Compensation mechanism in tumor cell migration: mesenchymal-amoeboid transition after blocking of pericellular proteolysis

Physical network regimes of 3D fibrillar collagen networks trigger invasive phenotypes of breast cancer cells

The mechanical characteristics of the extracellular environment are known to significantly influence cancer cell behavior in vivo and in vitro. The structural complexity and viscoelastic dynamics of the extracellular matrix (ECM) pose significant challenges in understanding its impact on cancer cells. Herein, we report distinct regulatory signatures in the invasion of different breast cancer cell lines into three-dimensional (3D) fibrillar collagen networks, caused by systematic modifications of the physical network properties. By reconstituting collagen networks of thin fibrils, we demonstrate that such networks can display network strand flexibility akin to that of synthetic polymer networks, known to exhibit entropic rubber elasticity. This finding contrasts with the predominant description of the mechanics of fibrillar collagen networks by an enthalpic bending elasticity of rod-like fibrils. Mean-squared displacement analysis of free-standing fibrils confirmed a flexible fiber regime in networks of thin fibrils. Furthermore, collagen fibrils in both networks were softened by the adsorption of highly negatively charged sulfonated polymers and colloidal probe force measurements of network elastic modulus again proofed the occurrence of the two different physical network regimes. Our cell assays revealed that the cellular behavior (morphology, clustering, invasiveness, matrix metalloproteinase (MMP) activity) of the 'weakly invasive' MCF-7 and 'highly invasive' MDA-MB-231 breast cancer cell lines is distinctively affected by the physical (enthalpic/entropic) network regime, and cannot be explained by changes of the network elastic modulus, alone. These results highlight an essential pathway, albeit frequently overlooked, how the physical characteristics of fibrillar ECMs affect cellular behavior. Considering the coexistence of diverse physical network regimes of the ECM in vivo, our findings underscore their critical role of ECM's physical network regimes in tumor progression and other cell functions, and moreover emphasize the significance of 3D in vitro collagen network models for quantifying cell responses in both healthy and pathological states.

Decoding physical principles of cell migration under controlled environment using microfluidics

Living cells can perform incredible tasks that man-made micro/nano-sized robots have not yet been able to accomplish. One example is that white blood cells can sense and move to the site of pathogen attack within minutes. The robustness and precision of cellular functions have been perfected through billions of years of evolution. In this context, we ask the question whether cells follow a set of physical principles to sense, adapt, and migrate. Microfluidics has emerged as an enabling technology for recreating well-defined cellular environment for cell migration studies, and its ability to follow single cell dynamics allows for the results to be amenable for theoretical modeling. In this review, we focus on the development of microfluidic platforms for recreating cellular biophysical (e.g., mechanical stress) and biochemical (e.g., nutrients and cytokines) environments for cell migration studies in 3D. We summarize the basic principles that cells (including bacteria, algal, and mammalian cells) use to respond to chemical gradients learned from microfluidic systems. We also discuss about novel biological insights gained from studies of cell migration under biophysical cues and the need for further quantitative studies of cell function under well-controlled biophysical environments in the future.

Biophysical modeling identifies an optimal hybrid amoeboid-mesenchymal phenotype for maximal T cell migration speeds

Despite recent experimental progress in characterizing cell migration mechanics, our understanding of the mechanisms governing rapid cell movement remains limited. To effectively limit tumor growth, antitumoral T cells need to rapidly migrate to find and kill cancer cells. To investigate the upper limits of cell speed, we developed a new hybrid stochastic-mean field model of bleb-based cell motility. We first examined the potential for adhesion-free bleb-based migration and show that cells migrate inefficiently in the absence of adhesion-based forces, i.e., cell swimming. While no cortical contractility oscillations are needed for cells to swim in viscoelastic media, high-to-low cortical contractility oscillations are necessary for cell swimming in viscous media. This involves a high cortical contractility phase with multiple bleb nucleation events, followed by an intracellular pressure buildup recovery phase at low cortical tensions, resulting in modest net cell motion. However, our model suggests that cells can employ a hybrid bleb- and adhesion-based migration mechanism for rapid cell motility and identifies conditions for optimality. The model provides a momentum-conserving mechanism underlying rapid single-cell migration and identifies factors as design criteria for engineering T cell therapies to improve movement in mechanically complex environments.

Single Living Cell "Observation-Analysis" Integrated Platform Decodes Cell Migration Plasticity Orchestrated by Nucleocytoplasmic STAT3

Cell migration requires the interplay among diverse migration patterns. The molecular basis of distinct migration programs is undoubtedly vital but not fully explored. Meanwhile, the lack of tools for investigating spontaneous migratory plasticity in a single living cell also adds to the hindrance. Here, we developed a micro/nanotechnology-enabled single-cell analytical platform to achieve coherent monitoring of spontaneous migratory pattern and signaling molecules. Via the platform, we unveiled a previously unappreciated STAT3 regionalization on the multifunctional regulations of migration. Specifically, nuclear STAT3 is associated with amoeboid migration, while cytoplasmic STAT3 promotes mesenchymal movement. Opposing effects of JAK2 multisite phosphorylation shape its response to STAT3 distribution in a dynamic and antagonistic manner, eventually triggering a reversible amoeboid-mesenchymal transition. Based on the above results, bioinformatics further revealed a possible downstream regulator of nucleocytoplasmic STAT3. Thus, our platform, as an exciting technological advance in single-cell migration research, can provide in-depth mechanism interpretations of tumor metastasis and progression.

Fluorescent, phosphorescent, magnetic resonance contrast and radioactive tracer labelling of extracellular vesicles

This review focusses on the significance of fluorescent, phosphorescent labelling and tracking of extracellular vesicles (EVs) for unravelling their biology, pathophysiology, and potential diagnostic and therapeutic uses. Various labeling strategies, such as lipid membrane, surface protein, luminal, nucleic acid, radionuclide, quantum dot labels, and metal complex-based stains, are evaluated for visualizing and characterizing EVs. Direct labelling with fluorescent lipophilic dyes is simple but generally lacks specificity, while surface protein labelling offers selectivity but may affect EV-cell interactions. Luminal and nucleic acid labelling strategies have their own advantages and challenges. Each labelling approach has strengths and weaknesses, which require a suitable probe and technique based on research goals, but new tetranuclear polypyridylruthenium(II) complexes as phosphorescent probes have strong phosphorescence, selective staining, and stability. Future research should prioritize the design of novel fluorescent probes and labelling platforms that can significantly enhance the efficiency, accuracy, and specificity of EV labeling, while preserving their composition and functionality. It is crucial to reduce false positive signals and explore the potential of multimodal imaging techniques to gain comprehensive insights into EVs.

Rear cortex contraction aids in nuclear transit during confined migration by increasing pressure in the cell posterior

As cells migrate through biological tissues, they must frequently squeeze through micron-sized constrictions in the form of interstitial pores between extracellular matrix fibers and/or other cells. Although it is now well recognized that such confined migration is limited by the nucleus, which is the largest and stiffest organelle, it remains incompletely understood how cells apply sufficient force to move their nucleus through small constrictions. Here, we report a mechanism by which contraction of the cell rear cortex pushes the nucleus forward to mediate nuclear transit through constrictions. Laser ablation of the rear cortex reveals that pushing forces behind the nucleus are the result of increased intracellular pressure in the rear compartment of the cell. The pushing forces behind the nucleus depend on accumulation of actomyosin in the rear cortex and require Rho kinase (ROCK) activity. Collectively, our results suggest a mechanism by which cells generate elevated intracellular pressure in the posterior compartment to facilitate nuclear transit through three-dimensional (3D) constrictions. This mechanism might supplement or even substitute for other mechanisms supporting nuclear transit, ensuring robust cell migrations in confined 3D environments.

