Marshall Kathryn M, Matsumoto Sandra S, Holden Joseph A, Concepción Gisela P, Tasdemir Deniz, Ireland Chris M, Barrows Louis R
Department of Pharmacology and Toxicology, 30 S. 2000 E. Rm. 201, Salt Lake City, UT 84112, USA.
Biochem Pharmacol. 2003 Aug 1;66(3):447-58. doi: 10.1016/s0006-2952(03)00209-0.
Topoisomerase IIalpha (top2) is a target of some of the most useful anticancer drugs. All clinically approved top2 drugs act to stabilize a drug-enzyme-DNA cleavable complex. Here we report the novel top2 activity of neoamphimedine, an isomer of the marine pyridoacridine amphimedine. Neoamphimedine was cytotoxic in yeast and mammalian cell lines. Neoamphimedine exhibited enhanced toxicity in top2 over-expressing yeast cells and was toxic in every mammalian cell line tested. However, neoamphimedine did not possess enhanced toxicity in a mammalian cell line sensitive to stabilized cleavable complexes. Therefore, we hypothesized that neoamphimedine is a top2-dependent drug, whose primary mechanism of action is not the stabilization of cleavable complexes. Top2-directed activity was determined in purified enzyme systems. Neoamphimedine-induced catenation of plasmid DNA only in the presence of active top2. This catenation correlated with the ability of neoamphimedine to aggregate DNA. Catenation was also observed using a filter-binding assay and transmission electron microscopy. Catenation was confirmed when only restriction enzyme digestion could resolve the catenated plasmid complex to monomer length plasmid DNA. Neoamphimedine also showed potent anti-neoplastic activity in human xenograft tumors in athymic mice. Neoamphimedine was as effective as etoposide in mice bearing KB tumors and as effective as 9-aminocamptothecin in mice bearing HCT-116 tumors. Amphimedine did not induce DNA aggregation or catenation in vitro, nor did it display any significant anti-neoplastic activity. These results suggest that neoamphimedine has a novel top2-mediated mechanism of cytotoxicity and anticancer potential.
拓扑异构酶IIα（top2）是一些最有效的抗癌药物的作用靶点。所有临床批准的top2药物都能稳定药物 - 酶 - DNA可裂解复合物。在此我们报告了新安菲美定（neoamphimedine）的新型top2活性，它是海洋吡啶吖啶安菲美定（amphimedine）的一种异构体。新安菲美定在酵母和哺乳动物细胞系中具有细胞毒性。新安菲美定在top2过表达的酵母细胞中表现出增强的毒性，并且在所有测试的哺乳动物细胞系中均有毒性。然而，新安菲美定在对稳定的可裂解复合物敏感的哺乳动物细胞系中并未表现出增强的毒性。因此，我们推测新安菲美定是一种依赖top2的药物，其主要作用机制不是稳定可裂解复合物。在纯化的酶系统中测定了top2导向的活性。新安菲美定仅在活性top2存在的情况下诱导质粒DNA的连环化。这种连环化与新安菲美定聚集DNA的能力相关。使用滤膜结合试验和透射电子显微镜也观察到了连环化。当只有限制性内切酶消化能够将连环化的质粒复合物分解为单体长度的质粒DNA时，连环化得到了证实。新安菲美定在无胸腺小鼠的人异种移植肿瘤中也显示出强大的抗肿瘤活性。在携带KB肿瘤的小鼠中，新安菲美定与依托泊苷的效果相当，在携带HCT - 116肿瘤的小鼠中，其效果与9 - 氨基喜树碱相当。安菲美定在体外不诱导DNA聚集或连环化，也没有显示出任何显著的抗肿瘤活性。这些结果表明，新安菲美定具有一种新型的top2介导的细胞毒性机制和抗癌潜力。
