The results obtained can be summarized as follows. Firstly, cannabinoids and BDS reduced PCC viability with higher potency and efficacy in the absence of serum proteins, and regardless of the presence of hormones in the medium and of the androgen dependency of the PCC line under study. With serum deprivation, CBD was the most efficacious compound in three out of the four cell lines investigated. These results are in full agreement with previous observations in glioma cells (Jacobsson et al., 2000). Secondly,amongst all the possible known cannabinoid targets investigated, only TRPM8 channels, when present (as in LNCaP cells), seemed to mediate, and only in part, the effect of CBD. Finally, under certain dosing conditions, CBD produced synergistic effects with docetaxel and/or bicalutamide in DU‐145 and/or LNCaP cells.
Based on this first set of results, we decided to test CBD against the growth of xenograft tumours generated in athymic mice from LNCaP and DU‐145 cells. As CBD–BDS was more efficacious in vitro than CBD in the presence of serum proteins, we administered this preparation. Given alone, CBD–BDS reduced tumour size in xenografts generated from LNCaP cells. In these tumours, CBD also significantly enhanced the anti‐cancer effects of bicalutamide (extending the survival time of the animals), but not those of docetaxel. Instead, CBD–BDS was inactive by itself against the growth of DU‐145 xenografts in vivo, although it potentiated the effect of docetaxel. These findings suggest that Cannabis extracts enriched in CBD might provide the basis for new therapies against prostate carcinoma, either as stand alone treatments or in addition to currently used drugs for this type of tumor.
