The effects of monocytes on tumor cell extravasation in a 3D vascularized microfluidic model

Metastasis is the leading cause of cancer-related deaths. Recent developments in cancer immunotherapy have shown exciting therapeutic promise for metastatic patients. While most therapies target T cells, other immune cells, such as monocytes, hold great promise for therapeutic intervention. In our study, we provide primary evidence of direct engagement between human monocytes and tumor cells in a 3D vascularized microfluidic model. We first characterize the novel application of our model to investigate and visualize at high resolution the evolution of monocytes as they migrate from the intravascular to the extravascular micro-environment. We also demonstrate their differentiation into macrophages in our all-human model. Our model replicates physiological differences between different monocyte subsets. In particular, we report that inflammatory, but not patrolling, monocytes rely on actomyosin based motility. Finally, we exploit this platform to study the effect of monocytes, at different stages of their life cycle, on cancer cell extravasation. Our data demonstrates that monocytes can directly reduce cancer cell extravasation in a non-contact dependent manner. In contrast, we see little effect of monocytes on cancer cell extravasation once monocytes transmigrate through the vasculature and are macrophage-like. Taken together, our study brings novel insight into the role of monocytes in cancer cell extravasation, which is an important step in the metastatic cascade. These findings establish our microfluidic platform as a powerful tool to investigate the characteristics and function of monocytes and monocyte-derived macrophages in normal and diseased states. We propose that monocyte-cancer cell interactions could be targeted to potentiate the anti-metastatic effect we observe in vitro, possibly expanding the milieu of immunotherapies available to tame metastasis.

In Vitro Modeling of Mechanics in Cancer Metastasis

In addition to a multitude of genetic and biochemical alterations, abnormal morphological, structural, and mechanical changes in cells and their extracellular environment are key features of tumor invasion and metastasis. Furthermore, it is now evident that mechanical cues alongside biochemical signals contribute to critical steps of cancer initiation, progression, and spread. Despite its importance, it is very challenging to study mechanics of different steps of metastasis in the clinic or even in animal models. While considerable progress has been made in developing advanced in vitro models for studying genetic and biological aspects of cancer, less attention has been paid to models that can capture both biological and mechanical factors realistically. This is mainly due to lack of appropriate models and measurement tools. After introducing the central role of mechanics in cancer metastasis, we provide an outlook on the emergence of novel in vitro assays and their combination with advanced measurement technologies to probe and recapitulate mechanics in conditions more relevant to the metastatic disease.

Cell-Extracellular Matrix Mechanobiology: Forceful Tools and Emerging Needs for Basic and Translational Research

Extracellular biophysical cues have a profound influence on a wide range of cell behaviors, including growth, motility, differentiation, apoptosis, gene expression, adhesion, and signal transduction. Cells not only respond to definitively mechanical cues from the extracellular matrix (ECM) but can also sometimes alter the mechanical properties of the matrix and hence influence subsequent matrix-based cues in both physiological and pathological processes. Interactions between cells and materials in vitro can modify cell phenotype and ECM structure, whether intentionally or inadvertently. Interactions between cell and matrix mechanics in vivo are of particular importance in a wide variety of disorders, including cancer, central nervous system injury, fibrotic diseases, and myocardial infarction. Both the in vitro and in vivo effects of this coupling between mechanics and biology hold important implications for clinical applications.

In Vitro Microfluidic Models for Neurodegenerative Disorders

Microfluidic devices enable novel means of emulating neurodegenerative disease pathophysiology in vitro. These organ-on-a-chip systems can potentially reduce animal testing and substitute (or augment) simple 2D culture systems. Reconstituting critical features of neurodegenerative diseases in a biomimetic system using microfluidics can thereby accelerate drug discovery and improve our understanding of the mechanisms of several currently incurable diseases. This review describes latest advances in modeling neurodegenerative diseases in the central nervous system and the peripheral nervous system. First, this study summarizes fundamental advantages of microfluidic devices in the creation of compartmentalized cell culture microenvironments for the co-culture of neurons, glial cells, endothelial cells, and skeletal muscle cells and in their recapitulation of spatiotemporal chemical gradients and mechanical microenvironments. Then, this reviews neurodegenerative-disease-on-a-chip models focusing on Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. Finally, this study discusses about current drawbacks of these models and strategies that may overcome them. These organ-on-chip technologies can be useful to be the first line of testing line in drug development and toxicology studies, which can contribute significantly to minimize the phase of animal testing steps.

