Prostate cancer is the most commonly diagnosed cancer in men in whom it is the second leading cause of cancer deaths. Androgen deprivation therapy is used to treat advanced disease but inevitably patients relapse and subsequently die. We believe oxytocinergic signalling to be a potential target for treatment of advanced prostate cancer. In several cancer cell types studied, including prostate, differential effects of oxytocin on cell proliferation and migration are noted. We are investigating why differential effects are observed.
Hypothesis: In PC3 prostate cancer cells, the oxytocin receptor (OTR) couples to Gαq/11 which on oxytocin binding, activates a calcium-dependent pathway, resulting in brief ERK1/2 phosphorylation and stimulates cell proliferation and migration/invasion. In DU145 prostate cancer cells it is hypothesised that OTR couples to Gαi that activates calcium-independent signalling pathways that result in prolonged ERK1/2 activation that suppresses cell proliferation.
Methods: We investigated calcium dynamics using live cell imaging of FURA-2 loaded cells, following perfusion with 100nmol/L oxytocin. ERK1/2 activation patterns were determined by western blot following treatment with 100nmol/L Oxytocin for 0-120 minutes. MMP zymography identified if determinants of cellular invasion were affected. The contribution of Gαi signalling to responses observed was investigated in cells pre-treated with the Gαi inhibitor pertussis toxin.
Results: Oxytocin increased intracellular calcium in ~60% of PC3 cells examined. Pre-treatment with pertussis toxin partially ablated the response. No response in ERK1/2 was identified. In DU145 cells, oxytocin did not induce a calcium response but did induce a small response in ERK1/2 phosphorylation. In DU145 cells, MMP-9 activity was reduced by oxytocin treatment.
Conclusion: Oxytocin activates different cell-signalling pathways in DU145 cells and PC3 cells that might account for the differences in downstream responses observed. We are currently examining if the reductions in MMP correlates with reductions in migration and invasion using real-time wound healing assays.