By employing sST2-expressing pancreatic cancer Panc02 cells in an orthotopic implantation mouse model, we report here that, contrary to expectations, sST2 enhanced orthotopic tumor growth in immunocompetent but not IL-33 knockout mice, which suggests that IL-33-ST2L signaling inhibits pancreatic cancer growth. Here, IL33 is linked to familial pancreatic carcinoma.