Immunosuppressive cell populations harbor inhibitory mechanisms, for example, arginase 1, iNOS and NAPDH oxidase to induce T-cell proliferative arrest and to inhibit T-cell activation.3 Thus, using cancer vaccines to induce tumor-specific T-cell responses in combination with strategies to target immunosuppressive cell populations in cancer patients can be a preferable scheme for the treatment of malignancies.4 This evidence concerns the gene FMO5 and cancer.