Naive primary neutrophils play a dual role in the tumor microenvironment

The tumor microenvironment (TME) is characterized by a network of cancer cells, recruited immune cells and extracellular matrix (ECM) in a hypoxic microenvironment. However, the specific role of neutrophils during tumor development, and their interactions with other immune cells is still not well understood. Thus, there is a need to investigate the interaction between primary neutrophils and natural killer cells and the resulting effects on tumor development. Here we use both standard well plate culture and an under oil microfluidic (UOM) assay with an integrated extracellular cell matrix (ECM) bridge to elucidate how naive primary neutrophils respond to both patient derived tumor cells and tumor cell lines. Our data demonstrated that both patient derived head and neck squamous cell carcinoma (HNSCC) tumor cells and MDA-MB-231 breast cancer cells trigger cluster formation in neutrophils, and the swarm of neutrophils restricts tumor invasion through the generation of reactive oxygen species (ROS) and neutrophil extracellular trap (NETs) release within the neutrophil cluster. However, we also observed that the presence of neutrophils downregulates granzyme B in NK-92 cells and the resulting NETs can obstruct NK cells from penetrating the tumor mass in vitro suggesting a dual role for neutrophils in the TME. Further, using label-free optical metabolic imaging (OMI) we observed changes in the metabolic activities of primary neutrophils during the different swarming phases when challenged with tumor cells. Finally, our data demonstrates that neutrophils in direct contact, or in close proximity, with tumor cells exhibit greater metabolic activities (lower nicotinamide adenine dinucleotide phosphate (NAD(P)H) mean lifetime) compared to non-contact neutrophils.

Microphysiological systems for solid tumor immunotherapy: opportunities and challenges

Immunotherapy remains more effective for hematologic tumors than for solid tumors. One of the main challenges to immunotherapy of solid tumors is the immunosuppressive microenvironment these tumors generate, which limits the cytotoxic capabilities of immune effector cells (e.g., cytotoxic T and natural killer cells). This microenvironment is characterized by hypoxia, nutrient starvation, accumulated waste products, and acidic pH. Tumor-hijacked cells, such as fibroblasts, macrophages, and T regulatory cells, also contribute to this inhospitable microenvironment for immune cells by secreting immunosuppressive cytokines that suppress the antitumor immune response and lead to immune evasion. Thus, there is a strong interest in developing new drugs and cell formulations that modulate the tumor microenvironment and reduce tumor cell immune evasion. Microphysiological systems (MPSs) are versatile tools that may accelerate the development and evaluation of these therapies, although specific examples showcasing the potential of MPSs remain rare. Advances in microtechnologies have led to the development of sophisticated microfluidic devices used to recapitulate tumor complexity. The resulting models, also known as microphysiological systems (MPSs), are versatile tools with which to decipher the molecular mechanisms driving immune cell antitumor cytotoxicity, immune cell exhaustion, and immune cell exclusion and to evaluate new targeted immunotherapies. Here, we review existing microphysiological platforms to study immuno-oncological applications and discuss challenges and opportunities in the field.

Microphysiological model reveals the promise of memory-like natural killer cell immunotherapy for HIV± cancer

Numerous studies are exploring the use of cell adoptive therapies to treat hematological malignancies as well as solid tumors. However, there are numerous factors that dampen the immune response, including viruses like human immunodeficiency virus. In this study, we leverage human-derived microphysiological models to reverse-engineer the HIV-immune system interaction and evaluate the potential of memory-like natural killer cells for HIV+ head and neck cancer, one of the most common tumors in patients living with human immunodeficiency virus. Here, we evaluate multiple aspects of the memory-like natural killer cell response in human-derived bioengineered environments, including immune cell extravasation, tumor penetration, tumor killing, T cell dependence, virus suppression, and compatibility with retroviral medication. Overall, these results suggest that memory-like natural killer cells are capable of operating without T cell assistance and could simultaneously destroy head and neck cancer cells as well as reduce viral latency.

Microfluidic device with reconfigurable spatial temporal gradients reveals plastic astrocyte response to stroke and reperfusion

As a leading cause of mortality and morbidity, stroke constitutes a significant global health burden. Ischemic stroke accounts for 80% of cases and occurs due to an arterial thrombus, which impedes cerebral blood flow and rapidly leads to cell death. As the most abundant cell type within the central nervous system, astrocytes play a critical role within the injured brain. We developed a novel microphysiological platform that permits the induction of spatiotemporally controlled nutrient gradients, allowing us to study astrocytic response during and after transient nutrient deprivation. Within 24 h of inducing starvation in the platform, nutrient deprivation led to multiple changes in astrocyte response, from metabolic perturbations to gene expression changes, and cell viability. Furthermore, we observed that nutrient restoration did not reverse the functional changes in astrocyte metabolism, which mirrors reperfusion injury observed in vivo. We also identified alterations in numerous glucose metabolism-associated genes, many of which remained upregulated or downregulated even after restoration of the nutrient supply. Together, these findings suggest that astrocyte activation during and after nutrient starvation induces plastic changes that may underpin persistent stroke-induced functional impairment. Overall, our innovative device presents interesting potential to be used in the development of new therapies to improve tissue repair and even cognitive recovery after stroke.

Griddient: a microfluidic array to generate reconfigurable gradients on-demand for spatial biology applications

Biological tissues are highly organized structures where spatial-temporal gradients (e.g., nutrients, hypoxia, cytokines) modulate multiple physiological and pathological processes including inflammation, tissue regeneration, embryogenesis, and cancer progression. Current in vitro technologies struggle to capture the complexity of these transient microenvironmental gradients, do not provide dynamic control over the gradient profile, are complex and poorly suited for high throughput applications. Therefore, we have designed Griddent, a user-friendly platform with the capability of generating controllable and reversible gradients in a 3D microenvironment. Our platform consists of an array of 32 microfluidic chambers connected to a 384 well-array through a diffusion port at the bottom of each reservoir well. The diffusion ports are optimized to ensure gradient stability and facilitate manual micropipette loading. This platform is compatible with molecular and functional spatial biology as well as optical and fluorescence microscopy. In this work, we have used this platform to study cancer progression.

Oxidative phosphorylation inhibitors inhibit proliferation of endometriosis cells

In brief

Developing novel therapies to cure and manage endometriosis is a major unmet need that will benefit over 180 million women worldwide. Results from the current study suggest that inhibitors of oxidative phosphorylation may serve as novel agents for the treatment of endometriosis.

