Abstract A49: A dual blockade of N-CoR2- and immune checkpoints induces complete remissions in treatment-refractory tumors

Background: The majority of human malignant tumors are resistant or only partially respond to conventional chemotherapy (C/T) or immunotherapy (I/T) such as immune checkpoint inhibitors (ICIs). Irrespective of the treatments, efficient tumor-cell killing requires amplification of inflammatory signaling, which, however, is tightly regulated by various “checkpoint” mechanisms evolved by epithelial cells to prevent excessive tissue damage induced by virus and immune attack. Novel approaches to disable theses conserved and cell-intrinsic inflammation checkpoints may provide breakthrough and “tumor-agnostic” strategies to circumvent the innate treatment resistance to unleash the full potential of C/T and I/T in treatment-refractory and highly lethal malignant tumors, such as triple-negative breast cancer (TNBC), pancreatic ductal adenocarcinoma (PDAC), and glioblastoma multiform (GBM).

Materials and Methods: We designed and conducted integrated genomic and proteomic screening combined with molecular and functional studies to identify conserved anti-inflammatory pathways that mediate innate and cell-intrinsic resistance to C/T and I/T agents. Preclinical studies were used to validate a gene therapy strategy to disable the inflammation-checkpoint identified from this process.

Results: We uncovered that the cytotoxic and immunogenic death induced by C/T and I/T agents is constrained by repression of a toll-like receptor-2 (TLR-2)/TLR-3- and NF-kB-induced interferon regulatory factor-1 (IRF-1) and interferon (IFN)-gamma anti-viral response program in various malignant tumor cells, including breast cancer, PDAC and GBM. Loss- and gain-of-function studies implicated that co-repressor-2 (N-CoR2) co-translocated with NF-kB p50 into cell nuclei in response to therapy, wherein it serves as an epigenetic checkpoint of this inflammation program by mediating a histone deacetylase-dependent chromatin remodeling and repression of a specific panel of proinflammatory and proapoptotic genes. Thus, high N-CoR2 expression predicts treatment refractoriness and poor prognosis in neoadjuvant or adjuvant-treated breast cancer patients. Blockade of the epigenetic checkpoint function of N-CoR2 by a small decoy of N-CoR2 hypersensitized malignant cells to assorted C/T agents, death ligands, and IFN-gamma. Consistently, intratumoral delivery of the N-CoR2 checkpoint blockade dramatically potentiated systemic C/T and ICI therapies, including anti-PD-1 and anti-CTLA-4 antibodies, and completely halted tumor growth or induced remissions in orthotopic and patient-derived xenograft models of TNBC and GBM.

Conclusion: Our findings suggest that malignant tumors can access intrinsically conserved anti-inflammatory mechanisms that enable them to escape from C/T and I/T. As such, strategies that can override this defense program constitute novel antitumor gene therapies that may be applied to overcome resistance in treatment-refractory tumors and improve patient prognosis.

Citation Format: Kelvin Tsai, Valerie M. Weaver. A dual blockade of N-CoR2- and immune checkpoints induces complete remissions in treatment-refractory tumors [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A49.

Fibrosis and cancer: A strained relationship

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.

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

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.

Controlled modelling of human epiblast and amnion development using stem cells

Early human embryonic development involves extensive lineage diversification, cell-fate specification and tissue patterning¹. Despite its basic and clinical importance, early human embryonic development remains relatively unexplained owing to interspecies divergence^2,3 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.

Abstract 5184: N-CoR2 epigenetically regulates adhesion-dependent branching morphogenesis and its loss correlates with malignant progression of the mammary gland

