Evaluation of adenosine deaminase activity in patients with head and neck cancer.

ADA is a key enzyme in the mammalian purine salvage pathway. The lack of ADA activity has been linked to a lack of cellular immunity in various immune and myeloproliferative disorders. Data on its role in patients with solid tumors are scant and inconclusive. In this report, we have evaluated the activity of this enzyme in the peripheral lymphocytes of patients with head and neck squamous cell cancer (HNC). The mean ADA activity in Stage IV patients (0.57 +/- 0.08 SEM, n = 12) was significantly lower than that of controls (1.55 +/- 0.25 SEM, P less than 0.05, n = 14) and also significantly lower that the mean ADA activity in patients with Stages I, II, and III (1.14 +/- 0.10 SEM, P less than 0.05, n = 17). Fourteen out of 19 controls, Stage I, II, and III patients had positive skin tests compared to 7 out of 10 Stage IV patients. These differences were not statistically significant. There was also no correlation between ADA activity and the absolute lymphocyte counts. Our results indicate that ADA activity in lymphocytes of patients with advanced HNC is lower than that of controls or patients with earlier stages of the disease. ADA may be a more sensitive indicator of suppressed cellular immunity than delayed cutaneous hypersensitivity reactions, or monitoring absolute lymphocyte counts.