Persister cancer cells are characterized by H4K20me3 heterochromatin that defines a low inflammatory profile

Anti-cancer therapies may induce proliferative arrest in cancer cells in the form of senescence or drug-tolerant persistency, the latter being a reversible arrest with similarities to embryonic diapause. Here, we use mTOR/PI3K inhibition to develop and characterize a model of persistency/diapause-like arrest in human cancer cells of various origins. We show that persister and senescent cancer cells share an expanded lysosomal compartment and hypersensitivity to BCL-XL inhibition. However, persister cells do not exhibit other features of senescence, such as the loss of Lamin B1, senescence-associated b-galactosidase activity, and an inflammatory phenotype. Compared to senescent cells, persister cells have a profoundly diminished senescence-associated secretory phenotype (SASP), low activation of interferon signaling pathways and lack upregulation of MHC-I presentation. Based on a genome-wide CRISPR/Cas9 screen performed in diapause mouse embryonic stem cells (mESC), we discover that persister human cancer cells are hypersensitive to the inhibition of one-carbon metabolism. This finding led us to uncover that the repressive heterochromatic mark H4K20me3 is enriched at promoters of SASP and interferon response genes in persister cells, but not in senescent cells. Collectively, we define novel features and vulnerabilities of persister cancer cells and we provide insight into the epigenetic mechanisms underlying their low inflammatory and immunogenic activity.