Adenosine deaminase activity in the serum and malignant tumors of breast cancer: The assessment of isoenzyme ADA1 and ADA2 activities

Objective: The potential relationship between adenosine deaminase activity and cancer progression was examined by investigating the activity of total ADA and its isoenzymes in serum and simultaneously in the cancerous tissue of each patient with breast cancer. Methods: Total ADA and its isoenzymes were measured using the Giusti method. ADA2 activity was measured in the presence of a specific ADA1 inhibitor, EHNA. Results: Our results indicated that ADA2 and total ADA activities were higher in serum and malignant tissues than those of corresponding controls (P < 0.05). Tumor ADA2 and total ADA activities were significantly (P < 0.05) correlated with lymph node involvement, histological grade and tumor size, whereas their levels in serum were significantly (P < 0.05) correlated with menopausal status and patient age. Conclusion: Although serum and tumor total ADA activity and its ADA2 isoenzyme were both found to be increased, distinct correlation patterns were observed with some of the prognostic factors. It can be speculated that increased ADA and isoenzyme activities in serum originated from sources other than the breast tumors.