Crosstalk between developing vasculature and optogenetically engineered skeletal muscle improves muscle contraction and angiogenesis

Capillary networks surrounding skeletal muscle play an important role in not only supplying oxygen and nutrients but also in regulating the myogenesis and repair of skeletal muscle tissues. Herein, we model the early stages of 3D vascularized muscle fiber formation in vitro using a sequential molding technique to investigate interactions between angiogenesis of endothelial cells and myogenesis of skeletal muscle cells. Channelrhodopsin-2 C2C12 muscle fiber bundles and 3D vascular structures (600 μm diameter) were formed at 500 μm intervals in a collagen gel. Endothelial cells exhibited an emergent angiogenic sprouting behavior over several days, which was modulated by the muscle fiber bundle through the secretion of angiopoietin-1. Through a reciprocal response, myogenesis was also upregulated by interactions with the vascular cells, improving muscle contraction via angiopoetin-1/neuregulin-1 signaling. Moreover, continuous training of muscle tissue by optical stimulation induced significantly more angiogenic sprouting. This in vitro model could be used to better understand the formation of vascularized muscle tissues and to test the interactions between muscle growth, repair or training and angiogenesis for applications in tissue engineering and regenerative medicine.

Ex Vivo Profiling of PD-1 Blockade Using Organotypic Tumor Spheroids

Ex vivo systems that incorporate features of the tumor microenvironment and model the dynamic response to immune checkpoint blockade (ICB) may facilitate efforts in precision immuno-oncology and the development of effective combination therapies. Here, we demonstrate the ability to interrogate ex vivo response to ICB using murine- and patient-derived organotypic tumor spheroids (MDOTS/PDOTS). MDOTS/PDOTS isolated from mouse and human tumors retain autologous lymphoid and myeloid cell populations and respond to ICB in short-term three-dimensional microfluidic culture. Response and resistance to ICB was recapitulated using MDOTS derived from established immunocompetent mouse tumor models. MDOTS profiling demonstrated that TBK1/IKKε inhibition enhanced response to PD-1 blockade, which effectively predicted tumor response in vivo Systematic profiling of secreted cytokines in PDOTS captured key features associated with response and resistance to PD-1 blockade. Thus, MDOTS/PDOTS profiling represents a novel platform to evaluate ICB using established murine models as well as clinically relevant patient specimens.Significance: Resistance to PD-1 blockade remains a challenge for many patients, and biomarkers to guide treatment are lacking. Here, we demonstrate feasibility of ex vivo profiling of PD-1 blockade to interrogate the tumor immune microenvironment, develop therapeutic combinations, and facilitate precision immuno-oncology efforts. Cancer Discov; 8(2); 196-215. ©2017 AACR.See related commentary by Balko and Sosman, p. 143See related article by Deng et al., p. 216This article is highlighted in the In This Issue feature, p. 127.

Integrated Analysis of Intracellular Dynamics of MenaINV Cancer Cells in a 3D Matrix

The intracellular environment is composed of a filamentous network that exhibits dynamic turnover of cytoskeletal components and internal force generation from molecular motors. Particle tracking microrheology enables a means to probe the internal mechanics and dynamics. Here, we develop an analytical model to capture the basic features of the active intracellular mechanical environment, including both thermal and motor-driven effects, and show consistency with a diverse range of experimental microrheology data. We further perform microrheology experiments, integrated with Brownian dynamics simulations of the active cytoskeleton, on metastatic breast cancer cells embedded in a three-dimensional collagen matrix with and without the presence of epidermal growth factor to probe the intracellular mechanical response in a physiologically mimicking scenario. Our results demonstrate that EGF stimulation can alter intracellular stiffness and power output from molecular motor-driven fluctuations in cells overexpressing an invasive isoform of the actin-associated protein Mena.

