Discipline of Pathology, University of Sydney, Sydney, New South Wales, Australia.
Mol Pharmacol. 2012 Jul;82(1):105-14. doi: 10.1124/mol.112.078964. Epub 2012 Apr 16.
Thiosemicarbazones are a group of compounds that have received comprehensive investigation as anticancer agents. The antitumor activity of the thiosemicarbazone, 3-amino-2-pyridinecarboxaldehyde thiosemicarbazone (3-AP; triapine), has been extensively assessed in more than 20 phase I and II clinical trials. These studies have demonstrated that 3-AP induces methemoglobin (metHb) formation and hypoxia in patients, limiting its usefulness. Considering this problem, we assessed the mechanism of metHb formation by 3-AP compared with that of more recently developed thiosemicarbazones, including di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT). This was investigated using intact red blood cells (RBCs), RBC lysates, purified oxyhemoglobin, and a mouse model. The chelation of cellular labile iron with the formation of a redox-active thiosemicarbazone-iron complex was found to be crucial for oxyhemoglobin oxidation. This observation was substantiated using a thiosemicarbazone that cannot ligate iron and also by using the chelator, desferrioxamine, that forms a redox-inactive iron complex. Of significance, cellular copper chelation was not important for metHb generation in contrast to its role in preventing tumor cell proliferation. Administration of Dp44mT to mice catalyzed metHb and cardiac metmyoglobin formation. However, ascorbic acid administered together with the drug in vivo significantly decreased metHb levels, providing a potential therapeutic intervention. Moreover, we demonstrated that the structure of the thiosemicarbazone is of importance in terms of metHb generation, because the DpT analog, di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), does not induce metHb generation in vivo. Hence, DpC represents a next-generation thiosemicarbazone that possesses markedly superior properties. This investigation is important for developing more effective thiosemicarbazone treatment regimens.
硫代氨基甲脒类化合物是一类受到广泛研究的抗癌药物。3-氨基-2-吡啶甲醛缩氨基硫脲（3-AP；三嗪）的抗肿瘤活性已在超过 20 项的 I 期和 II 期临床试验中得到广泛评估。这些研究表明，3-AP 会在患者体内诱导高铁血红蛋白（metHb）形成和缺氧，限制了其应用。鉴于此问题，我们评估了 3-AP 与最近开发的硫代氨基甲脒类化合物（包括二吡啶酮-4,4-二甲基-3-硫代氨基甲脒（Dp44mT））形成 metHb 的机制。这是通过使用完整的红细胞（RBC）、RBC 裂解物、纯化的氧合血红蛋白和小鼠模型进行研究的。发现细胞内不稳定铁的螯合作用与形成具有氧化还原活性的硫代氨基甲脒-铁络合物对于氧合血红蛋白的氧化至关重要。这一观察结果通过使用不能结合铁的硫代氨基甲脒和形成氧化还原非活性铁络合物的螯合剂去铁胺得到证实。重要的是，与防止肿瘤细胞增殖的作用相反，细胞内铜螯合对于 metHb 的生成并不重要。与药物一起在体内给予 Dp44mT 会催化 metHb 和心脏 metmyoglobin 的形成。然而，体内给予抗坏血酸与药物一起显著降低了 metHb 水平，提供了一种潜在的治疗干预措施。此外，我们证明了硫代氨基甲脒的结构在生成 metHb 方面很重要，因为 DpT 类似物，二吡啶酮-4-环己基-4-甲基-3-硫代氨基甲脒（DpC），不会在体内引起 metHb 的生成。因此，DpC 代表了一种具有明显优越特性的下一代硫代氨基甲脒。这项研究对于开发更有效的硫代氨基甲脒治疗方案非常重要。
