Abstract 3736: Schlafen 11 (SLFN11) blocks RNA synthesis upon replicative damage, a novel mechanism for killing cancer cells in response to DNA damaging agents

Abstract

Abstract The putative DNA/RNA helicase, SLFN11, is a recently discovered determinant of response to DNA damaging agents including topoisomerase inhibitors (camptothecin, irinotecan, topotecan, doxorubicin and etoposide) and cisplatin. SLFN11 is inactivated in approximately 40% of cancer cell lines (NCI-60 and CCLE). Until now, the molecular mechanisms of SLFN11 action in response to DNA damage have been unknown. Using isogenic SLFN11-knockout cells as well as SLFN11-overexpressing cells, we will show that SLFN11 irreversibly arrests cells in S-phase without cell cycle recovery under camptothecin treatment, whereas SLFN11-negative cells continue cell cycle progression. Notably, the action of SLFN11 is independent of ATR-mediated S-phase checkpoint. Co-immunostaining of 5-Ethynyl Uridine (EU) and gamma-H2AX revealed that SLFN11 blocks RNA synthesis upon replicative damage. Comprehensive analysis of cell cycle genes revealed that genes that drive S-phase progression are selectively turned-off in SLFN11-positive cells, whereas p53-dependent genes remain induced by camptothecin. Accordingly, critical proteins for S-phase progression such as cyclin A, cyclin B, CDK1 and CDK2 were suppressed in SLFN11-positive but not in SLFN11-negative cells, which causality links SLFN11-mediated S-phase arrest in camptothecin-treated cells with inactivation of cell cycle-driving pathways. This mechanism is supported by the fact that the CDK inhibitor roscovitine recapitulates the S-phase arrest even in SLFN11-deficient cells. Finally, by contrast to normal SLFN11, overexpression of SLFN11 helicase-dead mutant failed to block RNA synthesis and to kill camptothecin-treated cells, indicating that the helicase activity of SLFN11 is necessary for its RNA synthesis regulatory function. Our study reveals a novel cell cycle regulation mechanism by SLFN11 that links DNA damage and transcriptional responses in cancer cells with replicative DNA damage. Citation Format: Junko Murai, Sai-wen Tang, Yves Pommier. Schlafen 11 (SLFN11) blocks RNA synthesis upon replicative damage, a novel mechanism for killing cancer cells in response to DNA damaging agents. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3736.