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Modeling mammary epithelial cell polarization and the role of podocalyxin in breast tumor progressionGraves, Marcia Lynn 11 1900 (has links)
The mammary gland consists of an organized network of epithelial ducts and lobules. This histoarchitecture can be recapitulated in vitro by culturing mammary epithelial cells as 3D spheroids embedded in a reconstituted basement membrane. I first used this assay to characterize the role of cell-cell and cell-ECM adhesion in the formation and polarization of the apical junction complexes in normal mammary epithelial cells. Cell-cell adhesion alone was sufficient to initiate polarized junction assembly. However, the addition of exogenous ECM generated a spatial polarity signal dependent on laminin-1 and α6 and β1 integrins. This caused clusters of mammary epithelial cells to re-localize the junctional complexes to the center of the spheroid prior to lumen formation.
In ductal breast carcinoma, a critical hallmark is the loss of normal polarized tissue architecture without the induction of an epithelial-to-mesenchymal transformation (EMT). Thus, misregulation of molecules that function as polarity determinants may contribute to ductal tumor progression. Podocalyxin is an anti-adhesive glycoprotein that may be involved, as it is important in epithelial morphogenesis, and its overexpression in clinical breast tumors is associated with poor outcome. Despite this, overexpression of podocalyxin in normal mammary epithelial cells did not disrupt 3D morphogenesis or apicobasal polarity. However, its overexpression in non-metastatic breast tumor cells did perturb the architecture and growth of tumor spheroids in vitro and it facilitated subcutaneous tumor growth in vivo without causing an EMT. Mechanistically, podocalyxin localized to and expanded non-adhesive membrane domains and induced microvillus formation that was dependent on its extracellular domain and Rho GTPase-regulated actin polymerization. Podocalyxin also recruited its intracellular binding partners NHERF-1 and ezrin via its cytoplasmic tail. Strikingly, the formation of this protein complex was not required for microvillus formation. Additionally, podocalyxin delayed cell-cell aggregation and decreased the initial adhesion, spreading and strength of attachment of tumor cells to fibronectin where it restricted β1 integrin localization to the basal/attached domain. These alterations in adhesion possibly contributed to podocalyxin's ability to increase growth factor-dependent tumor cell migration. Altogether, these data indicate that podocalyxin overexpression may facilitate a ductal tumor-like progression that involves EMT-independent alterations in tissue architecture.
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Modeling mammary epithelial cell polarization and the role of podocalyxin in breast tumor progressionGraves, Marcia Lynn 11 1900 (has links)
The mammary gland consists of an organized network of epithelial ducts and lobules. This histoarchitecture can be recapitulated in vitro by culturing mammary epithelial cells as 3D spheroids embedded in a reconstituted basement membrane. I first used this assay to characterize the role of cell-cell and cell-ECM adhesion in the formation and polarization of the apical junction complexes in normal mammary epithelial cells. Cell-cell adhesion alone was sufficient to initiate polarized junction assembly. However, the addition of exogenous ECM generated a spatial polarity signal dependent on laminin-1 and α6 and β1 integrins. This caused clusters of mammary epithelial cells to re-localize the junctional complexes to the center of the spheroid prior to lumen formation.
In ductal breast carcinoma, a critical hallmark is the loss of normal polarized tissue architecture without the induction of an epithelial-to-mesenchymal transformation (EMT). Thus, misregulation of molecules that function as polarity determinants may contribute to ductal tumor progression. Podocalyxin is an anti-adhesive glycoprotein that may be involved, as it is important in epithelial morphogenesis, and its overexpression in clinical breast tumors is associated with poor outcome. Despite this, overexpression of podocalyxin in normal mammary epithelial cells did not disrupt 3D morphogenesis or apicobasal polarity. However, its overexpression in non-metastatic breast tumor cells did perturb the architecture and growth of tumor spheroids in vitro and it facilitated subcutaneous tumor growth in vivo without causing an EMT. Mechanistically, podocalyxin localized to and expanded non-adhesive membrane domains and induced microvillus formation that was dependent on its extracellular domain and Rho GTPase-regulated actin polymerization. Podocalyxin also recruited its intracellular binding partners NHERF-1 and ezrin via its cytoplasmic tail. Strikingly, the formation of this protein complex was not required for microvillus formation. Additionally, podocalyxin delayed cell-cell aggregation and decreased the initial adhesion, spreading and strength of attachment of tumor cells to fibronectin where it restricted β1 integrin localization to the basal/attached domain. These alterations in adhesion possibly contributed to podocalyxin's ability to increase growth factor-dependent tumor cell migration. Altogether, these data indicate that podocalyxin overexpression may facilitate a ductal tumor-like progression that involves EMT-independent alterations in tissue architecture.
