Cancer cell motility: lessons from migration in confined spaces

NETosis-Inspired Cell Surface-Constrained Framework Nucleic Acids Traps (FNATs) for Cascaded Extracellular Recognition and Cellular Behavior Modulation

Upon pathogenic stimulation, activated neutrophils release nuclear DNA into the extracellular environment, forming web-like DNA structures known as neutrophil extracellular traps (NETs), which capture and kill bacteria, fungi, and cancer cells. This phenomenon is commonly referred to as NETosis. Inspired by this, we introduce a cell surface-constrained web-like framework nucleic acids traps (FNATs) with programmable extracellular recognition capability and cellular behavior modulation. This approach facilitates dynamic key chemical signaling molecule recognition such as adenosine triphosphate (ATP), which is elevated in the extracellular microenvironment, and triggers FNA self-assembly. This, in turn, leads to in situ tightly interwoven FNAs formation on the cell surface, thereby inhibiting target cell migration. Furthermore, it activates a photosensitizer-capturing switch, chlorin e6 (Ce6), and induces cell self-destruction. This cascade platform provides new potential tools for visualizing dynamic extracellular activities and manipulating cellular behaviors using programmable in situ self-assembling DNA molecular devices.

The importance of 3D fibre architecture in cancer and implications for biomaterial model design

The need for improved prediction of clinical response is driving the development of cancer models with enhanced physiological relevance. A new concept of 'precision biomaterials' is emerging, encompassing patient-mimetic biomaterial models that seek to accurately detect, treat and model cancer by faithfully recapitulating key microenvironmental characteristics. Despite recent advances allowing tissue-mimetic stiffness and molecular composition to be replicated in vitro, approaches for reproducing the 3D fibre architectures found in tumour extracellular matrix (ECM) remain relatively unexplored. Although the precise influences of patient-specific fibre architecture are unclear, we summarize the known roles of tumour fibre architecture, underlining their implications in cell-matrix interactions and ultimately clinical outcome. We then explore the challenges in reproducing tissue-specific 3D fibre architecture(s) in vitro, highlighting relevant biomaterial fabrication techniques and their benefits and limitations. Finally, we discuss imaging and image analysis techniques (focussing on collagen I-optimized approaches) that could hold the key to mapping tumour-specific ECM into high-fidelity biomaterial models. We anticipate that an interdisciplinary approach, combining materials science, cancer research and image analysis, will elucidate the role of 3D fibre architecture in tumour development, leading to the next generation of patient-mimetic models for mechanistic studies and drug discovery.

Mitochondria- and endoplasmic reticulum-localizing iridium(III) complexes induce immunogenic cell death of 143B cells

Recent breakthroughs in cancer immunology have propelled immunotherapy to the forefront of cancer research as a promising treatment approach that harnesses the body's immune system to effectively identify and eliminate cancer cells. In this study, three novel cyclometalated Ir(III) complexes, Ir1, Ir2, and Ir3, were designed, synthesized, and assessed in vitro for cytotoxic activity against several tumor-derived cell lines. Among these, Ir1 exhibited the highest cytotoxic activity, with an IC50 value of 0.4 ± 0.1 μM showcasing its significant anticancer potential. Detailed mechanistic analysis revealed that co-incubation of Ir1 with 143B cells led to Ir1 accumulation within mitochondria and the endoplasmic reticulum (ER). Furthermore, Ir1 induced G0/G1 phase cell cycle arrest, while also diminishing mitochondrial membrane potential, disrupting mitochondrial function, and triggering ER stress. Intriguingly, in mice the Ir1-induced ER stress response disrupted calcium homeostasis to thereby trigger immunogenic cell death (ICD), which subsequently activated the host antitumor immune response while concurrently dampening the in vivo tumor-induced inflammatory response.

Tension directs cancer cell migration over fiber alignment through energy minimization

Cell migration during many fundamental biological processes including metastasis requires cells to traverse tissue with heterogeneous mechanical cues that direct migration as well as determine force and energy requirements for motility. However, the influence of discrete structural and mechanical cues on migration remains challenging to determine as they are often coupled. Here, we decouple the pro-invasive cues of collagen fiber alignment and tension to study their individual impact on migration. When presented with both cues, cells preferentially travel in the axis of tension against fiber alignment. Computational and experimental data show applying tension perpendicular to alignment increases potential energy stored within collagen fibers, lowering requirements for cell-induced matrix deformation and energy usage during migration compared to motility in the direction of fiber alignment. Energy minimization directs migration trajectory, and tension can facilitate migration against fiber alignment. These findings provide a conceptual understanding of bioenergetics during migration through a fibrous matrix.

Impact of mechanical cues on key cell functions and cell-nanoparticle interactions

In recent years, it has been recognized that mechanical forces play an important regulative role in living organisms and possess a direct impact on crucial cell functions, ranging from cell growth to maintenance of tissue homeostasis. Advancements in mechanobiology have revealed the profound impact of mechanical signals on diverse cellular responses that are cell type specific. Notably, numerous studies have elucidated the pivotal role of different mechanical cues as regulatory factors influencing various cellular processes, including cell spreading, locomotion, differentiation, and proliferation. Given these insights, it is unsurprising that the responses of cells regulated by physical forces are intricately linked to the modulation of nanoparticle uptake kinetics and processing. This complex interplay underscores the significance of understanding the mechanical microenvironment in shaping cellular behaviors and, consequently, influencing how cells interact with and process nanoparticles. Nevertheless, our knowledge on how localized physical forces affect the internalization and processing of nanoparticles by cells remains rather limited. A significant gap exists in the literature concerning a systematic analysis of how mechanical cues might bias the interactions between nanoparticles and cells. Hence, our aim in this review is to provide a comprehensive and critical analysis of the existing knowledge regarding the influence of mechanical cues on the complicated dynamics of cell-nanoparticle interactions. By addressing this gap, we would like to contribute to a detailed understanding of the role that mechanical forces play in shaping the complex interplay between cells and nanoparticles.

Enhancing PKA-dependent mesothelial barrier integrity reduces ovarian cancer transmesothelial migration via inhibition of contractility

Cancer-mesothelial cell interactions are critical for multiple solid tumors to colonize the surface of peritoneal organs. Understanding mechanisms of mesothelial barrier dysfunction that impair its protective function is critical for discovering mesothelial-targeted therapies to combat metastatic spread. Here, we utilized a live cell imaging-based assay to elucidate the dynamics of ovarian cancer spheroid transmesothelial migration and mesothelial-generated mechanical forces. Treatment of mesothelial cells with the adenylyl cyclase agonist forskolin strengthens cell-cell junctions, reduces actomyosin fibers, contractility-driven matrix displacements, and cancer spheroid transmigration in a protein kinase A (PKA)-dependent mechanism. We also show that inhibition of the cytoskeletal regulator Rho-associated kinase in mesothelial cells phenocopies the anti-metastatic effects of forskolin. Conversely, upregulation of contractility in mesothelial cells disrupts cell-cell junctions and increases the clearance rates of ovarian cancer spheroids. Our findings demonstrate the critical role of mesothelial cell contractility and mesothelial barrier integrity in regulating metastatic dissemination within the peritoneal microenvironment.

