Lessons from the study of induced alterations in amino acids in patients with cancer.

The sensitivity of the neoplastic cell to amino acid deprivation shows considerable variation. The responsiveness of human leukemic cell cultures to L-asparaginase indicates that those of T cell origin are much more sensitive to the action of this L-asparagine-depleting enzyme than those of B cell origin. A cautionary note is raised concerning amino acid analogs. Minor changes such as substituting selenium for sulfur to make seleno-L-methionine rather than L-methionine may lead to considerable differences in their respective metabolic polls in vivo. A systemic survey of amino acid requirements of human neoplasms is desirable before designing new analogs.