It is worth noting that excessive intratumoral cGAMP can induce T- and B-cell apoptosis21,22, upregulate the expression of immunosuppressive molecules (such as PD-L1 and IDO1)2,20, and promote the proliferation of tumor-infiltrating regulatory T cells, hence compromising the overall antitumor immunity64,65. Here, IDO1 is linked to neoplasm.