Aim: 

Human prostate cancers express type 1 GnRH receptor. Their proliferation is time- and dose-dependently reduced by GnRH-I and its analogues. Recently, we have observed that GnRH-II has a strong anti-proliferative effect on prostate cancer cells but a full–length functional type II GnRH receptor has not been found in humans. In the present study we aimed to demonstrate the involvement of type 1 GnRH receptor in mediating the anti-proliferative effect of GnRH-II in human androgen-indipendent prostate cancer cell line PC3.

Methods: 

To investigate the role of type 1 GnRH receptor in mediating the anti-proliferative effect of GnRH-II, the powerful technique of RNA interference (RNAi) was employed. To monitor the RNAi transfection efficiency, RT-PCR, immunoblot and immunofluorescence analysis were performed. For cell proliferation studies, PC3 cells were treated for7 days and then were harvested and counted by hemocytometer.

We subsequently investigated whether the anti-proliferative action of GnRH-II might be mediated by the Gi-cAMP signal trasduction pathways. At this pourpose, we evaluated the effect of GnRH-II on cAMP concentration.

Results: 

The RNAi control experiments showed that the type 1 GnRH receptor expression was significantly reduced in RNAi-transfected cells. Transfection with RNAi targeted to the type 1 GnRH receptor blocked the anti-proliferative effect of GnRH-II. Moreover GnRH-II treatment significantly decreases forskolin-stimulated cAMP levels only when it binds to type 1 GnRH receptor.

Conclusion: 

These observations demostrate that GnRH-II must bind to type 1 GnRH receptor to exert its anti-proliferative action in prostate cancer cells.