Abstract

Current therapeutic strategies for endometriosis focus on symptom management and are not curative. Here, we provide evidence supporting the inhibition of oxidative phosphorylation (OXPHOS) as a novel treatment strategy for endometriosis. Additionally, we report an organotypic organ-on-a-chip luminal model for endometriosis. The OXPHOS inhibitors, curcumin, plumbagin, and the FDA-approved anti-malarial agent, atovaquone, were tested against the endometriosis cell line, 12Z, in conventional as well as the new organotypic model. The results suggest that all three compounds inhibit proliferation and cause cell death of the endometriotic cells by inhibiting OXPHOS and causing an increase in intracellular oxygen radicals. The oxidative stress mediated by curcumin, plumbagin, and atovaquone causes DNA double-strand breaks as indicated by the elevation of phospho-γH2Ax. Mitochondrial energetics shows a significant decrease in oxygen consumption in 12Z cells. These experiments also highlight differences in the mechanism of action as curcumin and plumbagin inhibit complex I whereas atovaquone blocks complexes I, II, and III. Real-time assessment of cells in the lumen model showed inhibition of migration in response to the test compounds. Additionally, using two-photon lifetime imaging, we demonstrate that the 12Z cells in the lumen show decreased redox ratio (NAD(P)H/FAD) and lower fluorescence lifetime of NAD(P)H in the treated cells confirming major metabolic changes in response to inhibition of mitochondrial electron transport. The robust chemotoxic responses observed with atovaquone suggest that this anti-malarial agent may be repurposed for the effective treatment of endometriosis.

Towards Novel Biomimetic In Vitro Models of the Blood-Brain Barrier for Drug Permeability Evaluation

Current available animal and in vitro cell-based models for studying brain-related pathologies and drug evaluation face several limitations since they are unable to reproduce the unique architecture and physiology of the human blood-brain barrier. Because of that, promising preclinical drug candidates often fail in clinical trials due to their inability to penetrate the blood-brain barrier (BBB). Therefore, novel models that allow us to successfully predict drug permeability through the BBB would accelerate the implementation of much-needed therapies for glioblastoma, Alzheimer's disease, and further disorders. In line with this, organ-on-chip models of the BBB are an interesting alternative to traditional models. These microfluidic models provide the necessary support to recreate the architecture of the BBB and mimic the fluidic conditions of the cerebral microvasculature. Herein, the most recent advances in organ-on-chip models for the BBB are reviewed, focusing on their potential to provide robust and reliable data regarding drug candidate ability to reach the brain parenchyma. We point out recent achievements and challenges to overcome in order to advance in more biomimetic in vitro experimental models based on OOO technology. The minimum requirements that should be met to be considered biomimetic (cellular types, fluid flow, and tissular architecture), and consequently, a solid alternative to in vitro traditional models or animals.

Abstract B01: Microphysiological systems as a next-generation precision immunotherapy tool: From patient heterogeneity to memory-like natural killer cells

Immunotherapy is transforming cancer treatment for thousands of patients worldwide. However, treatment response relies on the patients’ immune system, eliciting heterogeneous results. Numerous parameters contribute to immunotherapy response, including tumor-intrinsic factors such as an immunosuppressive microenvironment characterized by nutrient depletion, acidic pH, or waste products; and tumor-extrinsic factors including genetic immunodeficiencies, or immunosuppressive disorders like HIV infection or organ transplant medication. Consequently, predicting response to immunotherapy remains challenging. Thus, we designed a microphysiological system (MPS) that allows us to incorporate these factors to evaluate patient-specific immunotherapy efficacy. We used our MPS to assess memory-like natural killer (mNK) cell efficacy against solid tumors, as well as evaluated NK cell exhaustion in a tumor-induced suppressive environment. Focusing upon head and neck squamous cell carcinoma (HNSCC), we evaluated risk/benefit ratios and mNK cell responses, including mNK cell extravasation; tumor penetration/killing; and synergy with therapeutic antibodies. We observed that the tumor-induced microenvironment led to gradual erosion of natural killer (NK) cells’ cytotoxicity and upregulation of exhaustion markers. Interestingly, NK cells exhibited a limited capacity to recover from tumor-induced exhaustion, and checkpoint inhibitors and immunomodulatory agents (e.g., PD-1, IDO-1 inhibitors) partially prevented NK cell exhaustion. We also infected T cells with HIV to evaluate whether immunocompromised patients would benefit from mNK cell therapy in the same fashion. In this context, mNK cells exhibited promising immunotherapeutic potential for these populations as they retained tumor killing capacity even in the absence of T cells; mNK cells exhibited extravasation and migration towards patient-derived tumor spheroids, suggesting that mNK cells alone are capable of extravasation. However, CD4 T cells enhanced mNK responses and elicited overexpression of NK survival and function-associated genes, suggesting that future guidelines for people living with HIV and cancer should consider the progression of the disease when considering mNK cell-based therapies. Our MPS may also help to identify CD4 T cell-secreted factors with therapeutic potential to increase mNK cell responses, which could be provided ex vivo in immunocompromised patients. In summary, MPSs offer a precision tool to assess treatment responses in a patient-specific fashion and may help identify next-generation immunotherapies for hitherto excluded cohorts.

Citation Format: Catherine A McBain, Mehtab A Farooqui, María Virumbrales-Muñoz, Cristina Sanchez-de-Diego, Sireesh Kumar Teertam, Rebecca Schmitz, Melissa Skala, David J Beebe, Jose M Ayuso. Microphysiological systems as a next-generation precision immunotherapy tool: From patient heterogeneity to memory-like natural killer cells [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr B01.

Microfluidic Model to Evaluate Astrocyte Activation in Penumbral Region following Ischemic Stroke

Stroke is one of the main causes of death in the US and post-stroke treatment options remain limited. Ischemic stroke is caused by a blood clot that compromises blood supply to the brain, rapidly leading to tissue death at the core of the infarcted area surrounded by a hypoxic and nutrient-starved region known as the penumbra. Recent evidence suggests that astrocytes in the penumbral region play a dual role in stroke response, promoting further neural and tissue damage or improving tissue repair depending on the microenvironment. Thus, astrocyte response in the hypoxic penumbra could promote tissue repair after stroke, salvaging neurons in the affected area and contributing to cognitive recovery. However, the complex microenvironment of ischemic stroke, characterized by gradients of hypoxia and nutrients, poses a unique challenge for traditional in vitro models, which in turn hinders the development of novel therapies. To address this challenge, we have developed a novel, polystyrene-based microfluidic device to model the necrotic and penumbral region induced by an ischemic stroke. We demonstrated that when subjected to hypoxia, and nutrient starvation, astrocytes within the penumbral region generated in the microdevice exhibited long-lasting, significantly altered signaling capacity including calcium signaling impairment.

