The essential role of Giα2 in prostate cancer cell migration.

Cell- and receptor-specific regulation of cell migration by Gi/oα-proteins remains unknown in prostate cancer cells. In the present study, oxytocin (OXT) receptor was detected at the protein level in total cell lysates from C81 (an androgen-independent subline of LNCaP), DU145 and PC3 prostate cancer cells, but not in immortalized normal prostate luminal epithelial cells (RWPE1), and OXT-induced migration of PC3 cells. This effect of OXT has been shown to be mediated by Gi/oα-dependent signaling. Accordingly, OXT inhibited forskolin-induced luciferase activity in PC3 cells that were transfected with a luciferase reporter for cyclic AMP activity. Although mRNAs for all three Giα isoforms were present in PC3 cells, Giα2 was the most abundant isoform that was detected at the protein level. Pertussis toxin (PTx) inhibited the OXT-induced migration of PC3 cells. Ectopic expression of the PTx-resistant Giα2-C352G, but not wild-type Giα2, abolished this effect of PTx on OXT-induced cell migration. The Giα2-targeting siRNA was shown to specifically reduce Giα2 mRNA and protein in prostate cancer cells. The Giα2-targeting siRNA eliminated OXT-induced migration of PC3 cells. These data suggest that Giα2 plays an important role in the effects of OXT on PC3 cell migration. The Giα2-targeting siRNA also inhibited EGF-induced migration of PC3 and DU145 cells. Expression of the siRNA-resistant Giα2, but not wild type Giα2, restored the effects of EGF in PC3 cells transfected with the Giα2-targeting siRNA. In conclusion, Giα2 plays an essential role in OXT and EGF signaling to induce prostate cancer cell migration.