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Modeling mammary epithelial cell polarization and the role of podocalyxin in breast tumor progressionGraves, Marcia Lynn 11 1900 (has links)
The mammary gland consists of an organized network of epithelial ducts and lobules. This histoarchitecture can be recapitulated in vitro by culturing mammary epithelial cells as 3D spheroids embedded in a reconstituted basement membrane. I first used this assay to characterize the role of cell-cell and cell-ECM adhesion in the formation and polarization of the apical junction complexes in normal mammary epithelial cells. Cell-cell adhesion alone was sufficient to initiate polarized junction assembly. However, the addition of exogenous ECM generated a spatial polarity signal dependent on laminin-1 and α6 and β1 integrins. This caused clusters of mammary epithelial cells to re-localize the junctional complexes to the center of the spheroid prior to lumen formation.
In ductal breast carcinoma, a critical hallmark is the loss of normal polarized tissue architecture without the induction of an epithelial-to-mesenchymal transformation (EMT). Thus, misregulation of molecules that function as polarity determinants may contribute to ductal tumor progression. Podocalyxin is an anti-adhesive glycoprotein that may be involved, as it is important in epithelial morphogenesis, and its overexpression in clinical breast tumors is associated with poor outcome. Despite this, overexpression of podocalyxin in normal mammary epithelial cells did not disrupt 3D morphogenesis or apicobasal polarity. However, its overexpression in non-metastatic breast tumor cells did perturb the architecture and growth of tumor spheroids in vitro and it facilitated subcutaneous tumor growth in vivo without causing an EMT. Mechanistically, podocalyxin localized to and expanded non-adhesive membrane domains and induced microvillus formation that was dependent on its extracellular domain and Rho GTPase-regulated actin polymerization. Podocalyxin also recruited its intracellular binding partners NHERF-1 and ezrin via its cytoplasmic tail. Strikingly, the formation of this protein complex was not required for microvillus formation. Additionally, podocalyxin delayed cell-cell aggregation and decreased the initial adhesion, spreading and strength of attachment of tumor cells to fibronectin where it restricted β1 integrin localization to the basal/attached domain. These alterations in adhesion possibly contributed to podocalyxin's ability to increase growth factor-dependent tumor cell migration. Altogether, these data indicate that podocalyxin overexpression may facilitate a ductal tumor-like progression that involves EMT-independent alterations in tissue architecture. / Medicine, Faculty of / Graduate
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Implication des voies de différenciation épithéliale précoce dans la morphogenèse mammaire et la progression des cancers du sein / Involvement of precocious epithelial differentiation pathways in mammary morphogenesis and progression of breast cancers and progression of breast cancersIdoux-Gillet, Ysia 20 September 2013 (has links)
La morphogenèse de la glande mammaire résulte de la coordination de différentes voies, incluant l'apoptose, la prolifération, la différenciation et la dynamique des cellules souches/progénitrices. La transition épithéliale-mésenchymateuse (EMT) semble être impliquée dans ces voies de signalisation. Ainsi, nous nous sommes concentrés sur le facteur de transcription Slug, un gène clé régulant l'EMT, et son implication dans la morphogenèse de la glande mammaire. Dans un premier temps, en utilisant un modèle de souris transgéniques Slug-Lacz, nous avons localisé Slug dans une sous-population couvrant 10 à 20% des cellules basales du tubule et des cap cells du bourgeons terminal, coexprimant les marqueurs P-cadhérine, CK5, CD49f. Ensuite, nous avons montré par des expériences in vitro de perte et de gain de fonction, que Slug régulait la différenciation et la prolifération des cellules épithéliales mammaires. De plus, nous avons trouvé que Slug inhibait l'apoptose, promouvait