Innate immune cell response to host-parasite interaction in a human intestinal tissue microphysiological system

Protozoan parasites that infect humans are widespread and lead to varied clinical manifestations, including life-threatening illnesses in immunocompromised individuals. Animal models have provided insight into innate immunity against parasitic infections; however, species-specific differences and complexity of innate immune responses make translation to humans challenging. Thus, there is a need for in vitro systems that can elucidate mechanisms of immune control and parasite dissemination. We have developed a human microphysiological system of intestinal tissue to evaluate parasite-immune-specific interactions during infection, which integrates primary intestinal epithelial cells and immune cells to investigate the role of innate immune cells during epithelial infection by the protozoan parasite, Toxoplasma gondii, which affects billions of people worldwide. Our data indicate that epithelial infection by parasites stimulates a broad range of effector functions in neutrophils and natural killer cell-mediated cytokine production that play immunomodulatory roles, demonstrating the potential of our system for advancing the study of human-parasite interactions.

Microphysiological model of the renal cell carcinoma to inform anti-angiogenic therapy

Renal cell carcinomas are common genitourinary tumors characterized by high vascularization and strong reliance on glycolysis. Despite the many available therapies for renal cell carcinomas, first-line targeted therapies, such as cabozantinib, and durable reaponses are seen in only a small percentage of patients. Yet, little is known about the mechanisms that drive response (or lack thereof). This dearth of knowledge can be explained by the dynamic and complex microenvironment of renal carcinoma, which remains challenging to recapitulate in vitro. Here, we present a microphysiological model of renal cell carcinoma, including a tubular blood vessel model of induced pluripotent stem cell-derived endothelial cells and an adjacent 3D carcinoma model. Our model recapitulated hypoxia, glycolic metabolism, and sprouting angiogenesis. Using our model, we showed that cabozantinib altered cancer cell metabolism and decreased sprouting angiogenesis but did not restore barrier function. This microphysiological model could be helpful to elucidate, through multiple endpoints, the contributions of the relevant environmental components in eliciting a functional response or resistance to therapy in renal cell carcinoma.

Role of the Skin Microenvironment in Melanomagenesis: Epidermal Keratinocytes and Dermal Fibroblasts Promote BRAF Oncogene-Induced Senescence Escape in Melanocytes

Simple Summary

Melanoma is a deadly skin cancer caused by the uncontrolled proliferation of melanocytes, a population of specialized cells that produce the skin pigment melanin. An aberrant proliferation of melanocytes is common, manifesting as new moles, and these lesions often remain benign. Only a small fraction of these aberrant melanocytes transition to melanoma (i.e., melanomagenesis). The factors that drive this transition are not fully understood. Recent studies have suggested that other cells—specifically, keratinocytes that make up the upper skin layers and fibroblasts, which are non-specialized cells within the deeper layers of the skin—also contribute to melanomagenesis. Here, employing microscale models that mimicked the skin microenvironment, we investigated the effect of crosstalk between melanocytes as well as keratinocytes and fibroblasts on melanomagenesis. Our findings show that keratinocyte- and fibroblast-derived factors can inhibit the mechanisms that prevent an uncontrolled melanocyte proliferation and contribute to melanomagenesis. Thus, targeting skin microenvironment-derived factors is a potential strategy to prevent melanomagenesis.

Abstract

BRAF^V600E is the most common mutation driver in melanoma. This mutation is known to cause a brief burst of proliferation followed by growth arrest and senescence, which prevent an uncontrolled cell proliferation. This phenomenon is known as oncogene-induced senescence (OIS) and OIS escape is thought to lead to melanomagenesis. Much attention has been focused on the melanocyte-intrinsic mechanisms that contribute to senescence escape. Additional genetic events such as the loss of tumor suppressor PTEN and/or epigenetic changes that contribute to senescence escape have been described. However, the role of the skin microenvironment—specifically, the role of epidermal keratinocytes—on melanomagenesis is not fully understood. In this study, we employ a microfluidic platform to study the interaction between melanocytes expressing the BRAF^V600E mutation as well as keratinocytes and dermal fibroblasts. We demonstrate that keratinocytes suppress senescence-related genes and promote the proliferation of transformed melanocytes. We also show that a keratinocyte-conditioned medium can alter the secretion of both pro- and anti-tumorigenic factors by transformed melanocytes. In addition, we show that melanocytes and keratinocytes from donors of white European and black African ancestry display different crosstalks; i.e., white keratinocytes appear to promote a more pro-tumorigenic phenotype compared with black keratinocytes. These data suggest that keratinocytes exert their influence on melanomagenesis both by suppressing senescence-related genes in melanocytes and by affecting the balance of the melanocyte-secreted factors that favor tumorigenesis.

Microfluidic Systems to Study Neutrophil Forward and Reverse Migration

During infection, neutrophils are the most abundantly recruited innate immune cells at sites of infection, playing critical roles in the elimination of local infection and healing of the injury. Neutrophils are considered to be short-lived effector cells that undergo cell death at infection sites and in damaged tissues. However, recent in vitro and in vivo evidence suggests that neutrophil behavior is more complex and that they can migrate away from the inflammatory site back into the vasculature following the resolution of inflammation. Microfluidic devices have contributed to an improved understanding of the interaction and behavior of neutrophils ex vivo in 2D and 3D microenvironments. The role of reverse migration and its contribution to the resolution of inflammation remains unclear. In this review, we will provide a summary of the current applications of microfluidic devices to investigate neutrophil behavior and interactions with other immune cells with a focus on forward and reverse migration in neutrophils.

Social motility of biofilm-like microcolonies in a gliding bacterium

Bacterial biofilms are aggregates of surface-associated cells embedded in an extracellular polysaccharide (EPS) matrix, and are typically stationary. Studies of bacterial collective movement have largely focused on swarming motility mediated by flagella or pili, in the absence of a biofilm. Here, we describe a unique mode of collective movement by a self-propelled, surface-associated biofilm-like multicellular structure. Flavobacterium johnsoniae cells, which move by gliding motility, self-assemble into spherical microcolonies with EPS cores when observed by an under-oil open microfluidic system. Small microcolonies merge, creating larger ones. Microscopic analysis and computer simulation indicate that microcolonies move by cells at the base of the structure, attached to the surface by one pole of the cell. Biochemical and mutant analyses show that an active process drives microcolony self-assembly and motility, which depend on the bacterial gliding apparatus. We hypothesize that this mode of collective bacterial movement on solid surfaces may play potential roles in biofilm dynamics, bacterial cargo transport, or microbial adaptation. However, whether this collective motility occurs on plant roots or soil particles, the native environment for F. johnsoniae, is unknown.

