2-(fluoromethyl)dehydroornithine-methyl-ester and 6-heptyne-2-5-diamine

The antitumor properties of (E)-2-(fluoromethyl)dehydroornithine methyl ester (delta-MFMO-ME) and of (E)-2-(fluoromethyl)dehydroornithine ethyl ester (delta-MFMO-EE), the prodrugs of delta-MFMO, an irreversible inhibitor of mammalian L-ornithine decarboxylase (ODC) 14 times more potent than alpha-difluoromethylornithine (DFMO) and equipotent to (2R,5R)-6-heptyne-2,5-diamine (MAP) in vitro, have been investigated in L1210 leukemia- and Lewis lung carcinoma-bearing mice. The anticancer properties of these esters have been compared with those of DFMO and MAP as a function of the dose, the route of administration, and the stage of the lewis lung carcinoma development in mice. The two esters, administered i.p. shortly after cell inoculation at one-fifth the dose of DFMO, prolonged the survival of mice-bearing leukemia to the same extent as DFMO and MAP. When administered orally to leukemia-bearing mice the two esters were equipotent at prolonging survival. The methyl ester appears, however, to be slightly, but not significantly, more effective than the ethyl ester against leukemia when given i.p., maximum prolongation of the mice survival (79%) occurring at 0.5 g/kg methyl ester every 12 h. The two esters achieve at one-sixth to one-twelfth the dose, antitumor effects similar to DFMO in the Lewis lung carcinoma model, the ethyl ester being slightly, but not significantly, more effective than the methyl ester when administered orally. Moreover, the ethyl ester causes greater reduction of tumor growth than DFMO (P less than 0.05) and MAP (P less than 0.01) in this model. Inhibition of tumor growth is correlated with spermidine depletion and an increase of decarboxylated-S-adenosylmethionine, the aminopropyl donor in the spermidine and spermine synthase reactions. All ODC inhibitors, however, lose most of their antitumor properties when administered at late stage of Lewis lung carcinoma development. Finally, this study demonstrates the advantage of using prodrugs of delta-MFMO, an inhibitor of ODC, since they possess longer duration of action, higher potency, and in some cases better antitumor efficiency than the parent direct inhibitor of ODC. Moreover, and as already noticed for DFMO or MAP, no sign of overt toxicity is caused by the highest effective antitumor doses of the esters.

Topics: Administration, Oral; Alkynes; Animals; Diamines; Eflornithine; Injections, Intraperitoneal; Leukemia L1210; Lung Neoplasms; Mice; Mice, Inbred DBA; Ornithine Decarboxylase Inhibitors; Prodrugs; S-Adenosylmethionine; Time Factors; Tumor Cells, Cultured

Proliferation of Acanthamoeba castellanii (Neff strain) in either a broth medium or a defined medium was arrested by alpha-monofluoromethyldehydroornithine (delta-MFMOme), alpha-difluoromethylornithine (DFMO), and (R,R')-delta-methyl-alpha-acetylenic putrescine (MAP), three specific inhibitors of ornithine decarboxylase. Although all three inhibited the ameba enzyme, delta-MFMOme was the most effective inhibitor of multiplication. Growth inhibition was reversed by the addition of polyamines. The inhibitors did not induce differentiation by themselves although DFMO caused encystment when supplemented with CaCl2 or MgSO4.

Topics: Acanthamoeba; Alkynes; Animals; Culture Media; Diamines; Eflornithine; Ornithine Decarboxylase Inhibitors; Polyamines; Putrescine

The effects of the enzyme-activated irreversible inhibitors of ornithine decarboxylase, alpha-difluoromethylornithine, alpha-(fluoromethyl)dehydroornithine, alpha-(fluoromethyl)dehydroornithine methyl ester, and (2R,5R)-6-heptyne-2,5-diamine (RR-MAP), on cell growth and parameters related to polyamine biosynthesis were compared in L5178Y and L1210 cells under identical culture conditions. The two lines are murine lymphocytic leukemia cells which differ in their ability to metabolize 5'-methylthioadenosine, the by-product of polyamine biosynthesis: L5178Y cells contain a specific 5'-methylthioadenosine phosphorylase; L1210 cells do not. In L1210 cells, the 50% inhibitory concentrations (lC50S) of the various analogues were 3.0 mM for alpha-difluoromethylornithine, 0.2 mM for alpha-(fluoromethyl)dehydroornithine, 0.1 mM for alpha-(fluoromethyl)dehydroornithine methyl ester, and 0.01 mM for RR-MAP. L5178Y cells were somewhat more sensitive to the inhibitors with lC50 values of 0.5 mM for alpha-difluoromethylornithine, 0.06 mM for alpha-(fluoromethyl)dehydroornithine, 0.03 mM for alpha-(fluoromethyl)dehydroornithine methyl ester, and 0.002 mM for RR-MAP. In all cases, growth inhibition was fully prevented by exogenous putrescine. The effects of the inhibitors on parameters related to polyamine metabolism were compared at drug concentrations approximating the average of lC50 values for the two cell lines. Under these treatment conditions, polyamine pools were similarly affected by the various inhibitors. Typically, putrescine and spermidine were depleted, but effects on spermine pools differed according to the cell line, increasing slightly in L1210 cells and decreasing by about 50% in L5178Y cells. Spermine pools in L1210 cells could be reduced by RR-MAP at concentrations higher than the lC50 (i.e., 0.1 mM). Clonogenicity in soft agar was decreased about 50% by putrescine and spermidine depletion and was not further affected by spermine depletion. The inhibitors elevated S-adenosylmethionine decarboxylase activity in both cell lines with a 2-fold greater increase in L5178Y cells than in L1210 cells. Finally, the inhibitors decreased S-adenosylmethionine pools in L1210 cells by about 50% but had little effect on these pools in L5178Y cells with the exception of RR-MAP, which decreased S-adenosylmethionine pools by about 40%. Whether the different polyamine responses of the two cell lines are related to their ability to metabolize 5'-methylthioadenosine is unce

Topics: Alkynes; Animals; Biological Transport; Cell Cycle; Cell Survival; Diamines; Eflornithine; Leukemia L1210; Leukemia L5178; Leukemia, Lymphoid; Mice; Ornithine; Ornithine Decarboxylase Inhibitors; Polyamines; Purine-Nucleoside Phosphorylase; S-Adenosylmethionine