Combined effects of matrix stiffness and obesity-associated signaling directs progressive phenotype in PANC-1 pancreatic cancer cells in vitro

Obesity is a leading risk factor of pancreatic ductal adenocarcinoma (PDAC) that contributes to poor disease prognosis and outcomes. Retrospective studies have identified this link, but interactions surrounding obesity and PDAC are still unclear. Research has shifted to contributions of fibrosis (desmoplasia) on malignancy, which involves increased deposition of collagens and other extracellular matrix (ECM) molecules and increased ECM crosslinking, all of which contribute to increased tissue stiffening. However, fibrotic stiffening is underrepresented as a model feature in current PDAC models. Fibrosis is shared between PDAC and obesity, and can be leveraged for in vitro model design, as current animal obesity models of PDAC are limited in their ability to isolate individual components of fibrosis to study cell behavior. In the current study, methacrylated type I collagen (PhotoCol®) was photo-crosslinked to pathological stiffness levels to recapitulate fibrotic ECM stiffening. PANC-1 cells were encapsulated within PhotoCol®, and the tumor-tissue constructs were prepared to represent normal (healthy) (~600 Pa) and pathological (~2000 Pa) tissues. Separately, human mesenchymal stem cells were differentiated into adipocytes representing lean (2D differentiation) and obese fat tissue (3D collagen matrix differentiation), and conditioned media was applied to PANC-1 tumor-tissue constructs. Conditioned media from obese adipocytes showed increased vimentin expression, a hallmark of invasiveness and progression, that was not seen after exposure to media from lean adipocytes or control media. Characterization of the obese adipocyte secretome suggested that some PANC-1 differences may arise from increased interleukin-8 and -10 compared to lean adipocytes. Additionally, high matrix stiffness associated induced an amoeboid morphology in PANC-1 cells that was not present at low stiffness. Amoeboid morphology is an accessory to epithelial-to-mesenchymal transition and is used to navigate complex ECM environments. This plasticity has greater implications for treatment efficacy of metastatic cancers. Overall, this work 1) highlights the importance of investigating PDAC-obesity interactions to study the effects on disease progression and persistence, 2) establishes PhotoCol® as a matrix material that can be leveraged to study amoeboid morphology and invasion in PDAC, and 3) emphasizes the importance of integrating both biophysical and biochemical interactions associated within both pathologies for in vitro PDAC models.

Proteolysis-free amoeboid migration of melanoma cells through crowded environments via bleb-driven worrying

In crowded microenvironments, migrating cells must find or make a path. Amoeboid cells are thought to find a path by deforming their bodies to squeeze through tight spaces. Yet, some amoeboid cells seem to maintain a near-spherical morphology as they move. To examine how they do so, we visualized amoeboid human melanoma cells in dense environments and found that they carve tunnels via bleb-driven degradation of extracellular matrix components without the need for proteolytic degradation. Interactions between adhesions and collagen at the cell front induce a signaling cascade that promotes bleb enlargement via branched actin polymerization. Large blebs abrade collagen, creating feedback between extracellular matrix structure, cell morphology, and polarization that enables both path generation and persistent movement.

Environmentally dependent and independent control of 3D cell shape

How cancer cells determine their shape in response to three-dimensional (3D) geometric and mechanical cues is unclear. We develop an approach to quantify the 3D cell shape of over 60,000 melanoma cells in collagen hydrogels using high-throughput stage-scanning oblique plane microscopy (ssOPM). We identify stereotypic and environmentally dependent changes in shape and protrusivity depending on whether a cell is proximal to a flat and rigid surface or is embedded in a soft environment. Environmental sensitivity metrics calculated for small molecules and gene knockdowns identify interactions between the environment and cellular factors that are important for morphogenesis. We show that the Rho guanine nucleotide exchange factor (RhoGEF) TIAM2 contributes to shape determination in environmentally independent ways but that non-muscle myosin II, microtubules, and the RhoGEF FARP1 regulate shape in ways dependent on the microenvironment. Thus, changes in cancer cell shape in response to 3D geometric and mechanical cues are modulated in both an environmentally dependent and independent fashion.

Nucleating amoeboid cancer cell motility with Diaphanous related formins

The tissue invasive capacity of cancer cells is determined by their phenotypic plasticity. For instance, mesenchymal to amoeboid transition has been found to facilitate the passage of cancer cells through confined environments. This phenotypic transition is also heavily regulated by the architecture of the actin cytoskeleton, which may increase myosin contractility and the intracellular pressure that is known to drive bleb formation. In this review, we highlight several Diaphanous related formins (DRFs) that have been found to promote or suppress bleb formation in cancer cells, which is a hallmark of amoeboid migration. Based on the work discussed here, the role of the DRFs in cancer(s) is worthy of further scrutiny in animal models, as they may prove to be therapeutic targets.

Exploring the Enigma: The Role of the Epithelial Protein Lost in Neoplasm in Normal Physiology and Cancer Pathogenesis

The cytoskeleton plays a pivotal role in maintaining the epithelial phenotype and is vital to several hallmark processes of cancer. Over the past decades, researchers have identified the epithelial protein lost in neoplasm (EPLIN, also known as LIMA1) as a key regulator of cytoskeletal dynamics, cytoskeletal organization, motility, as well as cell growth and metabolism. Dysregulation of EPLIN is implicated in various aspects of cancer progression, such as tumor growth, invasion, metastasis, and therapeutic resistance. Its altered expression levels or activity can disrupt cytoskeletal dynamics, leading to aberrant cell motility and invasiveness characteristic of malignant cells. Moreover, the involvement of EPLIN in cell growth and metabolism underscores its significance in orchestrating key processes essential for cancer cell survival and proliferation. This review provides a comprehensive exploration of the intricate roles of EPLIN across diverse cellular processes in both normal physiology and cancer pathogenesis. Additionally, this review discusses the possibility of EPLIN as a potential target for anticancer therapy in future studies.

Matrix Resistance Toward Proteolytic Cleavage Controls Contractility-Dependent Migration Modes During Angiogenic Sprouting

Tissue homeostasis and disease states rely on the formation of new blood vessels through angiogenic sprouting, which is tightly regulated by the properties of the surrounding extracellular matrix. While physical cues, such as matrix stiffness or degradability, have evolved as major regulators of cell function in tissue microenvironments, it remains unknown whether and how physical cues regulate endothelial cell migration during angiogenesis. To investigate this, a biomimetic model of angiogenic sprouting inside a tunable synthetic hydrogel is created. It is shown that endothelial cells sense the resistance of the surrounding matrix toward proteolytic cleavage and respond by adjusting their migration phenotype. The resistance cells encounter is impacted by the number of covalent matrix crosslinks, crosslink degradability, and the proteolytic activity of cells. When matrix resistance is high, cells switch from a collective to an actomyosin contractility-dependent single cellular migration mode. This switch in collectivity is accompanied by a major reorganization of the actin cytoskeleton, where stress fibers are no longer visible, and F-actin aggregates in large punctate clusters. Matrix resistance is identified as a previously unknown regulator of angiogenic sprouting and, thus, provides a mechanism by which the physical properties of the matrix impact cell migration modes through cytoskeletal remodeling.

Cell volume expansion and local contractility drive collective invasion of the basement membrane in breast cancer

Breast cancer becomes invasive when carcinoma cells invade through the basement membrane (BM)-a nanoporous layer of matrix that physically separates the primary tumour from the stroma. Single cells can invade through nanoporous three-dimensional matrices due to protease-mediated degradation or force-mediated widening of pores via invadopodial protrusions. However, how multiple cells collectively invade through the physiological BM, as they do during breast cancer progression, remains unclear. Here we developed a three-dimensional in vitro model of collective invasion of the BM during breast cancer. We show that cells utilize both proteases and forces-but not invadopodia-to breach the BM. Forces are generated from a combination of global cell volume expansion, which stretches the BM, and local contractile forces that act in the plane of the BM to breach it, allowing invasion. These results uncover a mechanism by which cells collectively interact to overcome a critical barrier to metastasis.

