Laminin and fibronectin promote the haptotactic migration of B16 mouse melanoma cells in vitro

Proteins Secreted by Lung Cancer Cells Induce the Onset of Proteinuria via Focal Adhesion Kinase Signaling in Mice

Paraneoplastic nephrotic syndrome (PNS) is a complication seen in cancer patients. Ultrastructural examination shows the accumulation of proteins and the presence of foot process (FP) effacement in the glomeruli of PNS patients. Previously, we reported that orthotopic xenografts of Lewis lung carcinoma 1 in C57BL/6 mice caused them to develop lung cancer with albuminuria. This implies that these mice can be used as a model of human disease and suggests that Lewis lung carcinoma 1 cell-secreted proteins (LCSePs) contain nephrotoxic molecules and cause inflammation in renal cells. As podocyte effacement was present in glomeruli in this model, such podocyte injury may be attributable to either soluble LCSeP or LCSeP deposits triggering pathological progression. LCSePs in conditioned media was concentrated for nephrotoxicity testing. Integrin-focal adhesion kinase (FAK) signaling and inflammatory responses were evaluated in podocytes either exposed to soluble LCSePs or seeded onto substrates with immobilized LCSePs. FAK phosphorylation and interleukin-6 expression were higher in podocytes attached to LCSePs substrates than in those exposed to soluble LCSePs. Notably, LCSeP-based haptotaxis gave rise to altered signaling in podocytes. When podocytes were stimulated by immobilized LCSePs, FAK accumulated at focal adhesions, synaptopodin dissociated from F-actin, and disrupting the interactions between synaptopodin and α-actinin was observed. When FAK was inhibited by PF-573228 in immobilized LCSePs, the association between synaptopodin and α-actinin was observed in the podocytes. The association of synaptopodin and α-actinin with F-actin allowed FP stretching, establishing a functional glomerular filtration barrier. Therefore, in this mouse model of lung cancer, FAK signaling prompts podocyte FP effacement and proteinuria, indicative of PNS.

Laminin Triggers Neutrophil Extracellular Traps (NETs) and Modulates NET Release Induced by Leishmania amazonensis

Neutrophils are recruited from the blood and transmigrate through the endothelium to reach tissues, where they are prone to respond through different mechanisms, including the release of neutrophil extracellular traps (NETs). These responses occur in close contact with proteins from the basement membrane and extracellular matrix, where laminins are abundant. Thus, we investigated the interactions between neutrophils and different laminin (LM) isoforms and analyzed the induction of NETs. We showed that neutrophils stimulated with LM isoforms 111, 211, 332, 411, 421, and 511 released NETs. The same occurred when neutrophils interacted with polymerized LMs 111, 411, and 511. LM-induced NETs were partially inhibited by pretreatment of neutrophils with an anti-α6 integrin antibody. Furthermore, NETs triggered by laminins were dependent on elastase and peptidylarginine deiminase (PAD)-4, enzymes that participate in chromatin decondensation. We also found that LMs 411 and LM 511 potentiated the NET release promoted by promastigotes of the protozoan parasite Leishmania, and that NETs stimulated by LMs alone display leishmanicidal activity. The ability of LM to induce NET release may have potential implications for the course of inflammation or infection.

Screening anti-metastasis drugs by cell adhesion-induced color change in a biochip

Metastasis is a frequent complication of cancer and accounts for more than 60% of patients' mortality. Despite technological advancements, treatment options are still limited. Ion channels participate in the regulation of cell adhesion, whilst the regulation of cell adhesion further controls metastasis formation. However, to develop a new ion channel inhibitor targeting metastasis takes tremendous effort and resources; therefore, drug repurposing is an emerging strategy in oncology. In previous studies, we have developed a metal-based nanoslit surface plasmon resonance (SPR) platform to examine the influence of drugs on the cell adhesion process. In this work, we developed a scanner-based cell adhesion kinetic examination (CAKE) system that is capable of monitoring the cell adhesion process by measuring color changes of SPR biosensors. The system's performance was demonstrated by screening the anti-metastasis ability of compounds from a commercial ion-channel inhibitor library. Out of the 274 compounds from the inhibitor library, zinc pyrithione (ZPT) and terfenadine were demonstrated to influence CL1-5 cell adhesion. The cell responses to the two compounds were then compared with those by traditional cell adhesion assays where similar behavior was observed. Further investigation of the two compounds using wound healing and transwell assays was performed and inhibitions of both cell migration and invasion by the two compounds were also observed. The results indicate that ZPT and terfenadine are potential candidates for anti-metastasis drugs. Our work has demonstrated the label-free drug screening ability of our CAKE system for finding potential drugs for cancer treatment.

Collective migration during a gap closure in a two-dimensional haptotactic model

The ability of cells to respond to substrate-bound protein gradients is crucial for many physiological processes, such as immune response, neurogenesis and cancer cell migration. However, the difficulty to produce well-controlled protein gradients has long been a limitation to our understanding of collective cell migration in response to haptotaxis. Here we use a photopatterning technique to create circular, square and linear fibronectin (FN) gradients on two-dimensional (2D) culture substrates. We observed that epithelial cells spread preferentially on zones of higher FN density, creating rounded or elongated gaps within epithelial tissues over circular or linear FN gradients, respectively. Using time-lapse experiments, we demonstrated that the gap closure mechanism in a 2D haptotaxis model requires a significant increase of the leader cell area. In addition, we found that gap closures are slower on decreasing FN densities than on homogenous FN-coated substrate and that fresh closed gaps are characterized by a lower cell density. Interestingly, our results showed that cell proliferation increases in the closed gap region after maturation to restore the cell density, but that cell–cell adhesive junctions remain weaker in scarred epithelial zones. Taken together, our findings provide a better understanding of the wound healing process over protein gradients, which are reminiscent of haptotaxis.

Basement membrane proteins modulate cell migration on bovine pericardium extracellular matrix scaffold

Native bovine pericardium (BP) exhibits anisotropy of its surface ECM niches, with the serous surface (i.e., parietal pericardium) containing basement membrane components (e.g., Laminin, Col IV) and the fibrous surface (i.e., mediastinal side) being composed primarily of type I collagen (Col I). Native BP surface ECM niche anisotropy is preserved in antigen removed BP (AR-BP) extracellular matrix (ECM) scaffolds. By exploiting sideness (serous or fibrous surface) of AR-BP scaffolds, this study aims to determine the mechanism by which ECM niche influences human mesenchymal stem cells (hMSCs) migration. Human mesenchymal stem cells (hMSC) seeding on serous surface promoted more rapid cell migration than fibrous surface seeding. Gene analysis revealed that expression of integrin α3 and α11 were increased in cells cultured on serous surface compared to those on the fibrous side. Monoclonal antibody blockade of α3β1 (i.e., laminin binding) inhibited early (i.e. ≤ 6 h) hMSC migration following serous seeding, while having no effect on migration of cells on the fibrous side. Blockade of α3β1 resulted in decreased expression of integrin α3 by cells on serous surface. Monoclonal antibody blockade of α11β1 (i.e., Col IV binding) inhibited serous side migration at later time points (i.e., 6-24 h). These results confirmed the role of integrin α3β1 binding to laminin in mediating early rapid hMSCs migration and α11β1 binding to Col IV in mediating later hMSCs migration on the serous side of AR-BP, which has critical implications for rate of cellular monolayer formation and use of AR-BP as blood contacting material for clinical applications.

