Low-dose ionizing radiation decreases the frequency of neoplastic transformation to a level below the spontaneous rate in C3H 10T1/2 cells
Low-dose ionizing radiation decreases the frequency of neoplastic transformation to a level below the spontaneous rate in C3H 10T1/2 cells
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DOI：
10.2307/3579298
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发表时间：
1996-10-01
影响因子：
3.4
通讯作者：
Mitchel, REJ
中科院分区：
文献类型：
--
作者：
Azzam, EI;deToledo, SM;Mitchel, REJ
我们之前的研究表明，在低至10 cGy的剂量下，慢性暴露于高原期C3H 10T1/2细胞的Co-60 γ辐射可保护细胞免受随后的大急性辐射暴露的肿瘤转化。我们还表明，这种诱导的对肿瘤转化的抵抗与修复辐射诱导的染色体断裂的能力增加相关。我们现在表明，静息细胞单次暴露于低至0.1 cGy的剂量也可以降低肿瘤转化的风险，从自发水平降低到低于该水平的三到四倍。更高剂量，在相同剂量率下（0.24 cGy/min）高达10 cGy，并没有进一步降低肿瘤转化频率。这种保护作用仅在接触抑制释放之前，在37摄氏度下孵育的辐照细胞中可见。照射后立即释放到低密度传代培养中的细胞肿瘤转化频率不变。这些结果表明，低剂量或长期暴露于辐射可以诱导保护细胞免受自然发生的以及辐射诱导的导致细胞转化的改变的过程。如果在人类细胞中诱导类似的过程，结果还表明，在背景或职业照射水平下，单次低剂量可能在某些情况下降低而不是增加癌症风险，这一结论与辐射致癌风险的线性无阈值模型不一致。(C) 1996年，辐射研究学会
We have previously shown that chronic exposure of plateau-phase C3H 10T1/2 cells to Co-60 gamma radiation at doses as low as 10 cGy protected the cells against neoplastic transformation by a subsequent large acute radiation exposure. We have also shown that this induced resistance to neoplastic transformation correlated with an increased ability to repair radiation-induced chromosome breaks. We now show that a single exposure of quiescent cells to doses as low as 0.1 cGy also reduces the risk of neoplastic transformation, from the spontaneous level to a rate three- to fourfold below that level. Higher doses, up to 10 cGy at the same dose rate (0.24 cGy/min), did not reduce the neoplastic transformation frequency further. This protective effect was seen only in irradiated cells that were allowed to incubate at 37 degrees C before release from contact inhibition. Cells released into low-density subcultures immediately after irradiation had unchanged neoplastic transformation frequencies. These results demonstrate that low or chronic exposure to radiation can induce processes which protect the cell against naturally occurring as well as radiation-induced alterations that lead to cell transformation. If similar processes are induced in human cells, the results also suggest that a single low dose, at background or occupational exposure levels, may in some circumstances reduce rather than increase cancer risk, a conclusion inconsistent with the linear no-threshold model of cancer risk from radiation. (C) 1996 by Radiation Research Society