REDUCED EXPRESSION OF DIPEPTIDYL PEPTIDASE (DPP)-IV IN PERIPHERAL-BLOOD T-LYMPHOCYTES OF ORAL-CANCER PATIENTS

To investigate the mechanism of decrease of serum DPP TV activity in o ral cancer patients, we analyzed the expression of DPP IV in periphera l blood T lymphocytes of oral cancer patients and healthy subjects. Co nsequently, serum DPP IV activity was found to correlate significantly with the number of peripheral blood lymphocytes (PBL), T lymphocytes and CD26 (identified as DPP IV)(+) T lymphocytes in healthy subjects, and the number of PBL and CD26(+) T lymphocytes in cancer patients. Ho wever, the numbers of PBL and T lymphocytes were significantly less in cancer patients than in healthy subjects. Although the number of CD26 (+) T lymphocytes was somewhat greater in cancer patients than in heal thy subjects, serum DPP IV activity was significantly lower in cancer patients. DPP TV activity and amount of CD26 in T lymphocyte plasma me mbranes were much less in cancer patients than in healthy subjects. Th ese findings suggest that a decrease in the number of T lymphocytes an d the small amount of DPP IV in their plasma membrane may contribute t o the decrease of serum DPP IV activity in cancer patients.