According to International Agency for Research on
Cancer,
ethanol and
acetaldehyde belong to group 1 of human
carcinogens. The accurate mechanism by which alcohol consumption enhances
carcinogenesis is still unexplained. Alcohol is oxidized primarily by
alcohol dehydrogenase (ADH) to
acetaldehyde, a substance capable of initiating
carcinogenesis by forming adducts with
proteins and
DNA and causing mutations. Next,
acetaldehyde is metabolized by
aldehyde dehydrogenase (ALDH) to
acetate. In tissues of many
cancers, we can observe significantly higher activity of total
alcohol dehydrogenase with any change in
aldehyde dehydrogenase activity in comparison with healthy cells. Moreover, in malignant diseases of digestive system, significantly increased activity of ADH
isoenzymes class I, III and IV was found. The gynecological, brain and
renal cancers exhibit increased activity of class I ADH. ADH and ALDH can play also a crucial regulatory role in initiation and progression of malignant diseases by participation in
retinoic acid synthesis and elimination of toxic
acetaldehyde. Besides, changes of
enzymes activities in
tumor cells are reflected in serum of
cancer patients, which create the possibilities of application ADH
isoenzymes as
cancer markers.