mechanical interactions such as spatial restriction and adhesion affect migration of a self-propelled droplet in dense fibrous media. We have performed a systematic analysis using a phase-field model and we propose a novel approach to simulate cell migration with dissipative particle dynamics modelling. With this purpose we have measured in our simulation the cell's velocity and quantified its morphology as a function of the fibre density and of its adhesiveness to the matrix fibres. Furthermore, we have compared our results to a previousin vitromigration assay of fibrosarcoma cells in fibrous matrices. The results show good agreement between the two methodologies and experiments in the literature, which indicates that these minimalist descriptions are able to capture the main features of the system. Our results indicate that adhesiveness is critical for cell migration, by modulating cell morphology in crowded environments and by enhancing cell velocity. In addition, our analysis suggests that matrix metalloproteinases (MMPs) play an important role as adhesiveness modulators. We propose that new assays should be carried out to address the role of adhesion and the effect of different MMPs in cell migration under confined conditions.

PhysiBoSS: a multi-scale agent-based modelling framework integrating physical dimension and cell signalling

MOTIVATION

Due to the complexity and heterogeneity of multicellular biological systems, mathematical models that take into account cell signalling, cell population behaviour and the extracellular environment are particularly helpful. We present PhysiBoSS, an open source software which combines intracellular signalling using Boolean modelling (MaBoSS) and multicellular behaviour using agent-based modelling (PhysiCell).

RESULTS

PhysiBoSS provides a flexible and computationally efficient framework to explore the effect of environmental and genetic alterations of individual cells at the population level, bridging the critical gap from single-cell genotype to single-cell phenotype and emergent multicellular behaviour. PhysiBoSS thus becomes very useful when studying heterogeneous population response to treatment, mutation effects, different modes of invasion or isomorphic morphogenesis events. To concretely illustrate a potential use of PhysiBoSS, we studied heterogeneous cell fate decisions in response to TNF treatment. We explored the effect of different treatments and the behaviour of several resistant mutants. We highlighted the importance of spatial information on the population dynamics by considering the effect of competition for resources like oxygen.

AVAILABILITY AND IMPLEMENTATION

PhysiBoSS is freely available on GitHub (https://github.com/sysbio-curie/PhysiBoSS), with a Docker image (https://hub.docker.com/r/gletort/physiboss/). It is distributed as open source under the BSD 3-clause license.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

An Interplay Between Reaction-Diffusion and Cell-Matrix Adhesion Regulates Multiscale Invasion in Early Breast Carcinomatosis

The progression of cancer in the breast involves multiple reciprocal interactions between malignantly transformed epithelia, surrounding untransformed but affected stromal cells, and the extracellular matrix (ECM) that is remodeled during the process. A quantitative understanding of the relative contribution of such interactions to phenotypes associated with cancer cells can be arrived at through the construction of increasingly complex experimental and computational models. Herein, we introduce a multiscale three-dimensional (3D) organo- and pathotypic experimental assay that approximates, to an unprecedented extent, the histopathological complexity of a tumor disseminating into its surrounding stromal milieu via both bulk and solitary motility dynamics. End point and time-lapse microscopic observations of this assay allow us to study the earliest steps of cancer invasion as well as the dynamical interactions between the epithelial and stromal compartments. We then simulate our experimental observations using the modeling environment Compucell3D that is based on the Glazier-Graner-Hogeweg model. The computational model, which comprises adhesion between cancer cells and the matrices, cell proliferation and apoptosis, and matrix remodeling through reaction-diffusion-based morphogen dynamics, is first trained to phenocopy controls run with the experimental model, wherein one or the other matrices have been removed. The trained computational model successfully predicts phenotypes of the experimental counterparts that are subjected to pharmacological treatments (inhibition of N-linked glycosylation and matrix metalloproteinase activity) and scaffold modulation (alteration of collagen density). Further parametric exploration-based simulations suggest that specific permissive regimes of cell-cell and cell-matrix adhesions, operating in the context of a reaction-diffusion-regulated ECM dynamics, promote multiscale invasion of breast cancer cells and determine the extent to which the latter migrate through their surrounding stroma.