Bacterial biofilms are aggregates of surface-associated cells embedded in an extracellular polysaccharide (EPS) matrix. Here, the authors describe a unique mode of collective movement by self-propelled, surface-associated spherical microcolonies with EPS cores in the gliding bacterium Flavobacterium johnsoniae.

Microfluidic model with air-walls reveals fibroblasts and keratinocytes modulate melanoma cell phenotype, migration, and metabolism

Melanoma evolution is a complex process. The role epidermal keratinocytes and dermal fibroblasts play in this process and the mechanisms involved in tumor-stroma interactions remain poorly understood. Here, we used a microfluidic platform to evaluate the cross-talk between human primary melanoma cells, keratinocytes and dermal fibroblasts. The microfluidic device included multiple circular chambers separated by a series of narrow connection channels. The microdevice design allowed us to develop a new cell patterning method based on air-walls, removing the need for hydrogel barriers, porous membranes, or external equipment. Using this method, we co-cultured melanoma cells in the presence of keratinocytes and/or dermal fibroblasts. The results demonstrated that the presence of dermal fibroblasts and keratinocytes led to changes in melanoma cell morphology and growth pattern. Molecular analysis revealed changes in the chemokine secretion pattern, identifying multiple secreted factors involved in tumor progression. Finally, optical metabolic imaging showed that melanoma cells, fibroblasts, and keratinocytes exhibited different metabolic features. Additionally, the presence of stromal cells led to a metabolic shift in melanoma cells, highlighting the role the skin microenvironment on melanoma evolution.

Abstract PO004: Reverse-engineering the tumor microenvironment through microfluidics and bioengineered in vitro models

Scope: Solid tumors are complex 3D systems where environmental gradients and cellular interactions shape tumor evolution and patient outcome. In this work, we developed bioengineered microfluidic in vitro models to study how environmental factors affect immune exhaustion.

Methods: In this work, we fabricated a microfluidic model that mimicked the tumor architecture to study tumor-immune interactions. Breast cancer cells were cultured as a dense mass and embedded in a 3D collagen hydrogel inside the microfluidic device. The model also included two lateral lumens on the flanks, allowing us to seed endothelial cells and mimicking the cylindrical structure of blood vessels. These biomimetic blood vessels were used to perfuse culture media, antibodies (e.g., anti-PD-1, immunocytokines), or immune cells (e.g., natural killer cells, CD4 T cells). We used a combination of fluorescence and multi-photon microscopy to monitor antibody and immune cell extravasation, migration, and tumor clearance in real-time. We retrieved the cells from the model (i.e., endothelial, tumor, CD4, and natural killer cells) to analyze them by RT-qPCR and functional assays (e.g., proliferation rate, migration speed, natural killer cell killing potential).

Results: The results demonstrated that tumor metabolism rapidly led to nutrient starvation and acidic pH in the inner regions of the model. Consequently, tumor cells showed different metabolism and proliferation rates near the biomimetic vessels compared with the core of the model. We used metabolic inhibitors targeting multiple metabolic pathways (e.g., glycolysis) to selectively destroy tumor cells depending on their location in the model. Real-time microscopy revealed that natural killer cells were able to detect the presence of tumor cells from several hundreds of microns away, exhibiting directional migration towards the tumor cells. Molecular analysis revealed that as natural killer cells reached inner regions, they exhibited progressive signs of immune exhaustion (e.g., upregulation of PD-1, downregulation of granzymes). Interestingly, when retrieved from the model and cultured alone in traditional flasks, natural killer cells remained exhausted for an extended time, highlighting the long-lasting effects of the tumor microenvironment. The use of antibodies (e.g., anti-PD-1), immunocytokines (e.g., IL-2-coupled antibody), or metabolic inhibitors (e.g., IDO-1 inhibitors) partially prevented natural killer cell exhaustion at the core, improving their killing potential.

Conclusions: tumor-immune interactions in the tumor microenvironment are extremely complex. Bioengineered microfluidic models offered a versatile tool to monitor the natural killer cell exhaustion, allowing us to identify multiple molecular factors driving the process. We used this knowledge to test several drugs and antibodies to prevent natural killer cell exhaustion and improve tumor killing.

Citation Format: Jose M. Ayuso, Mehtab Farooqui, Maria Virumbrales-Munoz, Shujah Rehman, Melissa C. Skala, David J. Beebe. Reverse-engineering the tumor microenvironment through microfluidics and bioengineered in vitro models [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr PO004.

Breast cancer immunotherapy: current biomarkers and the potential of in vitro assays

Breakthroughs in metastatic breast cancer care require new model systems that can identify the unique features and vulnerabilities of each cancer. Primary tumor cultures are proposed to efficiently screen multiple treatment options in a patient-specific strategy to maximize therapeutic benefit, minimize toxicity, and enable mechanistic insights that inspire future biomarkers for patient selection. To realize the potential of patient-specific cultures, new tools are needed to capture cell-by-cell variability in behavior and dynamic response to treatments in living 3D specimens. Potential bioengineering tools that can achieve this include optical microscopy to image single-cell dynamics and microphysiological in vitro systems to evaluate cell-cell interactions and immunotherapies.

Elucidating cancer-vascular paracrine signaling using a human organotypic breast cancer cell extravasation model

In cancer metastasis, extravasation refers to the process where tumor cells exit the bloodstream by crossing the endothelium and invade the surrounding tissue. Tumor cells engage in complex crosstalk with other active players such as the endothelium leading to changes in functional behavior that exert pro-extravasation effects. Most in vitro studies to date have only focused on the independent effects of molecular targets on the functional changes of cancer cell extravasation behavior. However, singular targets cannot combat complex interactions involved in tumor cell extravasation that affects multiple cell types and signaling pathways. In this study, we employ an organotypic microfluidic model of human vasculature to investigate the independent and combined role of multiple upregulated secreted factors resulting from cancer-vascular interactions during cancer cell extravasation. The device consists of a tubular endothelial vessel generated from induced pluripotent stem cell derived endothelial cells within a collagen-fibrinogen matrix with breast cancer cells injected through and cultured along the lumen of the vessel. Our system identified cancer-vascular crosstalk, involving invasive breast cancer cells, that results in increased levels of secreted IL-6, IL-8, and MMP-3. Our model also showed that upregulation of these secreted factors correlates with invasive/metastatic potential of breast cancer cells. We also used therapeutic inhibitors to assess the independent and combined role of multiple signaling factors on the overall changes in functional behavior of both the cancer cells and the endothelium that promote extravasation. Taken together, these results demonstrate the potential of our organotypic model in elucidating mechanisms through which cancer-vascular interactions can promote extravasation, and in conducting functional assessment of therapeutic drugs that prevent extravasation in cancer metastasis.