Design of Selective PARP-1 Inhibitors and Antitumor Studies

Designing selective PARP-1 inhibitors has become a new strategy for anticancer drug development. By sequence comparison of PARP-1 and PARP-2, we identified a possible selective site (S site) consisting of several different amino acid residues of α-5 helix and D-loop. Targeting this S site, 140 compounds were designed, synthesized, and characterized for their anticancer activities and mechanisms. Compound I16 showed the highest PARP-1 enzyme inhibitory activity (IC50 = 12.38 ± 1.33 nM) and optimal selectivity index over PARP-2 (SI = 155.74). Oral administration of I16 (25 mg/kg) showed high inhibition rates of Hela and SK-OV-3 tumor cell xenograft models, both of which were higher than those of the oral positive drug Olaparib (50 mg/kg). In addition, I16 has an excellent safety profile, without significant toxicity at high oral doses. These findings provide a novel design strategy and chemotype for the development of safe, efficient, and highly selective PARP-1 inhibitors.

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.

The impact of tumor microenvironment: unraveling the role of physical cues in breast cancer progression

Metastasis accounts for the vast majority of breast cancer-related fatalities. Although the contribution of genetic and epigenetic modifications to breast cancer progression has been widely acknowledged, emerging evidence underscores the pivotal role of physical stimuli in driving breast cancer metastasis. In this review, we summarize the changes in the mechanics of the breast cancer microenvironment and describe the various forces that impact migrating and circulating tumor cells throughout the metastatic process. We also discuss the mechanosensing and mechanotransducing molecules responsible for promoting the malignant phenotype in breast cancer cells. Gaining a comprehensive understanding of the mechanobiology of breast cancer carries substantial potential to propel progress in prognosis, diagnosis, and patient treatment.

Single-molecule magnetic tweezers to probe the equilibrium dynamics of individual proteins at physiologically relevant forces and timescales

The reversible unfolding and refolding of proteins is a regulatory mechanism of tissue elasticity and signalling used by cells to sense and adapt to extracellular and intracellular mechanical forces. However, most of these proteins exhibit low mechanical stability, posing technical challenges to the characterization of their conformational dynamics under force. Here, we detail step-by-step instructions for conducting single-protein nanomechanical experiments using ultra-stable magnetic tweezers, which enable the measurement of the equilibrium conformational dynamics of single proteins under physiologically relevant low forces applied over biologically relevant timescales. We report the basic principles determining the functioning of the magnetic tweezer instrument, review the protein design strategy and the fluid chamber preparation and detail the procedure to acquire and analyze the unfolding and refolding trajectories of individual proteins under force. This technique adds to the toolbox of single-molecule nanomechanical techniques and will be of particular interest to those interested in proteins involved in mechanosensing and mechanotransduction. The procedure takes 4 d to complete, plus an additional 6 d for protein cloning and production, requiring basic expertise in molecular biology, surface chemistry and data analysis.

Mechanical regulation of mitochondrial morphodynamics in cancer cells by extracellular microenvironment

Recently, it has been recognized that physical abnormalities (e.g. elevated solid stress, elevated interstitial fluid pressure, increased stiffness) are associated with tumor progression and development. Additionally, these mechanical forces originating from tumor cell environment through mechanotransduction pathways can affect metabolism. On the other hand, mitochondria are well-known as bioenergetic, biosynthetic, and signaling organelles crucial for sensing stress and facilitating cellular adaptation to the environment and physical stimuli. Disruptions in mitochondrial dynamics and function have been found to play a role in the initiation and advancement of cancer. Consequently, it is logical to hypothesize that mitochondria dynamics subjected to physical cues may play a pivotal role in mediating tumorigenesis. Recently mitochondrial biogenesis and turnover, fission and fusion dynamics was linked to mechanotransduction in cancer. However, how cancer cell mechanics and mitochondria functions are connected, still remain poorly understood. Here, we discuss recent studies that link mechanical stimuli exerted by the tumor cell environment and mitochondria dynamics and functions. This interplay between mechanics and mitochondria functions may shed light on how mitochondria regulate tumorigenesis.

Insights into the mechanobiology of cancer metastasis via microfluidic technologies

During cancer metastasis, cancer cells will encounter various microenvironments with diverse physical characteristics. Changes in these physical characteristics such as tension, stiffness, viscosity, compression, and fluid shear can generate biomechanical cues that affect cancer cells, dynamically influencing numerous pathophysiological mechanisms. For example, a dense extracellular matrix drives cancer cells to reorganize their cytoskeleton structures, facilitating confined migration, while this dense and restricted space also acts as a physical barrier that potentially results in nuclear rupture. Identifying these pathophysiological processes and understanding their underlying mechanobiological mechanisms can aid in the development of more effective therapeutics targeted to cancer metastasis. In this review, we outline the advances of engineering microfluidic devices in vitro and their role in replicating tumor microenvironment to mimic in vivo settings. We highlight the potential cellular mechanisms that mediate their ability to adapt to different microenvironments. Meanwhile, we also discuss some important mechanical cues that still remain challenging to replicate in current microfluidic devices in future direction. While much remains to be explored about cancer mechanobiology, we believe the developments of microfluidic devices will reveal how these physical cues impact the behaviors of cancer cells. It will be crucial in the understanding of cancer metastasis, and potentially contributing to better drug development and cancer therapy.

Deposited footprints let cells switch between confined, oscillatory, and exploratory migration

For eukaryotic cells to heal wounds, respond to immune signals, or metastasize, they must migrate, often by adhering to extracellular matrix (ECM). Cells may also deposit ECM components, leaving behind a footprint that influences their crawling. Recent experiments showed that some epithelial cell lines on micropatterned adhesive stripes move persistently in regions they have previously crawled over, where footprints have been formed, but barely advance into unexplored regions, creating an oscillatory migration of increasing amplitude. Here, we explore through mathematical modeling how footprint deposition and cell responses to footprint combine to allow cells to develop oscillation and other complex migratory motions. We simulate cell crawling with a phase field model coupled to a biochemical model of cell polarity, assuming local contact with the deposited footprint activates Rac1, a protein that establishes the cell's front. Depending on footprint deposition rate and response to the footprint, cells on micropatterned lines can display many types of motility, including confined, oscillatory, and persistent motion. On two-dimensional (2D) substrates, we predict a transition between cells undergoing circular motion and cells developing an exploratory phenotype. Small quantitative changes in a cell's interaction with its footprint can completely alter exploration, allowing cells to tightly regulate their motion, leading to different motility phenotypes (confined vs. exploratory) in different cells when deposition or sensing is variable from cell to cell. Consistent with our computational predictions, we find in earlier experimental data evidence of cells undergoing both circular and exploratory motion.

Anchorage of H3K9-methylated heterochromatin to the nuclear periphery helps mediate P-cell nuclear migration though constricted spaces in Caenorhabditis elegans

Nuclei adjust their deformability while migrating through constrictions to enable structural changes and maintain nuclear integrity. The effect of heterochromatin anchored at the nucleoplasmic face of the inner nuclear membrane on nuclear morphology and deformability during in vivo nuclear migration through constricted spaces remains unclear. Here, we show that abolishing peripheral heterochromatin anchorage by eliminating CEC-4, a chromodomain protein that tethers H3K9-methylated chromatin to the nuclear periphery, disrupts constrained P-cell nuclear migration in Caenorhabditis elegans larvae in the absence of the established LINC complex-dependent pathway. CEC-4 acts in parallel to an actin and CDC-42-based pathway. We also demonstrate the necessity for the chromatin methyltransferases MET-2 and JMJD-1.2 during P-cell nuclear migration in the absence of functional LINC complexes. We conclude that H3K9-nethylated chromatin needs to be anchored to the nucleoplasmic face of the inner nuclear membrane to help facilitate nuclear migration through constricted spaces in vivo.

