Association between Cannabinoid CB(1) Receptor Expression and Akt Signalling in Prostate Cancer

BACKGROUND: In prostate cancer, tumour expression of cannabinoid CB(1) receptors is associated with a poor prognosis. One explanation for this association comes from experiments with transfected astrocytoma cells, where a high CB receptor expression recruits the Akt signalling survival pathway. In the present study, we have investigated the association between CB(1) receptor expression and the Akt pathway in a well-characterised prostate cancer tissue microarray. METHODOLOGY/PRINCIPAL FINDINGS: Phosphorylated Akt immunoreactivity (pAkt-IR) scores were available in the database. CB(1) receptor immunoreactivity (CB(1)IR) was rescored from previously published data using the same scale as pAkt-IR. There was a highly significant correlation between CB(1)IR and pAkt-IR. Further, cases with high expression levels of both biomarkers were much more likely to have a more severe form of the disease at diagnosis than those with low expression levels. The two biomarkers had additive effects, rather than an interaction, upon disease-specific survival. CONCLUSIONS/SIGNIFICANCE: The present study provides data that is consistent with the hypothesis that at a high CB(1) receptor expression, the Akt signalling pathway becomes operative.