Microfluidic tumor-on-a-chip model to evaluate the role of tumor environmental stress on NK cell exhaustion

Solid tumors generate a suppressive environment that imposes an overwhelming burden on the immune system. Nutrient depletion, waste product accumulation, hypoxia, and pH acidification severely compromise the capacity of effector immune cells such as T and natural killer (NK) cells to destroy cancer cells. However, the specific molecular mechanisms driving immune suppression, as well as the capacity of immune cells to adapt to the suppressive environment, are not completely understood. Thus, here, we used an in vitro microfluidic tumor-on-a-chip platform to evaluate how NK cells respond to the tumor-induced suppressive environment. The results demonstrated that the suppressive environment created by the tumor gradually eroded NK cell cytotoxic capacity, leading to compromised NK cell surveillance and tumor tolerance. Further, NK cell exhaustion persisted for an extended period of time after removing NK cells from the microfluidic platform. Last, the addition of checkpoint inhibitors and immunomodulatory agents alleviated NK cell exhaustion.

Toward improved in vitro models of human cancer

Cancer is a leading cause of death across the world and continues to increase in incidence. Despite years of research, multiple tumors (e.g., glioblastoma, pancreatic cancer) still have limited treatment options in the clinic. Additionally, the attrition rate and cost of drug development have continued to increase. This trend is partly explained by the poor predictive power of traditional in vitro tools and animal models. Moreover, multiple studies have highlighted that cell culture in traditional Petri dishes commonly fail to predict drug sensitivity. Conversely, animal models present differences in tumor biology compared with human pathologies, explaining why promising therapies tested in animal models often fail when tested in humans. The surging complexity of patient management with the advent of cancer vaccines, immunotherapy, and precision medicine demands more robust and patient-specific tools to better inform our understanding and treatment of human cancer. Advances in stem cell biology, microfluidics, and cell culture have led to the development of sophisticated bioengineered microscale organotypic models (BMOMs) that could fill this gap. In this Perspective, we discuss the advantages and limitations of patient-specific BMOMs to improve our understanding of cancer and how these tools can help to confer insight into predicting patient response to therapy.

Microfluidic Tumor-on-a-Chip Model to Study Tumor Metabolic Vulnerability

Tumor-specific metabolic adaptations offer an interesting therapeutic opportunity to selectively destroy cancer cells. However, solid tumors also present gradients of nutrients and waste products across the tumor mass, forcing tumor cells to adapt their metabolism depending on nutrient availability in the surrounding microenvironment. Thus, solid tumors display a heterogenous metabolic phenotype across the tumor mass, which complicates the design of effective therapies that target all the tumor populations present. In this work, we used a microfluidic device to study tumor metabolic vulnerability to several metabolic inhibitors. The microdevice included a central chamber to culture tumor cells in a three-dimensional (3D) matrix, and a lumen in one of the chamber flanks. This design created an asymmetric nutrient distribution across the central chamber, generating gradients of cell viability. The results revealed that tumor cells located in a nutrient-enriched environment showed low to no sensitivity to metabolic inhibitors targeting glycolysis, fatty acid oxidation, or oxidative phosphorylation. Conversely, when cell density inside of the model was increased, compromising nutrient supply, the addition of these metabolic inhibitors disrupted cellular redox balance and led to tumor cell death.

Abstract 3874: Monitoring immune-tumor cell interactions in 3D microfluidic models with optical metabolic imaging and molecular profiling

The tumor microenvironment is defined by nutrient starvation, waste product accumulation, hypoxia, and acidosis, which collectively contribute towards immune exhaustion and suppression. Models that mimic the tumor microenvironment will be instrumental to develop new therapies that improve immune response. Microfluidic models can mimic the tumor metabolic microenvironment to elucidate mechanisms that lead to weakened tumor immunity and to new tumor immunotherapies. We developed microfluidic models where cancer cells were cultured as a dense mass embedded in a 3D matrix. The microfluidic platform has lateral channels that are lined with endothelial cells to mimic the tumor vasculature. These vessels can be perfused with immune cells or drugs that extravasate into the tumor mass. Immune cells were isolated from the tumor mass within these microfluidic models and gene expression was analyzed to quantify changes in immune cell function under tumor metabolic microenvironment conditions. Optical metabolic imaging of NADH and FAD autofluorescence with 2-photon microscopy monitored metabolic dynamics during tumor-immune cell interactions. Immunotherapy drugs were also perfused through the microfluidic devices to measure drug efficacy. Changes in immune cell function after drug exposure were analyzed by optical metabolic imaging to examine metabolic dynamics, alongside fluorescence microscopy to visualize cytotoxicity changes. Natural killer cells exhibited directional migration towards the tumor, which indicates that natural killer cells can detect the presence of the tumor several hundreds of microns away. Real-time microscopy revealed that natural killer cells destroyed tumor cells at the tumor periphery and notably at the innermost tumor core. Gene expression analysis of immune cells and tumor cells cultured in the microfluidic model reveals that the tumor cells have created an environment consistent with immunosuppression, immune exhaustion, and nutrient starvation. Metabolic imaging reveals that immune cells exposed to the tumor microenvironment have an altered metabolic profile, specifically decreased redox ratio that persists even under normal culture conditions. The microfluidic model provides a system to examine immune cytotoxicity, metabolic dynamics during tumor-immune interactions, and the impact of immunotherapies in enhancing immune cytotoxicity. Optical metabolic imaging and microfluidic models provide novel insight into metabolic dynamics with tumor cell and immune cell interactions within the tumor metabolic microenvironment. Future studies will expand this technology towards studying immune exhaustion and dysfunction in other immune therapies.

Citation Format: Shujah H. Rehman, Jose M. Ayuso, Maria Maria Virumbrales-Munoz, Patrick H. McMinn, David J. Beebe, Melissa C. Skala. Monitoring immune-tumor cell interactions in 3D microfluidic models with optical metabolic imaging and molecular profiling [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3874.

