Development of Anti-tumor Drugs by Targetting Tumor Specific Isozyme (Type II) of Hexokinase

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We found that the steady state transcript level of type II hexokinase was specifically and remarkably elevated in rat tumor cell lines. In this study, we tried to establish a new strategy for the development of anti-tumor drugs and obtained following results.1)We isolated the cDNA fragment encoding human type II hexokinase and analyzed its transcript level by Northern blotting. As a result, we found that the transcript level of the type II hexokinase is elevated not only in rat hepatoma cell line, but also in human tumor cell line, HepG2.2)We isolated the gene encoding the type II hexokinase and characterized its structual features. As a result, we found a region which seems to be responsible for the enhanced expression of this gene in tumor cells.3)We think that hexokinase increases its activity by receving ATP from the ADP/ATP carrier exist in the inner mitochondrial membrane. Thus, we exaimed structure and function of this carrier by measuring the reactivities of cystein residues exist in this carrier under the various conditions and succeeded to reveal the transport mechanism at a molecular level.4)To find candidates of anti-tumor drug, we tried to establish the screening system of the specific inhibitor of the type II hexokinase. To obatin certain amount of this isozyme, we estabished a over-expression system of this enzyme in E.coli.