Branching morphogenesis depends upon extracellular matrix remodeling and dynamic cell-cell and cell-extracellular matrix interactions, although how this developmental program is coordinated remains unclear. Expression profiling of mammary tissue at different stages of branching morphogenesis combined with histological and functional studies identified the histone deacetylase (HDAC) regulator, nuclear receptor co-repressor 2 (N-CoR2), as a key orchestrator of adhesion-dependent branching morphogenesis in the mammary gland. Molecular studies revealed that N-CoR2 actively represses fibronectin (FN) and thrombospondin-1 (THBS-1) promoter accessibility in an HDAC-dependent manner. Consistently, histological analysis revealed that N-CoR2 is abundantly expressed in the luminal epithelial cells localized along the outer rim of invading terminal end buds (TEB) and that its expression is lowest at sites of TEB branching bifurcation. In addition, reducing N-CoR2 expression drove the scattering of human mammary acini in vitro and promoted promiscuous branching of humanized mouse mammary tissue in vivo, suggesting that downregulation of N-CoR2 is required for branching morphogenesis in mammary gland. Furthermore, downregulation of N-CoR2 in breast cancer cells increased the expression of both FN and THBS-1 and reduced the expression of E-cadherin and enhanced the migratory capability of breast cancer cells. Intriguingly, immunohistochemical and clinical correlative analysis indicated that loss of N-CoR2 correlates with perturbed cell-cell and enhanced cell-ECM adhesion and acquisition of an invasive phenotype and local lymph node metastasis in a subset of breast carcinomas. These findings suggest N-CoR2 may epigenetically regulate adhesion-dependent branching morphogenesis in the mammary gland and that its loss could promote malignant progression of some breast cancers.

Citation Format: Shenq-Shyang Huang, Valerie M. Weaver, Kelvin K.C. Tsai. N-CoR2 epigenetically regulates adhesion-dependent branching morphogenesis and its loss correlates with malignant progression of the mammary gland [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5184.

Abstract 1900: A tension-mediated glycocalyx feedback loop promotes glioblastoma

A considerable challenge in glioblastoma (GBM) therapy is treatment resistance and tumor recurrence, resulting in dismal patient prognosis. GBM aggression and recurrence is often associated with a mesenchymal phenotype, increased expression of glycoproteins and the presence of glioma-initiating “stem-like” cells. Using patient-derived xenograft models, and immune competent syngeneic and transgenic glioma mouse models, we show that aggressive mesenchymal-like GBMs, reminiscent of recurrent GBM, are mechanically stiffer, present with a bulky glycocalyx and demonstrate a stem-like phenotype. We report that the more aggressive mesenchymal GBMs show increased mechanical signaling and contractility, and their tumors are surrounded by a stiffer ECM that maintains and even further enhances integrin mechanosignaling. Since a large proportion of these bulky glycoproteins are also stem markers, upregulation of the glycoproteins and their modulators leads to enhanced GBM stem-ness. This was evident both in our mesenchymal models of GBM as well as multiple patient datasets which compared paired primary and recurrent GBM RNA sequencing and protein data. In addition to stem-ness, we show that the mechanically “enhanced” GBMs also foster a differential immune landscape, infiltrated by type 2 macrophages, believed to be pro-tumorigenic and immune evasive. Our findings suggest that there is a dynamic and reciprocal link between integrin mechanosignaling, the GBM immune landscape and a bulky glycocalyx, which promotes a mesenchymal, stem-like phenotype and likely recurrence in GBM patients. Thus, therapeutic strategies to target GBM tissue tension could prevent recurrence, reduce mortality and improve patient outcome.

Citation Format: Shelly Kaushik, James Matthew Barnes, Russell O. Bainer, Jason K. Sa, Elliot C. Woods, Fuiboon Kai, Jonathon N. Lakins, Joanna J. Phillips, Valerie M. Weaver. A tension-mediated glycocalyx feedback loop promotes glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1900.

