Abstract 5875: Schlafen 11 (SLFN11) induces lethal S-phase arrest in response to DNA damage: A novel mechanism of how cancer cells are killed by DNA damaging agents

Abstract

Abstract The putative DNA/RNA helicase, Schlafen 11 (SLFN11), is a recently discovered determinant of sensitivity to DNA damaging agents such as platinums, topoisomerase I and II inhibitors (camptothecins, etoposide, doxorubicin), cisplatin, gemcitabine (1-3) and PARP inhibitors (olaparib, talazoparib) (4). Because SLFN11 expression is suppressed in ~45% cancer cell lines, SLFN11 inactivation is potentially one of the most prevalent mechanisms of resistance to DNA damaging agents. However, the molecular mechanisms of SLFN11 action in the DNA damage response have not been solved. Using isogenic cell lines of SLFN11-knockout and SLFN11-overexpression, we will show that SLFN11 binds to chromatin in response to camptothecin within 2 hours. ChIP-seq analysis reveals that SLFN11 preferentially binds to replication origins under camptothecin treatment. We identify two helicases DHX9 and MCM3, which are involved in replication and origin firing, as binding partners of SLFN11 by IP-MS analysis. Cell cycle analyses revealed that SLFN11 inhibits replication in response to camptothecin, which irreversibly lasts until apoptosis is exerted. Notably, the S-phase arrest by SLFN11 is independent of ATR-mediated S-phase checkpoint. Unscheduled origin firing by ATR inhibition under camptothecin treatment is suppressed in the presence of SLFN11. Hence, SLFN11 enforces irreversible S-phase arrest in damaged cells possibly by inhibiting dormant origin firing and inactivating the MCM helicase in conjunction with DXH9. We conclude that the irreversible S-phase arrest by SLFN11 leads to cell death in response to DNA damaging agents, which is a novel mechanism of how cancer cells are killed by DNA damaging agents. 1. Sousa FG, Matuo R, Tang SW, Rajapakse VN, Luna A, Sander C, et al. Alterations of DNA repair genes in the NCI-60 cell lines and their predictive value for anticancer drug activity. DNA Repair (Amst) 2015;28:107-15. 2. Zoppoli G, Regairaz M, Leo E, Reinhold WC, Varma S, Ballestrero A, et al. Putative DNA/RNA helicase Schlafen-11 (SLFN11) sensitizes cancer cells to DNA-damaging agents. Proc Natl Acad Sci U S A 2012;109(37):15030-5. 3. Barretina J, Caponigro G, Stransky N, Venkatesan K, Margolin AA, Kim S, et al. The Cancer Cell Line Encyclopedia enables predictive modelling of anticancer drug sensitivity. Nature 2012;483(7391):603-307. 4. Murai J, Feng Y, Yu GK, Ru Y, Tang SW, Shen Y, et al. Resistance to PARP inhibitors by SLFN11 inactivation can be overcome by ATR inhibition. Oncotarget 2016. Citation Format: Junko Murai, Yves Pommier. Schlafen 11 (SLFN11) induces lethal S-phase arrest in response to DNA damage: A novel mechanism of how cancer cells are killed by DNA damaging agents [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5875. doi:10.1158/1538-7445.AM2017-5875