RESUMEN
Oxidation of mitochondrial fatty acids (FA) results in the generation of reactive oxygen species (ROS) which have been postulated to play a key role in the initiation and progression of prostate cancer (PC). We previously reported that androgens increase FA uptake into PC cells. We thus examined if androgens that are known to induce ROS generation regulate FA oxidation in PC cells. The effects of the androgen-depleted medium, R1881 (synthetic androgen) and/or androgen receptor blocker, bicalutamide were examined in the human androgen-responsive but not dependent 22rv1 cells. R1881 supplementation significantly increased mitochondrial FA oxidation ((14)C-radiolabeled FA degradation studies), resulting in increased ROS production. Androgens increased the mRNA levels of carnitine palmitoyltransferase (CPT1), the rate limiting enzyme in the process of mitochondrial FA oxidation. Treatment with R1881 and bicalutamide inhibited these androgen regulated effects. Inhibition of mitochondrial ROS generation by two different inhibitors, rotenone and thenoyltrifluoroacetone, eliminated the androgen-induced ROS generation, to the same level as in cells deprived of androgens or treated with R1881 and bicalutamide. Taken together, androgens increase the mitochondrial oxidation of FA, leading to increased production of ROS that is associated with prostate cell proliferation and mutagenesis. These results therefore support the rationale for PC prevention using 5-alpha reductase inhibitors, dietary restrictions or anti-oxidants, each of which has different inhibitory but complementary effects.
Asunto(s)
Antagonistas de Andrógenos/farmacología , Anilidas/farmacología , Ácidos Grasos/metabolismo , Metribolona/farmacología , Mitocondrias/efectos de los fármacos , Neoplasias Hormono-Dependientes/metabolismo , Nitrilos/farmacología , Estrés Oxidativo/efectos de los fármacos , Neoplasias de la Próstata/metabolismo , Congéneres de la Testosterona/farmacología , Compuestos de Tosilo/farmacología , Carnitina O-Palmitoiltransferasa/genética , Carnitina O-Palmitoiltransferasa/metabolismo , Línea Celular Tumoral , Depuradores de Radicales Libres/farmacología , Regulación Enzimológica de la Expresión Génica , Humanos , Masculino , Mitocondrias/metabolismo , Neoplasias Hormono-Dependientes/patología , Neoplasias Hormono-Dependientes/prevención & control , Oxidación-Reducción , Neoplasias de la Próstata/patología , Neoplasias de la Próstata/prevención & control , ARN Mensajero/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Desacopladores/farmacología , Regulación hacia ArribaRESUMEN
Radiation therapy is a standard treatment for prostate cancer (PC). The postulated mechanism of action for radiation therapy is the generation of reactive oxygen species (ROS). Adjuvant androgen deprivation (AD) therapy has been shown to confer a survival advantage over radiation alone in high-risk localized PC. However, the mechanism of this interaction is unclear. We hypothesize that androgens modify the radioresponsiveness of PC through the regulation of cellular oxidative homeostasis. Using androgen receptor (AR)(+) 22rv1 and AR(-) PC3 human PC cell lines, we demonstrated that testosterone increased basal reactive oxygen species (bROS) levels, resulting in dose-dependent activation of phospho-p38 and pAKT, and increased expression of clusterin, catalase, and manganese superoxide dismutase. Similar data were obtained in three human PC xenografts; WISH-PC14, WISH-PC23, and CWR22, growing in testosterone-supplemented or castrated SCID mice. These effects were reversible through AD or through incubation with a reducing agent. Moreover, testosterone increased the activity of catalase, superoxide dismutases, and glutathione reductase. Consequently, AD significantly facilitated the response of AR(+) cells to oxidative stress challenge. Thus, testosterone induces a preset cellular adaptation to radiation through the generation of elevated bROS, which is modified by AD. These findings provide a rational for combined hormonal and radiation therapy for localized PC.