LIM1863 is useful to explore collective cancer cell migration,and the group of heterogeneous cells undergoing collective migration behaves like a supracellular unit

Collective cancer cell migration(CCCM)and epithelial-to-mesenchymal transition(EMT)play key roles in metastasis.This study reports that the colorectal carcinoma cell line LIM1863 is useful for the study of CCCM and EMT.Methods:Hematoxylin and eosin staining,scanning electron microscopy,transmission electron microscopy,and western blot analysis were performed.Results:LIM1863 automatically grew as spheroids in suspension and had important typical epithelial properties,including several layers of cells arranged around a central lumen,apical-basal polarity,and types of cell-cell junctions.Treatment with a combination of both TGF beta 1 and TNF alpha induced definite and distinct EMT,a spheroid changing phenotype to form a monolayer high-confluent patch without lumen,without polarity.Spontaneous CCCM occurred in spheroids.Flat EMT cells adhered to the base of a dish,exhibited persistent movement as a cluster of cells,and then shed,resulting in a cluster.All cells from one cluster undergoing CCCM died.Otherwise,all cells undergoing EMT disappeared and almost all cells located in the cell reservoir survived and proliferated.Conclusion:LIM1863 is an excellent cell line to study CCCM and EMT.The group of heterogeneous cells undergoing CCCM behaves like a supracellular unit.

Geometric regulation of collective cell tangential ordering migration

Collective cell migration is a coordinated movement of multi-cell systems essential for various processes throughout life.The collective motions often occur under spatial restrictions,hallmarked by the collective rotation of epithelial cells confined in circular substrates.Here,we aim to explore how geometric shapes of confinement regulate this collective cell movement.We develop quantitative methods for cell velocity orientation analysis,and find that boundary cells exhibit stronger tangential ordering migration than inner cells in circular pattern.Furthermore,decreased tangential ordering movement capability of collective cells in triangular and square patterns are observed,due to the disturbance of cell motion at unsmooth corners of these patterns.On the other hand,the collective cell rotation is slightly affected by a convex defect of the circular pattern,while almost hindered with a concave defect,also resulting from different smoothness features of their boundaries.Numerical simulations employing cell Potts model well reproduce and extend experimental observations.Together,our results highlight the importance of boundary smoothness in the regulation of collective cell tangential ordering migration.

Computational Study of Collective Cell Migration By Meshfree Method

The collective cell migration behavior on a substrate was studied using RKPM meshfree method.The cells were modeled as nematic liquid crystal with hyperelastic cell nucleus.The cell-substrate and cell-cell interactions were modeled by coarse-grained potential forces.Through this study,the pulling and pushing phenomenon during collective cell migration process was observed and it was found that the individual cell mobility significantly influenced the collective cell migratory behavior.More self-propelled cells are in the system along the same direction,the faster the collective group migrates toward coordinated direction.The parametric study on cell-cell adhesion strength indicated that as the adhesion strength increases,the collective cell migration speed increases.It also showed that the mechanical stress in leader cell is higher than stress in follower cells.

Cell mechanics and energetic costs of collective cell migration under confined microchannels

Mechanical force between cells relates to many biological processes of cell development.The cellular collective migration comes from cell-cell cooperation,and studying the intercellular mechanical properties helps elucidate collective cell migration.Herein,we studied cell-cell junctions,intercellular tensile force and the related cellular energetic costs in confined microchannels.Using the intercellular force sensor,we found that cells adapt to different confinement environments by regulating intercellular force,and thereby the relationship between collective cell migration and cell-cell junction were verified.Through the observation of cell orientation,actomyosin contractility,energetic costs,and glucose uptake,we can make a reasonable explanation of cell-force driven migration in different confined environments.Under highly confined conditions,the intercellular force and energetic costs are greater,and the cell orientation is more orderly.The collective migration behavior in confined spaces is closely related to the intercellular force and energetic costs,which is helpful to understand the collective migration behaviors in various confined spaces.

Dynamics along the epithelial-cancer biointerface:Hidden system complexities

The biointerface dynamics influence any cancer spreading through the epithelium since it is documented in the early stages some malignancies(like epithelial cancer).The altered rearrangement of epithelial cells has an impact on the development of cancer.Therefore,it is necessary to comprehend the underlying biological and physical mechanisms of this biointerface dynamics for early suppression of cancer.While the biological mechanisms include cell signaling and gene expression,the physical mechanisms are several physical parameters such as the epithelial-cancer interfacial tension,epithelial surface tension,and compressive stress accumulated within the epithelium.Although the segregation of epithelia-cancer co-cultured systems was widely investigated,the role of these physical parameters in cell reorganization is still not fully recognized.Hence,this review is focused on clarifying the role that some physical parameters have during cell reorganization within the epithelial cell clusters and cancer spread within co-cultured spheroids.We have applied the developed biophysical model to point out the inter-relations among physical parameters that influence cell reorganization within epithelial-cancer co-cultured systems.The main results of this theoretical consideration have been assessed by integrating the biophysical model with biological and bio-mechanical experiments from the available literature.The epithelial-cancer interfacial tension leads to the reduction of the biointerface area,which leads to an increase in the compressive residual stress within the epithelial clusters depending on the viscoelasticity of the epithelial subpopulation.This stress impacts epithelial rearrangement and the dynamics along the biointerface by influencing the epithelial surface tension and epithelial-cancer interfacial tension.Further,the interrelation between the epithelial surface tension and epithelial-cancer interfacial tension influences the spread of cancer cells.