Abstract 1028: Extracellular matrix dimensionality reduces cellular cortical tension to stimulate pro-survival signaling in mammary epithelial cells

Tumor dormancy is a clinical phenomenon in which disseminated tumor cells remain asymptomatic and undetectable over a long period of time. Dormant cells are able to maintain quiescence in hostile microenvironments, escape frontline cancer therapies and evade the immune system, as well as their propensity to reactivate from latency and cause metastatic relapse. Although tumor dormancy is an important problem in the treatment of cancer, the molecular mechanisms underlying this complex process remain unclear. Because dormant cells are frequently found surrounded by a laminin-rich ECM, we hypothesized that ECM dimensionality intrinsically affects cell behaviors that predispose to dormancy. Accordingly, we assessed the biophysical and biochemical response of mammary epithelial cells (MECs) to compliant polyacrylamide (PA) gels and micropatterned surfaces in which ligand presentation and ECM dimensionality were modulated to recapitulate different ECM landscapes. Using traction force microscopy, atomic force microscopy indentation, and laser ablation studies, we found that a 3D ECM led to a drop in cortical tension of MECs. Computational modeling predicted that reduced cortical tension should lead to an increase in the number and/or residence time of actin protrusions as well as a net increase in negative membrane curvature. To test the prediction, we ectopically expressed F-actin and plasma membrane markers in MECs to examine the plasma membrane topography and actin protrusion dynamics. Indeed, MECs in 3D ECM had longer and more stable actin protrusions and more negative membrane curvature inducing proteins, including Exo70, at the plasma membrane. The enrichment of Exo70 at the plasma membrane accompanied the activation of Arf6, which led to an increase in Rac/p38 pro-survival signaling pathway. Consistently, we found that the non-spread cells were able to survive in 3D ECM but the non-spread MECs plated on either a soft 2D PA gels or rigid micropatterned adhesive islands died. We next examined if reduced cortical tension is sufficient to activate pro-survival pathways in cells in 2D. Importantly, pharmacological inhibition of myosin in non-spread MECs on a 2D ECM, which causes loss of cortical tension, increased negative membrane curvature and cell viability. Conversely, genetic knockdown of the negative curvature-inducing protein Exo70 compromised MEC survival in a 3D ECM. Our results provide the first evidence demonstrating that ECM dimensionality alters the biophysical properties of cells to modulate plasma membrane curvature and activate pro-survival signaling pathways. Our findings also offer a unique perspective for why Arf6 and Rac GTPases have been implicated in cancer aggression and suggest that targeting the tissue ECM or cellular cortical tension may provide a novel therapeutic approach to target dormant cells.

Citation Format: FuiBoon Kai, Guanqing Ou, Alexandra Long, Wei Guo, Richard Tourdot, Ravi Radhakrishnan, Christopher Chen, Sophie Dumont, Valerie M. Weaver. Extracellular matrix dimensionality reduces cellular cortical tension to stimulate pro-survival signaling in mammary epithelial cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1028.

Tissue mechanics, an important regulator of development and disease

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'.

Abstract P5-07-13: Conceptual model of transdisciplinary science - Advocacy collaboration for the physical sciences and oncology: A case study focusing on breast density, biomarker discovery, and emerging therapeutics

BACKGROUND: What happens when you mix the foundations of tissue mechanics with advocacy? In a shared quest for exciting scientific frontiers, Bay Area physical scientists, clinical researchers, and advocates work in dynamic symbiotic relationships to integrate concepts drawn from their respective fields. Focusing on the mechanobiology of tumor progression in breast cancer, researchers and advocates are co-creating system change interventions for revamping convergent research processes.

METHODS:As vital catalysts of transdisciplinary innovation, advocates affiliated with the National Cancer Institute (NCI) Physical Sciences and Oncology Network (PS-ON) applied core principles that synergize with the evolving disciplines of Implementation Science (IS) and the Science of Team Science (STS). Diverse methodologies to describe the intersections of physical sciences, breast density, biomarker discovery, emerging therapeutics and advocacy are presented. Additionally, we introduce a theoretical framework and conceptual puzzle illustrating multimethod science advocacy engagement strategies, a typology of contextual factors influencing collaboration, as well as the antecedents, processes, strategic priorities, and overall potential impacts of collaborative transdisciplinary science advocacy exchanges.