Microenvironment-regulated lncRNA-HAL is able to promote stemness in breast cancer cells

Multicellular Tumor Spheroids culture (MCTS) is an in vitro model mimicking the characteristics of the tumor microenvironment, such as hypoxia and acidosis, resulting in the presence of both proliferating and quiescent cell populations. lncRNA's is a novel group of regulatory molecules that participates in the acquisition of tumorigenic phenotypes. In the present work we evaluated the oncogenic association of an uncharacterized lncRNA (lncRNA-HAL) in the tumorigenic phenotype induced by the MCTS microenvironment. We measured lncRNA-HAL expression level in MCF-7-MCTS populations and under different hypoxic conditions by RT-qPCR. Afterwards, we silenced lncRNA-HAL expression by shRNAs and evaluated its effect in MCF-7 transcriptome (by RNAseq) and validated the modified cellular processes by proliferation, migration, and stem cells assays. Finally, we analyzed which proteins interacts with lncRNA-HAL by ChIRP assay, to propose a possible molecular mechanism for this lncRNA. We found that lncRNA-HAL is overexpressed in the internal quiescent populations (p27 positive populations) of MCF-7-MCTS, mainly in the quiescent stem cell population, being hypoxia one of the microenvironmental cues responsible of its overexpression. Transcriptome analysis of lncRNA-HAL knockdown MCF7 cells revealed that lncRNA-HAL effect is associated with proliferation, migration and cell survival mechanisms; moreover, lncRNA-HAL silencing increased cell proliferation and impaired cancer stem cell proportion and function, resulting in decreased tumor grafting in vivo. In addition, we found that this lncRNA was overexpressed in triple-negative breast cancer patients. Analysis by ChIRP assay showed that this nuclear lncRNA binds to histones and hnRNPs suggesting a participation at the chromatin level and transcriptional regulation. The results obtained in the present work suggest that the function of lncRNA-HAL is associated with quiescent stem cell populations, which in turn is relevant due to its implications in cancer cell survival and resistance against treatment in vivo. Altogether, our data highlights a new lncRNA whose expression is regulated by the tumor microenvironment and associated to stemness in breast cancer.

MMP Secretion Rate and Inter-invadopodia Spacing Collectively Govern Cancer Invasiveness

Invadopodia are micron-sized invasive structures that mediate extracellular matrix (ECM) degradation through a combination of membrane-bound and soluble matrix metalloproteinases (MMPs). However, how such localized degradation is converted into pores big enough for cancer cells to invade, and the relative contributions of membrane-bound versus soluble MMPs to this process remain unclear. In this article, we address these questions by combining experiments and simulations. We show that in MDA-MB-231 cells, an increase in ECM density enhances invadopodia-mediated ECM degradation and decreases inter-invadopodia spacing. ECM degradation is mostly mediated by soluble MMPs, which are activated by membrane-bound MT1-MMP. We present a computational model of invadopodia-mediated ECM degradation, which recapitulates the above observations and identifies MMP secretion rate as an important regulator of invadopodia stability. Simulations with multiple invadopodia suggest that inter-invadopodia spacing and MMP secretion rate collectively dictate the size of the degraded zones. Taken together, our results suggest that for creating pores conducive for cancer invasion, cells must tune inter-invadopodia spacing and MMP secretion rate in an ECM density-dependent manner, thereby striking a balance between invadopodia penetration and ECM degradation.

Cathepsin B defines leader cells during the collective invasion of salivary adenoid cystic carcinoma

