CHEK1 and neuroblastoma: To assess if the impaired modulation of activating ligands by the four drugs tested could be related to altered signalling upon drug-mediated genotoxic DNA damage, the status of genes encoding ATM (ATM), ATR (ATR), Chk1 (CHEK1), and Chk2 (CHEK2), the main molecules involved in DDR [38], was analysed in our panel of NB cell lines (Table 1).