Sai Krishna A D, Panda Gayatri, Kondapi Anand K
Department of Biochemistry, University of Hyderabad, India.
Arch Biochem Biophys. 2005 Jun 15;438(2):206-16. doi: 10.1016/j.abb.2005.04.014.
Topoisomerase II is found to be present in two isoforms alpha and beta, and both the isoforms are regulated in cancerous tissue. Development of isoform-specific topoisomerase II poisons has been of great interest for cancer-specific drug targeting. In the present investigation using quantitative structure-activity analysis of ferrocene derivatives, we show that two derivatives of ferrocene, azalactone ferrocene and thiomorpholide amido methyl ferrocene, can preferentially inhibit topoisomerase IIbeta activity. Thiomorpholide amido methyl ferrocene shows higher inhibition of catalytic activity (IC(50) = 50 microM) against topoisomerase IIbeta compared to azalactone ferrocene (IC(50) = 100 microM). The analysis of protein DNA intermediates formed in the presence of these two compounds suggests that azalactone ferrocene readily induces formation of cleavable complex in a dose-dependent manner, in comparison with thiomorpholide amido methyl ferrocene. Both the compounds show significant inhibition of DNA-dependent ATPase activity of enzyme. These results suggest that azalactone ferrocene inhibits DNA passage activity of enzyme leading to the formation of cleavable complex, while thiomorpholide amido methyl ferrocene competes with ATP binding resulting in the inhibition of catalytic activity of enzyme. In summary, thiomorpholide amido methyl ferrocene and azalactone ferrocene show distinctly different mechanisms in inhibition of catalytic activity of topoisomerase IIbeta.
拓扑异构酶II存在α和β两种同工型，且这两种同工型在癌组织中均受到调控。开发同工型特异性的拓扑异构酶II抑制剂对于癌症特异性药物靶向治疗具有重大意义。在本研究中，通过对二茂铁衍生物进行定量构效分析，我们发现二茂铁的两种衍生物，氮杂内酯二茂铁和硫代吗啉酰胺甲基二茂铁，能够优先抑制拓扑异构酶IIβ的活性。与氮杂内酯二茂铁（IC50 = 100 μM）相比，硫代吗啉酰胺甲基二茂铁对拓扑异构酶IIβ的催化活性具有更高的抑制作用（IC50 = 50 μM）。对在这两种化合物存在下形成的蛋白质-DNA中间体的分析表明，与硫代吗啉酰胺甲基二茂铁相比，氮杂内酯二茂铁能够以剂量依赖性方式轻易诱导可裂解复合物的形成。这两种化合物均对该酶的DNA依赖性ATP酶活性表现出显著抑制作用。这些结果表明，氮杂内酯二茂铁抑制该酶的DNA通过活性，导致可裂解复合物的形成，而硫代吗啉酰胺甲基二茂铁与ATP结合竞争，从而抑制该酶的催化活性。总之，硫代吗啉酰胺甲基二茂铁和氮杂内酯二茂铁在抑制拓扑异构酶IIβ催化活性方面表现出明显不同的机制。
