The long-lasting antiproliferative effect of 15-deoxyspergualin through its spermidine moiety.

15-Deoxyspergualin (DSG) inhibited growth of mouse EL-4 lymphoma cells with an IC50 0.02 microg/ml. Even though the cells were treated with DSG for only 4 hours and then washed, the antiproliferative effect lasted long with an IC50 0.4 microg/ml. DSG has spermidine and guanidine moieties in its structure. One decomposed element containing guanidine moiety inhibited the growth at higher doses than DSG, but the effect did not last long unlike DSG. While another element containing spermidine moiety did not affect the growth, it diminished the long-lasting antiproliferative effect of DSG by pretreatment of the cells. Pretreatment with polyamines such as putrescine, spermidine, and spermine also diminished the effect of DSG. Furthermore, N-alkylation of spermidine moiety in DSG abolished the antiproliferative effect. These results suggested that DSG binds to the cells through its spermidine moiety and exerts its long-lasting antiproliferative effect.