Abstract A107: Microfluidics and oncoimmunology: New in vitro models to study solid tumor immunotherapy

Immunotherapies against solid tumors face daunting challenges compared with hematologic cancers. In solid tumors, immune cells and antibodies need to extravasate from the vasculature, find the tumor cells, and migrate through a dense mass of normal and tumor cells where nutrients are depleted and waste products build up. All these factors pose significant obstacles for solid tumor immunotherapy, commonly leading to immune exhaustion and compromising the immune response. Thus, finding effective immunotherapies against solid tumors requires in vitro models that accurately capture the tumor complexity. In this work, we present microfluidic models for solid tumor immunotherapy and show how they mimic the tumor architecture in an unprecedented way compared with other traditional in vitro models based on Petri dishes. Breast cancer cells were cultured as a dense mass and embedded in a 3D collagen hydrogel into a microfluidic device. Endothelial cells were cultured in lateral flanking lumens to mimic the blood vessels, allowing the perfusion of therapeutic antibodies or effector immune cells (e.g., natural killer cells). Antibody and immune cell extravasation, diffusion, migration, and tumor clearance were evaluated in the model, showing the NK cell capacity to detect the presence of the tumor hundreds of microns away. Once inside the tumor mass, real-time microscopy revealed natural killer cells were able to destroy tumor cells at the tumor periphery and, more importantly, also at the innermost layers. The combination of antibodies and natural killer cells led to an enhanced cytotoxicity, showing the potential of the model to evaluate new immunotherapy combinations. Finally, tumor, endothelial, and NK cells were retrieved at different locations of the tumor (e.g., tumor margin vs. tumor core) and at different time points to show how these different cell populations adapted to the continuously evolving tumor microenvironment.

Citation Format: Jose M. Ayuso, Maria Virumbrales-Munoz, Patrick H. McMinn, Shujah Rehman, Cate M. Fitzgerald, David J. Beebe, Melissa C. Skala. Microfluidics and oncoimmunology: New in vitro models to study solid tumor immunotherapy [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A107.

Human Tumor-Lymphatic Microfluidic Model Reveals Differential Conditioning of Lymphatic Vessels by Breast Cancer Cells

Breast tumor progression is a complex process involving intricate crosstalk between the primary tumor and its microenvironment. In the context of breast tumor-lymphatic interactions, it is unclear how breast cancer cells alter the gene expression of lymphatic endothelial cells and how these transcriptional changes potentiate lymphatic dysfunction. Thus, there is a need for in vitro lymphatic vessel models to study these interactions. In this work, a tumor-lymphatic microfluidic model is developed to study the differential conditioning of lymphatic vessels by estrogen receptor-positive (i.e., MCF7) and triple-negative (i.e., MDA-MB-231) breast cancer cells. The model consists of a lymphatic endothelial vessel cultured adjacently to either MCF7 or MDA-MB-231 cells. Quantitative transcriptional analysis reveals expression changes in genes related to vessel growth, permeability, metabolism, hypoxia, and apoptosis in lymphatic endothelial cells cocultured with breast cancer cells. Interestingly, these changes are different in the MCF7-lymphatic cocultures as compared to the 231-lymphatic cocultures. Importantly, these changes in gene expression correlate to functional responses, such as endothelial barrier dysfunction. These results collectively demonstrate the utility of this model for studying breast tumor-lymphatic crosstalk for multiple breast cancer subtypes.

Development of a Microfluidic Array to Study Drug Response in Breast Cancer

Luminal geometries are common structures in biology, which are challenging to mimic using conventional in vitro techniques based on the use of Petri dishes. In this context, microfluidic systems can mimic the lumen geometry, enabling a large variety of studies. However, most microfluidic models still rely on polydimethylsiloxane (PDMS), a material that is not amenable for high-throughput fabrication and presents some limitations compared with other materials such as polystyrene. Thus, we have developed a microfluidic device array to generate multiple bio-relevant luminal structures utilizing polystyrene and micro-milling. This platform offers a scalable alternative to conventional microfluidic devices designed in PDMS. Additionally, the use of polystyrene has well described advantages, such as lower permeability to hydrophobic molecules compared with PDMS, while maintaining excellent viability and optical properties. Breast cancer cells cultured in the devices exhibited high cell viability similar to PDMS-based microdevices. Further, co-culture experiments with different breast cell types showed the potential of the model to study breast cancer invasion. Finally, we demonstrated the potential of the microfluidic array for drug screening, testing chemotherapy drugs and photodynamic therapy agents for breast cancer.

Tumor-on-a-chip: a microfluidic model to study cell response to environmental gradients

Limited blood supply and rapid tumor metabolism within solid tumors leads to nutrient starvation, waste product accumulation and the generation of pH gradients across the tumor mass. These environmental conditions modify multiple cellular functions, including metabolism, proliferation, and drug response. However, capturing the spatial metabolic and phenotypic heterogeneity of the tumor with classic in vitro models remains challenging. Thus, in this work a microfluidic tumor slice model was developed to study cell behavior under metabolic starvation gradients. The presented microdevice comprises a central chamber where tumor cells were cultured in a 3D collagen hydrogel. A lumen on the flank of the chamber was used to perfuse media, mimicking the vasculature. Under these circumstances, tumor cell metabolism led to the generation of viability, proliferation and pH gradients. The model decoupled the influence of oxygen from other nutrients, revealing that cell necrosis at the core of the model could be explained by nutrient starvation. The microdevice can be disassembled to retrieve the cells from the desired locations to study molecular adaptions due to nutrient starvation. When exposed to these pH gradients and low nutrient conditions, cancer cells showed multiple changes in their gene expression profile depending on their distance from the lumen. Those cells located further from the lumen upregulated several genes related to stress and survival response, whereas genes related to proliferation and DNA repair were downregulated. This model may help to identify new therapeutic opportunities to target the metabolic heterogeneity observed in solid tumors.

Enabling cell recovery from 3D cell culture microfluidic devices for tumour microenvironment biomarker profiling

The tumour microenvironment (TME) has recently drawn much attention due to its profound impact on tumour development, drug resistance and patient outcome. There is an increasing interest in new therapies that target the TME. Nonetheless, most established in vitro models fail to include essential cues of the TME. Microfluidics can be used to reproduce the TME in vitro and hence provide valuable insight on tumour evolution and drug sensitivity. However, microfluidics remains far from well-established mainstream molecular and cell biology methods. Therefore, we have developed a quick and straightforward collagenase-based enzymatic method to recover cells embedded in a 3D hydrogel in a microfluidic device with no impact on cell viability. We demonstrate the validity of this method on two different cell lines in a TME microfluidic model. Cells were successfully retrieved with high viability, and we characterised the different cell death mechanisms via AMNIS image cytometry in our model.

