@article {696, title = {A 3D tension bioreactor platform to study the interplay between ECM stiffness and tumor phenotype.}, journal = {J Biotechnol}, volume = {193}, year = {2015}, month = {2015 Jan 10}, pages = {66-9}, abstract = {

Extracellular matrix (ECM) structure, composition, and stiffness have profound effects on tissue development and pathologies such as cardiovascular disease and cancer. Accordingly, a variety of synthetic hydrogel systems have been designed to study the impact of ECM composition, density, mechanics, and topography on cell and tissue phenotype. However, these synthetic systems fail to accurately recapitulate the biological properties and structure of the native tissue ECM. Natural three dimensional (3D) ECM hydrogels, such as collagen or hyaluronic acid, feature many of the chemical and physical properties of tissue, yet, these systems have limitations including the inability to independently control biophysical properties such as stiffness and pore size. Here, we present a 3D tension bioreactor system that permits precise mechanical tuning of collagen hydrogel stiffness, while maintaining consistent composition and pore size. We achieve this by mechanically loading collagen hydrogels covalently-conjugated to a polydimethylsiloxane (PDMS) membrane to induce hydrogel stiffening. We validated the biological application of this system with oncogenically transformed mammary epithelial cell organoids embedded in a 3D collagen I hydrogel, either uniformly stiffened or calibrated to create a gradient of ECM stiffening, to visually demonstrate the impact of ECM stiffening on transformation and tumor cell invasion. As such, this bioreactor presents the first tunable 3D natural hydrogel system that is capable of independently assessing the role of ECM stiffness on tissue phenotype.

}, issn = {1873-4863}, doi = {10.1016/j.jbiotec.2014.11.008}, author = {Cassereau, Luke and Miroshnikova, Yekaterina A and Ou, Guanqing and Lakins, Johnathon and Weaver, Valerie M} } @article {721, title = {Human breast cancer invasion and aggression correlates with ECM stiffening and immune cell infiltration.}, journal = {Integr Biol (Camb)}, year = {2015}, month = {2015 May 11}, abstract = {

Tumors are stiff and data suggest that the extracellular matrix stiffening that correlates with experimental mammary malignancy drives tumor invasion and metastasis. Nevertheless, the relationship between tissue and extracellular matrix stiffness and human breast cancer progression and aggression remains unclear. We undertook a biophysical and biochemical assessment of stromal-epithelial interactions in noninvasive, invasive and normal adjacent human breast tissue and in breast cancers of increasingly aggressive subtype. Our analysis revealed that human breast cancer transformation is accompanied by an incremental increase in collagen deposition and a progressive linearization and thickening of interstitial collagen. The linearization of collagen was visualized as an overall increase in tissue birefringence and was most striking at the invasive front of the tumor where the stiffness of the stroma and cellular mechanosignaling were the highest. Amongst breast cancer subtypes we found that the stroma at the invasive region of the more aggressive Basal-like and Her2 tumor subtypes was the most heterogeneous and the stiffest when compared to the less aggressive luminal A and B subtypes. Intriguingly, we quantified the greatest number of infiltrating macrophages and the highest level of TGF beta signaling within the cells at the invasive front. We also established that stroma stiffness and the level of cellular TGF beta signaling positively correlated with each other and with the number of infiltrating tumor-activated macrophages, which was highest in the more aggressive tumor subtypes. These findings indicate that human breast cancer progression and aggression, collagen linearization and stromal stiffening are linked and implicate tissue inflammation and TGF beta.

}, issn = {1757-9708}, doi = {10.1039/c5ib00040h}, author = {Acerbi, I and Cassereau, L and Dean, I and Shi, Q and Au, A and Park, C and Chen, Y Y and Liphardt, J and Hwang, E S and Weaver, V M} } @article {761, title = {Monitoring developmental force distributions in reconstituted embryonic epithelia.}, journal = {Methods}, year = {2015}, month = {2015 Sep 2}, abstract = {

The way cells are organized within a tissue dictates how they sense and respond to extracellular signals, as cues are received and interpreted based on expression and organization of receptors, downstream signaling proteins, and transcription factors. Part of this microenvironmental context is the result of forces acting on the cell, including forces from other cells or from the cellular substrate or basement membrane. However, measuring forces exerted on and by cells is difficult, particularly in an in vivo context, and interpreting how forces affect downstream cellular processes poses an even greater challenge. Here, we present a simple method for monitoring and analyzing forces generated from cell collectives. We demonstrate the ability to generate traction force data from human embryonic stem cells grown in large organized epithelial sheets to determine the magnitude and organization of cell-ECM and cell-cell forces within a self-renewing colony. We show that this method can be used to measure forces in a dynamic hESC system and demonstrate the ability to map intracolony protein localization to force organization.