RESULTS:Through proactive participation in four areas: 1) research and programmatic support, 2) education and outreach, 3) policy and strategy, and 4) representation and advisory, advocates, representing patient/consumer perspectives, worked toward a common set of goals with researchers and clinicians in determining how tumor microenvironments regulate cancer initiation and behavior through interactions among cell types (e.g., initiated cells, activated stromal cells, and components of the extracellular matrix). Applying NCI Office of Advocacy Relations (OAR) and NCI PS-ON Advocacy Working Group goals for strategic innovation, collaborative execution, and ethical codes of conduct, researchers and advocates codeveloped guiding conceptual frameworks based on organizational foundations, systems readiness, leadership commitment to change, and transdisciplinary levers to promote shared governance, bidirectional collaboration, advocacy inclusion, and the prioritization of research addressing questions of importance to patients.

DISCUSSION: Embedding advocate patient/consumer evidentiary and experiential insights/perspectives regarding mechanics-directed research priorities and clinical interventions in the early phase of convergent research efforts contributes to our understanding of the important role of the physical organization in cell-to-cell contacts, tissue architecture, tumor microenviroments, and mechanical properties in response to therapy. Notably, catalyzing and leveraging advocate engagement across the research continuum provides novel opportunities for advancing institutional changes, spurring unique training/mentoring exchanges, and fostering innovative research and translational opportunities.

Citation Format: Samson S, Northey JJ, Baas C, Weaver VM. Conceptual model of transdisciplinary science - Advocacy collaboration for the physical sciences and oncology: A case study focusing on breast density, biomarker discovery, and emerging therapeutics [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-07-13.

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

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 in vitro 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.

Embryos begin as a collection of similar cells, which progress in stages to form a huge variety of cell types in particular arrangements. These patterns of cells give rise to the different tissues and organs that make up the body.

Although we often use ‘model’ organisms such as mice and frogs to study how embryos develop, our species has evolved unique ways to control organ development. Investigating these processes is difficult: we cannot experiment on human embryos, and our development is hard to recreate in test tubes. As a result, we do not fully understand how developing human cells specialize and organize.

Libby et al. have now created a new system to study how different genes control cell organization. The system uses human pluripotent stem cells – cells that have the ability to specialize into any type of cell. Some of the stem cells are modified using a technique called inducible CRISPR interference, which makes it possible to reduce the activity of certain genes in these cells.

Libby et al. used this technique to investigate how changes to the activity of two genes – called ROCK1 and CDH1 – affect how a mixed group of stem cells organized themselves. Cells that lacked ROCK1 formed bands near the edges of the group. Cells that lacked CDH1 segregated themselves from other cells, forming ‘islands’ inside the main group. The cells retained their ability to specialize into any type of cell after forming these patterns. However, specific groups of cells were more likely to become certain cell types.

The method developed by Libby et al. can be used to study a range of complex tissue development and cell organization processes. Future work could create human tissue model systems for research into human disease or drug development.

Modeling Tissue Polarity in Context

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.

Fibronectin rescues estrogen receptor α from lysosomal degradation in breast cancer cells

Estrogen receptor α (ERα) is expressed in tissues as diverse as brains and mammary glands. In breast cancer, ERα is a key regulator of tumor progression. Therefore, understanding what activates ERα is critical for cancer treatment in particular and cell biology in general. Using biochemical approaches and superresolution microscopy, we show that estrogen drives membrane ERα into endosomes in breast cancer cells and that its fate is determined by the presence of fibronectin (FN) in the extracellular matrix; it is trafficked to lysosomes in the absence of FN and avoids the lysosomal compartment in its presence. In this context, FN prolongs ERα half-life and strengthens its transcriptional activity. We show that ERα is associated with β1-integrin at the membrane, and this integrin follows the same endocytosis and subcellular trafficking pathway triggered by estrogen. Moreover, ERα⁺ vesicles are present within human breast tissues, and colocalization with β1-integrin is detected primarily in tumors. Our work unravels a key, clinically relevant mechanism of microenvironmental regulation of ERα signaling.

