Myosin phosphorylation on stress fibers predicts contact guidance behavior across diverse breast cancer cells

Contact Guidance Drives Upward Cellular Migration at the Mesoscopic Scale

Introduction

Cancer metastasis is associated with increased cancer incidence, recurrence, and mortality. The role of cell contact guidance behaviors in cancer metastasis has been recognized but has not been elucidated yet.

Methods

The contact guidance behavior of cancer cells in response to topographical constraints is identified using microgrooved substrates with varying dimensions at the mesoscopic scale. Then, the cell morphology is determined to quantitatively analyze the effects of substrate dimensions on cells contact guidance. Cell density and migrate velocity signatures within the cellular population are determined using time-lapse phase-contrast microscopy. The effect of soluble factors concentration is determined by culturing cells upside down. Then, the effect of cell-substrate interaction on cell migration is investigated using traction force microscopy.

Results

With increasing depth and decreasing groove width, cell elongation and alignment are enhanced, while cell spreading is inhibited. Moreover, cells display preferential distribution on the ridges, which is found to be more pronounced with increasing depth and groove width. Determinations of cell density and migration velocity signatures reveal that the preferential distribution on ridges is caused by cell upward migration. Combined with traction force measurement, we find that migration toward ridges is governed by different cell-substrate interactions between grooves and ridges caused by geometrical constraints. Interestingly, the upward migration of cells at the mesoscopic scale is driven by entropic maximization.

Conclusions

The mesoscopic cell contact guidance mechanism based on the entropic force driven theory provides basic support for the study of cell alignment and migration along healthy tissues with varying size, thereby aiding in the prediction of cancer metastasis.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-023-00766-y.

Soft topographical patterns trigger a stiffness-dependent cellular response to contact guidance

Topographical patterns are a powerful tool to study directional migration. Grooved substrates have been extensively used as in vitro models of aligned extracellular matrix fibers because they induce cell elongation, alignment, and migration through a phenomenon known as contact guidance. This process, which involves the orientation of focal adhesions, F-actin, and microtubule cytoskeleton along the direction of the grooves, has been primarily studied on hard materials of non-physiological stiffness. But how it unfolds when the stiffness of the grooves varies within the physiological range is less known. Here we show that substrate stiffness modulates the cellular response to topographical contact guidance. We find that for fibroblasts, while focal adhesions and actin respond to topography independently of the stiffness, microtubules show a stiffness-dependent response that regulates contact guidance. On the other hand, both clusters and single breast carcinoma epithelial cells display stiffness-dependent contact guidance, leading to more directional and efficient migration when increasing substrate stiffness. These results suggest that both matrix stiffening and alignment of extracellular matrix fibers cooperate during directional cell migration, and that the outcome differs between cell types depending on how they organize their cytoskeletons.

Biophysical cues of in vitro biomaterials-based artificial extracellular matrix guide cancer cell plasticity

Clinical evidence supports a role for the extracellular matrix (ECM) in cancer plasticity across multiple tumor types. The lack of in vitro models that represent the native ECMs is a significant challenge for cancer research and drug discovery. Therefore, a major motivation for developing new tumor models is to create the artificial ECM in vitro. Engineered biomaterials can closely mimic the architectural and mechanical properties of ECM to investigate their specific effects on cancer progression, offering an alternative to animal models for the testing of cancer cell behaviors. In this review, we focused on the biomaterials from different sources applied in the fabrication of the artificial ECM and their biophysical cues to recapitulate key features of tumor niche. Furthermore, we summarized how the distinct biophysical cues guided cell behaviors of cancer plasticity, including morphology, epithelial-to-mesenchymal transition (EMT), enrichment of cancer stem cells (CSCs), proliferation, migration/invasion and drug resistance. We also discuss the future opportunities in using the artificial ECM for applications of tumorigenesis research and precision medicine, as well as provide useful messages of principles for designing suitable biomaterial scaffolds.

