Transient reduction of PTI-1 expression by short interfering RNAs inhibits the growth of human prostate cancer cell lines.

The prostate tumor-inducing gene 1 (PTI-1) was originally identified by differential ribonucleic acid (RNA) display in human prostate carcinoma. PTI-1 is expressed in human prostate carcinoma but not in benign prostate hypertrophy or normal prostate tissue. PTI-1 may be a member of oncogenes that could affect protein translation and contribute to carcinoma development in human prostate. To investigate the role of PTI-1 in human prostate carcinoma, we constructed three different short interfering RNA (siRNA) vectors (pSilencer3.1-neo-Yu Lei [YL]1-2, -YL3-4 and -YL5-6), each of which was transfected into DU145 and PC3 human prostate cancer cell lines. Among these siRNAs, only pSilencer3.1-neo-YL1-2 could almost completely block the expression of PTI-1 in these two cell lines. The growth of the cell lines was then evaluated after transfection. The proliferation rate was retarded in DU145 and PC3 cells transfected with pSilencer3.1-neo-YL1-2, compared with the cells transfected with a control vector; namely, about 88.6% of DU145 and 80.2% of PC3 cancer cells were blocked at the G1 phase when transfected with pSilencer3.1-neo-YL1-2, compared to 62.0% in DU145 cells and 51.7% in PC3 cells, transfected with the control vector. Moreover, 68.3% of DU145 cells and 72.3% of PC3 cells were induced into apoptosis, while in control transfection, the population was 26.6% in DU145 cells and 28.4% in PC3 cells. These results indicate that blocking PTI-1 expression can inhibit the growth of certain prostate cancer cell lines. We suggest that PTI-1 may serve as a target for the gene-based therapy of human prostate carcinoma.