}, issn = {1095-9130}, doi = {10.1016/j.ymeth.2015.09.003}, author = {Przybyla, L and Lakins, J N and Sunyer, R and Trepat, X and Weaver, V M} } @article {671, title = {The cancer glycocalyx mechanically primes integrin-mediated growth and survival.}, journal = {Nature}, volume = {511}, year = {2014}, month = {2014 Jul 17}, pages = {319-25}, abstract = {

Malignancy is associated with altered expression of glycans and glycoproteins that contribute to the cellular glycocalyx. We constructed a glycoprotein expression signature, which revealed that metastatic tumours upregulate expression of bulky glycoproteins. A computational model predicted that these glycoproteins would influence transmembrane receptor spatial organization and function. We tested this prediction by investigating whether bulky glycoproteins in the glycocalyx promote a tumour phenotype in human cells by increasing integrin adhesion and signalling. Our data revealed that a bulky glycocalyx facilitates integrin clustering by funnelling active integrins into adhesions and altering integrin state by applying tension to matrix-bound integrins, independent of actomyosin contractility. Expression of large tumour-associated glycoproteins in non-transformed mammary cells promoted focal adhesion assembly and facilitated integrin-dependent growth factor signalling to support cell growth and survival. Clinical studies revealed that large glycoproteins are abundantly expressed on circulating tumour cells from patients with advanced disease. Thus, a bulky glycocalyx is a feature of tumour cells that could foster metastasis by mechanically enhancing cell-surface receptor function.

}, keywords = {Animals, Breast, Cell Line, Tumor, Cell Proliferation, Cell Survival, Fibroblasts, Glycocalyx, Glycoproteins, Humans, Immobilized Proteins, Integrins, Mice, Molecular Targeted Therapy, Mucin-1, Neoplasm Metastasis, Neoplasms, Neoplastic Cells, Circulating, Protein Binding, Receptors, Cell Surface}, issn = {1476-4687}, doi = {10.1038/nature13535}, author = {Paszek, Matthew J and DuFort, Christopher C and Rossier, Olivier and Bainer, Russell and Mouw, Janna K and Godula, Kamil and Hudak, Jason E and Lakins, Jonathon N and Wijekoon, Amanda C and Cassereau, Luke and Rubashkin, Matthew G and Magbanua, Mark J and Thorn, Kurt S and Davidson, Michael W and Rugo, Hope S and Park, John W and Hammer, Daniel A and Giannone, Gr{\'e}gory and Bertozzi, Carolyn R and Weaver, Valerie M} } @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 {226, title = {Tissue mechanics modulate microRNA-dependent PTEN expression to regulate malignant progression.}, journal = {Nat Med}, year = {2014}, month = {2014 Mar 16}, abstract = {

Tissue mechanics regulate development and homeostasis and are consistently modified in tumor progression. Nevertheless, the fundamental molecular mechanisms through which altered mechanics regulate tissue behavior and the clinical relevance of these changes remain unclear. We demonstrate that increased matrix stiffness modulates microRNA expression to drive tumor progression through integrin activation of β-catenin and MYC. Specifically, in human and mouse tissue, increased matrix stiffness induced miR-18a to reduce levels of the tumor suppressor phosphatase and tensin homolog (PTEN), both directly and indirectly by decreasing levels of homeobox A9 (HOXA9). Clinically, extracellular matrix stiffness correlated directly and significantly with miR-18a expression in human breast tumor biopsies. miR-18a expression was highest in basal-like breast cancers in which PTEN and HOXA9 levels were lowest, and high miR-18a expression predicted poor prognosis in patients with luminal breast cancers. Our findings identify a mechanically regulated microRNA circuit that can promote malignancy and suggest potential prognostic roles for HOXA9 and miR-18a levels in stratifying patients with luminal breast cancers.

}, issn = {1546-170X}, doi = {10.1038/nm.3497}, author = {Mouw, Janna K and Yui, Yoshihiro and Damiano, Laura and Bainer, Russell O and Lakins, Johnathon N and Acerbi, Irene and Ou, Guanqing and Wijekoon, Amanda C and Levental, Kandice R and Gilbert, Penney M and Hwang, E Shelley and Chen, Yunn-Yi and Weaver, Valerie M} } @article {251, title = {Collagen architecture in pregnancy-induced protection from breast cancer.}, journal = {J Cell Sci}, volume = {126}, year = {2013}, month = {2013 Sep 15}, pages = {4108-10}, abstract = {

The reduction in breast cancer risk attributed to early-age pregnancy is mediated in part by changes in the mammary epithelium. Here, we address the role of the mammary stroma in this protection. Utilizing tumor cells capable of transitioning from indolent to proliferative or invasive states, we demonstrate that mammary extracellular matrix (ECM) from parous rats (parous matrix) decreases tumor growth and impedes cellular phenotypes associated with tumor cell invasion compared with that observed using nulliparous matrix. Proteomic analysis identifies an increased abundance of collagen I in parous matrix, an observation extended to breast tissue of parous women. Given the pro-tumorigenic attributes of fibrillar collagen, these results were unexpected. Second-harmonic generation imaging and atomic force microscopy revealed that the abundant collagen observed in the mammary glands of parous rats is less linearized and associated with a decrease in stromal stiffness, implicating collagen organization and stiffness in parity-induced protection. Using 3D cell culture models, we demonstrate that linearized (fibrillar) collagen I induces cellular phenotypes consistent with an invasive behavior in mammary tumor cells and alters the subcellular distribution of β1 integrin. Conversely, high-density non-fibrillar collagen I induces tumor-suppressive attributes, including increases in junctional E-cadherin in tumor cells, upregulation of genes encoding components of cell-cell junctions, and downregulation of mesenchymal-specific and metalloproteinase-encoding genes. These data show that collagen organization, rather than density alone, is a key contributor to the invasive phenotype. Furthermore, our data show that parity alters the composition and organization of mammary ECM, particularly fibrillar collagen, in a manner consistent with tumor suppression.

