We present an easy-to-use, disposable, thermoplastic microwell chip designed to support screening and high-resolution imaging of single-cell behavior in two- and three-dimensional (2D and 3D) cell cultures. We show that the chip has excellent optical properties and provide simple protocols for efficient long-term cell culture of suspension and adherent cells, the latter grown either as monolayers or as hundreds of single, uniformly sized spheroids. We then demonstrate the applicability of the system for single-cell analysis by correlating the dynamic cytotoxic response of single immune cells grown under different metabolic conditions to their intracellular cytolytic load at the end of the assay. Additionally, we illustrate highly multiplex cytotoxicity screening of tumor spheroids in the chip, comparing the effect of environment cues characteristic of the tumor microenvironment on natural killer (NK)-cell-induced killing. Following the functional screening, we perform high-resolution 3D immunofluorescent imaging of infiltrating NK cells within the spheroid volumes.

Ultrasonic standing wave (USW) manipulation is a technology that has been used for separating, sorting, enriching and trapping particles and cells in microfluidic devices including microchannels, microchambers and microwells. One application area is to use the technology for 3D cell cultures on a chip. Such USW-formed 3D cultures have been used for high content screening of tumor spheroids interacting with chemotherapeutic drugs and immune cells. For this purpose, we have developed multiwell microplates designed for high-resolution optimal microscopy. In these microplates, hundreds of tumor spheroids can be formed and shaped by the ultrasound in parallel, followed by high-quality imaging in 3D. However, in our previous work, our USW-based method was not compatible with live cell imaging. Instead, the method was based on active temperature regulation and high-power RF amplification, including bulky and expensive instrumentation. To address this, a novel transducer configuration in combination with an adaptive ultrasonic actuation method has been designed and characterized. The actuation method is applied to a chip-based high-content multi-well screening platform for USW-mediated formation of spheroids. The methodology results in better control of the shape of formed spheroids, eliminates the need for active temperature control and costly RF amplifiers, and enables live-cell microscopy-based imaging during spheroid formation and maturation.

Natural killer (NK) cells can protect from tumor-transformed cells using a fine-tuned machinery of activating and inhibiting receptors. An important activating receptor is Fc gamma receptor IIIa (FcγRIIIA or CD16A), which can trigger antibody-dependent cellular cytotoxicity (ADCC) when recognizing antibody-opsonized target cells. One strategy to boost ADCC responses may be achieved by inhibiting activation-induced shedding of CD16A from the NK cell surface. However, previous preclinical studies have shown contrasting results regarding the effectiveness and limitations of this approach. Here, microchip-based live cell-imaging was used to assess the consequences of CD16A shedding inhibition on the dynamics of NK cell cytotoxicity. The bispecific innate cell engager acimtamig (AFM13) was superior to IgG1 monoclonal antibodies in ADCC and in increasing the fraction of cytotoxic NK cells and serial killers. Under conditions where CD16A shedding was inhibited, acimtamig still triggered ADCC; however, the ability to promote serial killing was reduced and associated with impaired NK cell detachment from target cells. These results demonstrate that CD16A shedding represents an intrinsic feature of NK cell biology that is critical to sustain the antitumoral cytotoxicity of NK cells. This has implications for CD16A engineering of NK cell products and their combination with CD16A-directed NK cell engagers.

The development of new immunotherapeutic drugs and combinatorial strategies requires the implementation of novel methods to test their efficacy in vitro. Here, we present a series of miniaturized in vitro assays to assess immune cell cytotoxic activity, infiltration, and phenotype in renal carcinoma spheroids with the use of a recently developed multichambered microwell chip. We provide protocols for tumor spheroid formation, NK cell culture, fluorescence labelling and imaging of live or fixed cells directly in the chip together with data analysis.

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.

