Reduced expression of dipeptidyl peptidase (DPP) IV in peripheral blood T lymphocytes of oral cancer patients.

Abstract

To investigate the mechanism of decrease of serum DPP IV activity in oral cancer patients, we analyzed the expression of DPP IV in peripheral blood T lymphocytes of oral cancer patients and healthy subjects. Consequently, 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. However, 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 healthy subjects, serum DPP IV activity was significantly lower in cancer patients. DPP IV activity and amount of CD26 in T lymphocyte plasma membranes were much less in cancer patients than in healthy subjects. These findings suggest that a decrease in the number of T lymphocytes and the small amount of DPP IV in their plasma membrane may contribute to the decrease of serum DPP IV activity in cancer patients.