Characterization of aldehyde dehydrogenase from HTC rat hepatoma cells.

We have proposed developing rat hepatoma cell lines as an in vitro model for studying the regulation of changes in aldehyde dehydrogenase activity occurring during hepatocarcinogenesis. Aldehyde dehydrogenase purified in a single step from HTC rat hepatoma cells is identical to the aldehyde dehydrogenase isolated from rat hepatocellular carcinomas. HTC aldehyde dehydrogenase is a 100 kDa dimer composed of 54-kDa subunits, prefers NADP+ as coenzyme, and preferentially oxidizes benzaldehyde-like aromatic aldehydes but not phenylacetaldehyde. The substrate and coenzyme specificity, effects of disulfiram, pH profile and isoelectric point of HTC aldehyde dehydrogenase are also identical to these same properties of the tumor aldehyde dehydrogenase. In immunodiffusion, both isozymes are recognized with complete identity by anti-HTC aldehyde dehydrogenase antibodies. Having established that HTC aldehyde dehydrogenase is very similar, if not identical, to the aldehyde dehydrogenase found in hepatocellular carcinomas, simplifies the development of molecular probes for examination of the regulation of tumor aldehyde dehydrogenase activity in vivo and in vitro.