@article {241, title = {Rapid disorganization of mechanically interacting systems of mammary acini.}, journal = {Proc Natl Acad Sci U S A}, volume = {111}, year = {2014}, month = {2014 Jan 14}, pages = {658-63}, abstract = {

Cells and multicellular structures can mechanically align and concentrate fibers in their ECM environment and can sense and respond to mechanical cues by differentiating, branching, or disorganizing. Here we show that mammary acini with compromised structural integrity can interconnect by forming long collagen lines. These collagen lines then coordinate and accelerate transition to an invasive phenotype. Interacting acini begin to disorganize within 12.5 \± 4.7 h in a spatially coordinated manner, whereas acini that do not interact mechanically with other acini disorganize more slowly (in 21.8 \± 4.1 h) and to a lesser extent (P \< 0.0001). When the directed mechanical connections between acini were cut with a laser, the acini reverted to a slowly disorganizing phenotype. When acini were fully mechanically isolated from other acini and also from the bulk gel by box-cuts with a side length \<900 μm, transition to an invasive phenotype was blocked in 20 of 20 experiments, regardless of waiting time. Thus, pairs or groups of mammary acini can interact mechanically over long distances through the collagen matrix, and these directed mechanical interactions facilitate transition to an invasive phenotype.

}, keywords = {Acinar Cells, Breast Neoplasms, Cell Communication, Cell Line, Tumor, Cell Separation, Collagen, Escherichia coli, Female, Humans, Kaplan-Meier Estimate, Mammary Glands, Human, Microscopy, Atomic Force, Microscopy, Electron, Scanning, Microscopy, Fluorescence}, issn = {1091-6490}, doi = {10.1073/pnas.1311312110}, author = {Shi, Quanming and Ghosh, Rajarshi P and Engelke, Hanna and Rycroft, Chris H and Cassereau, Luke and Sethian, James A and Weaver, Valerie M and Liphardt, Jan T} } @article {246, title = {Stromally derived lysyl oxidase promotes metastasis of transforming growth factor-β-deficient mouse mammary carcinomas.}, journal = {Cancer Res}, volume = {73}, year = {2013}, month = {2013 Sep 1}, pages = {5336-46}, abstract = {

The tumor stromal environment can dictate many aspects of tumor progression. A complete understanding of factors driving stromal activation and their role in tumor metastasis is critical to furthering research with the goal of therapeutic intervention. Polyoma middle T-induced mammary carcinomas lacking the type II TGF-β receptor (PyMT(mgko)) are highly metastatic compared with control PyMT-induced carcinomas (PyMT(fl/fl)). We hypothesized that the PyMT(mgko)-activated stroma interacts with carcinoma cells to promote invasion and metastasis. We show that the extracellular matrix associated with PyMT(mgko) tumors is stiffer and has more fibrillar collagen and increased expression of the collagen crosslinking enzyme lysyl oxidase (LOX) compared with PyMT(fl/fl) mammary carcinomas. Inhibition of LOX activity in PyMT(mgko) mice had no effect on tumor latency and size, but significantly decreased tumor metastasis through inhibition of tumor cell intravasation. This phenotype was associated with a decrease in keratin 14-positive myoepithelial cells in PyMT(mgko) tumors following LOX inhibition as well as a decrease in focal adhesion formation. Interestingly, the primary source of LOX was found to be activated fibroblasts. LOX expression in these fibroblasts can be driven by myeloid cell-derived TGF-β, which is significantly linked to human breast cancer. Overall, stromal expansion in PyMT(mgko) tumors is likely caused through the modulation of immune cell infiltrates to promote fibroblast activation. This feeds back to the epithelium to promote metastasis by modulating phenotypic characteristics of basal cells. Our data indicate that epithelial induction of microenvironmental changes can play a significant role in tumorigenesis and attenuating these changes can inhibit metastasis. Cancer Res; 73(17); 5336-46. \©2013 AACR.

