CHEK1 and neoplasm: When Chk1 and Ras/RAF/MEK/ERK pathway inhibitors were combined, anti-tumour efficacy and increased DNA damage was observed suggesting a functional role of the Ras/RAF/MEK/ERK signalling in the regulation of Chk1 inhibitor-mediated DNA damage (Dai et al, 2008; Pei et al, 2011).