Contact Inhibition Of Locomotion Research Articles

Nm23-H1 regulates contact inhibition of locomotion which is affected by ephrin-B1

Contact inhibition of locomotion (CIL) is the process by which cells stop the continual migration in the same direction after collision with another cell. Highly invasive malignant cells exhibit diminished CIL when they contact stromal cells, which allows invasion of the tissue by tumors. We show that Nm23-H1 is essential for the suppression of Rac1 through inactivation of Tiam1 at the sites of cell-cell contact, which plays a pivotal role in CIL. U87MG cells show CIL when they contact normal glia. In spheroid confrontation assays U87MG cells showed only limited invasion of the glial population, but reduction of Nm23-H1 expression in U87MG cells abrogated CIL resulting in invasion. In U87MG cells, Nm23-H1 is translocated to the sites of contact with glia through association with α-catenin and N-cadherin. Mutants of Nm23-H1, which lacked the binding ability with Tiam1, or α-catenin did not restore CIL. Moreover, the expression of ephrin-B1 in tumor cells disrupted CIL and promoted invasion. As one mechanism, ephrin-B1 inhibits the association of Nm23-H1 with Tiam1, which contributes for activation of Rac1. These results indicate a novel function of Nm23-H1 to control CIL, and its negative regulation by ephrin-B1.

Collective cell migration of the cephalic neural crest: The art of integrating information

The cephalic neural crest (NC) cells delaminate from the neuroepithelium in large numbers and undergo collective cell migration under the influence of multiple factors including positive and negative taxis, cell-cell interactions mediating cell sorting, cell cooperation, and Contact-Inhibition of Locomotion. The migration has to be tightly regulated to allow NC cells to reach precise locations in order to contribute to various craniofacial structures such as the skeletal and peripheral nervous systems. Several birth defects, syndromes, and malformations are due to improper cephalic NC (CNC) migration, and NC cell migration bears important similarities to cancer cell invasion and metastasis dissemination. Therefore, understanding how CNC cells interpret multiple inputs to achieve directional collective cell migration will shed light on pathological situations where cell migration is involved.

Cancer cell migration: when red light switched to green

The doctrine of ‘the golden mean' of the Confucian certainly applies at the molecular level to cell growth and migration. It is critically important for tissue architecture and homeostasis that cells stop proliferation when reaching appropriate density and halt migration in a direction to avoid collision with others. This ‘red light' to hinder cell movement is essential for maintaining contact inhibition of locomotion (CIL)—a phenomenon that a cell ceases to continue moving in the same direction when it comes into contact with another cell. The concept of CIL emerged initially from the early work of Abercrombie and Heaysman in the 1950s.1 Deficiencies in this cell communication system may lead to uncontrolled cell migration towards neighboring cells—an invasive process often observed in cancer. Indeed, metastatic cancer cells have often gained the capability to migrate specifically towards non-malignant cells and away from its cancerous peers. Understanding the molecular basis of this selective migration will greatly enhance our ability to prevent cancer dissemination, a lethal process in a majority of tumor types. In a recent issue of Nature Cell Biology, Astin and colleagues2 report that defective CIL between normal and cancerous cells is dictated by a switch of the repulsive ‘red light'—the EphA receptor signaling—to the attractive ‘green light', the EphB receptor signaling (Figure 1). These intriguing findings shed some light on the control of CIL and pave the way for future characterization of its role in cancer.

Collective Chemotaxis Requires Contact-Dependent Cell Polarity

SummaryDirectional collective migration is now a widely recognized mode of migration during embryogenesis and cancer. However, how a cluster of cells responds to chemoattractants is not fully understood. Neural crest cells are among the most motile cells in the embryo, and their behavior has been likened to malignant invasion. Here, we show that neural crest cells are collectively attracted toward the chemokine Sdf1. While not involved in initially polarizing cells, Sdf1 directionally stabilizes cell protrusions promoted by cell contact. At this cell contact, N-cadherin inhibits protrusion and Rac1 activity and in turn promotes protrusions and activation of Rac1 at the free edge. These results show a role for N-cadherin during contact inhibition of locomotion, and they reveal a mechanism of chemoattraction likely to function during both embryogenesis and cancer metastasis, whereby attractants such as Sdf1 amplify and stabilize contact-dependent cell polarity, resulting in directional collective migration.

