Urine and serum cathepsin B concentrations in the transitional cell carcinoma of the bladder.

BACKGROUND: It has been shown that expression and activity of lysosomal proteolytic enzymes (i.e., cathepsin B) correlate with tumor progression in various neoplasms. We investigate possible correlation of cathepsin B concentrations with grading and invasivity of tumorous bladder tissue.
METHOD: Cathepsin B concentrations in serum and urine were measured in 40 patients (29 men, 11 women, mean age 68 years) with transitional cell carcinoma (TCC) of the bladder without metastases and in control group of 64 healthy subjects (28 men, 36 women, mean age 55 years) using commercially available enzymatic immunoassay. Concentration of cathepsin B in urine was adjusted on creatinine. Urinary creatinine in all samples was measured by enzymatic creatinase method. Patients were divided into groups according to the grading (low grading: 18 patients, high grading: 22 patients) and invasivity of the carcinoma (nonmuscle-invasive tumors: 23 patients, invasive tumors: 17 patients). RESULT: Concentrations of cathepsin B in urine were significantly elevated in patients than in control group (Median = 3.87 μg/L vs. 1.35 μg/L, P = 0.0002). Similarly, the ratio of U-cathepsin B/creatinine was significantly higher in patients (Median: 0.44 μg/mmol creatinine vs. 0.17 μg/mmol creatinine, P < 0.0001). U-cathepsin B may prove to be useful biomarker (area under the curve [AUC] = 0.72 and 0.73 for the U-cathepsin B/creatinine ratio, respectively). S-cathepsin B significantly correlated with grading of carcinoma (P = 0.02) and U-cathepsin B and U-cathepsin B/creatinine are positively associated with invasive tumors (P = 0.0001 and P = 0.002).
CONCLUSION: Cathepsin B concentrations correlate well with grading and invasivity of tumors and may have diagnostic value in investigation of bladder cell carcinoma. New index U-cathepsin B/Creatinine ratio is more appropriate biomarker to monitor TCC, than U-cathepsin B so far.