Effect of 6-Aminonicotinamide and Other Protein Synthesis Inhibitors on Formation of Platinum-DNA Adducts and Cisplatin Sensitivity
作者:I. Imawati Budihardjo、Scott A. Boerner、Steven Eckdahl、Phyllis A. Svingen、Robert Rios、Matthew M. Ames、Scott H. Kaufmann
DOI:10.1124/mol.57.3.529
日期:2000.3.1
The present study was undertaken to examine the mechanistic basis for the recent observation that the pyridine nucleotide derivative 6-aminonicotinamide (6AN, NSC 21206) enhances the accumulation and resulting cytotoxicity of cisplatin in a variety of tumor cell lines. When A549 lung cancer cells or K562 leukemia cells were treated with 62.5 μM 6AN for 21 h and then pulse-labeled with [35S]methionine for 1 h, increased labeling of five polypeptides, one of which corresponded to a M r ∼78,000 glucose-regulated protein (GRP78), was observed. Two subsequent observations, however, suggested that up-regulation of these polypeptides was unlikely to explain the interaction between 6AN and cisplatin: 1) the concentration of 6AN required to induce GRP78 was 4-fold higher than the dose required to sensitize cells to cisplatin; and 2) simultaneous treatment of cells with 6AN and cycloheximide prevented the increase in GRP78 but not the sensitizing effect of 6AN. On the contrary, treatment with the protein synthesis inhibitors cycloheximide, anisomycin, or puromycin as well as prolonged exposure to the RNA synthesis inhibitor actinomycin D mimicked the biochemical modulating effects of 6AN on cisplatin action. Conversely, 6AN inhibited protein synthesis, whereas 18 6AN analogs that failed to enhance Pt-DNA adducts and cisplatin cytotoxicity failed to inhibit protein synthesis. These observations are consistent with a model in which 6AN and other inhibitors of protein synthesis act as modulating agents by increasing cisplatin accumulation, thereby enhancing the formation of Pt-DNA adducts and subsequent cisplatin-induced cell death.
最近观察到吡啶核苷酸衍生物 6-氨基烟酰胺(6AN,NSC 21206)可增强顺铂在多种肿瘤细胞系中的蓄积和由此产生的细胞毒性,本研究就是为了研究这一观察结果的机理基础。用 62.5 μM 6AN 处理 A549 肺癌细胞或 K562 白血病细胞 21 小时,然后用[35S]蛋氨酸脉冲标记 1 小时,观察到五种多肽的标记增加,其中一种对应于 M r ∼ 78,000 葡萄糖调节蛋白(GRP78)。然而,随后的两个观察结果表明,这些多肽的上调不太可能解释 6AN 与顺铂之间的相互作用:1)诱导 GRP78 所需的 6AN 浓度比使细胞对顺铂敏感所需的剂量高 4 倍;2)同时用 6AN 和环己亚胺处理细胞可防止 GRP78 的增加,但不能防止 6AN 的敏感效应。相反,用蛋白质合成抑制剂环己亚胺、安乃近或嘌呤霉素处理细胞,以及长时间暴露于 RNA 合成抑制剂放线菌素 D,可模拟 6AN 对顺铂作用的生化调节作用。相反,6AN抑制蛋白质合成,而18种6AN类似物不能增强Pt-DNA加合物和顺铂的细胞毒性,也不能抑制蛋白质合成。这些观察结果符合这样一种模式:6AN 和其他蛋白质合成抑制剂通过增加顺铂的积累,从而增强 Pt-DNA 加合物的形成和随后由顺铂诱导的细胞死亡,起到调节剂的作用。