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Change in cell shape is required for matrix metalloproteinase-induced epithelial-mesenchymal transition of mammary epithelial cells

Description: Cell morphology dictates response to a wide variety of stimuli, controlling cell metabolism, differentiation, proliferation, and death. Epithelial-mesenchymal transition (EMT) is a developmental process in which epithelial cells acquire migratory characteristics, and in the process convert from a 'cuboidal' epithelial structure into an elongated mesenchymal shape. We had shown previously that matrix metalloproteinase-3 (MMP3) can stimulate EMT of cultured mouse mammary epithelial cells through a process that involves increased expression of Rac1b, a protein that stimulates alterations in cytoskeletal structure. We show here that cells treated with MMP-3 or induced to express Rac1b spread to cover a larger surface, and that this induction of cell spreading is a requirement of MMP-3/Rac1b-induced EMT. We find that limiting cell spreading, either by increasing cell density or by culturing cells on precisely defined micropatterned substrata, blocks expression of characteristic markers of EMT in cells treated with MMP-3. These effects are not caused by general disruptions in cell signaling pathways, as TGF-{beta}-induced EMT is not affected by similar limitations on cell spreading. Our data reveal a previously unanticipated cell shape-dependent mechanism that controls this key phenotypic alteration and provide insight into the distinct mechanisms activated by different EMT-inducing agents.
Date: June 26, 2008
Creator: Nelson, Celeste M.; Khauv, Davitte; Bissell, Mina J. & Radisky, Derek C.
Partner: UNT Libraries Government Documents Department

Single proteins that serve linked functions in intracellular and extracellular microenvironments

Description: Maintenance of organ homeostasis and control of appropriate response to environmental alterations requires intimate coordination of cellular function and tissue organization. An important component of this coordination may be provided by proteins that can serve distinct, but linked, functions on both sides of the plasma membrane. Here we present a novel hypothesis in which non-classical secretion can provide a mechanism through which single proteins can integrate complex tissue functions. Single genes can exert a complex, dynamic influence through a number of different processes that act to multiply the function of the gene product(s). Alternative splicing can create many different transcripts that encode proteins of diverse, even antagonistic, function from a single gene. Posttranslational modifications can alter the stability, activity, localization, and even basic function of proteins. A protein can exist in different subcellular localizations. More recently, it has become clear that single proteins can function both inside and outside the cell. These proteins often lack defined secretory signal sequences, and transit the plasma membrane by mechanisms separate from the classical ER/Golgi secretory process. When examples of such proteins are examined individually, the multifunctionality and lack of a signal sequence are puzzling - why should a protein with a well known function in one context function in such a distinct fashion in another? We propose that one reason for a single protein to perform intracellular and extracellular roles is to coordinate organization and maintenance of a global tissue function. Here, we describe in detail three specific examples of proteins that act in this fashion, outlining their specific functions in the extracellular space and in the intracellular space, and we discuss how these functions may be linked. We present epimorphin/syntaxin-2, which may coordinate morphogenesis of secretory organs (as epimorphin) with control of protein secretion (as syntaxin-2), amphoterin/high mobility group box-1 (HMGB1), which ...
Date: June 3, 2009
Creator: Radisky, Derek C.; Stallings-Mann, Melody; Hirai, Yohei & Bissell, Mina J.
Partner: UNT Libraries Government Documents Department

The organizing principle: microenvironmental influences in the normal and malignant breast

