In a number of studies, immuno-histochemical staining of tissue samples from patients and mouse models as well as measurement of mRNA expression of IL-33 and ST2 in tumor samples have collectively reported higher levels in adenomas and early stage CRC [64,65,66,68] as compared to higher-grade and more advanced or late stage tumors, suggesting that IL-33/ST2 signaling may play an anti-tumorigenic role in later stages of CRC. This evidence concerns the gene IL1RL1 and neoplasm.