Computer graphics modeling and physicochemical studies of
spermine-
DNA interactions, as well as experiments in cell culture, indicate that a
polyamine analogue with strong affinity for
nucleic acids but poor ability to condense and aggregate
DNA in vitro should act as an antiproliferative agent if it can enter cells. On the basis of our studies of
polyamine-
DNA interactions, we designed a
pentamine, 1,19-bis(ethylamino)-5,10,15- triazanonadecane (BE-4-4-4-4), that had these characteristics. Measurement of melting temperature and ultraviolet light scattering studies show that the affinity of this analogue for
calf-thymus DNA is about 4 times higher than that of
spermine, whereas its ability to aggregate
DNA is slightly poorer than that of
spermine. Studies in U-87 MG, U-251 MG, SF-126, SF-188, SF-763, SF-767, and DAOY human
brain tumor cells in tissue culture showed that treatment for more than 96 h with concentrations of 5 microM
BE-4-4-4-4 or greater inhibited growth; decreased levels of
putrescine,
spermidine, and
spermine; and decreased colony-forming ability in all cell lines. The cytotoxicity of the analogue varied among cell lines; DAOY and SF-767 were the most sensitive and the most resistant lines, respectively. In SF-763 cells, growth inhibition by
BE-4-4-4-4 could be partially reversed by the addition of
putrescine,
spermidine, or
spermine 1 day after
BE-4-4-4-4 addition, but in U-251 MG cells, growth inhibition was reversed only by
spermine and not by other
polyamines. When any of the naturally occurring
polyamines was added simultaneously with
BE-4-4-4-4, growth inhibition was completely blocked. The data suggest that a threshold intracellular concentration of
BE-4-4-4-4 is needed to manifest the growth-inhibitory and cytotoxic effects. In most cell lines, once that threshold level is reached, the growth-inhibitory and cytotoxic properties of the analogue are manifest irrespective of cellular
polyamine levels. Further increases in the
BE-4-4-4-4 concentration or incubation time reduce the intracellular
polyamine levels but do not significantly increase growth inhibition. In U-87 MG and DAOY cells, however, prolonged incubation with higher concentrations of
BE-4-4-4-4 causes additional growth inhibition along with depletion of intracellular
polyamines.(ABSTRACT TRUNCATED AT 400 WORDS)