ABSTRACT
This chapter discusses the relationship of diamine oxidase (DAO) activity to the cell populations present in certain human tumors, to the normal cell types from which the tumors may arise, and to the clinical monitoring of such neoplasms. The interest in DAO in tumor tissues probably can be traced back to original findings of Ahlmark and Danforth and Gorham concerning high activities of the enzyme in the circulation and placenta of humans and other mammalian species. In the early 1970s, using specific radioassays with either histamine and/or putrescine as substrates, high DAO activity was found to be a consistent property of the human endocrine tumor, medullary thyroid carcinoma. In medullary thyroid carcinoma and lung cancers, increased DAO activity was also found in metastases as compared to surrounding normal tissue. The enzyme activity was increased not only in the tissues, but in the circulation of some patients with this cancer, and predominantly in those patients known to have metastatic disease.
