RESUMEN
OBJECTIVE: To determine the role of hypoxia-inducible factor-2alpha (HIF2alpha) on the sensitivity of renal cell carcinoma (RCC) cell lines to ionizing radiation and to determine if the mTOR antagonist, rapamycin, could decrease HIF2alpha protein levels. MATERIALS AND METHODS: Cell lines expressing stable short-hairpin RNAs (shRNAs) encoding HIF2alpha shRNAs or an empty vector were transfected with a hypoxia responsive element (HRE)-driven firefly luciferase reporter gene. Two separate paired cell lines were assayed for their response to increasing doses of ionizing radiation. Proliferation and cell cycle kinetics were compared for cell lines expressing HIF2alpha shRNAs and empty vectors. The effect of an mTOR antagonist, rapamycin on HIF1alpha and HIF2alpha proteins levels was also assessed. RESULTS: We confirmed that the 786-O RCC lines with stably integrated shRNAs against HIF2alpha had decreased activation of a plasmid with a HRE-driven firefly luciferase reporter gene. Lines from two separate cell clones with decreased HIF2alpha levels showed a significant increase in radiation sensitivity and an increase in G2 cell cycle arrest. Rapamycin, while effective in decreasing HIF1alpha protein levels, did not affect HIF2alpha levels in either of the RCC cell lines. CONCLUSIONS: These results show that decreasing levels of HIF2alpha leads to an increased sensitivity to ionizing radiation. This finding may explain in part, the known resistance of RCC to radiation therapy. Although mTOR antagonists are approved for the treatment of RCC, these agents do not decrease HIF2alpha levels and therefore might not be effective in enhancing the radio-sensitivity of these tumours.
Asunto(s)
Antibióticos Antineoplásicos/uso terapéutico , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/farmacología , Carcinoma de Células Renales/radioterapia , Neoplasias Renales/radioterapia , Fármacos Sensibilizantes a Radiaciones/farmacología , Sirolimus/uso terapéutico , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/efectos de los fármacos , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Western Blotting , Carcinoma de Células Renales/tratamiento farmacológico , Carcinoma de Células Renales/patología , Muerte Celular/efectos de los fármacos , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Citometría de Flujo , Fase G2/efectos de los fármacos , Genes Reporteros , Humanos , Neoplasias Renales/tratamiento farmacológico , Neoplasias Renales/patología , Luciferasas/metabolismo , Proteínas Quinasas/efectos de los fármacos , Tolerancia a Radiación , Fármacos Sensibilizantes a Radiaciones/metabolismo , Serina-Treonina Quinasas TORRESUMEN
PURPOSE: The effects of a low-fat diet or a low-fat diet with the addition of a soy supplement were investigated in a pilot Phase II study for asymptomatic, hormonally naive prostate cancer patients with rising prostate-specific antigen (PSA) levels. EXPERIMENTAL DESIGN: A two-step intervention was implemented. During step 1 patients were begun on a low-fat diet with a goal to reduce fat intake to 15% of total daily calories. On PSA progression, a soy protein supplement was added to the diet (step 2). The primary end point was PSA reduction by 50%. Secondary end points were PSA doubling time and time to progression (TTP). Serum was analyzed for changes in the sex hormone and insulin-like growth factor (IGF-I) axes. RESULTS: Among 18 evaluable patients, (median follow-up on study 10.5 months), no patient on either step had a PSA reduction by 50% at any time. There was a trend toward a longer PSA doubling time (P = 0.06) and a prolongation in estimated median TTP of approximately 3 months (P = 0.018) during step 2 compared with step 1 of the study. During step 1, free testosterone levels decreased by 5% (P < 0.01), and during step 2, IGF-I levels increased by 22% (P = 0.02). CONCLUSIONS: A low-fat diet with the subsequent addition of a soy supplement did not result in a significant decline in PSA levels. The addition of soy protein had a modest effect on TTP. A potentially undesirable effect associated with the administration of soy was an increase in IGF-I serum levels.
Asunto(s)
Dieta , Grasas de la Dieta , Antígeno Prostático Específico/biosíntesis , Neoplasias de la Próstata/dietoterapia , Proteínas de Soja/farmacología , Anciano , Metabolismo de los Hidratos de Carbono , Grasas de la Dieta/metabolismo , Humanos , Factor I del Crecimiento Similar a la Insulina/biosíntesis , Masculino , Persona de Mediana Edad , Proyectos Piloto , Antígeno Prostático Específico/sangre , Testosterona/sangre , Nucleótidos de Timina , Resultado del TratamientoRESUMEN
PURPOSE: Elevated serum levels of insulin-like growth factor-1 (IGF-1) have been consistently shown to be a risk factor for prostate cancer. Alterations in serum IGF-1 binding proteins 1 to 3 have also been associated with prostate cancer risk. A potentially important complication in these studies is that prostate tissue, perhaps especially malignant prostate tissue, may secrete IGF-1 and its binding proteins into serum. In fact, it is possible that altered levels of these proteins observed in subjects at risk for prostate cancer are the result of prostate cancer rather than related to its cause. MATERIALS AND METHODS: The contribution of prostate cancer to serum levels of IGF-1 and IGF-1 binding proteins was determined by analyzing serum samples from 86 patients with prostate cancer 2 weeks before and 8 weeks after radical prostatectomy. Preoperative and postoperative values for IGF-1 and its 3 major binding proteins were analyzed using univariate and multivariate analysis models. RESULTS: On univariate analysis significant increases and not decreases in IGF-1, IGF binding protein-1 and 3 were observed after prostatectomy. On multivariate analysis a significant post-prostatectomy increase was observed for IGF-1 binding proteins 1 and 3 but the increase in IGF-1 was not significant. CONCLUSIONS: Increased levels of IGF-1 and IGF-1 binding proteins were unexpected after prostatectomy. This result makes it extremely unlikely that secretion from the prostate, even if it contains cancer, affects serum levels of these proteins. The implication of these findings is that endocrine production of IGF-1 is a factor in prostate cancer risk. Therefore, strategies to lower serum IGF-1 may be potentially useful.