Dynamic interplay between tumour, stroma and immune system can drive or prevent tumour progression

In the tumour microenvironment, cancer cells directly interact with both the immune system and the stroma. It is firmly established that the immune system, historically believed to be a major part of the body's defence against tumour progression, can be reprogrammed by tumour cells to be ineffective, inactivated, or even acquire tumour promoting phenotypes. Likewise, stromal cells and extracellular matrix can also have pro-and anti-tumour properties. However, there is strong evidence that the stroma and immune system also directly interact, therefore creating a tripartite interaction that exists between cancer cells, immune cells and tumour stroma. This interaction contributes to the maintenance of a chronically inflamed tumour microenvironment with pro-tumorigenic immune phenotypes and facilitated metastatic dissemination. A comprehensive understanding of cancer in the context of dynamical interactions of the immune system and the tumour stroma is therefore required to truly understand the progression toward and past malignancy.

Abstract 5814: Engineered microfluidic 3D human microvasculature identifies Talin-1-dependent adhesion and FAK activation as the key promoter of cancer cell trans-endothelial migration

In extravasation cancer cells and vascular niche are involved in a tight cross-talk which has been defined as the rate-regulating event for metastases establishment [1]. Recent, animal studies support the hypothesis that metastatic deficiency lies in focal adhesion complex alterations, however, it still needs to be elucidated which are the specific regulators of each event composing extravasation. Focal adhesion proteins Talin-1 (TLN-1) and Focal Adhesion Kinase (FAK) are up-regulated in breast cancer. Both targets due to their structural and functional role, dramatically influence cancer mechanotransduction leading to endothelial junction disruption, critical in extravasation process [2]. Here, we generated ad hoc engineered models for each extravasation step allowing single cell behavior analyses through high resolution real time imaging in a reliable and quantitative way in a physiological environment. Through this novel approach we analyzed the effect of TLN-1 and FAK and their genetic and chemical inhibition in breast cancer extravasation. The 3D-microfluidic vasculature displayed maturation markers and physiological permeability (1.5±0.76*10-6cm/s) and allowed cancer cell injection through the hollow vessels. Western blot confirmed TLN-1 and FAK knock down (KD) in MDA-MB231. Both targets significantly affected morphology and proliferation (p<0.001). We demonstrated the involvement of both targets in adhesion to the endothelium (p<0.001). Trans endothelial migration (TEM) was decreased in TLN-1 KD (p<0.05) and in FAK KD (P<0.01). Both TLN-1 and FAK KD cells were trapped into the vessels and were not able to extend pseudopodia. Cancer migration tracking in 3D matrix was statistically lower in both KD (p<0.001). The calculated ratios of adhesion/TEM and invasion/TEM were lower in TLN-1 compared to FAK KD, demonstrating that TLN-1 plays a major role in adhesion to endothelium and early invasion while FAK was identified as the main driver in TEM. Additive (TLN-1 and FAK) KD did not show significant difference respect to the target that mostly affected adhesion and invasion demonstrating TLN-1 role in these events. Additive KD was statistically lower compared to TLN-1 KD (P<0.05), supporting FAK crucial role in TEM. Inhibition of TLN-1 and FAK phosphorylation revealed that actin polymerization and pseudopodia formation (required for extravasation) were dependent by their structural role and were independent by their phosphorylation. However, the inhibition of FAK activity showed FAK phosphorylation as the key driver of TEM mechanism (p<0.01). Concluding, our results supported by in vivo data (p<0.05) showed that TLN-1 and FAK inhibition may represent novel strategies challenging mechanisms leading to metastatic establishment. 1. Cell,2011.147(2):p.275-92; 2. Proc Natl Acad Sci USA,2015.112(1):p.214-9