Cathepsin B (CTSB) has been reported to be involved in cancer metastasis by altering extracellular matrix (ECM) remodeling and facilitating invasion. However, the contribution of CTSB to collective cell invasion in salivary adenoid cystic carcinoma (SACC) and the underlying mechanisms remain unclear. The present study demonstrated that collective cell invasion is commonly observed in SACC without a complete epithelial-mesenchymal transition signature. CTSB was found to be overexpressed in the invasive front of SACC compared to the tumor center, and was associated with a poor prognosis of patients with SACC. Subsequently, a 3D spheroid invasion assay was established in order to recapitulate the collective cell invasion of SACC and the results revealed that CTSB was only expressed in leader cells. The knockdown of CTSB by siRNA inhibited the migration and invasion of SACC-83 cells and impaired the formation of leader cells. CTSB knockdown also disrupted cytoskeletal organization, altered cell morphology and inhibited ECM remodeling by downregulating matrix metalloproteinase-9, focal adhesion kinase and Rho/ROCK function. Therefore, the present study provides evidence that CTSB may define leader cells in SACC and is required for collective cell invasion as a potential key regulator of ECM remodeling.

Immune targets in the tumor microenvironment treated by radiotherapy

Radiotherapy (RT), the major anti-cancer modality for more than half of cancer patients after diagnosis, has the advantage of local tumor control with relatively less systematic side effects comparing to chemotherapy. However, the efficacy of RT is limited by acquired tumor resistance leading to the risks of relapse and metastasis. To further enhance the efficacy of RT, with the renaissances of targeted immunotherapy (TIT), increasing interests are raised on RT combined with TIT including cancer vaccines, T-cell therapy, and antibody-based immune checkpoint blockers (ICB) such as anti-CTLA-4 and anti-PD1/PD-L1. In achieving a significant synergy between RT and TIT, the dynamics of radiation-induced response in tumor cells and stromal cells, especially the cross-talk between tumor cells and immune cells in the irradiated tumor microenvironment (ITME) as highlighted in recent literature are to be elucidated. The abscopal effect refereeing the RT-induced priming function outside of ITME could be compromised by the immune-suppressive factors such as CD47 and PD-L1 on tumor cells and Treg induced or enhanced in the ITME. Cell surface receptors temporally or permanently induced and bioactive elements released from dead cells could serve antigenic source (radiation-associated antigenic proteins, RAAPs) to the host and have functions in immune regulation on the tumor. This review is attempted to summarize a cluster of factors that are inducible by radiation and targetable by antibodies, or have potential to be immune regulators to synergize tumor control with RT. Further characterization of immune regulators in ITME will deepen our understanding of the interplay among immune regulators in ITME and discover new effective targets for the combined modality with RT and TIT.

Adaptive F-Actin Polymerization and Localized ATP Production Drive Basement Membrane Invasion in the Absence of MMPs

Matrix metalloproteinases (MMPs) are associated with decreased patient prognosis but have failed as anti-invasive drug targets despite promoting cancer cell invasion. Through time-lapse imaging, optical highlighting, and combined genetic removal of the five MMPs expressed during anchor cell (AC) invasion in C. elegans, we find that MMPs hasten invasion by degrading basement membrane (BM). Though irregular and delayed, AC invasion persists in MMP- animals via adaptive enrichment of the Arp2/3 complex at the invasive cell membrane, which drives formation of an F-actin-rich protrusion that physically breaches and displaces BM. Using a large-scale RNAi synergistic screen and a genetically encoded ATP FRET sensor, we discover that mitochondria enrich within the protrusion and provide localized ATP that fuels F-actin network growth. Thus, without MMPs, an invasive cell can alter its BM-breaching tactics, suggesting that targeting adaptive mechanisms will be necessary to mitigate BM invasion in human pathologies.

The regulatory roles of lncRNAs in the process of breast cancer invasion and metastasis

Breast cancer (BC) is the most common cancer and principal cause of death among females worldwide. Invasion and metastasis are major causes which influence the survival and prognosis of BC. Therefore, to understand the molecule mechanism underlying invasion and metastasis is paramount for developing strategies to improve survival and prognosis in BC patients. Recent studies have reported that long non-coding RNAs (lncRNAs) play critical roles in the regulation of BC invasion and metastasis through a variety of molecule mechanisms that endow cells with an aggressive phenotype. In this article, we focused on the function of lncRNAs on BC invasion and metastasis through participating in epithelial-to-mesenchymal transition, strengthening cancer stem cells generation, serving as competing endogenous lncRNAs, influencing multiple signaling pathways as well as regulating expressions of invasion-metastasis related factors, including cells adhesion molecules, extracellular matrix, and matrix metallo-proteinases. The published work described has provided a better understanding of the mechanisms underpinning the contribution of lncRNAs to BC invasion and metastasis, which may lay the foundation for the development of new strategies to prevent BC invasion and metastasis.