}, issn = {1477-9137}, doi = {10.1242/jcs.121590}, author = {Maller, Ori and Hansen, Kirk C and Lyons, Traci R and Acerbi, Irene and Weaver, Valerie M and Prekeris, Rytis and Tan, Aik-Choon and Schedin, Pepper} } @article {276, title = {Molecular profiling of prostatic acinar morphogenesis identifies PDCD4 and KLF6 as tissue architecture-specific prognostic markers in prostate cancer.}, journal = {Am J Pathol}, volume = {182}, year = {2013}, month = {2013 Feb}, pages = {363-74}, abstract = {

Histopathological classification of human prostate cancer (PCA) relies on the morphological assessment of tissue specimens but has limited prognostic value. To address this deficiency, we performed comparative transcriptome analysis of human prostatic acini generated in a three-dimensional basement membrane that recapitulates the differentiated morphological characteristics and gene expression profile of a human prostate glandular epithelial tissue. We then applied an acinar morphogenesis-specific gene profile to two independent cohorts of patients with PCA (total n = 79) and found that those with tumors expressing this profile, which we designated acini-like tumors, had a significantly lower risk of postoperative relapse compared with those tumors with a lower correlation (hazard ratio, 0.078; log-rank test P = 0.009). Multivariate analyses showed superior prognostic prediction performance using this classification system compared with clinical criteria and Gleason scores. We prioritized the genes in this profile and identified programmed cell death protein 4 (PDCD4) and Kruppel-like factor 6 (KLF6) as critical regulators and surrogate markers of prostatic tissue architectures, which form a gene signature that robustly predicts clinical prognosis with a remarkable accuracy in several large series of PCA tumors (total n = 161; concordance index, 0.913 to 0.951). Thus, by exploiting the genomic program associated with prostate glandular differentiation, we identified acini-like PCA and related molecular markers that significantly enhance prognostic prediction of human PCA.

}, keywords = {Acinar Cells, Aged, Apoptosis Regulatory Proteins, Cell Differentiation, Epithelial Cells, Gene Expression Profiling, Gene Expression Regulation, Neoplastic, Humans, Kruppel-Like Transcription Factors, Male, Middle Aged, Morphogenesis, Organ Specificity, Prognosis, Prostate, Prostatic Neoplasms, Proto-Oncogene Proteins, Recurrence, RNA-Binding Proteins, Tumor Markers, Biological}, issn = {1525-2191}, doi = {10.1016/j.ajpath.2012.10.024}, author = {Li, Chi-Rong and Su, Jimmy J-M and Wang, Wei-Yu and Lee, Michael T-L and Wang, Ting-Yun and Jiang, Kuan-Ying and Li, Chein-Feng and Hsu, Jong-Ming and Chen, Chi-Kuan and Chen, Marcelo and Jiang, Shih-Sheng and Weaver, Valerie M and Tsai, Kelvin K-C} } @article {256, title = {Oncogenic targeting of BRM drives malignancy through C/EBPβ-dependent induction of α5 integrin.}, journal = {Oncogene}, year = {2013}, month = {2013 Jun 17}, abstract = {

Integrin expression and activity are altered in tumors, and aberrant integrin signaling promotes malignancy. However, how integrins become altered in tumors remains poorly understood. We discovered that oncogenic activation of MEK signaling induces cell growth and survival, and promotes the malignant phenotype of mammary epithelial cells (MECs) by increasing α5 integrin expression. We determined that MEK activates c-Myc to reduce the transcription of the SWI/SNF chromatin remodeling enzyme Brahma (BRM). Our studies revealed that reduced BRM expression and/or activity drives the malignant behavior of MECs by epigenetically promoting C/EBPβ expression to directly induce α5 integrin transcription. Consistently, we could show that restoring BRM levels normalized the malignant behavior of transformed MECs in culture and in vivo by preventing C/EBPβ-dependent α5 integrin transcription. Our findings identify a novel mechanism whereby oncogenic signaling promotes malignant transformation by regulating transcription of a key chromatin remodeling molecule that regulates integrin-dependent stromal-epithelial interactions.Oncogene advance online publication, 17 June 2013; doi:10.1038/onc.2013.220.

