AIM: The expression of cytokines plays an important role in the transmission of the effects of ionizing radiation to tumor cells and normal tissue. Tumor necrosis factor alpha (TNF alpha), a pleiotropic monokine, is of special interest because of its cytotoxic effect on tumor cells and the induction of hemorrhagic necrosis in tumors. We examined the influence of ionizing radiation on TNF alpha production in a human Ewing's sarcoma cell line in vitro and in vivo. METHODS: The protein and mRNA levels of the Ewing's sarcoma cell line RM 82 were examined in vitro with "Enhanced Amplified Sensitivity Immunoassay" (EASIA) and semiquantitative RT-PCR before and after treatment with single doses of 2 to 40 Gy, 1 to 72 hours after irradiation. After successful transplantation to nude mice, the time and dose correlation of TNF alpha mRNA production was examined in vivo. RESULTS: In vitro, RM 82 had a basal protein level of TNF alpha of 20.1 +/- 4.3 pg/ml/10(6) cells. We observed a time- and dose-dependent increase of TNF alpha expression with a maximum of 125 pg/ml/10(6) (5.9 fold) 24 hours after irradiation with 20 Gy. At the mRNA level, the maximal up-regulation occurred 6 to 12 hours after 10 Gy. In vivo, the xenograft tumor maintained the capacity of TNF alpha expression. Time- and dose-dependency in mRNA production showed a maximum increase 6 hours after treatment with 10 Gy. CONCLUSIONS: The presented experiments show in vitro a dose- and time-dependent up-regulation of TNF alpha in the Ewing's sarcoma cell line RM 82 on protein and mRNA level. For the first time this phenomenon was also observed in vivo in a human xenograft tumor. This tumor model could be used for further experiments to examine the role of TNF alpha as a biologic radiation response modifier in human tumors.
AIM: The expression of cytokines plays an important role in the transmission of the effects of ionizing radiation to tumor cells and normal tissue. Tumor necrosis factor alpha (TNF alpha), a pleiotropic monokine, is of special interest because of its cytotoxic effect on tumor cells and the induction of hemorrhagic necrosis in tumors. We examined the influence of ionizing radiation on TNF alpha production in a humanEwing's sarcoma cell line in vitro and in vivo. METHODS: The protein and mRNA levels of the Ewing's sarcoma cell line RM 82 were examined in vitro with "Enhanced Amplified Sensitivity Immunoassay" (EASIA) and semiquantitative RT-PCR before and after treatment with single doses of 2 to 40 Gy, 1 to 72 hours after irradiation. After successful transplantation to nude mice, the time and dose correlation of TNF alpha mRNA production was examined in vivo. RESULTS: In vitro, RM 82 had a basal protein level of TNF alpha of 20.1 +/- 4.3 pg/ml/10(6) cells. We observed a time- and dose-dependent increase of TNF alpha expression with a maximum of 125 pg/ml/10(6) (5.9 fold) 24 hours after irradiation with 20 Gy. At the mRNA level, the maximal up-regulation occurred 6 to 12 hours after 10 Gy. In vivo, the xenograft tumor maintained the capacity of TNF alpha expression. Time- and dose-dependency in mRNA production showed a maximum increase 6 hours after treatment with 10 Gy. CONCLUSIONS: The presented experiments show in vitro a dose- and time-dependent up-regulation of TNF alpha in the Ewing's sarcoma cell line RM 82 on protein and mRNA level. For the first time this phenomenon was also observed in vivo in a human xenograft tumor. This tumor model could be used for further experiments to examine the role of TNF alpha as a biologic radiation response modifier in humantumors.