The logic behind the approach, which the team calls the Macrophage Transducer Concept, draws on the natural biology of macrophages. These immune cells, derived from circulating monocytes, are among the first responders to emerging tumors. In early cancer, they detect factors released by cancer cells and migrate into tumor tissue, where interactions with malignant cells reshape their behavior. Tumor-associated macrophages then secrete molecules that influence inflammation, fibrosis, and the growth of new blood vessels, helping to build and regulate the tumor microenvironment. Crucially, macrophages are exquisitely sensitive to their surroundings and adjust their secretory output in response to diverse stimuli. The researchers hypothesized that this plasticity could be exploited: expose macrophages to a sample containing unknown cancer-derived factors, and the cells will translate that complex input into a reproducible profile of cytokines that can be measured with standard laboratory assays.

To test the idea, the team built a microfluidic device from polydimethylsiloxane, a transparent silicone widely used in lab-on-a-chip systems. The fabrication followed established soft-lithography techniques: a mold of the microchannel was patterned in SU-8 photoresist on a glass substrate using ultraviolet photolithography, liquid PDMS was poured over the mold and cured, and the resulting structure was plasma-bonded to glass. The finished channel is 500 micrometers wide and 200 micrometers deep, arranged in a serpentine pattern that packs 1.3 square centimeters of cell culture area into a compact footprint. A syringe pump drives fluid through the channel while a hot plate holds the device at body temperature, creating a controlled perfusion environment in which cells experience continuous, defined flow rather than sitting in a static pool of medium.

Before exposing the cells to cancer-derived factors, the researchers needed to understand how flow itself affects macrophage behavior. They cultured human monocyte-derived macrophages, prepared from blood donated by healthy volunteers, inside the device and perfused it with medium containing lipopolysaccharide, a bacterial endotoxin that strongly triggers tumor necrosis factor-alpha secretion. At flow rates of 1 and 2 microliters per minute, TNF-alpha output was high; at 5 microliters per minute it dropped significantly. Computational fluid dynamics using the finite volume method in ANSYS Fluent explained why. Simulating the velocity field ten micrometers above the channel floor—the height of the cells—revealed that the area of the channel experiencing flow velocities below 0.1 millimeters per second tracked closely with TNF-alpha secretion. Based on these results, the team selected 2 microliters per minute as the standard condition, balancing strong cellular responses with reasonable experimental throughput.

The perfusion format also unlocked something static cultures cannot provide: a time-resolved view of macrophage secretion. When LPS-containing medium was perfused through the device and effluent collected every four hours, TNF-alpha peaked sharply at four hours and then declined rapidly, while interleukin-6 rose to a maximum between four and eight hours and remained relatively stable afterward. In conventional well plates, by contrast, TNF-alpha did not peak until twelve hours and then plateaued, and IL-6 climbed gradually for roughly twenty hours. Because the two formats sample differently—perfusion captures what is secreted during each interval, while static culture accumulates everything up to the collection time—the absolute concentrations cannot be compared directly. But the contrast demonstrates that the microfluidic platform can resolve the onset, peak, and duration of secretory responses, dynamic information that endpoint measurements in well plates simply cannot capture.

With the platform calibrated, the team turned to the central question: do macrophages generate distinct, reproducible response profiles when exposed to different cancer-derived signals? They collected culture supernatants from eight human cancer cell lines representing colon, ovarian, esophageal, kidney, lung, breast, stomach, and liver cancers, and incubated them with macrophages for twenty-four hours. The answer was clearly yes. The types and amounts of factors secreted by the macrophages differed according to which cancer supernatant they had encountered. The colorectal line COLO205 drove elevated TNF-alpha and IL-6 secretion; the ovarian line RMG-1 provoked strong TNF-alpha and CCL2 responses; the kidney cancer line MAMIYA preferentially induced IL-6 and CCL2; and the gastric line MKN45 was characterized by increased vascular endothelial growth factor production. Four readout factors—TNF-alpha, IL-6, CCL2, and VEGF—were chosen to span inflammation, immune regulation, immune cell migration, and angiogenesis.

