Etoposide eto

Colorectal cancer (CRC) cell lines (HCT116, HT29, WIDR and T87), lung cancer cell lines (A549, H460, H1299 and H1975), a human bronchial epithelial cell line (BEAS-2B), human glioma cell lines (U251, U373 and U87), human hepatoma cell lines (HuH7, 7721, HepG2) and human embryonic kidney 293 cells (HEK 293T) were all purchased from the Chinese Academy of Sciences Cell Bank (Shanghai, China). The culture conditions used in this study are shown in Supplementary Table S1. High glucose Dulbecco’s modified Eagle’s medium (DMEM) and RPMI-1640 medium were supplied by HyClone (Thermo Fisher, USA). All culture media were supplemented with 10% fetal bovine serum (Gibco, Thermo Fisher), 100 U/mL penicillin and 100 µg/mL phytomycin (Gibco, Thermo Fisher). All cultures were maintained at 37 °C and 5% CO₂. For induction of DNA damage, cells were treated with camptothecin (CPT, 1 µM, Selleck) for 1 h, etoposide (ETO, 100 μg/mL, Selleck) for 4 h, or γ-irradiation. ATM inhibitor (ATMi, KU-55933), ATR inhibitor (ATRi, VE-821) and DNA-PK inhibitor (DNA-PKi, NU7441) were purchased from Selleck. During DNA damage induction by ionizing radiation (IR), CPT or ETO, the corresponding inhibitors were maintained in complete medium continuously unless indicated.

Valproic acid (VPA; Sigma-Aldrich, St. Louis, MO, USA; Cat. #P4543-10G) was dissolved in phosphate-buffered saline (PBS; Hyclone Laboratories Inc., Logan, UT, USA; Cat. #SH30256.02) into 300 mM and stored at −20 °C. Etoposide (ETO; Selleckchem, Houston, TX, USA; Cat. #S1225) was dissolved in dimethyl sulfoxide (DMSO; Sigma-Aldrich, St. Louis, MO, USA; Cat. # D2650-100 mL) into 100 mM and stored at −20 °C. Both VPA and ETO were diluted into desired working concentrations in culture medium prior to experiments.