Serum dipeptidyl peptidase (DPP) IV activity in hamster buccal pouch carcinogenesis with 9,10-dimethyl-1,2-benzanthracene.

Dynamic change of serum DPP IV activity in carcinogenesis of hamster buccal pouch epithelium with DMBA was investigated. The serum enzyme level in hamster (21.5 +/- 3.1 IU/l serum) was decreased gradually from the 8th to the 10th wk when papillomas were induced by DMBA application (18.9 +/- 2.7 IU/l serum). The enzyme level was further decreased in the formation of carcinoma in situ or early invasive carcinoma (13.2 +/- 0.5 IU/l serum), and reached to less than half of the normal level at the time when tumors were diagnosed as squamous cell carcinoma histologically (8.1 +/- 1.3 IU/l serum). This enzyme level was increased by tumor excision and decreased again by tumor recurrence toward death. These findings suggested that the decrease of serum DPP IV activity occurred from the early stage of hamster buccal pouch carcinogenesis as a tumor-burden marker.