3D hanging spheroid plate for high-throughput CAR T cell cytotoxicity assay

Diffusion-based culture and real-time impedance monitoring of tumor spheroids in hydrogel microwells of a suspended membrane under microfluidic conditions

Tumor spheroids are widely studied for in vitro modeling of tumor growth and responses to anticancer drugs. However, current methods are mostly limited to static and perfusion-based cultures, which can be improved by more accurately mimicking pathological conditions. Here, we developed a diffusion-based dynamic culture system for tumor spheroids studies using a thin membrane of hydrogel microwells and a microfluidic device. This allows for effective exchange of nutrients and metabolites between the tumors and the culture medium flowing underneath, resulting in uniform tumor spheroids. To monitor the growth and drug response of the spheroids in real-time, we performed spectroscopic analyses of the system's impedance, demonstrating a close correlation between the tumor size and the resistance and capacitance of the system. Our results also indicate an enhanced drug effect on the tumor spheroids in the presence of a low AC electric field, suggesting a weakening mechanism of the spheroids induced by external perturbation.

CAR T cell infiltration and cytotoxic killing within the core of 3D breast cancer spheroids under the control of antigen sensing in microwell arrays

The success of chimeric antigen receptor (CAR) T cells in blood cancers has intensified efforts to develop CAR T therapies for solid cancers. In the solid tumor microenvironment, CAR T cell trafficking and suppression of cytotoxic killing represent limiting factors for therapeutic efficacy. Here, we present a microwell platform to study CAR T cell interactions with 3D breast tumor spheroids and determine predictors of anti-tumor CAR T cell function. To precisely control antigen sensing, we utilized a switchable adaptor CAR system that covalently attaches to co-administered antibody adaptors and mediates antigen recognition. Following the addition of an anti-HER2 adaptor antibody, primary human CAR T cells exhibited higher infiltration, clustering, and secretion of effector cytokines. By tracking CAR T cell killing in individual spheroids, we showed the suppressive effects of spheroid size and identified the initial CAR T cell to spheroid area ratio as a predictor of cytotoxicity. We demonstrate that larger spheroids exhibit higher hypoxia levels and are infiltrated by CAR T cells with a suppressed activation state, characterized by reduced expression of IFN-γ, TNF-α, and granzyme B. Spatiotemporal analysis revealed lower CAR T cell numbers and cytotoxicity in the spheroid core compared to the periphery. Finally, increasing CAR T cell seeding density resulted in higher CAR T cell infiltration and cancer cell elimination in the spheroid core. Our findings provide new quantitative insight into CAR T cell function within 3D cancer spheroids. Given its miniaturized nature and live imaging capabilities, our microfabricated system holds promise for screening cellular immunotherapies.

Reshaping the tumor immune microenvironment to improve CAR-T cell-based cancer immunotherapy

In many hematologic malignancies, the adoptive transfer of chimeric antigen receptor (CAR) T cells has demonstrated notable success; nevertheless, further improvements are necessary to optimize treatment efficacy. Current CAR-T therapies are particularly discouraging for solid tumor treatment. The immunosuppressive microenvironment of tumors affects CAR-T cells, limiting the treatment's effectiveness and safety. Therefore, enhancing CAR-T cell infiltration capacity and resolving the immunosuppressive responses within the tumor microenvironment could boost the anti-tumor effect. Specific strategies include structurally altering CAR-T cells combined with targeted therapy, radiotherapy, or chemotherapy. Overall, monitoring the tumor microenvironment and the status of CAR-T cells is beneficial in further investigating the viability of such strategies and advancing CAR-T cell therapy.

Tumoroids, a valid preclinical screening platform for monitoring cancer angiogenesis

In recent years, biologists and clinicians have witnessed prominent advances in in vitro 3D culture techniques related to biomimetic human/animal tissue analogs. Numerous data have confirmed that unicellular and multicellular (tumoroids) tumor spheroids with dense native cells in certain matrices are sensitive and valid analytical tools for drug screening, cancer cell dynamic growth, behavior, etc. in laboratory settings. Angiogenesis/vascularization is a very critical biological phenomenon to support oxygen and nutrients to tumor cells within the deep layer of solid masses. It has been shown that endothelial cell (EC)-incorporated or -free spheroid/tumoroid systems provide a relatively reliable biological platform for monitoring the formation of nascent blood vessels in micron/micrometer scales. Besides, the paracrine angiogenic activity of cells within the spheroid/tumoroid systems can be monitored after being treated with different therapeutic approaches. Here, we aimed to collect recent advances and findings related to the monitoring of cancer angiogenesis using unicellular and multicellular tumor spheroids. Vascularized spheroids/tumoroids can help us in the elucidation of mechanisms related to cancer formation, development, and metastasis by monitoring the main influencing factors.