}, issn = {1476-5594}, doi = {10.1038/onc.2013.220}, author = {Damiano, L and Stewart, K M and Cohet, N and Mouw, J K and Lakins, J N and Debnath, J and Reisman, D and Nickerson, J A and Imbalzano, A N and Weaver, V M} } @article {271, title = {A physical sciences network characterization of non-tumorigenic and metastatic cells.}, journal = {Sci Rep}, volume = {3}, year = {2013}, month = {2013}, pages = {1449}, abstract = {

To investigate the transition from non-cancerous to metastatic from a physical sciences perspective, the Physical Sciences-Oncology Centers (PS-OC) Network performed molecular and biophysical comparative studies of the non-tumorigenic MCF-10A and metastatic MDA-MB-231 breast epithelial cell lines, commonly used as models of cancer metastasis. Experiments were performed in 20 laboratories from 12 PS-OCs. Each laboratory was supplied with identical aliquots and common reagents and culture protocols. Analyses of these measurements revealed dramatic differences in their mechanics, migration, adhesion, oxygen response, and proteomic profiles. Model-based multi-omics approaches identified key differences between these cells\&$\#$39; regulatory networks involved in morphology and survival. These results provide a multifaceted description of cellular parameters of two widely used cell lines and demonstrate the value of the PS-OC Network approach for integration of diverse experimental observations to elucidate the phenotypes associated with cancer metastasis.

}, keywords = {Cell Line, Tumor, Cell Movement, Cell Size, Cell Survival, Computer Simulation, Gene Expression Regulation, Neoplastic, Humans, Models, Biological, Neoplasm Metastasis, Neoplasm Proteins, Tumor Markers, Biological}, issn = {2045-2322}, doi = {10.1038/srep01449}, author = {Agus, David B and Alexander, Jenolyn F and Arap, Wadih and Ashili, Shashanka and Aslan, Joseph E and Austin, Robert H and Backman, Vadim and Bethel, Kelly J and Bonneau, Richard and Chen, Wei-Chiang and Chen-Tanyolac, Chira and Choi, Nathan C and Curley, Steven A and Dallas, Matthew and Damania, Dhwanil and Davies, Paul C W and Decuzzi, Paolo and Dickinson, Laura and Estevez-Salmeron, Luis and Estrella, Veronica and Ferrari, Mauro and Fischbach, Claudia and Foo, Jasmine and Fraley, Stephanie I and Frantz, Christian and Fuhrmann, Alexander and Gascard, Philippe and Gatenby, Robert A and Geng, Yue and Gerecht, Sharon and Gillies, Robert J and Godin, Biana and Grady, William M and Greenfield, Alex and Hemphill, Courtney and Hempstead, Barbara L and Hielscher, Abigail and Hillis, W Daniel and Holland, Eric C and Ibrahim-Hashim, Arig and Jacks, Tyler and Johnson, Roger H and Joo, Ahyoung and Katz, Jonathan E and Kelbauskas, Laimonas and Kesselman, Carl and King, Michael R and Konstantopoulos, Konstantinos and Kraning-Rush, Casey M and Kuhn, Peter and Kung, Kevin and Kwee, Brian and Lakins, Johnathon N and Lambert, Guillaume and Liao, David and Licht, Jonathan D and Liphardt, Jan T and Liu, Liyu and Lloyd, Mark C and Lyubimova, Anna and Mallick, Parag and Marko, John and McCarty, Owen J T and Meldrum, Deirdre R and Michor, Franziska and Mumenthaler, Shannon M and Nandakumar, Vivek and O{\textquoteright}Halloran, Thomas V and Oh, Steve and Pasqualini, Renata and Paszek, Matthew J and Philips, Kevin G and Poultney, Christopher S and Rana, Kuldeepsinh and Reinhart-King, Cynthia A and Ros, Robert and Semenza, Gregg L and Senechal, Patti and Shuler, Michael L and Srinivasan, Srimeenakshi and Staunton, Jack R and Stypula, Yolanda and Subramanian, Hariharan and Tlsty, Thea D and Tormoen, Garth W and Tseng, Yiider and van Oudenaarden, Alexander and Verbridge, Scott S and Wan, Jenny C and Weaver, Valerie M and Widom, Jonathan and Will, Christine and Wirtz, Denis and Wojtkowiak, Jonathan and Wu, Pei-Hsun} } @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 {281, title = {Exploring the link between human embryonic stem cell organization and fate using tension-calibrated extracellular matrix functionalized polyacrylamide gels.}, journal = {Methods Mol Biol}, volume = {916}, year = {2012}, month = {2012}, pages = {317-50}, abstract = {

Human embryonic stem cell (hESc) lines are likely the in vitro equivalent of the pluripotent epiblast. hESc express high levels of the extracellular matrix (ECM) laminin integrin receptor α6β1 and consequently can adhere robustly and be propagated in an undifferentiated state on tissue culture plastic coated with the laminin rich basement membrane preparation, Matrigel, even in the absence of supporting fibroblasts. Such cultures represent a critical step in the development of more defined feeder free cultures of hESc; a goal deemed necessary for regenerative medical applications and have been used as the starting point in some differentiation protocols. However, on standard non-deformable tissue culture plastic hESc either fail or inadequately develop the structural/morphological organization of the epiblast in vivo. By contrast, growth of hESc on appropriately defined mechanically deformable polyacrylamide substrates permits recapitulation of many of these in vivo features. These likely herald differences in the precise nature of the integration of signal transduction pathways from soluble morphogens and represent an unexplored variable in hESc (fate) state space. In this chapter we describe how to establish viable hESc colonies on these functionalized polyacrylamide gels. We suggest this strategy as a prospective in vitro model of the genetics, biochemistry, and cell biology of pre- and early-gastrulation stage human embryos and the permissive and instructive roles that cellular and substrate mechanics might play in early embryonic cell fate decisions. Such knowledge should inform regenerative medical applications aimed at enabling or improving the differentiation of specific cell types from embryonic or induced embryonic stem cells.

