Ornithine decarboxylase induction and polyamine biosynthesis are required for the growth of interleukin-2- and interleukin-3-dependent cell lines.

The objective of this study was to evaluate induction of ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, and subsequent polyamine accumulation in interleukin-2 (IL-2)- and interleukin-3 (IL-3)-dependent growth. The CTLL-20 and FDC-P1 cell lines, which have been shown to be absolutely dependent on IL-2 and IL-3, respectively, were used in these studies. The CTLL-20 and FDC-P1 cells each had different temporal patterns of ODC induction following lymphokine stimulation. ODC levels increased rapidly in the FDC-P1 cells, peaking 4 hr after stimulation with IL-3. In contrast, peak ODC activity in the CTLL-20 cells occurred 18 hr following stimulation with IL-2 and reached eightfold higher levels than those observed in the FDC-P1 cells. Treatment with D,L-alpha-difluoromethylornithine X HCl X H2O (DFMO), a specific irreversible inhibitor of ODC activity, completely abrogated lymphokine-dependent ODC induction in both the CTLL-20 and FDC-P1 cell lines. Similarly, intracellular levels of the polyamines putrescine and spermidine were reduced in both cell lines following DFMO treatment. DFMO treatment reduced both IL-2- and IL-3-dependent proliferation in a dose-dependent manner. However, this inhibition could be reversed by the addition of exogenous putrescine. DFMO treatment had no effect on cell viability. Polyamine-depleted CTLL-20 and FDC-P1 cells showed decreased absorption of IL-2 and IL-3 activity, respectively. However, the addition of exogenous putrescine restored the ability of the cells to absorb the appropriate lymphokine. These data are the first to demonstrate that ODC induction and polyamine biosynthesis are required in lymphokine dependent growth.