RNA-seq of effector (CD43+) CD8+ T cells, CD45+ hematopoietic cells and CD45- tumor/stromal cells from mice bearing bilateral AT-3 tumors following radio-immunotherapy of which one tumor was irradiated

Radiotherapy (RT) destroys tumor cells, which may lead to release of antigens and immune-activating signals. In this way, RT may act as an in situ vaccine and kick-start a T-cell response against the tumor. Immunotherapy enhances tumor-specific T-cell responses. Combination of radiotherapy and immunotherapy (radio-immunotherapy (RIT)) can therefore be expected to synergize in inducing and sustaining systemic anti-tumor T-cell responses. However, in the clinic, systemic combined responses between radiotherapy and immunotherapy are rarely observed, as the effect of RIT combinations on 'abscopal' tumors outside the radiotherapy field are not (yet) greater than the effect of immunotherapy alone. In order to define potential bottlenecks in the tumor micro-environment that impede CD8 T cell activity, we harvested irradiated and non-irradiated tumors from the same mice that were treated with RIT (10 Gy RT, anti-CD137 and anti-PD1). From these tumors, effector (CD43+) CD8 T cells, 'other' hematopoietic (CD45+) cells and tumor/stromal (CD45-) were sorted and RNA sequencing was performed to identify differences between these cell populations in the irradiated and non-irradiated tumors that could explain the lack of T cell activity in the non-irradiated tumor.