Citation Format: Mara Gilardi, Simone Bersini, Rosa Maria Moresco, Marco Vanoni, Roger D. Kamm, Matteo Moretti. Engineered microfluidic 3D human microvasculature identifies Talin-1-dependent adhesion and FAK activation as the key promoter of cancer cell trans-endothelial migration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5814. doi:10.1158/1538-7445.AM2017-5814

Emerging Trends in Micro- and Nanoscale Technologies in Medicine: From Basic Discoveries to Translation

We discuss the state of the art and innovative micro- and nanoscale technologies that are finding niches and opening up new opportunities in medicine, particularly in diagnostic and therapeutic applications. We take the design of point-of-care applications and the capture of circulating tumor cells as illustrative examples of the integration of micro- and nanotechnologies into solutions of diagnostic challenges. We describe several novel nanotechnologies that enable imaging cellular structures and molecular events. In therapeutics, we describe the utilization of micro- and nanotechnologies in applications including drug delivery, tissue engineering, and pharmaceutical development/testing. In addition, we discuss relevant challenges that micro- and nanotechnologies face in achieving cost-effective and widespread clinical implementation as well as forecasted applications of micro- and nanotechnologies in medicine.

A Chemomechanical Model for Nuclear Morphology and Stresses during Cell Transendothelial Migration

It is now evident that the cell nucleus undergoes dramatic shape changes during important cellular processes such as cell transmigration through extracellular matrix and endothelium. Recent experimental data suggest that during cell transmigration the deformability of the nucleus could be a limiting factor, and the morphological and structural alterations that the nucleus encounters can perturb genomic organization that in turn influences cellular behavior. Despite its importance, a biophysical model that connects the experimentally observed nuclear morphological changes to the underlying biophysical factors during transmigration through small constrictions is still lacking. Here, we developed a universal chemomechanical model that describes nuclear strains and shapes and predicts thresholds for the rupture of the nuclear envelope and for nuclear plastic deformation during transmigration through small constrictions. The model includes actin contraction and cytosolic back pressure that squeeze the nucleus through constrictions and overcome the mechanical resistance from deformation of the nucleus and the constrictions. The nucleus is treated as an elastic shell encompassing a poroelastic material representing the nuclear envelope and inner nucleoplasm, respectively. Tuning the chemomechanical parameters of different components such as cell contractility and nuclear and matrix stiffnesses, our model predicts the lower bounds of constriction size for successful transmigration. Furthermore, treating the chromatin as a plastic material, our model faithfully reproduced the experimentally observed irreversible nuclear deformations after transmigration in lamin-A/C-deficient cells, whereas the wild-type cells show much less plastic deformation. Along with making testable predictions, which are in accord with our experiments and existing literature, our work provides a realistic framework to assess the biophysical modulators of nuclear deformation during cell transmigration.

Modeling the Blood-Brain Barrier in a 3D triple co-culture microfluidic system

The need for a blood-brain barrier (BBB) model that accurately mimics the physiological characteristics of the in-vivo situation is well-recognized by researchers in academia and industry. However, there is currently no in-vitro model allowing studies of neuronal growth and/or function influenced by factors from the blood that cross through the BBB. Therefore, we established a 3D triple co-culture microfluidic system using human umbilical vein endothelial cells (HUVEC) together with primary rat astrocytes and neurons. Immunostaining confirmed the successful triple co-culture system consisting of an intact BBB with tight intercellular junctions in the endothelial monolayer. The BBB selective permeability was determined by a fluorescent-based assay using dextrans of different molecular weights. Finally, neuron functionality was demonstrated by calcium imaging.

