We had previously reported a reduced incidence of intestinal tumours in Gpr35–/– mice in spontaneous CRC (Apcmin) and CAC (AOM/DSS) models.10 Selective deletion of Gpr35 in the intestinal epithelium (ie, in Gpr35fl/fl;Vil-Cre or ‘Gpr35ΔIEC’ mice) was sufficient to reduce tumour incidence in both models.10 In both CRC and CAC, individual tumours in Gpr35–/– mice were strikingly smaller compared with Gpr35+/+ tumours (figure 1A). Here, GPR35 is linked to colorectal carcinoma.