Lown J W, Hanstock C C, Bradley R D, Scraba D G
Mol Pharmacol. 1984 Jan;25(1):178-84.
The interactions of the low cardiotoxic antitumor agents 1,4-dihydroxy-5,8-bis[[2-[(2-hydroxyethyl)amino]ethyl]amino]-9, 10-anthracenedione (mitoxantrone) and 9,10-anthracenedicarboxaldehyde bis[(4,5-dihydro-1H-imidazoyl-2-yl)hydrazone] (bisantrene) with pBR322 and PM2 DNA have been examined by electron microscopy. Direct evidence was obtained for intercalative binding of both drugs, with mitoxantrone causing a 13% average length increase in pBR322 corresponding to approximately 580 drug molecules per circle at saturation and bisantrene causing an 11% increase in length corresponding to approximately 480 drug molecules bound per circle. Considerations of the known GC preference for non-nearest neighbor binding of the drugs and inspection of the known sequence of pBR322 suggest that the available intercalation sites are occupied and that additional external electrostatic binding of the cationic drugs also occurs. An apparent difference in behavior of mitoxantrone as compared with that of bisantrene in causing no net increase in length of supercoiled pBR322 was shown to be attributable to an offsetting compaction due to extensive supercoiling by mitoxantrone molecules. This conclusion was confirmed by independent experiments with PM2 covalently closed-circular DNA--both native, negatively supercoiled and relaxed--with calf thymus topoisomerase, using ethidium for comparison. Ethidium caused a 21.3 +/- 3.6% length increase in nicked, open-circular PM2-DNA, or 2100 molecules bound per 10,300 base pairs. Mitoxantrone caused a 16.6% length increase in nicked PM2-DNA equivalent to approximately 1700 drug molecules per circle. Electron microscopic measurements on relaxed PM2-DNA with progressively increasing proportions of mitoxantrone (from 1.4:1 to 14:1 drug molecules per base pair) revealed the onset of formation of lacelike networks of DNA circles linked together. This phenomenon, which is not produced by bisantrene, is attributed to inter-DNA links by the charged side arms of mitoxantrone and is in accord with previous reports that mitoxantrone causes severe compaction and distortion of chromatin. Electron microscopic examination of the interaction of six additional mitoxantrone derivatives, two of which produced lacelike DNA networks, revealed strict structural requirements for this phenomenon.
通过电子显微镜研究了低心脏毒性抗肿瘤药物1,4 - 二羟基 - 5,8 - 双[[2 - [(2 - 羟乙基)氨基]乙基]氨基] - 9,10 - 蒽二酮（米托蒽醌）和9,10 - 蒽二甲醛双[(4,5 - 二氢 - 1H - 咪唑 - 2 - 基)腙]（双胺苯吖啶）与pBR322和PM2 DNA的相互作用。获得了两种药物嵌入结合的直接证据，米托蒽醌使pBR322的平均长度增加13%，饱和时每圈约对应580个药物分子，双胺苯吖啶使长度增加11%，每圈约对应480个结合的药物分子。考虑到药物对非紧邻碱基结合已知的GC偏好以及对pBR322已知序列的检查表明，可用的嵌入位点已被占据，并且阳离子药物还发生了额外的外部静电结合。与双胺苯吖啶相比，米托蒽醌在导致超螺旋pBR322的长度没有净增加方面表现出明显差异，这被证明是由于米托蒽醌分子广泛超螺旋导致的抵消性压缩所致。用小牛胸腺拓扑异构酶对PM2共价闭环DNA（包括天然的、负超螺旋的和松弛的）进行的独立实验，以溴化乙锭作为对照，证实了这一结论。溴化乙锭使切口的、开环的PM2 - DNA长度增加21.3±3.6%，即每10300个碱基对结合2100个分子。米托蒽醌使切口的PM2 - DNA长度增加16.6%，每圈约相当于1700个药物分子。对松弛的PM2 - DNA进行电子显微镜测量，随着米托蒽醌比例逐渐增加（从每碱基对1.4:1到14:1药物分子），发现开始形成由相连的DNA环组成的花边状网络。这种双胺苯吖啶不会产生的现象归因于米托蒽醌带电荷的侧臂导致的DNA间连接，这与之前关于米托蒽醌导致染色质严重压缩和扭曲的报道一致。对另外六种米托蒽醌衍生物相互作用的电子显微镜检查，其中两种产生了花边状DNA网络，揭示了这种现象的严格结构要求。