}, keywords = {Acrylamides, Acrylic Resins, Calibration, Cell Culture Techniques, Cell Differentiation, Cell Polarity, Collagen, Crystallization, Drug Combinations, Elastic Modulus, Embryonic Stem Cells, Extracellular Matrix, Glutaral, Humans, Laminin, Ligands, Proteoglycans, Stress, Mechanical, Trypsin}, issn = {1940-6029}, doi = {10.1007/978-1-61779-980-8_24}, author = {Lakins, Johnathon N and Chin, Andrew R and Weaver, Valerie M} } @article {291, title = {The extracellular matrix: a dynamic niche in cancer progression.}, journal = {J Cell Biol}, volume = {196}, year = {2012}, month = {2012 Feb 20}, pages = {395-406}, abstract = {

The local microenvironment, or niche, of a cancer cell plays important roles in cancer development. A major component of the niche is the extracellular matrix (ECM), a complex network of macromolecules with distinctive physical, biochemical, and biomechanical properties. Although tightly controlled during embryonic development and organ homeostasis, the ECM is commonly deregulated and becomes disorganized in diseases such as cancer. Abnormal ECM affects cancer progression by directly promoting cellular transformation and metastasis. Importantly, however, ECM anomalies also deregulate behavior of stromal cells, facilitate tumor-associated angiogenesis and inflammation, and thus lead to generation of a tumorigenic microenvironment. Understanding how ECM composition and topography are maintained and how their deregulation influences cancer progression may help develop new therapeutic interventions by targeting the tumor niche.

}, keywords = {Disease Progression, Extracellular Matrix, Humans, Neoplasms}, issn = {1540-8140}, doi = {10.1083/jcb.201102147}, author = {Lu, Pengfei and Weaver, Valerie M and Werb, Zena} } @article {231, title = {Scanning angle interference microscopy reveals cell dynamics at the nanoscale.}, journal = {Nat Methods}, volume = {9}, year = {2012}, month = {2012 Aug}, pages = {825-7}, abstract = {

Emerging questions in cell biology necessitate nanoscale imaging in live cells. Here we present scanning angle interference microscopy, which is capable of localizing fluorescent objects with nanoscale precision along the optical axis in motile cellular structures. We use this approach to resolve nanotopographical features of the cell membrane and cytoskeleton as well as the temporal evolution, three-dimensional architecture and nanoscale dynamics of focal adhesion complexes.

}, keywords = {Cell Membrane, Cells, Cultured, Cytoskeleton, Epithelial Cells, Fibronectins, Focal Adhesions, Humans, Microscopy, Interference, Nanotechnology}, issn = {1548-7105}, doi = {10.1038/nmeth.2077}, author = {Paszek, Matthew J and DuFort, Christopher C and Rubashkin, Matthew G and Davidson, Michael W and Thorn, Kurt S and Liphardt, Jan T and Weaver, Valerie M} } @article {311, title = {Actomyosin-mediated cellular tension drives increased tissue stiffness and β-catenin activation to induce epidermal hyperplasia and tumor growth.}, journal = {Cancer Cell}, volume = {19}, year = {2011}, month = {2011 Jun 14}, pages = {776-91}, abstract = {

Tumors and associated stroma manifest mechanical properties that promote cancer. Mechanosensation of tissue stiffness activates the Rho/ROCK pathway to increase actomyosin-mediated cellular tension to re-establish force equilibrium. To determine how actomyosin tension affects tissue homeostasis and tumor development, we expressed conditionally active ROCK2 in mouse skin. ROCK activation elevated tissue stiffness via increased collagen. β-catenin, a key element of mechanotranscription pathways, was stabilized by ROCK activation leading to nuclear accumulation, transcriptional activation, and consequent hyperproliferation and skin thickening. Inhibiting actomyosin contractility by blocking LIMK or myosin ATPase attenuated these responses, as did FAK inhibition. Tumor number, growth, and progression were increased by ROCK activation, while ROCK blockade was inhibitory, implicating actomyosin-mediated cellular tension and consequent collagen deposition as significant tumor promoters.