Background Adenosine is a metabolite that suppresses antitumor immune response of T and NK cells via extracellular binding to the two subtypes of adenosine-2 receptors, A(2)ARs. While blockade of the A(2A)ARs subtype effectively rescues lymphocyte activity, with four A(2A)AR antagonists currently in anticancer clinical trials, less is known for the therapeutic potential of the other A(2B)AR blockade within cancer immunotherapy. Recent studies suggest the formation of A(2A)AR/A(2B)AR dimers in tissues that coexpress the two receptor subtypes, where the A(2B)AR plays a dominant role, suggesting it as a promising target for cancer immunotherapy. Methods We report the synthesis and functional evaluation of five potent A(2B)AR antagonists and a dual A(2A)AR/A(2B)AR antagonist. The compounds were designed using previous pharmacological data assisted by modeling studies. Synthesis was developed using multicomponent approaches. Flow cytometry was used to evaluate the phenotype of T and NK cells on A(2B)AR antagonist treatment. Functional activity of T and NK cells was tested in patient-derived tumor spheroid models. Results We provide data for six novel small molecules: five A(2B)AR selective antagonists and a dual A(2A)AR/A(2B)AR antagonist. The growth of patient-derived breast cancer spheroids is prevented when treated with A(2B)AR antagonists. To elucidate if this depends on increased lymphocyte activity, immune cells proliferation, and cytokine production, lymphocyte infiltration was evaluated and compared with the potent A(2A)AR antagonist AZD-4635. We find that A(2B)AR antagonists rescue T and NK cell proliferation, IFN gamma and perforin production, and increase tumor infiltrating lymphocytes infiltration into tumor spheroids without altering the expression of adhesion molecules. Conclusions Our results demonstrate that A(2B)AR is a promising target in immunotherapy, identifying ISAM-R56A as the most potent candidate for A(2B)AR blockade. Inhibition of A(2B)AR signaling restores T cell function and proliferation. Furthermore, A(2B)AR and dual A(2A)AR/A(2B)AR antagonists showed similar or better results than A(2A)AR antagonist AZD-4635 reinforcing the idea of dominant role of the A(2B)AR in the regulation of the immune system.

Here, we present a methodology based on multiplexed fluorescence screening of two-or three-dimensional cell cultures in a newly designed multichambered microwell chip, allowing direct assessment of drug or im-mune cell cytotoxic efficacy. We establish a framework for cell culture, formation of tumor spheroids, fluores-cence labeling, and imaging of fixed or live cells at various magnifications directly in the chip together with data analysis and interpretation. The methodology is demonstrated by drug cytotoxicity screening using ovarian and non-small cell lung cancer cells and by cellular cytotoxicity screening targeting tumor spheroids of renal carcinoma and ovarian carcinoma with natural killer cells from healthy donors. The miniaturized format allowing long-term cell culture, efficient screening, and high-quality imaging of small sample volumes makes this methodology promising for individualized cytotoxicity tests for precision medicine.

Single-cell assays are developed as novel tools for the identification and characterization of individual cell responses. Some methods provide snapshots of the phenotype of the cell, such as flow cytometry and single-cell RNA sequencing, whereas others, almost exclusively microscopy-based, can be used for longitudinal studies of individual cells. In the present study, we developed an easy-to-use, disposable, thermoplastic microwell chip, designed to support screening and high-resolution imaging of single-cell behavior in two-and three-dimensional cell cultures. We confirm its excellent optical properties and provide simple protocols for efficient long-term cell culture of suspension and adherent cells, the latter grown either as monolayers or as hundreds of single, uniformly-sized spheroids. We demonstrate the applicability of the system for single-cell analysis by correlating the dynamic cytotoxic response of single immune cells to their intracellular cytolytic load at the end of the assay. Additionally, we illustrate highly multiplex cytotoxicity screening of tumor spheroids in the chip, comparing the effect of environment cues characteristic of the tumor microenvironment on NK cell-induced killing. Following the functional screening, we perform high-resolution 3D immunofluorescent imaging of infiltrating NK cells within the spheroid volumes.