To explore whether regulation of tumorigenesis by USP18 expression in tumor cells was due to host immune status, we intravenously inoculated B16-OVA-GFP or B16-OVA-USP18 tumor cells into NSG (NOD-SCID/IL2Rγ-/-) mice, which are deficient in T, B and NK cells. Here, USP18 is linked to neoplasm.