In vivo imaging of mammary epithelial cell dynamics in response to lineage-biased Wnt/β-catenin activation

International audienceHighlights d Lineage-biased b-catenin activation in mammary cells leads to hyperplastic lesions d Intravital imaging reveals mammary cell dynamics induced by b-catenin activation d Constitutive Wnt signaling induces squamous transdifferentiation of mammary cell

EGF controls the in vivo developmental potential of a mammary epithelial cell line possessing progenitor properties

The bilayered mammary epithelium comprises a luminal layer of secretory cells and a basal layer of myoepithelial cells. Numerous data suggest the existence of self-renewing, pluripotent mammary stem cells; however, their molecular characteristics and differentiation pathways are largely unknown. BC44 mammary epithelial cells in culture, display phenotypic characteristics of basal epithelium, i.e., express basal cytokeratins 5 and 14 and P-cadherin, but no smooth muscle markers. In vivo, after injection into the cleared mammary fat pad, these cells gave rise to bilayered, hollow, alveolus-like structures comprising basal cells expressing cytokeratin 5 and luminal cells positive for cytokeratin 8 and secreting β-casein in a polarized manner into the lumen. The persistent stimulation of EGF receptor signaling pathway in BC44 cells in culture resulted in the loss of the in vivo morphogenetic potential and led to the induction of active MMP2, thereby triggering cell scattering and motility on laminin 5. These data (a) suggest that BC44 cells are capable of asymmetric division for self-renewal and the generation of a differentiated progeny restricted to the luminal lineage; (b) clarify the function of EGF in the control of the BC44 cell phenotypic plasticity; and (c) suggest a role for this phenomenon in the mammary gland development

Postlaunch evidence-generation studies for medical devices in Spain: the RedETS approach to integrate real-world evidence into decision making

The Monitoring Studies (MS) program, the approach developed by RedETS to generate postlaunch real-world evidence (RWE), is intended to complement and enhance the conventional health technology assessment process to support health policy decision making in Spain, besides informing other interested stakeholders, including clinicians and patients. The MS program is focused on specific uncertainties about the real effect, safety, costs, and routine use of new and insufficiently assessed relevant medical devices carefully selected to ensure the value of the additional research needed, by means of structured, controlled, participative, and transparent procedures. However, despite a clear political commitment and economic support from national and regional health authorities, several difficulties were identified along the development and implementation of the first wave of MS, delaying its execution and final reporting. Resolution of these difficulties at the regional and national levels and a greater collaborative impulse in the European Union, given the availability of an appropriate methodological framework already provided by EUnetHTA, might provide a faster and more efficient comparative RWE of improved quality and reliability at the national and international levels

Mammary stem cells have myoepithelial cell properties.

Contractile myoepithelial cells dominate the basal layer of the mammary epithelium and are considered to be differentiated cells. However, we observe that up to 54% of single basal cells can form colonies when seeded into adherent culture in the presence of agents that disrupt actin-myosin interactions, and on average, 65% of the single-cell-derived basal colonies can repopulate a mammary gland when transplanted in vivo. This indicates that a high proportion of basal myoepithelial cells can give rise to a mammary repopulating unit (MRU). We demonstrate that myoepithelial cells, flow-sorted using two independent myoepithelial-specific reporter strategies, have MRU capacity. Using an inducible lineage-tracing approach we follow the progeny of myoepithelial cells that express α-smooth muscle actin and show that they function as long-lived lineage-restricted stem cells in the virgin state and during pregnancy.This work was funded by Cancer Research UK, Breast Cancer Campaign, the University of Cambridge, Hutchison Whampoa Limited, La Ligue Nationale Contre le Cancer (Equipe Labelisée 2013) and a grant from Agence Nationale de la Recherche ANR- 08-BLAN-0078-01 to M.A.G.This is the author accepted manuscript. The final version is available from Nature at http://www.nature.com/ncb/journal/vaop/ncurrent/full/ncb3025.html

Cloning and Characterization of Three Xenopus Slug Promoters Reveal Direct Regulation by Lef/\uce\ub2-Catenin Signaling

In amphibians and birds, one of the first steps of neu- ral crest cell (NCC) determination is expression of the transcription factor Slug. This marker has been used to demonstrate that BMP and Wnt molecules play a major role in NCC induction. However, it is unknown whether Slug expression is directly or indirectly regulated by these signals. We report here the cloning and character- ization of three Xenopus Slug promoters: that of the Xenopus tropicalis slug gene and those of two Xenopus laevis Slug pseudoalleles. Although the three genes en- code proteins with almost identical amino acid se- quences and are expressed with similar spatiotemporal patterns, their 5 -flanking regions are quite different. A striking difference is a deletion in the X. tropicalis gene located precisely at the transcription initiation site that results in the X. tropicalis promoter being inefficient in X. laevis. Additionally, we identified two regions com- mon to the three promoters that are necessary and suf- ficient to drive specific expression in NCCs. Interest- ingly, one of the common regulatory regions presents a functional Lef/ -catenin-binding site necessary for spe- cific expression. As the Lef -catenin complex is a down- stream effector of Wnt signaling, these results suggest that Xenopus Slug is a direct target of NCC determina- tion signals

Vers la caractérisation des cellules souches de la glande mammaire murine adulte

L’épithélium mammaire est une bicouche composée d’une part de cellules myoépithéliales basales et d’autre part de cellules luminales. Les propriétés si particulières de la morphogenèse post-natale de la glande mammaire, notamment la mise en place du réseau canalaire durant la puberté, et la formation d’alvéoles à chaque grossesse, suggèrent que des cellules souches résident dans l’épithélium mammaire adulte. Différentes stratégies incluant notamment l’analyse de la rétention de marqueurs de l’ADN, l’étude du potentiel de développement in vivo de sous-populations cellulaires et des approches transgéniques, sont utilisées depuis quelques années pour isoler et caractériser les cellules souches et progénitrices de l’épithélium mammaire murin. Les caractéristiques moléculaires de ces cellules restent à définir de façon précise mais des progrès notables ont déjà été réalisés pour leur enrichissement et leur identification

Growth defects induced by perturbation of β1-integrin function in the mammary gland epithelium result from a lack of MAPK activation via the Shc and Akt pathways

Adhesion to extracellular matrix (ECM) induces intracellular signals that modulate cell proliferation, survival and differentiation. To study signalling events triggered by cell–ECM interactions in vivo we used transgenic mice exhibiting reduced mammary epithelial cell proliferation and increased apoptosis rates during the growth phase in pregnancy and lactation due to expression of a β1-integrin dominant-negative mutant in the mammary gland epithelium. Here we show that ERK and JNK MAPKs were markedly less activated in lactating transgenic glands thereby accounting for the growth defects. The FAK pathway was not affected suggesting a mechanism of activation additional to the ECM signal. On the contrary, the significant decrease of Shc phosphorylation, Grb2 recruitment and the reduced phosphorylation level of Akt Thr308 and Akt substrates FKHR and Bad detected in transgenic glands show that activation of the Shc and the Akt pathways require intact cell–ECM interactions. These results provide an insight into the mechanisms of growth control by integrin-mediated adhesion that operate in vivo