To functionally clarify whether IL-11-mediated Stat3 signaling contributes to the formation and progression of gastric tumors, we generated KPP;IL11ra+/− mice because we had previously shown that monoallelic ablation of the IL-11Ra receptor subunit impaired the formation of signaling-competent IL-11:IL-11Ra:gp130 receptor complexes.21 Here, STAT3 is linked to gastric neoplasm.