Abstract LB-055: Discoidin domain receptor 1 (DDR1) ablation promotes tissue fibrosis and hypoxia to induce aggressive, basal-like breast cancer

Breast cancer studies implicate the discoidin domain receptor 1 (DDR1) in both pro- and anti-tumor roles. DDR1 is often overexpressed in breast tumors and its activation by collagen promotes tumor cell invasion and potentiates metastatic colonization by cell lines. However, DDR1 transfection into low DDR1 expressing tumor cells hinders cell migration. Moreover, low expression of DDR1 correlates with higher grade human tumors and associates with worse prognosis. To better understand the role of DDR1 in breast tumor progression and metastasis, we established a DDR1 knockout and crossed it into the MMTV-PyMT mouse. DDR1 loss compromised luminal cell adhesion and expanded the basal/myoepithelial population in adult mice. PyMT DDR1-/- tumors grew faster and had increased lung metastasis both in size and number of metastatic colonies. The DDR1-/- tumors broadly exhibited a more basal-like phenotype with enhanced fibrosis and were more hypoxic. Furthermore, these tumors contained more CD90+ CD24+ tumor cells and more K8+ K14+ cells surrounding necrotic regions. Taken together these data suggest DDR1 loss confers a growth advantage favoring basal cell expansion via impaired luminal adhesion and enhanced basal differentiation leading to more aggressive, basal-like disease.

Citation Format: Allison P. Drain, Ken Takai, Devon A. Lawson, Laurie E. Littlepage, Marcela Karpuj, Kai Kessenbrock, Annie Le, Kenichi Inoue, Valerie M. Weaver, Zena Werb. Discoidin domain receptor 1 (DDR1) ablation promotes tissue fibrosis and hypoxia to induce aggressive, basal-like breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-055.

Abstract 4767: Regional strategies for expanding the evolving continuum of Physical Sciences-Oncology Network (PS-ON) research advocacy experiences

Background: The National Cancer Institute (NCI) Physical Sciences-Oncology Network (PS-ON), initiated in 2009, is an interdisciplinary hub currently consisting of eighteen regions across the nation to support the emergence of new scientific frontiers, principles, and opportunities within physical sciences and oncology. Based on the belief that the increasing momentum for cross-disciplinary connectivity between biologists, physicists, mathematicians, chemists, biomedical engineers, and oncologists would be enriched and enhanced by vigorous and diverse public and/or advocacy support, the PS-ON leadership, at program inception, incorporated the advocate voice in setting a national research agenda.

Methods: While the regional advocacy programs operate independently and utilize multilevel, multimethod strategies to expand the evolving umbrella of research advocacy experiences, they are connected through an administrative structure that communicates NCI program priorities to enhance capacity in the approaches utilized across the eighteen PS-ON regions.

Impact: As integral team members, advocates bring real-time diverse patient experiences, diverse professional expertise, and concerns into pioneering, innovative research practices. PS-ON regional engagement/communication strategies include: 1) integrating advocate perspectives to shape basic science research agendas, 2) developing conceptual models/roadmaps to holistic engagement focusing on organizational foundations and best practice strategies, 3) applying guiding frameworks and toolkits for setting the terms of principled engagement/shared governance/bidirectional collaboration, 4) implementing education, outreach, and professional development programs for early-stage investigators, students, and patient communities, and 5) translating, communicating and disseminating laboratory innovations into society.

Discussion: To better understand and fully address the complexities of intersecting physical sciences and oncology advocacy engagement, we explore the unique culture and guidelines set by selected participating institutions. Meeting key challenges regarding programmatic scope and policy impact requires a shift to a new, rapidly evolving paradigm. In parallel to incentives and policy measures created through federal and professional organizations, we offer recommendations for strengthening regional programs and encouraging equitable partnerships for advocates at earlier stages of research to help propel convergent science innovation.

Citation Format: Susan Samson, Nastaran Zahir, Sheila M. Judge, Stuart Cornew, Bob Riter, Jeri Francoeur, Anne Meyn, Laurie Cynkin, Jason J. Northey, Valerie M. Weaver, Carole Baas. Regional strategies for expanding the evolving continuum of Physical Sciences-Oncology Network (PS-ON) research advocacy experiences [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4767.

