RESUMEN
It has been proposed that Cyclooxygenase (COX)-2 inhibitors may be able to enhance the effects of chemotherapeutic or radiation treatment; however, currently few studies have been reported that define the radiation-enhancing effect of COX-2 inhibitors. We conducted in vitro radiation survival experiments using rat intestinal epithelial cells which were stably transfected with COX-2 cDNA in the sense (RIE-S) and antisense (RIE-AS) orientations to investigate the potential radiosensitizing effect of the selective COX-2 inhibitor, NS-398. Apoptosis was measured using 7-aminoactinomycin-D with flow cytometry to investigate underlying mechanisms for the effect of NS-398 on radiosensitivity. The same experiments were repeated with NCI-H460 human lung cancer cells, which express COX-2 constitutively, and HCT-116 human colon cancer cells, which lack COX-2 expression. In vivo tumor growth delay assays were also performed with tumors formed by H460 and HCT-116 cells. No difference was observed in the intrinsic radiation sensitivity of RIE-S and RIE-AS cells exposed to radiation alone. However, 150-400 microM of NS-398 enhanced radiosensitivity in a concentration-dependent manner in RIE-S cells with dose enhancement ratios of 1.2-1.9 at a surviving fraction of 0.25. However, this effect was not shown in RIE-AS cells. NS-398 enhanced radiosensitivity in H460 cells with a dose enhancement ratio of 1.8 but protected HCT-116 cells from the effects of radiation. Radiation-induced apoptosis was enhanced by NS-398 in RIE-S and H460 cells but not in RIE-AS and HCT-116 cells. Additionally, this radiation-enhancing effect in RIE-S cells seemed to be attributable to some mechanisms other than the reversal of radioresistance induced by COX-2. NS-398 (36 mg/kg) enhanced the effect of radiation on H460 tumors in vivo by an enhancement factor of 2.5; however, it did not enhance the radiosensitivity of HCT-116 tumors (enhancement factor = 1.04). These in vitro and in vivo results suggest that selective COX-2 inhibitors enhance the effect of radiation on tumors that express COX-2 but not on COX-2-lacking tumors. This effect may be attributable to enhancement of radiation-induced apoptosis. Thus, selective COX-2 inhibitors may have potential as radiosensitizers for treatment of human cancers.
Asunto(s)
Inhibidores de la Ciclooxigenasa/farmacología , Isoenzimas/antagonistas & inhibidores , Nitrobencenos/farmacología , Sulfonamidas/farmacología , Animales , Apoptosis/efectos de los fármacos , Apoptosis/efectos de la radiación , Supervivencia Celular/efectos de la radiación , Células Cultivadas , Terapia Combinada , Ciclooxigenasa 2 , Inhibidores de la Ciclooxigenasa 2 , Inhibidores de la Ciclooxigenasa/uso terapéutico , ADN sin Sentido/genética , Relación Dosis-Respuesta en la Radiación , Células Epiteliales/citología , Células Epiteliales/efectos de los fármacos , Células Epiteliales/efectos de la radiación , Humanos , Mucosa Intestinal/citología , Mucosa Intestinal/efectos de los fármacos , Mucosa Intestinal/efectos de la radiación , Isoenzimas/genética , Proteínas de la Membrana , Ratones , Ratones Desnudos , Trasplante de Neoplasias , Neoplasias Experimentales/tratamiento farmacológico , Neoplasias Experimentales/patología , Neoplasias Experimentales/radioterapia , Nitrobencenos/uso terapéutico , Prostaglandina-Endoperóxido Sintasas/genética , Ratas , Sulfonamidas/uso terapéutico , Factores de Tiempo , Transfección , Células Tumorales Cultivadas , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Prior studies using pO(2) microelectrodes have shown that RSR13, an allosteric modifier of hemoglobin, increases tissue oxygenation in vivo. Recently, measurements of tissue oxygenation have been performed by many investigators using blood oxygen level-dependent magnetic resonance imaging (BOLD MRI). In this study, we tested the hypothesis that the BOLD MRI signal ratio in tumors will change after administration of RSR13. NCI-H460 human lung carcinoma cells were used as a xenograft in athymic nude mice. Mice with 1-cm(3) tumors in the flank were anesthetized and mounted on the MRI apparatus, and various doses of RSR13 were administered intraperitoneally (i.p.). MR images were then acquired at 10-min intervals for up to 60 min after injection. The effect of RSR13 on tumor response was studied using the same mouse xenograft model with tumor growth delay measurements. RSR13 increased the MRI signal ratio [Intensity(t)/Intensity(t = 0)] in a dose-dependent manner, with maximum increases occurring 30 min after RSR13 was administered. An RSR13 dose of 200 mg/kg proved to be optimum. Since the MRI signal ratio has been shown previously to be linearly related to tissue oxygenation, the changes in the MRI signal ratio can be attributed to changes in tumor oxygen levels. Using a 200-mg/kg dose of RSR13, with a 10-Gy dose of radiation administered to tumors 30 min later, enhancement of radiation-induced tumor growth delay by RSR13 was observed (enhancement factor = 2.8). Thus our MRI results support and verify the previously reported RSR13-induced increase in tumor oxygenation obtained using pO(2) microelectrodes. Based upon these results and other previous studies, the mechanism of enhancement of the effect of radiation by RSR13 probably involves an increase in tumor oxygenation.
