A transformable three-dimensional simulated solid tumor model reveals the widespread killing potential of natural killer cells with controlled lytic granule positioning

Abstract

Abstract Cancer immunotherapy using engineered natural killer (NK) cells has shown great promise. However, the limited spatial complexity of current models hinders the study of NK cells in three-dimensional, solid tumor-like environments. Previously, we found that NK cells converge lytic granules before degranulation. It helps focus the secretion of cytotoxic cargos to the synaptic cleft, thus preventing the non-specific killing of bystander cells. We had speculated that bypassing this protective mechanism and forcing NK cells to degranulate non-directionally may promote broader destruction of cancer cells and eradicate tumor-resident non-triggering cells. To evaluate our hypothesis, we designed a novel strategy for creating complex cellular environments with controlled spatial distribution and intercellular dynamics. Using hydrogel-embedded cells as building blocks, we construct 3D models that arrange multiple cell populations within desired inner structures. Notably, these structures can undergo controlled transformations enabled by hydrogels comprised of thermo-responsive polymers. During this transformation, cells experienced rapid but mechanically gentle translocation to pre-designated positions, allowing us to control cell contacts actively. With these systems (which we have termed TheCOS for Thermal Collapse Of Strata), we observed that controlling NK cell lytic granule positioning at a lytic immune synapse was able to promote bystander cell death within a complex multicellular environment. Using quantitative imaging, we calculated an area of damage attributable to radial degranulation, which suggests a potential benefit to this as a strategy for improving cytotoxic cell therapy for solid tumors.