From individual to collective 3D cancer dissemination: roles of collagen concentration and TGF-β

Cancer cells have the ability to migrate from the primary (original) site to other places in the body. The extracellular matrix affects cancer cell migratory capacity and has been correlated with tissue-specific spreading patterns. However, how the matrix orchestrates these behaviors remains unclear. Here, we investigated how both higher collagen concentrations and TGF-β regulate the formation of H1299 cell (a non-small cell lung cancer cell line) spheroids within 3D collagen-based matrices and promote cancer cell invasive capacity. We show that at low collagen concentrations, tumor cells move individually and have moderate invasive capacity, whereas when the collagen concentration is increased, the formation of cell clusters is promoted. In addition, when the concentration of TGF-β in the microenvironment is lower, most of the clusters are aggregates of cancer cells with a spheroid-like morphology and poor migratory capacity. In contrast, higher concentrations of TGF-β induced the formation of clusters with a notably higher invasive capacity, resulting in clear strand-like collective cell migration. Our results show that the concentration of the extracellular matrix is a key regulator of the formation of tumor clusters that affects their development and growth. In addition, chemical factors create a microenvironment that promotes the transformation of idle tumor clusters into very active, invasive tumor structures. These results collectively demonstrate the relevant regulatory role of the mechano-chemical microenvironment in leading the preferential metastasis of tumor cells to specific tissues with high collagen concentrations and TFG-β activity.

Interaction between oral squamous cell carcinoma cells and fibroblasts through TGF-β1 mediated by podoplanin

Podoplanin is upregulated in the invasive front of oral squamous cell carcinoma (OSCC). Carcinoma-associated fibroblasts (CAFs) may mediate podoplanin expression. However, the role of podoplanin in OSCC cell and fibroblast interaction remains elusive. In the present study, we found that positive podoplanin expression in OSCC cells correlated with smooth muscle actin (α-SMA) expression in CAFs. Using CAFs and normal mucosal fibroblasts (NFs), we established indirect and direct co-culture systems mimicking the structure of OSCC. Podoplanin-overexpressing OSCC cells promoted NF activation; in direct co-culture, but not in indirect co-culture, podoplanin-overexpressing OSCC cells increased fibroblast invasion via matrix metalloproteinase 2 (MMP-2), MMP-14, and αv/β6 integrin receptor (ITGA5/ITGB6) signaling. CAFs also induced podoplanin expression through the transforming growth factor-β1 (TGF-β1)/Smad pathway. TGF-β1 increased the podoplanin-dependent activation of epidermal growth factor receptor (EGFR), AKT, and extracellular signal-regulated kinase (ERK) signaling. Additionally, CAFs promoted OSCC cell invasion by upregulating MMP-2 and MMP-14 expression in both indirect and direct co-culture. Taken together, our findings indicate that podoplanin regulates the interaction between OSCC cells and CAFs via the mutual paracrine effects of TGF-β1.

Multicompartment cell-based modeling of confined migration: regulation by cell intrinsic and extrinsic factors

Though cell and nuclear deformability are expected to influence efficiency of confined migration, their individual and collective influence on migration efficiency remains incompletely understood. In addition to cell intrinsic properties, the relevance of cell extrinsic factors on confined migration, if any, has not been adequately explored. Here we address these questions using a statistical mechanics-based stochastic modeling approach where cell/nuclear dimensions and their deformability are explicitly taken into consideration. In addition to demonstrating the importance of cell softness in sustaining confined migration, our results suggest that dynamic tuning of cell and nuclear properties at different stages of migration is essential for maximizing migration efficiency. Our simulations also implicate confinement shape and confinement history as two important cell extrinsic regulators of cell invasiveness. Together, our findings illustrate the strength of a multicompartment model in dissecting the contributions of multiple factors that collectively influence confined cell migration.

