Importantly, PARPis are compatible with ICIs for three reasons: 1) PARPis upregulate PD-L1 expression in cancer cells in vitro and in vivo which is a marker for response to ICIs; 2) PARPis release DNA from cancer cells and induce T cell activation through the release of interferon-γ by the activation of the STING pathway; and 3) PARPis change the tumor microenvironment to activate tumor-infiltrating lymphocytes. Here, STING1 is linked to cancer.