ObjectiveThis study is aimed to determine the expression of ubiquitin-specific peptidase 39 (USP39) protein in the colorectal cancer (CRC) tissues, and the effect of silencing USP39 gene on the cell growth and cell cycle distribution of CRC cells.Methods① The expressions of USP39 protein in CRC tissues and its paracancerous tissues were determined by immunohistochemical staining method. ② By lentiviral infection, Lv-shUSP39 (KD-1 and KD-2 group) and Lv-shCon (shCon group) were transferred into SW1116 and HCT116 cells, and cells of blank control group did not received any treatment (Con group). To determine the role of USP39 gene in cell growth, MTT assay was performed to draw growth curve, and cell cycle distribution of CRC cells in the 4 groups were determined by flow cytometer.Results① The expression of USP39 protein was higher in CRC tissues compared to adjacent tissues (P=0.007). ② For SW1116 and HCT116 cells, the cell proliferation ability of KD-1 and KD-2 groups were remarkably decreased than those in corresponding shCon and Con groups on 3, 4, and 5-day (P<0.05). ③ Flow cytometry assay showed that, the percentage of G0/G1 phase cells were decreased obviously (P<0.05), while increased significantly in percentage of G2/M phase and number of sub-G1 phase cells in KD-1 group compared with that in the Con group and shCon group of SW1116 and HCT116 cells (P<0.05).ConclusionsThe expression of USP39 protein is highly expressed in CRC tissues. Knockdowning of USP39 gene can inhibit cell proliferation and promote cell apoptosis.