Thymidine rescues ATR kinase inhibition induced deoxyuridine contamination in genomic DNA, cell death, and Type 1 interferon expression

Abstract

ATR kinase is a central regulator of the DNA damage response (DDR) and cell cycle checkpoints. However, little is known about the role of ATR in the cell cycle and the impact of DDR inhibitors in immune cells in the absence of DNA damage. We previously showed that the ATR inhibitor AZD6738 (ATRi) combines with radiation to generate delayed, CD8+ T cell-dependent antitumor responses in mouse models of cancer. Here, we show that ATRi induces untimely CDK1 activity during S phase in CD8+ T cells and this induces origin firing and simultaneous degradation of dNTP synthesis and salvage enzymes. These pleiotropic effects of ATRi in proliferating CD8+ T cells induce deoxyuridine contamination in genomic DNA, R loops, RNA-DNA polymerase collisions, and death. Remarkably, thymidine significantly rescues ATRi-induced CD8+ T cell death. Our data identifies critical considerations for the design of clinical ATRi regimens with genotoxic chemo- and radiation and immunotherapies.

S Phase Duration Is Determined by Local Rate and Global Organization of Replication

“…For example, the frog cell line A-6 has an S phase of 13.8 h at 28 • C [46], and the Drosophila Kc cell line requires 10 h, a stark contrast with the earlier rapid cycles. The fastest somatic mammalian cells which we have seen reported are activated CD8+ T cells who have S phases of under 5 h ex vivo [47] and in vivo CD8+ T cells can complete their whole cell cycle in under 2 h [48]. The vast majority of mammalian S phases are around 8-10 h (see Table S1).…”