Mechanical and Physical Regulation of Fibroblast-Myofibroblast Transition: From Cellular Mechanoresponse to Tissue Pathology

Fibroblasts are cells present throughout the human body that are primarily responsible for the production and maintenance of the extracellular matrix (ECM) within the tissues. They have the capability to modify the mechanical properties of the ECM within the tissue and transition into myofibroblasts, a cell type that is associated with the development of fibrotic tissue through an acute increase of cell density and protein deposition. This transition from fibroblast to myofibroblast-a well-known cellular hallmark of the pathological state of tissues-and the environmental stimuli that can induce this transition have received a lot of attention, for example in the contexts of asthma and cardiac fibrosis. Recent efforts in understanding how cells sense their physical environment at the micro- and nano-scales have ushered in a new appreciation that the substrates on which the cells adhere provide not only passive influence, but also active stimulus that can affect fibroblast activation. These studies suggest that mechanical interactions at the cell-substrate interface play a key role in regulating this phenotype transition by changing the mechanical and morphological properties of the cells. Here, we briefly summarize the reported chemical and physical cues regulating fibroblast phenotype. We then argue that a better understanding of how cells mechanically interact with the substrate (mechanosensing) and how this influences cell behaviors (mechanotransduction) using well-defined platforms that decouple the physical stimuli from the chemical ones can provide a powerful tool to control the balance between physiological tissue regeneration and pathological fibrotic response.

Feeling Things Out: Bidirectional Signaling of the Cell-ECM Interface, Implications in the Mechanobiology of Cell Spreading, Migration, Proliferation, and Differentiation

Biophysical cues stemming from the extracellular environment are rapidly transduced into discernible chemical messages (mechanotransduction) that direct cellular activities-placing the extracellular matrix (ECM) as a potent regulator of cell behavior. Dynamic reciprocity between the cell and its associated matrix is essential to the maintenance of tissue homeostasis and dysregulation of both ECM mechanical signaling, via pathological ECM turnover, and internal mechanotransduction pathways contribute to disease progression. This review covers the current understandings of the key modes of signaling used by both the cell and ECM to coregulate one another. By taking an outside-in approach, the inherent complexities and regulatory processes at each level of signaling (ECM, plasma membrane, focal adhesion, and cytoplasm) are captured to give a comprehensive picture of the internal and external mechanoregulatory environment. Specific emphasis is placed on the focal adhesion complex which acts as a central hub of mechanical signaling, regulating cell spreading, migration, proliferation, and differentiation. In addition, a wealth of available knowledge on mechanotransduction is curated to generate an integrated signaling network encompassing the central components of the focal adhesion, cytoplasm and nucleus that act in concert to promote durotaxis, proliferation, and differentiation in a stiffness-dependent manner.

From tumour perfusion to drug delivery and clinical translation of in silico cancer models

In silico cancer models have demonstrated great potential as a tool to improve drug design, optimise the delivery of drugs to target sites in the host tissue and, hence, improve therapeutic efficacy and patient outcome. However, there are significant barriers to the successful translation of in silico technology from bench to bedside. More precisely, the specification of unknown model parameters, the necessity for models to adequately reflect in vivo conditions, and the limited amount of pertinent validation data to evaluate models' accuracy and assess their reliability, pose major obstacles in the path towards their clinical translation. This review aims to capture the state-of-the-art in in silico cancer modelling of vascularised solid tumour growth, and identify the important advances and barriers to success of these models in clinical oncology. Particular emphasis has been put on continuum-based models of cancer since they - amongst the class of mechanistic spatio-temporal modelling approaches - are well-established in simulating transport phenomena and the biomechanics of tissues, and have demonstrated potential for clinical translation. Three important avenues in in silico modelling are considered in this contribution: first, since systemic therapy is a major cancer treatment approach, we start with an overview of the tumour perfusion and angiogenesis in silico models. Next, we present the state-of-the-art in silico work encompassing the delivery of chemotherapeutic agents to cancer nanomedicines through the bloodstream, and then review continuum-based modelling approaches that demonstrate great promise for successful clinical translation. We conclude with a discussion of what we view to be the key challenges and opportunities for in silico modelling in personalised and precision medicine.

Topotaxis of active Brownian particles

Recent experimental studies have demonstrated that cellular motion can be directed by topographical gradients, such as those resulting from spatial variations in the features of a micropatterned substrate. This phenomenon, known as topotaxis, has been extensively studied for topographical gradients at the subcellular scale, but can also occur in the presence of a spatially varying density of cell-sized features. Such a large-scale topotaxis has recently been observed in highly motile cells that persistently crawl within an array of obstacles with smoothly varying lattice spacing. We introduce a toy model of large-scale topotaxis, based on active Brownian particles. Using numerical simulations and analytical arguments, we demonstrate that topographical gradients introduce a spatial modulation of the particles' persistence, leading to directed motion toward regions of higher persistence. Our results demonstrate that persistent motion alone is sufficient to drive large-scale topotaxis and could serve as a starting point for more detailed studies on self-propelled particles and cells.

Lymphocyte perform reverse adhesive haptotaxis mediated by integrins LFA-1

Cell Guidance by anchored molecules, or haptotaxis, is crucial in development, immunology and cancer. Adhesive haptotaxis, or guidance by adhesion molecules, is well established for mesenchymal cells like fibroblasts, whereas its existence remains unreported for amoeboid cells that require less or no adhesion to migrate. We show here in vitro that amoeboid human T lymphocytes develop adhesive haptotaxis versus densities of integrin ligands expressed by high endothelial venules. Moreover, lymphocytes orient towards increasing adhesion with VLA-4 integrins, like all mesenchymal cells, but towards decreasing adhesion with LFA-1 integrins, which has never been observed. This counterintuitive ‘reverse haptotaxis’ cannot be explained with the existing mesenchymal mechanisms of competition between cells’ pulling edges or of lamellipodia growth activated by integrins, which favor orientation towards increasing adhesion. Mechanisms and functions of amoeboid adhesive haptotaxis remain unclear, however multidirectional integrin-mediated haptotaxis may operate around transmigration ports on endothelium, stromal cells in lymph nodes, and inflamed tissue where integrin ligands are spatially modulated.