A 3D microfluidic model for preclinical evaluation of TCR-engineered T cells against solid tumors

The tumor microenvironment imposes physical and functional constraints on the antitumor efficacy of adoptive T cell immunotherapy. Preclinical testing of different T cell preparations can help in the selection of efficient immune therapies, but in vivo models are expensive and cumbersome to develop, while classical in vitro 2D models cannot recapitulate the spatiotemporal dynamics experienced by T cells targeting cancer. Here, we describe an easily customizable 3D model, in which the tumor microenvironment conditions are modulated and the functionality of different T cell preparations is tested. We incorporate human cancer hepatocytes as a single cell or as tumor cell aggregates in a 3D collagen gel region of a microfluidic device. Human T cells engineered to express tumor-specific T cell receptors (TCR-T cells) are then added in adjacent channels. The TCR-T cells' ability to migrate and kill the tumor target and the profile of soluble factors were investigated under conditions of varying oxygen levels and in the presence of inflammatory cytokines. We show that only the 3D model detects the effect that oxygen levels and the inflammatory environment impose on engineered TCR-T cell function, and we also used the 3D microdevice to analyze the TCR-T cell efficacy in an immunosuppressive scenario. Hence, we show that our microdevice platform enables us to decipher the factors that can alter T cell function in 3D and can serve as a preclinical assay to tailor the most efficient immunotherapy configuration for a specific therapeutic goal.

A versatile microfluidic device for high throughput production of microparticles and cell microencapsulation

Biocompatible microparticles are valuable tools in biomedical research for applications such as drug delivery, cell transplantation therapy, and analytical assays. However, their translation into clinical research and the pharmaceutical industry has been slow due to the lack of techniques that can produce microparticles with controlled physicochemical properties at high throughput. We introduce a robust microfluidic platform for the production of relatively homogeneous microdroplets at a generation frequency of up to 3.1 MHz, which is about three orders of magnitude higher than the production rate of a conventional microfluidic drop maker. We demonstrated the successful implementation of our device for production of biocompatible microparticles with various crosslinking mechanisms and cell microencapsulation with high cell viability.

Advances in on-chip vascularization

Microfluidics is invaluable for studying microvasculature, development of organ-on-chip models and engineering microtissues. Microfluidic design can cleverly control geometry, biochemical gradients and mechanical stimuli, such as shear and interstitial flow, to more closely mimic in vivo conditions. In vitro vascular networks are generated by two distinct approaches: via endothelial-lined patterned channels, or by self-assembled networks. Each system has its own benefits and is amenable to the study of angiogenesis, vasculogenesis and cancer metastasis. Various techniques are employed in order to generate rapid perfusion of these networks within a variety of tissue and organ-mimicking models, some of which have shown recent success following implantation in vivo. Combined with tuneable hydrogels, microfluidics holds great promise for drug screening as well as in the development of prevascularized tissues for regenerative medicine.

A Facile Method to Probe the Vascular Permeability of Nanoparticles in Nanomedicine Applications

The effectiveness of nanoparticles (NP) in nanomedicine depends on their ability to extravasate from vasculature towards the target tissue. This is determined by their permeability across the endothelial barrier. Unfortunately, a quantitative study of the diffusion permeability coefficients (P_d) of NPs is difficult with in vivo models. Here, we utilize a relevant model of vascular-tissue interface with tunable endothelial permeability in vitro based on microfluidics. Human umbilical vein endothelial cells (HUVECs) grown in microfluidic devices were treated with Angiopoietin 1 and cyclic adenosine monophosphate (cAMP) to vary the P_d of the HUVECs monolayer towards fluorescent polystyrene NPs (pNPs) of different sizes, which was determined from image analysis of their fluorescence intensity when diffusing across the monolayer. Using 70 kDa dextran as a probe, untreated HUVECs yielded a P_d that approximated tumor vasculature while HUVECs treated with 25 μg/mL cAMP had P_d that approximated healthy vasculature in vivo. As the size of pNPs increased, its P_d decreased in tumor vasculature, but remained largely unchanged in healthy vasculature, demonstrating a trend similar to tumor selectivity for smaller NPs. This microfluidic model of vascular-tissue interface can be used in any laboratory to perform quantitative assessment of the tumor selectivity of nanomedicine-based systems.

