ANTIPROLIFERATIVE EFFECTS OF N-1,N-4-DIBENZYLPUTRESCINE IN HUMAN AND RODENT TUMOR-CELLS

Polyamines (putrescine, spermidine and spermine) increase in prolifera ting tissues and are essential for cellular growth and cell division p rocesses. We had previously shown that alkyl substituted putrescines c an inhibit cell proliferation. We now tested the effects of the N-alph a,N-omega-dibenzyl derivatives of the simple diamines putrescine, cada verine and 1,3-diaminopropane on the growth of three human squamous ce ll carcinoma (SCC) lines and a rat hepatoma (H-4-II-E) cell line. Surv ival assays were measured by treating exponentially-growing SCC cultur es with N-1,N-4-dibenzylputrescine (DBP) (270 mu M) or a rat hepatoma cell culture with DBP (100 mu M) for 48 hrs. Inhibition of cell growth was measured either by the colony forming assay or by cell counting. DBP inhibited proliferation of the rat hepatoma (H-4-II-E) cell line a nd induced cytotoxicity when used at a concentration of 100 mu M for > 48 hrs. N-1,N-5-dibenzylcadaverine (DBC) also induced cytotoxicity at a similar concentration, while N-1,N-3-dibenzyl-1,3-diaminopropane (DB Pr) was a much weaker inhibitor of cell growth. Inhibition of cell gro wth by DBP resulted in marked modifications of cell morphology, such a s vacuole formation, decrease in size, pycnosis, change in staining be havior toward trypan blue and lack of adherence. DBP was also growth i nhibitory in the three human SCC cell lines tested. The concentration of DBP required to achieve growth inhibition of SCC cells could be dra matically decreased in the presence of N-1,N-4-bis(buta-2,3dienyl)buta nediamine, a specific inhibitor of polyamine oxidase (PAOI). Moreover, although the presence of PAOI only prevented the oxidation (debenzyla tion) of approximately 20% of intracellular DBP over a 5-day period, i t produced a 5-fold increase in the inhibition of cell proliferation b y DBP. DBP (and DEC) inhibited putrescine uptake by rat hepatoma (H-4- II-E) cells in what appears to be a competitive reaction. A tenfold ex cess of putrescine over DBP did not inhibit the antiproliferative or c ytotoxic effects of the latter. DBP administered for 72 hrs. depleted intracellular levels of putrescine, spermidine and spermine in the SCC lines by 50-100% of control values. It was found that DBP inhibited n ucleic acid and protein synthesis at an early stage of cell proliferat ion, hence its growth inhibitory effect may be related to inhibition o f the synthesis of macromolecules.