Tumor M2-PK and glutaminolytic enzymes in the metabolic shift of tumor cells

The pyruvate kinase isoenzyme M2-PK is known to be associated with a metabo lic shift that is characteristic for tumor cells. Meanwhile, the universal expression of this isoenzyme is the basis for the detection of various tumo r diseases in human clinical diagnosis. Other enzymes which are known to be essential for this tumor specific metabolic shift in mt chemical carcinoge nesis are the NADP-dependent enzymes malic enzyme, isocitrate dehydrogenase and glucose 6-phosphate dehydrogenase. To evaluate the role of these enzym es in human carcinogenesis, we compared their enzymatic activities in norma l colon mucosa and tissues derived from primary colon tumors. Histochemical staining showed that the enzyme activities were restricted to mucosal colo n cells and colon cancer cells. The enzymes were strongly but heterogeneous ly expressed in the tumor tissues, whereas staining of normal mucosa was we ak. Tumor M2-PK showed the most prominent differences in normal colon mucos a and colon cancer cells.