Surface activity of cancer cells:The fusion of two cell aggregates

A key feature that distinguishes cancer cells from all other cells is their capability to spread throughout the body.Although how cancer cells collectively migrate by following molecular rules which influence the state of cell-cell adhesion contacts has been comprehensively formulated,the impact of physical interactions on cell spreading remains less understood.Cumulative effects of physical interactions exist as the interplay between various physical parameters such as(1)tissue surface tension,(2)viscoelasticity caused by collective cell migration,and(3)solid stress accumulated in the cell aggregate core region.This review aims to point out the role of these physical parameters in cancer cell spreading by considering and comparing the rearrangement of various mono-cultured cancer and epithelial model systems such as the fusion of two cell aggregates.While epithelial cells undergo volumetric cell rearrangement driven by the tissue surface tension,which directs cell movement from the surface to the core region of two-aggregate systems,cancer cells rather perform surface cell rearrangement.Cancer cells migrate toward the surface of the two-aggregate system driven by the solid stress while the surface tension is significantly reduced.The solid stress,accumulated in the core region of the two-aggregate system,is capable of suppressing the movement of epithelial cells that can undergo the jamming state transition;however,this stress enhances the movement of cancer cells.We have focused here on the multi-scale rheological modeling approaches that aimed at reproducing and understanding these biological systems.

Collective cell migration: Implications for wound healing and cancer invasion

During embryonic morphogenesis, wound repair and cancer invasion, cells often migrate collectively via tight cell-cell junctions, a process named collective migration. During such migration, cells move as coherent groups, large cell sheets, strands or tubes rather than individually. One unexpected finding regarding collective cell migration is that being a "multicellular structure" enables cells to better respond to chemical and physical cues, when compared with isolated cells. This is important because epithelial cells heal wounds via the migration of large sheets of cells with tight intercellular connections. Recent studies have gained some mechanistic insights that will benefit the clinical understanding of wound healing in general. In this review, we will briefly introduce the role of collective cell migration in wound healing, regeneration and cancer invasion and discuss its underlying mechanisms as well as implications for wound healing.

CD9 negatively regulates collective electrotaxis of the epidermal monolayer by controlling and coordinating the polarization of leader cells

Background:Endogenous electric fields(EFs)play an essential role in guiding the coordinated collective migration of epidermal cells to the wound centre during wound healing.Although polarization of leadercells is essential for collective migration,the signal mechanisms responsible for the EF-induced polarization of leader cells under electrotactic collective migration remain unclear.This study aims to determine how the leader cells are polarized and coordinated during EF-guided collective migration of epidermal cell sheets.Methods:Collective migration of the human epidermal monolayer(human immortalized ker-atinocytes HaCaT)under EFs was observed via time-lapse microscopy.The involvement of tetraspanin-29(CD9)in EF-induced fibrous actin(F-actin)polarization of leader cells as well as electrotactic migration of the epidermal monolayer was evaluated by genetic manipulation.Blocking,rescue and co-culture experiments were conducted to explore the downstream signalling of CD9.Results:EFs guided the coordinated collective migration of the epithelial monolayer to the anode,with dynamic formation of pseudopodia in leader cells at the front edge of the monolayer along the direction of migration.F-actin polarization,as expected,played an essential role in pseudopod formation in leader cells under EFs.By confocal microscopy,we found that CD9 was colocalized with F-actin on the cell surface and was particularly downregulated in leader cells by EFs.Interestingly,genetic overexpression of CD9 abolished EF-induced F-actin polarization in leader cells as well as collective migration in the epidermal monolayer.Mechanistically,CD9 determined the polarization of F-actin in leader cells by downregulating a disintegrin and metalloprotease 17/heparin-binding epidermal growth factor-like growth factor/epidermal growth factor receptor(ADAM17/HB-EGF/EGFR)signalling.The abolished polarization of leader cells due to CD9 overex-pression could be restored in a co-culture monolayer where normal cells and CD9-overexpressing cells were mixed;however,this restoration was eliminated again by the addition of the HB-EGF-neutralizing antibody.Conclusion:CD9 functions as a key regulator in the EF-guided collective migration of the epidermal monolayer by controlling and coordinating the polarization of leader cells through ADAM17/HB-EGF/EGFR signalling.

Engineering subcellular-patterned biointerfaces to regulate the surface wetting of multicellular spheroids

Studying the wetting behaviors of multicellular spheroids is crucial in the fields of embryo implantation, cancer propagation, and tissue repair. Existing strategies for controlling the wetting of multicellular spheroids mainly focus on surface chemistry and substrate rigidity. Although topography is another important feature in the biological micro-environment, its effect on multicellular spheroid wetting has seldom been explored. In this study, the influence of topography on the surface wetting of multicellular spheroids was investigated using subcellular- patterned opal films with controllable colloidal particle diameters （from 200 to 1,500 nm）. The wetting of hepatoma carcinoma cellular （Hep G2） spheroids was impaired on opal films compared with that on flat substrates, and the wetting rate decreased as colloidal particle diameter increased. The decrement reached 48.5% when the colloidal particle diameter was 1,500 nm. The subcellular-patterned topography in opal films drastically reduced the cellular mobility in precursor films, especially the frontier cells in the leading edge. The frontier cells failed to form mature focal adhesions and stress fibers on micro-patterned opal films. This was due to gaps between colloidal particles leaving adhesion vacancies, causing weak cell-substrate adhesion and consequent retarded migration of Hep G2 spheroids. Our study manifests the inhibiting effects of subcellular-patterned topography on the wetting behaviors of multicellular spheroids, providing new insight into tissue wetting-associated treatments and biomaterial design.