CTC-Race: Single-Cell Motility Assay of Circulating Tumor Cells from Metastatic Lung Cancer Patients

Distinctive subpopulations of circulating tumor cells (CTCs) with increased motility are considered to possess enhanced tumor-initiating potential and contribute to metastasis. Single-cell analysis of the migratory CTCs may increase our understanding of the metastatic process, yet most studies are limited by technical challenges associated with the isolation and characterization of these cells due to their extreme scarcity and heterogeneity. We report a microfluidic method based on CTCs' chemotactic motility, termed as CTC-Race assay, that can analyze migrating CTCs from metastatic non-small-cell lung cancer (NSCLC) patients with advanced tumor stages and enable concurrent biophysical and biochemical characterization of them with single-cell resolution. Analyses of motile CTCs in the CTC-Race assay, in synergy with other single cell characterization techniques, could provide insights into cancer metastasis.

Diffuse midline glioma invasion and metastasis rely on cell-autonomous signaling

BACKGROUND

Diffuse midline gliomas (DMG) are pediatric tumors with negligible 2-year survival after diagnosis characterized by their ability to infiltrate the central nervous system. In the hope of controlling the local growth and slowing the disease, all patients receive radiotherapy. However, distant progression occurs frequently in DMG patients. Current clues as to what causes tumor infiltration circle mainly around the tumor microenvironment, but there are currently no known determinants to predict the degree of invasiveness.

METHODS

In this study, we use patient-derived glioma stem cells (GSCs) to create patient-specific 3D avatars to model interindividual invasion and elucidate the cellular supporting mechanisms.

RESULTS

We show that GSC models in 3D mirror the invasive behavior of the parental tumors, thus proving the ability of DMG to infiltrate as an autonomous characteristic of tumor cells. Furthermore, we distinguished 2 modes of migration, mesenchymal and ameboid-like, and associated the ameboid-like modality with GSCs derived from the most invasive tumors. Using transcriptomics of both organoids and primary tumors, we further characterized the invasive ameboid-like tumors as oligodendrocyte progenitor-like, with highly contractile cytoskeleton and reduced adhesion ability driven by crucial over-expression of bone morphogenetic pathway 7 (BMP7). Finally, we deciphered MEK, ERK, and Rho/ROCK kinases activated downstream of the BMP7 stimulation as actionable targets controlling tumor cell motility.

CONCLUSIONS

Our findings identify 2 new therapeutic avenues. First, patient-derived GSCs represent a predictive tool for patient stratification in order to adapt irradiation strategies. Second, autocrine and short-range BMP7-related signaling becomes a druggable target to prevent DMG spread and metastasis.

High Stretch Associated with Mechanical Ventilation Promotes Piezo1-Mediated Migration of Airway Smooth Muscle Cells

Ventilator-induced lung injury (VILI) during mechanical ventilation (MV) has been attributed to airway remodeling involving increased airway smooth muscle cells (ASMCs), but the underlying mechanism is not fully understood. Thus, we aimed to investigate whether MV-associated high stretch (>10% strain) could modulate mechanosensitive Piezo1 expression and thereby alter cell migration of ASMCs as a potential pathway to increased ASMCs in VILI. C57BL/6 mice and ASMCs were subjected to MV at high tidal volume (VT, 18 mL/kg, 3 h) and high stretch (13% strain, 0.5 Hz, 72 h), respectively. Subsequently, the mice or cells were evaluated for Piezo1 and integrin mRNA expression by immunohistochemical staining and quantitative PCR (qPCR), and cell migration and adhesion by transwell and cell adhesion assays. Cells were either treated or not with Piezo1 siRNA, Piezo1-eGFP, Piezo1 knockin, Y27632, or blebbistatin to regulate Piezo1 mRNA expression or inhibit Rho-associated kinase (ROCK) signaling prior to migration or adhesion assessment. We found that expression of Piezo1 in in situ lung tissue, mRNA expression of Piezo1 and integrin αVβ1 and cell adhesion of ASMCs isolated from mice with MV were all reduced but the cell migration of primary ASMCs (pASMCs) isolated from mice with MV was greatly enhanced. Similarly, cell line mouse ASMCs (mASMCs) cultured in vitro with high stretch showed that mRNA expression of Piezo1 and integrin αVβ1 and cell adhesion were all reduced but cell migration was greatly enhanced. Interestingly, such effects of MV or high stretch on ASMCs could be either induced or abolished/reversed by down/up-regulation of Piezo1 mRNA expression and inhibition of ROCK signaling. High stretch associated with MV appears to be a mechanical modulator of Piezo1 mRNA expression and can, thus, promote cell migration of ASMCs during therapeutic MV. This may be a novel mechanism of detrimental airway remodeling associated with MV, and, therefore, a potential intervention target to treat VILI.

RhoA activation promotes glucose uptake to elevate proliferation in MAPK inhibitor resistant melanoma cells

Cutaneous melanomas harboring a B-RafV600E mutation are treated with immune check point inhibitors or kinase inhibitor combination therapies relying on MAPK inhibitors (MAPKi) Dabrafenib and Trametinib (Curti and Faries, 2021). However, cells become resistant to treatments over the timespan of a few months. Resistance to MAPKi has been associated with adoption of an aggressive amoeboid phenotype characterized by elevated RhoA signaling, enhanced contractility and thick cortical filamentous actin (F-actin) structures (Kim et al., 2016; Misek et al., 2020). Targeting active RhoA through Rho-kinase (ROCK) inhibitors, either alone or in combination with immunotherapies, reverts MAPKi-resistance (Misek et al., 2020; Orgaz et al., 2020). Yet, the mechanisms for this behavior remain largely unknown. Given our recent findings of cytoskeleton's role in cancer cell proliferation (Mohan et al., 2019), survival (Weems et al., 2023), and metabolism (Park et al., 2020), we explored possibilities by which RhoA-driven changes in cytoskeleton structure may confer resistance. We confirmed elevated activation of RhoA in a panel of MAPKi-resistant melanoma cell lines, leading to a marked increase in the presence of contractile F-actin bundles. Moreover, these cells had increased glucose uptake and glycolysis, a phenotype disrupted by pharmacological perturbation of ROCK. However, glycolysis was unaffected by disruption of F-actin bundles, indicating that glycolytic stimulation in MAPKi-resistant melanoma is independent of F-actin organization. Instead, our findings highlight a mechanism in which elevated RhoA signaling activates ROCK, leading to the activation of insulin receptor substrate 1 (IRS1) and P85 of the PI3K pathway, which promotes cell surface expression of GLUT1 and elevated glucose uptake. Application of ROCK inhibitor GSK269962A results in reduced glucose uptake and glycolysis, thus impeding cell proliferation. Our study adds a mechanism to the proposed use of ROCK inhibitors for long-term treatments on MAPKi-resistant melanomas.

Plasma Membrane Blebbing Is Controlled by Subcellular Distribution of Vimentin Intermediate Filaments

The formation of specific cellular protrusions, plasma membrane blebs, underlies the amoeboid mode of cell motility, which is characteristic for free-living amoebae and leukocytes, and can also be adopted by stem and tumor cells to bypass unfavorable migration conditions and thus facilitate their long-distance migration. Not all cells are equally prone to bleb formation. We have previously shown that membrane blebbing can be experimentally induced in a subset of HT1080 fibrosarcoma cells, whereas other cells in the same culture under the same conditions retain non-blebbing mesenchymal morphology. Here we show that this heterogeneity is associated with the distribution of vimentin intermediate filaments (VIFs). Using different approaches to alter the VIF organization, we show that blebbing activity is biased toward cell edges lacking abundant VIFs, whereas the VIF-rich regions of the cell periphery exhibit low blebbing activity. This pattern is observed both in interphase fibroblasts, with and without experimentally induced blebbing, and during mitosis-associated blebbing. Moreover, the downregulation of vimentin expression or displacement of VIFs away from the cell periphery promotes blebbing even in cells resistant to bleb-inducing treatments. Thus, we reveal a new important function of VIFs in cell physiology that involves the regulation of non-apoptotic blebbing essential for amoeboid cell migration and mitosis.

