Radiotherapy enhances anticancer CD8 T cell responses by cGAMP transfer through LRRC8A/C volume-regulated anion channels.

The volume-regulated anion channels (VRACs) transport osmolytes, neurotransmitters, and cyclic GMP-AMP (cGAMP) across the cell membrane to regulate cell volume and host defense. We report that the leucine-rich repeat-containing 8A/C (LRRC8A/C) VRAC plays a crucial role in immune responses to radiotherapy and chemotherapy for cancer. VRACs transfer cGAMP from irradiated cancer cells to infiltrating CD4 and CD8 T cells, thus enhancing their effector functions. TCR signaling acts as a physiological signal to open the VRAC pore through phosphatidylinositol 4,5-bisphosphate [PI(4,5)P] and reactive oxygen species (ROS). This allows the rapid uptake of cGAMP and STING activation in mouse and human T cells and induction of interferon-α/β, which up-regulate granzymes and IFN-γ in CD8 T cells. Inhibition of the extracellular hydroxylases CD39 and ENPP1 maintains extracellular ATP and cGAMP, which promotes VRAC-enhanced CD8 T cell anticancer function. Thus, the transfer of cGAMP to T cells by VRACs may be a strategy that can be targeted in future cancer therapies.