TGF-β1 inhibits polyamine biosynthesis in K 562 leukemic cells

The present study proved that TGF-β1 significantly inhibited the growth of K 562 cells. The drop in cell numbers after 24 h incubation with increasing concentrations of TGF-β1 (0.01, 0.1, 1.0, 10.0 ng/ml) was accompanied by significant suppression of the activity of two key enzymes of polyamine biosynthesis: ornithine decarboxylase (ODC) and S-adenosylme-thionine decarboxylase (SAMDC). In contrast to ODC and SAMDC activity, TGF-β1 did not significantly affect the absolute concentration of spermidine and spermine in K 562 cells. We suppose that the lack of an evident drop in concentration of spermidine and spermine in spite of a significant decrease in ODC and SAMDC activity in K 562 cells exposed to TGF-β1 resulted from the uptake of polyamines from the extracellular space.