}, keywords = {Actomyosin, Animals, beta Catenin, Biomechanical Phenomena, Cell Proliferation, Cells, Cultured, Epidermis, Humans, Hyperplasia, Mice, Papilloma, rho-Associated Kinases, Signal Transduction, Skin Neoplasms}, issn = {1878-3686}, doi = {10.1016/j.ccr.2011.05.008}, author = {Samuel, Michael S and Lopez, Jose I and McGhee, Ewan J and Croft, Daniel R and Strachan, David and Timpson, Paul and Munro, June and Schr{\"o}der, Ewald and Zhou, Jing and Brunton, Valerie G and Barker, Nick and Clevers, Hans and Sansom, Owen J and Anderson, Kurt I and Weaver, Valerie M and Olson, Michael F} } @article {296, title = {Extracellular matrix degradation and remodeling in development and disease.}, journal = {Cold Spring Harb Perspect Biol}, volume = {3}, year = {2011}, month = {2011 Dec}, abstract = {

The extracellular matrix (ECM) serves diverse functions and is a major component of the cellular microenvironment. The ECM is a highly dynamic structure, constantly undergoing a remodeling process where ECM components are deposited, degraded, or otherwise modified. ECM dynamics are indispensible during restructuring of tissue architecture. ECM remodeling is an important mechanism whereby cell differentiation can be regulated, including processes such as the establishment and maintenance of stem cell niches, branching morphogenesis, angiogenesis, bone remodeling, and wound repair. In contrast, abnormal ECM dynamics lead to deregulated cell proliferation and invasion, failure of cell death, and loss of cell differentiation, resulting in congenital defects and pathological processes including tissue fibrosis and cancer. Understanding the mechanisms of ECM remodeling and its regulation, therefore, is essential for developing new therapeutic interventions for diseases and novel strategies for tissue engineering and regenerative medicine.

}, keywords = {Animals, Body Patterning, Cell Differentiation, Extracellular Matrix, Extracellular Matrix Proteins, Mice, Models, Biological, Neoplasms, Peptide Hydrolases, Signal Transduction, Stem Cells, Vertebrates}, issn = {1943-0264}, doi = {10.1101/cshperspect.a005058}, author = {Lu, Pengfei and Takai, Ken and Weaver, Valerie M and Werb, Zena} } @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 {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 {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 {371, title = {Filamin A-beta1 integrin complex tunes epithelial cell response to matrix tension.}, journal = {Mol Biol Cell}, volume = {20}, year = {2009}, month = {2009 Jul}, pages = {3224-38}, abstract = {

The physical properties of the extracellular matrix (ECM) regulate the behavior of several cell types; yet, mechanisms by which cells recognize and respond to changes in these properties are not clear. For example, breast epithelial cells undergo ductal morphogenesis only when cultured in a compliant collagen matrix, but not when the tension of the matrix is increased by loading collagen gels or by increasing collagen density. We report that the actin-binding protein filamin A (FLNa) is necessary for cells to contract collagen gels, and pull on collagen fibrils, which leads to collagen remodeling and morphogenesis in compliant, low-density gels. In stiffer, high-density gels, cells are not able to contract and remodel the matrix, and morphogenesis does not occur. However, increased FLNa-beta1 integrin interactions rescue gel contraction and remodeling in high-density gels, resulting in branching morphogenesis. These results suggest morphogenesis can be \"tuned\" by the balance between cell-generated contractility and opposing matrix stiffness. Our findings support a role for FLNa-beta1 integrin as a mechanosensitive complex that bidirectionally senses the tension of the matrix and, in turn, regulates cellular contractility and response to this matrix tension.

}, keywords = {Animals, Antigens, CD29, Biomechanical Phenomena, Cell Line, Tumor, Collagen, Contractile Proteins, Epithelial Cells, Extracellular Matrix, Filamins, Gels, Humans, Mice, Microfilament Proteins, Morphogenesis, Myosin Light Chains, Phosphorylation, Protein Binding}, issn = {1939-4586}, doi = {10.1091/mbc.E08-12-1186}, author = {Gehler, Scott and Baldassarre, Massimiliano and Lad, Yatish and Leight, Jennifer L and Wozniak, Michele A and Riching, Kristin M and Eliceiri, Kevin W and Weaver, Valerie M and Calderwood, David A and Keely, Patricia J} } @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 {396, title = {Biomechanical regulation of cell orientation and fate.}, journal = {Oncogene}, volume = {27}, year = {2008}, month = {2008 Nov 24}, pages = {6981-93}, abstract = {

Biomechanical regulation of tumor phenotypes have been noted for several decades, yet the function of mechanics in the co-evolution of the tumor epithelium and altered cancer extracellular matrix has not been appreciated until fairly recently. In this review, we examine the dynamic interaction between the developing epithelia and the extracellular matrix, and discuss how similar interactions are exploited by the genetically modified epithelium during tumor progression. We emphasize the process of mechanoreciprocity, which is a phenomenon observed during epithelial transformation, in which tension generated within the extracellular microenvironment induce and cooperate with opposing reactive forces within transformed epithelium to drive tumor progression and metastasis. We highlight the importance of matrix remodeling, and present a new, emerging paradigm that underscores the importance of tissue morphology as a key regulator of epithelial cell invasion and metastasis.