Description: The current paradigm for cancer initiation and progression rests on the groundbreaking discoveries of oncogenes and tumor suppressor genes. This framework has revealed much about the role of genetic alterations in the underlying signaling pathways central to normal cellular function and to tumor progression. However, it is clear that single gene theories or even sequential acquisition of mutations underestimate the nature of the genetic and epigenetic changes in tumors, and do not account for the observation that many cancer susceptibility genes (e.g. BRCA1, APC) show a high degree of tissue specificity in their association with neoplastic transformation. Therefore, the cellular and tissue context itself must confer additional and crucial information necessary for mutated genes to exert their influence. A considerable body of evidence now shows that cell - cell and cell - extracellular matrix (ECM) interactions are essential organizing principles that help define the nature of the tissue context, and play a crucial role in regulating homeostasis and tissue specificity. How this context determines functional integrity, and how its loss can lead to malignancy, appears to have much to do with tissue structure and polarity.
Date: August 20, 2002
Creator: Bissell, Mina; Radisky, Derek C.; Rizki, Aylin; Weaver, Valerie M. & Petersen, Ole W.
Partner: UNT Libraries Government Documents Department

Proliferation and Polarity in Breast Cancer: Untying the Gordian Knot

Description: Epithelial cancers are associated with genomic instability and alterations in signaling pathways that affect proliferation, apoptosis, and integrity of tissue structure. Overexpression of a number of oncogenic protein kinases has been shown to malignantly transform cells in culture and to cause tumors in vivo, but the interconnected signaling events induced by transformation still awaits detailed dissection. We propose that the network of cellular signaling pathways can be classified into functionally distinct branches, and that these pathways are rewired in transformed cells and tissues after they lose tissue-specific architecture to favor tumor expansion and invasion. Using three-dimensional (3D) culture systems, we recently demonstrated that polarity and proliferation of human mammary epithelial cancer cells were separable consequences of signaling pathways downstream of PI3 kinase.These, and results from a number of other laboratories are beginning to provide insight into how different signaling pathways may become interconnected in normal tissues to allow homeostasis, and how they are disrupted during malignant progression.
Date: May 9, 2005
Creator: Liu, Hong; Radisky, Derek C. & Bissell, Mina J.
Partner: UNT Libraries Government Documents Department

Mechanisms of disease: epithelial-mesenchymal transition and back again: does cellular plasticity fuel neoplastic progression?

Description: Epithelial-mesenchymal transition (EMT) is a conversion that facilitates organ morphogenesis and tissue remodeling in physiological processes such as embryonic development and wound healing. A similar phenotypic conversion is also detected in fibrotic diseases and neoplasia, which is associated with disease progression. EMT in cancer epithelial cells often seems to be an incomplete and bi-directional process. In this Review, we discuss the phenomenon of EMT as it pertains to tumor development, focusing on exceptions to the commonly held rule that EMT promotes invasion and metastasis. We also highlight the role of the RAS-controlled signaling mediators, ERK1, ERK2 and PI3-kinase, as microenvironmental responsive regulators of EMT.
Date: February 13, 2008
Creator: Bissell, Mina J; Turley, Eva A.; Veiseh, Mandana; Radisky, Derek C. & Bissell, Mina J.
Partner: UNT Libraries Government Documents Department

CANCELLED EMT and back again: does cellular plasticity fuel neoplastic progression?

Description: Epithelial-mesenchymal transition (EMT) is a cellular transdifferentiation program that facilitates organ morphogenesis and tissue remodeling in physiological processes such as embryonic development and wound healing. However, a similar phenotypic conversion is also detected in fibrotic diseases and neoplasia, in which it is associated with disease progression. EMT in cancer epithelial cells often appears to be an incomplete and bi-directional process. Here we discuss the phenomenon of EMT as it pertains to tumor development, focusing on exceptions to the commonly held rule that EMT promotes invasion and metastasis. We also highlight the role of the Ras-controlled signaling mediators, ERK1, ERK2 and PI3-kinase, as microenvironmental responsive regulators of EMT.
Date: February 24, 2007
Creator: Turley, Eva A.; Veiseh, Mandana; Radisky, Derek C. & Bissell, MinaJ.
Partner: UNT Libraries Government Documents Department

Laminin and biomimetic extracellular elasticity enhance functional differentiation in mammary epithelia

