The progression from two-dimensional cell cultures to three-dimensional (3D) spheroids and those based on hydrogel scaffolds has produced better models of in vivo tissues. However, adding this third dimension creates the need for vasculature and also opens opportunities for adding other aspects of the tumor microenvironment. Meng et al. show that 3D bioprinting can be used to precisely place clusters of tumor cells, stromal cells, and infused vascular cells according to their physiological functions. 3D bioprinting also enabled them to make stimuli-responsive capsules containing growth factors that allowed for spatial and time-controlled distribution of chemical cues. They used these models for preclinical screening to target immunotoxins for their anticancer efficacy.