}, keywords = {Animals, Carcinogenesis, Collagen, Enzyme Inhibitors, Female, Fibroblasts, Focal Adhesion Kinase 1, Humans, In Situ Hybridization, Keratin-14, Lung Neoplasms, Mammary Neoplasms, Experimental, Mice, Mice, Transgenic, Microscopy, Atomic Force, Myeloid Cells, Phosphorylation, Protein-Lysine 6-Oxidase, Protein-Serine-Threonine Kinases, Receptors, Transforming Growth Factor beta, Signal Transduction, Stromal Cells, Transforming Growth Factor beta}, issn = {1538-7445}, doi = {10.1158/0008-5472.CAN-13-0012}, author = {Pickup, Michael W and Laklai, Hanane and Acerbi, Irene and Owens, Philip and Gorska, Agnieszka E and Chytil, Anna and Aakre, Mary and Weaver, Valerie M and Moses, Harold L} } @article {261, title = {YAP forces fibroblasts to feel the tension.}, journal = {Nat Cell Biol}, volume = {15}, year = {2013}, month = {2013 Jun}, pages = {570-2}, abstract = {

Cancer-associated fibroblasts (CAFs) may contribute to tissue tension and cancer progression by increasing extracellular matrix (ECM) deposition and remodelling. However, how CAFs become activated and their roles in tumour mechanics have remained unclear. YAP is now identified as a tension-stimulated CAF activator that promotes malignancy through a mechanically reinforced feed-forward loop.

}, keywords = {Adaptor Proteins, Signal Transducing, Animals, Breast Neoplasms, Female, Fibroblasts, Humans, Mechanotransduction, Cellular, Phosphoproteins}, issn = {1476-4679}, doi = {10.1038/ncb2777}, author = {Maller, Ori and DuFort, Christopher C and Weaver, Valerie M} } @article {301, title = {In situ force mapping of mammary gland transformation.}, journal = {Integr Biol (Camb)}, volume = {3}, year = {2011}, month = {2011 Sep}, pages = {910-21}, abstract = {

Tumor progression is characterized by an incremental stiffening of the tissue. The importance of tissue rigidity to cancer is appreciated, yet the contribution of specific tissue elements to tumor stiffening and their physiological significance remains unclear. We performed high-resolution atomic force microscopy indentation in live and snap-frozen fluorescently labeled mammary tissues to explore the origin of the tissue stiffening associated with mammary tumor development in PyMT mice. The tumor epithelium, the tumor-associated vasculature and the extracellular matrix all contributed to mammary gland stiffening as it transitioned from normal to invasive carcinoma. Consistent with the concept that extracellular matrix stiffness modifies cell tension, we found that isolated transformed mammary epithelial cells were intrinsically stiffer than their normal counterparts but that the malignant epithelium in situ was far stiffer than isolated breast tumor cells. Moreover, using an in situ vitrification approach, we determined that the extracellular matrix adjacent to the epithelium progressively stiffened as tissue evolved from normal through benign to an invasive state. Importantly, we also noted that there was significant mechanical heterogeneity within the transformed tissue both in the epithelium and the tumor-associated neovasculature. The vascular bed within the tumor core was substantially stiffer than the large patent vessels at the invasive front that are surrounded by the stiffest extracellular matrix. These findings clarify the contribution of individual mammary gland tissue elements to the altered biomechanical landscape of cancerous tissues and emphasize the importance of studying cancer cell evolution under conditions that preserve native interactions.

}, keywords = {Animals, Bioengineering, Biomechanical Phenomena, Biophysical Phenomena, Cell Transformation, Neoplastic, Extracellular Matrix, Female, Mammary Glands, Animal, Mammary Neoplasms, Experimental, Mammary Tumor Virus, Mouse, Mice, Mice, Transgenic, Microscopy, Atomic Force, Neoplasm Invasiveness, Retroviridae Infections, Tensile Strength, Tumor Virus Infections, Vitrification}, issn = {1757-9708}, doi = {10.1039/c1ib00043h}, author = {Lopez, Jose I and Kang, Inkyung and You, Weon-Kyoo and McDonald, Donald M and Weaver, Valerie M} } @article {321, title = {Tumor microenvironment and progression.}, journal = {J Surg Oncol}, volume = {103}, year = {2011}, month = {2011 May 1}, pages = {468-74}, abstract = {

