Intriguingly defective NOTCH signalling has recently been shown to drive clonal expansions of P53 mutant cells (Alcolea et al. 2014), raising the possibility that HES5 silencing early in prostate tumourogenesis might drive clonal expansions and contribute to the ‘field effect’ observed in prostate tumours (Bostwick et al. 1998, Hanson et al. 2006, Mehrotra et al. 2008). This evidence concerns the gene HES5 and prostate neoplasm.