Deposited footprints let cells switch between confined, oscillatory, and exploratory migration

For eukaryotic cells to heal wounds, respond to immune signals, or metastasize, they must migrate, often by adhering to extracellular matrix. Cells may also deposit extracellular matrix components, leaving behind a footprint that influences their crawling. Recent experiments showed that some epithelial cells on micropatterned adhesive stripes move persistently in regions they have previously crawled over, where footprints have been formed, but barely advance into unexplored regions, creating an oscillatory migration of increasing amplitude. Here, we explore through mathematical modeling how footprint deposition and cell responses to footprint combine to allow cells to develop oscillation and other complex migratory motions. We simulate cell crawling with a phase field model coupled to a biochemical model of cell polarity, assuming local contact with the deposited footprint activates Rac1, a protein that establishes the cell's front. Depending on footprint deposition rate and response to the footprint, cells on micropatterned lines can display many types of motility, including confined, oscillatory, and persistent motion. On two-dimensional substrates, we predict a transition between cells undergoing circular motion and cells developing an exploratory phenotype. Small quantitative changes in a cell's interaction with its footprint can completely alter exploration, allowing cells to tightly regulate their motion, leading to different motility phenotypes (confined vs exploratory) in different cells when deposition or sensing is variable from cell to cell. Consistent with our computational predictions, we find in earlier experimental data evidence of cells undergoing both circular and exploratory motion.

The amoeboid migration of monocytes in confining channels requires the local remodeling of the cortical actin cytoskeleton by cofilin-1

Within the bloodstream, monocytes must traverse the microvasculature to prevent leukostasis, which is the entrapment of monocytes within the confines of the microvasculature. Using the model cell line, THP-1, and VCAM-1 coated channels to simulate the microvasculature surface, we demonstrate that monocytes predominantly adopt an amoeboid phenotype, which is characterized by the formation of blebs. As opposed to cortical actin flow in leader blebs, cell movement is correlated with myosin contraction at the cell rear. It was previously documented that cofilin-1 promotes cortical actin turnover at leader bleb necks in melanoma cells. In monocytes, our data suggest that cofilin-1 promotes the local upregulation of myosin contractility through actin cytoskeleton remodeling. In support of this concept, cofilin-1 is found to localize to a single cell edge. Moreover, the widespread upregulation of myosin contractility was found to inhibit migration. Thus, monocytes within the microvasculature may avoid entrapment by adopting an amoeboid mode of migration.

Fuyuan decoction prevents nasopharyngeal carcinoma metastasis by inhibiting circulating tumor cells/ endothelial cells interplay and enhancing anti-cancer immune response

Distant metastasis is a major cause of treatment failure in cancer patients and a key challenge to improving cancer care today. We hypothesized that enhancing anti-cancer immune response and inhibiting circulating tumor cells (CTCs) adhesion and transendothelial migration through synergistic multi-target approaches may effectively prevent cancer metastasis. "Fuyuan Decoction" (FYD) is a traditional Chinese medicine compound that is widely used to prevent postoperative metastasis in cancer patients, but its underlying mechanism remains unclear. In this work, we systematically elucidated the underlying molecular mechanism by which FYD prevents cancer metastasis through multi-compound and multi-target synergies in vitro and in vivo. FYD significantly prevented cancer metastasis at non-cytotoxic concentrations by suppressing the adhesion of CTCs to endothelial cells and their subsequent transendothelial migration, as well as enhancing anti-cancer immune response. Mechanistically, FYD interrupts adhesion of CTCs to vascular endothelium by inhibiting TNF-α-induced CAMs expression via regulation of the NF-κB signaling pathway in endothelial cells. FYD inhibits invasion and migration of CTCs by suppressing EMT, PI3K/AKT and FAK signaling pathways. Moreover, FYD enhances the anti-cancer immune response by significantly increasing the population of Tc and NK cells in the peripheral immune system. In addition, the chemical composition of FYD was determined by UPLC-HRMS, and the results indicated that multiple compounds in FYD prevents cancer metastasis through multi-target synergistic treatment. This study provides a modern medical basis for the application of FYD in the prevention of cancer metastasis, and suggesting that multi-drug and multi-target synergistic therapy may be one of the most effective ways to prevent cancer metastasis.

Membrane to cortex attachment determines different mechanical phenotypes in LGR5+ and LGR5- colorectal cancer cells

Colorectal cancer (CRC) tumors are composed of heterogeneous and plastic cell populations, including a pool of cancer stem cells that express LGR5. Whether these distinct cell populations display different mechanical properties, and how these properties might contribute to metastasis is poorly understood. Using CRC patient derived organoids (PDOs), we find that compared to LGR5- cells, LGR5+ cancer stem cells are stiffer, adhere better to the extracellular matrix (ECM), move slower both as single cells and clusters, display higher nuclear YAP, show a higher survival rate in response to mechanical confinement, and form larger transendothelial gaps. These differences are largely explained by the downregulation of the membrane to cortex attachment proteins Ezrin/Radixin/Moesin (ERMs) in the LGR5+ cells. By analyzing single cell RNA-sequencing (scRNA-seq) expression patterns from a patient cohort, we show that this downregulation is a robust signature of colorectal tumors. Our results show that LGR5- cells display a mechanically dynamic phenotype suitable for dissemination from the primary tumor whereas LGR5+ cells display a mechanically stable and resilient phenotype suitable for extravasation and metastatic growth.

Squaraine Dyes Exhibit Spontaneous Fluorescence Blinking That Enables Live-Cell Nanoscopy

Hampered by their susceptibility to nucleophilic attack and chemical bleaching, electron-deficient squaraine dyes have long been considered unsuitable for biological imaging. This study unveils a surprising twist: in aqueous environments, bleaching is not irreversible but rather a reversible spontaneous quenching process. Leveraging this new discovery, we introduce a novel deep-red squaraine probe tailored for live-cell super-resolution imaging. This probe enables single-molecule localization microscopy (SMLM) under physiological conditions without harmful additives or intense lasers and exhibits spontaneous blinking orchestrated by biological nucleophiles, such as glutathione or hydroxide anion. With a low duty cycle (∼0.1%) and high-emission rate (∼6 × 104 photons/s under 400 W/cm2), the squaraine probe surpasses the benchmark Cy5 dye by 4-fold and Si-rhodamine by a factor of 1.7 times. Live-cell SMLM with the probe reveals intricate structural details of cell membranes, which demonstrates the high potential of squaraine dyes for next-generation super-resolution imaging.

