Human promyelogenous leukaemic cells (HL-60) were treated with novel spermine analogue, (S)-N1-(2-methyl-1-butyl)-N11-ethyl-4,8-diazaundecane (IPENSpm), and the effects on growth and intracellular polyamine metabolism were measured. IPENSpm was cytotoxic to these cells at concentrations greater than 2.5μM. It induced apoptosis in a caspase-dependent manner and its toxicity profile was comparable with etoposide, a well-known anti-tumour agent and inducer of apoptosis. IPENSpm decreased intracellular polyamine content as a result of changes in ornithine decarboxylase activity and increases in spermidine/spermine N1-acetyltransferase and polyamine export. Analysis showed spermine and spermidine as the major intracellular polyamines, while putrescine and acetyl-polyamines were the main export compounds. IPENSpm used the polyamine transporter system for uptake and its accumulation in cells was prevented by polyamine transport inhibitors. IPENSpm can be classified as a polyamine anti-metabolite and it may be a promising new lead compound in terms of treatment of some human cancers.
Abbreviations used: IPENSpm, (S)-N1-(2-methyl-1-butyl)-N11-ethyl-4,8-diazaundecane; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; ODC, ornithine decarboxylase; SSAT, spermidine/spermine N1-acetyltransferase.