RESUMEN
Prostate cancer is initially treated via androgen deprivation therapy (ADT), a highly successful treatment in the initial pursuit of tumor regression, but commonly restricted by the eventual emergence of a more lethal 'castrate resistant' form of the disease. Intracrine pathways that utilize dehydroepiandrosterone (DHEA) or other circulatory precursor steroids, are thought to generate relevant levels of growth-stimulating androgens such as testosterone (T) and dihydrotestosterone (DHT). In this study, we explored the capacity of the active vitamin D hormone to interact and elicit changes upon this prostatic intracrine pathway at a metabolic level. We used androgen dependent LNCaP cells cultured under steroid-depleted conditions and assessed the impact of vitamin D-based compounds upon intracrine pathways that convert exogenously added DHEA to relevant metabolites, through Mass Spectrometry (MS). Changes in relevant metabolism-related gene targets were also assessed. Our findings confirm that exposure to vitamin D based compounds, within LNCaP cells, elicits measurable and significant reduction in the intracrine conversion of DHEA to T, DHT and other intermediate metabolites within the androgenic pathway. The aassessment and validation of the biological model and analytical platforms were performed by pharmacological manipulations of the SRD5α and HSD-17ß enzymes. The data provides further confirmation for how a vitamin D-based regime may be used to counter intracrine mechanisms contributing to the emergence of castrate-resistant tumors.
Asunto(s)
Antagonistas de Andrógenos/farmacología , Andrógenos/metabolismo , Neoplasias de la Próstata/tratamiento farmacológico , Vitamina D/farmacología , Humanos , Ligandos , Masculino , Neoplasias de la Próstata/metabolismo , Neoplasias de la Próstata/patología , Células Tumorales CultivadasRESUMEN
BACKGROUND: A contributing factor to the emergence of castrate resistant prostate cancer (CRPC) is the ability of the tumor to circumvent low circulating levels of testosterone during androgen deprivation therapy (ADT), through the production of "intracrine" tumoral androgens from precursors including cholesterol and dehydroepiandrosterone (DHEA). As these processes promote AR signaling and prostate cancer progression their modulation is required for disease prevention and treatment. METHODS: We evaluated the involvement of the vitamin D receptor ligand EB1089 in the regulation of genes with a role in androgen metabolism using the androgen dependent cell lines LNCaP and LAPC-4. EB1089 regulation of androgen metabolism was assessed using QRT-PCR, luciferase promoter assays, western blotting, enzyme activity assays, and LC-MS analyses. RESULTS: EB1089 induced significant expression of genes involved in androgen metabolism in prostate cancer cells. Real-Time PCR analysis revealed that VDR mediated significant regulation of CYP3A4, CYP3A5, CYP3A43, AKR1C1-3, UGT2B15/17, and HSD17B2. Data revealed potent regulation of CYP3A4 at the level of mRNA, protein expression and enzymatic activity, with VDR identified as the predominant regulator. Inhibition of CYP3A activity using the specific inhibitor ritonavir resulted in alleviation of the anti-proliferative response of VDR ligands in prostate cancer cells. Mass spectrometry revealed that overexpression of CYP3A protein in prostate cancer cells resulted in a significant increase in the oxidative inactivation of testosterone and DHEA to their 6-ß-hydroxy-testosterone and 16-α-hydroxy-DHEA metabolites, respectively. CONCLUSIONS: These data highlight a potential application of VDR-based therapies for the reduction of growth-promoting androgens within the tumor micro-environment.