Advancements in 3D In Vitro Models for Colorectal Cancer

The process of drug discovery and pre-clinical testing is currently inefficient, expensive, and time-consuming. Most importantly, the success rate is unsatisfactory, as only a small percentage of tested drugs are made available to oncological patients. This is largely due to the lack of reliable models that accurately predict drug efficacy and safety. Even animal models often fail to replicate human-specific pathologies and human body's complexity. These factors, along with ethical concerns regarding animal use, urge the development of suitable human-relevant, translational in vitro models.

DMPK perspective on quantitative model analysis for chimeric antigen receptor cell therapy: Advances and challenges

Chimeric antigen receptor (CAR) cells are genetically engineered immune cells that specifically target tumor-associated antigens and have revolutionized cancer treatment, particularly in hematological malignancies, with ongoing investigations into their potential applications in solid tumors. This review provides a comprehensive overview of the current status and challenges in drug metabolism and pharmacokinetics (DMPK) for CAR cell therapy, specifically emphasizing on quantitative modeling and simulation (M&S). Furthermore, the recent advances in quantitative model analysis have been reviewed, ranging from clinical data characterization to mechanism-based modeling that connects in vitro and in vivo nonclinical and clinical study data. Additionally, the future perspectives and areas for improvement in CAR cell therapy translation have been reviewed. This includes using formulation quality considerations, characterization of appropriate animal models, refinement of in vitro models for bottom-up approaches, and enhancement of quantitative bioanalytical methodology. Addressing these challenges within a DMPK framework is pivotal in facilitating the translation of CAR cell therapy, ultimately enhancing the patients' lives through efficient CAR cell therapies.

Imaging-Based Efficacy Evaluation of Cancer Immunotherapy in Engineered Tumor Platforms and Tumor Organoids

Cancer immunotherapy is used to treat tumors by modulating the immune system. Although the anticancer efficacy of cancer immunotherapy has been evaluated prior to clinical trials, conventional in vivo animal and endpoint models inadequately replicate the intricate process of tumor elimination and reflect human-specific immune systems. Therefore, more sophisticated models that mimic the complex tumor-immune microenvironment must be employed to assess the effectiveness of immunotherapy. Additionally, using real-time imaging technology, a step-by-step evaluation can be applied, allowing for a more precise assessment of treatment efficacy. Here, an overview of the various imaging-based evaluation platforms recently developed for cancer immunotherapeutic applications is presented. Specifically, a fundamental technique is discussed for stably observing immune cell-based tumor cell killing using direct imaging, a microwell that reproduces a confined space for spatial observation, a droplet assay that facilitates cell-cell interactions, and a 3D microphysiological system that reconstructs the vascular environment. Furthermore, it is suggested that future evaluation platforms pursue more human-like immune systems.

CAR T cell infiltration and cytotoxic killing within the core of 3D breast cancer spheroids under control of antigen sensing in microwell arrays

The success of chimeric antigen receptor (CAR) T cells in blood cancers has intensified efforts to develop CAR T therapies for solid cancers. In the solid tumor microenvironment, CAR T cell trafficking and suppression of cytotoxic killing represent limiting factors for therapeutic efficacy. Here, we present a microwell platform to study CAR T cell interactions with 3D tumor spheroids and determine predictors of anti-tumor CAR T cell function. To precisely control antigen sensing by CAR T cells, we utilized a switchable adaptor CAR system, that instead of directly binding to an antigen of interest, covalently attaches to co-administered antibody adaptors that mediate tumor antigen recognition. Following addition of an anti-HER2 adaptor antibody, primary human CAR T cells exhibited higher infiltration and clustering compared to the no adaptor control. By tracking CAR T cell killing at the individual spheroid level, we showed the suppressive effects of spheroid size and identified the initial CAR T cell : spheroid area ratio as a predictor of cytotoxicity. Spatiotemporal analysis revealed lower CAR T cell numbers and cytotoxicity in the spheroid core compared to the periphery. Finally, increasing CAR T cell seeding density, resulted in higher CAR T cell infiltration and cancer cell elimination in the spheroid core. Our findings provide new quantitative insights into CAR T cell-mediated killing of HER2+ breast tumor cells. Given the miniaturized nature and live imaging capabilities, our microfabricated system holds promise for discovering cell-cell interaction mechanisms that orchestrate antitumor CAR T cell functions and screening cellular immunotherapies in 3D tumor models.