la motilité cellulaire, et permettait l'émergence et la croissance de mammosphères clonales. Ce dernier point montre l'implication de Slug dans les cellules souches, qui est renforcé par le fait que des cellules primaires déficientes pour Slug étaient incapables de donner des mammosphères secondaires. Par ailleurs, nous avons pu observer in vivo que les souris déficientes pour Slug présentaient un retard de développement de la glande mammaire, possédant moins de cellules en prolifération, et une surexpression des marqueurs des cellules luminale CK8/18, GATA3 et ER. D'autres gènes régulant l'EMT sont retrouvés surexprimés, suggérant un mécanisme de compensation, qui peut expliquer le fait que le retard de développement de la glande mammaire est rattrapé à l'âge adulte. Les glandes mammaires Slug-knockout présentaient également des branchements excessifs, évoquant une différenciation précoce, similaire aux glandes mammaires de souris déficientes pour la P-cadhérine, exprimée dans les cellules basales. Sachant cela, nous avons constaté que la P-cadhérine était diminuée dans les glandes mammaires Slug-knockout, et dans les cellules CommaDβ traitées par siRNA ciblant Slug. Nous avons alors trouvé que Slug se liait directement au promoteur de la P-cadhérine et l'activait, et que cette dernière intervenait dans certains effets fonctionnels de Slug, tels que la croissance de mammosphères, la différenciation et la migration cellulaire. Ainsi, nous avons montré l'importance d'une nouvelle voie de signalisation Slug/P-cadhérine dans les capacités souches/progénitrices des cellules épithéliales mammaires, intégrant la différenciation et la motilité cellulaire, et nous avons maintenant une meilleure compréhension de son rôle dans l'agressivité de certains cancers du sein. / Mammary gland morphogenesis results from the coordination of different pathways, including apoptosis, proliferation, differentiation, and stem/progenitor cell dynamics. Epithelial-mesenchymal transition (EMT) appears to be involved in these signalling pathways. Thus, we focused on transcription factor Slug, a key gene regulating EMT, and its involvement in mammary gland morphogenesis. First, using a Slug–LacZ transgenic mice model, we located Slug in a subpopulation covering about 10–20% basal duct cells and cap cells of terminal end bud, coexpressed with basal markers P-cadherin, CK5 and CD49f. Then, we have shown by in vitro experiments of loss and gain of function that Slug regulated the differentiation and proliferation of mammary epithelial cells. Moreover, we found that Slug inhibited apoptosis, promoted cell motility, and allowed the emergence and growth of clonal mammospheres. This last point shows the involvement of Slug in stem cells, which is reinforced by the fact that primary cells deficient for Slug were unable to give secondary mammospheres. Furthermore, we observed in vivo that mice deficient for Slug showed delayed development of the mammary gland, with less proliferating cells, and overexpression of markers of luminal cells CK8/18, GATA3 and ER. Other genes regulating EMT are found overexpressed, suggesting a compensatory mechanism, which can explain the fact that the delayed development of the mammary gland is caught up in adulthood. The Slug-knockout mammary glands also showed overbranching, evoking an early differentiation, similar to the mammary glands of mice deficient in P-cadherin, expressed in the basal cells. Knowing this, we found that P-cadherin was decreased in Slug-knockout mammary glands, and in CommaDβ cells treated with siRNA targeting Slug. We then found that Slug binds directly to the promoter of the P-cadherin and activated it, and that P-cadherin was involved in some functional effects of Slug, such as mammospheres growth, differentiation and cell migration. Thus, we have shown the importance of a new signalling pathway Slug/P-cadherin in the capacity of mammary epithelial stem/progenitor cells, integrating differentiation and cell motility, and we now have a better understanding of its role in the aggressiveness of some breast cancers.
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