Learning dynamical models of single and collective cell migration: a review

Single and collective cell migration are fundamental processes critical for physiological phenomena ranging from embryonic development and immune response to wound healing and cancer metastasis. To understand cell migration from a physical perspective, a broad variety of models for the underlying physical mechanisms that govern cell motility have been developed. A key challenge in the development of such models is how to connect them to experimental observations, which often exhibit complex stochastic behaviours. In this review, we discuss recent advances in data-driven theoretical approaches that directly connect with experimental data to infer dynamical models of stochastic cell migration. Leveraging advances in nanofabrication, image analysis, and tracking technology, experimental studies now provide unprecedented large datasets on cellular dynamics. In parallel, theoretical efforts have been directed towards integrating such datasets into physical models from the single cell to the tissue scale with the aim of conceptualising the emergent behaviour of cells. We first review how this inference problem has been addressed in both freely migrating and confined cells. Next, we discuss why these dynamics typically take the form of underdamped stochastic equations of motion, and how such equations can be inferred from data. We then review applications of data-driven inference and machine learning approaches to heterogeneity in cell behaviour, subcellular degrees of freedom, and to the collective dynamics of multicellular systems. Across these applications, we emphasise how data-driven methods can be integrated with physical active matter models of migrating cells, and help reveal how underlying molecular mechanisms control cell behaviour. Together, these data-driven approaches are a promising avenue for building physical models of cell migration directly from experimental data, and for providing conceptual links between different length-scales of description.

Small Molecule SHP2 Inhibitor LXQ-217 Affects Lung Cancer Cell Proliferation in Vitro and in Vivo

BACKGROUND

SHP2 is highly expressed in a variety of cancer and has emerged as a potential target for cancer therapeutic agents. The identification of uncharged pTyr mimics is an important direction for the development of SHP2 orthosteric inhibitors.

METHODS

Surface plasmon resonance analysis and cellular thermal shift assay were employed to verify the direct binding of LXQ-217 to SHP2. The inhibitory effect of LXQ-217 was characterized by linear Weaver-Burke enzyme kinetic analysis and BIOVIA Discovery Studio. The inhibition of tumor cell proliferation by LXQ-217 was characterized by cell viability assay, colony formation assays and hoechst 33258 staining. The inhibition of lung cancer proliferation in vivo was studied in nude mice after oral administration of LXQ-217.

RESULTS

An electroneutral bromophenol derivative, LXQ-217, was identified as a competitive SHP2 inhibitor. LXQ-217 induced apoptosis and inhibited growth of human pulmonary epithelial cells by affecting the RAS-ERK and PI3 K-AKT signaling pathways. Long-term oral administration of LXQ-217 significantly inhibited the proliferation ability of lung cancer cells in nude mice. Moreover, mice administered LXQ-217 orally at high doses exhibited no mortality or significant changes in vital signs.

CONCLUSIONS

Our findings on the uncharged orthosteric inhibitor provide a foundation for further development of a safe and effective anti-lung cancer drug.

Emergence, Pattern, and Frequency of Spontaneous Waves in Spreading Epithelial Monolayers

A striking phenomenon of collective cell motion is that they can exhibit a spontaneously emerging wave during epithelia expansions. However, the fundamental mechanism, governing the emergence and its crucial characteristics (e.g., the eigenfrequency and the pattern), remains an enigma. By introducing a mechanochemical feedback loop, we develop a highly efficient discrete vertex model to investigate the spatiotemporal evolution of spreading epithelia. We find both numerically and analytically that expanding cell monolayers display a power-law dependence of wave frequency on the local heterogeneities (i.e., cell density) with a scaling exponent of -1/2. Moreover, our study demonstrates the quantitative capability of the proposed model in capturing distinct X-, W-, and V-mode wave patterns. We unveil that the phase transition between these modes is governed by the distribution of active self-propulsion forces. Our work provides an avenue for rigorous quantitative investigations into the collective motion and pattern formation of cell groups.

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.

Protocol for in situ visualization of mitochondrial ROS and apoptosis in spatially confined cells and sample preparation for biochemical analysis

Locomotion through spatially confining spaces is an important in vivo migration mode. Here, we present a protocol for in situ visualization of mitochondrial reactive oxygen species and apoptosis in cancer cells during confined migration. We then detail sample preparation of confined cells for transcriptome and immunoblotting analysis by using transwell chambers. This approach allows in situ evaluation of a variety of cellular functions during confined migration and preparation of the samples of confined cells for further biochemical analysis. For complete details on the use and execution of this protocol, please refer to Cai et al.1.

Investigation the apoptotic effect of silver nanoparticles (Ag-NPs) on MDA-MB 231 breast cancer epithelial cells via signaling pathways

Background

The discovery of novel cancer therapeutic strategies leads to the development of nanotechnology-based methods for cancer treatment. Silver nanoparticles (Ag-NPs) have garnered considerable interest owing to their size, shape, and capacity to modify chemical, optical, and photonic properties. This study aimed to investigate the impact of Ag-NPs on inducing of apoptosis in MDA-MB 231 cells by examining specific signaling pathways.

Materials and methods

The cytotoxicity of Ag-NPs was determined using an MTT assay in MDA-MB 231 cells. The apoptotic effects were assessed using the Annexin-V/PI assay. Real-time PCR and western blotting were conducted to analyze the expression of apoptosis-related genes and proteins, respectively. Levels of ERK1/2 and cyclin D1 were measured using ELISA. Cell cycle assay was determined by flow cytometry. Cell migration was evaluated by scratch assay.

Results

The results revealed that Ag-NPs triggered apoptosis and cell cycle arrest in MDA-MB 231 cells. The expression level of Bax (pro-apoptotic gene) was increased, while Bcl-2 (anti-apoptotic gene) expression was decreased. Increased apoptosis was correlated with increased levels of p53 and PTEN. Additionally, notable alterations were observed in protein expression related to the Janus kinase/Signal transducers (JAK/STAT) pathway, including p-AKT. Additionally, reduced expression of h-TERT was observed following exposure to Ag-NPs. ELISA results demonstrated a significant reduction in p-ERK/Total ERK and cyclin D1 levels in Ag-NPs-exposed MDA-MB 231 cells. Western blotting analysis also confirmed the reduction of p-ERK/Total ERK and cyclin D1. Decreased level of cyclin D is associated with suppression of cell cycle progression. The migratory ability of MDA-MB-231 cells was reduced upon treatment with Ag-NPs.

Conclusions

Our findings revealed that Ag-NPs influenced the proliferation, apoptosis, cell cycle, and migration in MDA-MB 231 cells, possibly by modulating protein expression of the AKT/ERK/Cyclin D1 axis.

The activation of INF2 by Piezo1/Ca2+ is required for mesenchymal to amoeboid transition in confined environments

To invade heterogenous tissues, transformed cells may undergo a mesenchymal to amoeboid transition (MAT). However, the molecular mechanisms regulating this transition are poorly defined. In invasive melanoma cells, we demonstrate that intracellular [Ca2+] increases with the degree of confinement in a Piezo1 dependent fashion. Moreover, Piezo1/Ca2+ is found to drive amoeboid and not mesenchymal migration in confined environments. Consistent with a model in which Piezo1 senses tension at the plasma membrane, the percentage of cells using amoeboid migration is further increased in undulating microchannels. Surprisingly, amoeboid migration was not promoted by myosin light chain kinase (MLCK), which is sensitive to intracellular [Ca2+]. Instead, we report that Piezo1/Ca2+ activates inverted formin-2 (INF2) to induce widespread actin cytoskeletal remodeling. Strikingly, the activation of INF2 is found to promote de-adhesion, which in turn facilitates MAT. Using micropatterned surfaces, we demonstrate that cells require INF2 to effectively migrate in environments with challenging mechanochemical properties.