Networked Cluster Formation via Trigonal Lipid Modules for Augmented Ex Vivo NK Cell Priming

Current cytokine-based natural killer (NK) cell priming techniques have exhibited limitations such as the deactivation of biological signaling molecules and subsequent insufficient maturation of the cell population during mass cultivation processes. In this study, we developed an amphiphilic trigonal 1,2-distearoyl-sn-glycero-3-phosphorylethanolamine (DSPE) lipid-polyethylene glycol (PEG) material to assemble NK cell clusters via multiple hydrophobic lipid insertions into cellular membranes. Our lipid conjugate-mediated ex vivo NK cell priming sufficiently augmented the structural modulation of clusters, facilitated diffusional signal exchanges, and finally activated NK cell population with the clusters. Without any inhibition in diffusional signal exchanges and intrinsic proliferative efficacy of NK cells, effectively prime NK cell clusters produced increased interferon-gamma, especially in the early culture periods. In conclusion, the present study demonstrates that our novel lipid conjugates could serve as a promising alternative for future NK cell mass production.

A 3D hanging spheroid-filter plate for high-throughput drug testing and CAR T cell cytotoxicity assay

Tumour spheroids are widely used in immune cell cytotoxicity assays and anticancer drug testing, providing a physiologically relevant model replicating the tumour microenvironment. However, co-culture of immune and tumour cells complicates quantification of immune cell killing efficiency. We present a novel 3D hanging spheroid-filter plate that efficiently facilitates spheroid formation and separates unbound/dead cells during cytotoxicity assays. Optical imaging directly measures the cytotoxic effects of anti-cancer drugs on tumour spheroids, eliminating the need for live/dead fluorescent staining. This approach enables cost-effective evaluation of T-cell cytotoxicity with specific chimeric antigen receptors (CARs), enhancing immune cell-based assays and drug testing in three-dimensional tumour models.

Ex Vivo Surface Decoration of Phenylboronic Acid onto Natural Killer Cells for Sialic Acid-Mediated Versatile Cancer Cell Targeting

Phenylboronic acid (PBA) has been highly acknowledged as a significant cancer recognition moiety in sialic acid-overexpressing cancer cells. In this investigation, lipid-mediated biomaterial integrated PBA molecules onto the surface of natural killer (NK) cells to make a receptor-mediated immune cell therapeutic module. Therefore, a 1,2-distearoyl-sn-glycero-3-phosphorylethanolamine (DSPE) lipid-conjugated di-PEG-PBA (DSPEPEG-di(PEG-PBA) biomaterial was synthesized. The DSPEPEG-di(PEG-PBA) biomaterial exhibited a high affinity for sialic acid (SA), confirmed by fluorescence spectroscopy at pH 6.5 and 7.4. DSPEPEG-di(PEG-PBA) was successfully anchored onto NK cell surfaces (PBA-NK), and this biomaterial maintains intrinsic properties such as viability, ligand availability (FasL & TRAIL), and cytokine secretion response to LPS. The anticancer efficacy of PBA-NK cells was evaluated against 2D cancer cells (MDA-MB-231, HepG2, and HCT-116) and 3D tumor spheroids of MDA-MB-231 cells. PBA-NK cells exhibited greatly enhanced anticancer effects against SA-overexpressing cancer cells. Thus, PBA-NK cells represent a new anticancer strategy for cancer immunotherapy.

Three-Dimensional Hanging Drop Spheroid Plates for Easy Chimeric Antigen Receptor (CAR) T Cytotoxicity Assay

Chimeric antigen receptor (CAR) T cell therapy shows a highly effective therapeutic effect on B-cell malignancies. The tumor microenvironment (TME) of solid tumors in vivo poses a great challenge to CAR T cell therapy due to its complexity. Recently, tumor spheroids have attracted much attention because of their ability to recapitulate TME. However, the use of tumor spheroids for the CAR T cytotoxicity assay involves the difficult task of separating unbound T cells and dead tumor cells from the spheroids. Therefore, we developed a three-dimensional hanging spheroid plate (3DHSP) that facilitates spheroid formation and separation of unbound and dead cells from spheroids during cytotoxicity assays. In this work, detailed steps have been described for fabrication and operation of the 3DHSP. This new 3DHSP device is a 96-well plate in which each well consists of a hanging dripper and a spheroid separation plate. A tumor spheroid forms in a droplet hanging in the dripper and is mixed with CAR T cells. The mixture in the droplet is deposited into the spheroid separation plate by pipetting, and unbound and dead CAR T and tumor cells are detached from the spheroid and moved to the waste well in the plate by tilting the 3DHSP at 20°. The size of the spheroid can be used as a readout for CAR T cell cytotoxicity assay, suggesting that the 3DHSP does not require cumbersome fluorescent staining.

