Since USP22 is more dominant than USP7 in cancer cell proliferation, USP22 was partially knocked down in A549 and H1299 cancer cells (Fig. 5C, Upper panel), using 1/6 and 1/3 of amounts of siRNA that could completely silence USP22 to further confirm the synergistic effect of targeting these two Dubs; the results showed that partial knockdown of USP22 significantly enhanced the inhibition of USP7 knockdown alone on the proliferation of both cancer cells (Fig. 5C, Lower panel). This evidence concerns the gene USP22 and cancer.