Tumor blood vessels are heterogeneous, of at least six distinct types, are induced primarily by vascular endothelial growth factor-A (VEGF-A), and provide a potentially useful therapeutic target. Breast cancer is characterized by changes in the microenvironment that result in altered tensional homeostasis. Also, breast cancers arise as the result of epigenetic as well as genetic changes. Tumor blood vessel pericytes result, in part, from bone marrow precursor cells, and VEGF is a negative regulator of glioblastoma tumor cell invasion.

}, keywords = {Angiogenesis Inhibitors, Breast Neoplasms, Disease Progression, Female, Humans, Molecular Targeted Therapy, Neoplasm Invasiveness, Neoplasms, Neovascularization, Pathologic, Tumor Microenvironment, Vascular Endothelial Growth Factor A}, issn = {1096-9098}, doi = {10.1002/jso.21709}, author = {Dvorak, Harold F and Weaver, Valerie M and Tlsty, Thea D and Bergers, Gabriele} } @article {351, title = {HOXA9 regulates BRCA1 expression to modulate human breast tumor phenotype.}, journal = {J Clin Invest}, volume = {120}, year = {2010}, month = {2010 May}, pages = {1535-50}, abstract = {

Breast cancer 1, early onset (BRCA1) expression is often reduced in sporadic breast tumors, even in the absence of BRCA1 genetic modifications, but the molecular basis for this is unknown. In this study, we identified homeobox A9 (HOXA9) as a gene frequently downregulated in human breast cancers and tumor cell lines and noted that reduced HOXA9 transcript levels associated with tumor aggression, metastasis, and patient mortality. Experiments revealed that loss of HOXA9 promoted mammary epithelial cell growth and survival and perturbed tissue morphogenesis. Restoring HOXA9 expression repressed growth and survival and inhibited the malignant phenotype of breast cancer cells in culture and in a xenograft mouse model. Molecular studies showed that HOXA9 restricted breast tumor behavior by directly modulating the expression of BRCA1. Indeed, ectopic expression of wild-type BRCA1 phenocopied the tumor suppressor function of HOXA9, and reducing BRCA1 levels or function inhibited the antitumor activity of HOXA9. Consistently, HOXA9 expression correlated with BRCA1 in clinical specimens and with tumor aggression in patients lacking estrogen receptor/progesterone receptor expression in their breast tissue. These findings indicate that HOXA9 restricts breast tumor aggression by modulating expression of the tumor suppressor gene BRCA1, which we believe provides an explanation for the loss of BRCA1 expression in sporadic breast tumors in the absence of BRCA1 genetic modifications.

}, keywords = {Adult, Animals, BRCA1 Protein, Breast Neoplasms, Female, Gene Expression Regulation, Neoplastic, Homeodomain Proteins, Humans, Mice, Middle Aged, Models, Genetic, Neoplasm Transplantation, Phenotype, Receptors, Estrogen, Receptors, Progesterone, Treatment Outcome}, issn = {1558-8238}, doi = {10.1172/JCI39534}, author = {Gilbert, Penney M and Mouw, Janna K and Unger, Meredith A and Lakins, Johnathon N and Gbegnon, Mawuse K and Clemmer, Virginia B and Benezra, Miriam and Licht, Jonathan D and Boudreau, Nancy J and Tsai, Kelvin K C and Welm, Alana L and Feldman, Michael D and Weber, Barbara L and Weaver, Valerie M} } @article {356, title = {SWI/SNF chromatin remodeling enzyme ATPases promote cell proliferation in normal mammary epithelial cells.}, journal = {J Cell Physiol}, volume = {223}, year = {2010}, month = {2010 Jun}, pages = {667-78}, abstract = {