To visualize these multidimensional patterns, the researchers standardized the cytokine concentrations and generated heatmaps, then applied principal component analysis as an exploratory tool. The analysis suggested that macrophage-derived response profiles carry multidimensional information associated with differences among the cancer supernatants. Notably, when the pre-incubation supernatants were analyzed on their own, they showed one multivariate structure; after macrophage incubation, the spatial organization of samples in principal component space changed and dispersed, consistent with the idea that macrophages do not merely mirror the composition of the input but actively reshape and amplify biologically relevant information within it. The authors are careful to stress that the PCA was exploratory, performed on a limited donor dataset, and was not intended to demonstrate diagnostic classification performance. The goal was to establish whether complex biological information could be transformed into reproducible response profiles at all—not to identify the individual molecules responsible.

The team then confirmed that the concept works under perfusion. When supernatants from COLO205 and HepG2 liver cancer cells—chosen because they produced contrasting TNF-alpha responses in static culture—were flowed through the device, macrophages secreted TNF-alpha in response to COLO205 but not to HepG2, reproducing the static-culture trend. The device also proved economical: it reduced the number of cells required by 65 percent and the solution volume by roughly 10 percent compared with well plates, and TNF-alpha secretion per cell under LPS stimulation tended to be higher in the microfluidic format, measuring 33 percent higher under normalized conditions. The authors caution that the mechanisms behind this difference were not investigated, so any interpretation that the device enhances secretion remains speculative. They also note that integrating an on-chip biosensor, as other groups have done with fluorescence and electrochemical cytokine detection, could further shrink sample volumes and assay times, which are currently limited by the requirements of enzyme-linked immunosorbent assays.

The researchers are equally candid about the study’s limitations, which are substantial. Macrophages are heterogeneous, and although similar qualitative trends appeared across independent donors, the donor cohort was too small to systematically assess variability, and the differentiated cells were not phenotyped with markers such as CD80, CD86, CD163, or CD206. Only four secreted factors were measured, a small slice of the macrophage repertoire, and only two supernatants were tested in the device itself. The cancer-derived factors and signaling pathways driving the distinct responses remain unknown, PDMS surfaces may have adsorbed cytokines, and the culture supernatants used as model inputs differ enormously from real patient blood or serum. Disease specificity is also unresolved, since inflammatory and infectious conditions might produce overlapping macrophage responses, and no blinded validation was performed. Still, as a proof of concept, the work sketches a genuinely novel path for liquid biopsy: rather than fishing for known biomarkers in a sea of unknown signals, future diagnostics might hand complex clinical samples to a living immune sensor and read back the answer in the language of cytokines. Whether that translation proves reliable enough for the clinic will depend on the validation studies that must now follow.

Subject of Research: A microfluidic platform using macrophages as biological transducers to profile responses to cancer-cell-derived factors for potential cancer diagnostics

Article Title: Development of macrophage transducer-based cancer diagnostics: A proof-of-concept microfluidic platform for profiling macrophage responses to cancer-cell-derived factors

Article References: Ide, Y., Yamasaki, K., Ishikawa, S., Saito, Y., Fujiwara, Y., Nakanishi, Y., & Nakashima, Y. (2026). Development of macrophage transducer-based cancer diagnostics: A proof-of-concept microfluidic platform for profiling macrophage responses to cancer-cell-derived factors. Results in Engineering, 32, Article 113534. https://doi.org/10.1016/j.rineng.2026.113534

Image Credits: AI Generated

DOI: Not provided

Keywords: macrophages, microfluidics, cancer diagnostics, liquid biopsy, cytokines, tumor microenvironment, biosensors, TNF-alpha, organ-on-chip, principal component analysis, tumor-associated macrophages, proof of concept