Neutrophils are the most abundant immune cells in human blood, representing about 50% to 70% of circulating immune cells, but their short life span, fragility and functional heterogeneity make them difficult to study outside the body. They normally respond rapidly to infection by migrating from the circulation into affected tissue, where they can phagocytose pathogens, produce reactive oxygen species, release granule proteins and form neutrophil extracellular traps, or NETs. In tumors, however, these same functions can have different consequences. Human tumor analyses have associated abundant circulating neutrophils and tumor-associated neutrophils with poor outcomes, including a gene-expression analysis of approximately 18,000 tumors across 30 cancer types in which neutrophils were linked to the worst survival among the immune populations assessed. Other studies show that carefully controlled neutrophils can directly kill tumor cells, present antigens, support T-cell responses or cooperate with natural killer cells.

The apparent contradiction is not evidence that one universal neutrophil population is beneficial or harmful. Single-cell studies reviewed in the article identify at least ten transcriptionally distinct neutrophil states across 17 cancer types, including interferon-responsive, angiogenic, immunosuppressive, quiescent and antigen-presenting programs. Local tumor conditions can also override a cell’s maturation state: one 2024 mouse study reported that neutrophils entering a tumor converged on a glycolytic, hypoxic state associated with pro-angiogenic activity. This plasticity makes context essential. It also creates a technical problem, because conventional monolayers and transwell cultures expose cells to a much narrower set of chemical, mechanical and spatial signals than they encounter in a tumor, while mouse models contain major species differences. Human blood is neutrophil-rich, whereas laboratory mouse blood is lymphocyte-rich; mice also lack direct counterparts of human CXCR1 and IL-8, and human neutrophils express FcαRI, which is absent in mice.

Three-dimensional tumor models address part of this problem. Spheroids made from immortalized cancer cell lines form dense aggregates with layers of proliferating, quiescent and necrotic cells, along with gradients of nutrients, oxygen and metabolites. They are relatively easy to produce and suitable for higher-throughput experiments, although they do not retain the full cellular and genetic diversity of a patient’s tumor. Organoids are self-organizing structures grown from primary biopsy or resection material, commonly within collagen or Matrigel-like hydrogels. Because they preserve more of the original tumor’s heterogeneity and genetic programming, they offer a closer approximation of clinical tumors but require more demanding maintenance. In reviewed spheroid studies, primary human neutrophils increased the growth of A549 lung tumor spheroids, while CXCR2 inhibition reduced their infiltration. In colorectal and head-and-neck spheroid systems, NETs physically obstructed T cells and natural killer cells, and treatment with DNase I restored their cytotoxic activity.

Patient-derived organoids have likewise exposed mechanisms of neutrophil reprogramming. In a colorectal cancer model, KRAS-mutant tumor organoids prolonged neutrophil survival and polarized the cells toward a tumor-promoting, T-cell-suppressing phenotype. A separate study used organoids derived from liver metastases in colorectal cancer patients, together with autologous neutrophils and CD8 T cells, to investigate AKR1B10. Combining the AKR1B10 inhibitor epalrestat with anti-PD-L1 therapy suppressed organoid growth more than either treatment alone. These are preclinical organoid observations, not clinical efficacy findings, but they demonstrate that MPS can test tumor-specific mechanisms and combination strategies with patient material. Other experiments found that CAR-neutrophils generated from human pluripotent stem cells infiltrated glioblastoma spheroids and killed tumor cells, including under hypoxic conditions, while nanoparticle-loaded CAR-neutrophils produced greater cytotoxicity than unloaded cells or nanoparticles alone.

Microfluidic devices add spatial control and dynamic flow to these applications. Compartments, porous membranes, micropillars and collagen gels can be arranged to determine whether neutrophils and cancer cells are separated, allowed to contact one another or recruited from a perfused vascular channel. Live imaging then records migration, cluster formation, reactive oxygen species, NET release, tumor invasion and cell death with single-cell resolution. One cervical cancer-on-a-chip system reproduced recruitment of patient-derived neutrophils into a tumor chamber and their production of NETs. A prostate model found that cancer-associated fibroblasts limited neutrophil infiltration relative to fibroblasts from benign prostate tissue, suggesting patient-specific regulation of recruitment. In a pancreatic cancer device, the CXCR2 antagonist AZD-5069 reduced neutrophil forward migration, velocity, directionality and displacement, while another device revealed that anti-tumor neutrophils made longer contacts with tumor spheroids and penetrated them more deeply than pro-tumor neutrophils.