Defining the Hallmarks of Metastasis

Metastasis is the primary cause of cancer morbidity and mortality. The process involves a complex interplay between intrinsic tumor cell properties as well as interactions between cancer cells and multiple microenvironments. The outcome is the development of a nearby or distant discontiguous secondary mass. To successfully disseminate, metastatic cells acquire properties in addition to those necessary to become neoplastic. Heterogeneity in mechanisms involved, routes of dissemination, redundancy of molecular pathways that can be utilized, and the ability to piggyback on the actions of surrounding stromal cells makes defining the hallmarks of metastasis extraordinarily challenging. Nonetheless, this review identifies four distinguishing features that are required: motility and invasion, ability to modulate the secondary site or local microenvironments, plasticity, and ability to colonize secondary tissues. By defining these first principles of metastasis, we provide the means for focusing efforts on the aspects of metastasis that will improve patient outcomes.

Topotaxis: A New Mechanism of Directed Cell Migration in Topographic ECM Gradients

Living cells orient the cytoskeleton polarity and directional migration in response to spatial gradients of multiple types of cues. The resulting tactic behaviors are critical for the proper cell localization in the context of complex single-cell and tissue behaviors. In this perspective, we highlight the recent discovery of, to our knowledge, a new -taxis phenomenon, the topotaxis, which mediates directional cell migration in response to the gradients of such topographic features as the density of extracellular matrix fibers. The direction of topotactic migration critically depends on the effective stiffness of the cortical cytoskeleton, which is controlled by the balance between two parallel signaling pathways activated by the extracellular matrix input. Topotaxis can account for such striking cell behaviors as the opposite directionality of migration of benign and metastatic cancer cells and certain aspects of the wound-healing process. We anticipate that, in conjunction with other tactic phenomena, topotaxis can provide critical information for understanding and design of tissue structure and function.

Graded Protein/PEG Nanopattern Arrays: Well-Defined Gradient Biomaterials to Induce Basic Cellular Behaviors

Gradient biomaterials have shown enormous potential in high-throughput screening of biomaterials and material-induced cell migration. To make the screening process more rapid and precise, improving the regularity of morphological structure and chemical modification on gradient biomaterials have attracted much attention. In this paper, we present a novel fabrication strategy to introduce ordered nanopattern arrays into gradient biomaterials, through combining surface-initiated atom transfer radical polymerization and inclined reactive-ion etching based on colloidal lithography. Graded protein/poly(ethylene glycol) (PEG) nanopattern arrays on a quartz substrate were fabricated and applied to affect the behaviors of cells. Owing to the continuously changed ratio of two different components, the corresponding cell adhesion density along the substrate showed obvious graded distribution after culturing for 24 h. Meanwhile, the cytoskeleton showed obvious polarization after culturing for 7 days, which is parallel with the direction of gradient. Additionally, oriented migration was generated when mouse MC3T3-E1 cells were cultured on the graded protein/PEG nanopattern arrays. On the basis of the ordered and well-defined nanopatterns, the correlation between the extracellular matrix and corresponding expressions generated by different stimuli can be investigated.

Curvotaxis directs cell migration through cell-scale curvature landscapes

Cells have evolved multiple mechanisms to apprehend and adapt finely to their environment. Here we report a new cellular ability, which we term “curvotaxis” that enables the cells to respond to cell-scale curvature variations, a ubiquitous trait of cellular biotopes. We develop ultra-smooth sinusoidal surfaces presenting modulations of curvature in all directions, and monitor cell behavior on these topographic landscapes. We show that adherent cells avoid convex regions during their migration and position themselves in concave valleys. Live imaging combined with functional analysis shows that curvotaxis relies on a dynamic interplay between the nucleus and the cytoskeleton—the nucleus acting as a mechanical sensor that leads the migrating cell toward concave curvatures. Further analyses show that substratum curvature affects focal adhesions organization and dynamics, nuclear shape, and gene expression. Altogether, this work identifies curvotaxis as a new cellular guiding mechanism and promotes cell-scale curvature as an essential physical cue.

The effect that microscale surface curvature has on cell migration has not been evaluated. Here the authors fabricate sinusoidal 3D surfaces and show that the cell nucleus and cytoskeleton cooperate to guide cells to concave valleys in a process they coin curvotaxis.

Mechanoreciprocity in cell migration

Cell migration is an adaptive process that depends on and responds to physical and molecular triggers. Moving cells sense and respond to tissue mechanics and induce transient or permanent tissue modifications, including extracellular matrix stiffening, compression and deformation, protein unfolding, proteolytic remodelling and jamming transitions. Here we discuss how the bi-directional relationship of cell-tissue interactions (mechanoreciprocity) allows cells to change position and contributes to single-cell and collective movement, structural and molecular tissue organization, and cell fate decisions.

Actomyosin contractility and RhoGTPases affect cell-polarity and directional migration during haptotaxis

Although much is known about chemotaxis- induced by gradients of soluble chemical cues - the molecular mechanisms involved in haptotaxis (migration induced by substrate-bound protein gradients) are largely unknown. We used micropatterning to produce discontinuous gradients consisting of μm-sized fibronectin-dots arranged at constant lateral but continuously decreasing axial spacing. Parameters like gradient slope, protein concentration and size or shape of the fibronectin dots were modified to determine optimal conditions for directional cell migration in gradient patterns. We demonstrate that fibroblasts predominantly migrate uphill towards a higher fibronectin density in gradients with a dot size of 2 × 2 μm, a 2% and 6% slope, and a low fibronectin concentration of 1 μg ml^-1. Increasing dot size to 3.5 × 3.5 μm resulted in stationary cells, whereas rectangular dots (2 × 3 μm) orientated perpendicular to the gradient axis preferentially induce lateral migration. During haptotaxis, the Golgi apparatus reorients to a posterior position between the nucleus and the trailing edge. Using pharmacological inhibitors, we demonstrate that actomyosin contractility and microtubule dynamics are a prerequisite for gradient recognition indicating that asymmetric intracellular forces are necessary to read the axis of adhesive gradients. In the haptotaxis signalling cascade, RhoA and Cdc42, and the atypical protein kinase C zeta (aPKCζ), but not Rac, are located upstream of actomyosin contractility.