Fibrin Stiffness Regulates Phenotypic Plasticity of Metastatic Breast Cancer Cells

The extracellular matrix (ECM)-regulated phenotypic plasticity is crucial for metastatic progression of triple negative breast cancer (TNBC). While ECM faithful cell-based models are available for in situ and invasive tumors, such as cell aggregate cultures in reconstituted basement membrane and in collagenous gels, there are no ECM faithful models for metastatic circulating tumor cells (CTCs). Such models are essential to represent the stage of metastasis where clinical relevance and therapeutic opportunities are significant. Here, CTC-like DU4475 TNBC cells are cultured in mechanically tunable 3D fibrin hydrogels. This is motivated, as in circulation fibrin aids CTC survival by forming a protective coating reducing shear stress and immune cell-mediated cytotoxicity and promotes several stages of late metastatic processes at the interface between circulation and tissue. This work shows that fibrin hydrogels support DU4475 cell growth, resulting in spheroid formation. Furthermore, increasing fibrin stiffness from 57 to 175 Pa leads to highly motile, actin and tubulin containing cellular protrusions, which are associated with specific cell morphology and gene expression patterns that markedly differ from basement membrane or suspension cultures. Thus, mechanically tunable fibrin gels reveal specific matrix-based regulation of TNBC cell phenotype and offer scaffolds for CTC-like cells with better mechano-biological properties than liquid.

Mechanobiology in oncology: basic concepts and clinical prospects

The interplay between genetic transformations, biochemical communications, and physical interactions is crucial in cancer progression. Metastasis, a leading cause of cancer-related deaths, involves a series of steps, including invasion, intravasation, circulation survival, and extravasation. Mechanical alterations, such as changes in stiffness and morphology, play a significant role in all stages of cancer initiation and dissemination. Accordingly, a better understanding of cancer mechanobiology can help in the development of novel therapeutic strategies. Targeting the physical properties of tumours and their microenvironment presents opportunities for intervention. Advancements in imaging techniques and lab-on-a-chip systems enable personalized investigations of tumor biomechanics and drug screening. Investigation of the interplay between genetic, biochemical, and mechanical factors, which is of crucial importance in cancer progression, offers insights for personalized medicine and innovative treatment strategies.

Zhuidu Formula suppresses the migratory and invasive properties of triple-negative breast cancer cells via dual signaling pathways of RhoA/ROCK and CDC42/MRCK

ETHNOPHARMACOLOGICAL RELEVANCE

Zhuidu Formula (ZDF) is composed of triptolide, cinobufagin and paclitaxel, which are the active ingredients of Tripterygium wilfordii Hook. F, dried toad skin and Taxus wallichiana var. chinensis (Pilg) Florin, respectively. Modern pharmacological studies show that triptolide, cinobufagin, and paclitaxel are well-known natural compounds that exert anti-tumor effects by interfering with DNA synthesis, inducing tumor cell apoptosis, and inhibiting the dynamic balance of the tubulin. However, the mechanism by which the three compounds inhibit triple-negative breast cancer (TNBC) metastasis is unknown.

OBJECTIVE

The objective of this investigation was to examine the inhibitory essences of ZDF on the metastasis of TNBC and elucidate its potential mechanism.

MATERIALS AND METHODS

Cell viability of triptolide (TPL), cinobufagin (CBF), and paclitaxel (PTX) on MDA-MB-231 cells was assessed employing a CCK-8 assay. The drug interactions of the three drugs on MDA-MB-231 cells were determined in vitro utilizing the Chou-Talalay method. MDA-MB-231 cells were identified for migration, invasion and adhesion in vitro through the implementation of the scratch assay, transwell assay and adhesion assay, respectively. The formation of cytoskeleton protein F-actin was detected by immunofluorescence assay. The expressions of MMP-2 and MMP-9 in the supernatant of the cells were determined by ELISA analysis. The Western blot and RT-qPCR were employed to explore the protein expressions associated with the dual signaling pathways of RhoA/ROCK and CDC42/MRCK. The anti-tumor efficacy of ZDF in vivo and its preliminary mechanism were investigated in the mouse 4T1 TNBC model.

RESULTS

The results demonstrated that ZDF could significantly reduce the viability of the MDA-MB-231 cell, and the combination index (CI) values of actual compatibility experimental points were all less than 1, demonstrating a favorable synergistic compatibility relationship. It was found that ZDF reduces RhoA/ROCK and CDC42/MRCK dual signaling pathways, which are responsible for MDA-MB-231cell migration, invasion, and adhesion. Additionally, there has been a significant reduction in the manifestation of cytoskeleton-related proteins. Furthermore, the expression levels of RhoA, CDC42, ROCK2, and MRCKβ mRNA and protein were down-regulated. ZDF significantly decreased the protein expressions of vimentin, cytokeratin-8, Arp2 and N-WASP, and inhibited actin polymerization and actomyosin contraction. Furthermore, MMP-2 and MMP-9 levels in the high-dose ZDF group were decreased by 30% and 26%, respectively. ZDF significantly reduced the tumor volume and protein expressions of ROCK2 and MRCKβ in tumor tissues without eliciting any perceptible alterations in the physical mass of the mice, and the reduction was more pronounced than that of the BDP5290 treated group.

CONCLUSION

The current investigation demonstrates that ZDF exhibits a proficient inhibitory impact on TNBC metastasis by regulating cytoskeletal proteins through the dual signaling pathways of RhoA/ROCK and CDC42/MRCK. Furthermore, the findings indicate that ZDF has significant anti-tumorigenic and anti-metastatic characteristics in breast cancer animal models.

Extracellular matrix type 0: From ancient collagen lineage to a versatile product pipeline - JellaGel™

Extracellular matrix type 0 is reported. The matrix is developed from a jellyfish collagen predating mammalian forms by over 0.5 billion years. With its ancient lineage, compositional simplicity, and resemblance to multiple collagen types, the matrix is referred to as the extracellular matrix type 0. Here we validate the matrix describing its physicochemical and biological properties and present it as a versatile, minimalist biomaterial underpinning a pipeline of commercialised products under the collective name of JellaGelTM. We describe an extensive body of evidence for folding and assembly of the matrix in comparison to mammalian matrices, such as bovine collagen, and its use to support cell growth and development in comparison to known tissue-derived products, such as Matrigel™. We apply the matrix to co-culture human astrocytes and cortical neurons derived from induced pluripotent stem cells and visualise neuron firing synchronicity with correlations indicative of a homogenous extracellular material in contrast to the performance of heterogenous commercial matrices. We prove the ability of the matrix to induce spheroid formation and support the 3D culture of human immortalised, primary, and mesenchymal stem cells. We conclude that the matrix offers an optimal solution for systemic evaluations of cell-matrix biology. It effectively combines the exploitable properties of mammalian tissue extracts or top-down matrices, such as biocompatibility, with the advantages of synthetic or bottom-up matrices, such as compositional control, while avoiding the drawbacks of the two types, such as biological and design heterogeneity, thereby providing a unique bridging capability of a stem extracellular matrix.

