KDM4A is essential for tumor cell proliferation. (A) MTT cell proliferation assay and (B) crystal violet staining of normal immortalized RWPE-1 cell and prostate cancer cell lines LNCaP, CWR22Rv1 and C4-2B, infected with lentivirus carrying control pLKO.1 or shKDM4A constructs. The cells were infected on day 0, and MTT was added to detect viable cells every two days after infection. 8 days after lentiviral infection, the cells were fixed and stained by crystal violet. (C) Caspase 3/7 activity of the lentiviral-infected cells was detected on day 6. (D) 3 days after infection, the expression of KDM4A was examined by western blotting. (E) CWR22Rv1 xenograft tumor growth. CWR22Rv1 cells were infected by lentivirus carrying pLKO.1 or shKDM4A for 2 days, and then implanted subcutaneously into nude mice. 10 days after implantation, the tumor volumes were measured up to 3 weeks. Data are presented as mean ± SD, with the SD derived from 10 mice. (F) Ki-67 and KDM4A immunohistochemistry staining of the tumor sections isolated from the xenografts. All cell culture-based data are presented as the average of n ≥ 3 replicates ± SD. **:p< 0.01, *: p<0.05