Zebularine elevates STING expression and enhances cGAMP cancer immunotherapy in mice

DNA methylation abnormality is closely related to tumor occurrence and development. Chemical inhibitors targeting DNA methyltransferase (DNMTis) have been used in treating cancer. However, the impact of DNMTis on antitumor immu-nity has not been well elucidated. In this study, we show that zebularine (a demethylating agent) treatment of cancer cells led to increased levels of interferon response in a cyclic guano -sine monophosphate-AMP (cGAMP) synthase (cGAS)-and stimulator of interferon genes (STING)-dependent manner. This treatment also specifically sensitized the cGAS-STING pathway in response to DNA stimulation. Incorporation of ze-bularine into genomic DNA caused demethylation and elevated expression of a group of genes, including STING. Without causing DNA damage, zebularine led to accumulation of DNA species in the cytoplasm of treated cells. In syngeneic tu-mor models, administration of zebularine alone reduced tumor burden and extended mice survival. This effect synergized with cGAMP and immune checkpoint blockade therapy. The efficacy of zebularine was abolished in nude mice and in cGAS(-/-) or STING(-/-) mice, indicating its dependency on host immunity. Analysis of tumor cells indicates upregulation of interferon-stimulated genes (ISGs) following zebularine administration. Zebularine promoted infiltration of CD8 T cells and natural killer (NK) cells into tumor and therefore suppressed tumor growth. This study unveils the role of zebu-larine in sensitizing the cGAS-STING pathway to promote anti-tumor immunity and provides the foundation for further therapeutic development.

Automated summary

DNA methylation abnormality is closely related to tumor occurrence and development. Chemical inhibitors targeting DNA methyltransferase (DNMTis) have been used in treating cancer. The study shows that zebularine treatment of cancer cells led to increased levels of interferon response in a cGAMP synthase (cGAS) and stimulator of interferon genes (STING) dependent manner. This treatment sensitized the cGAS-STING pathway in response to DNA stimulation and promoted anti-tumor immunity.