Engineered Three-Dimensional Tumor Models to Study Natural Killer Cell Suppression

In Vitro Modeling of Idiopathic Pulmonary Fibrosis: Lung-on-a-Chip Systems and Other 3D Cultures

Idiopathic pulmonary fibrosis (IPF) is a lethal disorder characterized by relentless progression of lung fibrosis that causes respiratory failure and early death. Currently, no curative treatments are available, and existing therapies include a limited selection of antifibrotic agents that only slow disease progression. The development of novel therapeutics has been hindered by a limited understanding of the disease's etiology and pathogenesis. A significant challenge in developing new treatments and understanding IPF is the lack of in vitro models that accurately replicate crucial microenvironments. In response, three-dimensional (3D) in vitro models have emerged as powerful tools for replicating organ-level microenvironments seen in vivo. This review summarizes the state of the art in advanced 3D lung models that mimic many physiological and pathological processes observed in IPF. We begin with a brief overview of conventional models, such as 2D cell cultures and animal models, and then explore more advanced 3D models, focusing on lung-on-a-chip systems. We discuss the current challenges and future research opportunities in this field, aiming to advance the understanding of the disease and the development of novel devices to assess the effectiveness of new IPF treatments.

Biofabrication Directions in Recapitulating the Immune System-on-a-Chip

Ever since the implementation of microfluidics in the biomedical field, in vitro models have experienced unprecedented progress that has led to a new generation of highly complex miniaturized cell culture platforms, known as Organs-on-a-Chip (OoC). These devices aim to emulate biologically relevant environments, encompassing perfusion and other mechanical and/or biochemical stimuli, to recapitulate key physiological events. While OoCs excel in simulating diverse organ functions, the integration of the immune organs and immune cells, though recent and challenging, is pivotal for a more comprehensive representation of human physiology. This comprehensive review covers the state of the art in the intricate landscape of immune OoC models, shedding light on the pivotal role of biofabrication technologies in bridging the gap between conceptual design and physiological relevance. The multifaceted aspects of immune cell behavior, crosstalk, and immune responses that are aimed to be replicated within microfluidic environments, emphasizing the need for precise biomimicry are explored. Furthermore, the latest breakthroughs and challenges of biofabrication technologies in immune OoC platforms are described, guiding researchers toward a deeper understanding of immune physiology and the development of more accurate and human predictive models for a.o., immune-related disorders, immune development, immune programming, and immune regulation.

Natural Killer Cell Mechanosensing in Solid Tumors

Natural killer (NK) cells, which are an exciting alternative cell source for cancer immunotherapies, must sense and respond to their physical environment to traffic to and eliminate cancer cells. Herein, we review the mechanisms by which NK cells receive mechanical signals and explore recent key findings regarding the impact of the physical characteristics of solid tumors on NK cell functions. Data suggest that different mechanical stresses present in solid tumors facilitate NK cell functions, especially infiltration and degranulation. Moreover, we review recent engineering advances that can be used to systemically study the role of mechanical forces on NK cell activity. Understanding the mechanisms by which NK cells interpret their environment presents potential targets to enhance NK cell immunotherapies for the treatment of solid tumors.

In vitro models to study natural killer cell dynamics in the tumor microenvironment

Immunotherapy is revolutionizing cancer therapy. The rapid development of new immunotherapeutic strategies to treat solid tumors is posing new challenges for preclinical research, demanding novel in vitro methods to test treatments. Such methods should meet specific requirements, such as enabling the evaluation of immune cell responses like cytotoxicity or cytokine release, and infiltration into the tumor microenvironment using cancer models representative of the original disease. They should allow high-throughput and high-content analysis, to evaluate the efficacy of treatments and understand immune-evasion processes to facilitate development of new therapeutic targets. Ideally, they should be suitable for personalized immunotherapy testing, providing information for patient stratification. Consequently, the application of in vitro 3-dimensional (3D) cell culture models, such as tumor spheroids and organoids, is rapidly expanding in the immunotherapeutic field, coupled with the development of novel imaging-based techniques and -omic analysis. In this paper, we review the recent advances in the development of in vitro 3D platforms applied to natural killer (NK) cell-based cancer immunotherapy studies, highlighting the benefits and limitations of the current methods, and discuss new concepts and future directions of the field.