The ATPase subunits of the SWI/SNF chromatin remodeling enzymes, Brahma (BRM) and Brahma-related gene 1 (BRG1), can induce cell cycle arrest in BRM and BRG1 deficient tumor cell lines, and mice heterozygous for Brg1 are pre-disposed to breast tumors, implicating loss of BRG1 as a mechanism for unregulated cell proliferation. To test the hypothesis that loss of BRG1 can contribute to breast cancer, we utilized RNA interference to reduce the amounts of BRM or BRG1 protein in the nonmalignant mammary epithelial cell line, MCF-10A. When grown in reconstituted basement membrane (rBM), these cells develop into acini that resemble the lobes of normal breast tissue. Contrary to expectations, knockdown of either BRM or BRG1 resulted in an inhibition of cell proliferation in monolayer cultures. This inhibition was strikingly enhanced in three-dimensional rBM culture, although some BRM-depleted cells were later able to resume proliferation. Cells did not arrest in any specific stage of the cell cycle; instead, the cell cycle length increased by approximately 50\%. Thus, SWI/SNF ATPases promote cell cycle progression in nonmalignant mammary epithelial cells.

}, keywords = {Adenosine Triphosphatases, Basement Membrane, Cell Cycle, Cell Line, Cell Proliferation, Chromatin Assembly and Disassembly, DNA Helicases, Doxycycline, Epithelial Cells, Female, Gene Knockdown Techniques, Humans, Mammary Glands, Human, Nuclear Proteins, Protein Subunits, RNA, Small Interfering, RNA, Small Nucleolar, Transcription Factors, Up-Regulation}, issn = {1097-4652}, doi = {10.1002/jcp.22072}, author = {Cohet, Nathalie and Stewart, Kathleen M and Mudhasani, Rajini and Asirvatham, Ananthi J and Mallappa, Chandrashekara and Imbalzano, Karen M and Weaver, Valerie M and Imbalzano, Anthony N and Nickerson, Jeffrey A} } @article {381, title = {CpG island tumor suppressor promoter methylation in non-BRCA-associated early mammary carcinogenesis.}, journal = {Cancer Epidemiol Biomarkers Prev}, volume = {18}, year = {2009}, month = {2009 Mar}, pages = {901-14}, abstract = {

BACKGROUND: Only 5\% of all breast cancers are the result of BRCA1/2 mutations. Methylation silencing of tumor suppressor genes is well described in sporadic breast cancer; however, its role in familial breast cancer is not known.

METHODS: CpG island promoter methylation was tested in the initial random periareolar fine-needle aspiration sample from 109 asymptomatic women at high risk for breast cancer. Promoter methylation targets included RARB (M3 and M4), ESR1, INK4a/ARF, BRCA1, PRA, PRB, RASSF1A, HIN-1, and CRBP1.

RESULTS: Although the overall frequency of CpG island promoter methylation events increased with age (P\<0.0001), no specific methylation event was associated with age. In contrast, CpG island methylation of RARB M4 (P=0.051), INK4a/ARF (P=0.042), HIN-1 (P=0.044), and PRA (P=0.032), as well as the overall frequency of methylation events (P=0.004), was associated with abnormal Masood cytology. The association between promoter methylation and familial breast cancer was tested in 40 unaffected premenopausal women in our cohort who underwent BRCA1/2 mutation testing. Women with BRCA1/2 mutations had a low frequency of CpG island promoter methylation (15 of 15 women had

CONCLUSIONS: This is the first evidence of CpG island methylation of tumor suppressor gene promoters in non-BRCA1/2 familial breast cancer.