Impact of elastic substrate on the dynamic heterogeneity of WC256 Walker carcinosarcoma cells

Cellular heterogeneity is a phenomenon in which cell populations are composed of subpopulations that vary in their behavior. Heterogeneity is particularly pronounced in cancer cells and can affect the efficacy of oncological therapies. Previous studies have considered heterogeneity dynamics to be indicative of evolutionary changes within subpopulations; however, these studies do not consider the short-time morphological plasticity of cells. Physical properties of the microenvironment elasticity have also been poorly investigated within the context of cellular heterogeneity, despite its role in determining cellular behavior. This article demonstrates that cellular heterogeneity can be highly dynamic and dependent on the micromechanical properties of the substrate. During observation, migrating Walker carcinosarcoma WC256 cells were observed to belong to different subpopulations, in which their morphologies and migration strategies differed. Furthermore, the application of an elastic substrate (E = 40 kPa) modified three aspects of cellular heterogeneity: the occurrence of subpopulations, the occurrence of transitions between subpopulations, and cellular migration and morphology. These findings provide a new perspective in the analysis of cellular heterogeneity, whereby it may not be a static feature of cancer cell populations, instead varying over time. This helps further the understanding of cancer cell behavior, including their phenotype and migration strategy, which may help to improve cancer therapies by extending their suitability to investigate tumor heterogeneity.

Adhesion tunes speed and persistence by coordinating protrusions and extracellular matrix remodeling

Cell migration through 3D environments is essential to development, disease, and regeneration processes. Conceptual models of migration have been developed primarily on the basis of 2D cell behaviors, but a general understanding of 3D cell migration is still lacking due to the added complexity of the extracellular matrix. Here, using a multiplexed biophysical imaging approach for single-cell analysis of human cell lines, we show how the subprocesses of adhesion, contractility, actin cytoskeletal dynamics, and matrix remodeling integrate to produce heterogeneous migration behaviors. This single-cell analysis identifies three modes of cell speed and persistence coupling, driven by distinct modes of coordination between matrix remodeling and protrusive activity. The framework that emerges establishes a predictive model linking cell trajectories to distinct subprocess coordination states.

Peristalsis-Associated Mechanotransduction Drives Malignant Progression of Colorectal Cancer

Introduction

In the colorectal cancer (CRC) tumor microenvironment, cancerous and precancerous cells continuously experience mechanical forces associated with peristalsis. Given that mechanical forces like shear stress and strain can positively impact cancer progression, we explored the hypothesis that peristalsis may also contribute to malignant progression in CRC. We defined malignant progression as enrichment of cancer stem cells and the acquisition of invasive behaviors, both vital to CRC progression.

Methods

We leveraged our peristalsis bioreactor to expose CRC cell lines (HCT116), patient-derived xenograft (PDX1,2) lines, or non-cancerous intestinal cells (HIEC-6) to forces associated with peristalsis in vitro. Cells were maintained in static control conditions or exposed to peristalsis for 24 h prior to assessment of cancer stem cell (CSC) emergence or the acquisition of invasive phenotypes.

Results

Exposure of HCT116 cells to peristalsis significantly increased the emergence of LGR5+ CSCs by 1.8-fold compared to static controls. Peristalsis enriched LGR5 positivity in several CRC cell lines, notably significant in KRAS mutant lines. In contrast, peristalsis failed to increase LGR5+ in non-cancerous intestinal cells, HIEC-6. LGR5+ emergence downstream of peristalsis was dependent on ROCK and Wnt activity, and not YAP1 activation. Additionally, HCT116 cells adopted invasive morphologies when exposed to peristalsis, with increased filopodia density and epithelial to mesenchymal gene expression, in a Wnt dependent manner.

Conclusions

Peristalsis associated forces drive malignant progression of CRC via ROCK, YAP1, and Wnt-related mechanotransduction.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-023-00776-w.

Vaccinia virus induces EMT-like transformation and RhoA-mediated mesenchymal migration

The emerging outbreak of monkeypox is closely associated with the viral infection and spreading, threatening global public health. Virus-induced cell migration facilitates viral transmission. However, the mechanism underlying this type of cell migration remains unclear. Here we investigate the motility of cells infected by vaccinia virus (VACV), a close relative of monkeypox, through combining multi-omics analyses and high-resolution live-cell imaging. We find that, upon VACV infection, the epithelial cells undergo epithelial-mesenchymal transition-like transformation, during which they lose intercellular junctions and acquire the migratory capacity to promote viral spreading. After transformation, VACV-hijacked RhoA signaling significantly alters cellular morphology and rearranges the actin cytoskeleton involving the depolymerization of robust actin stress fibers, leading-edge protrusion formation, and the rear-edge recontraction, which coordinates VACV-induced cell migration. Our study reveals how poxviruses alter the epithelial phenotype and regulate RhoA signaling to induce fast migration, providing a unique perspective to understand the pathogenesis of poxviruses.

Characterization of Anticancer Effects of the Analogs of DJ4, a Novel Selective Inhibitor of ROCK and MRCK Kinases

The Rho associated coiled-coil containing protein kinase (ROCK1 and ROCK2) and myotonic dystrophy-related Cdc-42 binding kinases (MRCKα and MRCKβ) are critical regulators of cell proliferation and cell plasticity, a process intimately involved in cancer cell migration and invasion. Previously, we reported the discovery of a novel small molecule (DJ4) selective multi-kinase inhibitor of ROCK1/2 and MRCKα/β. Herein, we further characterized the anti-proliferative and apoptotic effects of DJ4 in non-small cell lung cancer and triple-negative breast cancer cells. To further optimize the ROCK/MRCK inhibitory potency of DJ4, we generated a library of 27 analogs. Among the various structural modifications, we identified four additional active analogs with enhanced ROCK/MRCK inhibitory potency. The anti-proliferative and cell cycle inhibitory effects of the active analogs were examined in non-small cell lung cancer, breast cancer, and melanoma cell lines. The anti-proliferative effectiveness of DJ4 and the active analogs was further demonstrated against a wide array of cancer cell types using the NCI-60 human cancer cell line panel. Lastly, these new analogs were tested for anti-migratory effects in highly invasive MDA-MB-231 breast cancer cells. Together, our results demonstrate that selective inhibitors of ROCK1/2 (DJE4, DJ-Allyl) inhibited cell proliferation and induced cell cycle arrest at G2/M but were less effective in cell death induction compared with dual ROCK1/2 and MRCKα/β (DJ4 and DJ110).

A review of the mechanisms of anti-cancer activities of some medicinal plants-biochemical perspectives

Cancer is a disease resulting in unbridled growth of cells due to dysregulation in the balance of cell populations. Various management procedures in handling cases of cancer are not without their adverse side effects on the normal cells. Medicinal plants/herbs have been in use in the management of various ailments, including cancer, for a long time. Medicinal plants have been credited with wide safety margins, cost effectiveness, availability and diverse activities. This study reviewed various mechanisms of anti-cancer activities of some medicinal plants from a biochemical perspective. The mechanisms of anti-cancer activities of plant compounds addressed in this article include induction of apoptosis, anti-angiogenic effects, anti-metastasis, inhibition of cell cycle, inhibition of DNA destruction and effects on key enzymes, cytotoxic and anti-oxidant effects. The anti-cancer activities of some of the plants involve more than one mechanism.

