Harnessing 3D in vitro systems to model immune responses to solid tumours: a step towards improving and creating personalized immunotherapies

In vitro 3D models are advanced biological tools that have been established to overcome the shortcomings of oversimplified 2D cultures and mouse models. Various in vitro 3D immuno-oncology models have been developed to mimic and recapitulate the cancer–immunity cycle, evaluate immunotherapy regimens, and explore options for optimizing current immunotherapies, including for individual patient tumours. Here, we review recent developments in this field. We focus, first, on the limitations of existing immunotherapies for solid tumours, secondly, on how in vitro 3D immuno-oncology models are established using various technologies — including scaffolds, organoids, microfluidics and 3D bioprinting — and thirdly, on the applications of these 3D models for comprehending the cancer–immunity cycle as well as for assessing and improving immunotherapies for solid tumours. This Review describes recent advances in the field of 3D in vitro modelling technologies that enable a better understanding of immune cell and tumour cell interactions in the tumour microenvironment. The authors explain how such systems can be used to assess the efficacy of novel immunotherapies, including personalized immunotherapies, for patients with cancer.