In this regard, a recent in vivo study by Yan et al. unexpectedly showed that MAIT cells were found to promote cancer metastasis by suppressing T and/or NK cells (which was partly IL-17 dependent) after interaction with MR1 molecules expressed on tumor cells and pre-treatment of tumor cells with 5-OP-RU increased lung metastases [9]. Here, MR1 is linked to cancer.