Horiguchi-Yamada Junko, Iwase Satsuki, Kawano Takeshi, Yamada Hisashi
Departments of Oncology, Institute of DNA Medicine, Jikei University School of Medicine, Minato-ku, Tokyo 105-8461, Japan.
Anticancer Res. 2005 Jul-Aug;25(4):2631-8.
Interferon (IFN) potentiates cytotoxicity by X-ray irradiation. To elucidate the mechanism of this potentiation, the biological markers related to DNA damage and cell survival were studied.
IFN-alpha-sensitive Daudi and its resistant cells were used. Survival after treatment was assessed by clonogenic assays. DNA breaks were studied by pulse-field gel electrophoresis (PFGE). Production of reactive oxygen metabolites was measured using flow cytometry. Messenger RNA and protein were examined by RT-PCR and immunoblot, respectively.
IFN-alpha treatment for 24 h before irradiation potentiated the sensitivity of Daudi cells to X-rays. This combination induced 50 kb DNA fragmentation and activated caspase-3 in Daudi cells. Pretreatment with IFN-alpha inhibited the production of reactive oxygen species by irradiation. IFN-alpha pretreatment down-regulated most of the double-strand break (DSB) repair-related mRNAs, but did not affect the repair of DSBs studied by PFGE. The induction and phosphorylation of p21(Cip1/WAF1) (p21) was prominently suppressed in cells pretreated with IFN-a.
Pretreatment with IFN-alpha potentiates the cytotoxic effects of X-rays. Inhibition of X-ray-induced p21 may cause the augmented sensitivity by IFN-alpha pretreatment.
干扰素（IFN）可增强X射线照射的细胞毒性。为阐明这种增强作用的机制，对与DNA损伤和细胞存活相关的生物学标志物进行了研究。
使用对IFN-α敏感的Daudi细胞及其耐药细胞。通过克隆形成试验评估处理后的细胞存活率。采用脉冲场凝胶电泳（PFGE）研究DNA断裂情况。使用流式细胞术检测活性氧代谢产物的产生。分别通过逆转录聚合酶链反应（RT-PCR）和免疫印迹法检测信使核糖核酸（mRNA）和蛋白质。
照射前用IFN-α处理24小时可增强Daudi细胞对X射线的敏感性。这种联合处理诱导Daudi细胞出现50 kb的DNA片段化并激活半胱天冬酶-3。IFN-α预处理可抑制照射诱导的活性氧生成。IFN-α预处理下调了大多数与双链断裂（DSB）修复相关的mRNA，但不影响通过PFGE研究的DSB修复。在用IFN-α预处理的细胞中，p21（Cip1/WAF1）（p21）的诱导和磷酸化受到显著抑制。
IFN-α预处理可增强X射线的细胞毒性作用。抑制X射线诱导的p21可能是IFN-α预处理导致敏感性增强的原因。
