Tamaki Yoshio, Mitsuhashi Norio, Sakurai Hideyuki, Islam Mohammad Shahidul, Takahashi Takeo, Akimoto Tetsuo, Ishikawa Hitoshi, Saitoh Jun-Ichi, Muramatsu Hiroyuki, Niibe Hideo
Department of Radiology and Radiation Oncology, Gunma University School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma 371-8511.
Anticancer Res. 2002 Nov-Dec;22(6A):3143-8.
Two rat yolk sac tumor cell lines, NMT-1 and NMT-1R, are of the same origin and of different sensitivity to irradiation and to heat. The aim of this study was to investigate the sensitivities of these two cell lines to combined treatments of low-dose irradiation at 2 Gy and hyperthermia at 42 degrees C.
The cell survival was assayed by soft agar clonogenic assay. After the survival curves of radiation alone and of heat alone at various temperatures were estimated, not only the effect of irradiation on heat, but the effect of heat on irradiation were evaluated with sequential treatments in both cell lines. These effects on survival curves were evaluated by the enhancement ratios at isosurvival levels of 37%, 10% and 1%, respectively.
NMT-1 was more sensitive to radiation but more resistant to heat than NMT-1R. For 1% survival level, radiosensitivity in NMT-1 was 1.32 times that in NMT-1R, while thermal sensitivity at 42 degrees C in NMT-1R was 2.73 times that in NMT-1. For sequential treatment, thermosensitization by a radiation dose of 2 Gy in radiosensitive NMT-1 was greater than that in radioresistant NMT-1R. Following heat at 42 degrees C for 1 hour, increased radiosensitivity in NMT-1R was significant, whereas the same heat treatment produced an increase in the radiation sensitivity of NMT-1 with a reduction of the survival curve shoulder but with less slope modification. There was no difference in the surviving fraction in the time-course of a combination of heat and irradiation at various intervals within 6 hours for NMT-1 except for heating immediately after irradiation. However a significant increase in survival was observed when heat was applied more than 3 hours after 2 Gy irradiation for NMT1-R.
These results from our cell lines with the same origin were useful for investigation into the interaction of irradiation with heat.
两种大鼠卵黄囊瘤细胞系NMT - 1和NMT - 1R起源相同，但对辐射和热的敏感性不同。本研究的目的是调查这两种细胞系对2 Gy低剂量辐射和42℃热疗联合治疗的敏感性。
采用软琼脂克隆形成试验检测细胞存活率。在估计了不同温度下单独辐射和单独热疗的存活曲线后，通过对两种细胞系进行序贯治疗，评估了辐射对热的影响以及热对辐射的影响。通过分别在37%、10%和1%等存活水平下的增强率来评估这些对存活曲线的影响。
NMT - 1比NMT - 1R对辐射更敏感，但对热更耐受。在1%存活水平时，NMT - 1的放射敏感性是NMT - 1R的1.32倍，而NMT - 1R在42℃时的热敏感性是NMT - 1的2.73倍。对于序贯治疗，放射敏感的NMT - 1中2 Gy辐射剂量的热增敏作用大于放射耐受的NMT - 1R。在42℃加热1小时后，NMT - 1R的放射敏感性显著增加，而相同的热处理使NMT - 1的辐射敏感性增加，存活曲线的肩部降低，但斜率变化较小。对于NMT - 1，除了照射后立即加热外，在6小时内不同间隔的热与辐射联合治疗的时间进程中，存活分数没有差异。然而，对于NMT1 - R，在2 Gy照射后3小时以上施加热疗时，观察到存活率显著增加。
这些来自相同起源细胞系的结果有助于研究辐射与热的相互作用。
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