Advances in research on the anti-tumor mechanism of Astragalus polysaccharides

The dry root of the soybean plant Astragalus membranaceus (Fisch) Bge. var. mongholicus (Bge) Hsiao or A. membranaceus (Fisch) Bge, Astragali Radix (AR) has a long medicinal history. Astragalus polysaccharide (APS), the natural macromolecule that exhibits immune regulatory, anti-inflammatory, anti-tumor, and other pharmacological activities, is an important active ingredient extracted from AR. Recently, APS has been increasingly used in cancer therapy owing to its anti-tumor ability as it prevents the progression of prostate, liver, cervical, ovarian, and non-small-cell lung cancer by suppressing tumor cell growth and invasion and enhancing apoptosis. In addition, APS enhances the sensitivity of tumors to antineoplastic agents and improves the body's immunity. This macromolecule has prospects for broad application in tumor therapy through various pathways. In this article, we present the latest progress in the research on the anti-tumor effects of APS and its underlying mechanisms, aiming to provide novel theoretical support and reference for its use in cancer therapy.

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

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

Influence of Curvature on Cell Motility and Morphology during Cancer Migration in Confined Microchannels

Microchannels often serve as highways for cancer migration, and their topology largely determines the migration efficiency. Curvature, a topological parameter in biological systems, has recently been reported to be efficient in guiding cell polarization and migration. Curvature varies widely along curved microchannels, while its influence on cell migration remains elusive. Here, we recapitulated the curved microchannels, as observed in clinical tumor tissues with hydrogels, and studied how cancer cells respond to curvature. We found that cells bend more significantly in a larger curvature and exhibit less spreading as well as lower motility. The underlying mechanism is probably based on the hindrance of the movement of cytoskeletal molecules at the curved microchannel walls. Collectively, our results demonstrated that the accelerated actin retrograde flow rate under local curvature has an effective negative regulation on cell motility and morphology, leading to shortened and bent cell morphologies as well as hampered cell migration efficiency.

Microtubule control of migration: Coordination in confinement

The microtubule cytoskeleton has a well-established, instrumental role in coordinating cell migration. Decades of research has focused on understanding how microtubules couple intracellular trafficking with cortical targeting and spatial organization of signaling to facilitate locomotion. Movement in physically challenging environments requires coordination of forces generated by the actin cytoskeleton to drive cell shape changes, with microtubules acting to spatially regulate contractility. Recent work has demonstrated that the mechanical properties of microtubules are adaptive to stress, leading to a new understanding of their roles in cell migration. Herein we review new developments in how microtubules sense and adapt to changes in the physical properties of their environment during migration. We frame our discussion around our current understanding of how microtubules target cell-matrix adhesions, and their role in the spatiotemporal coordination of signaling to form mechano feedback loops. We expand on how these mechanisms may influence cell morphology in confined three-dimensional settings, and the importance of locally tuning the mechanical stability of polymers in response to mechanical cues. Finally, we discuss new roles for Golgi-derived microtubules in mechanosensing, and how preferential motor use may influence polymer stability to resist the physical constraints cells experience in confined environments.

Cationic solid lipid nanoparticles (SLN) complexed with plasmid DNA enhance prostate cancer cells (PC-3) migration

Nanotechnology applications in biomedicine have increased in recent decades, primarily as therapeutic agents, drugs, and gene delivery systems. Among the nanoparticles used in medicine, we highlight cationic solid lipid nanoparticles (SLN). Given their nontoxic properties, much research has focused on the beneficial effects of SLN for drug or gene delivery system. However, little attention has been paid to the adverse impacts of SLN on the cellular environment, particularly their influence on intracellular signaling pathways. In this work, we investigate the effects triggered by cationic SLN on human prostate non-tumor cells (PNT1A) and tumor cells (PC-3). Our results demonstrate that cationic SLN enhances the migration of PC-3 prostate cancer cells but not PNT1A non-tumor prostate cells, an unexpected and unprecedented development. Furthermore, we observed that the enhanced cell migration velocity is a concentration-dependent and nanoparticle-dependent effect, and not related to any individual nanoparticle component. Moreover, cationic SLN increased vimentin expression (p < 0.05) but SLN did not affect Smad2 nuclear translocation. Meanwhile, EMT-related (epithelial-to-mesenchymal transition) proteins, such as ZEB1, underwent nuclear translocation when treated with cationic SLN, thereby affecting PC-3 cell motility through ZEB1 and vimentin modulation. From a therapeutic perspective, cationic SLN could potentially worsen a patient's condition if these results were reproduced in vivo. Understanding the in vitro molecular mechanisms triggered by nanomaterials and their implications for cell function is crucial for defining their safe and effective use.

Cytoskeleton remodeling induced by SMYD2 methyltransferase drives breast cancer metastasis

Malignant forms of breast cancer refractory to existing therapies remain a major unmet health issue, primarily due to metastatic spread. A better understanding of the mechanisms at play will provide better insights for alternative treatments to prevent breast cancer cell dispersion. Here, we identify the lysine methyltransferase SMYD2 as a clinically actionable master regulator of breast cancer metastasis. While SMYD2 is overexpressed in aggressive breast cancers, we notice that it is not required for primary tumor growth. However, mammary-epithelium specific SMYD2 ablation increases mouse overall survival by blocking the primary tumor cell ability to metastasize. Mechanistically, we identify BCAR3 as a genuine physiological substrate of SMYD2 in breast cancer cells. BCAR3 monomethylated at lysine K334 (K334me1) is recognized by a novel methyl-binding domain present in FMNLs proteins. These actin cytoskeleton regulators are recruited at the cell edges by the SMYD2 methylation signaling and modulate lamellipodia properties. Breast cancer cells with impaired BCAR3 methylation lose migration and invasiveness capacity in vitro and are ineffective in promoting metastases in vivo. Remarkably, SMYD2 pharmacologic inhibition efficiently impairs the metastatic spread of breast cancer cells, PDX and aggressive mammary tumors from genetically engineered mice. This study provides a rationale for innovative therapeutic prevention of malignant breast cancer metastatic progression by targeting the SMYD2-BCAR3-FMNL axis.

Coordinated in confined migration: crosstalk between the nucleus and ion channel-mediated mechanosensation

Cell surface and intracellular mechanosensors enable cells to perceive different geometric, topographical, and physical cues. Mechanosensitive ion channels (MICs) localized at the cell surface and on the nuclear envelope (NE) are among the first to sense and transduce these signals. Beyond compartmentalizing the genome of the cell and its transcription, the nucleus also serves as a mechanical gauge of different physical and topographical features of the tissue microenvironment. In this review, we delve into the intricate mechanisms by which the nucleus and different ion channels regulate cell migration in confinement. We review evidence suggesting an interplay between macromolecular nuclear-cytoplasmic transport (NCT) and ionic transport across the cell membrane during confined migration. We also discuss the roles of the nucleus and ion channel-mediated mechanosensation, whether acting independently or in tandem, in orchestrating migratory mechanoresponses. Understanding nuclear and ion channel sensing, and their crosstalk, is critical to advancing our knowledge of cell migration in health and disease.

