Publications by authors named "Valerie M Weaver"

125 Publications

Mechanobiology: forcing the second act.

Authors:
Valerie M Weaver

Mol Biol Cell 2021 08;32(18):1611-1613

Center for Bioengineering and Tissue Regeneration, Department of Surgery, Departments of Radiation Oncology and Bioengineering and Therapeutic Sciences, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, and UCSF Helen Diller Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94143-0456.

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http://dx.doi.org/10.1091/mbc.E21-07-0343DOI Listing
August 2021

Autophagy in stromal fibroblasts promotes tumor desmoplasia and mammary tumorigenesis.

Genes Dev 2021 Jul 24;35(13-14):963-975. Epub 2021 Jun 24.

Department of Pathology, Helen Diller Family Comprehensive Cancer Center, University of California at San Francisco, San Francisco, California 94143, USA.

Autophagy inhibitors are currently being evaluated in clinical trials for the treatment of diverse cancers, largely due to their ability to impede tumor cell survival and metabolic adaptation. More recently, there is growing interest in whether and how modulating autophagy in the host stroma influences tumorigenesis. Fibroblasts play prominent roles in cancer initiation and progression, including depositing type 1 collagen and other extracellular matrix (ECM) components, thereby stiffening the surrounding tissue to enhance tumor cell proliferation and survival, as well as secreting cytokines that modulate angiogenesis and the immune microenvironment. This constellation of phenotypes, pathologically termed desmoplasia, heralds poor prognosis and reduces patient survival. Using mouse mammary cancer models and syngeneic transplantation assays, we demonstrate that genetic ablation of stromal fibroblast autophagy significantly impedes fundamental elements of the stromal desmoplastic response, including collagen and proinflammatory cytokine secretion, extracellular matrix stiffening, and neoangiogenesis. As a result, autophagy in stromal fibroblasts is required for mammary tumor growth in vivo, even when the cancer cells themselves remain autophagy-competent . We propose the efficacy of autophagy inhibition is shaped by this ability of host stromal fibroblast autophagy to support tumor desmoplasia.
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http://dx.doi.org/10.1101/gad.345629.120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8247603PMC
July 2021

Tissue mechanics in stem cell fate, development, and cancer.

Dev Cell 2021 Jul 8;56(13):1833-1847. Epub 2021 Jun 8.

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Bioengineering and Therapeutic Sciences and Department of Radiation Oncology, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; The Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94143, USA. Electronic address:

Cells in tissues experience a plethora of forces that regulate their fate and modulate development and homeostasis. Cells sense mechanical cues through localized mechanoreceptors or by influencing cytoskeletal or plasma membrane organization. Cells translate force and modulate their behavior through a process termed mechanotransduction. Cells tune their tension upon exposure to chronic force by engaging cellular machinery that modulates actin tension, which in turn stimulates matrix remodeling and stiffening and alters cell-cell adhesions until cells achieve a state of tensional homeostasis. Loss of tensional homeostasis can be induced through oncogene activity and/or tissue fibrosis, accompanies tumor progression, and is associated with increased cancer risk. The mechanical stresses that develop in tumors can also foster the mesenchymal-like transdifferentiation of cells to induce a stem-like phenotype that contributes to their aggression, metastatic dissemination, and treatment resistance. Thus, strategies that ameliorate tumor mechanics may comprise an effective strategy to prevent aggressive tumor behavior.
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http://dx.doi.org/10.1016/j.devcel.2021.05.011DOI Listing
July 2021

Adhesion-mediated mechanosignaling forces mitohormesis.

Cell Metab 2021 Jul 20;33(7):1322-1341.e13. Epub 2021 May 20.

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Bioengineering and Therapeutic Sciences and Department of Radiation Oncology, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, and The Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94143, USA. Electronic address:

Mitochondria control eukaryotic cell fate by producing the energy needed to support life and the signals required to execute programed cell death. The biochemical milieu is known to affect mitochondrial function and contribute to the dysfunctional mitochondrial phenotypes implicated in cancer and the morbidities of aging. However, the physical characteristics of the extracellular matrix are also altered in cancerous and aging tissues. Here, we demonstrate that cells sense the physical properties of the extracellular matrix and activate a mitochondrial stress response that adaptively tunes mitochondrial function via solute carrier family 9 member A1-dependent ion exchange and heat shock factor 1-dependent transcription. Overall, our data indicate that adhesion-mediated mechanosignaling may play an unappreciated role in the altered mitochondrial functions observed in aging and cancer.
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http://dx.doi.org/10.1016/j.cmet.2021.04.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8266765PMC
July 2021

Single-cell transcriptome analysis defines heterogeneity of the murine pancreatic ductal tree.

