IL33 and cancer: Furthermore, we have found that IL-33 gene expression by tumours complements MHC-I production and immune recognition of processed tumour antigens, and, consequently, reduces the frequency of circulating tumour cells and also the growth of metastatic tumours in vivo. Overall, this study demonstrates that immunosubversion of the IL-33-dependent antigen processing pathways in metastatic forms of the cancer is a new paradigm for understanding both immune-surveillance and immune escape in malignancy.