Köksal et al. show that radiotherapy boosts the proliferation and differentiation of intratumoral CD8+ T cells, including stem-like TCF-1+ cells, which are key to the early immunological and therapeutic response.

Using a mouse tumor model with inducible cGAS expression, Herbst et al. show that cancer-cell-derived cGAMP triggers a sustained type I interferon response, enhancing CD8+ T cell-dependent tumor restriction. However, STING-expressing CD8+ T cells exhibit reduced proliferation and survival. Thus, STING signaling acts as a checkpoint balancing anti-tumor immunity.