Objectives: RNA interference (RNAi) has the potential to be developed into therapeutics for prostate cancer, but the lack of cellular targets limits its application. In the present study we attempt to develop a prostate cancer-specific RNAi system using the human prostate specific membrane antigen (PSMA) promoter/enhancer; furthermore, we analyzed its inhibitive effect on STAT3 expression.
Methods: The adenoviral vectors containing a small hairpin RNA (shRNA) to target exogenous reporters enhance green fluorescent protein (EGFP) and endogenous gene signal transducers and activators of transcription 3 (STAT3) were constructed. After prostate cancer and other cells were transfected, reverse transcription-polymerase chain reaction (RT-PCR), fluorescence microscopy, and Western blotting were used to measure EGFP expression. Inhibition of STAT3 was evaluated by Western blotting. Cell proliferation and viability were measured by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Cell apoptosis was analyzed with double-staining of Annexin V and PI.
Results: Our study showed that with the PSMA promoter/enhancer directly driving shRNA transcription, expression of the exogenous reporters EGFP in prostate cancer cells, but not other cancer cells and normal cells, was specifically inhibited in vitro. The PSMA promoter/enhancer-driven shRNA also depressed the expression of STAT3 in only prostate cancer cells. Inhibition of STAT3 suppressed proliferation of PC-3 and LNCaP cells.
Conclusions: The present study describes an efficient RNAi system for gene silencing that is specific to prostate cancer cells using the PSMA promoter/enhancer. Suppression of STAT3 by using this system decreased proliferation and induced apoptosis of PC-3 and LNCaP cells. This system may be useful for RNAi therapy for prostate cancer.