1 Gastric cancer (GC) is the second most lethal cancer in the world and represents a growing number of cancers linked with inflammation. While it is accepted that deregulated interactions between gastric microbes (i.e. H. pylori) and the host innate immune system are likely to be involved in the pathogenesis of gastric inflammation (gastritis) and GC, the identity of oncogenic inflammatory/immune regulators in the host gastric mucosa remains obscure. We report here our investigation into the role of Toll-like receptors (TLRs) during GC by using a spontaneous gastritis/GC mouse model; gp130F/F mice carrying a specific “knock-in” mutation in the interleukin (IL)-6 cytokine family co-receptor gp130 which abolishes a negative feedback mechanism. Among the TLR family, gastric TLR2 expression was significantly upregulated in the tumours of mice, and genetic or therapeutic blockade of TLR2 in gp130F/F mice severely reduced the gastric tumour mass by 50%. However, unexpectedly, the genetic ablation of TLR2 had no effect on reducing the numbers and activation status of immune cells in the stomachs of gp130F/F mice. Furthermore, bone marrow reconstitution experiments suggested a non-essential role for TLR2 in innate immune cells. Although the TLR2-driven inflammatory response from gastric epithelial (tumour) cells from gp130F/F mice was unchanged, immunohistochemical analyses revealed that gp130F/F mice lacking TLR2 had increased TUNEL-positive apoptotic cells and reduced PCNA-positive cells in the gastric mucosal epithelium, thus implicating a role for TLR2 in gastric epithelial cell proliferation and survival. Consistent with our mouse data, we identified that activating TLR2 using synthetic lipopeptides in human gastric epithelial cells promoted cell proliferation via multiple signaling pathways. Collectively, our data depict an unexpected role for TLR2 in gastric tumourigenesis independent of inflammation, whereby over-expression of TLR2 promotes gastric epithelial cell growth.