As tumor cells were intravenously injected into mice, the change in tumor burden was not due to the difference of invasion or migration of tumor cells (Additional file1: Figure S4A-C).In order to confirm this finding, we subcutaneously inoculated B16-OVA-shCon, B16-OVA-shUSP18, or B16-OVA-USP18 tumor cells into C57BL/6 mice. This evidence concerns the gene USP18 and neoplasm.