Unveiling breast cancer metastasis through an advanced X-ray imaging approach

Breast cancer is a significant global health burden, causing a substantial number of deaths. Systemic metastatic tumour cell dissemination is a major cause of poor outcomes. Understanding the mechanisms underlying metastasis is crucial for effective interventions. Changes in the extracellular matrix play a pivotal role in breast cancer metastasis. In this work, we present an advanced multimodal X-ray computed tomography, by combining Small-angle X-ray Scattering Tensor Tomography (SAXS-TT) and X-ray Fluorescence Computed Tomography (XRF-CT). This approach likely brings out valuable information about the breast cancer metastasis cascade. Initial results from its application on a breast cancer specimen reveal the collective influence of key molecules in the metastatic mechanism, identifying a strong correlation between zinc accumulation (associated with matrix metalloproteinases MMPs) and highly oriented collagen. MMPs trigger collagen alignment, facilitating breast cancer cell intravasation, while iron accumulation, linked to angiogenesis and vascular endothelial growth factor VEGF, supports cell proliferation and metastasis. Therefore, these findings highlight the potential of the advanced multimodal X-ray computed tomography approach and pave the way for in-depth investigation of breast cancer metastasis, which may guide the development of novel therapeutic approaches and enable personalised treatment strategies, ultimately improving patient outcomes in breast cancer management.

Cytoplasmic accumulation and plasma membrane association of anillin and Ect2 promote confined migration and invasion

Cells migrating in confinement experience mechanical challenges whose consequences on cell migration machinery remain only partially understood. Here, we demonstrate that a pool of the cytokinesis regulatory protein anillin is retained during interphase in the cytoplasm of different cell types. Confinement induces recruitment of cytoplasmic anillin to plasma membrane at the poles of migrating cells, which is further enhanced upon nuclear envelope (NE) rupture(s). Rupture events also enable the cytoplasmic egress of predominantly nuclear RhoGEF Ect2. Anillin and Ect2 redistributions scale with microenvironmental stiffness and confinement, and are observed in confined cells in vitro and in invading tumor cells in vivo. Anillin, which binds actomyosin at the cell poles, and Ect2, which activates RhoA, cooperate additively to promote myosin II contractility, and promote efficient invasion and extravasation. Overall, our work provides a mechanistic understanding of how cytokinesis regulators mediate RhoA/ROCK/myosin II-dependent mechanoadaptation during confined migration and invasive cancer progression.

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.

Bulky glycocalyx shields cancer cells from invasion-associated stresses

The glycocalyx-that forms a protective barrier around cells-has been implicated in cancer cell proliferation, survival, and metastasis. However, its role in maintaining the integrity of DNA/nucleus during migration through dense matrices remains unexplored. In this study, we address this question by first documenting heterogeneity in glycocalyx expression in highly invasive MDA-MB-231 breast cancer cells, and establishing a negative correlation between cell size and glycocalyx levels. Next, we set-up transwell migration through 3 µm pores, to isolate two distinct sub-populations and to show that the early migrating cell sub-population possesses a bulkier glycocalyx and undergoes less DNA damage and nuclear rupture, assessed using γH2AX foci formation and nuclear/cytoplasmic distribution of Ku70/80. Interestingly, enzymatic removal of glycocalyx led to disintegration of the nuclear membrane indicated by increased cytoplasmic localisation of Ku70/80, increased nuclear blebbing and reduction in nuclear area. Together, these results illustrate an inverse association between bulkiness of the glycocalyx and nuclear stresses, and highlights the mechanical role of the glycocalyx in shielding migration associated stresses.

Impairment of Assembly of the Vimentin Intermediate Filaments Leads to Suppression of Formation and Maturation of Focal Contacts and Alteration of the Type of Cellular Protrusions

Cell migration is largely determined by the type of protrusions formed by the cell. Mesenchymal migration is accomplished by formation of lamellipodia and/or filopodia, while amoeboid migration is based on bleb formation. Changing of migrational conditions can lead to alteration in the character of cell movement. For example, inhibition of the Arp2/3-dependent actin polymerization by the CK-666 inhibitor leads to transition from mesenchymal to amoeboid motility mode. Ability of the cells to switch from one type of motility to another is called migratory plasticity. Cellular mechanisms regulating migratory plasticity are poorly understood. One of the factors determining the possibility of migratory plasticity may be the presence and/or organization of vimentin intermediate filaments (VIFs). To investigate whether organization of the VIF network affects the ability of fibroblasts to form membrane blebs, we used rat embryo fibroblasts REF52 with normal VIF organization, fibroblasts with vimentin knockout (REF-/-), and fibroblasts with mutation inhibiting assembly of the full-length VIFs (REF117). Blebs formation was induced by treatment of cells with CK-666. Vimentin knockout did not lead to statistically significant increase in the number of cells with blebs. The fibroblasts with short fragments of vimentin demonstrate the significant increase in number of cells forming blebs both spontaneously and in the presence of CK-666. Disruption of the VIF organization did not lead to the significant changes in the microtubules network or the level of myosin light chain phosphorylation, but caused significant reduction in the focal contact system. The most pronounced and statistically significant decrease in both size and number of focal adhesions were observed in the REF117 cells. We believe that regulation of the membrane blebbing by VIFs is mediated by their effect on the focal adhesion system. Analysis of migration of fibroblasts with different organization of VIFs in a three-dimensional collagen gel showed that organization of VIFs determines the type of cell protrusions, which, in turn, determines the character of cell movement. A novel role of VIFs as a regulator of membrane blebbing, essential for manifestation of the migratory plasticity, is shown.

Implantable SDF-1α-loaded silk fibroin hyaluronic acid aerogel sponges as an instructive component of the glioblastoma ecosystem: Between chemoattraction and tumor shaping into resection cavities

In view of inevitable recurrences despite resection, glioblastoma (GB) is still an unmet clinical need. Dealing with the stromal-cell derived factor 1-alpha (SDF-1α)/CXCR4 axis as a hallmark of infiltrative GB tumors and with the resection cavity situation, the present study described the effects and relevance of a new engineered micro-nanostructured SF-HA-Hep aerogel sponges, made of silk fibroin (SF), hyaluronic acid (HA) and heparin (Hep) and loaded with SDF-1α, to interfere with the GB ecosystem and residual GB cells, attracting and confining them in a controlled area before elimination. 70 µm-pore sponges were designed as an implantable scaffold to trap GB cells. They presented shape memory and fit brain cavities. Histological results after implantation in brain immunocompetent Fischer rats revealed that SF-HA-Hep sponges are well tolerated for more than 3 months while moderately and reversibly colonized by immuno-inflammatory cells. The use of human U87MG GB cells overexpressing the CXCR4 receptor (U87MG-CXCR4+) and responding to SDF-1α allowed demonstrating directional GB cell attraction and colonization of the device in vitro and in vivo in orthotopic resection cavities in Nude rats. Not modifying global survival, aerogel sponge implantation strongly shaped U87MG-CXCR4+ tumors in cavities in contrast to random infiltrative growth in controls. Overall, those results support the interest of SF-HA-Hep sponges as modifiers of the GB ecosystem dynamics acting as "cell meeting rooms" and biocompatible niches whose properties deserve to be considered toward the development of new clinical procedures. STATEMENT OF SIGNIFICANCE: Brain tumor glioblastoma (GB) is one of the worst unmet clinical needs. To prevent the relapse in the resection cavity situation, new implantable biopolymer aerogel sponges loaded with a chemoattractant molecule were designed and preclinically tested as a prototype targeting the interaction between the initial tumor location and its attraction by the peritumoral environment. While not modifying global survival, biocompatible SDF1-loaded hyaluronic acid and silk fibroin sponges induce directional GB cell attraction and colonization in vitro and in rats in vivo. Interestingly, they strongly shaped GB tumors in contrast to random infiltrative growth in controls. These results provide original findings on application of exogenous engineered niches that shape tumors and serve as cell meeting rooms for further clinical developments.

