Induction of aldehyde dehydrogenases during hepatocarcinogenesis

Only recently has a clear picture of the number, subcellular distribution and properties of rat liver aldehyde dehydrogenase begun to emerge. In addition to the basal normal liver isozymes, several additional activities are inducible in both normal and abnormal liver by a variety of xenobiotics, including chemical carcinogens. While the induction protocols vary widely and the induced activities appear to differ slightly in physical and functional properties, it is likely that only a small number of structural genes, perhaps 2 or 3, encode these new activities. Whether the diversity of new aldehyde dehydrogenases inducible in liver is due to differences in the transcription of these genes, differences in post-transcriptional processing or post-translational modification of the synthesized polypeptides is currently unknown. What is clear is that the induction of aldehyde dehydrogenase represents an intriguing problem in molecular genetics, the resolution of which would contribute significantly to our understanding of eukaryotic gene regulation.