Jean Paul Thiery

Epithelial-Mesenchymal Transitions in Development and Disease

The epithelial to mesenchymal transition (EMT) plays crucial roles in the formation of the body plan and in the differentiation of multiple tissues and organs. EMT also contributes to tissue repair, but it can adversely cause organ fibrosis and promote carcinoma progression through a variety of mechanisms. EMT endows cells with migratory and invasive properties, induces stem cell properties, prevents apoptosis and senescence, and contributes to immunosuppression. Thus, the mesenchymal state is associated with the capacity of cells to migrate to distant organs and maintain stemness, allowing their subsequent differentiation into multiple cell types during development and the initiation of metastasis.

Identical reactivity of monoclonal antibodies HNK-1 and NC-1: conservation in vertebrates on cells derived from the neural primordium and on some leukocytes

NC-1 and HNK-1, two mouse monoclonal antibodies raised against quail ciliary ganglion and a human leukemic cell-line, respectively, were found to display the same pattern of reactivity. Species investigated included human, rodents, birds and amphibians. In 1- to 3-day-old avian embryos, migrating crest cells are stained, whereas in older animals neuroepithelial cells and neurons are labelled. Staining with fluorescein isothiocyanate-conjugated NC-1 is blocked by preincubation with HNK-1. In immunoblot analyses both antibodies recognize the same pattern of bands which are different in central and peripheral nervous systems and vary during development. Thus, HNK-1/NC-1 provides a useful tool for investigating the ontogeny of neural and lymphocytic cells carrying this determinant, which, in view of its high degree of conservation during vertebrate evolution, may play an important part within the haematopoietic and nervous systems.

Mesenchymal Transition and Dissemination of Cancer Cells Is Driven by Myeloid-Derived Suppressor Cells Infiltrating the Primary Tumor

In order to metastasize, cancer cells need to acquire a motile phenotype. Previously, development of this phenotype was thought to rely on the acquisition of selected, random mutations and thus would occur late in cancer progression. However, recent studies show that cancer cells disseminate early, implying the existence of a different, faster route to the metastatic motile phenotype. Using a spontaneous murine model of melanoma, we show that a subset of bone marrow-derived immune cells (myeloid-derived suppressor cells or MDSC) preferentially infiltrates the primary tumor and actively promotes cancer cell dissemination by inducing epithelial-mesenchymal transition (EMT). CXCL5 is the main chemokine attracting MDSC to the primary tumor. In vitro assay using purified MDSC showed that TGF-β, EGF, and HGF signaling pathways are all used by MDSC to induce EMT in cancer cells. These findings explain how cancer cells acquire a motile phenotype so early and provide a mechanistic explanation for the long recognized link between inflammation and cancer progression.

An analysis of the bovine genome by Cs2SO4-Ag density gradient centrifugation.

Abstract Calf DNA preparations having molecular weights of 5 to 7 × 106 have been fractionated by preparative Cs2SO4—Ag+ density gradient centrifugation into a number of components. These may be divided into three groups: (1) the main DNA component (1.697 g/cm3; all densities quoted are those determined in CsCl density gradients), the 1.704 and 1.709 g/cm3 components form about 50, 25 and 10% of the genome, respectively; they are characterized by having symmetrical CsCl bands and melting curves, both of which have standard deviations close to those of bacterial DNAs of comparable molecular weight, and by their G + C contents being equal to 39, 48 and 54%, respectively; after heat-denaturation and reannealing, their buoyant densities in CsCl are greater than native DNA by 12, 10 and 3 mg/cm3, respectively. (2) The 1.705, 1.710, 1.714 and 1.723 g/cm3 components represent 4, 1.5, 7 and 1.5% of the DNA, respectively, and exhibit the properties of “satellite” DNAs; their CsCl bands and melting curves have standard deviations lower than those of bacterial DNAs; after heat-denaturation and reannealing, their buoyant densities are identical to native DNA, except for the 1.705 g/cm3 component, which remains heavier by 5 mg/cm3; in alkaline CsCl, only the 1.714 g/cm3 component shows a strand separation. (3) A number of minor components, forming 1% of the DNA, have been recognized, but they have not been investigated in detail; two of them (1.719 and 1.699 g/cm3) might correspond to ribosomal cistrons and mitochondrial DNA, respectively.

Epithelial-to-mesenchymal transition and autophagy induction in breast carcinoma promote escape from T-cell-mediated lysis.