Microfluidic devices for precise measurements of cell directionality reveal a role for glutamine during cell migration

Cancer cells that migrate from tumors into surrounding tissues are responsible for cancer dissemination through the body. Microfluidic devices have been instrumental in discovering unexpected features of cancer cell migration, including the migration in self-generated gradients and the contributions of cell-cell contact during collective migration. Here, we design microfluidic channels with five successive bifurcations to characterize the directionality of cancer cell migration with high precision. We uncover an unexpected role for glutamine in epithelial cancer cell orientation, which could be replaced by alfa-keto glutarate but not glucose.

Confinement primes cells for faster migration by polarizing active mitochondria

Mechanical cues in the tumor microenvironment interplay with internal cellular processes to control cancer cell migration. Microscale pores present in tumor tissue confer varying degrees of confinement on migrating cells, increasing matrix contact and inducing cytoskeletal rearrangement. Previously, we observed that increased collagen matrix contact significantly increased cell migration speed and cell-induced strains within the matrix. However, the effects of this confinement on future cell migration are not fully understood. Here, we use a collagen microtrack platform to determine the effect of confinement on priming MDA-MB-231 cancer cells for fast migration. We show that migration through a confined track results in increased speed and accumulation of migratory machinery, including actin and active mitochondria, in the front of migrating breast cancer cells. By designing microtracks that allow cells to first navigate a region of high confinement, then a region of low confinement, we assessed whether migration in high confinement changes future migratory behavior. Indeed, cells maintain their speed attained in high confinement even after exiting to a region of low confinement, indicating that cells maintain memory of previous matrix cues to fuel fast migration. Active mitochondria maintain their location at the front of the cell even after cells leave high confinement. Furthermore, knocking out vinculin to disrupt focal adhesions disrupts active mitochondrial localization and disrupts the fast migration seen upon release from confinement. Together, these data suggest that active mitochondrial localization in confinement may facilitate fast migration post-confinement. By better understanding how confinement contributes to future cancer cell migration, we can identify potential therapeutic targets to inhibit breast cancer metastasis.

Subcellular mechano-regulation of cell migration in confined extracellular microenvironment

Cell migration is a highly coordinated cellular event that determines diverse physiological and pathological processes in which the continuous interaction of a migrating cell with neighboring cells or the extracellular matrix is regulated by the physical setting of the extracellular microenvironment. In confined spaces, cell migration occurs differently compared to unconfined open spaces owing to the additional forces that limit cell motility, which create a driving bias for cells to invade the confined space, resulting in a distinct cell motility process compared to what is expected in open spaces. Moreover, cells in confined environments can be subjected to elevated mechanical compression, which causes physical stimuli and activates the damage repair cycle in the cell, including the DNA in the nucleus. Although cells have a self-restoring system to repair damage from the cell membrane to the genetic components of the nucleus, this process may result in genetic and/or epigenetic alterations that can increase the risk of the progression of diverse diseases, such as cancer and immune disorders. Furthermore, there has been a shift in the paradigm of bioengineering from the development of new biomaterials to controlling biophysical cues and fine-tuning cell behaviors to cure damaged/diseased tissues. The external physical cues perceived by cells are transduced along the mechanosensitive machinery, which is further channeled into the nucleus through subcellular molecular linkages of the nucleoskeleton and cytoskeleton or the biochemical translocation of transcription factors. Thus, external cues can directly or indirectly regulate genetic transcriptional processes and nuclear mechanics, ultimately determining cell fate. In this review, we discuss the importance of the biophysical cues, response mechanisms, and mechanical models of cell migration in confined environments. We also discuss the effect of force-dependent deformation of subcellular components, specifically focusing on subnuclear organelles, such as nuclear membranes and chromosomal organization. This review will provide a biophysical perspective on cancer progression and metastasis as well as abnormal cellular proliferation.

3D Volumetric Mechanosensation of MCF7 Breast Cancer Spheroids in a Linear Stiffness Gradient GelAGE

The tumor microenvironment presents spatiotemporal shifts in biomechanical properties with cancer progression. Hydrogel biomaterials like GelAGE offer the stiffness tuneability to recapitulate dynamic changes in tumor tissues by altering photo-energy exposures. Here, a tuneable hydrogel with spatiotemporal control of stiffness and mesh-network is developed. The volume of MCF7 spheroids encapsulated in a linear stiffness gradient demonstrates an inverse relationship with stiffness (p < 0.0001). As spheroids are exposed to increased crosslinking (stiffer) and greater mechanical confinement, spheroid stiffness increases. Protein expression (TRPV4, β1 integrin, E-cadherin, and F-actin) decreases with increasing stiffness while showing strong correlations to spheroid volume (r2  > 0.9). To further investigate the role of volume, MCF7 spheroids are grown in a soft matrix for 5 days prior to a second polymerisation which presents a stiffness gradient to equally expanded spheroids. Despite being exposed to variable stiffness, these spheroids show even protein expression, confirming volume as a key regulator. Overall, this work showcases the versatility of GelAGE and demonstrates volume expansion as a key regulator of 3D mechanosensation in MCF7 breast cancer spheroids. This platform has the potential to further investigation into the role of stiffness and dimensionality in 3D spheroid culture for other types of cancers and diseases.

Dynein-Powered Cell Locomotion Guides Metastasis of Breast Cancer

The principal cause of death in cancer patients is metastasis, which remains an unresolved problem. Conventionally, metastatic dissemination is linked to actomyosin-driven cell locomotion. However, the locomotion of cancer cells often does not strictly line up with the measured actomyosin forces. Here, a complementary mechanism of metastatic locomotion powered by dynein-generated forces is identified. These forces arise within a non-stretchable microtubule network and drive persistent contact guidance of migrating cancer cells along the biomimetic collagen fibers. It is also shown that the dynein-powered locomotion becomes indispensable during invasive 3D migration within a tissue-like luminal network formed by spatially confining granular hydrogel scaffolds (GHS) made up of microscale hydrogel particles (microgels). These results indicate that the complementary motricity mediated by dynein is always necessary and, in certain instances, sufficient for disseminating metastatic breast cancer cells. These findings advance the fundamental understanding of cell locomotion mechanisms and expand the spectrum of clinical targets against metastasis.

Gelatin-based 3D biomimetic scaffolds platform potentiates culture of cancer stem cells in esophageal squamous cell carcinoma

Cancer stem cells (CSCs) are crucial for tumorigenesis, metastasis, and therapy resistance in esophageal squamous cell carcinoma (ESCC). To further elucidate the mechanism underlying characteristics of CSCs and develop CSCs-targeted therapy, an efficient culture system that could expand and maintain CSCs is needed. CSCs reside in a complex tumor microenvironment, and three-dimensional (3D) culture systems of biomimetic scaffolds are expected to better support the growth of CSCs by recapitulating the biophysical properties of the extracellular matrix (ECM). Here, we established gelatin-based 3D biomimetic scaffolds mimicking the stiffness and collagen content of ESCC, which could enrich ESCC CSCs efficiently. Biological changes of ESCC cells laden in scaffolds with three different viscoelasticity emulating physiological stiffness of esophageal tissues were thoroughly investigated in varied aspects such as cell morphology, viability, cell phenotype markers, and transcriptomic profiling. The results demonstrated the priming effects of viscoelasticity on the stemness of ESCC. The highly viscous scaffolds (G': 6-403 Pa; G'': 2-75 Pa) better supported the enrichment of ESCC CSCs, and the TGF-beta signaling pathway might be involved in regulating the stemness of ESCC cells. Compared to two-dimensional (2D) cultures, highly viscous scaffolds significantly promoted the clonal expansion of ESCC cells in vitro and tumor formation ability in vivo. Our findings highlight the crucial role of biomaterials' viscoelasticity for the 3D culture of ESCC CSCs in vitro, and this newly-established culture system represents a valuable platform to support their growth, which could facilitate the CSCs-targeted therapy in the future.