Elife 2021 May 19;10. Epub 2021 May 19.

Diabetes Center, University of California, San Francisco, San Francisco, United States.

To study disease development, an inventory of an organ's cell types and understanding of physiologic function is paramount. Here, we performed single-cell RNA-sequencing to examine heterogeneity of murine pancreatic duct cells, pancreatobiliary cells, and intrapancreatic bile duct cells. We describe an epithelial-mesenchymal transitory axis in our three pancreatic duct subpopulations and identify osteopontin as a regulator of this fate decision as well as human duct cell dedifferentiation. Our results further identify functional heterogeneity within pancreatic duct subpopulations by elucidating a role for geminin in accumulation of DNA damage in the setting of chronic pancreatitis. Our findings implicate diverse functional roles for subpopulations of pancreatic duct cells in maintenance of duct cell identity and disease progression and establish a comprehensive road map of murine pancreatic duct cell, pancreatobiliary cell, and intrapancreatic bile duct cell homeostasis.
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http://dx.doi.org/10.7554/eLife.67776DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8184217PMC
May 2021

Improving DCIS diagnosis and predictive outcome by applying artificial intelligence.

Biochim Biophys Acta Rev Cancer 2021 08 29;1876(1):188555. Epub 2021 Apr 29.

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, California, USA; Department of Bioengineering and Therapeutic Sciences, and UCSF Helen Diller Comprehensive Cancer Center, University of California, San Francisco, San Francisco, California, USA; Department of Radiation Oncology, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, California, USA. Electronic address:

Breast ductal carcinoma in situ (DCIS) is a preinvasive lesion that is considered to be a precursor to invasive breast cancer. Nevertheless, not all DCIS will progress to invasion. Current histopathological classification systems are unable to predict which cases will or will not progress, and therefore many women with DCIS may be overtreated. Artificial intelligence (AI) image-based analysis methods have potential to identify and analyze novel features that may facilitate tumor identification, prediction of disease outcome and response to treatment. Indeed, these methods prove promising for accurately identifying DCIS lesions, and show potential clinical utility in the therapeutic stratification of DCIS patients. Here, we review how AI techniques in histopathology may aid diagnosis and clinical decisions in regards to DCIS, and how such techniques could be incorporated into clinical practice.
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http://dx.doi.org/10.1016/j.bbcan.2021.188555DOI Listing
August 2021

Matrix compliance permits NF-κB activation to drive therapy resistance in breast cancer.

J Exp Med 2021 05;218(5)

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, CA.

Triple-negative breast cancers (TNBCs) are associated with poor survival mediated by treatment resistance. TNBCs are fibrotic, yet little is known regarding how the extracellular matrix (ECM) evolves following therapy and whether it impacts treatment response. Analysis revealed that while primary untreated TNBCs are surrounded by a rigid stromal microenvironment, chemotherapy-resistant residual tumors inhabit a softer niche. TNBC organoid cultures and xenograft studies showed that organoids interacting with soft ECM exhibit striking resistance to chemotherapy, ionizing radiation, and death receptor ligand TRAIL. A stiff ECM enhanced proapoptotic JNK activity to sensitize cells to treatment, whereas a soft ECM promoted treatment resistance by elevating NF-κB activity and compromising JNK activity. Treatment-resistant residual TNBCs residing within soft stroma had elevated activated NF-κB levels, and disengaging NF-κB activity sensitized tumors in a soft matrix to therapy. Thus, the biophysical properties of the ECM modify treatment response, and agents that modulate stiffness-dependent NF-κB or JNK activity could enhance therapeutic efficacy in patients with TNBC.
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http://dx.doi.org/10.1084/jem.20191360DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8025243PMC
May 2021

EPH/EPHRIN regulates cellular organization by actomyosin contractility effects on cell contacts.

J Cell Biol 2021 Jun;220(6)

Program in Craniofacial Biology, University of California, San Francisco, San Francisco, CA.