Antisecretory Factor-Mediated Inhibition of Cell Volume Dynamics Produces Antitumor Activity in Glioblastoma

Interstitial fluid pressure (IFP) presents a barrier to drug uptake in solid tumors, including the aggressive primary brain tumor glioblastoma (GBM). It remains unclear how fluid dynamics impacts tumor progression and can be targeted therapeutically. To address this issue, a novel telemetry-based approach was developed to measure changes in IFP during progression of GBM xenografts. Antisecretory factor (AF) is an endogenous protein that displays antisecretory effects in animals and patients. Here, endogenous induction of AF protein or exogenous administration of AF peptide reduced IFP and increased drug uptake in GBM xenografts. AF inhibited cell volume regulation of GBM cells, an effect that was phenocopied in vitro by the sodium-potassium-chloride cotransporter 1 (SLC12A2/NKCC1) inhibitor bumetanide. As a result, AF induced apoptosis and increased survival in GBM models. In vitro, the ability of AF to reduce GBM cell proliferation was phenocopied by bumetanide and NKCC1 knockdown. Next, AF's ability to sensitize GBM cells to the alkylating agent temozolomide, standard of care in GBM patients, was evaluated. Importantly, combination of AF induction and temozolomide treatment blocked regrowth in GBM xenografts. Thus, AF-mediated inhibition of cell volume regulation represents a novel strategy to increase drug uptake and improve outcome in GBM. Mol Cancer Res; 16(5); 777-90. ©2018 AACR.

The Physical and Biochemical Properties of the Extracellular Matrix Regulate Cell Fate

The extracellular matrix is a complex network of hydrated macromolecular proteins and sugars that, in concert with bound soluble factors, comprise the acellular stromal microenvironment of tissues. Rather than merely providing structural information to cells, the extracellular matrix plays an instructive role in development and is critical for the maintenance of tissue homeostasis. In this chapter, we review the composition of the extracellular matrix and summarize data illustrating its importance in embryogenesis, tissue-specific development, and stem cell differentiation. We discuss how the biophysical and biochemical properties of the extracellular matrix ligate specific transmembrane receptors to activate intracellular signaling that alter cell shape and cytoskeletal dynamics to modulate cell growth and viability, and direct cell migration and cell fate. We present examples describing how the extracellular matrix functions as a highly complex physical and chemical entity that regulates tissue organization and cell behavior through a dynamic and reciprocal dialogue with the cellular constituents of the tissue. We suggest that the extracellular matrix not only transmits cellular and tissue-level force to shape development and tune cellular activities that are key for coordinated tissue behavior, but that it is itself remodeled such that it temporally evolves to maintain the integrated function of the tissue. Accordingly, we argue that perturbations in extracellular matrix composition and structure compromise key developmental events and tissue homeostasis, and promote disease.

New Horizons in Advocacy Engaged Physical Sciences and Oncology Research

To address cancer as a multifaceted adaptive system, the increasing momentum for cross-disciplinary connectivity between cancer biologists, physical scientists, mathematicians, chemists, biomedical engineers, computer scientists, clinicians, and advocates is fueling the emergence of new scientific frontiers, principles, and opportunities within physical sciences and oncology. In parallel to highlighting the advances, challenges, and acceptance of advocates as credible contributors, we offer recommendations for addressing real world hurdles in advancing equitable partnerships among advocacy stakeholders.

Compartment resolved proteomics reveals a dynamic matrisome in a biomechanically driven model of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a severe fibrotic component that compromises treatment, alters the immune cell profile and contributes to patient mortality. It has been shown that early on in this process, dynamic changes in tissue biomechanics play an integral role in supporting pancreatic cancer development and progression. Despite the acknowledgement of its importance, a granular view of how stromal composition changes during the course of PDAC progression remains largely unknown. To mimic the quasi-mesenchymal phenotype and pronounced desmoplastic response observed clinically, we utilized a genetically engineered mouse model of PDAC that is driven by a Kras^G12D mutation and loss of Tgfbr2 expression. Application of compartment resolved proteomics revealed that PDAC progression in this KTC model is associated with dynamic stromal alterations that are indicative of a wound healing program. We identified an early provisional matricellular fibrosis that was accompanied by markers of macrophage activation and infiltration, consistent with the inflammatory phase of wound healing. At 20 weeks a proliferative phenotype was observed with increased fibroblast markers, further collagen deposition and loss of basement membrane and native cell markers.

