a–f, Mice were given one dose of AOM intraperitoneally, followed by one week of 2% DSS in drinking water. a, Tumour development in Il22+/+ and Il22−/− mice. Scale bar, 1 cm. Tumour number (b) (Il22+/+, n = 9; Il22−/−, n = 8; mean ± s.e.m.; P = 0.022) and regional distribution of tumours (c) (Il22+/+, n = 7; Il22−/−, n = 10; mean ± s.e.m.; rectum, P = 0.0007; total, P = 0.0078). d, Body weight as percentage of initial weight (Il22+/+, n = 7; Il22−/−, n = 10; mean ± s.e.m.). e, Expression of the indicated inflammatory and tumour-promoting genes (n = 4–6; mean ± s.e.m.) in colonic mucosa was assessed by qRT–PCR two days after DSS treatment was stopped. f, Expression of the indicated genes was analysed by qRT–PCR within tumours (n = 3–9, mean ± s.e.m.). g, Schematic representation of the CAC treatment in mice with sporadic inactivation of the Il22ra1 gene (Il22ra1fl/fl;Lgr5creERT2/+;R26R-Confetti and Il22ra1fl/+;Lgr5creERT2/+;R26R-Confetti). Data are representative of two biologically independent experiments.