Fiber density and matrix stiffness modulate distinct cell migration modes in a 3D stroma mimetic composite hydrogel

The peritumoral stroma is a complex 3D tissue that provides cells with myriad biophysical and biochemical cues. Histologic observations suggest that during metastatic spread of carcinomas, these cues influence transformed epithelial cells, prompting a diversity of migration modes spanning single cell and multicellular phenotypes. Purported consequences of these variations in tumor escape strategies include differential metastatic capability and therapy resistance. Therefore, understanding how cues from the peritumoral stromal microenvironment regulate migration mode has both prognostic and therapeutic value. Here, we utilize a synthetic stromal mimetic in which matrix fiber density and bulk hydrogel mechanics can be orthogonally tuned to investigate the contribution of these two key matrix attributes on MCF10A migration mode phenotypes, epithelial-mesenchymal transition (EMT), and invasive potential. We develop an automated computational image analysis framework to extract migratory phenotypes from fluorescent images and determine 3D migration metrics relevant to metastatic spread. Using this analysis, we find that matrix fiber density and bulk hydrogel mechanics distinctly contribute to a variety of MCF10A migration modes including amoeboid, single mesenchymal, clusters, and strands. We identify combinations of physical and soluble cues that induce a variety of migration modes originating from the same MCF10A spheroid and use these settings to examine a functional consequence of migration mode -resistance to apoptosis. We find that cells migrating as strands are more resistant to staurosporine-induced apoptosis than either disconnected clusters or individual invading cells. Improved models of the peritumoral stromal microenvironment and understanding of the relationships between matrix attributes and cell migration mode can aid ongoing efforts to identify effective cancer therapeutics that address cell plasticity-based therapy resistances. STATEMENT OF SIGNIFICANCE: Stromal extracellular matrix structure dictates both cell homeostasis and activation towards migratory phenotypes. However decoupling the effects of myriad biophysical cues has been difficult to achieve. Here, we encapsulate electrospun fiber segments within an amorphous hydrogel to create a fiber-reinforced hydrogel composite in which fiber density and hydrogel stiffness can be orthogonally tuned. Quantification of 3D cell migration reveal these two parameters uniquely contribute to a diversity of migration phenotypes spanning amoeboid, single mesenchymal, multicellular cluster, and collective strand. By tuning biophysical and biochemical cues to elicit heterogeneous migration phenotypes, we find that collective strands best resist apoptosis. This work establishes a composite approach to modulate fibrous topography and bulk hydrogel mechanics and identified biomaterial parameters to direct distinct 3D cell migration phenotypes.

AMPK is a mechano-metabolic sensor linking cell adhesion and mitochondrial dynamics to Myosin-dependent cell migration

Cell migration is crucial for cancer dissemination. We find that AMP-activated protein kinase (AMPK) controls cell migration by acting as an adhesion sensing molecular hub. In 3-dimensional matrices, fast-migrating amoeboid cancer cells exert low adhesion/low traction linked to low ATP/AMP, leading to AMPK activation. In turn, AMPK plays a dual role controlling mitochondrial dynamics and cytoskeletal remodelling. High AMPK activity in low adhering migratory cells, induces mitochondrial fission, resulting in lower oxidative phosphorylation and lower mitochondrial ATP. Concurrently, AMPK inactivates Myosin Phosphatase, increasing Myosin II-dependent amoeboid migration. Reducing adhesion or mitochondrial fusion or activating AMPK induces efficient rounded-amoeboid migration. AMPK inhibition suppresses metastatic potential of amoeboid cancer cells in vivo, while a mitochondrial/AMPK-driven switch is observed in regions of human tumours where amoeboid cells are disseminating. We unveil how mitochondrial dynamics control cell migration and suggest that AMPK is a mechano-metabolic sensor linking energetics and the cytoskeleton.

Reciprocal intra- and extra-cellular polarity enables deep mechanosensing through layered matrices

Adherent cells migrate on layered tissue interfaces to drive morphogenesis, wound healing, and tumor invasion. Although stiffer surfaces are known to enhance cell migration, it remains unclear whether cells sense basal stiff environments buried under softer, fibrous matrix. Using layered collagen-polyacrylamide gel systems, we unveil a migration phenotype driven by cell-matrix polarity. Here, cancer (but not normal) cells with stiff base matrix generate stable protrusions, faster migration, and greater collagen deformation because of "depth mechanosensing" through the top collagen layer. Cancer cell protrusions with front-rear polarity produce polarized collagen stiffening and deformations. Disruption of either extracellular or intracellular polarity via collagen crosslinking, laser ablation, or Arp2/3 inhibition independently abrogates depth-mechanosensitive migration of cancer cells. Our experimental findings, validated by lattice-based energy minimization modeling, present a cell migration mechanism whereby polarized cellular protrusions and contractility are reciprocated by mechanical extracellular polarity, culminating in a cell-type-dependent ability to mechanosense through matrix layers.

Rapid cancer cell perineural invasion utilizes amoeboid migration

The invasion of nerves by cancer cells, or perineural invasion (PNI), is potentiated by the nerve microenvironment and is associated with adverse clinical outcomes. However, the cancer cell characteristics that enable PNI are poorly defined. Here, we generated cell lines enriched for a rapid neuroinvasive phenotype by serially passaging pancreatic cancer cells in a murine sciatic nerve model of PNI. Cancer cells isolated from the leading edge of nerve invasion showed a progressively increasing nerve invasion velocity with higher passage number. Transcriptome analysis revealed an upregulation of proteins involving the plasma membrane, cell leading edge, and cell movement in the leading neuroinvasive cells. Leading cells progressively became round and blebbed, lost focal adhesions and filipodia, and transitioned from a mesenchymal to amoeboid phenotype. Leading cells acquired an increased ability to migrate through microchannel constrictions and associated more with dorsal root ganglia than nonleading cells. ROCK inhibition reverted leading cells from an amoeboid to mesenchymal phenotype, reduced migration through microchannel constrictions, reduced neurite association, and reduced PNI in a murine sciatic nerve model. Cancer cells with rapid PNI exhibit an amoeboid phenotype, highlighting the plasticity of cancer migration mode in enabling rapid nerve invasion.

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.

Tumour Suppressor Neuron Navigator 3 and Matrix Metalloproteinase 14 are Co-expressed in Most Melanomas but Downregulated in Thick Tumours

Melanoma is a highly metastatic tumour originating from neural crest-derived melanocytes. The aim of this study was to analyse the expression of neuron navigator 3 (NAV3) in relation to membrane type-1 matrix metalloproteinase MMP14, a major regulator of invasion, in 40 primary melanomas, 15 benign naevi and 2 melanoma cell lines. NAV3 copy number changes were found in 18/27 (67%) primary melanomas, so that deletions dominated (16/27 of samples, 59%). NAV3 protein was found to be localized at the leading edge of migrating melanoma cells in vitro. Silencing of NAV3 reduced both melanoma cell migration in 2-dimensional conditions, as well as sprouting in 3-dimensional collagen I. NAV3 protein expression correlated with MMP14 in 26/37 (70%) primary melanomas. NAV3 and MMP14 were co-expressed in all tumours with Breslow thickness < 1 mm, in 11/23 of mid-thickness tumours (1-5 mm), but in only 1/6 samples of thick (> 5 mm) melanomas. Altogether, NAV3 number changes are frequent in melanomas, and NAV3 and MMP14, while expressed in all thin melanomas, are often downregulated in thicker tumours, suggesting that the lack of both NAV3 and MMP14 favours melanoma progression.

Cytoplasmic Tail of MT1-MMP: A Hub of MT1-MMP Regulation and Function

MT1-MMP (MMP-14) is a multifunctional protease that regulates ECM degradation, activation of other proteases, and a variety of cellular processes, including migration and viability in physiological and pathological contexts. Both the localization and signal transduction capabilities of MT1-MMP are dependent on its cytoplasmic domain that constitutes the final 20 C-terminal amino acids, while the rest of the protease is extracellular. In this review, we summarize the ways in which the cytoplasmic tail is involved in regulating and enacting the functions of MT1-MMP. We also provide an overview of known interactors of the MT1-MMP cytoplasmic tail and the functional significance of these interactions, as well as further insight into the mechanisms of cellular adhesion and invasion that are regulated by the cytoplasmic tail.