Movement Directionality in Collective Migration of Germ Layer Progenitors

Collective cell migration, the simultaneous movement of multiple cells that are connected by cell-cell adhesion, is ubiquitous in development, tissue repair, and tumor metastasis [1, 2]. It has been hypothesized that the directionality of cell movement during collective migration emerges as a collective property [3, 4]. Here we determine how movement directionality is established in collective mesendoderm migration during zebrafish gastrulation. By interfering with two key features of collective migration, (1) having neighboring cells and (2) adhering to them, we show that individual mesendoderm cells are capable of normal directed migration when moving as single cells but require cell-cell adhesion to participate in coordinated and directed migration when moving as part of a group. We conclude that movement directionality is not a de novo collective property of mesendoderm cells but rather a property of single mesendoderm cells that requires cell-cell adhesion during collective migration.

Collective cell migration in development

Collective cell migration is a key process during the development of most organisms. It can involve either the migration of closely packed mesenchymal cells that make dynamic contacts with frequently changing neighbour cells, or the migration of epithelial sheets that typically display more stable cell-cell interactions and less frequent changes in neighbours. These collective movements can be controlled by short- or long-range dynamic gradients of extracellular signalling molecules, depending on the number of cells involved and their distance of migration. These gradients are sensed by some or all of the migrating cells and translated into directed migration, which in many settings is further modulated by cell-contact-mediated attractive or repulsive interactions that result in contact-following or contact-inhibition of locomotion, respectively. Studies of collective migration of groups of epithelial cells during development indicate that, in some cases, only leader cells sense and migrate up an external signal gradient, and that adjacent cells follow through strong cell-cell contacts. In this Commentary, I review studies of collective cell migration of differently sized cell populations during the development of several model organisms, and discuss our current understanding of the molecular mechanisms that coordinate this migration.

Behaviour and structure of the leading lamella in moving fibroblasts. I. Occurrence and centripetal movement of arc-shaped microfilament bundles beneath the dorsal cell surface.

Arc-shaped bundles of microfilaments are frequently found beneath the dorsal surface of the leading lamella of chick embryo fibroblasts. These structures, called arcs, form parallel to, and 2-10 micron from the leading edge of the lamella and they then move centripetally through the lamella and disappear in front of the cell nucleus. Arcs move centripetally at a mean speed of 1.33 (+/- 0.08 S.E.) micron min-1 relative to the substratum. Arcs are specifically associated with cells that are actively protrusive. They are common in fanshaped fibroblasts and in those cells that are newly spreading on a substratum. Arcs are absent from fibroblasts that have only small lamellae or that are polygonal. The correlation between are formation and protrusive activity is also clearly shown by the locomotory behaviour of fan-shaped cells. When protrusion of the lamella is increased by tail detachment, fibroblasts often develop numerous arcs, which chase each other backwards through the lamella. Conversely, arc formation ceases during contact inhibition of locomotion. In cells with large convex-edged lamellae there is a dorsal submembraneous sheath of microfilaments. All of the filaments comprising the sheath are oriented parallel to the margin of the lamella. Arcs are regions of the sheath where the microfilaments are more densely packed and hence visible by phase-contrast microscopy. There is no obvious relationship between the dorsally situated arcs and microfilament sheath, and the stress fibres that are associated with the ventral cell surface. The similarities between the movement and behaviour of arcs and the centripetal transport of particles on the surface of the lamella suggest a role for the microfilament sheath in the movement of particles.

Analysing the motile behaviour of cells: a general approach with special reference to pairs of cells in collision.

