Role of crown-like side chains in the biological activity of substituted-phenoxazone drugs

The antitumour activity of a number of synthetic crown-ether analogues of a ctinomycin D (AMD) was investigated in order to test the role of side chain s that can complex metal cations, The AMD analogues consisted of two series of phenoxazone derivatives substituted with either benzo-15-crown-5 or ben zo-18-crown-6 and with different lengths of spacers between the crown group s and the phenoxazone chromophore. The biological activities of the synthet ic compounds were investigated by examination of drug-induced apoptosis and cell cycle perturbations in a human leukemia MOLT-3 cell line by flow cyto metry. A compound with dimethylaminopropyl side chains on the phenoxazone c hromophore was used as a control; this molecule was shown to intercalate in to DNA by UV-visible spectroscopy and was found to have considerable cytoto xic activity in the 1-9 muM concentration range, Compounds with five-member ed crown-ether side chains showed biological activity comparable with the c ontrol drug, whereas increasing the length of the spacers between the crown groups and the phenoxazone chromophore reduced the cytotoxic effect of the drugs, Compounds with six-membered crown-ether side chains reduced stabili zation of the DNA double helical structure and abolished biological activit y. Cell cycle alterations were observed only in drug systems which demonstr ated cytotoxic activity. Cell cycle regulation was found to be sensitive to minor modifications (elongation of the spacer by one methylene group) in t he side chains of the benzo-15-crown-5 derivatives, indicating that such se ries of synthetic drugs may serve as useful probes for investigation of cel l cycle regulation processes.