}, keywords = {Biopsy, Fine-Needle, Breast Neoplasms, Chi-Square Distribution, CpG Islands, Cyclin-Dependent Kinase Inhibitor p16, Cytokines, DNA Methylation, Female, Genes, BRCA1, Genes, BRCA2, Genes, Tumor Suppressor, Humans, Mutation, Polymerase Chain Reaction, Premenopause, Promoter Regions, Genetic, Receptors, Progesterone, Receptors, Retinoic Acid, Risk, Risk Assessment, Statistics, Nonparametric, Tumor Suppressor Proteins}, issn = {1055-9965}, doi = {10.1158/1055-9965.EPI-08-0875}, author = {Vasilatos, Shauna N and Broadwater, Gloria and Barry, William T and Baker, Joseph C and Lem, Siya and Dietze, Eric C and Bean, Gregory R and Bryson, Andrew D and Pilie, Patrick G and Goldenberg, Vanessa and Skaar, David and Paisie, Carolyn and Torres-Hernandez, Alejandro and Grant, Tracey L and Wilke, Lee G and Ibarra-Drendall, Catherine and Ostrander, Julie H and D{\textquoteright}Amato, Nicholas C and Zalles, Carola and Jirtle, Randy and Weaver, Valerie M and Seewaldt, Victoria L} } @article {366, title = {Matrix crosslinking forces tumor progression by enhancing integrin signaling.}, journal = {Cell}, volume = {139}, year = {2009}, month = {2009 Nov 25}, pages = {891-906}, abstract = {

Tumors are characterized by extracellular matrix (ECM) remodeling and stiffening. The importance of ECM remodeling to cancer is appreciated; the relevance of stiffening is less clear. We found that breast tumorigenesis is accompanied by collagen crosslinking, ECM stiffening, and increased focal adhesions. Induction of collagen crosslinking stiffened the ECM, promoted focal adhesions, enhanced PI3 kinase (PI3K) activity, and induced the invasion of an oncogene-initiated epithelium. Inhibition of integrin signaling repressed the invasion of a premalignant epithelium into a stiffened, crosslinked ECM and forced integrin clustering promoted focal adhesions, enhanced PI3K signaling, and induced the invasion of a premalignant epithelium. Consistently, reduction of lysyl oxidase-mediated collagen crosslinking prevented MMTV-Neu-induced fibrosis, decreased focal adhesions and PI3K activity, impeded malignancy, and lowered tumor incidence. These data show how collagen crosslinking can modulate tissue fibrosis and stiffness to force focal adhesions, growth factor signaling and breast malignancy.

}, keywords = {Aging, Animals, Breast Neoplasms, Collagen, Epidermal Growth Factor, Extracellular Matrix, Female, Fibrosis, Genes, ras, Humans, Integrins, Mammary Glands, Human, Mice, Mice, Inbred BALB C, Protein-Lysine 6-Oxidase, Signal Transduction}, issn = {1097-4172}, doi = {10.1016/j.cell.2009.10.027}, author = {Levental, Kandice R and Yu, Hongmei and Kass, Laura and Lakins, Johnathon N and Egeblad, Mikala and Erler, Janine T and Fong, Sheri F T and Csiszar, Katalin and Giaccia, Amato and Weninger, Wolfgang and Yamauchi, Mitsuo and Gasser, David L and Weaver, Valerie M} } @article {431, title = {Mammary epithelial cell: influence of extracellular matrix composition and organization during development and tumorigenesis.}, journal = {Int J Biochem Cell Biol}, volume = {39}, year = {2007}, month = {2007}, pages = {1987-94}, abstract = {

Stromal-epithelial interactions regulate mammary gland development and are critical for the maintenance of tissue homeostasis. The extracellular matrix, which is a proteinaceous component of the stroma, regulates mammary epithelial growth, survival, migration and differentiation through a repertoire of transmembrane receptors, of which integrins are the best characterized. Integrins modulate cell fate by reciprocally transducing biochemical and biophysical cues between the cell and the extracellular matrix, facilitating processes such as embryonic branching morphogenesis and lactation in the mammary gland. During breast development and cancer progression, the extracellular matrix is dynamically altered such that its composition, turnover, processing and orientation change dramatically. These modifications influence mammary epithelial cell shape, and modulate growth factor and hormonal responses to regulate processes including branching morphogenesis and alveolar differentiation. Malignant transformation of the breast is also associated with significant matrix remodeling and a progressive stiffening of the stroma that can enhance mammary epithelial cell growth, perturb breast tissue organization, and promote cell invasion and survival. In this review, we discuss the role of stromal-epithelial interactions in normal and malignant mammary epithelial cell behavior. We specifically focus on how dynamic modulation of the biochemical and biophysical properties of the extracellular matrix elicit a dialogue with the mammary epithelium through transmembrane integrin receptors to influence tissue morphogenesis, homeostasis and malignant transformation.