EPH/EPHRIN signaling is essential to many aspects of tissue self-organization and morphogenesis, but little is known about how EPH/EPHRIN signaling regulates cell mechanics during these processes. Here, we use a series of approaches to examine how EPH/EPHRIN signaling drives cellular self-organization. Contact angle measurements reveal that EPH/EPHRIN signaling decreases the stability of heterotypic cell:cell contacts through increased cortical actomyosin contractility. We find that EPH/EPHRIN-driven cell segregation depends on actomyosin contractility but occurs independently of directed cell migration and without changes in cell adhesion. Atomic force microscopy and live cell imaging of myosin localization support that EPH/EPHRIN signaling results in increased cortical tension. Interestingly, actomyosin contractility also nonautonomously drives increased EPHB2:EPHB2 homotypic contacts. Finally, we demonstrate that changes in tissue organization are driven by minimization of heterotypic contacts through actomyosin contractility in cell aggregates and by mouse genetics experiments. These data elucidate the biomechanical mechanisms driving EPH/EPHRIN-based cell segregation wherein differences in interfacial tension, regulated by actomyosin contractility, govern cellular self-organization.
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http://dx.doi.org/10.1083/jcb.202005216DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8025214PMC
June 2021

Leveraging microenvironmental synthetic lethalities to treat cancer.

J Clin Invest 2021 03;131(6)

Department of Surgery.

Treatment resistance leads to cancer patient mortality. Therapeutic approaches that employ synthetic lethality to target mutational vulnerabilities in key tumor cell signaling pathways have proven effective in overcoming therapeutic resistance in some cancers. Yet, tumors are organs composed of malignant cells residing within a cellular and noncellular stroma. Tumor evolution and resistance to anticancer treatment are mediated through a dynamic and reciprocal dialogue with the tumor microenvironment (TME). Accordingly, expanding tumor cell synthetic lethality to encompass contextual synthetic lethality has the potential to eradicate tumors by targeting critical TME circuits that promote tumor progression and therapeutic resistance. In this Review, we summarize current knowledge about the TME and discuss its role in treatment. We outline the concept of tumor cell-specific synthetic lethality and describe therapeutic approaches to expand this paradigm to leverage TME synthetic lethality to improve cancer therapy.
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http://dx.doi.org/10.1172/JCI143765DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7954586PMC
March 2021

Membrane Tension Locks In Pluripotency.

Cell Stem Cell 2021 02;28(2):175-176

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, CA 94143, USA; Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; UCSF Comprehensive Cancer Center, Helen Diller Family Cancer Research Center, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Anatomy, Department of Bioengineering and Therapeutic Sciences, Department of Radiation Oncology, University of California, San Francisco, San Francisco, CA 94143, USA. Electronic address:

In this issue of Cell Stem Cell, De Belly et al. (2021) and Bergert et al. (2021) reveal that membrane tension regulates the pluripotent state via endocytosis-mediated ERK signaling. These findings advance our understanding of naive pluripotency and highlight how cell mechanics are intertwined with molecular signaling to drive cell fate decisions.
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http://dx.doi.org/10.1016/j.stem.2021.01.008DOI Listing
February 2021

Derivation of a nuclear heterogeneity image index to grade DCIS.

Comput Struct Biotechnol J 2020 3;18:4063-4070. Epub 2020 Dec 3.

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California San Francisco, San Francisco, CA, USA.

Abnormalities in cell nuclear morphology are a hallmark of cancer. Histological assessment of cell nuclear morphology is frequently used by pathologists to grade ductal carcinoma in situ (DCIS). Objective methods that allow standardization and reproducibility of cell nuclear morphology assessment have potential to improve the criteria needed to predict DCIS progression and recurrence. Aggressive cancers are highly heterogeneous. We asked whether cell nuclear morphology heterogeneity could be incorporated into a metric to classify DCIS. We developed a nuclear heterogeneity image index to objectively, and quantitatively grade DCIS. A whole-tissue cell nuclear morphological analysis, that classified tumors by the worst ten percent in a duct-by-duct manner, identified nuclear size ranges associated with each DCIS grade. Digital image analysis further revealed increasing heterogeneity within ducts or between ducts in tissues of worsening DCIS grade. The findings illustrate how digital image analysis comprises a supplemental tool for pathologists to objectively classify DCIS and in the future, may provide a method to predict patient outcome through analysis of nuclear heterogeneity.
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http://dx.doi.org/10.1016/j.csbj.2020.11.040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7744935PMC
December 2020

Proteoglycans as Mediators of Cancer Tissue Mechanics.

Front Cell Dev Biol 2020 30;8:569377. Epub 2020 Nov 30.

Center for Bioengineering & Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, CA, United States.