Functional Interrogation of Ca2+ Signals in Human Cancer Cells In Vitro and Ex Vivo by Fluorescent Microscopy and Molecular Tools

Genetically encoded calcium indicators (GECIs) and high-resolution confocal microscopy enable dynamic visualization of calcium signals in cells and tissues. Two-dimensional and 3D biocompatible materials mimic the mechanical microenvironments of tumor and healthy tissues in a programmable manner. Cancer xenograft models and ex vivo functional imaging of tumor slices reveal physiologically relevant functions of calcium dynamics in tumors at different progression stages. Integration of these powerful techniques allows us to quantify, diagnose, model, and understand cancer pathobiology. Here, we describe detailed materials and methods used to establish this integrated interrogation platform, from generating transduced cancer cell lines that stably express CaViar (GCaMP5G + QuasAr2) to in vitro and ex vivo calcium imaging of the cells in 2D/3D hydrogels and tumor tissues. These tools open the possibility for detailed explorations of mechano-electro-chemical network dynamics in living systems.

Reductionist Three-Dimensional Tumor Microenvironment Models in Synthetic Hydrogels

Simple Summary

Tumors exist in a complex, three-dimensional environment which helps them to survive, grow, metastasize, and resist drug treatment. Simple, reproducible, in vitro models of this environment are necessary in order to better understand tumor behavior. Naturally derived polymers are great 3D cell culture substrates, but they often lack the tunability and batch-to-batch consistency which can be found in synthetic polymer systems. In this review, we describe the current state of and future directions for tumor microenvironment models in synthetic hydrogels.

Abstract

The tumor microenvironment (TME) plays a determining role in everything from disease progression to drug resistance. As such, in vitro models which can recapitulate the cell–cell and cell–matrix interactions that occur in situ are key to the investigation of tumor behavior and selecting effective therapeutic drugs. While naturally derived matrices can retain the dimensionality of the native TME, they lack tunability and batch-to-batch consistency. As such, many synthetic polymer systems have been employed to create physiologically relevant TME cultures. In this review, we discussed the common semi-synthetic and synthetic polymers used as hydrogel matrices for tumor models. We reviewed studies in synthetic hydrogels which investigated tumor cell interactions with vasculature and immune cells. Finally, we reviewed the utility of these models as chemotherapeutic drug-screening platforms, as well as the future directions of the field.

Clinical Application Perspectives of Lung Cancers 3D Tumor Microenvironment Models for In Vitro Cultures

Despite the enormous progress and development of modern therapies, lung cancer remains one of the most common causes of death among men and women. The key element in the development of new anti-cancer drugs is proper planning of the preclinical research phase. The most adequate basic research exemplary for cancer study are 3D tumor microenvironment in vitro models, which allow us to avoid the use of animal models and ensure replicable culture condition. However, the question tormenting the scientist is how to choose the best tool for tumor microenvironment research, especially for extremely heterogenous lung cancer cases. In the presented review we are focused to explain the key factors of lung cancer biology, its microenvironment, and clinical gaps related to different therapies. The review summarized the most important strategies for in vitro culture models mimicking the tumor–tumor microenvironmental interaction, as well as all advantages and disadvantages were depicted. This knowledge could facilitate the right decision to designate proper pre-clinical in vitro study, based on available analytical tools and technical capabilities, to obtain more reliable and personalized results for faster introduction them into the future clinical trials.

Tumor Microenvironment and Hydrogel-Based 3D Cancer Models for In Vitro Testing Immunotherapies

In recent years, immunotherapy has emerged as a promising novel therapeutic strategy for cancer treatment. In a relevant percentage of patients, however, clinical benefits are lower than expected, pushing researchers to deeply analyze the immune responses against tumors and find more reliable and efficient tools to predict the individual response to therapy. Novel tissue engineering strategies can be adopted to realize in vitro fully humanized matrix-based models, as a compromise between standard two-dimensional (2D) cell cultures and animal tests, which are costly and hardly usable in personalized medicine. In this review, we describe the main mechanisms allowing cancer cells to escape the immune surveillance, which may play a significant role in the failure of immunotherapies. In particular, we discuss the role of the tumor microenvironment (TME) in the establishment of a milieu that greatly favors cancer malignant progression and impact on the interactions with immune cells. Then, we present an overview of the recent in vitro engineered preclinical three-dimensional (3D) models that have been adopted to resemble the interplays between cancer and immune cells and for testing current therapies and immunotherapeutic approaches. Specifically, we focus on 3D hydrogel-based tools based on different types of polymers, discussing the suitability of each of them in reproducing the TME key features based on their intrinsic or tunable characteristics. Finally, we introduce the possibility to combine the 3D models with technological fluid dynamics platforms, reproducing the dynamic complex interactions between tumor cells and immune effectors migrated in situ via the systemic circulation, pointing out the challenges that still have to be overcome for setting more predictive preclinical assays.

