Laszlo Andrei, Davidson Teri, Harvey Amanda, Sim Julia E, Malyapa Robert S, Spitz Douglas R, Roti Roti Joseph L
Division of Radiation and Cancer Biology, Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO 63108, USA.
Int J Hyperthermia. 2006 Feb;22(1):43-60. doi: 10.1080/02656730500394296.
This paper examined heat-induced radiosensitization in two Chinese hamster heat-resistant cell lines, HR-1 and OC-14, that were isolated from the same wild-type HA-1 cell line. It found a reduction of the magnitude of heat-induced radiosensitization after exposure to 43 degrees C in both HR-1 and OC-14 cells and a similar reduction after exposure to 45 degrees C in HR-1 cells, but not in OC-14 cells. The effect of heat exposure on a class of ionizing radiation-induced DNA damage that inhibits the ability of nuclear DNA to undergo super-coiling changes was also studied using the fluorescent halo assay in these three cell lines. Wild type cells exposed to either 43 or 45 degrees C before irradiation had a DNA rewinding ability that was intermediate between control and unheated cells, a phenomenon previously described as a masking effect. This masking effect was significantly reduced in HR-1 cells exposed to either 43 or 45 degrees C or in OC-14 cells exposed to 43 degrees C under conditions that heat-induced radiosensitization was reduced. In contrast, the masking effect was not altered in OC-14 cells exposed to 45 degrees C, conditions under which heat-induced radiosensitization was similar to that observed in wild-type HA-1 cells. These results suggest that a reduction in the masking effect is associated with a reduction of the magnitude of heat-induced radiosensitization in the HR-1 and OC-14 heat-resistant cell lines. The reduction of the masking effect in the cell lines resistant to heat-induced radiosensitization was associated with neither a reduction in the magnitude of the heat-induced increase in total nuclear protein content nor major differences in the protein profiles of the nucleoids isolated from heated cells.
本文研究了从同一野生型HA-1细胞系分离得到的两种中国仓鼠耐热细胞系HR-1和OC-14中的热诱导放射增敏作用。研究发现，HR-1和OC-14细胞在暴露于43℃后，热诱导放射增敏的程度降低；HR-1细胞在暴露于45℃后也有类似程度的降低，但OC-14细胞没有。还使用荧光晕圈试验研究了热暴露对一类抑制核DNA超螺旋变化能力的电离辐射诱导的DNA损伤的影响。在照射前暴露于43℃或45℃的野生型细胞具有介于对照细胞和未加热细胞之间的DNA复绕能力，这一现象先前被描述为掩盖效应。在热诱导放射增敏降低的条件下，暴露于43℃或45℃的HR-1细胞或暴露于43℃的OC-14细胞中，这种掩盖效应显著降低。相比之下，暴露于45℃的OC-14细胞中的掩盖效应没有改变，在这种条件下热诱导放射增敏与野生型HA-1细胞中观察到的相似。这些结果表明，掩盖效应的降低与HR-1和OC-14耐热细胞系中热诱导放射增敏程度的降低有关。在对热诱导放射增敏有抗性的细胞系中，掩盖效应的降低既不与热诱导的总核蛋白含量增加幅度的降低有关，也不与从加热细胞中分离的类核的蛋白质谱的主要差异有关。