Proteoglycans are a diverse group of molecules which are characterized by a central protein backbone that is decorated with a variety of linear sulfated glycosaminoglycan side chains. Proteoglycans contribute significantly to the biochemical and mechanical properties of the interstitial extracellular matrix where they modulate cellular behavior by engaging transmembrane receptors. Proteoglycans also comprise a major component of the cellular glycocalyx to influence transmembrane receptor structure/function and mechanosignaling. Through their ability to initiate biochemical and mechanosignaling in cells, proteoglycans elicit profound effects on proliferation, adhesion and migration. Pathologies including cancer and cardiovascular disease are characterized by perturbed expression of proteoglycans where they compromise cell and tissue behavior by stiffening the extracellular matrix and increasing the bulkiness of the glycocalyx. Increasing evidence indicates that a bulky glycocalyx and proteoglycan-enriched extracellular matrix promote malignant transformation, increase cancer aggression and alter anti-tumor therapy response. In this review, we focus on the contribution of proteoglycans to mechanobiology in the context of normal and transformed tissues. We discuss the significance of proteoglycans for therapy response, and the current experimental strategies that target proteoglycans to sensitize cancer cells to treatment.
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http://dx.doi.org/10.3389/fcell.2020.569377DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7734320PMC
November 2020

Tumour-associated macrophages drive stromal cell-dependent collagen crosslinking and stiffening to promote breast cancer aggression.

Nat Mater 2021 04 30;20(4):548-559. Epub 2020 Nov 30.

UCSF Helen Diller Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA, USA.

Stromal stiffening accompanies malignancy, compromises treatment and promotes tumour aggression. Clarifying the molecular nature and the factors that regulate stromal stiffening in tumours should identify biomarkers to stratify patients for therapy and interventions to improve outcome. We profiled lysyl hydroxylase-mediated and lysyl oxidase-mediated collagen crosslinks and quantified the greatest abundance of total and complex collagen crosslinks in aggressive human breast cancer subtypes with the stiffest stroma. These tissues harbour the highest number of tumour-associated macrophages, whose therapeutic ablation in experimental models reduced metastasis, and decreased collagen crosslinks and stromal stiffening. Epithelial-targeted expression of the crosslinking enzyme, lysyl oxidase, had no impact on collagen crosslinking in PyMT mammary tumours, whereas stromal cell targeting did. Stromal cells in microdissected human tumours expressed the highest level of collagen crosslinking enzymes. Immunohistochemical analysis of biopsies from a cohort of patients with breast cancer revealed that stromal expression of lysyl hydroxylase 2, an enzyme that induces hydroxylysine aldehyde-derived collagen crosslinks and stromal stiffening, correlated significantly with disease specific mortality. The findings link tissue inflammation, stromal cell-mediated collagen crosslinking and stiffening to tumour aggression and identify lysyl hydroxylase 2 as a stromal biomarker.
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http://dx.doi.org/10.1038/s41563-020-00849-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8005404PMC
April 2021

Mechanical Tension Promotes Formation of Gastrulation-like Nodes and Patterns Mesoderm Specification in Human Embryonic Stem Cells.

Dev Cell 2020 12 17;55(6):679-694.e11. Epub 2020 Nov 17.

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, CA 94143, USA; Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA 94143, USA; UCSF Comprehensive Cancer Center, Helen Diller Family Cancer Research Center, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Anatomy, Department of Bioengineering and Therapeutic Sciences, Department of Radiation Oncology, University of California, San Francisco, San Francisco, CA 94143, USA. Electronic address:

Embryogenesis is directed by morphogens that induce differentiation within a defined tissue geometry. Tissue organization is mediated by cell-cell and cell-extracellular matrix (ECM) adhesions and is modulated by cell tension and tissue-level forces. Whether cell tension regulates development by modifying morphogen signaling is less clear. Human embryonic stem cells (hESCs) exhibit an intrinsic capacity for self-organization, which motivates their use as a tractable model of early human embryogenesis. We engineered patterned substrates that recapitulate the biophysical properties of the early embryo and mediate the self-organization of "gastrulation-like" nodes in cultured hESCs. Tissue geometries that generated local nodes of high cell-adhesion tension directed the spatial patterning of the BMP4-dependent "gastrulation-like" phenotype by enhancing phosphorylation and junctional release of β-catenin to promote Wnt signaling and mesoderm specification. Furthermore, direct force application via mechanical stretching promoted BMP-dependent mesoderm specification, confirming that tissue-level forces can directly regulate cell fate specification in early human development.
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http://dx.doi.org/10.1016/j.devcel.2020.10.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7755684PMC
December 2020

Zena Werb (1945-2020): Mourning the loss of a tissue microenvironment icon.

Proc Natl Acad Sci U S A 2020 11 29;117(45):27759-27760. Epub 2020 Oct 29.