Asunto(s)
Compuestos de Anilina , Carcinoma de Células Grandes/metabolismo , Hemoglobinas/metabolismo , Neoplasias Pulmonares/metabolismo , Oxígeno/metabolismo , Propionatos/farmacología , Fármacos Sensibilizantes a Radiaciones/farmacología , Regulación Alostérica , Animales , Humanos , Imagen por Resonancia Magnética , Ratones , Trasplante de Neoplasias , Células Tumorales CultivadasRESUMEN
PURPOSE: We evaluated the orally administered platinum agent, JM216, in combination with ionizing radiation both in vivo and in vitro against human tumor cells. METHODS: H460 human lung carcinoma cells were used as a subcutaneous xenograft in nude mice. JM216 (30 mg/kg) was administered orally, and radiation treatments (2 Gy) were given 1 h after JM216 delivery for five consecutive days. For in vitro analysis, attached H460 cells were treated with JM216 (15 microM) for 1 h and then irradiated. Cells were rinsed 20 min later, and survival was determined by clonogenic assay. RESULTS: Tumor growth delay measurements showed that the combination of JM216 and radiation was additive in vivo, with an enhancement ratio of 1.24. In vitro clonogenic survival experiments demonstrated a dose enhancement ratio of 1.23. Isobologram analysis showed that this interaction was also additive. CONCLUSIONS: These data demonstrate that the combination of JM216 and fractionated radiotherapy is more effective against human lung cancer xenografts than either agent alone, and the in vivo results were supported by those observed using an in vitro system with the same tumor cell line.
Asunto(s)
Antineoplásicos/uso terapéutico , Carcinoma/terapia , Neoplasias Pulmonares/terapia , Compuestos Organoplatinos/uso terapéutico , Animales , Carcinoma/tratamiento farmacológico , Carcinoma/radioterapia , Trasplante de Células , Terapia Combinada , Femenino , Humanos , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/radioterapia , Ratones , Ratones Desnudos , Trasplante de Neoplasias , Análisis de Supervivencia , Células Tumorales CultivadasRESUMEN
PURPOSE: To test for enhancement of radiation effects in vitro and in vivo by the orally administered camptothecin derivative, 9-nitrocamptothecin (RFS-2000); to study whether the mechanism of this enhancement involves inhibition of sublethal damage recovery. METHODS AND MATERIALS: In vitro: H460 human lung carcinoma cells were incubated with RFS-2000 for various times at 37 degrees C, irradiated, immediately rinsed, and assessed for colony-forming ability. Sublethal damage recovery (SLDR) was also assessed using two split doses of radiation. In vivo: H460 cell xenografts were used in nude mice. Tumors were grown subcutaneously on the flank, then treated with RFS-2000 (1 mg/kg) and/or radiation (2 Gy) for 5 consecutive days. Tumor growth delay was then measured for each treatment group. RESULTS: Radiation enhancement was observed in vitro for incubation times between 4 and 24 hr with 10 nM RFS-2000. Using a 24-hr treatment, the radiation dose enhancement ratio values (DER) for 5, 10, and 15 nM were 1.22, 1.54, and 2.0, respectively. Incubation with 10 nM RFS-2000 inhibited SLDR by a factor of 2. The results of three independent in vivo experiments showed that RFS-2000 can enhance the effects of fractionated radiotherapy, with an enhancement factor (EF) of 1.64. CONCLUSION: Our results show that RFS-2000 can enhance the effects of radiation in human lung cancer cells both in vitro and in vivo, and that the mechanism of this effect may involve the inhibition of SLDR.