Collagen type IV alpha 1 (COL4A1) and collagen type XIII alpha 1 (COL13A1) produced in cancer cells promote tumor budding at the invasion front in human urothelial carcinoma of the bladder

Current knowledge of the molecular mechanism driving tumor budding is limited. Here, we focused on elucidating the detailed mechanism underlying tumor budding in urothelial cancer of the bladder. Invasive urothelial cancer was pathologically classified into three groups as follows: nodular, trabecular, and infiltrative (tumor budding). Pathohistological analysis of the orthotopic tumor model revealed that human urothelial cancer cell lines MGH-U3, UM-UC-14, and UM-UC-3 displayed typical nodular, trabecular, and infiltrative patterns, respectively. Based on the results of comprehensive gene expression analysis using microarray (25 K Human Oligo chip), we identified two collagens, COL4A1 and COL13A1, which may contribute to the formation of the infiltrative pattern. Visualization of protein interaction networks revealed that proteins associated with connective tissue disorders, epithelial-mesenchymal transition, growth hormone, and estrogen were pivotal factors in tumor cells. To evaluate the invasion pattern of tumor cells in vitro, 3-D collective cell invasion assay using Matrigel was performed. Invadopodial formation was evaluated using Gelatin Invadopodia Assay. Knockdown of collagens with siRNA led to dramatic changes in invasion patterns and a decrease in invasion capability through decreased invadopodia. The in vivo orthotopic experimental model of bladder tumors showed that intravesical treatment with siRNA targeting COL4A1 and COL13A1 inhibited the formation of the infiltrative pattern. COL4A1 and COL13A1 production by cancer cells plays a pivotal role in tumor invasion through the induction of tumor budding. Blocking of these collagens may be an attractive therapeutic approach for treatment of human urothelial cancer of the bladder.

The Mechanics of Single Cell and Collective Migration of Tumor Cells

Metastasis is a dynamic process in which cancer cells navigate the tumor microenvironment, largely guided by external chemical and mechanical cues. Our current understanding of metastatic cell migration has relied primarily on studies of single cell migration, most of which have been performed using two-dimensional (2D) cell culture techniques and, more recently, using three-dimensional (3D) scaffolds. However, the current paradigm focused on single cell movements is shifting toward the idea that collective migration is likely one of the primary modes of migration during metastasis of many solid tumors. Not surprisingly, the mechanics of collective migration differ significantly from single cell movements. As such, techniques must be developed that enable in-depth analysis of collective migration, and those for examining single cell migration should be adopted and modified to study collective migration to allow for accurate comparison of the two. In this review, we will describe engineering approaches for studying metastatic migration, both single cell and collective, and how these approaches have yielded significant insight into the mechanics governing each process.

MMP proteolytic activity regulates cancer invasiveness by modulating integrins

Cancer invasion through dense extracellular matrices (ECMs) is mediated by matrix metalloproteinases (MMPs) which degrade the ECM thereby creating paths for migration. However, how this degradation influences the phenotype of cancer cells is not fully clear. Here we address this question by probing the function of MMPs in regulating biophysical properties of cancer cells relevant to invasion. We show that MMP catalytic activity regulates cell spreading, motility, contractility and cortical stiffness by stabilizing integrins at the membrane and activating focal adhesion kinase. Interestingly, cell rounding and cell softening on stiff gels induced by MMP inhibition is attenuated on MMP pre-conditioned surfaces. Together, our results suggest that MMP catalytic activity regulates invasiveness of cancer cells by modulating integrins.

