Cathepsin D activity in the blood serum and urine in patients with colonic adenocarcinoma

Cathepsin D [EC 3.4.23.5] is an aspartyl proteinase, which is one of the enzymes of the proteolytic cascade involved in cancerous invasion and formation of metastases. It has been found in both normal and cancerous tissues. Cathepsin D takes part in the penetration of a cancerous tumour in the tissues, migration of the neoplastic cells and their location in the metastatic foci.
The aim of the study was to evaluate a diagnostic value of determination of cathepsin D activity in patients with colonic adenocarcinoma.
The study was carried out on samples of the blood serum and urine of 9 patients treated in the First Department of General and Endocrinological Surgery of the Medical University of Białystok, aged 56 to 81 years with histologically diagnosed colonic adenocarcinoma, and of 6 healthy individuals aged from 28 to 40 years constituting controls.
Cathepsin D activity was assessed by the Folin-Ciocalteau method in the cupric modification and expressed in nmol Tyr/ml/6 h in the blood serum, and in nmol Tyr/mg of protein/6h in the urine. Protein concentration was determined by Lowry’s method and the results were expressed in mg/ml.
Cathepsin D activity was significantly higher (1.5 – fold) in the blood serum of patients with colonic adenocarcinoma than in controls (p<0.003). However, it was decreased in the urine of patients with colonic adenocarcinoma in comparison with healthy people. No statistically significant differences were found in cathepsin D activity (p=0.426) or protein concentration (p=0.139) in the urine of patients with colonic adenocarcinoma compared to controls.
The results suggest that cathepsin D activity can be used as a marker of colonic adenocarcinoma.