Biological Systems & Engineering Division, E. O. Lawrence Berkeley National Laboratory, Berkeley, CA 94720

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http://dx.doi.org/10.1073/pnas.2020162117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7668183PMC
November 2020

In Memoriam - Zena Werb 1945-2020.

J Mammary Gland Biol Neoplasia 2020 09 30;25(3):179-180. Epub 2020 Sep 30.

University of California, San Francisco, CA, USA.

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http://dx.doi.org/10.1007/s10911-020-09459-yDOI Listing
September 2020

Targeting acid ceramidase inhibits YAP/TAZ signaling to reduce fibrosis in mice.

Sci Transl Med 2020 08;12(557)

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, CA 94143, USA.

Hepatic stellate cells (HSCs) drive hepatic fibrosis. Therapies that inactivate HSCs have clinical potential as antifibrotic agents. We previously identified acid ceramidase (aCDase) as an antifibrotic target. We showed that tricyclic antidepressants (TCAs) reduce hepatic fibrosis by inhibiting aCDase and increasing the bioactive sphingolipid ceramide. We now demonstrate that targeting aCDase inhibits YAP/TAZ activity by potentiating its phosphorylation-mediated proteasomal degradation via the ubiquitin ligase adaptor protein β-TrCP. In mouse models of fibrosis, pharmacologic inhibition of aCDase or genetic knockout of aCDase in HSCs reduces fibrosis, stromal stiffness, and YAP/TAZ activity. In patients with advanced fibrosis, aCDase expression in HSCs is increased. Consistently, a signature of the genes most down-regulated by ceramide identifies patients with advanced fibrosis who could benefit from aCDase targeting. The findings implicate ceramide as a critical regulator of YAP/TAZ signaling and HSC activation and highlight aCDase as a therapeutic target for the treatment of fibrosis.
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http://dx.doi.org/10.1126/scitranslmed.aay8798DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7976849PMC
August 2020

Pancreatic ductal adenocarcinoma progression is restrained by stromal matrix.

J Clin Invest 2020 09;130(9):4704-4709

Division of Hematology and Oncology, Department of Medicine and Helen Diller Family Comprehensive Cancer Center, UCSF, San Francisco, California, USA.

Desmoplasia describes the deposition of extensive extracellular matrix and defines primary pancreatic ductal adenocarcinoma (PDA). The acellular component of this stroma has been implicated in PDA pathogenesis and is being targeted therapeutically in clinical trials. By analyzing the stromal content of PDA samples from numerous annotated PDA data sets and correlating stromal content with both anatomic site and clinical outcome, we found PDA metastases in the liver, the primary cause of mortality to have less stroma, have higher tumor cellularity than primary tumors. Experimentally manipulating stromal matrix with an anti-lysyl oxidase like-2 (anti-LOXL2) antibody in syngeneic orthotopic PDA mouse models significantly decreased matrix content, led to lower tissue stiffness, lower contrast retention on computed tomography, and accelerated tumor growth, resulting in diminished overall survival. These studies suggest an important protective role of stroma in PDA and urge caution in clinically deploying stromal depletion strategies.
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http://dx.doi.org/10.1172/JCI136760DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7456216PMC
September 2020

Stiff stroma increases breast cancer risk by inducing the oncogene ZNF217.

J Clin Invest 2020 11;130(11):5721-5737

Department of Surgery.

Women with dense breasts have an increased lifetime risk of malignancy that has been attributed to a higher epithelial density. Quantitative proteomics, collagen analysis, and mechanical measurements in normal tissue revealed that stroma in the high-density breast contains more oriented, fibrillar collagen that is stiffer and correlates with higher epithelial cell density. microRNA (miR) profiling of breast tissue identified miR-203 as a matrix stiffness-repressed transcript that is downregulated by collagen density and reduced in the breast epithelium of women with high mammographic density. Culture studies demonstrated that ZNF217 mediates a matrix stiffness- and collagen density-induced increase in Akt activity and mammary epithelial cell proliferation. Manipulation of the epithelium in a mouse model of mammographic density supported a causal relationship between stromal stiffness, reduced miR-203, higher levels of the murine homolog Zfp217, and increased Akt activity and mammary epithelial proliferation. ZNF217 was also increased in the normal breast epithelium of women with high mammographic density, correlated positively with epithelial proliferation and density, and inversely with miR-203. The findings identify ZNF217 as a potential target toward which preexisting therapies, such as the Akt inhibitor triciribine, could be used as a chemopreventive agent to reduce cancer risk in women with high mammographic density.
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http://dx.doi.org/10.1172/JCI129249DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7598051PMC
November 2020

Fibrosis and cancer: A strained relationship.

