Paul L A, Fulton A M, Heppner G H
Department of Immunology, Michigan Cancer Foundation, Detroit.
Mutat Res. 1989 Dec;215(2):223-34. doi: 10.1016/0027-5107(89)90187-5.
We have shown, in a preliminary report, that macrophages can induce strand breaks in the DNA of co-cultured tumor cells (Chong et al., 1988). The present study is designed to determine if oxygen-centered species generated by the cell-free enzyme-substrate combination of hypoxanthine and xanthine oxidase can induce similar lesions and to identify the specific mediator(s). We report that co-incubation of murine mammary tumor cell lines with hypoxanthine and xanthine oxidase leads to the induction of DNA-strand breaks as determined by fluorescence analysis of DNA unwinding (FADU) assay or alkaline elution techniques. This damage is preventable by catalase which removes hydrogen peroxide but no protection is provided by agents to remove or prevent the formation of superoxide anion (superoxide dismutase), or hydroxyl radical (mannitol or the iron chelator o-phenanthroline). Likewise, cyclooxygenase or lipoxygenase inhibitors of arachidonate metabolism (indomethacin, nordihydroguaiaretic acid, caffeic acid) or bromophenacyl bromide do not alter the degree of DNA scission. Treatment with higher doses of oxygen species leads to significant toxicity as determined by evaluation of cell growth potential or colony-forming ability. Again, toxicity is prevented only by the presence of catalase. Tumor cells are able to rejoin strand breaks at lower, less toxic doses. When comparing different tumor cell subpopulations at various stages of progression, i.e., metastatic vs. nonmetastatic, for sensitivity to hydrogen peroxide-induced strand breakage, we found that at lower concentrations (less than 5 microM) metastatic populations are sensitive whereas nonmetastatic populations exhibit no significant breakage. At higher concentrations of hydrogen peroxide, all lines were sensitive, suggesting that a lower threshold of sensitivity may exist for more progressed tumor cell lines.
我们在一份初步报告中指出，巨噬细胞可诱导共培养的肿瘤细胞DNA发生链断裂（Chong等人，1988年）。本研究旨在确定次黄嘌呤与黄嘌呤氧化酶的无细胞酶 - 底物组合所产生的以氧为中心的物质是否能诱导类似损伤，并鉴定特定的介质。我们报告，通过DNA解旋荧光分析（FADU）测定法或碱性洗脱技术确定，将小鼠乳腺肿瘤细胞系与次黄嘌呤和黄嘌呤氧化酶共同孵育会导致DNA链断裂的诱导。过氧化氢酶可消除过氧化氢，从而预防这种损伤，但去除或防止超氧阴离子（超氧化物歧化酶）或羟基自由基（甘露醇或铁螯合剂邻菲罗啉）形成的试剂则不能提供保护。同样，花生四烯酸代谢的环氧化酶或脂氧化酶抑制剂（吲哚美辛、去甲二氢愈创木酸、咖啡酸）或溴苯甲酰溴不会改变DNA断裂的程度。通过评估细胞生长潜力或集落形成能力确定，用更高剂量的氧物质处理会导致显著毒性。同样，只有过氧化氢酶的存在才能预防毒性。肿瘤细胞能够在较低、毒性较小的剂量下重新连接链断裂。在比较处于不同进展阶段的不同肿瘤细胞亚群，即转移性与非转移性亚群对过氧化氢诱导的链断裂的敏感性时，我们发现，在较低浓度（小于5 microM）下，转移性亚群敏感，而非转移性亚群则无明显断裂。在过氧化氢浓度较高时，所有细胞系均敏感，这表明进展程度更高的肿瘤细胞系可能存在较低的敏感性阈值。
