Objective:To investigate the expression protein of HHV-8 K13 in human endothelial and prostate cancer cells respectively, and evaluate the effect on the proliferation of the two cell lines. Methods:The recombinant plasmid PEF-K13-Flag-IRES/Puro was transiently trancfected into EA.HY926 cells and PC-3 cells. The expression of K13 protein in both cells was analyzed by Western blot. The function of K13 protein in cell cycle and cell proliferation were measured by flow cytometry and MTT assay, respectively. Results:The specific band of K13 protein was detected at the expected place by Western blot. In addition, the results of the flow cytometry and MTT assay showed that the HHV-8 K13 protein could significantly inhibit the proliferation in human endothelial and prostate cancer cells. Conclusion:HHV-8 K13 protein might inhibit the growth of human endothelial and prostate cancer cells.