Biochim Biophys Acta Rev Cancer 2020 04 5;1873(2):188356. Epub 2020 Mar 5.

Department of Surgery and Center for Bioengineering and Tissue Regeneration, University of California, San Francisco (UCSF), USA; Departments of Radiation Oncology, Bioengineering and Therapeutic Sciences, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research at UCSF, UCSF Helen Diller Comprehensive Cancer Center, 513 Parnassus Avenue, HSE565, San Francisco, CA 94143-0456, USA. Electronic address:

Tumors are characterized by extracellular matrix (ECM) deposition, remodeling, and cross-linking that drive fibrosis to stiffen the stroma and promote malignancy. The stiffened stroma enhances tumor cell growth, survival and migration and drives a mesenchymal transition. A stiff ECM also induces angiogenesis, hypoxia and compromises anti-tumor immunity. Not surprisingly, tumor aggression and poor patient prognosis correlate with degree of tissue fibrosis and level of stromal stiffness. In this review, we discuss the reciprocal interplay between tumor cells, cancer associated fibroblasts (CAF), immune cells and ECM stiffness in malignant transformation and cancer aggression. We discuss CAF heterogeneity and describe its impact on tumor development and aggression focusing on the role of CAFs in engineering the fibrotic tumor stroma and tuning tumor cell tension and modulating the immune response. To illustrate the role of mechanoreciprocity in tumor evolution we summarize data from breast cancer and pancreatic ductal carcinoma (PDAC) studies, and finish by discussing emerging anti-fibrotic strategies aimed at treating cancer.
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http://dx.doi.org/10.1016/j.bbcan.2020.188356DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7733542PMC
April 2020

Don't sugarcoat it: How glycocalyx composition influences cancer progression.

J Cell Biol 2020 01;219(1)

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, CA.

Mechanical interactions between tumors and the extracellular matrix (ECM) of the surrounding tissues have profound effects on a wide variety of cellular functions. An underappreciated mediator of tumor-ECM interactions is the glycocalyx, the sugar-decorated proteins and lipids that act as a buffer between the tumor and the ECM, which in turn mediates all cell-tissue mechanics. Importantly, tumors have an increase in the density of the glycocalyx, which in turn increases the tension of the cell membrane, alters tissue mechanics, and drives a more cancerous phenotype. In this review, we describe the basic components of the glycocalyx and the glycan moieties implicated in cancer. Next, we examine the important role the glycocalyx plays in driving tension-mediated cancer cell signaling through a self-enforcing feedback loop that expands the glycocalyx and furthers cancer progression. Finally, we discuss current tools used to edit the composition of the glycocalyx and the future challenges in leveraging these tools into a novel tractable approach to treat cancer.
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http://dx.doi.org/10.1083/jcb.201910070DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7039198PMC
January 2020

Patterning the Geometry of Human Embryonic Stem Cell Colonies on Compliant Substrates to Control Tissue-Level Mechanics.

J Vis Exp 2019 09 28(151). Epub 2019 Sep 28.

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California San Francisco; Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California San Francisco; UCSF Comprehensive Cancer Center, Helen Diller Family Cancer Research Center, University of California San Francisco; Department of Anatomy, Department of Bioengineering and Therapeutic Sciences, and Department of Radiation Oncology, University of California San Francisco;

Human embryonic stem cells demonstrate a unique ability to respond to morphogens in vitro by self-organizing patterns of cell fate specification that correspond to primary germ layer formation during embryogenesis. Thus, these cells represent a powerful tool with which to examine the mechanisms that drive early human development. We have developed a method to culture human embryonic stem cells in confined colonies on compliant substrates that provides control over both the geometry of the colonies and their mechanical environment in order to recapitulate the physical parameters that underlie embryogenesis. The key feature of this method is the ability to generate polyacrylamide hydrogels with defined patterns of extracellular matrix ligand at the surface to promote cell attachment. This is achieved by fabricating stencils with the desired geometric patterns, using these stencils to create patterns of extracellular matrix ligand on glass coverslips, and transferring these patterns to polyacrylamide hydrogels during polymerization. This method is also compatible with traction force microscopy, allowing the user to measure and map the distribution of cell-generated forces within the confined colonies. In combination with standard biochemical assays, these measurements can be used to examine the role mechanical cues play in fate specification and morphogenesis during early human development.
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http://dx.doi.org/10.3791/60334DOI Listing
September 2019

Controlled modelling of human epiblast and amnion development using stem cells.

