Monitoring treatment of pulmonary carcinomas by serial determination of monoamine oxidase and diamine oxidase in blood serum.

We investigated monoamine oxidase (MAO--E.C. 1.4.3.4.) and diamine oxidase (DAO--E. C. 1.4.3.6.) in the serum of patients with lung cancer, treated with chemo- and radiotherapy. These enzyme activities were determined with tyramine and putrescine as substrates. The MAO activities of serum and DAO serum increased notably in some cases of lung cancer. These results are discussed in light of the postulated role of this enzyme in cell division and in the tumor development process.