MENA Promotes Tumor-Intrinsic Metastasis through ECM Remodeling and Haptotaxis

Oudin and colleagues report a novel and specific function of MENA in mediating directional migration of breast cancer cells toward a fibronectin gradient of increasing concentration. This MENA-mediated haptotactic response depends on the binding of MENA to the α5β1 integrin receptor, adhesion protein signaling, and fibronectin fibrillogenesis. Cancer Discov; 6(5); 474-6. ©2016 AACRSee related article by Oudin et al., p. 516.

Solution blow spinning fibres: New immunologically inert substrates for the analysis of cell adhesion and motility

The control of cell behaviour through material geometry is appealing as it avoids the requirement for complex chemical surface modifications. Significant advances in new technologies have been made to the development of polymeric biomaterials with controlled geometry and physico-chemical properties. Solution blow spinning technique has the advantage of ease of use allowing the production of nano or microfibres and the direct fibre deposition on any surface in situ. Yet, in spite of these advantages, very little is known about the influence of such fibres on biological functions such as immune response and cell migration. In this work, we engineered polymeric fibres composed of either pure poly(lactic acid) (PLA) or blends of PLA and polyethylene glycol (PEG) by solution blow spinning and determined their impact on dendritic cells, highly specialised cells essential for immunity and tolerance. We also determined the influence of fibres on cell adhesion and motility. Cells readily interacted with fibres resulting in an intimate contact characterised by accumulation of actin filaments and focal adhesion components at sites of cell-fibre interactions. Moreover, cells were guided along the fibres and actin and focal adhesion components showed a highly dynamic behaviour at cell-fibre interface. Remarkably, fibres did not elicit any substantial increase of activation markers and inflammatory cytokines in dendritic cells, which remained in their immature (inactive) state. Taken together, these findings will be useful for developing new biomaterials for applications in tissue engineering and regenerative medicine.

Inhibition of Tumor Metastasis by a Synthetic Polymer Containing a Cell-Adhesive RGDS Peptide

A water soluble polymer containing cell adhesive Arg-Gly-Asp- Ser (RGDS) sequence, i.e., poly(carboxyethylmethacrylamide-RGDS) conjugate [poly(CEMA-RGDS)], was synthesized. Poly(CEMA-RGDS) inhibited lung metastasis of B16-BL6 melanoma cells in a dose-dependent manner (20-1000 μg) and liver metastasis of L5178YML25 lymphoma cells. A mixture of poly- (CEMA) and RGDS peptide or poly(CEMA) alone did not show any inhibitory effect on lung metastasis. The Gly-Arg-Gly-Asp-Ser (GRGDS) peptide required high doses (3000 μ g) to obtain a sufficient antimetastatic effect. An in vitro study showed that poly(CEMA-RGDS) as well as RGDS + poly(CEMA) gave similar inhibition of B16-BL6 cell invasion into reconstituted basement mem brane Matrigel. Intermittent i.v. administration of poly(CEMA-RGDS) after in oculation with B16-BL6 cells caused significant inhibition of spontaneous lung metastasis as compared with the multiple administration of RGDS, poly- (CEMA) or untreated control. These results demonstrate that the conjugation

Directed migration of cancer cells guided by the graded texture of the underlying matrix

Living cells and the extracellular matrix (ECM) can exhibit complex interactions that define key developmental, physiological and pathological processes. Here, we report a new type of directed migration-which we term 'topotaxis'-guided by the gradient of the nanoscale topographic features in the cells' ECM environment. We show that the direction of topotaxis is reflective of the effective cell stiffness, and that it depends on the balance of the ECM-triggered signalling pathways PI(3)K-Akt and ROCK-MLCK. In melanoma cancer cells, this balance can be altered by different ECM inputs, pharmacological perturbations or genetic alterations, particularly a loss of PTEN in aggressive melanoma cells. We conclude that topotaxis is a product of the material properties of cells and the surrounding ECM, and propose that the invasive capacity of many cancers may depend broadly on topotactic responses, providing a potentially attractive mechanism for controlling invasive and metastatic behaviour.

Extracellular matrix-specific Caveolin-1 phosphorylation on tyrosine 14 is linked to augmented melanoma metastasis but not tumorigenesis

Caveolin-1 (CAV1) is a scaffolding protein that plays a dual role in cancer. In advanced stages of this disease, CAV1 expression in tumor cells is associated with enhanced metastatic potential, while, at earlier stages, CAV1 functions as a tumor suppressor. We recently implicated CAV1 phosphorylation on tyrosine 14 (Y14) in CAV1-enhanced cell migration. However, the contribution of this modification to the dual role of CAV1 in cancer remained unexplored. Here, we used in vitro [2D and transendothelial cell migration (TEM), invasion] and in vivo (metastasis) assays, as well as genetic and biochemical approaches to address this question in B16F10 murine melanoma cells. CAV1 promoted directional migration on fibronectin or laminin, two abundant lung extracellular matrix (ECM) components, which correlated with enhanced Y14 phosphorylation during spreading. Moreover, CAV1-driven migration, invasion, TEM and metastasis were ablated by expression of the phosphorylation null CAV1(Y14F), but not the phosphorylation mimicking CAV1(Y14E) mutation. Finally, CAV1-enhanced focal adhesion dynamics and surface expression of beta1 integrin were required for CAV1-driven TEM. Importantly, CAV1 function as a tumor suppressor in tumor formation assays was not altered by the Y14F mutation. In conclusion, our results provide critical insight to the mechanisms of CAV1 action during cancer development. Specific ECM-integrin interactions and Y14 phosphorylation are required for CAV1-enhanced melanoma cell migration, invasion and metastasis to the lung. Because Y14F mutation diminishes metastasis without inhibiting the tumor suppressor function of CAV1, Y14 phosphorylation emerges as an attractive therapeutic target to prevent metastasis without altering beneficial traits of CAV1.

Ovarian Cancer Cell Adhesion/Migration Dynamics on Micro-Structured Laminin Gradients Fabricated by Multiphoton Excited Photochemistry

Haptotaxis, i.e., cell migration in response to adhesive gradients, has been previously implicated in cancer metastasis. A better understanding of cell migration dynamics and their regulation could ultimately lead to new drug targets, especially for cancers with poor prognoses, such as ovarian cancer. Haptotaxis has not been well-studied due to the lack of biomimetic, biocompatible models, where, for example, microcontact printing and microfluidics approaches are primarily limited to 2D surfaces and cannot produce the 3D submicron features to which cells respond. Here we used multiphoton excited (MPE) phototochemistry to fabricate nano/microstructured gradients of laminin (LN) as 2.5D models of the ovarian basal lamina to study the haptotaxis dynamics of a series of ovarian cancer cells. Using these models, we found that increased LN concentration increased migration speed and also alignment of the overall cell morphology and their cytoskeleton along the linear axis of the gradients. Both these metrics were enhanced on LN compared to BSA gradients of the same design, demonstrating the importance of both topographic and ECM cues on the adhesion/migration dynamics. Using two different gradient designs, we addressed the question of the roles of local concentration and slope and found that the specific haptotactic response depends on the cell phenotype and not simply the gradient design. Moreover, small changes in concentration strongly affected the migration properties. This work is a necessary step in studying haptotaxis in more complete 3D models of the tumor microenvironment for ovarian and other cancers.