Phenotypic assay for cytotoxicity assessment of Balamuthia mandrillaris against human neurospheroids

Introduction

The phenotypic screening of drugs against Balamuthia mandrillaris, a neuropathogenic amoeba, involves two simultaneous phases: an initial step to test amoebicidal activity followed by an assay for cytotoxicity to host cells. The emergence of three-dimensional (3D) cell cultures has provided a more physiologically relevant model than traditional 2D cell culture for studying the pathogenicity of B. mandrillaris. However, the measurement of ATP, a critical indicator of cell viability, is complicated by the overgrowth of B. mandrillaris in coculture with host cells during drug screening, making it challenging to differentiate between amoebicidal activity and drug toxicity to human cells.

Methods

To address this limitation, we introduce a novel assay that utilizes three-dimensional hanging spheroid plates (3DHSPs) to evaluate both activities simultaneously on a single platform.

Results and discussion

Our study showed that the incubation of neurospheroids with clinically isolated B. mandrillaris trophozoites resulted in a loss of neurospheroid integrity, while the ATP levels in the neurospheroids decreased over time, indicating decreased host cell viability. Conversely, ATP levels in isolated trophozoites increased, indicating active parasite metabolism. Our findings suggest that the 3DHSP-based assay can serve as an endpoint for the phenotypic screening of drugs against B. mandrillaris, providing a more efficient and accurate approach for evaluating both parasite cytotoxicity and viability.

Mechanical Properties Affect Primary T Cell Activation in 3D Bioprinted Hydrogels

T cells play a critical role in the adaptive immune response of the body, especially against intracellular pathogens and cancer. In vitro, T cell activation studies typically employ planar (two-dimensional, 2D) culture systems that do not mimic native cell-to-extracellular matrix (ECM) interactions, which influence activation. The goal of this work was to study T cell responses in a cell line (EL4) and primary mouse T cells in three-dimensional (3D) bioprinted matrices of varied stiffness. Cell-laden hydrogels were 3D bioprinted from gelatin methacryloyl (GelMA) using a digital light processing (DLP)-based 3D bioprinter operated with visible light (405 nm). Mechanical characterization revealed that the hydrogels had pathophysiologically relevant stiffnesses for a lymph node-mimetic tissue construct. EL4, a mouse T cell lymphoma line, or primary mouse T cells were 3D bioprinted and activated using a combination of 10 ng/mL of phorbol myristate acetate (PMA) and 0.1 μM of ionomycin. Cellular responses revealed differences between 2D and 3D cultures and that the biomechanical properties of the 3D bioprinted hydrogel influence T cell activation. Cellular responses of the 2D and 3D cultures in a soft matrix (19.83 ± 2.36 kPa) were comparable; however, they differed in a stiff matrix (52.95 ± 1.36 kPa). The fraction of viable EL4 cells was 1.3-fold higher in the soft matrix than in the stiff matrix. Furthermore, primary mouse T cells activated with PMA and ionomycin showed 1.35-fold higher viable cells in the soft matrix than in the stiff matrix. T cells bioprinted in a soft matrix and a stiff matrix released 7.4-fold and 5.9-fold higher amounts of interleukin-2 (IL-2) than 2D cultured cells, respectively. Overall, the study demonstrates the changes in the response of T cells in 3D bioprinted scaffolds toward engineering an ex vivo lymphoid tissue-mimetic system that can faithfully recapitulate T cell activation and unravel pathophysiological characteristics of T cells in infectious biology, autoimmunity, and cancers.