Stromal architecture directs early dissemination in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is an extremely metastatic and lethal disease. Here, in both murine and human PDA, we demonstrate that extracellular matrix architecture regulates cell extrusion and subsequent invasion from intact ductal structures through tumor-associated collagen signatures (TACS). This results in early dissemination from histologically premalignant lesions and continual invasion from well-differentiated disease, and it suggests TACS as a biomarker to aid in the pathologic assessment of early disease. Furthermore, we show that pancreatitis results in invasion-conducive architectures, thus priming the stroma prior to malignant disease. Analysis in potentially novel microfluidic-derived microtissues and in vivo demonstrates decreased extrusion and invasion following focal adhesion kinase (FAK) inhibition, consistent with decreased metastasis. Thus, data suggest that targeting FAK or strategies to reengineer and normalize tumor microenvironments may have roles not only in very early disease, but also for limiting continued dissemination from unresectable disease. Likewise, it may be beneficial to employ stroma-targeting strategies to resolve precursor diseases such as pancreatitis in order to remove stromal architectures that increase risk for early dissemination.

Aligned forces: Origins and mechanisms of cancer dissemination guided by extracellular matrix architecture

Organized extracellular matrix (ECM), in the form of aligned architectures, is a critical mediator of directed cancer cell migration by contact guidance, leading to metastasis in solid tumors. Current models suggest anisotropic force generation through the engagement of key adhesion and cytoskeletal complexes drives contact-guided migration. Likewise, disrupting the balance between cell-cell and cell-ECM forces, driven by ECM engagement for cells at the tumor-stromal interface, initiates and drives local invasion. Furthermore, processes such as traction forces exerted by cancer and stromal cells, spontaneous reorientation of matrix-producing fibroblasts, and direct binding of ECM modifying proteins lead to the emergence of collagen alignment in tumors. Thus, as we obtain a deeper understanding of the origins of ECM alignment and the mechanisms by which it is maintained to direct invasion, we are poised to use the new paradigm of stroma-targeted therapies to disrupt this vital axis of disease progression in solid tumors.

Cancer cell migration in collagen-hyaluronan composite extracellular matrices

Hyaluronan (HA) is a key component in the tumor microenvironment (TME) that participates in cancer growth and invasiveness. While the molecular weight (MW) dependent properties of HA can cause tumor-promoting and -repressing effects, the elevated levels of HA in the TME impedes drug delivery. The degradation of HA using hyaluronidases (HYALs), resulting in fragments of HA, is a way to overcome this, but the consequences of changes in HA molecular weight and concentration is currently unknown. Therefore, it is critical to understand the MW-dependent biological effects of HA. Here we examine the influence of HA molecular weight on biophysical properties that regulate cell migration and extracellular matrix (ECM) remodeling. In our study, we used vLMW, LMW and HMW HA at different physiologically relevant concentrations, with a particular interest in correlating the mechanical and structural properties to different cell functions. The elastic modulus, collagen network pore size and collagen fiber diameter increased with increasing HA concentration. Although the collagen network pore size increased, these pores were filled with the bulky HA molecules. Consequently, cell migration decreased with increase in HA concentration due to multiple, long-lived and unproductive protrusions, suggesting the influence of steric factors. Surprisingly, even though elastic modulus increased with HA molecular weight and concentration, gel compaction assays showed an increased degree of ECM compaction among HMW HA gels at high concentrations (2 and 4 mg mL^-1 [0.2 and 0.4%]). These results were not seen in collagen gels that lacked HA, but had similar stiffness. HA appears to have the effect of decreasing migration and increasing collagen network contraction, but only at high HA molecular weight. Consequently, changes in HA molecular weight can have relatively large effects on cancer cell behavior. STATEMENT OF SIGNIFICANCE: Hyaluronan (HA) is a critical component of the tumor microenvironment (TME). Overproduction of HA in the TME results in poor prognosis and collapse of blood vessels, inhibiting drug delivery. Hyaluronidases have been used to enhance drug delivery. However, they lead to low molecular weight (MW) HA, altering the mechanical and structural properties of the TME and cancer cell behavior. Understanding how HA degradation affects cancer cell behavior is critical for uncovering detrimental effects of this therapy. Very little is known about how HA MW affects cancer cell behavior in tumor-mimicking collagen-HA composite networks. Here we examine how MW and HA content in collagen-HA networks alter structural and mechanical properties to regulate cell migration and matrix remodeling in 3D TME-mimicking environments.