Feeling Stress: The Mechanics of Cancer Progression and Aggression

The tumor microenvironment is a dynamic landscape in which the physical and mechanical properties evolve dramatically throughout cancer progression. These changes are driven by enhanced tumor cell contractility and expansion of the growing tumor mass, as well as through alterations to the material properties of the surrounding extracellular matrix (ECM). Consequently, tumor cells are exposed to a number of different mechanical inputs including cell–cell and cell-ECM tension, compression stress, interstitial fluid pressure and shear stress. Oncogenes engage signaling pathways that are activated in response to mechanical stress, thereby reworking the cell's intrinsic response to exogenous mechanical stimuli, enhancing intracellular tension via elevated actomyosin contraction, and influencing ECM stiffness and tissue morphology. In addition to altering their intracellular tension and remodeling the microenvironment, cells actively respond to these mechanical perturbations phenotypically through modification of gene expression. Herein, we present a description of the physical changes that promote tumor progression and aggression, discuss their interrelationship and highlight emerging therapeutic strategies to alleviate the mechanical stresses driving cancer to malignancy.

Discoidin domain receptor 1 (DDR1) ablation promotes tissue fibrosis and hypoxia to induce aggressive basal-like breast cancers

Here, Takai et al. researched the function of discoidin domain receptor 1 (DDR1), a member of the subfamily of receptor tyrosine kinases activated by collagens that is overexpressed in breast and other carcinoma cells. Using bioinformatics analysis, breast cancer cell lines, and knockout mice, they demonstrate that DDR1 ablation leads to aggressive breast cancer, and their findings suggest that the absence of DDR1 provides a growth and adhesion advantage that favors the expansion of basal cells, potentiates fibrosis, and enhances necrosis/hypoxia and basal differentiation of transformed cells to increase their aggression and metastatic potential.

The discoidin domain receptor 1 (DDR1) is overexpressed in breast carcinoma cells. Low DDR1 expression is associated with worse relapse-free survival, reflecting its controversial role in cancer progression. We detected DDR1 on luminal cells but not on myoepithelial cells of DDR1^+/+ mice. We found that DDR1 loss compromises cell adhesion, consistent with data that older DDR1^−/− mammary glands had more basal/myoepithelial cells. Basal cells isolated from older mice exerted higher traction forces than the luminal cells, in agreement with increased mammary branches observed in older DDR1^−/− mice and higher branching by their isolated organoids. When we crossed DDR1^−/− mice with MMTV-PyMT mice, the PyMT/DDR1^−/− mammary tumors grew faster and had increased epithelial tension and matricellular fibrosis with a more basal phenotype and increased lung metastases. DDR1 deletion induced basal differentiation of CD90⁺CD24⁺ cancer cells, and the increase in basal cells correlated with tumor cell mitoses. K14⁺ basal cells, including K8⁺K14⁺ cells, were increased adjacent to necrotic fields. These data suggest that the absence of DDR1 provides a growth and adhesion advantage that favors the expansion of basal cells, potentiates fibrosis, and enhances necrosis/hypoxia and basal differentiation of transformed cells to increase their aggression and metastatic potential.