Tumor growth in complex, evolving microenvironmental geometries: a diffuse domain approach

We develop a mathematical model of tumor growth in complex, dynamic microenvironments with active, deformable membranes. Using a diffuse domain approach, the complex domain is captured implicitly using an auxiliary function and the governing equations are appropriately modified, extended and solved in a larger, regular domain. The diffuse domain method enables us to develop an efficient numerical implementation that does not depend on the space dimension or the microenvironmental geometry. We model homotypic cell-cell adhesion and heterotypic cell-basement membrane (BM) adhesion with the latter being implemented via a membrane energy that models cell-BM interactions. We incorporate simple models of elastic forces and the degradation of the BM and ECM by tumor-secreted matrix degrading enzymes. We investigate tumor progression and BM response as a function of cell-BM adhesion and the stiffness of the BM. We find tumor sizes tend to be positively correlated with cell-BM adhesion since increasing cell-BM adhesion results in thinner, more elongated tumors. Prior to invasion of the tumor into the stroma, we find a negative correlation between tumor size and BM stiffness as the elastic restoring forces tend to inhibit tumor growth. In order to model tumor invasion of the stroma, we find it necessary to downregulate cell-BM adhesiveness, which is consistent with experimental observations. A stiff BM promotes invasiveness because at early stages the opening in the BM created by MDE degradation from tumor cells tends to be narrower when the BM is stiffer. This requires invading cells to squeeze through the narrow opening and thus promotes fragmentation that then leads to enhanced growth and invasion. In three dimensions, the opening in the BM was found to increase in size even when the BM is stiff because of pressure induced by growing tumor clusters. A larger opening in the BM can increase the potential for further invasiveness by increasing the possibility that additional tumor cells could invade the stroma.

Heparan sulfate proteoglycans and heparin regulate melanoma cell functions

BACKGROUND

The solid melanoma tumor consists of transformed melanoma cells, and the associated stromal cells including fibroblasts, endothelial cells, immune cells, as well as, soluble macro- and micro-molecules of the extracellular matrix (ECM) forming the complex network of the tumor microenvironment. Heparan sulfate proteoglycans (HSPGs) are an important component of the melanoma tumor ECM. Importantly, there appears to be both a quantitative and a qualitative shift in the content of HSPGs, in parallel to the nevi-radial growth phase-vertical growth phase melanoma progression. Moreover, these changes in HSPG expression are correlated to modulations of key melanoma cell functions.

SCOPE OF REVIEW

This review will critically discuss the roles of HSPGs/heparin in melanoma development and progression.

MAJOR CONCLUSIONS

We have correlated HSPGs' expression and distribution with melanoma cell signaling and functions as well as angiogenesis.

GENERAL SIGNIFICANCE

The current knowledge of HSPGs/heparin biology in melanoma provides a foundation we can utilize in the ongoing search for new approaches in designing anti-tumor therapy. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

New tools and new biology: recent miniaturized systems for molecular and cellular biology

Recent advances in applied physics and chemistry have led to the development of novel microfluidic systems. Microfluidic systems allow minute amounts of reagents to be processed using μm-scale channels and offer several advantages over conventional analytical devices for use in biological sciences: faster, more accurate and more reproducible analytical performance, reduced cell and reagent consumption, portability, and integration of functional components in a single chip. In this review, we introduce how microfluidics has been applied to biological sciences. We first present an overview of the fabrication of microfluidic systems and describe the distinct technologies available for biological research. We then present examples of microsystems used in biological sciences, focusing on applications in molecular and cellular biology.

In vitro assays of chemotaxis as a window into mechanisms of toxicant-induced immunomodulation

Dysregulated cell movement can lead to developmental abnormalities, neoplasia, and immune system disorders, and there are a variety of contexts in which xenobiotics (and biologic) effects on this movement are of interest. Many toxins and toxicants have been shown to disrupt controlled cell movement. Identification of compounds that affect cell movement is crucial to drug discovery. Drug components may have unexpected consequences with respect to cell motility, which would exclude these compounds in drug development. Finally, the development of drugs that target chemotactic pathways may be useful in the treatment of tumors, which often reprogram chemotactic pathways to become metastatic. The effects of these agents on cell movement can be measured using several different in vitro chemotactic assays. This review details the procedures of three in vitro measurements of chemotaxis: the Boyden chamber, the under-agarose assay, and the automated, real-time, ECIS/Taxis assay, and discusses the inferences that can be drawn from the results of such studies.

Fetuin-A (α2HS-glycoprotein) is a serum chemo-attractant that also promotes invasion of tumor cells through Matrigel

The present study was conducted to determine whether fetuin-A, a dominant serum protein plays a role in chemo-attraction and chemo-invasion of carcinoma cells in vitro. Serum is normally used as positive chemotaxis control in Boyden chamber motility assays, prompting the need to identify the factor/s in serum that contributes the bulk of chemo-taxis and invasion. Serum has a plethora of chemotactic factors including stromal derived factor 1 also known as CXCL12. Using highly purified fetuin-A, we compared its chemo-attraction potential to culture medium containing 10% fetal bovine serum. We also investigated its ability to attract tumor cells through a bed of Matrigel (invasion assay). We demonstrated, using similar concentration range of fetuin-A found in blood, that it robustly supports both directed chemo-attraction and invasion of breast tumor cells. More importantly, we showed that at low concentrations (fetuin-A coated wells) itinteracts synergistically with CXCL12 to promote chemotaxis. The presence of plasminogen (PL) blunted the fetuin-A mediated chemotaxis. Taken together, the data suggest an in vivo chemotaxis/invasion role for fetuin-A.

Migration of leukocytes across the vascular intima molecules and mechanisms

The process of leukocyte emigration from the blood into a site of inflammation can be dissected into four distinct but continuous stages involving sequential interactions of different adhesion molecules on the leukocyte and endothelial surfaces. Although the molecules mediating adhesion to the luminal surface have been well studied, much less is known about the final stage of this process, transendothelial migration. This is the stage in which a leukocyte bound to the vascular wall passes between adjacent endothelial cells; it is a complex process in its own right, involving continuous structural, mechanical, and biochemical changes in both interacting cell types. Distinct cell adhesion molecule and signal transduction mechanisms that appear to be involved in this phase are discussed here.

