In vitro manipulation of L1210 cell cycle kinetics with 4-amidinoindan-1-one 2′-amidinohydrazone, α-difluoromethylornithine and N1-acetylspermine

We investigated whether in vitro L1210 growth inhibition by alpha-difluoromethylomithine (DFMO; 740 mu M) and 4-amidinoindan-l-one 2'-amidinohydrazone (CGP 48664A; 1.7 mu M) ii reversible with N-1-acetylspermine (N-1-acSp). Influences of N-1-acSp dose (1-100 mu M), time (0-12 h at 100 mu M), aminoguanidine (AG, 1 mM) and cell numbers (at 1 mu M N-1-acSp) on percentage S-phase, polyamine contents and viability were determined. DFMO/CGP 48664A decreased percentage S-phase from 58 to 26%, decreased spermidine (Sd) and sl,ermine (Sp) contents 3-fold, but did not affect viability. With increasing N-1-acSp dose, S-phase percentage and Sd contents increased concomitantly, reaching plateau values that were comparable with those of untreated controls. S-phase and Sd content increased from 4-6 h after N-1-acSp administration, reaching plateau values from 11 and 6 h, respectively. N-1-acSp content was dose dependent and increased linearly to reach plateau values from 8 h. AG did not affect any of these parameters. Addition of 1 mu M N-1-acSp to decreasing numbers of DFMO/CGP 48664A-treated cells caused increasing S-phase percentage, Sd and N-1-acSp contents. We conclude that cell cycle kinetics of cultured L1210 cells can be manipulated by the induction of growth inhibition with DFMO/CGP 48664A and its subsequent abolishment with N-1-acSp. N-1-acSp accumulation rate and its subsequent conversion to Sd is relatively slow compared with intracellular Sd needs. The data support the notion that Sd is the most important polyamine for growth. (C) 1998 Elsevier Science B.V. All rights reserved.