Richardson D, Ponka P, Baker E
Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, Montreal, Quebec, Canada.
Cancer Res. 1994 Feb 1;54(3):685-9.
The mechanism of action of the clinically used iron(III) chelator, desferrioxamine (DFO), on preventing iron (Fe) uptake from transferrin (Tf) has been investigated using the human melanoma cell line SK-MEL-28. This investigation was initiated due to the paucity of information on the mechanisms of action of DFO in neoplastic cells and because recent studies have suggested that DFO may be a useful antitumor agent. The effect of DFO was dependent on incubation time. After a 2-h incubation, DFO acted like the extracellular chelators, EDTA and diethylenetriaminepentaacetic acid, because there was little inhibition of 59Fe uptake from Tf. In contrast, after a 24-h incubation, DFO (0.5 mM) efficiently reduced internalized 59Fe uptake from Tf to 18% of the control value. These observations suggested the existence of a kinetic block to the entry of the apochelator to intracellular Fe pools and/or to the exit of the DFO-59Fe complex. Indeed, cellular fractionation demonstrated that, in contrast to the decrease in the percentage of 59Fe in the ferritin and membrane fractions, a marked increase in the percentage of 59Fe present in the ferritin-free cytosol occurred. These observations suggested an accumulation of the DFO-59Fe complex within the cell. The highly lipophilic Fe chelator, pyridoxal isonicotinoyl hydrazone, was far more effective than DFO at preventing 59Fe uptake from Tf, illustrating the importance of membrane permeability for effective Fe chelation. Desferrioxamine at a concentration of 1 mM decreased internalized 125I-Tf uptake to 70% of the control. However, the decrease in 59Fe uptake observed could only be partially accounted for by a decrease in Tf uptake, and it appeared that DFO was chelating 59Fe at an intracellular site consistent with the transit Fe pool. The results are discussed in the context of the use of Fe chelators as effective antineoplastic agents.
利用人黑色素瘤细胞系SK-MEL-28，对临床使用的铁（III）螯合剂去铁胺（DFO）阻止从转铁蛋白（Tf）摄取铁（Fe）的作用机制进行了研究。开展这项研究是因为关于DFO在肿瘤细胞中的作用机制的信息匮乏，而且近期研究表明DFO可能是一种有用的抗肿瘤药物。DFO的作用效果取决于孵育时间。孵育2小时后，DFO的作用类似于细胞外螯合剂乙二胺四乙酸（EDTA）和二乙烯三胺五乙酸，因为从Tf摄取59Fe几乎没有受到抑制。相反，孵育24小时后，DFO（0.5 mM）能有效地将从Tf内化的59Fe摄取量降低至对照值的18%。这些观察结果表明，脱铁螯合剂进入细胞内铁池和/或DFO-59Fe复合物排出存在动力学障碍。实际上，细胞分级分离表明，与铁蛋白和膜组分中59Fe百分比的降低相反，无铁蛋白的胞质溶胶中59Fe的百分比显著增加。这些观察结果表明细胞内存在DFO-59Fe复合物的积累。高度亲脂性的铁螯合剂吡啶醛异烟酰腙在阻止从Tf摄取59Fe方面比DFO有效得多，这说明了膜通透性对有效铁螯合的重要性。浓度为1 mM的去铁胺将内化的125I-Tf摄取量降低至对照值的70%。然而，观察到的59Fe摄取量的降低只能部分归因于Tf摄取量的减少，而且似乎DFO在与转运铁池一致的细胞内位点螯合59Fe。将结合铁螯合剂作为有效的抗肿瘤药物的应用来讨论这些结果。