Identification of drugs as single agents or in combination to prevent carcinoma dissemination in a microfluidic 3D environment

Experiments were performed in a modified microfluidic platform recapitulating part of the in vivo tumor microenvironment by co-culturing carcinoma cell aggregates embedded in a three-dimensional (3D) collagen scaffold with human umbilical vein endothelial cells (HUVECs). HUVECs were seeded in one channel of the device to initiate vessel-like structures in vitro prior to introducing the aggregates. The lung adenocarcinoma cell line A549 and the bladder carcinoma cell line T24 were tested. Dose-response assays of four drugs known to interfere with Epithelial Mesenchymal Transition (EMT) signaling pathways were quantified using relative dispersion as a metric of EMT progression. The presence of HUVECs in one channel induces cell dispersal in A549 which then can be inhibited by each of the four drugs. Complete inhibition of T24 aggregate dispersal, however, is not achieved with any single agent, although partial inhibition was observed with 10 μM of the Src inhibitor, AZD-0530. Almost complete inhibition of T24 dispersal in monoculture was achieved only when the four drugs were added in combination, each at 10 μM concentration. Coculture of T24 with HUVECs forfeits the almost-complete inhibition. The enhanced dispersal observed in the presence of HUVECs is a consequence of secretion of growth factors, including HGF and FGF-2, by endothelial cells. This 3D microfluidic co-culture platform provides an in vivo-like surrogate for anti-invasive and anti-metastatic drug screening. It will be particularly useful for defining combination therapies for aggressive tumors such as invasive bladder carcinoma.

A process engineering approach to increase organoid yield

Temporal manipulation of the in vitro environment and growth factors can direct differentiation of human pluripotent stem cells into organoids - aggregates with multiple tissue-specific cell types and three-dimensional structure mimicking native organs. A mechanistic understanding of early organoid formation is essential for improving the robustness of these methods, which is necessary prior to use in drug development and regenerative medicine. We investigated intestinal organoid emergence, focusing on measurable parameters of hindgut spheroids, the intermediate step between definitive endoderm and mature organoids. We found that 13% of spheroids were pre-organoids that matured into intestinal organoids. Spheroids varied by several structural parameters: cell number, diameter and morphology. Hypothesizing that diameter and the morphological feature of an inner mass were key parameters for spheroid maturation, we sorted spheroids using an automated micropipette aspiration and release system and monitored the cultures for organoid formation. We discovered that populations of spheroids with a diameter greater than 75 μm and an inner mass are enriched 1.5- and 3.8-fold for pre-organoids, respectively, thus providing rational guidelines towards establishing a robust protocol for high quality intestinal organoids.

A 3D neurovascular microfluidic model consisting of neurons, astrocytes and cerebral endothelial cells as a blood-brain barrier

The neurovascular unit is a complex, interdependent system composed of neurons and neural supporting cells, such as astrocytes, as well as cells that comprise the vascular system including endothelial cells, pericytes, and smooth muscle cells. Each cell type in the neurovascular unit plays an essential role, either in transmitting and processing neural signals or in maintaining the appropriate microenvironmental conditions for healthy neural function. In vitro neurovascular models can be useful for understanding the different roles and functions of the cells composing the neurovascular unit, as well as for assessing the effects on neural function of therapeutic compounds after crossing the endothelial barrier. Here, we report a novel three-dimensional neurovascular microfluidic model consisting of primary rat astrocytes and neurons together with human cerebral microvascular endothelial cells. These three cell types in our neurovascular chip (NVC) show distinct cell type-specific morphological characteristics and functional properties. In particular, morphological and functional analysis of neurons enables quantitative assessment of neuronal responses, while human cerebral endothelial cells form monolayers with size-selective permeability similar to existing in vitro blood-brain barrier (BBB) models.