PRDX-1 Supports the Survival and Antitumor Activity of Primary and CAR-Modified NK Cells under Oxidative Stress

Oxidative stress, caused by the imbalance between reactive species generation and the dysfunctional capacity of antioxidant defenses, is one of the characteristic features of cancer. Here, we quantified hydrogen peroxide in the tumor microenvironment (TME) and demonstrated that hydrogen peroxide concentrations are elevated in tumor interstitial fluid isolated from murine breast cancers in vivo, when compared with blood or normal subcutaneous fluid. Therefore, we investigated the effects of increased hydrogen peroxide concentration on immune cell functions. NK cells were more susceptible to hydrogen peroxide than T cells or B cells, and by comparing T, B, and NK cells' sensitivities to redox stress and their antioxidant capacities, we identified peroxiredoxin-1 (PRDX1) as a lacking element of NK cells' antioxidative defense. We observed that priming with IL15 protected NK cells' functions in the presence of high hydrogen peroxide and simultaneously upregulated PRDX1 expression. However, the effect of IL15 on PRDX1 expression was transient and strictly dependent on the presence of the cytokine. Therefore, we genetically modified NK cells to stably overexpress PRDX1, which led to increased survival and NK cell activity in redox stress conditions. Finally, we generated PD-L1-CAR NK cells overexpressing PRDX1 that displayed potent antitumor activity against breast cancer cells under oxidative stress. These results demonstrate that hydrogen peroxide, at concentrations detected in the TME, suppresses NK cell function and that genetic modification strategies can improve CAR NK cells' resistance and potency against solid tumors.

Engineering microenvironments for manufacturing therapeutic cells

There are a growing number of globally approved products and clinical trials utilizing autologous and allogeneic therapeutic cells for applications in regenerative medicine and immunotherapies. However, there is a need to develop rapid and cost-effective methods for manufacturing therapeutically effective cells. Furthermore, the resulting manufactured cells may exhibit heterogeneities that result in mixed therapeutic outcomes. Engineering approaches that can provide distinct microenvironmental cues to these cells may be able to enhance the growth and characterization of these cell products. This mini-review describes strategies to potentially enhance the expansion of therapeutic cells with biomaterials and bioreactors, as well as to characterize the cell products with microphysiological systems. These systems can provide distinct cues to maintain the quality attributes of the cells and evaluate their function in physiologically relevant conditions.

Three-Dimensional Culture Models to Study Innate Anti-Tumor Immune Response: Advantages and Disadvantages

Several approaches have shown that the immune response against tumors strongly affects patients' clinical outcome. Thus, the study of anti-tumor immunity is critical to understand and potentiate the mechanisms underlying the elimination of tumor cells. Natural killer (NK) cells are members of innate immunity and represent powerful anti-tumor effectors, able to eliminate tumor cells without a previous sensitization. Thus, the study of their involvement in anti-tumor responses is critical for clinical translation. This analysis has been performed in vitro, co-incubating NK with tumor cells and quantifying the cytotoxic activity of NK cells. In vivo confirmation has been applied to overcome the limits of in vitro testing, however, the innate immunity of mice and humans is different, leading to discrepancies. Different activating receptors on NK cells and counter-ligands on tumor cells are involved in the antitumor response, and innate immunity is strictly dependent on the specific microenvironment where it takes place. Thus, three-dimensional (3D) culture systems, where NK and tumor cells can interact in a tissue-like architecture, have been created. For example, tumor cell spheroids and primary organoids derived from several tumor types, have been used so far to analyze innate immune response, replacing animal models. Herein, we briefly introduce NK cells and analyze and discuss in detail the properties of 3D tumor culture systems and their use for the study of tumor cell interactions with NK cells.