BACKGROUND: Cysteine proteases (mainly cathepsins B and L) are thoughtto play an important role in the progress of cancer, including brain tumors. Together with other proteases,they hydrolyze the extracellular matrix and basement membrane proteins, thus enabling the tumor to growand spread. Therefore cysteine protease inhibitors are regarded as protective factors, able to preventtumor growth and dissemination.
MATERIAL AND METHODS: In this study, the activity of cysteine proteaseinhibitors (CPIs) was investigated in material derived from patients with brain tumors (astrocytoma andmeningioma). The activity of CPIs was measured as antipapain activity in tissue homogenates, cerebrospinalfluid, and serum, with N-benzoyl-DL-arginine-2-naphthylamide hydrochloride (BANA) as a substrate, accordingto Barret's method.
RESULTS: Tumorous tissues showed higher activity of cysteine protease inhibitors thancontrol tissues, but this difference proved to be statistically insignificant. The activity of CPIs waslower in cerebrospinal fluid and serum from patients with brain tumors.
CONCLUSIONS: The activity of CPIsmeasured in brain tumor tissue cannot be taken as a marker of any type of tumor, whereas CPI activityin cerebrospinal fluid and serum may be considered a marker of meningioma. In meningioma patients thelevel of CPIs may be too low to prevent the host tissues from the growing tumor.

Keywords: cysteine protease inhibitors, cystatins, cystatins, Astrocytoma, Meningioma