Abstract A49: Tumor-associated interstitial flow promotes macrophage migration and pro-metastatic M2 phenotype in 3D ECM

The growth of solid tumor is often accompanied by an increase in the flow of interstitial fluid (interstitial flow) from the center of the tumor to the surrounding stroma. Recent studies have shown that elevated interstitial flow can influence the migration of cancer cells and fibroblasts. Despite these findings, the effects of interstitial flow on macrophages, one of the key metastasis-promoting tumor-associated stromal cell types, have not been explored. We used microfluidic and transwell flow assays to investigate how high level of interstitial flow (~3 μm/s) often observed in tumor affect macrophage migration and protein expression. We found that interstitial flow not only enhanced macrophage migration speed, but also directed macrophages to migrate against the flow in 3D extracellular matrix. Moreover, we discovered that interstitial flow activated Akt and FAK, two kinases that are crucial for cell migration. Interestingly, interstitial flow also up-regulated macrophage expression of M2 markers Arg I and TGFβ through the activation of JAK1-STAT3/6 pathway. Finally, macrophages treated with interstitial flow were shown to have enhanced abilities to promote cancer cell migration and protrusion formation. Taken together, these results suggest that interstitial flow can promote metastasis through its effects on macrophages. Specifically, since macrophages migrate against the flow, interstitial flow, which emanates from the tumor, can act as a mechanical stimulus to recruit macrophages into tumor tissues. Moreover, interstitial flow can activate macrophages and polarize them toward pro-metastatic M2 phenotype to further promote tumor metastasis and immunosuppression.

Citation Format: Ran Li, Hao Xing, Tara A. Lee, Hesham Azizgolshani, Roger D. Kamm. Tumor-associated interstitial flow promotes macrophage migration and pro-metastatic M2 phenotype in 3D ECM. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr A49.

Morphological Transformation and Force Generation of Active Cytoskeletal Networks

Cells assemble numerous types of actomyosin bundles that generate contractile forces for biological processes, such as cytokinesis and cell migration. One example of contractile bundles is a transverse arc that forms via actomyosin-driven condensation of actin filaments in the lamellipodia of migrating cells and exerts significant forces on the surrounding environments. Structural reorganization of a network into a bundle facilitated by actomyosin contractility is a physiologically relevant and biophysically interesting process. Nevertheless, it remains elusive how actin filaments are reoriented, buckled, and bundled as well as undergo tension buildup during the structural reorganization. In this study, using an agent-based computational model, we demonstrated how the interplay between the density of myosin motors and cross-linking proteins and the rigidity, initial orientation, and turnover of actin filaments regulates the morphological transformation of a cross-linked actomyosin network into a bundle and the buildup of tension occurring during the transformation.

Macrophage-Secreted TNFα and TGFβ1 Influence Migration Speed and Persistence of Cancer Cells in 3D Tissue Culture via Independent Pathways

The ability of a cancer cell to migrate through the dense extracellular matrix within and surrounding the solid tumor is a critical determinant of metastasis. Macrophages enhance invasion and metastasis in the tumor microenvironment, but the basis for their effects is not fully understood. Using a microfluidic 3D cell migration assay, we found that the presence of macrophages enhanced the speed and persistence of cancer cell migration through a 3D extracellular matrix in a matrix metalloproteinases (MMP)-dependent fashion. Mechanistic investigations revealed that macrophage-released TNFα and TGFβ1 mediated the observed behaviors by two distinct pathways. These factors synergistically enhanced migration persistence through a synergistic induction of NF-κB-dependent MMP1 expression in cancer cells. In contrast, macrophage-released TGFβ1 enhanced migration speed primarily by inducing MT1-MMP expression. Taken together, our results reveal new insights into how macrophages enhance cancer cell metastasis, and they identify TNFα and TGFβ1 dual blockade as an antimetastatic strategy in solid tumors. Cancer Res; 77(2); 279-90. ©2016 AACR.