Three-Dimensional Bioconjugated Liquid-Like Solid (LLS) Enhance Characterization of Solid Tumor - Chimeric Antigen Receptor T cell interactions

Cancer immunotherapy offers lifesaving treatments for cancers, but the lack of reliable preclinical models that could enable the mechanistic studies of tumor-immune interactions hampers the identification of new therapeutic strategies. We hypothesized 3D confined microchannels, formed by interstitial space between bio-conjugated liquid-like solids (LLS), enable CAR T dynamic locomotion within an immunosuppressive TME to carry out anti-tumor function. Murine CD70-specific CAR T cells cocultured with the CD70-expressing glioblastoma and osteosarcoma demonstrated efficient trafficking, infiltration, and killing of cancer cells. The anti-tumor activity was clearly captured via longterm in situ imaging and supported by upregulation of cytokines and chemokines including IFNg, CXCL9, CXCL10, CCL2, CCL3, and CCL4. Interestingly, target cancer cells, upon an immune attack, initiated an "immune escape" response by frantically invading the surrounding microenvironment. This phenomenon however was not observed for the wild-type tumor samples which remained intact and produced no relevant cytokine response. Single cells collection and transcriptomic profiling of CAR T cells at regions of interest revealed feasibility of identifying differential gene expression amongst the immune subpopulations. Complimentary 3D in vitro platforms are necessary to uncover cancer immune biology mechanisms, as emphasized by the significant roles of the TME and its heterogeneity.

Engineered Microphysiological Systems for Testing Effectiveness of Cell-Based Cancer Immunotherapies

Cell therapies, including adoptive immune cell therapies and genetically engineered chimeric antigen receptor (CAR) T or NK cells, have shown promise in treating hematologic malignancies. Yet, immune cell infiltration and expansion has proven challenging in solid tumors due to immune cell exclusion and exhaustion and the presence of vascular barriers. Testing next-generation immune therapies remains challenging in animals, motivating sophisticated ex vivo models of human tumor biology and prognostic assays to predict treatment response in real-time while comprehensively recapitulating the human tumor immune microenvironment (TIME). This review examines current strategies for testing cell-based cancer immunotherapies using ex vivo microphysiological systems and microfluidic technologies. Insights into the multicellular interactions of the TIME will identify novel therapeutic strategies to help patients whose tumors are refractory or resistant to current immunotherapies. Altogether, these microphysiological systems (MPS) have the capability to predict therapeutic vulnerabilities and biological barriers while studying immune cell infiltration and killing in a more physiologically relevant context, thereby providing important insights into fundamental biologic mechanisms to expand our understanding of and treatments for currently incurable malignancies.

An Optical and Chemiluminescence Assay for Assessing the Cytotoxicity of Balamuthia mandrillaris against Human Neurospheroids

A spheroid is a cell aggregate in a three-dimensional context; thereby, it recapitulates the cellular architecture in human tissue. However, the utility of spheroids as an assay for host–parasite interactions remains unexplored. This study demonstrates the potential use of neurospheroids for assessing the cytotoxicity of the life-threatening pathogenic amoeba Balamuthia mandrillaris. The neuroblastoma SH-SY5Y cells formed a spheroid in a hanging drop of culture medium. Cellular damage caused by B. mandrillaris trophozoites on human neuronal spheroids was observed using microscopic imaging and ATP detection. B. mandrillaris trophozoites rapidly caused a decrease in ATP production in the spheroid, leading to loss of neurospheroid integrity. Moreover, 3D confocal microscopy imaging revealed interactions between the trophozoites and SH-SY5Y neuronal cells in the outer layer of the neurospheroid. In conclusion, the neurospheroid allows the assessment of host cell damage in a simple and quantitative manner.

Assessment of CAR-T cell-mediated cytotoxicity in 3D microfluidic cancer co-culture models for combination therapy

Chimeric antigen receptor (CAR)-T cell therapy is efficacious against many haematological malignancies, but challenges remain when using this cellular immunotherapy for treating solid tumours. Classical 2D in vitro models fail to recapitulate the complexity of the tumour microenvironment, whilst in vivo models, such as patient-derived xenografts, are costly and labour intensive. Microfluidic technologies can provide miniaturized solutions to assess CAR-T therapies in 3D complex preclinical models of solid tumours. Here, we present a novel microfluidic immunoassay for the evaluation of CAR-T cell cytotoxicity and targeting specificity on 3D spheroids containing cancer cells and stromal cells. Monitoring the interaction between CAR-T cells and spheroid co-cultures, we show that CAR-T cells home towards target-expressing cancer cells and elicit a cytotoxic effect. Testing CAR-T cells in combination therapies, we show that CAR-T cell cytotoxicity is enhanced with anti-PD-L1 therapy and carboplatin chemotherapy. We propose this proof-of-concept microfluidic immunoassay as a material-saving, pre-clinical screening tool for quantification of cell therapy efficacy.