Targeting cytoskeletal phosphorylation in cancer

Phosphorylation of cytoskeletal proteins regulates the dynamics of polymerization, stability, and disassembly of the different types of cytoskeletal polymers. These control the ability of cells to migrate and divide. Mutations and alterations of the expression levels of multiple protein kinases are hallmarks of most forms of cancer. Thus, altered phosphorylation of cytoskeletal proteins is observed in most cancer cells. These alterations potentially control the ability of cancer cells to divide, invade and form distal metastasis. This review highlights the emergent role of phosphorylation in the control of the function of the different cytoskeletal polymers in cancer cells. It also addresses the potential effect of targeted inhibitors in the normalization of cytoskeletal function.

Anisotropic stiffness gradient-regulated mechanical guidance drives directional migration of cancer cells

Interfacial interactions between cancer cells and surrounding microenvironment involve complex mechanotransduction mechanisms that are directly associated with tumor invasion and metastasis. Matrix remodeling triggers heterogeneity of stiffness in tumor microenvironment and thus generates anisotropic stiffness gradient (ASG). The migration of cancer cells mediated by ASG, however, still remains elusive. Based on a multi-layer polymerization method of microstructured hydrogels with surface topology, we develop an in vitro experimental platform for mechanical interactions of cancer cells with ASG matrix microenvironment. We show that mechanical guidance of mesenchymal cells is essentially modulated by ASG, leading to a spontaneous directional migration along the orientation parallel to the maximum stiffness although there is no stiffness gradient in the direction. The ASG-regulated mechanical guidance presents an alternative way of cancer cell directional migration. Further, our findings indicate that the mechanical guidance occurs only in mesenchymal cancer cells, but not in epithelial cancer cells, implying that cell contractility may contribute to ASG-regulated migration of cells. This work is not only helpful for elucidating the role of matrix remodeling in mediating tumor cell invasion and metastasis, but has potential implications for developing specific cancer treatments. STATEMENT OF SIGNIFICANCE: Local extracellular matrix (ECM) stiffening triggers mechanical heterogeneity in tumor microenvironment, which can exert a crucial impact on interfacial interactions between tumor cells and surrounding ECM. The underlying mechanobiological mechanism that tumor cells are modulated by mechanically heterogeneous ECM, however, still remains mysterious to a great extent. Through our established in vitro platform and analysis, we have demonstrated that anisotropic stiffness gradient (ASG) has the ability to elicit directional migration of cells, essentially depending on local stiffness gradients and the corresponding absolute stiffness values. This study is not only crucial for revealing the role of matrix remodeling in regulating tumor invasion and metastasis, but also offers a valuable guidance for developing anti-tumor therapies from the biomechanical perspective.

ECM Remodeling in Breast Cancer with Different Grade: Contribution of 2D-DIGE Proteomics

Tumor extracellular matrix (ECM) plays a pivotal role in outcome of breast cancer (BC) patients. Overexpression of 58 genes, encoding 43 structural ECM proteins, has been identified to determine a specific cluster of BC with accelerated metastatic potential only in the undifferentiated (grade III) phenotype. The scope of this study is to characterize protein repertoire able to predict patient outcome in BC according to ECM gene expression pattern and histological grade. The differential proteomic analysis is based on 2D-differential gel electrophoresis, MALDI-MS, bioinformatics, and immunoblotting. Results suggest a relationship among ECM remodeling, signal mechanotransduction, and metabolic rewiring in BCs characterized by a specific mRNA ECM signature and identified a set of dysregulated proteins characteristic of hormone receptors expression as fibrinogen-β chain, collagen α-1(VI) chain, and α-1B-glycoprotein. Furthermore, in triple negative tumors with ECM signature, the FGG and α5β1/αvβ3 integrins increase whereas detyrosinated α-tubulin and mimecan decrease leading to unorganized integrin presentation involving focal adhesion kinase, activation of Rho GTPases associated to epithelial mesenchymal transition. In hormone receptors negative BCs characterized by a specific ECM gene cluster, the differentially regulated proteins, identified in the present study, can be potentially relevant to predict patient's outcome.

