Lactate dehydrogenase isoenzymes in squamous cell carcinomas of the oral cavity.

Lactate dehydrogenase (LDH; EC 1.1.1.27) isoenzymes in human epithelial cells from squamous cell carcinomas and healthy tissues of the oral cavity of five patients were analyzed using isoelectric focussing. A new basic isoenzyme and high LDH-7 and LDH-9 activity were found in tumor cells in contrast to epithelial cells of adjoining nontumor tissue. These findings indicate that gradual changes in the percentage distribution of LDH isoenzymes may represent a useful parameter of disease activity in patients with squamous cell carcinomas.