Evaluating natural killer cell cytotoxicity against solid tumors using a microfluidic model

Immunotherapies against solid tumors face additional challenges compared with hematological cancers. In solid tumors, immune cells and antibodies need to extravasate from vasculature, find the tumor, and migrate through a dense mass of cells. These multiple steps pose significant obstacles for solid tumor immunotherapy and their study has remained difficult using classic in vitro models based on Petri dishes. In this work, a microfluidic model has been developed to study natural killer cell response. The model includes a 3D breast cancer spheroid in a 3D extracellular matrix, and two flanking lumens lined with endothelial cells, replicating key structures and components during the immune response. Natural Killer cells and antibodies targeting the tumor cells were either embedded in the matrix or perfused through the lateral blood vessels. Antibodies that were perfused through the lateral lumens extravasated out of the blood vessels and rapidly diffused through the matrix. However, tumor cell-cell junctions hindered antibody penetration within the spheroid. On the other hand, natural killer cells were able to detect the presence of the tumor spheroid several hundreds of microns away and penetrate the spheroid faster than the antibodies. Once inside the spheroid, natural killer cells were able to destroy tumor cells at the spheroid periphery and, importantly, also at the innermost layers. Finally, the combination of antibody-cytokine conjugates and natural killer cells led to an enhanced cytotoxicity located mostly at the spheroid periphery. Overall, these results demonstrate the utility of the model for informing immunotherapy of solid tumors.

Organotypic microfluidic breast cancer model reveals starvation-induced spatial-temporal metabolic adaptations

BACKGROUND

Ductal carcinoma in situ (DCIS) is the earliest stage of breast cancer. During DCIS, tumor cells remain inside the mammary duct, growing under a microenvironment characterized by hypoxia, nutrient starvation, and waste product accumulation; this harsh microenvironment promotes genomic instability and eventually cell invasion. However, there is a lack of biomarkers to predict what patients will transition to a more invasive tumor or how DCIS cells manage to survive in this harsh microenvironment.

METHODS

In this work, we have developed a microfluidic model that recapitulates the DCIS microenvironment. In the microdevice, a DCIS model cell line was grown inside a luminal mammary duct model, embedded in a 3D hydrogel with mammary fibroblasts. Cell behavior was monitored by confocal microscopy and optical metabolic imaging. Additionally, metabolite profile was studied by NMR whereas gene expression was analyzed by RT-qPCR.

FINDINGS

DCIS cell metabolism led to hypoxia and nutrient starvation; revealing an altered metabolism focused on glycolysis and other hypoxia-associated pathways. In response to this starvation and hypoxia, DCIS cells modified the expression of multiple genes, and a gradient of different metabolic phenotypes was observed across the mammary duct model. These genetic changes observed in the model were in good agreement with patient genomic profiles; identifying multiple compounds targeting the affected pathways. In this context, the hypoxia-activated prodrug tirapazamine selectively destroyed hypoxic DCIS cells.

INTERPRETATION

The results showed the capacity of the microfluidic model to mimic the DCIS structure, identifying multiple cellular adaptations to endure the hypoxia and nutrient starvation generated within the mammary duct. These findings may suggest new potential therapeutic directions to treat DCIS. In summary, given the lack of in vitro models to study DCIS, this microfluidic device holds great potential to find new DCIS predictors and therapies and translate them to the clinic.

Glioblastoma on a microfluidic chip: Generating pseudopalisades and enhancing aggressiveness through blood vessel obstruction events

Background

Glioblastoma (GBM) is one of the most lethal tumor types. Hypercellular regions, named pseudopalisades, are characteristic in these tumors and have been hypothesized to be waves of migrating glioblastoma cells. These "waves" of cells are thought to be induced by oxygen and nutrient depletion caused by tumor-induced blood vessel occlusion. Although the universal presence of these structures in GBM tumors suggests that they may play an instrumental role in GBM's spread and invasion, the recreation of these structures in vitro has remained challenging.

Methods

Here we present a new microfluidic model of GBM that mimics the dynamics of pseudopalisade formation. To do this, we embedded U-251 MG cells within a collagen hydrogel in a custom-designed microfluidic device. By controlling the medium flow through lateral microchannels, we can mimic and control blood-vessel obstruction events associated with this disease.

Results

Through the use of this new system, we show that nutrient and oxygen starvation triggers a strong migratory process leading to pseudopalisade generation in vitro. These results validate the hypothesis of pseudopalisade formation and show an excellent agreement with a systems-biology model based on a hypoxia-driven phenomenon.

Conclusions

This paper shows the potential of microfluidic devices as advanced artificial systems capable of modeling in vivo nutrient and oxygen gradients during tumor evolution.

Hypoxia in Gliomas: Opening Therapeutical Opportunities Using a Mathematical-Based Approach

This chapter explores the use of mathematical models as promising and powerful tools to understand the complexity of tumors and their, frequently, hypoxic environment. We focus on gliomas, which are primary brain tumors derived from glial cells, mainly astrocytes and/or oligodendrocytes. A variety of mathematical models, based on ordinary and/or partial differential equations, have been developed both at the micro and macroscopic levels. The aim here is to describe in a quantitative way key physiopathological mechanisms relevant in these types of malignancies and to suggest optimal therapeutical strategies. More specifically, we consider novel therapies targeting thromboembolic phenomena to decrease cell invasion in high grade glioma or to delay the malignant transformation in low grade gliomas. This study has been the basis of a multidisciplinary collaboration involving, among others, neuro-oncologists, radiation oncologists, pathologists, cancer biologists, surgeons and mathematicians.

Agarose Spot as a Comparative Method for in situ Analysis of Simultaneous Chemotactic Responses to Multiple Chemokines

We describe a novel protocol to quantitatively and simultaneously compare the chemotactic responses of cells towards different chemokines. In this protocol, droplets of agarose gel containing different chemokines are applied onto the surface of a Petri dish, and then immersed under culture medium in which cells are suspended. As chemokine molecules diffuse away from the spot, a transient chemoattractant gradient is established across the spots. Cells expressing the corresponding cognate chemokine receptors migrate against this gradient by crawling under the agarose spots towards their centre. We show that this migration is chemokine-specific; meaning that only cells that express the cognate chemokine cell surface receptor, migrate under the spot containing its corresponding chemokine ligand. Furthermore, we show that migration under the agarose spot can be modulated by selective small molecule antagonists present in the cell culture medium.