Description: In the mammary gland, epithelial cells are embedded in a 'soft' environment and become functionally differentiated in culture when exposed to a laminin-rich extracellular matrix gel. Here, we define the processes by which mammary epithelial cells integrate biochemical and mechanical extracellular cues to maintain their differentiated phenotype. We used single cells cultured on top of gels in conditions permissive for {beta}-casein expression using atomic force microscopy to measure the elasticity of the cells and their underlying substrata. We found that maintenance of {beta}-casein expression required both laminin signalling and a 'soft' extracellular matrix, as is the case in normal tissues in vivo, and biomimetic intracellular elasticity, as is the case in primary mammary epithelial organoids. Conversely, two hallmarks of breast cancer development, stiffening of the extracellular matrix and loss of laminin signalling, led to the loss of {beta}-casein expression and non-biomimetic intracellular elasticity. Our data indicate that tissue-specific gene expression is controlled by both the tissues unique biochemical milieu and mechanical properties, processes involved in maintenance of tissue integrity and protection against tumorigenesis.
Date: October 20, 2008
Creator: Alcaraz, Jordi; Xu, Ren; Mori, Hidetoshi; Nelson, Celeste M.; Mroue, Rana; Spencer, Virginia A. et al.
Partner: UNT Libraries Government Documents Department

Homology with vesicle fusion mediator syntaxin-1a predicts determinants ofepimorphin/syntaxin-2 function in mammary epithelial morphogenesis

Description: We have shown that branching morphogenesis of mammary ductal structures requires the action of the morphogen epimorphin/syntaxin-2. Epimorphin, originally identified as an extracellular molecule, is identical to syntaxin-2, an intracellular molecule that is a member of the extensively investigated syntaxin family of proteins that mediate vesicle trafficking. We show here that although epimorphin/syntaxin-2 is highly homologous to syntaxin-1a, only epimorphin/syntaxin-2 can stimulate mammary branching morphogenesis. We construct a homology model of epimorphin/syntaxin-2 based on the published structure of syntaxin-1a, and we use this model to identify the structural motif responsible for the morphogenic activity. We identify four residues located within the cleft between helices B and C that differ between syntaxin-1a and epimorphin/syntaxin-2; through site-directed mutagenesis of these four amino acids, we confer the properties of epimorphin for cell adhesion, gene activation, and branching morphogenesis onto the inactive syntaxin-1a template. These results provide a dramatic demonstration of the use of structural information about one molecule to define a functional motif of a second molecule that is related at the sequence level but highly divergent functionally.
Date: June 3, 2009
Creator: Chen, Connie S.; Nelson, Celeste M.; Khauv, Davitte; Bennett, Simone; Radisky, Evette S.; Hirai, Yohei et al.
Partner: UNT Libraries Government Documents Department

Mechanism of Akt1 inhibition of breast cancer cell invasionreveals a protumorigenic role for TSC2

Description: Akt1 is frequently upregulated in human tumors, and has been shown to accelerate cell proliferation and to suppress programmed cell death; consequently, inhibiting the activity of Akt1 has been seen as an attractive target for therapeutic intervention. Paradoxically, hyperactivation of the Akt1 oncogene can also prevent the invasive behavior that underlies progression to metastasis. Here we show that overexpression of activated myr-Akt1 in human breast cancer cells phosphorylates and thereby targets the tumor suppressor tuberous sclerosis complex 2 (TSC2) for degradation, leading to reduced Rho-GTPase activity, decreased actin stress fibers and focal adhesions, and reduced motility and invasion. Overexpression of TSC2 rescues the migration phenotype of myr-Akt1-expressing tumor cells, and high levels of TSC2 in breast cancer patients correlate with increased metastasis and reduced survival. These data indicate that the functional properties of genes designated as oncogenes or tumor suppressor genes depends on the context of the cell type and the tissues studied, and suggest the need for caution in designing therapies targeting the function of individual genes in epithelial tissues.
Date: February 7, 2006
Creator: Liu, Hong; Radisky, Derek C.; Nelson, Celeste M.; Zhang, Hui; Fata, Jimmie; Roth, Richard A. et al.
Partner: UNT Libraries Government Documents Department