Nature 2019 09 11;573(7774):421-425. Epub 2019 Sep 11.

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA.

Early human embryonic development involves extensive lineage diversification, cell-fate specification and tissue patterning. Despite its basic and clinical importance, early human embryonic development remains relatively unexplained owing to interspecies divergence and limited accessibility to human embryo samples. Here we report that human pluripotent stem cells (hPSCs) in a microfluidic device recapitulate, in a highly controllable and scalable fashion, landmarks of the development of the epiblast and amniotic ectoderm parts of the conceptus, including lumenogenesis of the epiblast and the resultant pro-amniotic cavity, formation of a bipolar embryonic sac, and specification of primordial germ cells and primitive streak cells. We further show that amniotic ectoderm-like cells function as a signalling centre to trigger the onset of gastrulation-like events in hPSCs. Given its controllability and scalability, the microfluidic model provides a powerful experimental system to advance knowledge of human embryology and reproduction. This model could assist in the rational design of differentiation protocols of hPSCs for disease modelling and cell therapy, and in high-throughput drug and toxicity screens to prevent pregnancy failure and birth defects.
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http://dx.doi.org/10.1038/s41586-019-1535-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8106232PMC
September 2019

Wnt4 from the Niche Controls the Mechano-Properties and Quiescent State of Muscle Stem Cells.

Cell Stem Cell 2019 11 5;25(5):654-665.e4. Epub 2019 Sep 5.

The Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research, Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA 94143, USA. Electronic address:

Satellite cells (SCs) reside in a dormant state during tissue homeostasis. The specific paracrine agents and niche cells that maintain SC quiescence remain unknown. We find that Wnt4 produced by the muscle fiber maintains SC quiescence through RhoA. Using cell-specific inducible genetics, we find that a Wnt4-Rho signaling axis constrains SC numbers and activation during tissue homeostasis in adult mice. Wnt4 activates Rho in quiescent SCs to maintain mechanical strain, restrict movement in the niche, and repress YAP. The induction of YAP upon disruption of RhoA is essential for SC activation under homeostasis. In the context of injury, the loss of Wnt4 from the niche accelerates SC activation and muscle repair, whereas overexpression of Wnt4 transitions SCs into a deeper state of quiescence and delays muscle repair. In conclusion, the SC pool undergoes dynamic transitions during early activation with changes in mechano-properties and cytoskeleton signaling preceding cell-cycle entry.
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http://dx.doi.org/10.1016/j.stem.2019.08.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6842437PMC
November 2019

Tissue mechanics, an important regulator of development and disease.

Philos Trans R Soc Lond B Biol Sci 2019 08 1;374(1779):20180215. Epub 2019 Jul 1.

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California San Francisco, San Francisco, CA, USA.

A growing body of work describes how physical forces in and around cells affect their growth, proliferation, migration, function and differentiation into specialized types. How cells receive and respond biochemically to mechanical signals is a process termed mechanotransduction. Disease may arise if a disruption occurs within this mechanism of sensing and interpreting mechanics. Cancer, cardiovascular diseases and developmental defects, such as during the process of neural tube formation, are linked to changes in cell and tissue mechanics. A breakdown in normal tissue and cellular forces activates mechanosignalling pathways that affect their function and can promote disease progression. The recent advent of high-resolution techniques enables quantitative measurements of mechanical properties of the cell and its extracellular matrix, providing insight into how mechanotransduction is regulated. In this review, we will address the standard methods and new technologies available to properly measure mechanical properties, highlighting the challenges and limitations of probing different length-scales. We will focus on the unique environment present throughout the development and maintenance of the central nervous system and discuss cases where disease, such as brain cancer, arises in response to changes in the mechanical properties of the microenvironment that disrupt homeostasis. This article is part of a discussion meeting issue 'Forces in cancer: interdisciplinary approaches in tumour mechanobiology'.
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http://dx.doi.org/10.1098/rstb.2018.0215DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6627022PMC
August 2019

The Extracellular Matrix Modulates the Metastatic Journey.

Dev Cell 2019 05;49(3):332-346

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California, San Francisco, San Francisco, CA, USA; Departments of Radiation Oncology and Bioengineering and Therapeutic Sciences, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, and UCSF Helen Diller Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA, USA. Electronic address:

The extracellular matrix is perturbed in tumors. The tumor matrix promotes the growth, survival, and invasion of the cancer and modifies fibroblast and immune cell behavior to drive metastasis and impair treatment. Here, we discuss how the tumor matrix regulates metastasis by fostering tumor cell invasion into the stroma and migration toward the vasculature. We describe the role of the tumor matrix in cancer cell intravasation and vascular dissemination. We examine the impact of the matrix on disseminated tumor cell extravasation and on tumor dormancy and metastatic outgrowth. Finally, we discuss the clinical outcome of therapeutics that normalize tumor-matrix interactions.
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http://dx.doi.org/10.1016/j.devcel.2019.03.026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6527347PMC
May 2019

Spatiotemporal mosaic self-patterning of pluripotent stem cells using CRISPR interference.