Estrogen receptor beta as epigenetic mediator of miR-10b and miR-145 in mammary cancer

Even though the role of estrogen receptor alpha (ERα) in the modulation of breast cancer cells' behavior is thoroughly studied, the biological functions of its isoform, ERβ, are less elucidated. The suppression of ERβ in the aggressive ERα-negative MDA-MB-231 breast cancer cells resulted in the inhibition of epithelial to mesenchymal transition (EMT) and major changes in the basic functional properties and expression levels of certain matrix components of breast cancer cells. This arrest in metastatic potential of breast cancer cells suggests the contribution of ERβ in the induction of a more aggressive phenotype in MDA-MB-231 breast cancer cells. The epigenetic alterations are responsible for the ability of the tumor cells to metastasize. Here, we report for the first time that the suppression of ERβ in MDA-MB-231 breast cancer cells leads to significant changes in the expression profiles of specific microRNAs, including miR-10b, miR-200b and miR-145. Growth of MCF-7 and MDA-MB-231 cells in estrogen-free medium has a diverse impact on miRNA expression and the behavior of these cells, suggesting the specific effect of estradiol on the miRNA expression profile depending on the ER status of breast cancer cells. Enhanced miR-10b expression or silencing of miR-145 clearly revealed that these microRNAs can regulate the functional properties, EMT program and the expression of major matrix components known to be implicated in breast cancer aggressiveness. Our data revealed that miR-10b is strongly implicated in the regulation of functional properties, EMT program and Erk1/2 signaling in shERβ MDA-MB-231 cells, thus affecting the extracellular matrix (ECM) composition, including syndecan-1, proteolytic behavior, especially MMP2, MMP7 and MMP9 expression and subsequently the aggressiveness of these cells. Accordingly, the inhibition of miR-145 expression significantly increased the aggressiveness of shERβ MDA-MB-231 cells and induced EMT. Moreover, miR-145 inhibition resulted in important changes in the gene and protein levels of ECM mediators, such as HER2 and several MMPs, whereas it significantly increased the phosphorylated levels of Erk1/2 kinases in these cells, suggesting the crucial role of miR-145 in this signaling pathway. These novel results suggest that the alterations in cell behavior and in ECM composition caused by the suppression of ERβ in MDA-MB-231 cells are closely related to certain epigenetic miRNA-induced alterations. Targeting the ERβ-regulated miR-10b and miR-145 is a promising tool for diagnosis and pharmaceutical targeting in breast cancer.

Actomyosin contractility and collective migration: may the force be with you

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Collective migration relies on the ability of a multicellular co-ordinated unit to efficiently respond to physical changes in their surrounding matrix.

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Conversely, migrating cohorts physically alter their microenvironment using mechanical forces.

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During collective migration, actomyosin contractility acts as a central hub coordinating mechanosensing and mechanotransduction responses.

Collective cell migration is essential during physiological processes such as development or wound healing and in pathological conditions such as cancer dissemination. Cells migrating within multicellular tissues experiment different forces which play an intricate role during tissue formation, development and maintenance. How cells are able to respond to these forces depends largely on how they interact with the extracellular matrix. In this review, we focus on mechanics and mechanotransduction in collective migration. In particular, we discuss current knowledge on how cells integrate mechanical signals during collective migration and we highlight actomyosin contractility as a central hub coordinating mechanosensing and mechanotransduction responses.

Revisiting Seed and Soil: Examining the Primary Tumor and Cancer Cell Foraging in Metastasis

Metastasis is the consequence of a cancer cell that disperses from the primary tumor, travels throughout the body, and invades and colonizes a distant site. On the basis of Paget's 1889 hypothesis, the majority of modern metastasis research focuses on the properties of the metastatic "seed and soil," but the implications of the primary tumor "soil" have been largely neglected. The rare lethal metastatic "seed" arises as a result of the selective pressures in the primary tumor. Optimal foraging theory describes how cancer cells adopt a mobile foraging strategy to balance predation risk and resource reward. Further selection in the dispersal corridors leading out of the primary tumor enhances the adaptive profile of the potentially metastatic cell. This review focuses on the selective pressures of the primary tumor "soil" that generate lethal metastatic "seeds" which is essential to understanding this critical component of prostate cancer metastasis.Implication: Elucidating the selective pressures of the primary tumor "soil" that generate lethal metastatic "seeds" is essential to understand how and why metastasis occurs in prostate cancer. Mol Cancer Res; 15(4); 361-70. ©2017 AACR.

