Ngo E O, Nutter L M, Sura T, Gutierrez P L
Department of Pharmacology, University of Minnesota, 435 Delaware Street SE, Minneapolis, Minnesota 55455, USA.
Chem Res Toxicol. 1998 Apr;11(4):360-8. doi: 10.1021/tx9701945.
The biologic functions attributed to the nucleophosphoprotein p53 have been increasing in recent years. Some studies suggested that wild type p53 is responsible for cell cycle arrest brought about as a response to exposure of mammalian cells to DNA-damaging agents. This cell cycle arrest occurs in order for cells to repair the damaged macromolecules. Extensively damaged cells are also thought to undergo apoptosis via the p53-dependent or -independent signal transduction pathways. In this study, we investigated the ability of diaziridinylbenzoquinones to increase p53 levels in the human breast cancer cell line MCF-7. Diaziquone (AZQ), an anticancer agent, and its derivatives, diaziridinequinone (DZQ) and methyldiaziridinequinone (MeDZQ), induced p53 in a dose- and time-dependent manner as measured by the electrophoretic mobility shift assay. Wild type p53 induction by AZQ was suppressed when DT-diaphorase activity was inhibited by pretreating the cells with dicumarol. Aside from their potent alkylating activity, these agents also undergo redox cycling as evidenced by oxygen consumption and the production of reactive oxygen species (ROS). Inhibition of ROS production by the antioxidant enzyme catalase reduced AZQ- and DZQ-mediated p53 induction by about 45%. Thiotepa, a non-quinone aziridine-containing agent, and 1,4-benzoquinone (p-BQ), a redox cycling quinone, increased p53 levels. The nonalkylator oxygen-radical-generating agent menadione (MD) caused p53 induction only when MCF-7 cells were allowed to recover in drug-free media. On the basis of these data, we propose that the bioreductive activation of AZQ is a prerequisite for p53 induction. Moreover, the induction of p53 by AZQ requires both the quinone and the aziridine moieties of the AZQ molecule. Although AZQ and its analogues increased p53 levels in MCF-7 cells, p53 induction in these cells may not be responsible for the apoptosis seen upon treatment of MCF-7 cells with these agents. The uncoupling of p53 induction and apoptosis is evidenced by the generation of nucleosomal DNA laddering in aziridinequinone-treated T47D cells, a breast cancer cell line bearing a p53 mutation.
近年来，核磷蛋白p53的生物学功能不断增加。一些研究表明，野生型p53负责哺乳动物细胞暴露于DNA损伤剂后引起的细胞周期停滞。这种细胞周期停滞的发生是为了使细胞修复受损的大分子。广泛受损的细胞也被认为通过p53依赖性或非依赖性信号转导途径发生凋亡。在本研究中，我们研究了重氮烷基苯醌增加人乳腺癌细胞系MCF-7中p53水平的能力。抗癌剂重氮醌（AZQ）及其衍生物重氮喹啉（DZQ）和甲基重氮喹啉（MeDZQ），通过电泳迁移率变动分析测定，以剂量和时间依赖性方式诱导p53。当用双香豆素预处理细胞抑制DT-黄递酶活性时，AZQ对野生型p53的诱导作用受到抑制。除了其强大的烷基化活性外，这些药物还会进行氧化还原循环，耗氧和产生活性氧（ROS）证明了这一点。抗氧化酶过氧化氢酶抑制ROS产生使AZQ和DZQ介导的p53诱导降低约45%。硫替派，一种不含醌的氮丙啶类药物，以及1,4-苯醌（p-BQ），一种氧化还原循环醌，增加了p53水平。非烷化剂产生活性氧的药物甲萘醌（MD）仅在MCF-7细胞在无药物培养基中恢复时才引起p53诱导。基于这些数据，我们提出AZQ的生物还原激活是p53诱导的先决条件。此外，AZQ诱导p53需要AZQ分子的醌和氮丙啶部分。尽管AZQ及其类似物增加了MCF-7细胞中的p53水平，但这些细胞中p53的诱导可能与用这些药物处理MCF-7细胞时所见的凋亡无关。在氮丙啶醌处理的T47D细胞（一种携带p53突变的乳腺癌细胞系）中产生核小体DNA梯带证明了p53诱导与凋亡的解偶联。
