Sequences encoding G4s are enriched in regulatory regions consistent with roles in transcription and RNA regulation (Huppert and Balasubramanian, 2007; Huppert, 2008), and their over-representation in oncogene promoters, such as MYC, KRAS and KIT, suggests that they are important in cancer and are potential therapeutic targets (reviewed in Balasubramanian et al., 2011). This evidence concerns the gene MYC and cancer.