The JNK pathway is unusual in having both pro-proliferation and pro-apoptotic roles, and was initially thought to be activated only where wild-type tissue abuts clones mutant for neoplastic tumour suppressor genes, promoting apoptosis within mutant cells and their elimination from the tissue (Brumby and Richardson, 2003; Igaki et al., 2006, 2009; Ohsawa et al., 2011; Uhlirova et al., 2005). This evidence concerns the gene MAPK8 and neoplasm.