IGF-IR cooperates with ERα to inhibit breast cancer cell aggressiveness by regulating the expression and localisation of ECM molecules

IGF-IR is highly associated with the behaviour of breast cancer cells. In ERα-positive breast cancer, IGF-IR is present at high levels. In clinical practice, prolonged treatment with anti-estrogen agents results in resistance to the therapy with activation of alternative signaling pathways. Receptor Tyrosine Kinases, and especially IGF-IR, have crucial roles in these processes. Here, we report a nodal role of IGF-IR in the regulation of ERα-positive breast cancer cell aggressiveness and the regulation of expression levels of several extracellular matrix molecules. In particular, activation of IGF-IR, but not EGFR, in MCF-7 breast cancer cells results in the reduction of specific matrix metalloproteinases and their inhibitors. In contrast, IGF-IR inhibition leads to the depletion by endocytosis of syndecan-4. Global important changes in cell adhesion receptors, which include integrins and syndecan-4 triggered by IGF-IR inhibition, regulate adhesion and invasion. Cell function assays that were performed in MCF-7 cells as well as their ERα-suppressed counterparts indicate that ER status is a major determinant of IGF-IR regulatory role on cell adhesion and invasion. The strong inhibitory role of IGF-IR on breast cancer cells aggressiveness for which E2-ERα signaling pathway seems to be essential, highlights IGF-IR as a major molecular target for novel therapeutic strategies.

Predictive model of thrombospondin-1 and vascular endothelial growth factor in breast tumor tissue

Angiogenesis, the formation of new blood capillaries from pre-existing vessels, is a hallmark of cancer. Thus far, strategies for reducing tumor angiogenesis have focused on inhibiting pro-angiogenic factors, and less is known about the therapeutic effects of mimicking the actions of angiogenesis inhibitors. Thrombospondin-1 (TSP1) is an important endogenous inhibitor of angiogenesis that has been investigated as an anti-angiogenic agent. TSP1 impedes the growth of new blood vessels in many ways, including crosstalk with pro-angiogenic factors. Owing to the complexity of TSP1 signaling, a predictive systems biology model would provide quantitative understanding of the angiogenic balance in tumor tissue. Therefore, we have developed a molecular-detailed, mechanistic model of TSP1 and vascular endothelial growth factor (VEGF), a promoter of angiogenesis, in breast tumor tissue. The model predicts the distribution of the angiogenic factors in tumor tissue, revealing that TSP1 is primarily in an inactive, cleaved form owing to the action of proteases, rather than bound to its cellular receptors or to VEGF. The model also predicts the effects of enhancing TSP1’s interactions with its receptors and with VEGF. To provide additional predictions that can guide the development of new anti-angiogenic drugs, we simulate administration of exogenous TSP1 mimetics that bind specific targets. The model predicts that the CD47-binding TSP1 mimetic markedly decreases the ratio of receptor-bound VEGF to receptor-bound TSP1, in favor of anti-angiogenesis. Thus, we have established a model that provides a quantitative framework to study the response to TSP1 mimetics.

Plasticity of Cancer Cell Invasion-Mechanisms and Implications for Therapy

Cancer cell migration is a plastic and adaptive process integrating cytoskeletal dynamics, cell-extracellular matrix and cell-cell adhesion, as well as tissue remodeling. In response to molecular and physical microenvironmental cues during metastatic dissemination, cancer cells exploit a versatile repertoire of invasion and dissemination strategies, including collective and single-cell migration programs. This diversity generates molecular and physical heterogeneity of migration mechanisms and metastatic routes, and provides a basis for adaptation in response to microenvironmental and therapeutic challenge. We here summarize how cytoskeletal dynamics, protease systems, cell-matrix and cell-cell adhesion pathways control cancer cell invasion programs, and how reciprocal interaction of tumor cells with the microenvironment contributes to plasticity of invasion and dissemination strategies. We discuss the potential and future implications of predicted "antimigration" therapies that target cytoskeletal dynamics, adhesion, and protease systems to interfere with metastatic dissemination, and the options for integrating antimigration therapy into the spectrum of targeted molecular therapies.