Entropic Forces Drive Cellular Contact Guidance

Contact guidance-the widely known phenomenon of cell alignment induced by anisotropic environmental features-is an essential step in the organization of adherent cells, but the mechanisms by which cells achieve this orientational ordering remain unclear. Here, we seeded myofibroblasts on substrates micropatterned with stripes of fibronectin and observed that contact guidance emerges at stripe widths much greater than the cell size. To understand the origins of this surprising observation, we combined morphometric analysis of cells and their subcellular components with a, to our knowledge, novel statistical framework for modeling nonthermal fluctuations of living cells. This modeling framework is shown to predict not only the trends but also the statistical variability of a wide range of biological observables, including cell (and nucleus) shapes, sizes, and orientations, as well as stress-fiber arrangements within the cells with remarkable fidelity with a single set of cell parameters. By comparing observations and theory, we identified two regimes of contact guidance: 1) guidance on stripe widths smaller than the cell size (w ≤ 160 μm), which is accompanied by biochemical changes within the cells, including increasing stress-fiber polarization and cell elongation; and 2) entropic guidance on larger stripe widths, which is governed by fluctuations in the cell morphology. Overall, our findings suggest an entropy-mediated mechanism for contact guidance associated with the tendency of cells to maximize their morphological entropy through shape fluctuations.

Degradation and Remodeling of Epitaxially Grown Collagen Fibrils

INTRODUCTION—

The extracellular matrix (ECM) in the tumor microenvironment contains high densities of collagen that are highly aligned, resulting in directional migration called contact guidance that facilitates efficient migration out of the tumor. Cancer cells can remodel the ECM through traction force controlled by myosin contractility or proteolytic activity controlled by matrix metalloproteinase (MMP) activity, leading to either enhanced or diminished contact guidance.

METHODS—

Recently, we have leveraged the ability of mica to epitaxially grow aligned collagen fibrils in order to assess contact guidance. In this article, we probe the mechanisms of remodeling of aligned collagen fibrils on mica by breast cancer cells.

RESULTS—

We show that cells that contact guide with high fidelity (MDA-MB-231 cells) exert more force on the underlying collagen fibrils than do cells that contact guide with low fidelity (MTLn3 cells). These high traction cells (MDA-MB-231 cells) remodel collagen fibrils over hours, pulling so hard that the collagen fibrils detach from the surface, effectively delaminating the entire contact guidance cue. Myosin or MMP inhibition decreases this effect. Interestingly, blocking MMP appears to increase the alignment of cells on these substrates, potentially allowing the alignment through myosin contractility to be uninhibited. Finally, amplification or dampening of contact guidance with respect to a particular collagen fibril organization is seen under different conditions.

CONCLUSIONS—

Both myosin II contractility and MMP activity allow MDA-MB-231 cells to remodel and eventually destroy epitaxially grown aligned collagen fibrils.

Bimodal sensing of guidance cues in mechanically distinct microenvironments

Contact guidance due to extracellular matrix architecture is a key regulator of carcinoma invasion and metastasis, yet our understanding of how cells sense guidance cues is limited. Here, using a platform with variable stiffness that facilitates uniaxial or biaxial matrix cues, or competing E-cadherin adhesions, we demonstrate distinct mechanoresponsive behavior. Through disruption of traction forces, we observe a profound phenotypic shift towards a mode of dendritic protrusion and identify bimodal processes that govern guidance sensing. In contractile cells, guidance sensing is strongly dependent on formins and FAK signaling and can be perturbed by disrupting microtubule dynamics, while low traction conditions initiate fluidic-like dendritic protrusions that are dependent on Arp2/3. Concomitant disruption of these bimodal mechanisms completely abrogates the contact guidance response. Thus, guidance sensing in carcinoma cells depends on both environment architecture and mechanical properties and targeting the bimodal responses may provide a rational strategy for disrupting metastatic behavior.

Invasive cells respond to contact guidance cues during migration. Here, using micro- and nanopatterning with different ligands and varying stiffness, the authors find that cells can make cellular protrusions through both contractility-dependent and contractility-independent means.

Transfer of assembled collagen fibrils to flexible substrates for mechanically tunable contact guidance cues

