TP53 and cancer: Salmonella has particular promise as a cancer therapeutic because it can be manipulated to target quiescent, diffusion-limited regions in solid tumours (Kasinskas and Forbes, 2007) that are p53 deficient (Yu et al, 2002) and resistant to chemotherapeutics and radiation therapies (Minchinton and Tannock, 2006; Tredan et al, 2007).