Abstract: Objective To investigate the expression of ubiquitin-specifi c protease 22(USP22) in bone marrow cells in patients with acute leukemia(AL) and its clinical signifi cance. Methods Real-time quantitative PCR (qPCR) and Western blot were used to detect mRNA and protein expression levels of USP22 in Jurkat, HL-60, K562, molt-4 and NB4 cell lines and bone marrow mononuclear cells from AL patients and negative control patients, respectively. Results USP22 expression was found in Jurkat, HL-60, K562, molt-4 and NB4 cell lines. mRNA and protein expressions of USP22 in initial diagnosis group (33.90±9.58) and (0.58±0.15) and remission group(1.81±0.53) and (0.10±0.03) were both increased, compared with that in negative control group (1.05±0.33) and (0.05±0.02) (P<0.001). Meanwhile, expression levels of USP22 mRNA and protein in hyperleukocytic AL patients in initial diagnosis group (45.23±10.92) and (0.69±0.16) were significantly higher than those in non-hyperleukocytic AL patients (26.73±6.12) and (0.42±0.10), P<0.001. But no signifi cant difference of USP22 and protein expressions was found between acute myeloid leukemia(AML) and acute lymphoblastic leukemia (ALL) patients in initial diagnosis group (P=0.531, 0.377). Moreover, AL patients with higher USP22 expression (54.17%) had lower complete remission rate than that with lower USP22 expression (88.0%) after the fi rst induction chemotherapy. Conclusion USP22 is highly expressed in AL patients and decreased after complete remission, which might relate to leukocytes number. Taken together, it could be a useful parameter for prognosis of AL patients.