Serum amine oxidase activity contributes to crisis in mouse embryo cell lines

This paper reports the results of experiments to test the hypothesis that crisis of spontaneous transformation is caused by the hydrogen peroxide and/or aldehydes generated from endogenous polyamines by serum amine oxidase [amine: oxygen oxidoreductase (deaminating), EC 1.4.3.6]. After 4-5 weeks of culture, crisis occurred in 16 of 29 cell lines derived from limb buds of embryos from SJL/J, C3H, and CD-1 mice. In contrast, after the same time in culture but in medium supplemented with aminoguanidine, which inhibits serum amine oxidase, crisis occurred in only 1 of 41 cell lines. Protection against crisis was maximal in cell lines of SJL/J embryos, in which the incidence of crisis fell from 7 of 9 in untreated controls of 0 to 12 in the presence of 2 mM aminoguanidine. 2-Mercaptoethanol at 150-300 microM, which protects cells from serum amine oxidase-dependent polyamine toxicity, also protected the cell lines against crisis. These protected cell lines retained proliferative potential, diploid DNA content, and the mixture of cell types found in the primary cultures. These results indicate that cytotoxic catabolites generated by serum amine oxidase caused at least a large portion, but perhaps not all, of the cellular damage that leads to crisis in mouse embryo cell lines.