1,3-Bis(3,5-dichlorophenyl) urea compound 'COH-SR4' inhibits proliferation and activates apoptosis in melanoma

The current clinical interventions in malignant melanomas are met with poor response to therapy due to dynamic regulation of multiple melanoma signaling pathways consequent to administration of single target agents. In this context of limited response to single target agents, novel candidate molecules capable of effectively inducing tumor inhibition along with targeting multiple critical nodes of melanoma signaling assume translational significance. In this regard, we investigated the anti-cancer effects of a novel dichlorophenyl urea compound called COH-SR4 in melanoma. The SR4 treatment decreased the survival and inhibited the clonogenic potential of melanomas along with inducing apoptosis in vitro cultures. SR4 treatments lead to inhibition of GST activity along with causing G2/M phase cell cycle arrest. Oral administration of 4 mg/kg SR4 leads to effective inhibition of tumor burdens in both syngeneic and nude mouse models of melanoma. The SR4 treatment was well tolerated and no overt toxicity was observed. The histopathological examination of resected tumor sections revealed decreased blood vessels, decrease in the levels of angiogenesis marker, CD31, and proliferation marker, Ki67, along with an increase in pAMPK levels. Western blot analyses of resected tumor lysates revealed increased PARP cleavage, Bim, pAMPK along with decreased pAkt, vimentin, fibronectin, CDK4 and cyclin B1. Thus, SR4 represents a novel candidate for the further development of mono and combinatorial therapies to effectively target aggressive and therapeutically refractory melanomas.

Cell behavior on a CCN1 functionalized elastin-mimetic protein polymer

We report the design of an elastin-mimetic triblock copolymer with the ability to guide endothelial cell adhesion, spreading, and migration while maintaining the elastomeric properties of the protein polymer. The V2 ligand sequence from matricellular protein CCN1 (cysteine-rich 61, CYR61) was multimerized and cloned into elastin polymer LysB10, creating LysB10.V2. Cell adhesion studies demonstrated that a LysB10.V2 surface density of at least 40 pmol/cm(2) was required to elicit cell attachment. Peptide blocking studies confirmed V2 specific engagement with integrin receptor α(v)β(3) (P < 0.05) and we observed the formation of actin stress fiber networks and vinculin clustering, characteristic of focal adhesion assembly. Haptotatic migration assays demonstrated the ability of LysB10.V2 surfaces to stimulate migration of endothelial cells (P < 0.05). Significantly, we illustrated the ability of LysB10.V2 to support a quiescent endothelium. The CCN1 molecule functions to support many key biological processes necessary for tissue repair and thus presents a promising target for bioengineering applications. Collectively, our results demonstrate the potential to harness CCN1 specific function in the design of new scaffold materials for applications in regenerative medicine.

Isthmin exerts pro-survival and death-promoting effect on endothelial cells through alphavbeta5 integrin depending on its physical state

Isthmin (ISM) is a 60 kDa secreted-angiogenesis inhibitor that suppresses tumor growth in mouse and disrupts vessel patterning in zebrafish embryos. It selectively binds to alphavbeta5 (αvβ5) integrin on the surface of endothelial cells (ECs), but the mechanism of its antiangiogenic action remains unknown. In this work, we establish that soluble ISM suppresses in vitro angiogenesis and induces EC apoptosis by interacting with its cell surface receptor αvβ5 integrin through a novel 'RKD' motif localized within its adhesion-associated domain in MUC4 and other proteins domain. ISM induces EC apoptosis through integrin-mediated death (IMD) by direct recruitment and activation of caspase-8 without causing anoikis. On the other hand, immobilized ISM loses its antiangiogenic function and instead promotes EC adhesion, survival and migration through αvβ5 integrin by activating focal adhesion kinase (FAK). ISM unexpectedly has both a pro-survival and death-promoting effect on ECs depending on its physical state. This dual function of a single antiangiogenic protein may impact its antiangiogenic efficacy in vivo.

Predicting and preventing melanoma invasiveness: advances in clarifying E2F1 function

Malignant melanoma of the skin is one of the most aggressive human cancers with increasing incidence, despite efforts to improve primary prevention. In particular, the prognosis of patients at late stages of the disease has not significantly improved in the last three decades, because systemic therapies have proven disappointing. Thus, metastatic melanoma continues to be a daunting clinical problem. The increasingly high rates of lethal outcome associated with advanced melanoma rely on the acquisition of invasiveness, early metastatic dissemination of tumor cells from their primary sites, and generation of chemoresistance as a consequence of alteration of key molecules involved in the regulation of cell survival. Thus far, extensive studies have been conducted to understand the molecular mechanisms that drive tumor progression, but the specific requirements underlying the aggressive behavior are still widely unknown. Understanding the determinants of this process is key to unveiling its dynamics, especially those that promote invasiveness, and may open new routes for the development of therapeutic strategies that control metastatic spread, and eventually the prevention of life-threatening metastases. Here, we review recent advances on molecular aspects, particularly of E2F1 transcription factor function, in the context of patient data, and discuss the implications for targeting melanoma cells when they begin to invade and metastasize.

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.

Structure-guided identification of a laminin binding site on the laminin receptor precursor

The 37/ 67-kDa human laminin receptor (LamR) is a cell surface receptor for laminin, prion protein, and a variety of viruses. Because of its wide range of ligands, LamR plays a role in numerous pathologies. LamR overexpression correlates with a highly invasive cell phenotype and increased metastatic ability, mediated by interactions between LamR and laminin. In addition, the specific targeting of LamR with small interfering RNAs, blocking antibodies, and Sindbis viral vectors confers anti-tumor effects. We adopted a structure-based approach to map a laminin binding site on human LamR by comparing the sequences and crystal structures of LamR and Archaeoglobus fulgidus S2p, a non-laminin-binding ortholog. Here, we identify a laminin binding site on LamR, comprising residues Phe32, Glu35, and Arg155, which are conserved among mammalian species. Mutation of these residues results in a significant loss of laminin binding. Further, recombinant wild-type LamR is able to act as a soluble decoy to inhibit cellular migration towards laminin. Mutation of this laminin binding site results in loss of migration inhibition, which demonstrates the physiological role of Phe32, Glu35, and Arg155 for laminin binding activity. Mapping of the LamR binding site should contribute to the development of therapeutics that inhibit LamR interactions with laminin and may aid in the prevention of tumor growth and metastasis.