}, keywords = {Animals, Cell Lineage, Cell Transformation, Neoplastic, Epithelial Cells, Extracellular Matrix, Female, Humans, Mammary Glands, Human, Neoplasms}, issn = {1357-2725}, doi = {10.1016/j.biocel.2007.06.025}, author = {Kass, Laura and Erler, Janine T and Dembo, Micah and Weaver, Valerie M} } @article {531, title = {beta4 integrin-dependent formation of polarized three-dimensional architecture confers resistance to apoptosis in normal and malignant mammary epithelium.}, journal = {Cancer Cell}, volume = {2}, year = {2002}, month = {2002 Sep}, pages = {205-16}, abstract = {

Tumor cells can evade chemotherapy by acquiring resistance to apoptosis. We investigated the molecular mechanism whereby malignant and nonmalignant mammary epithelial cells become insensitive to apoptosis. We show that regardless of growth status, formation of polarized, three-dimensional structures driven by basement membrane confers protection to apoptosis in both nonmalignant and malignant mammary epithelial cells. By contrast, irrespective of their malignant status, nonpolarized structures are sensitive to induction of apoptosis. Resistance to apoptosis requires ligation of beta4 integrins, which regulates tissue polarity, hemidesmosome formation, and NFkappaB activation. Expression of beta4 integrin that lacks the hemidesmosome targeting domain interferes with tissue polarity and NFkappaB activation and permits apoptosis. These results indicate that integrin-induced polarity may drive tumor cell resistance to apoptosis-inducing agents via effects on NFkappaB.

}, keywords = {Apoptosis, Basement Membrane, Breast Neoplasms, Cell Polarity, Epithelial Cells, Extracellular Matrix, Female, Gene Expression Regulation, Neoplastic, Humans, Integrin beta4, NF-kappa B, Tumor Cells, Cultured}, issn = {1535-6108}, author = {Weaver, Valerie M and Leli{\`e}vre, Sophie and Lakins, Johnathon N and Chrenek, Micah A and Jones, Jonathan C R and Giancotti, Filippo and Werb, Zena and Bissell, Mina J} } @article {526, title = {The organizing principle: microenvironmental influences in the normal and malignant breast.}, journal = {Differentiation}, volume = {70}, year = {2002}, month = {2002 Dec}, pages = {537-46}, abstract = {

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.

}, keywords = {Apoptosis, Breast, Breast Neoplasms, Coculture Techniques, Female, Humans, Signal Transduction}, issn = {0301-4681}, doi = {10.1046/j.1432-0436.2002.700907.x}, author = {Bissell, Mina J and Radisky, Derek C and Rizki, Aylin and Weaver, Valerie M and Petersen, Ole W} } @article {541, title = {Tumour-stromal interactions. Integrins and cell adhesions as modulators of mammary cell survival and transformation.}, journal = {Breast Cancer Res}, volume = {3}, year = {2001}, month = {2001}, pages = {224-9}, abstract = {

Stromal-epithelial interactions modulate mammary epithelial cell (MEC) growth and apoptosis by influencing cell adhesion and tissue organization. Perturbations in the mammary stroma and cell adhesion characterize breast tumors and underlie the altered tissue organization, disrupted tissue homeostasis and enhanced survival phenotype of the disease. Apoptosis resistance likely arises during malignant transformation via genetic and epigenetic modification of cell adhesion pathways induced by a changing tissue microenvironment. Acquisition of adhesion-linked survival networks that enhance MEC viability in the absence of basement membrane interactions probably promote malignant transformation, and may render breast tumors sufficiently resistant to exogenous apoptotic stimuli to generate multidrug resistance.

