Maebayashi K, Mitsuhashi N, Takahashi T, Sakurai H, Niibe H
Department of Radiology and Radiation Oncology, Gunma University School of Medicine, Maebashi, Japan.
Int J Radiat Oncol Biol Phys. 1999 Jun 1;44(3):677-82. doi: 10.1016/s0360-3016(99)00025-5.
We reported that two established rat yolk sac tumor cell lines differ in their radiosensitivity by 1.7 fold, and the variation is most likely manifested by the differences seen in their apoptotic response. We investigated the relationship between radiosensitivity and p53 in these cell lines.
We assessed the status of p53 in cell lines by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and sequence analysis, and also analyzed protein expression of p53, p21, and bax as a function of time after irradiation to determine the signal transduction for p53 by immunoblotting.
A band shift was observed only in exon 7 for the radioresistant NMT-1R cells and no band shift was detected for the radiosensitive NMT-1 cells. A band shift was confirmed also at the mRNA level. Exon 7 of p53 DNA showed a three base substitution of DNA at codon 267 to 268. Expression of p53, p21, and bax proteins in NMT-1R cells did not change after 10 Gy irradiation; however, in NMT-1 cells, the expression of these proteins was increased from 1-12 h after irradiation.
A loss of p53 function by radiation-induced mutation of p53 decreased the radiosensitivity in these cell lines.
我们报道了两种已建立的大鼠卵黄囊瘤细胞系的放射敏感性相差1.7倍，这种差异很可能通过它们凋亡反应的差异表现出来。我们研究了这些细胞系中放射敏感性与p53之间的关系。
我们通过聚合酶链反应-单链构象多态性（PCR-SSCP）和序列分析评估细胞系中p53的状态，并通过免疫印迹分析照射后不同时间p53、p21和bax的蛋白表达，以确定p53的信号转导。
仅在放射抗性的NMT-1R细胞的第7外显子中观察到条带迁移，而放射敏感的NMT-1细胞未检测到条带迁移。在mRNA水平也证实了条带迁移。p53 DNA的第7外显子在密码子267至268处出现三个碱基替换。10 Gy照射后，NMT-1R细胞中p53、p21和bax蛋白的表达没有变化；然而，在NMT-1细胞中，这些蛋白的表达在照射后1至12小时增加。
p53辐射诱导突变导致的p53功能丧失降低了这些细胞系的放射敏感性。