As a measure of the change in motion of locomoting cells, acceleration has several advantages over more conventional measures such as rate of change in speed and rate of change in direction. In particular the instantaneous acceleration vector associated with a specific event, such as the collision of the cell with another, may be correlated with directional information contained in the structure of the cell and in the geometrical configuration of the event. It is hoped that this will prove to be a generally useful method for examining the relation between cell structure and motion during both normal and aberrant behaviour. Preliminary results obtained with this method to examine the changes in motion of a normal cell and a malignant cell on colliding with each other are already of interest for elucidating the mechanism of contact inhibition of locomotion and its failure during malignant invasion.

Locomotory invasion of human cervical epithelium and avian fibroblasts by HeLa cells in vitro.

The locomotory invasive ability of HeLa cells was tested against: (a) embryonic chick heart fibroblasts (CHF); and (b) normal epithelial cells from human cervix (HCE) in explant confrontations. Data for analyses were obtained from replicate cultures fixed 24 h after junction and from 24-h time-lapse films. The mean invasion index for HeLa versus CHF did not indicate significant obstruction but analyses of hourly radial advance and orientation frequencies showed that obstruction eventually developed as postjunctional incubation time increased. Early contacts between HeLa and CHF demonstrated non-reciprocity of type I contact inhibition of locomotion by the tumour cells, which continued moving in their original direction to underlap contact-inhibited fibroblasts and eventually to occupy spaces vacated by them. When CHF population density increased and free space diminished, HeLa cells displayed directional and probably substrate-dependent contact inhibition. The high invasion index of HeLa versus HCE was largely due to occupation of previous HCE territory by tumour cells and only occasionally to actual infiltration of the epithelial sheet. After contact with HeLa, ruffling substrate-adherent marginal epithelial cells displayed contractile, type I contact inhibition of locomotion. After orientation changes, they gradually retreated. Against HCE, HeLa cells exhibited non-reciprocity of type I contact inhibition and continued radially forward, following the retreating epithelial margin. They did not move onto exposed upper surfaces of epithelial cells and did not underlap marginal cells firmly adherent to the substratum. Invasion of the epithelial sheet was seen only when initial access beneath a cell with a non-adherent margin was available. The contact relationships of isolated invading HeLa cells with their epithelial neighbours suggested successive non-reciprocal contact inhibition reactions.

Contact inhibition of locomotion and the structure of homotypic and heterotypic intercellular contacts in embryonic epithelial cultures

Epithelia from the early chick embryo have been grown in culture and then fixed for electron microscopy so that the ultrastructure of intercellular contacts could be examined. Epithelia were used which showed various forms of contact inhibition of locomotion upon confrontation with one another. Confrontations of hypoblast with hypoblast after 6 days, and endoblast with endoblast after 24 h showed type 1 contact inhibition and formed desmosomes and zonulae adhaerentes with extensive microfilament collinearity between apposed cells. Hypoblast-hypoblast confrontations after 24 h resulted in type 2 contact inhibition with considerable ruffling and position shifting. In this case desmosomes were absent and microfilament collinearity was restricted. Endoblast cells after 24 h in culture show type 2 inhibition with respect to hypoblast monolayers which they infiltrated upon confrontation. Examination of these heterotypic contacts also showed an absence of desmosomes and reduced adhaerens junctions. Intermediate filaments accumulated at all contact sites examined. It is concluded that whereas type 1 contact inhibition of locomotion in these epithelial cells is accompanied by desmosome formation and extensive zonula adhaerens junctions, type 2 inhibition is not. These junctional deficiences may be responsible in part for the cell motility characteristically observed in monolayers of type 2 inhibited cells.

Interactions between living and zinc-fixed cells in culture

When chick heart fibroblasts collide with zinc-fixed fibroblasts in culture, they show a typical ‘contact inhibition of locomotion’ reaction both an inhibition of overlapping and contact paralysis occurring. Previous reports in the literature have suggested that contact inhibition of locomotion only occurs when the collision is between living cells.