CHEK1 and neoplasm: MYCN-amplified tumours express increased levels of genes involved in DNA repair and cell cycle checkpoint pathways [9,12,13,14], including ataxia telangiectasia and rad3-related (ATR), checkpoint kinase 1 (CHK1) and poly(ADP-ribose) polymerase 1/2 (PARP1/2), which have been shown to contribute to tolerance of RS [9,15,16,17,18].