}, keywords = {Animals, Biochemical Processes, Bioreactors, Cell Culture Techniques, Cell Differentiation, Cell Movement, Cell Polarity, Cell Transformation, Neoplastic, Embryonic Development, Epithelial Cells, Humans, Mechanotransduction, Cellular, Models, Biological, Neoplasm Metastasis}, issn = {1476-5594}, doi = {10.1038/onc.2008.348}, author = {Lopez, J I and Mouw, J K and Weaver, V M} } @article {411, title = {Rac-dependent cyclin D1 gene expression regulated by cadherin- and integrin-mediated adhesion.}, journal = {J Cell Sci}, volume = {121}, year = {2008}, month = {2008 Jan 15}, pages = {226-33}, abstract = {

Integrin-mediated adhesion to substratum is required for cyclin D1 induction in mesenchymal cells, but we show here that the induction of cyclin D1 persists despite blockade of ECM-integrin signaling in MCF10A mammary epithelial cells. E-cadherin-mediated cell-cell adhesion also supports cyclin D1 induction in these cells, and the combined inhibition of both E-cadherin and integrin adhesion is required to prevent the expression of cyclin D1 mRNA and protein. Our previous studies described a pro-proliferative effect of E-cadherin in MCF10A cells, mediated by Rac, and we now show that Rac is required for cyclin D1 mRNA induction by both E-cadherin and integrin engagement. The levels of p21Cip1 and p27Kip1, Cdk inhibitors that are also targets of integrin signaling, are not affected by E-cadherin-mediated cell-cell adhesion. Finally, we show that the increased expression of cyclin D1 mRNA associated with E-cadherin-dependent cell-cell adhesion is causally linked to an increased entry into S phase. Our results identify Rac signaling to cyclin D1 as a crucial pro-proliferative effect of E-cadherin-mediated cell-cell adhesion.

}, keywords = {Cadherins, Cell Adhesion, Cell Communication, Cell Line, Tumor, Cyclin D1, Cyclin-Dependent Kinase Inhibitor p21, Cyclin-Dependent Kinase Inhibitor p27, Gene Expression Regulation, Gene Expression Regulation, Neoplastic, Humans, Integrins, Models, Biological, rac GTP-Binding Proteins, Signal Transduction}, issn = {0021-9533}, doi = {10.1242/jcs.017012}, author = {Fournier, Alaina K and Campbell, Latoya E and Castagnino, Paola and Liu, Wendy F and Chung, Betty M and Weaver, Valerie M and Chen, Christopher S and Assoian, Richard K} } @article {416, title = {alpha6beta4 integrin activates Rac-dependent p21-activated kinase 1 to drive NF-kappaB-dependent resistance to apoptosis in 3D mammary acini.}, journal = {J Cell Sci}, volume = {120}, year = {2007}, month = {2007 Oct 15}, pages = {3700-12}, abstract = {

Malignant transformation and multidrug resistance are linked to resistance to apoptosis, yet the molecular mechanisms that mediate tumor survival remain poorly understood. Because the stroma can influence tumor behavior by regulating the tissue phenotype, we explored the role of extracellular matrix signaling and tissue organization in epithelial survival. We report that elevated (alpha6)beta4 integrin-dependent Rac-Pak1 signaling supports resistance to apoptosis in mammary acini by permitting stress-dependent activation of the p65 subunit of NF-kappaB through Pak1. We found that inhibiting Pak1 through expression of N17Rac or PID compromises NF-kappaB activation and renders mammary acini sensitive to death, but that resistance to apoptosis could be restored to these structures by overexpressing wild-type NF-kappaB p65. We also observed that acini expressing elevated levels of Pak1 can activate p65 and survive death treatments, even in the absence of activated Rac, yet will die if activation of NF-kappaB is simultaneously inhibited through expression of IkappaBalphaM. Thus, mammary tissues can resist apoptotic stimuli by activating NF-kappaB through alpha6beta4 integrin-dependent Rac-Pak1 signaling. Our data emphasize the importance of the extracellular matrix stroma in tissue survival and suggest that alpha6beta4 integrin-dependent Rac stimulation of Pak1 could be an important mechanism mediating apoptosis-resistance in some breast tumors.

}, keywords = {Apoptosis, Enzyme Activation, Humans, Integrin alpha6beta4, Mammary Glands, Human, p21-Activated Kinases, Proto-Oncogene Proteins c-akt, rac GTP-Binding Proteins, Transcription Factor RelA}, issn = {0021-9533}, doi = {10.1242/jcs.03484}, author = {Friedland, Julie C and Lakins, Johnathon N and Kazanietz, Marcelo G and Chernoff, Jonathan and Boettiger, David and Weaver, Valerie M} } @article {421, title = {Tensional homeostasis and the malignant phenotype.}, journal = {Cancer Cell}, volume = {8}, year = {2005}, month = {2005 Sep}, pages = {241-54}, abstract = {

Tumors are stiffer than normal tissue, and tumors have altered integrins. Because integrins are mechanotransducers that regulate cell fate, we asked whether tissue stiffness could promote malignant behavior by modulating integrins. We found that tumors are rigid because they have a stiff stroma and elevated Rho-dependent cytoskeletal tension that drives focal adhesions, disrupts adherens junctions, perturbs tissue polarity, enhances growth, and hinders lumen formation. Matrix stiffness perturbs epithelial morphogenesis by clustering integrins to enhance ERK activation and increase ROCK-generated contractility and focal adhesions. Contractile, EGF-transformed epithelia with elevated ERK and Rho activity could be phenotypically reverted to tissues lacking focal adhesions if Rho-generated contractility or ERK activity was decreased. Thus, ERK and Rho constitute part of an integrated mechanoregulatory circuit linking matrix stiffness to cytoskeletal tension through integrins to regulate tissue phenotype.

