USP22 and metastatic malignant neoplasm: All of 10 (100%) mice injected with the parent A549 cancer cells died of metastatic cancers by day 40; in contrast, all of the mice injected with USP22−/− A549 cancer cells were alive at day 35, and Kaplan-Meier survival analysis showed the survivals of USP22−/− A549 cancer-bearing mice were significantly longer than that of A549 cancer-bearing mice (P < 0.0001, Fig. 4c).