Front instabilities and invasiveness of simulated 3D avascular tumors

We use the Glazier-Graner-Hogeweg model to simulate three-dimensional (3D), single-phenotype, avascular tumors growing in an homogeneous tissue matrix (TM) supplying a single limiting nutrient. We study the effects of two parameters on tumor morphology: a diffusion-limitation parameter defined as the ratio of the tumor-substrate consumption rate to the substrate-transport rate, and the tumor-TM surface tension. This initial model omits necrosis and oxidative/hypoxic metabolism effects, which can further influence tumor morphology, but our simplified model still shows significant parameter dependencies. The diffusion-limitation parameter determines whether the growing solid tumor develops a smooth (noninvasive) or fingered (invasive) interface, as in our earlier two-dimensional (2D) simulations. The sensitivity of 3D tumor morphology to tumor-TM surface tension increases with the size of the diffusion-limitation parameter, as in 2D. The 3D results are unexpectedly close to those in 2D. Our results therefore may justify using simpler 2D simulations of tumor growth, instead of more realistic but more computationally expensive 3D simulations. While geometrical artifacts mean that 2D sections of connected 3D tumors may be disconnected, the morphologies of 3D simulated tumors nevertheless correlate with the morphologies of their 2D sections, especially for low-surface-tension tumors, allowing the use of 2D sections to partially reconstruct medically-important 3D-tumor structures.

Inhibition of tumor growth and angiogenesis by a lysophosphatidic acid antagonist in an engineered three-dimensional lung cancer xenograft model

BACKGROUND

: We developed an engineered three-dimensional (3D) tumor xenograft model of nonsmall cell lung cancer (NSCLC) in nude mice, and we used this model to evaluate a dual-activity inhibitor of lysophosphatidic acid (LPA) biosynthesis and receptor activation.

METHODS

: First, BrP-LPA, a pan-antagonist for 4 LPA receptors and inhibitor of the lyosphospholipase D activity of autotaxin, was examined for inhibition of cell migration and cell invasion by human NSCLC A549 cells. Second, A549 cells were encapsulated in 3D in 3 semisynthetic extracellular matrices (ECMs) based on chemically modified glycosaminoglycans, and injected subcutaneously in nude mice. Tumor volume and vascularity were determined as a function of semisynthetic ECMs composition. Third, engineered NSCLC xenografts were formed from A549 cells in either Extracel-HP or Matrigel, and mice were treated with 4 intraperitoneal injections of 3 mg/kg of BrP-LPA.

RESULTS

: First, BrP-LPA inhibited cell migration and invasiveness of A549 cells in vitro. Second, tumor growth and microvessel formation for 3D encapsulated A549 cells in vivo in nude mice increased in the following order: buffer only < Extracel < Extracel-HP < Extracel-HP containing growth factorss plus laminin. Third, tumor volumes increased rapidly in both Matrigel and Extracel-HP encapsulated A549 cells, and tumor growth was markedly inhibited by BrP-LPA treatment. Finally, tumor vascularization was dramatically reduced in the A549 tumors treated with BrP-LPA.

CONCLUSIONS

: Engineered A549 lung tumors can be created by 3D encapsulation in an ECM substitute with user controlled composition. The engineered tumors regress and lose vascularity in response to a dual activity inhibitor of the LPA signaling pathway. Cancer 2010. (c) 2010 American Cancer Society.

Lack of host SPARC enhances vascular function and tumor spread in an orthotopic murine model of pancreatic carcinoma

Utilizing subcutaneous tumor models, we previously validated SPARC (secreted protein acidic and rich in cysteine) as a key component of the stromal response, where it regulated tumor size, angiogenesis and extracellular matrix deposition. In the present study, we demonstrate that pancreatic tumors grown orthotopically in Sparc-null (Sparc(-/-)) mice are more metastatic than tumors grown in wild-type (Sparc(+/+)) littermates. Tumors grown in Sparc(-/-) mice display reduced deposition of fibrillar collagens I and III, basement membrane collagen IV and the collagen-associated proteoglycan decorin. In addition, microvessel density and pericyte recruitment are reduced in tumors grown in the absence of host SPARC. However, tumors from Sparc(-/-) mice display increased permeability and perfusion, and a subsequent decrease in hypoxia. Finally, we found that tumors grown in the absence of host SPARC exhibit an increase in alternatively activated macrophages. These results suggest that increased tumor burden in the absence of host SPARC is a consequence of reduced collagen deposition, a disrupted vascular basement membrane, enhanced vascular function and an immune-tolerant, pro-metastatic microenvironment.

Front instabilities and invasiveness of simulated avascular tumors

We study the interface morphology of a 2D simulation of an avascular tumor composed of identical cells growing in an homogeneous healthy tissue matrix (TM), in order to understand the origin of the morphological changes often observed during real tumor growth. We use the Glazier-Graner-Hogeweg model, which treats tumor cells as extended, deformable objects, to study the effects of two parameters: a dimensionless diffusion-limitation parameter defined as the ratio of the tumor consumption rate to the substrate transport rate, and the tumor-TM surface tension. We model TM as a nondiffusing field, neglecting the TM pressure and haptotactic repulsion acting on a real growing tumor; thus, our model is appropriate for studying tumors with highly motile cells, e.g., gliomas. We show that the diffusion-limitation parameter determines whether the growing tumor develops a smooth (noninvasive) or fingered (invasive) interface, and that the sensitivity of tumor morphology to tumor-TM surface tension increases with the size of the dimensionless diffusion-limitation parameter. For large diffusion-limitation parameters, we find a transition (missed in previous work) between dendritic structures, produced when tumor-TM surface tension is high, and seaweed-like structures, produced when tumor-TM surface tension is low. This observation leads to a direct analogy between the mathematics and dynamics of tumors and those observed in nonbiological directional solidification. Our results are also consistent with the biological observation that hypoxia promotes invasive growth of tumor cells by inducing higher levels of receptors for scatter factors that weaken cell-cell adhesion and increase cell motility. These findings suggest that tumor morphology may have value in predicting the efficiency of antiangiogenic therapy in individual patients.

Adhesion and migration of ovarian cancer cells on crosslinked laminin fibers nanofabricated by multiphoton excited photochemistry

Ovarian cancer is the deadliest gynecological cancer, which may arise in part due to the concurrent invasion and metastasis of high grade tumors. It is thus crucial to gain insight into the adhesion and migration mechanisms in vivo, as this may ultimately lead to new treatment/detection options. To explore this possibility, we have used multiphoton excited photochemistry (MPE) to synthesize models of the ovarian basal lamina consisting of crosslinked laminin nanofibers to quantify the adhesion/migration dynamics. The nanostructured laminin patterns permit the systematic comparison of total migration, directed migration, adhesion, and morphology of "normal" immortalized human ovarian epithelial cells (IOSE) and three lines of varying metastatic potential (OVCA433, SKOV-3.ip1, and HEY-1 cells). We find that the migration of all the cell lines is directed by the crosslinked fibers, and that the contact guidance enhances the total migration rates relative to monolayers. These rates increase with increasing metastatic potential, and the more invasive cells are less rigid and more weakly adhered to the nanofibers. The extent of directed migration also depends on the cell polarity and focal adhesion expression. For the invasive cells, these findings are similar to the integrin-independent ameboid-like migration seen for polar cells in collagen gels. Collectively, the results suggest that contact mediated migration as well as decreased adhesion may be operative in metastasis of ovarian cancer in vivo.

