Epigenetic silencing schlafen-11 sensitizes esophageal cancer to ATM inhibitor

BACKGROUND Targeting DNA damage response (DDR) pathway is a cutting-edge strategy. It has been reported that Schlafen-11 (SLFN11) contributes to increase chemosensitivity by participating in DDR. However, the detailed mechanism is unclear. AIM To investigate the role of SLFN11 in DDR and the application of synthetic lethal in esophageal cancer with SLFN11 defects. METHODS To reach the purpose, eight esophageal squamous carcinoma cell lines, 142 esophageal dysplasia (ED) and 1007 primary esophageal squamous cell carcinoma (ESCC) samples and various techniques were utilized, including methylation-specific polymerase chain reaction, CRISPR/Cas9 technique, Western blot, colony formation assay, and xenograft mouse model. RESULTS Methylation of SLFN11 was exhibited in 9.15% of (13/142) ED and 25.62% of primary (258/1007) ESCC cases, and its expression was regulated by promoter region methylation. SLFN11 methylation was significantly associated with tumor differentiation and tumor size (both P < 0.05). However, no significant associations were observed between promoter region methylation and age, gender, smoking, alcohol consumption, TNM stage, or lymph node metastasis. Utilizing DNA damaged model induced by low dose cisplatin, SLFN11 was found to activate non-homologous end-joining and ATR/CHK1 signaling pathways, while inhibiting the ATM/CHK2 signaling pathway. Epigenetic silencing of SLFN11 was found to sensitize the ESCC cells to ATM inhibitor (AZD0156), both in vitro and in vivo. CONCLUSION SLFN11 is frequently methylated in human ESCC. Methylation of SLFN11 is sensitive marker of ATM inhibitor in ESCC.