Abstract A126: The role of macrophages and monocytes during cancer cell extravasation in 3D vascularized microfluidic models

Recent in vivo mouse studies have revealed that macrophages can promote metastasis, while certain subsets of monocytes either help or block metastasis. Further studies are warranted to understand the underlying mechanisms, so as to target pharmacologically these immune cells as a means to halt metastasis. Intravital imaging can be performed in mice and has proven extremely useful in uncovering the role of macrophage and monocytes in metastasis, but requires specialized expertise and equipment. Concurrently, microfluidic models have been developed to dissect certain steps of the metastatic spread, because they allow for easier imaging at high resolution and facilitate an improved microenvironment control over more traditional macro-scale in vitro systems.

In this study, a microfluidic model was used to investigate the effects of monocytes and macrophages on cancer cell extravasation. A previously developed microfluidic assay was used to form a 3D microvascular network (MVN) that consists of 3 separate compartments, flanked by media channels connected to reservoirs. In the two lateral compartments, normal human lung fibroblasts were seeded at 5 million/ml, while in the central compartment GFP HUVECs were placed at 4 million/ml all in a 3D fibrin gel. After 4 days, the HUVECs self-assemble into a MVN, which forms lumens that open directly to the media channel. Therefore, cancer cells can be perfused within the MVN via the reservoirs, and their transendothelial migration is tracked by confocal imaging over time for up to 12 hours. In this study, we mix the HUVECs with the macrophages (ratio 40:1) such that the macrophages are found in the fibrin on the outside of the vessels. Alternatively, we perfuse monocytes in the MVN, most of which have extravasated 4 days later (94±2%), thus replicating macrophage differentiation from recruited monocytes. In another study, monocytes were perfused with cancer cells in the MVN to test whether the monocytes could affect cancer cell extravasation intra-luminally, as they would in the blood circulation. Both monocytes and macrophages were derived from healthy donors' blood.

Monocyte-derived macrophages (MDMs) were on average 33.4±4.4 μm (mean±SEM) away from the MVN, of which 40% were found within 10 μm. Interestingly, 46.4±3.1% stained positive for MRC-1. The MDM:MDA-MB-231 ratio was 2±0.5. The presence of MDM around the microvascular networks did not affect cancer cell extravasation rate; 10 hours after the cancer cells were perfused within the MVN, 57±15 vs. 60±6% of MDA-MB-231 had extravasated with or without MDMs, respectively. 11±6% of MDA-MB-231s came in contact with MDMs, for 5.1±0.6 hrs. Contact was mostly established after cancer cells had extravasated (73±19% of cancer cells), and less often while the cancer cell was extravasating (15±9%) or inside the vessels (12±12%). At t = 0, the average shortest distance between a MDM and a cancer cell arrested within the vessels was 98.4±6.3 μm, and was the same for cancer cells that did or did not eventually extravasate. However, the cancer cells that extravasated migrated further away from the μVN surface in presence of MDMs; 4.5 hrs after extravasation, cells were found 16.5±4.9 vs. 5.4±2.1 μm away from the endothelial wall with or without MDMs, respectively (p = 0.044, unpaired student t-test). In a separate study, monocytes were found to significantly decrease cancer cell extravasation. 11 hrs after cancer cells were perfused with monocytes inside the MVN, 19.8±6.1% of MDA-MB-231 had extravasated vs. 53.5±11% when cancer cells were perfused alone (p = 0.041, unpaired t-test). In conclusion, monocytes but not macrophage seem to affect cancer cell extravasation. Further studies will generalize the results to other cancer cell lines, and investigate how monocytes might decrease extravasation, and how this effect could be exacerbated pharmacologically to decrease metastasis.

Citation Format: Alexandra Boussommier-Calleja, Roger D. Kamm. The role of macrophages and monocytes during cancer cell extravasation in 3D vascularized microfluidic models [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A126.