IL1RL1 and neoplasm: However, it has also been reported that IL-33 can promote the accumulation of ST2+ Tregs in tumor lesions and exhibits an immunosuppressive effect (16); IL-33 can also promote MDSCs to accumulate in the tumor and secrete a large amount of immunosuppressive cytokines, such as TGF-β1, resulting in tumor metastasis (40).