The same platforms capture opposing effects that may be difficult to interpret in animals. In a microfluidic model of breast and head-and-neck cancers, direct contact with tumor cells triggered neutrophil migration, swarming, reactive oxygen species and NET release, yet the neutrophils also restricted tumor migration and invasion and induced apoptosis. In an ovarian cancer model, NETs instead promoted collective invasion into the surrounding matrix, and blocking their formation attenuated invasion. Vascular chips have likewise demonstrated that inflamed neutrophils can aggregate with circulating tumor cells, create localized IL-8 signaling and weaken endothelial barriers, facilitating extravasation. In a model combining circulating neutrophils, platelets and breast cancer cells, platelet integrin β3 inhibition reduced extravasation. In a separate bone-metastasis model, neutrophils that left the circulation increased cancer-cell death. These studies involved different experimental contexts and cell populations; together, they reinforce that the net effect of neutrophils depends on location, phenotype and neighboring cells rather than on a simple pro- or anti-tumor label.

Microphysiological systems also offer a route toward measuring what researchers call a neutrophil “behaviorome”: the complete set of measurable cellular behaviors over time. Cancer models reviewed in the article have quantified migration speed, displacement, directionality, contact frequency and duration, infiltration depth, swarming, NET formation, reactive oxygen species and tumor killing. Additional behaviors, including reverse migration and pausing, have been measured in non-cancer neutrophil systems and are proposed for future cancer studies, not established results in the reviewed cancer models. A larger validation gap remains because many studies still rely mainly on endpoint staining rather than continuous imaging. The review proposes combining behavior measurements with transcriptomics, proteomics, metabolomics and spatial analysis to identify molecular programs underlying observed behavior. Methods developed for T cells and natural killer cells provide precedents, including behavior-guided transcriptomics, single-cell sequencing of cells retrieved from chips, and spatial profiling of solid tumors. Neutrophil-specific work in this area remains preliminary, so the proposed combination is a research direction rather than an established testing standard.

Patient-derived systems could eventually support individualized therapy selection, but most neutrophil MPS studies have used healthy-donor blood or HL-60 cells differentiated into a neutrophil-like state rather than matching neutrophils and tumor cells from the same patient. Microfluidics can test several treatments with small clinical samples, and commercially available platforms can place 32 to 128 chips within the footprint of standard 96- or 384-well plates. Such systems may also help evaluate safety. Because systemic neutrophil manipulation could impair infection control or wound healing, a proposed tumor-and-tissue model could test whether CXCR2 blockade suppresses tumor recruitment while preserving responses elsewhere. Multi-organ models could similarly track engineered CAR-neutrophil biodistribution, off-target cytotoxicity and cytokine release across linked tissues. These proposed uses require further validation, and regulatory milestones described in the review for organ chips and other new approach methodologies do not establish clinical effectiveness for neutrophil-based cancer immunotherapy.

The review therefore positions microphysiological systems as a complementary bridge between animal experiments, conventional cell culture and clinical research, not as a replacement for either. Their strongest current contribution is to provide controlled, human-cell platforms in which neutrophil behavior can be observed in real time and linked to tumor-specific mechanisms and candidate interventions. Spheroids and organoids have demonstrated pro-tumor and anti-tumor effects in separate experimental settings; microfluidic systems add flow, compartmentalization and quantitative tracking of those interactions. Continued standardization of cell sources, isolation methods, culture conditions, flow, matrix composition and image analysis will be essential if findings from different laboratories are to be compared. The central translational promise is that these models may expose which forms of neutrophil manipulation work in human cellular systems, reveal their limitations and guide better-designed clinical studies without claiming benefits that have not yet been demonstrated in patients.

Subject of Research: Human microphysiological models for studying neutrophil–tumor interactions in cancer immunotherapy

Article Title: Leveraging Microphysiological Systems to Facilitate Neutrophil‐Based Cancer Immunotherapy

Article References: Shao, S., Diehl, M. I., & Jones, C. N. (2026). Leveraging Microphysiological Systems to Facilitate Neutrophil‐Based Cancer Immunotherapy. Advanced Science, 13(58), Article e77572. https://doi.org/10.1002/advs.77572

Image Credits: AI Generated

DOI: 10.1002/advs.77572

Keywords: microphysiological systems, neutrophil immunology, cancer immunotherapy, organ-on-a-chip, tumor organoids, tumor spheroids, neutrophil extracellular traps, microfluidics, human tumor models, CAR neutrophils, Leveraging, Microphysiological