Applying microfluidic technology to interpret the tumor immune microenvironment and cancer immunotherapy

In the past decade, cancer immunotherapy has emerged as a transformative treatment modality for diverse malignancies. Although impressive clinical efficacy has been demonstrated in some cancer patients, most patients respond poorly to immunotherapies. The complicated architecture and cellular composition of the tumor immune microenvironment (TIME) have substantial roles in the clinical outcomes of immunotherapies. Therefore, employing optimal <i>in vitro</i> models recapitulating the <i>in vivo</i> TIME characteristics is particularly important for interpreting the dynamic complexity of the TIME, evaluating drug efficacy, and developing novel immunotherapeutics. In recent years, microfluidic technology has been shown to be a valuable tool for mimicking dynamic crosstalk among the TIME <i>in vitro</i> through the manipulation of microscale fluids in an integrated device. Cellular behaviors, function and signal transduction, and tumor-immune interactions can be monitored in real time and analyzed in microfluidic chips by combining visualization technologies. Numerous recent studies have shown how to design and fabricate microfluidic chips for reproducing the complex three-dimensional architecture and dynamic changes in the TIME. This review comprehensively examines the application of innovative microfluidic technology in the field of cancer immunology research, focusing on interpreting dynamic crosstalk inside the TIME from bulk-cell to single-cell analyses, evaluating the efficacy of novel immunotherapies and preparing immunotherapeutic agents, and analyzes current limitations. This work aimed to propose a translational roadmap for leveraging microfluidics in elucidating mechanisms, biomarker discovery, high-throughput drug screening, and personalized immunotherapy development.