IL33 and neoplasm: Several studies have previously addressed the role of the IL-33/ST2 axis in CRC showing either tumor promoting17-24 or tumor reducing effects.26,27,45,46 Concerning the tumor microenvironment, tumor promoting effects by IL-33 have been linked with Tregs, which suppress tumor immunity,18,19 and with macrophage infiltration into tumors to stimulate PGE2 production that enhances colon cancer cell stemness.20 In our present work, we primarily focused on the role of eosinophils in the microenvironment and whether they might play a role in IL-33-induced reduction in tumor growth.