L5178Y asparagine-dependent cells and independent clonal sublines: Toxicity of 5-diazo-4-oxo- l-norvaline

Abstract

Sublines of the asparagine-dependent L5178Y mouse lymphoblastic leukemia cells have been obtained by single-step clonal selection in asparagine-free medium. These sublines grow equally well with or without this amino acid in the medium. Inhibition of the growth of L5178Y cells in culture by the l-asparagine analog, 5-diazo-4-oxo- l-norvaline ( l-Donv), can be attributed to two different mechanisms. Both the l and d-stereoisomers of DONV inhibited the growth of the parent L5178Y line in Fischer's medium (with asparagine) as well as the growth of the asparagine-independent cells in the presence of asparagine. In a medium devoid of asparagine, however, l-Donv caused a more immediate cessation of growth of the asparagine-independent cells than in the medium normally supplemented with this amino acid. The toxicity of d-Donv was not enhanced by omission of asparagine. Evaluation of the effects of the analogs by cell cloning revealed a rapid loss of viability of both dependent and independent cells in the presence or absence of asparagine. These results indicate that l-Donv acts as an l-asparagine analog to inhibit the growth of cells dependent on endogenous asparagine synthesis, but that an additional cytotoxic effect of either stereoisomer of the analog exists.