Abstract B002: DNA methylation protects cancer cells against senescence

Abstract Inhibitors of DNA methylation such as 5-aza-deoxycytidine are widely used in experimental and clinical settings. However, their mechanism of action is such that DNA damage inevitably cooccurs with loss of DNA methylation, making it challenging to discern their respective effects. Here we deconvolute the effects of decreased DNA methylation and DNA damage on cancer cells, by using degron alleles of key DNA methylation regulators (DNMT1 and UHRF1). We report that cancer cells with decreased DNA methylation — but no DNA damage— enter cellular senescence, with G1 arrest, senescence-associated secretory phenotype (SASP) expression, and senescence-associated beta-galactosidase (SA-β-gal) positivity. This senescence is independent of p53 and Rb, but involves p21, which is cytoplasmic and inhibits apoptosis. The suppression of cyclic GMP-AMP synthase (cGAS) alleviates SASP response and lysosomal activity, and this process is independent of stimulator of interferon genes (STING). Xenograft experiments show that tumor cells can be made senescent in vivo by decreasing DNA methylation. These findings reveal the intrinsic effects of loss of DNA methylation in cancer cells and have practical implications for future therapeutic approaches. Citation Format: Xiaoying Chen, Kosuke Yamaguchi, Brianna Rodgers, Delphine Goehrig, David Vindrieux, Xavier Lahaye, Matthieu Nolot, Laure Ferry, Nadine Martin, Pierre Dubus, Fumihito Miura, Takashi Ito, Nicolas Manel, Masato Kanemaki, David Bernard, Pierre-Antoine Defossez. DNA methylation protects cancer cells against senescence [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: DNA Methylation, Clonal Hematopoiesis, and Cancer; 2025 Feb 1-4; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2025;85(3 Suppl):Abstract nr B002.