}, keywords = {Apoptosis, Basement Membrane, Breast Neoplasms, Cell Adhesion Molecules, Cell Communication, Cell Differentiation, Cell Survival, Cell Transformation, Neoplastic, Drug Resistance, Multiple, Epithelial Cells, Female, Gene Expression Regulation, Neoplastic, Humans, Integrins, Stromal Cells}, issn = {1465-5411}, author = {Chrenek, M A and Wong, P and Weaver, V M} } @article {551, title = {Reciprocal interactions between beta1-integrin and epidermal growth factor receptor in three-dimensional basement membrane breast cultures: a different perspective in epithelial biology.}, journal = {Proc Natl Acad Sci U S A}, volume = {95}, year = {1998}, month = {1998 Dec 8}, pages = {14821-6}, abstract = {

Anchorage and growth factor independence are cardinal features of the transformed phenotype. Although it is logical that the two pathways must be coregulated in normal tissues to maintain homeostasis, this has not been demonstrated directly. We showed previously that down-modulation of beta1-integrin signaling reverted the malignant behavior of a human breast tumor cell line (T4-2) derived from phenotypically normal cells (HMT-3522) and led to growth arrest in a three-dimensional (3D) basement membrane assay in which the cells formed tissue-like acini (14). Here, we show that there is a bidirectional cross-modulation of beta1-integrin and epidermal growth factor receptor (EGFR) signaling via the mitogen-activated protein kinase (MAPK) pathway. The reciprocal modulation does not occur in monolayer (2D) cultures. Antibody-mediated inhibition of either of these receptors in the tumor cells, or inhibition of MAPK kinase, induced a concomitant down-regulation of both receptors, followed by growth-arrest and restoration of normal breast tissue morphogenesis. Cross-modulation and tissue morphogenesis were associated with attenuation of EGF-induced transient MAPK activation. To specifically test EGFR and beta1-integrin interdependency, EGFR was overexpressed in nonmalignant cells, leading to disruption of morphogenesis and a compensatory up-regulation of beta1-integrin expression, again only in 3D. Our results indicate that when breast cells are spatially organized as a result of contact with basement membrane, the signaling pathways become coupled and bidirectional. They further explain why breast cells fail to differentiate in monolayer cultures in which these events are mostly uncoupled. Moreover, in a subset of tumor cells in which these pathways are misregulated but functional, the cells could be \"normalized\" by manipulating either pathway.

}, keywords = {Antigens, CD29, Basement Membrane, Breast, Cell Line, Epithelial Cells, Female, Humans, Protein Binding, Protein Conformation, Receptor, Epidermal Growth Factor}, issn = {0027-8424}, author = {Wang, F and Weaver, V M and Petersen, O W and Larabell, C A and Dedhar, S and Briand, P and Lupu, R and Bissell, M J} } @article {546, title = {Structural cues from the tissue microenvironment are essential determinants of the human mammary epithelial cell phenotype.}, journal = {J Mammary Gland Biol Neoplasia}, volume = {3}, year = {1998}, month = {1998 Apr}, pages = {201-13}, abstract = {

Historically, the study of normal human breast function and breast disorders has been significantly impaired by limitations inherent to available model systems. Recent improvements in human breast epithelial cell lines and three-dimensional (3-D)3 culture systems have contributed to the development of in vitro model systems that recapitulate differentiated epithelial cell phenotypes with remarkable fidelity. Molecular characterization of these human breast cell models has demonstrated that normal breast epithelial cell behavior is determined in part by the precise interplay that exists between a cell and its surrounding microenvironment. Recent functional studies of integrins in a human model system provide evidence to support the idea that the structural stability afforded by integrin-mediated cell-extracellular matrix interactions is an important determinant of normal cellular behavior, and that alterations in tissue structure can give rise to tumorigenic progression.

