The profound reduction in tumour growth observed in both spontaneous and inflammation-induced intestinal tumour models on macrophage-selective deletion of Gpr35 identifies a novel major mechanism, and vividly highlights the critical role of myeloid cells in tumour development.18 We had previously reported that intestinal epithelial cell-specific deletion of Gpr35 reduces intestinal tumour incidence and reduces epithelial cell proliferation.10 Our discovery here adds a major separate tumour-promoting mechanism of GPR35 that originates from TAMs and neutrophils. This evidence concerns the gene GPR35 and intestinal neoplasm.