IN-VIVO MANIPULATION OF L1210 CELL-CYCLE PHASE DISTRIBUTION WITH ALPHA-DIFLUOROMETHYLORNITHINE, 4-AMIDINOINDAN-1-ONE 2'-AMIDINOHYDRAZONE AND N-1-ACETYLSPERMINE

We investigated whether the in vivo growth inhibitory effect of the co mbination of 4-amidinoindan-l-one 2'-amidinohydrazone (CGP 48664A) and alpha-difluoromethylornithine (DFMO) is reversible by treatment with N-1-acetylspermine (N-1-acSp). DBA-2 mice were inoculated with 10(5) L 1210 cells i.p. on day 0. From day 1 they received 2.50 mg CGP 48664A/ kg i.p. once daily and 500 mg DFMO/kg i.p. twice daily. On day 5 they received 3 X 2500 nmol N-1-acSp i.p. with 15-min intervals. L1210 cell numbers, S-phase percentage and polyamine contents, and liver and spl een polyamine contents were monitored in the following 48 h. Four days treatment with CGP 48663A/DFMO reduced L1210 cell numbers, S-phase, a nd spermidine. N-1-acSp treatment increased L1210 spermidine from less than or equal to 8 h and percentage S-phase from 12 h. Maxima for spe rmidine and S-phase were reached at less than or equal to 8 and 18 h, respectively. These were below levels of untreated controls. Decreases were noted from 12 and 18 h, respectively. N-1-acSp was detectable in L1210 from 0-18 h. Liver spermidine was decreased by CGP 48664A/DFlVI O. After N-1-acSp treatment, liver N-1-acSp and N-1-acSd increased fro m less than or equal to 8 h, reached maxima at less than or equal to 8 and 10 h, respectively, and were undetectable from 15 h. We conclude that the in vivo growth inhibitory effect of CGP 48664A/DFMO is revers ible by N-1-acSp treatment. The liver is probably involved in N-1-acSp terminal catabolism. The effect of the polyamine depletion-repletion scheme on S-phase cell numbers may be much more profound than present estimates from 5-bromo-2'-deoxyuridine incorporation. (C) 1998 Elsevie r Science B.V. All rights reserved.