}, keywords = {Breast, Breast Neoplasms, Cell Line, Epithelial Cells, Extracellular Matrix, Female, Humans, Integrins, Models, Biological}, issn = {1083-3021}, author = {Schmeichel, K L and Weaver, V M and Bissell, M J} } @article {556, title = {Tissue phenotype depends on reciprocal interactions between the extracellular matrix and the structural organization of the nucleus.}, journal = {Proc Natl Acad Sci U S A}, volume = {95}, year = {1998}, month = {1998 Dec 8}, pages = {14711-6}, abstract = {

What determines the nuclear organization within a cell and whether this organization itself can impose cellular function within a tissue remains unknown. To explore the relationship between nuclear organization and tissue architecture and function, we used a model of human mammary epithelial cell acinar morphogenesis. When cultured within a reconstituted basement membrane (rBM), HMT-3522 cells form polarized and growth-arrested tissue-like acini with a central lumen and deposit an endogenous BM. We show that rBM-induced morphogenesis is accompanied by relocalization of the nuclear matrix proteins NuMA, splicing factor SRm160, and cell cycle regulator Rb. These proteins had distinct distribution patterns specific for proliferation, growth arrest, and acini formation, whereas the distribution of the nuclear lamina protein, lamin B, remained unchanged. NuMA relocalized to foci, which coalesced into larger assemblies as morphogenesis progressed. Perturbation of histone acetylation in the acini by trichostatin A treatment altered chromatin structure, disrupted NuMA foci, and induced cell proliferation. Moreover, treatment of transiently permeabilized acini with a NuMA antibody led to the disruption of NuMA foci, alteration of histone acetylation, activation of metalloproteases, and breakdown of the endogenous BM. These results experimentally demonstrate a dynamic interaction between the extracellular matrix, nuclear organization, and tissue phenotype. They further show that rather than passively reflecting changes in gene expression, nuclear organization itself can modulate the cellular and tissue phenotype.

}, keywords = {Cell Nucleus, Extracellular Matrix, Extracellular Matrix Proteins, Female, Gene Expression Regulation, Humans, Morphogenesis, Nuclear Proteins, Tumor Cells, Cultured}, issn = {0027-8424}, author = {Leli{\`e}vre, S A and Weaver, V M and Nickerson, J A and Larabell, C A and Bhaumik, A and Petersen, O W and Bissell, M J} } @article {561, title = {Reversion of the malignant phenotype of human breast cells in three-dimensional culture and in vivo by integrin blocking antibodies.}, journal = {J Cell Biol}, volume = {137}, year = {1997}, month = {1997 Apr 7}, pages = {231-45}, abstract = {

In a recently developed human breast cancer model, treatment of tumor cells in a 3-dimensional culture with inhibitory beta1-integrin antibody or its Fab fragments led to a striking morphological and functional reversion to a normal phenotype. A stimulatory beta1-integrin antibody proved to be ineffective. The newly formed reverted acini re-assembled a basement membrane and re-established E-cadherin-catenin complexes, and re-organized their cytoskeletons. At the same time they downregulated cyclin D1, upregulated p21(cip,wat-1), and stopped growing. Tumor cells treated with the same antibody and injected into nude mice had significantly reduced number and size of tumors in nude mice. The tissue distribution of other integrins was also normalized, suggesting the existence of intimate interactions between the different integrin pathways as well as adherens junctions. On the other hand, nonmalignant cells when treated with either alpha6 or beta4 function altering antibodies continued to grow, and had disorganized colony morphologies resembling the untreated tumor colonies. This shows a significant role of the alpha6/beta4 heterodimer in directing polarity and tissue structure. The observed phenotypes were reversible when the cells were disassociated and the antibodies removed. Our results illustrate that the extracellular matrix and its receptors dictate the phenotype of mammary epithelial cells, and thus in this model system the tissue phenotype is dominant over the cellular genotype.

}, keywords = {Animals, Antibodies, Monoclonal, Antigens, CD, Antigens, CD29, Basement Membrane, Binding, Competitive, Breast Neoplasms, Cell Division, Extracellular Matrix, Female, Fluorescent Antibody Technique, Genotype, Humans, Immunoglobulin Fab Fragments, Integrin beta4, Mice, Phenotype, Rats, Signal Transduction, Transformation, Genetic, Tumor Cells, Cultured}, issn = {0021-9525}, author = {Weaver, V M and Petersen, O W and Wang, F and Larabell, C A and Briand, P and Damsky, C and Bissell, M J} }