Elife 2018 10 9;7. Epub 2018 Oct 9.

Gladstone Institute of Cardiovascular Disease, San Francisco, United States.

Morphogenesis involves interactions of asymmetric cell populations to form complex multicellular patterns and structures comprised of distinct cell types. However, current methods to model morphogenic events lack control over cell-type co-emergence and offer little capability to selectively perturb specific cell subpopulations. Our system interrogates cell-cell interactions and multicellular organization within human induced pluripotent stem cell (hiPSC) colonies. We examined effects of induced mosaic knockdown of molecular regulators of cortical tension (ROCK1) and cell-cell adhesion (CDH1) with CRISPR interference. Mosaic knockdown of ROCK1 or CDH1 resulted in differential patterning within hiPSC colonies due to cellular self-organization, while retaining an epithelial pluripotent phenotype. Knockdown induction stimulates a transient wave of differential gene expression within the mixed populations that stabilized in coordination with observed self-organization. Mosaic patterning enables genetic interrogation of emergent multicellular properties, which can facilitate better understanding of the molecular pathways that regulate symmetry-breaking during morphogenesis.
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http://dx.doi.org/10.7554/eLife.36045DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6177255PMC
October 2018

A tension-mediated glycocalyx-integrin feedback loop promotes mesenchymal-like glioblastoma.

Nat Cell Biol 2018 10 10;20(10):1203-1214. Epub 2018 Sep 10.

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California San Francisco, San Francisco, CA, USA.

Glioblastoma multiforme (GBMs) are recurrent lethal brain tumours. Recurrent GBMs often exhibit mesenchymal, stem-like phenotypes that could explain their resistance to therapy. Analyses revealed that recurrent GBMs have increased tension and express high levels of glycoproteins that increase the bulkiness of the glycocalyx. Studies showed that a bulky glycocalyx potentiates integrin mechanosignalling and tissue tension and promotes a mesenchymal, stem-like phenotype in GBMs. Gain- and loss-of-function studies implicated integrin mechanosignalling as an inducer of GBM growth, survival, invasion and treatment resistance, and a mesenchymal, stem-like phenotype. Mesenchymal-like GBMs were highly contractile and expressed elevated levels of glycoproteins that expanded their glycocalyx, and they were surrounded by a stiff extracellular matrix that potentiated integrin mechanosignalling. Our findings suggest that there is a dynamic and reciprocal link between integrin mechanosignalling and a bulky glycocalyx, implying a causal link towards a mesenchymal, stem-like phenotype in GBMs. Strategies to ameliorate GBM tissue tension offer a therapeutic approach to reduce mortality due to GBM.
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http://dx.doi.org/10.1038/s41556-018-0183-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6932748PMC
October 2018

Modeling Tissue Polarity in Context.

J Mol Biol 2018 09 25;430(19):3613-3628. Epub 2018 Jul 25.

Center for Bioengineering and Tissue Regeneration, Department of Surgery, University of California San Francisco, San Francisco, CA 94143, USA; Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA 94143, USA; Department of Radiation Oncology, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California San Francisco, San Francisco, CA 94143, USA; Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San Francisco, CA 94143, USA. Electronic address:

Polarity is critical for development and tissue-specific function. However, the acquisition and maintenance of tissue polarity is context dependent. Thus, cell and tissue polarity depend on cell adhesion which is regulated by the cytoskeleton and influenced by the biochemical composition of the extracellular microenvironment and modified by biomechanical cues within the tissue. These biomechanical cues include fluid flow induced shear stresses, cell-density and confinement-mediated compression, and cellular actomyosin tension intrinsic to the tissue or induced in response to morphogens or extracellular matrix stiffness. Here, we discuss how extracellular matrix stiffness and fluid flow influence cell-cell and cell-extracellular matrix adhesion and alter cytoskeletal organization to modulate cell and tissue polarity. We describe model systems that when combined with state of the art molecular screens and high-resolution imaging can be used to investigate how force modulates cell and tissue polarity.
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http://dx.doi.org/10.1016/j.jmb.2018.07.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6150793PMC
September 2018
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