Synthetic essentiality of thymine DNA glycosylase in p53-deficient cancer [RNA-seq]

Thymine DNA Glycosylase (TDG) is a versatile protein involved in DNA mismatch repair, DNA demethylation, and transcriptional regulation. Here, we identify TDG as a synthetic essential effector in p53-deficient tumours. We found that deletion of TDG inhibits cell proliferation specifically in p53-deficient cancer cells. Using a genetically engineered mouse model of lung adenocarcinoma (LUAD), we demonstrate that depletion of TDG suppresses tumour growth in the p53-deficient context. Notably, A novel and selective inhibitor developed to disrupt the DNA binding activity of TDG exhibits therapeutic efficacy against p53-deficient tumours in both cellular and xenograft models. Mechanistically, TDG coordinates with p53 to orchestrate the transcription of RNA helicase DHX9, which functions to eliminate dsRNA. Depletion of TDG in p53-deficient cells results in the downregulation of DHX9 and aberrant cytoplasmic double-strand (dsRNA) accumulation derived from Alu elements, subsequently activating the RIG-I/MDA5-MAVS mediated antiviral response. Moreover, single-cell RNA-sequencing analysis revealed the depletion of TDG in p53-deficient tumours facilitates the recruitment of tumour-infiltrating lymphocytes. We observed that TDG inhibition combined with immune checkpoint blockade (ICB) achieved a strong synergistic anti-tumour effect in p53-deficient tumours. This study highlights the function of TDG in maintaining p53-deficient tumour growth and provides an alternative therapeutic target for p53-deficient cancers.