[Enzyme and isoenzyme activity in patients with malignant tumors of the oral mucosa].

The activity and isoenzyme profile of lactate dehydrogenase (LDH), alkaline and acid phosphatase were studied in tumors of the tongue, cheek, oral floor, soft palate and palatine tonsils (n = 100), leukoplakia (n = 7) and in the oral mucosa at corresponding sites in healthy subjects (n = 66), to develop tests for early detection, monitoring and prognosis of oral cancer. Levels of alpha-amylase and acid phosphatase were measured in saliva and blood serum of patients with oral cancer and healthy subjects. The activity of LDH and alkaline and acid phosphatase in oral malignancies were 1.5-6 times that in normal mucosa, depending on tumor site. Changes in LDH isoenzyme profile consisted in an increased level of M-subunits (LDH-4 and 5) and a decreased concentration of N-subunits (LDH-1 and 2). With regards to acid phosphatase, an increase in the activity of its tartrate-inhibited fraction was observed. An increase in LDH and alkaline phosphatase activity was registered for oral precancer (leukoplakia), too, although it was less pronounced than in cancer. Changes in LDH isoenzyme profile matched those in cancer patients. A significant increase in the activity of alpha-amylase, acid phosphatase and the latter's tartrate-inhibited fraction was registered in saliva of oral cancer patients (86-96%). The credibility of enzyme activity measurement in saliva for evaluation of response and prognosis is discussed.