Targeting the cancer-associated fibroblasts as a treatment in triple-negative breast cancer

Increased collagen expression in tumors is associated with increased risk of metastasis, and triple-negative breast cancer (TNBC) has the highest propensity to develop distant metastases when there is evidence of central fibrosis. Transforming growth factor-β (TGF-β) ligands regulated by cancer-associated fibroblasts (CAFs) promote accumulation of fibrosis and cancer progression. In the present study, we have evaluated TNBC tumors with enhanced collagen to determine whether we can reduce metastasis by targeting the CAFs with Pirfenidone (PFD), an anti-fibrotic agent as well as a TGF-β antagonist. In patient-derived xenograft models, TNBC tumors exhibited accumulated collagen and activated TGF-β signaling, and developed lung metastasis. Next, primary CAFs were established from 4T1 TNBC homograft tumors, TNBC xenograft tumors and tumor specimens of breast cancer patients. CAFs promoted primary tumor growth with more fibrosis and TGF-β activation and lung metastasis in 4T1 mouse model. We then examined the effects of PFD in vitro and in vivo. We found that PFD had inhibitory effects on cell viability and collagen production of CAFs in 2D culture. Furthermore, CAFs enhanced tumor growth and PFD inhibited the tumor growth induced by CAFs by causing apoptosis in the 3D co-culture assay of 4T1 tumor cells and CAFs. In vivo, PFD alone inhibited tumor fibrosis and TGF-β signaling but did not inhibit tumor growth and lung metastasis. However, PFD inhibited tumor growth and lung metastasis synergistically in combination with doxorubicin. Thus, PFD has great potential for a novel clinically applicable TNBC therapy that targets tumor-stromal interaction.

Abstract P5-02-02: Second harmonic generation in combination with nuclear morphometry in the evaluation of DCIS

Purpose/Objective: Collagen is a major extracellular matrix (ECM) constituent in normal breast and is extensively remodeled in breast carcinoma. Therefore, features of remodeled collagen in the stroma adjacent to ductal carcinoma in situ (DCIS) could indicate cancer progression. The major objective of this study is to identify potential tumor-associated collagen signatures unique to DCIS that will allow us to predict progression based on the collagen texture and nuclear morphology. In this present study, we develop two image analysis pipelines (SHG Texture Extraction and H&E Nuclear Morphology Extractor) to quantify 1) stromal changes, 2) collagen signatures and 3) nuclear morphology from normal breast to DCIS in order to predict local breast cancer recurrence.

Method: We used second harmonic generation (SHG) images and H&E to analyze collagen features and to study nuclear morphology using a data set of 336 patients (from which 310 normal and 327 DCIS regions were imaged). The 336 patients were a subset of patients with pure DCIS taken from a case-control study. Clinical-pathologic factors were associated with risk of subsequent ipsilateral cancer (DCIS or invasive). The SHG framework consisted of collagen segmentation using 1) adaptive thresholding and 2) morphological operations. The H&E framework consisted of nuclear segmentation using adaptive thresholding and a maker-controlled watershed algorithm; and nuclear feature extractions including intensity, texture and morphology. Overall, the SHG framework segments collagen regions and computes textural features specifically at collagen regions. Furthermore, the H&E framework segments nuclei and computes nuclei morphology and textural features. These features were used in L1-regularized logistic regression to construct classification models to discriminate normal vs DCIS regions; and to distinguish regions from DCIS patients with vs. without local recurrences.

Results: In first experiment, we performed L1-regularized logistic regression to construct a classification model to discriminate normal vs DCIS regions. Our results suggest that using only SHG collagen features, this logistic model selected 19 significant features to build a classification model that achieved area under curve (AUC) 90% and accuracy 83% using 5-Fold cross validation. When H&E nuclei features are used, the logistic model selected 88 significant features and achieved AUC 91% and accuracy 86%. By combined both SHG and H&E features, the model achieved classification AUC 93% and accuracy 88%. By using L1-regularized logistic model with combined significant SHG and H&E features, we achieved AUC 59% with an accuracy of 61% for DCIS and recurrent DCIS regions.

Conclusions: Our study suggests that SHG and nuclear morphology features extracted from H&E can improve the classification of normal and DCIS regions. Overall, these results suggest that second harmonic generation and H&E nuclear morphology analysis could aid in the assessment of prognosis and risk of progression to invasive breast cancer.

Citation Format: Park CC, Irshad H, Ziaee S, Martin-Tuite P, Habel L, Weaver VM, Schnitt SJ, Beck AH. Second harmonic generation in combination with nuclear morphometry in the evaluation of DCIS [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-02-02.