Group leader position
The Cell Biology department at the Institut Curie (UMR 144 Institut Curie/CNRS) in Paris is inviting applications from outstanding candidates interested in normal epithelium and cancer stem cells biology. Priority will be given to projects focused on mammary gland development, mammary stem cell biology and the mechanisms of breast cancer.
Cell migration and invasion
Group leader: Danijela Matic Vignjevic
The broad objective of our research is to understand how epithelial cells interact with their microenvironment during migration, focusing on the mechanism of cell migration and the role of actin cytoskeleton in this process. We use a gut as model system to understand cell migration in homeostasis, wound healing and cancer invasion. Our research strategy combines molecular and cell biology techniques with live-cell imaging. In particular, we use 2D and 3D in vitro cell cultures; tissue slices cultured ex vivo; and different transgenic mouse models to study cell migration in the living animal.
Cell migration in gut homeostasis and during wound healing.
The entire intestinal epithelium is renewed every week due to cell division in the crypts coupled with cell migration towards the villi and loss of cells by apoptosis at the tip of villi. However, the mechanism responsible for the migration of intestinal cells remains largely unknown. Our goal is to determine if epithelial cells migrate passively as a consequence of the pushing force generated by cell division in the crypts, actively using cellular protrusions or if they are transported by underlying fibroblasts.
Role of actin cytoskeleton in cell invasion.
Uncoupling cell proliferation from apoptosis and possibly from cell migration can lead to pathologies such as cancer. In carcinoma in situ, the basement membrane (BM) represents a physical barrier that prevents spreading of the primary tumor to adjacent tissues. We have shown that breaching of the BM is a three-stage process: specialized, finger-like protrusions, called invadopodia first perforate BM, then elongate into mature invadopodia that finally guide the cell towards the stromal compartment (Figure 1A). Formation of invadopodia requires only the actin cytoskeleton, while invadopodia elongation also depends on intact microtubules and vimentin intermediate filament networks (Figure 1B). We are investigating the role of different actin binding proteins in invadopodia formation. For example, by stabilizing actin filaments into bundles, we found that fascin is required for formation and maintenance of invadopodia (Schoumacher et al. 2010). In agreement with its role in invasion, we found that fascin is highly expressed at the invasive front of human colon adenocarcinoma while completely absent from normal epithelial cells (Vignjevic et al, 2007) (Figure 1C). To test if fascin expression can induce metastasis, we have generated a conditional fascin transgenic mouse and crossed it with mice that develop spontaneous benign tumors in the gut (Schoumacher et al. in preparation).
Role of actin cytoskeleton in cell migration.
Cells initiate migration by extending membrane protrusions, lamellipodia and filopodia, that are driven by actin polymerization. We are investigating if filopodia are sensory organelles responsible for directed cell migration using 2D and 3D chemotactic chambers. Newly extended cellular protrusions are then stabilized by adhesions that link the actin cytoskeleton to the underlying extracellular matrix. Cells move forward by exerting traction forces on these adhesions at the cell front while adhesions at the cell rear must be released to allow cell translocation. We are interested in how tensile forces generated by stress fiber contraction, strengthen adhesions at the cell front but disassemble adhesions at the cell rear. Finally, using two-photon microscopy we are studying how cells migrate in and interact with complex environments in the living mice (Figure 2A). For example, recently we have explored the appearance of focal adhesions assembled in vitro and in vivo (Geraldo et al, 2012) (Figure 2B).
Cooperation of cancer cells and fibroblasts during invasion.
It is believed that cancer cells perforate BM, but stromal cells such as carcinoma-associated fibroblasts (CAFs) also secrete matrix proteinases (Figure 3A). Our objective is to understand who is invading whom – do cancer cells invade the stroma or is the stroma invading tumor cells? We are studying if cancer cells and fibroblasts have overlapping or distinct functions that need to be combined to perforate the BM (Figure 3B). Once the BM becomes compromised, cancer cells migrate through the stroma towards the blood vessels, allowing dissemination of the tumor and formation of metastasis. Using multicellular spheroids of cancer cells embedded in 3D collagen matrices, we are investigating how CAFs stimulate invasion of cancer cells (Figure 3C). Finally, using orthotopic implantation of cancer cells into mouse colon wall we are investigating if CAFs can promote formation of metastasis.
Invasion of cancer cells induced by mechanical pressure.
In addition to cellular and biochemical tumor microenvironment, mechanical stress also plays a crucial role in tumor growth. In collaboration with physicists P. Nassoy (Institut d’Optique Graduate School, Talence) and G. Cappello (UMR168, Institute Curie) we are investigating if pressure imposed by stroma can have an additional role in stimulating cancer invasion.