Epithelial-to-mesenchymal transition (EMT) mediates cancer cell invasion, metastasis, and drug resistance, but its impact on immune surveillance has not been explored. In this study, we investigated the functional consequences of this mode of epithelial cell plasticity on targeted cell lysis by cytotoxic T lymphocytes (CTL). Acquisition of the EMT phenotype in various derivatives of MCF-7 human breast cancer cells was associated with dramatic morphologic changes and actin cytoskeleton remodeling, with CD24(-)/CD44(+)/ALDH(+) stem cell populations present exhibiting a higher degree of EMT relative to parental cells. Strikingly, acquisition of this phenotype also associated with an inhibition of CTL-mediated tumor cell lysis. Resistant cells exhibited attenuation in the formation of an immunologic synapse with CTLs along with the induction of autophagy in the target cells. This response was critical for susceptibility to CTL-mediated lysis because siRNA-mediated silencing of beclin1 to inhibit autophagy in target cells restored their susceptibility to CTL-induced lysis. Our results argue that in addition to promoting invasion and metastasis EMT also profoundly alters the susceptibility of cancer cells to T-cell-mediated immune surveillance. Furthermore, they reveal EMT and autophagy as conceptual realms for immunotherapeutic strategies to block immune escape.

The nervous system specific protein D2 is involved in adhesion among neurites from cultured rat ganglia

The rat nervous system specific protein D2 is an integral membrane protein present on all bodies and neurites of cultured neurons from brain fetuses [l-3]. In adult brain, D2 is found mainly on the outside of synaptic membranes [4-61. It has been hypothesized that this protein may be involved in the recognition mechanism during the early stage of synaptogenesis 15451. Here we have examined the effect of anti-D2 antibodies on the formation of neurite fascicles from cultured rat sympathetic ganglia. The results indicated that D2 may be involved in neurite-neurite interaction, a property which has been reported for the cell adhesion molecule (CAM) isolated from chick embryo neural tissue [7,8]. This property and similarities in molecular weight, membrane distribution and localization raise the possibility that D2 and CAM may be evolutionarily related proteins. This hypothesis is strengthened by the finding, that anti-CAM antibodies crossreact with D2 protein.

Appearance and distribution of fibronectin during chick embryo gastrulation and neurulation

Abstract The distribution of fibronectin (FN) was studied by immunofluorescence during gastrulation and early neurulation in avian embryos. FN was first detected under the upper layer (ul), just prior to the streak appearance. During gastrulation, FN was restricted to the basement membrane of the ul. The streak initially appeared as a protruding cell mass limited by FN strands. Later on, FN disappeared locally where the streak sank into the space under the ul. In the streak, the invaginated cells separated and migrated laterally along the FN-rich basement membrane of the ul. FN appeared in the basal surface of the definitive endoderm, when it was completed. Our results suggest that, prior to gastrulation, passive cell movements occur in the absence of FN, while during gastrulation, FN is involved in active movements. In the head, early neurulation followed the separation of the notochord from the neural plate by a FN-rich basement membrane. In contrast, in the trunk, the neural groove appeared first and remained in close apposition with the notochord and somitic mesenchyme twice as long as in the head. An intense FN staining was revealed first between the neural tube and the somite, and later on between the neural tube and the notochord.

Pathways of avian neural crest cell migration in the developing gut

The NC-1 and E/C8 monoclonal antibodies recognize a similar population of neural crest cells as they migrate from vagal levels of the neural tube and colonize the branchial arch region of 2- to 3-day-old chicken embryos. Some of these immunoreactive cells then appear to enter the gut mesenchyme on the third day of incubation just caudal to the third branchial cleft. After entering the gut, these cells migrate in a rostral-caudal direction, using primarily the superficial splanchnic mesodermal epithelium of the gut as a substratum. The antigen-positive cells remain preferentially associated with the splanchnopleure. Few antigenic cells enter the mesenchyme surrounding the endoderm at anterior levels whereas they are found throughout the mesenchyme when nearing the umbilicus. At postumbilical levels, immunoreactive cells are distributed on both sides of the differentiating muscle layer but not within it. Although fibronectin immunoreactivity can be found throughout the wall of the gut, there is no apparent relationship between the distribution of fibronectin and the location of the immunoreactive cells. These results suggest that a mechanism more complex than a mere interaction with fibronectin may account for migration of crest-derived cells in the gut.

Tumor Dissemination: An EMT Affair

A recent paper reports that circulating tumor cells (CTCs) from metastatic breast cancer patients exhibit heterogeneous epithelial and mesenchymal phenotypes and that CTCs display higher frequencies of partial or full-blown mesenchymal phenotype than carcinoma cells within primary tumors. Mesenchymal-like CTCs are also elevated in patients who are refractory to therapy.

Actin dynamics modulate mechanosensitive immobilization of E-cadherin at adherens junctions

Mechanical stress is increasingly being shown to be a potent modulator of cell–cell junctional morphologies in developmental and homeostatic processes. Intercellular force sensing is thus expected to be an important regulator of cell signalling and tissue integrity. In particular, the interplay between myosin contractility, actin dynamics and E-cadherin recruitment largely remains to be uncovered. We devised a suspended cell doublet assay to quantitatively assess the correlation between myosin II activity and local E-cadherin recruitment. The single junction of the doublet exhibited a stereotypical morphology, with E-cadherin accumulating into clusters of varied concentrations at the rim of the circular contact. This local recruitment into clusters derived from the sequestration of E-cadherin through a myosin-II-driven modulation of actin turnover. We exemplify how the regulation of actin dynamics provides a mechanism for the mechanosensitive response of cell contacts.