}, keywords = {3T3 Cells, Animals, Cell Line, Tumor, Cell Shape, Cytoskeleton, Homeostasis, Mice, Neoplasms, Phenotype, Stress, Mechanical, Stromal Cells}, issn = {1535-6108}, doi = {10.1016/j.ccr.2005.08.010}, author = {Paszek, Matthew J and Zahir, Nastaran and Johnson, Kandice R and Lakins, Johnathon N and Rozenberg, Gabriela I and Gefen, Amit and Reinhart-King, Cynthia A and Margulies, Susan S and Dembo, Micah and Boettiger, David and Hammer, Daniel A and Weaver, Valerie M} } @article {516, title = {Autocrine laminin-5 ligates alpha6beta4 integrin and activates RAC and NFkappaB to mediate anchorage-independent survival of mammary tumors.}, journal = {J Cell Biol}, volume = {163}, year = {2003}, month = {2003 Dec 22}, pages = {1397-407}, abstract = {

Invasive carcinomas survive and evade apoptosis despite the absence of an exogenous basement membrane. How epithelial tumors acquire anchorage independence for survival remains poorly defined. Epithelial tumors often secrete abundant amounts of the extracellular matrix protein laminin 5 (LM-5) and frequently express alpha6beta4 integrin. Here, we show that autocrine LM-5 mediates anchorage-independent survival in breast tumors through ligation of a wild-type, but not a cytoplasmic tail-truncated alpha6beta4 integrin. alpha6beta4 integrin does not mediate tumor survival through activation of ERK or AKT. Instead, the cytoplasmic tail of beta4 integrin is necessary for basal and epidermal growth factor-induced RAC activity, and RAC mediates tumor survival. Indeed, a constitutively active RAC sustains the viability of mammary tumors lacking functional beta1 and beta4 integrin through activation of NFkappaB, and overexpression of NFkappaB p65 mediates anchorage-independent survival of nonmalignant mammary epithelial cells. Therefore, epithelial tumors could survive in the absence of exogenous basement membrane through autocrine LM-5-alpha6beta4 integrin-RAC-NFkappaB signaling.

}, keywords = {Autocrine Communication, Basement Membrane, Breast Neoplasms, Carcinoma, Cell Adhesion, Cell Adhesion Molecules, Cell Line, Tumor, Cell Survival, Epidermal Growth Factor, Humans, Integrin alpha6beta4, MAP Kinase Signaling System, Neoplasm Invasiveness, NF-kappa B, Protein Structure, Tertiary, rac GTP-Binding Proteins}, issn = {0021-9525}, doi = {10.1083/jcb.200302023}, author = {Zahir, Nastaran and Lakins, Johnathon N and Russell, Alan and Ming, WenYu and Chatterjee, Chandrima and Rozenberg, Gabriela I and Marinkovich, M Peter 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 {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 {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} } @article {571, title = {Degradation of nuclear matrix and DNA cleavage in apoptotic thymocytes.}, journal = {J Cell Sci}, volume = {109 ( Pt 1)}, year = {1996}, month = {1996 Jan}, pages = {45-56}, abstract = {

In dexamethasone-treated thymocyte cultures an increase in nuclear proteolytic activity paralleled chromatin fragmentation and the appearance of small apoptotic cells. The elevation of nuclear proteolytic activity was accompanied by site-specific degradation of nuclear mitotic apparatus protein and lamin B, two essential components of the nuclear matrix. Nuclear mitotic apparatus protein phosphorylation and cleavage into 200 and 48 kDa fragments occurred within 30 minutes of dexamethasone treatment. Cleavage of lamin B, which generated a fragment of 46 kDa consistent with the central rod domain of the protein, was also detected after 30 minutes of exposure to the steroid hormone. The level of lamin B phosphorylation did not change as a result of the dexamethasone treatment and the lamina did not solubilize until the later stages of apoptosis. Initial DNA breaks, detected by the terminal transferase-mediated dUTP-biotin nick end labeling assay, occurred throughout the nuclei and solubilization of lamina was not required for this process to commence. The data presented in this paper support a model of apoptotic nuclear destruction brought about by the site-specific proteolysis of key structural proteins. Both the nuclear mitotic apparatus protein and lamin B were specifically targeted by protease(s) at early stages of the cell death pathway, which possibly initiate the cascade of degradative events in apoptosis.

}, keywords = {alpha 1-Antichymotrypsin, Animals, Apoptosis, Cell Nucleus, Cells, Cultured, Dexamethasone, DNA, DNA Damage, Endopeptidases, Lamin Type B, Lamins, Male, Microscopy, Electron, Nuclear Matrix, Nuclear Proteins, Rats, Rats, Sprague-Dawley, Spindle Apparatus, Thymus Gland, Time Factors}, issn = {0021-9533}, author = {Weaver, V M and Carson, C E and Walker, P R and Chaly, N and Lach, B and Raymond, Y and Brown, D L and Sikorska, M} }