SPAK-dependent cotransporter activity mediates capillary adhesion and pressure during glioblastoma migration in confined spaces

The invasive potential of glioblastoma cells is attributed to large changes in pressure and volume, driven by diverse elements, including the cytoskeleton and ion cotransporters.  However, how the cell actuates changes in pressure and volume in confinement, and how these changes contribute to invasive motion is unclear. Here, we inhibited SPAK activity, with known impacts on the cytoskeleton and cotransporter activity and explored its role on the migration of glioblastoma cells in confining microchannels to model invasive spread through brain tissue. First, we found that confinement altered cell shape, inducing a transition in morphology that resembled droplet interactions with a capillary vessel, from "wetting" (more adherent) at low confinement, to "nonwetting" (less adherent) at high confinement. This transition was marked by a change from negative to positive pressure by the cells to the confining walls, and an increase in migration speed. Second, we found that the SPAK pathway impacted the migration speed in different ways dependent upon the extent of wetting. For nonwetting cells, SPAK inhibition increased cell-surface tension and cotransporter activity. By contrast, for wetting cells, it also reduced myosin II and YAP phosphorylation. In both cases, membrane-to-cortex attachment is dramatically reduced. Thus, our results suggest that SPAK inhibition differentially coordinates cotransporter and cytoskeleton-induced forces, to impact glioblastoma migration depending on the extent of confinement.

Microfluidic single-cell migration chip reveals insights into the impact of extracellular matrices on cell movement

Cell migration is a complex process that plays a crucial role in normal physiology and pathologies such as cancer, autoimmune diseases, and mental disorders. Conventional cell migration assays face limitations in tracking a large number of individual migrating cells. To address this challenge, we have developed a high-throughput microfluidic cell migration chip, which seamlessly integrates robotic liquid handling and computer vision to swiftly monitor the movement of 3200 individual cells, providing unparalleled single-cell resolution for discerning distinct behaviors of the fast-moving cell population. This study focuses on the ECM's role in regulating cellular migration, utilizing this cutting-edge microfluidic technology to investigate the impact of ten different ECMs on triple-negative breast cancer cell lines. We found that collagen IV, collagen III, and collagen I coatings were the top enhancers of cell movement. Combining these ECMs increased cell motility, but the effect was sub-additive. Furthermore, we examined 87 compounds and found that while some compounds inhibited migration on all substrates, significantly distinct effects on differently coated substrates were observed, underscoring the importance of considering ECM coating. We also utilized cells expressing a fluorescent actin reporter and observed distinct actin structures in ECM-interacting cells. ScRNA-Seq analysis revealed that ECM coatings induced EMT and enhanced cell migration. Finally, we identified genes that were particularly up-regulated by collagen IV and the selective inhibitors successfully blocked cell migration on collagen IV. Overall, the study provides insights into the impact of various ECMs on cell migration and dynamics of cell movement with implications for developing therapeutic strategies to combat diseases related to cell motility.

Calcein-Modified CeO2 for Intracellular ROS Detection: Mechanisms of Action and Cytotoxicity Analysis In Vitro

Cerium oxide nanoparticles (CeO2 NPs) are metal-oxide-based nanozymes with unique reactive oxygen species (ROS) scavenging abilities. Here, we studied new CeO2 NPs modified with calcein (CeO2-calcein) as an intracellular ROS inactivation/visualization theranostic agent. The molecular mechanisms of the CeO2-calcein intracellular activity, allowing for the direct monitoring of ROS inactivation in living cells, were studied. CeO2-calcein was taken up by both normal (human mesenchymal stem cells, hMSc) and cancer (human osteosarcoma, MNNG/Hos cell line) cells, and was easily decomposed via endogenous or exogenous ROS, releasing brightly fluorescent calcein, which could be quantitatively detected using fluorescence microscopy. It was shown that the CeO2-calcein has selective cytotoxicity, inducing the death of human osteosarcoma cells and modulating the expression of key genes responsible for cell redox status as well as proliferative and migration activity. Such cerium-based theranostic agents can be used in various biomedical applications.

Defining Integrin Tension Required for Chemotaxis of Metastatic Breast Cancer Cells in Confinement

Cancer metastasis is affected by chemical factors and physical cues. From cell adhesion to migration, mechanical tension applied to integrin expresses on the cell membrane and physical confinement significantly regulates cancer cell behaviors. Despite the physical interplay between integrins in cells and ligands in the tumor microenvironment, quantitative analysis of integrin tension during cancer cell migration in microconfined spaces remains elusive owing to the limited experimental tools. Herein, a platform termed microconfinement tension gauge tether to monitor spatial integrin tension with single-molecule precision by analyzing the epithelial-growth-factor-induced chemotaxis of metastatic human breast cancer cells in microfluidic channels is developed. The results reveal that the metastatic cancer cells exert the strongest integrin tension in the range of 54-100 pN at the leading edges of cells during chemokinetic migration on a planar surface, while the cells exert the strongest integrin tension exceeding 100 pN at the cell rear when entering microconfinement. Further analysis demonstrates that cells undergo mesenchymal migration under high integrin tension and less confinement, which is converted to amoeboid migration under low integrin tension or high confinement. In summary, the results identify a basic mechanism underlying the mechanical interactions between integrin tension and microenvironment that determines cancer invasion and metastasis.

Matrix Anisotropy Promotes a Transition of Collective to Disseminated Cell Migration via a Collective Vortex Motion

Cells detached and disseminated away from collectively migrating cells are frequently found during tumor invasion at the invasion front, where extracellular matrix (ECM) fibers are parallel to the cell migration direction. However, it remains unclear how anisotropic topography promotes the transition of collective to disseminated cell migration. This study applies a collective cell migration model with and without 800 nm wide aligned nanogrooves parallel, perpendicular, or diagonal to the cell migration direction. After 120 hour migration, MCF7-GFP-H2B-mCherry breast cancer cells display more disseminated cells at the migration front on parallel topography than on other topographies. Notably, a fluid-like collective motion with high vorticity is enhanced at the migration front on parallel topography. Furthermore, high vorticity but not velocity is correlated with disseminated cell numbers on parallel topography. Enhanced collective vortex motion colocalizes with cell monolayer defects where cells extend protrusions into the free space, suggesting that topography-driven cell crawling for defect closure promotes the collective vortex motion. In addition, elongated cell morphology and frequent protrusions induced by topography may further contribute to the collective vortex motion. Overall, a high-vorticity collective motion at the migration front promoted by parallel topography suggests a cause of the transition of collective to disseminated cell migration.