Click chemistry functionalization of self-assembling peptide hydrogels

Self-assembling peptide (SAP) hydrogels provide a fibrous microenvironment to cells while also giving users control of biochemical and mechanical cues. Previously, biochemical cues were introduced by physically mixing them with SAPs prior to hydrogel assembly, or by incorporating them into the SAP sequence during peptide synthesis, which limited flexibility and increased costs. To circumvent these limitations, we developed "Click SAPs," a novel formulation that can be easily functionalized via click chemistry thiol-ene reaction. Due to its high cytocompatibility, the thiol-ene click reaction is currently used to crosslink and functionalize other types of polymeric hydrogels. In this study, we developed a click chemistry compatible SAP platform by addition of a modified lysine (lysine-alloc) to the SAP sequence, enabling effective coupling of thiol-containing molecules to the SAP hydrogel network. We demonstrate the flexibility of this approach by incorporating a fluorescent dye, a cellular adhesion peptide, and a matrix metalloproteinase-sensitive biosensor using the thiol-ene reaction in 3D Click SAPs. Using atomic force microscopy, we demonstrate that Click SAPs retain the ability to self-assemble into fibers, similar to previous systems. Additionally, a range of physiologically relevant stiffnesses can be achieved by adjusting SAP concentration. Encapsulated cells maintain high viability in Click SAPs and can interact with adhesion peptides and a matrix metalloproteinase biosensor, demonstrating that incorporated molecules retain their biological activity. The Click SAP platform supports easier functionalization with a wider array of bioactive molecules and enables new investigations with temporal and spatial control of the cellular microenvironment.

Effect of Nanosecond Pulsed Currents on Directions of Cell Elongation and Migration through Time-Lapse Analysis

It is generally known that cells elongate perpendicularly to an electric field and move in the direction of the field when an electric field is applied. We have shown that irradiation of plasma-simulated nanosecond pulsed currents elongates cells, but the direction of cell elongation and migration has not been elucidated. In this study, a new time-lapse observation device that can apply nanosecond pulsed currents to cells was constructed, and software to analyze cell migration was created to develop a device that can sequentially observe cell behavior. The results showed nanosecond pulsed currents elongate cells but do not affect the direction of elongation and migration. It was also found the behavior of cells changes depending on the conditions of the current application.

The emerging role of microtubules in invasion plasticity

The ability of cells to switch between different invasive modes during metastasis, also known as invasion plasticity, is an important characteristic of tumor cells that makes them able to resist treatment targeted to a particular invasion mode. Due to the rapid changes in cell morphology during the transition between mesenchymal and amoeboid invasion, it is evident that this process requires remodeling of the cytoskeleton. Although the role of the actin cytoskeleton in cell invasion and plasticity is already quite well described, the contribution of microtubules is not yet fully clarified. It is not easy to infer whether destabilization of microtubules leads to higher invasiveness or the opposite since the complex microtubular network acts differently in diverse invasive modes. While mesenchymal migration typically requires microtubules at the leading edge of migrating cells to stabilize protrusions and form adhesive structures, amoeboid invasion is possible even in the absence of long, stable microtubules, albeit there are also cases of amoeboid cells where microtubules contribute to effective migration. Moreover, complex crosstalk of microtubules with other cytoskeletal networks participates in invasion regulation. Altogether, microtubules play an important role in tumor cell plasticity and can be therefore targeted to affect not only cell proliferation but also invasive properties of migrating cells.

Challenges and Opportunities Modeling the Dynamic Tumor Matrisome

We need novel strategies to target the complexity of cancer and, particularly, of metastatic disease. As an example of this complexity, certain tissues are particularly hospitable environments for metastases, whereas others do not contain fertile microenvironments to support cancer cell growth. Continuing evidence that the extracellular matrix (ECM) of tissues is one of a host of factors necessary to support cancer cell growth at both primary and secondary tissue sites is emerging. Research on cancer metastasis has largely been focused on the molecular adaptations of tumor cells in various cytokine and growth factor environments on 2-dimensional tissue culture polystyrene plates. Intravital imaging, conversely, has transformed our ability to watch, in real time, tumor cell invasion, intravasation, extravasation, and growth. Because the interstitial ECM that supports all cells in the tumor microenvironment changes over time scales outside the possible window of typical intravital imaging, bioengineers are continuously developing both simple and sophisticated in vitro controlled environments to study tumor (and other) cell interactions with this matrix. In this perspective, we focus on the cellular unit responsible for upholding the pathologic homeostasis of tumor-bearing organs, cancer-associated fibroblasts (CAFs), and their self-generated ECM. The latter, together with tumoral and other cell secreted factors, constitute the "tumor matrisome". We share the challenges and opportunities for modeling this dynamic CAF/ECM unit, the tools and techniques available, and how the tumor matrisome is remodeled (e.g., via ECM proteases). We posit that increasing information on tumor matrisome dynamics may lead the field to alternative strategies for personalized medicine outside genomics.

Moving through a changing world: Single cell migration in 2D vs. 3D

Migration of single adherent cells is frequently observed in the developing and adult organism and has been the subject of many studies. Yet, while elegant work has elucidated molecular and mechanical cues affecting motion dynamics on a flat surface, it remains less clear how cells migrate in a 3D setting. In this review, we explore the changing parameters encountered by cells navigating through a 3D microenvironment compared to cells crawling on top of a 2D surface, and how these differences alter subcellular structures required for propulsion. We further discuss how such changes at the micro-scale impact motion pattern at the macro-scale.

Graphene Hydrogel as a Porous Scaffold for Cartilage Regeneration

Porous scaffolds have widely been exploited in cartilage tissue regeneration. However, it is often difficult to understand how the delicate hierarchical structure of the scaffold material affects the regeneration process. Graphene materials are versatile building blocks for robust and biocompatible porous structures, enabling investigation of structural cues on tissue regeneration otherwise challenging to ascertain. Here, we utilize a graphene hydrogel with stable and tunable structure as a model scaffold to examine the effect of porous structure on matrix remodeling associated with ingrowth of chondrocytes on scaffolds. We observe much-accelerated yet balanced cartilage remodeling correlating the ingrowth of chondrocytes into the graphene scaffold with an open pore structure on the surface. Importantly, such an enhanced remodeling selectively promotes the expression of collagen type II fibrils over proteoglycan aggrecan, hence clearly illustrating that chondrocytes maintain a stable phenotype when they migrate into the scaffold while offering new insights into scaffold design for cartilage repair.

A Clockwork Bleb: cytoskeleton, calcium, and cytoplasmic fluidity

When the plasma membrane (PM) detaches from the underlying actin cortex, the PM expands according to intracellular pressure and a spherical membrane protrusion called a bleb is formed. This bleb retracts when the actin cortex is reassembled underneath the PM. Whereas this phenomenon seems simple at first glance, there are many interesting, unresolved cell biological questions in each process. For example, what is the membrane source to enlarge the surface area of the PM during rapid bleb expansion? What signals induce actin reassembly for bleb retraction, and how is cytoplasmic fluidity regulated to allow rapid membrane deformation during bleb expansion? Furthermore, emerging evidence indicates that cancer cells use blebs for invasion, but little is known about how molecules that are involved in bleb formation, expansion, and retraction are coordinated for directional amoeboid migration. In this review, we discuss the molecular mechanisms involved in the regulation of blebs, which have been revealed by various experimental systems.

Poly(ε-Caprolactone) Substrates with Micro/Nanohierarchical Patterned Structures for Cell Culture

A simple, efficient and controllable one-step template method is proposed to fabricate poly(ε-caprolactone) substrates with micro/nanohierarchical patterned structures. Two kinds of geometric patterns with and without nanowires, i.e., hexagonal and strip with controllable island size and spacing are designed and fabricated. Furthermore, the influence of geometric patterns, island size, island spacing, and patterned nanowires (pNW) on the growth behavior of MG-63 cells is studied in terms of cell density, distribution, proliferation, morphogenesis, and cellular alignment. It is found that MG-63 cells prefer to adhere and grow on the substrate with smaller island size or spacing. Moreover, unlike the hexagonal structure, the strip structure can guide cellular alignment on its surface. In addition, the microisland structures and the pNW play different roles in promoting cell proliferation, distribution, and morphogenesis. It is concluded that the growth behavior of MG-63 cells can be well controlled by precisely adjusting the micro/nanostructure of the substrate surface. A simple and effective method is provided here for the regulation of cell growth behavior.