Development and characterization of a microfluidic model of the tumour microenvironment

The physical microenvironment of tumours is characterized by heterotypic cell interactions and physiological gradients of nutrients, waste products and oxygen. This tumour microenvironment has a major impact on the biology of cancer cells and their response to chemotherapeutic agents. Despite this, most in vitro cancer research still relies primarily on cells grown in 2D and in isolation in nutrient- and oxygen-rich conditions. Here, a microfluidic device is presented that is easy to use and enables modelling and study of the tumour microenvironment in real-time. The versatility of this microfluidic platform allows for different aspects of the microenvironment to be monitored and dissected. This is exemplified here by real-time profiling of oxygen and glucose concentrations inside the device as well as effects on cell proliferation and growth, ROS generation and apoptosis. Heterotypic cell interactions were also studied. The device provides a live 'window' into the microenvironment and could be used to study cancer cells for which it is difficult to generate tumour spheroids. Another major application of the device is the study of effects of the microenvironment on cellular drug responses. Some data is presented for this indicating the device's potential to enable more physiological in vitro drug screening.

Abstract B04: An in vitro model for glioblastoma using microfluidics: Generating pseudopalisades on a chip

Glioblastoma (GBM), also named grade IV astrocytoma, is the most common and lethal malignant primary brain tumor. GBM is characterized by two main histopathological conditions: necrotic foci typically surrounded by areas of high cellularity and microvascular proliferation.

The causes of such densely populated regions, known a “pseudopalisades”, remain poorly understood. Firstly, high cellularity was thought to be due to the rapid proliferation of GBM cells, however recent histological studies have shown that proliferation in pseudopalisading areas is significantly lower than in adjacent regions. Additionally, in pseudopalisades, apoptosis is substantially larger than in neighboring regions. These evidences suggest that pseudopalisades are due to other causes than simply higher proliferation or survival rates. Recent reports have pointed out that, in histological slices from GBM patients, more than 50% of pseudopalisades present clearly a central obstructed blood vessel and in more than 90% microscopic evidences of thrombosis are observed.

As a consequence, oxygen and nutrients supply is compromised around the surrounding zones. It has been proposed that one of the driven forces of glioma aggressiveness is these nutrient and oxygen starvation. According to this hypothesis, GBM cell proliferation and secretion of pro-coagulant signals would cause thrombotic events, leading to hypoxia and nutrient depletion in the microenvironment. As a consequence, cells migrate towards nutrients and oxygen enriched regions, creating the characteristic GBM pseudopalisades. Eventually, these migrating cells would reach other blood vessels and eventually cause the collapse of these vessels, restarting the process and creating an expansive wave of tumor cells across the brain.

This complex process is hardly reproducible using “in vitro” models because the conventional migration assays are unable to mimic the complex microenvironment described. Recently, microfabrication and microfluidic technologies have arisen as interesting alternatives for creating high-performance cell culture systems. In this paper we describe the design, fabrication and biological validation of a microfluidic device using SU-8 technology for three-dimensional GBM cell cultures under thrombotic conditions. The fabricated microdevice possesses a central microchamber to locate the cells embedded within a hydrogel, mimicking the ECM and allowing migration in three dimensions. On both sides of the microchamber, two lateral microchannels are filled with culture medium, allowing nutrient and oxygen diffusion towards the microchamber, mimicking the brain blood vessels.

In this study we have demonstrated the GBM cells (U-251-MG) viability within the microdevice. Moreover, controlling medium flow through lateral microchannels we can mimic the GBM-associated thrombotic pathophysiological conditions. Under these thrombotic circumstances nutrient starvation leads to a chemotactic process and the formation of a migratory front similar to the pseudopalisades observed in vivo and validated with mathematical algorithms. Moreover, our results suggest that the whole process stimulates a more aggressive behavior of GBM cells. In an early stage when nutrients are plenty, GBM cells remain in a non-invasive phenotype. When nutrients are depleted, GBM cells initiate a migration process towards enriched regions, leading to the pseudopalisade formation. When compared with patient´s tumor pathology images, GBM cell invasion behavior follow the same pattern observed in vivo. This novel technique could help us to understand the mechanism of the pseudopalisade formation and to suggest novel therapeutic targets to avoid tumor progression. Besides, these microfluidic devices could represent an extremely useful platform to test new anticancer agents in a preclinical setting that mimics the complex GBM microenvironment.

Citation Format: Jose M. Ayuso, Rosa Monge, Alicia Martínez-González, Guillermo A. Llamazares, Javier Berganzo, Aurelio Hernández-Laín, Jorge Santolaria, Manuel Doblaré, Pilar Sánchez-Gómez, Víctor M. Pérez-García, Ignacio Ochoa, Luis J. Fernández. An in vitro model for glioblastoma using microfluidics: Generating pseudopalisades on a chip. [abstract]. In: Proceedings of the AACR Special Conference: Advances in Brain Cancer Research; May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr B04.

Specific binding of DNA to aggregated forms of Alzheimer's disease amyloid peptides

Anomalous protein aggregation is closely associated to age-related mental illness. Extraneuronal plaques, mainly composed of aggregated amyloid peptides, are considered as hallmarks of Alzheimer's disease. According to the amyloid cascade hypothesis, this disease starts as a consequence of an abnormal processing of the amyloid precursor protein resulting in an excess of amyloid peptides. Nuclear localization of amyloid peptide aggregates together with amyloid-DNA interaction, have been repeatedly reported. In this paper we have used surface plasmon resonance and electron microscopy to study the structure and behavior of different peptides and proteins, including β-lactoglobulin, bovine serum albumin, myoglobin, histone, casein and the amyloid-β peptides related to Alzheimer's disease Aβ25-35 and Aβ1-40. The main purpose of this study is to investigate whether proneness to DNA interaction is a general property displayed by aggregated forms of proteins, or it is an interaction specifically related to the aggregated forms of those particular proteins and peptides related to neurodegenerative diseases. Our results reveal that those aggregates formed by amyloid peptides show a particular proneness to interact with DNA. They are the only aggregated structures capable of binding DNA, and show more affinity for DNA than for other polyanions like heparin and polyglutamic acid, therefore strengthening the hypothesis that amyloid peptides may, by means of interaction with nuclear DNA, contribute to the onset of Alzheimer's disease.