Effect of methionine depletion on growth and apoptosis in various tumor cell lines.

Sodium ascorbate, sodium 5,6-benzylidene-L-ascorbate (SBA), gallic acid and caffeic acid induced apoptotic cell death in human myelogenous leukemic cell lines, and stimulated oxidation of methionine into methionine sulfoxide in the culture medium. When various tumor cell lines were cultured in methionine-free medium, their growth was nearly terminated at G1 phase of the cell cycle, producing much smaller number of apoptotic cells. Addition of methionine sulfoxide to the methionine-free medium did not stimulate the apoptosis induction. These data suggest that induction of apoptosis by ascorbates, gallate or by caffeate cannot be simply explained by methionine oxidation.