Cytoplasmic chromatin triggers inflammation in senescence and cancer

Chromatin is traditionally viewed as a nuclear entity that regulates gene expression and silencing1-3. However, we recently discovered the presence of cytoplasmic chromatin fragments that pinch off from intact nuclei of primary cells during senescence(4,5), a form of terminal cell-cycle arrest associated with pro-inflammatory responses6. The functional significance of chromatin in the cytoplasm is unclear. Here we show that cytoplasmic chromatin activates the innate immunity cytosolic DNA-sensing cGAS-STING (cyclic GMP-AMP synthase linked to stimulator of interferon genes) pathway, leading both to short-term inflammation to restrain activated oncogenes and to chronic inflammation that associates with tissue destruction and cancer. The cytoplasmic chromatin-cGAS-STING pathway promotes the senescence-associated secretory phenotype in primary human cells and in mice. Mice deficient in STING show impaired immuno-surveillance of oncogenic RAS and reduced tissue inflammation upon ionizing radiation. Furthermore, this pathway is activated in cancer cells, and correlates with pro-inflammatory gene expression in human cancers. Overall, our findings indicate that genomic DNA serves as a reservoir to initiate a pro-inflammatory pathway in the cytoplasm in senescence and cancer. Targeting the cytoplasmic chromatin-mediated pathway may hold promise in treating inflammation-related disorders.Leukemia & Lymphoma Society; National Institutes of Health (NIH) [K99AG053406]; NIH [P01AG031862, CA078831, P01CA196539]; Glenn Foundation; Ellison Foundation; [1P30AR069589-01]SCI(E)ARTICLE767655