Bioprinting of tumor immune microenvironment for immunotherapy

Accurately simulating the tumor immune microenvironment (TIME), which consists of a tumor, extracellular matrix (ECM), vascular network, and a variety of stromal and immune cells, is crucial for advancing and testing immunotherapies such as checkpoint inhibitors, chimeric antigen receptor-T (CAR-T) cells, and cancer vaccines. Traditional models, such as animal models, are limited by their differences from human immune environments. Bioprinting addresses these limitations by incorporating tumors, immune cells, and vascular cells within an ECM, thereby reflecting the complex interactions, including trafficking, between cancer and immune cells. These models provide better predictive accuracy for human immune responses, reducing translational failures and improving preclinical testing. While bioprinting methods for simulating the tumor microenvironment, where cancer cells form spheroids surrounded by blood vessels, are well reviewed, bioprinting methods for recapitulating the TIME are not as thoroughly explored. This review aims to fill this gap by exploring the development, application, and potential of bioprinted TIME models in enhancing the study and efficacy of immunotherapies, ultimately offering a more realistic and personalized approach to cancer treatment.