In the context of solid tumor, the tumor cells are often softened relative to their non-malignant counterparts. How softening of tumor cells influences immune surveillance, especially functionality of natural killer (NK) cells and T cells, is not well understood. Regarding NK cells, we found that NK cell killing efficiency in 3D was impaired against softened tumor cells, while it is enhanced against stiffened tumor cells. Furthermore, we found that the durations required for NK cell killing and detachment are significantly shortened for stiffened tumor cells. Additionally, we identified PIEZO1 as the predominantly mechanosensitive ion channel expressed in NK cells. We observed that perturbation of PIEZO1 abolished stiffness-dependent NK cell responsiveness, significantly impaired the killing efficiency of NK cells in 3D, and substantially reduced NK cell infiltration into 3D collagen matrices. Conversely, PIEZO1 activation enhances NK killing efficiency as well as infiltration. Regarding T cells, we found that T cell polarization, characterized by MTOC reorientation towards the T cell/tumor cell contact site, was impaired by softening of tumor cells. This stiffness-regulated T cell functionality was mediated by Piezo1, the predominantly expressed mechanosensitive channels in T cells. Piezo1 regulates the Ca2+ influx rate to govern MTOC reorientation, suggestively via modulating the formation of dynein ring structures at the contact site. Our findings highlight the crucial role of PIEZO1-mediated mechanosensing in functionality of both NK and T cells. These findings provide valuable insights into the intricate mechanisms governing immune cell responses and identify potential targets for enhancing immunotherapeutic approaches.