Cellular automata as microscopic models of cell migration in heterogeneous environments

Understanding the precise interplay of moving cells with their typically heterogeneous environment is crucial for central biological processes as embryonic morphogenesis, wound healing, immune reactions or tumor growth. Mathematical models allow for the analysis of cell migration strategies involving complex feedback mechanisms between the cells and their microenvironment. Here, we introduce a cellular automaton (especially lattice-gas cellular automaton-LGCA) as a microscopic model of cell migration together with a (mathematical) tensor characterization of different biological environments. Furthermore, we show how mathematical analysis of the LGCA model can yield an estimate for the cell dispersion speed within a given environment. Novel imaging techniques like diffusion tensor imaging (DTI) may provide tensor data of biological microenvironments. As an application, we present LGCA simulations of a proliferating cell population moving in an external field defined by clinical DTI data. This system can serve as a model of in vivo glioma cell invasion.

Development and characterization of a model of liver metastasis using human colon cancer HCT-116 cells

In order to develop a model of liver metastasis of human gastrointestinal cancer cells, we examined the potential of 10 human colon and stomach cancer cell lines (HT-29, WiDr, HCT-116, HCT-15, HCC-2998, MKN7, MKN28, MKN45, MKN74 and St-4) to form liver metastases in nude mice. Among the cell lines, HCT-116 cells consistently formed gross liver metastases when injected into the spleens of nude mice. In contrast, other human colon and stomach cancer cells produced little or no liver metastasis. In order to analyze the high metastatic potential of HCT-116 cells, the adhesion potential was compared between HCT-116 cells and the other colon cancer cell lines. HCT-116 cells showed more efficient adhesion to fibronectin (FN) than other cells. Furthermore, FN enhanced haptotaxis of HCT-116 cells, but not of other colon cancer cells. The high adhesion potential to FN and enhanced haptotaxis may contribute, at least in part, to the high metastatic potential of HCT-116. To assess the value of this newly developed model of liver metastasis, we compared the ability of four anticancer drugs (fluorouracil, doxifluridine, paclitaxel and irinotecan) to inhibit the formation of liver metastases. Paclitaxel and irinotecan showed strong inhibition of liver metastasis but fluorouracil and doxifluridine showed only slight inhibition. Therefore, this model of metastasis may be useful for screening anti-liver metastatic reagents. These results indicate that the HCT-116 liver-metastasis model should be useful for analyzing the molecular mechanism of liver metastasis and for evaluating new anti-liver metastatic drugs.

Melanoma invasion - current knowledge and future directions

The acquisition of invasive behaviour is the key transition in the progression of benign melanocyte hyperplasia to life threatening melanoma. Understanding this transition and the mechanisms of invasion are the key to understanding why malignant melanoma is such a devastating disease and will aid treatment strategies. Underlying the invasive behaviour is increased cell motility caused by changes in cytoskeletal organization and altered contacts with the extra-cellular matrix (ECM). In addition, changes in the interactions of melanoma cells with keratinocytes and fibroblasts enable them to survive and proliferate outside their normal epidermal location. Proteomic and genomic initiatives are greatly increasing our knowledge of which gene products are deregulated in invasive and metastatic melanoma; however, the next challenge is to understand how these genes promote the invasion of melanoma cells. In recent years new models have been developed that more closely recapitulate the conditions of melanoma invasion in vivo. It is hoped that these models will give us a better understanding of how the genes implicated in melanoma progression affect the motility of melanoma cells and their interactions with the ECM, stromal cells and blood vessels. This review will summarise our current understanding of melanoma invasion and focus on the new model systems that can be used to study melanoma.

Differential effects of matrix and growth factors on endothelial and fibroblast motility: application of a modified cell migration assay

Cell migration is crucial in virtually every biological process and strongly depends on the nature of the surrounding matrix. An assay that enables real-time studies on the effects of defined matrix components and growth factors on cell migration is not available. We have set up a novel, quantitative migration assay, which enables unharmed cells to migrate along a defined matrix. Here, we used this so-called barrier-assay to define the contribution of fibronectin (FN) and Collagen-I (Col-I) to vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and lysophosphatidic acid (LPA)-induced cell migration of endothelial cells (EC) and fibroblasts. In EC, both FN and Col-I stimulated migration, but FN-induced motility was random, while net movement was inhibited. Addition of bFGF and VEGF overcame the effect of FN, with VEGF causing directional movement. In contrast, in 3T3 fibroblasts, FN stimulated motility and this effect was enhanced by bFGF. This motility was more efficient and morphologically completely different compared to LPA stimulation. Strikingly, directional migration of EC was not paralleled by higher amounts of stable microtubules (MT) or an increased reorientation of the microtubule-organizing centre (MTOC). For EC, the FN effect appeared concentration dependent; high FN was able to induce migration, while for fibroblasts both low and high concentrations of FN induced motility. Besides showing distinct responses of the different cells to the same factors, these results address contradictive reports on FN and show that the interplay between matrix components and growth factors determines both pattern and regulation of cell migration. J. Cell. Biochem. 99: 1536-1552, 2006. (c) 2006 Wiley-Liss, Inc.

Overexpression of laminin-5 gamma2 chain in clear cell carcinoma of the ovary

One of the characteristic microscopic features of ovarian clear cell carcinoma (CCC) is the densely hyaline basement membrane material expanding the stroma. The biological significance of this material, however, has remained unclear. Recent studies have shown that laminin-5 (LN-5), a major component of the epithelial basement membrane, plays a more active role in cell migration or tumor invasion. In the present study, 20 CCCs and 5 borderline clear cell tumors were examined for LN-5 expression immunohistochemically, using an antibody against LN-5 gamma2 chain. All of the 20 CCCs showed a focal or diffuse immunoreactivity with the LN-5 gamma2 chain in the tumor stroma; whereas, borderline clear cell tumors rarely showed a stromal immunoreactivity. Cytoplasmic accumulation of the LN-5 gamma2 chain was far less common than stromal accumulation, suggesting an accelerated secretion in CCC. In vitro, CCC cell lines showed a significant increase in cell migration over excessive LN-5, and the migration was blocked by an antibody against integrin alpha3. These results indicate that an interaction between CCC cells and extracellularly accumulated LN-5 is responsible for cell migration and the subsequent stromal invasion of CCC.