There is accumulating evidence that cysteine proteinase activity plays an important role in cancer cell invasion and metastasis. Previously we demonstrated that cathepsin B (CB) plasma activity is increased in patients with transitional bladder cancer (TCC). In this work we have attempted to determine whether urine CB protein levels could be used as tumor marker in bladder cancer patients. Urine CB levels were evaluated employing a dot blot method, in 30 patients with TCC, 21 patients successfully treated from TCC without evidence of disease at the moment of urine collection (NED) and in 30 healthy volunteers. The median value (Md) of the control group was 3.8 microg CB/ml. Significantly higher urine CB values (Md: 5.9 microg/ml) were found in the TCC group. A high CB value was also found in the NED group (5.0 microg/ml). Urine CB values over the 5.2 microg/ml (cut-off point) were observed in 63% of TCC patients, 48% of NED and 8% of the control group. Only 4% NED patients had CB values over 13.0 microg/ml while 33% of TCC patients surpassed this value. Thus, urine CB might be a potential marker for transitional bladder cancer diagnosis.

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