Contact guidance or bidirectional migration along aligned fibers modulates many physiological and pathological processes such as wound healing and cancer invasion. Aligned 2D collagen fibrils epitaxially grown on mica substrates replicate many features of contact guidance seen in aligned 3D collagen fiber networks. However, these 2D collagen self-assembled substrates are difficult to image through, do not have known or tunable mechanical properties and cells degrade and mechanically detach collagen fibrils from the surface, leading to an inability to assess contact guidance over long times. Here, we describe the transfer of aligned collagen fibrils from mica substrates to three different functionalized target substrates: glass, polydimethylsiloxane (PDMS) and polyacrylamide (PA). Aligned collagen fibrils can be efficiently transferred to all three substrates. This transfer resulted in substrates that were to varying degrees resistant to cell-mediated collagen fibril deformation that resulted in detachment of the collagen fibril field, allowing for contact guidance to be observed over longer time periods. On these transferred substrates, cell speed is lowest on softer contact guidance cues for both MDA-MB-231 and MTLn3 cells. Intermediate stiffness resulted in the fastest migration. MTLn3 cell directionality was low on soft contact guidance cues, whereas MDA-MB-231 cell directionality marginally increased. It appears that the stiffness of the contact guidance cue regulates contact guidance differently between cell types. The development of this collagen fibril transfer method allows for the attachment of aligned collagen fibrils on substrates, particularly flexible substrates, that do not normally promote aligned collagen fibril growth, increasing the utility of this collagen self-assembly system for the fundamental examination of mechanical regulation of contact guidance.

Contact guidance diversity in rotationally aligned collagen matrices

Cancer cell metastasis is responsible for approximately 90% of deaths related to cancer. The migration of cancer cells away from the primary tumor and into healthy tissue is driven in part by contact guidance, or directed migration in response to aligned extracellular matrix. While contact guidance has been a focus of many studies, much of this research has explored environments that present 2D contact guidance structures. Contact guidance environments in 3D more closely resemble in vivo conditions and model cell-ECM interactions better than 2D environments. While most cells engage in directed migration on potent 2D contact guidance cues, there is diversity in response to contact guidance cues based on whether the cell migrates with a mesenchymal or amoeboid migration mode. In this paper, rotational alignment of collagen gels was used to study the differences in contact guidance between MDA-MB-231 (mesenchymal) and MTLn3 (amoeboid) cells. MDA-MB-231 cells migrate with high directional fidelity in aligned collagen gels, while MTLn3 cells show no directional migration. The collagen stiffness was increased through glycation, resulting in decreased MDA-MB-231 directionality in aligned collagen gels. Interestingly, partial inhibition of cell contractility dramatically decreased directionality in MDA-MB-231 cells. The directionality of MDA-MB-231 cells was most sensitive to ROCK inhibition, but unlike in 2D contact guidance environments, cell directionality and speed are more tightly coupled. Modulation of the contractile apparatus appears to more potently affect contact guidance than modulation of extracellular mechanical properties of the contact guidance cue.

STATEMENT OF SIGNIFICANCE

Collagen fiber alignment in the tumor microenvironment directs migration, a process called contact guidance, enhancing the efficiency of cancer invasion and metastasis. 3D systems that assess contact guidance by locally orienting collagen fiber alignment are lacking. Furthermore, cell type differences and the role of extracellular matrix stiffness in tuning contact guidance fidelity are not well characterized. In this paper rotational alignment of collagen fibers is used as a 3D contact guidance cue to illuminate cell type differences and the role of extracellular matrix stiffness in guiding cell migration along aligned fibers of collagen. This local alignment offers a simple approach by which to couple collagen alignment with gradients in other directional cues in devices such as microfluidic chambers.

Contact guidance persists under myosin inhibition due to the local alignment of adhesions and individual protrusions

Contact guidance—cell polarization by anisotropic substrate features—is integral to numerous physiological processes; however the complexities of its regulation are only beginning to be discovered. In particular, cells polarize to anisotropic features under non-muscle myosin II (MII) inhibition, despite MII ordinarily being essential for polarized cell migration. Here, we investigate the ability of cells to sense and respond to fiber alignment in the absence of MII activity. We find that contact guidance is determined at the level of individual protrusions, which are individually guided by local fiber orientation, independent of MII. Protrusion stability and persistence are functions of adhesion lifetime, which depends on fiber orientation. Under MII inhibition, adhesion lifetime no longer depends on fiber orientation; however the ability of protrusions to form closely spaced adhesions sequentially without having to skip over gaps in adhesive area, biases protrusion formation along fibers. The co-alignment of multiple protrusions polarizes the entire cell; if the fibers are not aligned, contact guidance of individual protrusions still occurs, but does not produce overall cell polarization. These results describe how aligned features polarize a cell independently of MII and demonstrate how cellular contact guidance is built on the local alignment of adhesions and individual protrusions.