OBJECTIVE Recent studies have shown that hepsin, a type of transmembrane serine protease, is highly upregulated in prostate cancer, but, little is known about its role in progression and invasion of this cancer. We constructed a hepsin-expressing plasmid and transfected it into PC-3 cells to investigate the effect of the hepsin gene on the biological behavior of the PC-3 cells.METHODS Plasmid pHepsin-IRES2 was transfected into prostate cancer PC-3 cells using Fugene6, and the cells with stable hepsin expression were screened and selected with Zeocin (600 mg/L). The hepsin mRNA level was measured by real-time PCR and the growth curve of the PC-3-transfected cells assessed using MTT and BrdU assays. A Boyden chamber was used to examine the difference in invasion and metastases between transfected and non-transfected cells.RESULTS The hepsin mRNA level in pHepsin-IRES2 transfected -PC-3 cells was significantly higher than that found in the control PC-3 cells. While the growth curve of the hepsin gene transfected PC-3 cells showed that there was no significant effect on proliferation, the invasive ability of the pHepsin-IRES2 transfected PC-3 cells, as compared with control cells, was significantly increased (P＜0.05).CONCLUSION The results suggest that even though hepsin has no effect on the proliferation of prostate cancer PC-3 cells, it does promote cellular invasion and metastasis.Therefore hepsin may have a role in the development of prostate cancer.