Non-muscle myosin II and the plasticity of 3D cell migration

Confined cells migrating through 3D environments are also constrained by the laws of physics, meaning for every action there must be an equal and opposite reaction for cells to achieve motion. Fascinatingly, there are several distinct molecular mechanisms that cells can use to move, and this is reflected in the diverse ways non-muscle myosin II (NMII) can generate the mechanical forces necessary to sustain 3D cell migration. This review summarizes the unique modes of 3D migration, as well as how NMII activity is regulated and localized within each of these different modes. In addition, we highlight tropomyosins and septins as two protein families that likely have more secrets to reveal about how NMII activity is governed during 3D cell migration. Together, this information suggests that investigating the mechanisms controlling NMII activity will be helpful in understanding how a single cell transitions between distinct modes of 3D migration in response to the physical environment.

Stimulus-Responsive, Gelatin-Containing Supramolecular Nanofibers as Switchable 3D Microenvironments for Cells

Polymer- and/or protein-based nanofibers that promote stable cell adhesion have drawn increasing attention as well-defined models of the extracellular matrix. In this study, we fabricated two classes of stimulus-responsive fibers containing gelatin and supramolecular crosslinks to emulate the dynamic cellular microenvironment in vivo. Gelatin enabled cells to adhere without additional surface functionalization, while supramolecular crosslinks allowed for the reversible switching of the Young’s modulus through changes in the concentration of guest molecules in culture media. The first class of nanofibers was prepared by coupling the host–guest inclusion complex to gelatin before electrospinning (pre-conjugation), while the second class of nanofibers was fabricated by coupling gelatin to polyacrylamide functionalized with host or guest moieties, followed by conjugation in the electrospinning solution (post-conjugation). In situ AFM nano-indentation demonstrated the reversible switching of the Young’s modulus between 2–3 kPa and 0.2–0.3 kPa under physiological conditions by adding/removing soluble guest molecules. As the concentration of additives does not affect cell viability, the supramolecular fibers established in this study are a promising candidate for various biomedical applications, such as standardized three-dimensional culture matrices for somatic cells and the regulation of stem cell differentiation.

How does plasticity of migration help tumor cells to avoid treatment: Cytoskeletal regulators and potential markers

Tumor shrinkage as a result of antitumor therapy is not the only and sufficient indicator of treatment success. Cancer progression leads to dissemination of tumor cells and formation of metastases - secondary tumor lesions in distant organs. Metastasis is associated with acquisition of mobile phenotype by tumor cells as a result of epithelial-to-mesenchymal transition and further cell migration based on cytoskeleton reorganization. The main mechanisms of individual cell migration are either mesenchymal, which depends on the activity of small GTPase Rac, actin polymerization, formation of adhesions with extracellular matrix and activity of proteolytic enzymes or amoeboid, which is based on the increase in intracellular pressure caused by the enhancement of actin cortex contractility regulated by Rho-ROCK-MLCKII pathway, and does not depend on the formation of adhesive structures with the matrix, nor on the activity of proteases. The ability of tumor cells to switch from one motility mode to another depending on cell context and environmental conditions, termed migratory plasticity, contributes to the efficiency of dissemination and often allows the cells to avoid the applied treatment. The search for new therapeutic targets among cytoskeletal proteins offers an opportunity to directly influence cell migration. For successful treatment it is important to assess the likelihood of migratory plasticity in a particular tumor. Therefore, the search for specific markers that can indicate a high probability of migratory plasticity is very important.

Multimodal microscale mechanical mapping of cancer cells in complex microenvironments

The mechanical phenotype of the cell is critical for survival following deformations due to confinement and fluid flow. One idea is that cancer cells are plastic and adopt different mechanical phenotypes under different geometries that aid in their survival. Thus, an attractive goal is to disrupt cancer cells' ability to adopt multiple mechanical states. To begin to address this question, we aimed to quantify the diversity of these mechanical states using in vitro biomimetics to mimic in vivo two-dimensional (2D) and 3D extracellular matrix environments. Here, we used two modalities Brillouin microscopy (∼GHz) and broadband frequency (7-15 kHz) optical tweezer microrheology to measure microscale cell mechanics. We measured the response of intracellular mechanics of cancer cells cultured in 2D and 3D environments where we modified substrate stiffness, dimensionality (2D versus 3D), and presence of fibrillar topography. We determined that there was good agreement between two modalities despite the difference in timescale of the two measurements. These findings on cell mechanical phenotype in different environments confirm a correlation between modalities that employ different mechanisms at different temporal scales (Hz-kHz versus GHz). We also determined that observed heterogeneity in cell shape is more closely linked to the cells' mechanical state. Moreover, individual cells in multicellular spheroids exhibit a lower degree of mechanical heterogeneity when compared with single cells cultured in monodisperse 3D cultures. The observed decreased heterogeneity among cells in spheroids suggested that there is mechanical cooperativity between cells that make up a single spheroid.

Water-Air Interface to Mimic In Vitro Tumoral Cell Migration in Complex Micro-Environments

The long-known role of cell migration in physiological and pathological contexts still requires extensive research to be fully understood, mainly because of the intricate interaction between moving cells and their surroundings. While conventional assays fail to capture this complexity, recently developed 3D platforms better reproduce the cellular micro-environment, although often requiring expensive and time-consuming imaging approaches. To overcome these limitations, we developed a novel approach based on 2D micro-patterned substrates, compatible with conventional microscopy analysis and engineered to create micro-gaps with a length of 150 µm and a lateral size increasing from 2 to 8 µm, where a curved water-air interface is created on which cells can adhere, grow, and migrate. The resulting hydrophilic/hydrophobic interfaces, variable surface curvatures, spatial confinements, and size values mimic the complex micro-environment typical of the extracellular matrix in which aggressive cancer cells proliferate and migrate. The new approach was tested with two breast cancer cell lines with different invasive properties. We observed that invasive cells (MDA-MB-231) can align along the pattern and modify both their morphology and their migration rate according to the size of the water meniscus, while non-invasive cells (MCF-7) are only slightly respondent to the surrounding micro-environment. Moreover, the selected pattern highlighted a significative matrix deposition process connected to cell migration. Although requiring further optimizations, this approach represents a promising tool to investigate cell migration in complex environments.

Anti-Human CD9 Fab Fragment Antibody Blocks the Extracellular Vesicle-Mediated Increase in Malignancy of Colon Cancer Cells

Intercellular communication between cancer cells themselves or with healthy cells in the tumor microenvironment and/or pre-metastatic sites plays an important role in cancer progression and metastasis. In addition to ligand-receptor signaling complexes, extracellular vesicles (EVs) are emerging as novel mediators of intercellular communication both in tissue homeostasis and in diseases such as cancer. EV-mediated transfer of molecular activities impacting morphological features and cell motility from highly metastatic SW620 cells to non-metastatic SW480 cells is a good in vitro example to illustrate the increased malignancy of colorectal cancer leading to its transformation and aggressive behavior. In an attempt to intercept the intercellular communication promoted by EVs, we recently developed a monovalent Fab fragment antibody directed against human CD9 tetraspanin and showed its effectiveness in blocking the internalization of melanoma cell-derived EVs and the nuclear transfer of their cargo proteins into recipient cells. Here, we employed the SW480/SW620 model to investigate the anti-cancer potential of the anti-CD9 Fab antibody. We first demonstrated that most EVs derived from SW620 cells contain CD9, making them potential targets. We then found that the anti-CD9 Fab antibody, but not the corresponding divalent antibody, prevented internalization of EVs from SW620 cells into SW480 cells, thereby inhibiting their phenotypic transformation, i.e., the change from a mesenchymal-like morphology to a rounded amoeboid-like shape with membrane blebbing, and thus preventing increased cell migration. Intercepting EV-mediated intercellular communication in the tumor niche with an anti-CD9 Fab antibody, combined with direct targeting of cancer cells, could lead to the development of new anti-cancer therapeutic strategies.