Activity of cysteine protease inhibitors in human brain tumors.

BACKGROUND: Cysteine proteases (mainly cathepsins B and L) are thought to 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 grow and spread. Therefore cysteine protease inhibitors are regarded as protective factors, able to prevent tumor growth and dissemination. MATERIAL AND METHODS: In this study, the activity of cysteine protease inhibitors (CPIs) was investigated in material derived from patients with brain tumors (astrocytoma and meningioma). The activity of CPIs was measured as antipapain activity in tissue homogenates, cerebrospinal fluid, and serum, with N-benzoyl-DL-arginine-2-naphthylamide hydrochloride (BANA) as a substrate, according to Barret's method. RESULTS: Tumorous tissues showed higher activity of cysteine protease inhibitors than control tissues, but this difference proved to be statistically insignificant. The activity of CPIs was lower in cerebrospinal fluid and serum from patients with brain tumors. CONCLUSIONS: The activity of CPIs measured in brain tumor tissue cannot be taken as a marker of any type of tumor, whereas CPI activity in cerebrospinal fluid and serum may be considered a marker of meningioma. In meningioma patients the level of CPIs may be too low to prevent the host tissues from the growing tumor.

Decrease in vivo of cysteine endopeptidases in blood of patients with tumor of the larynx.

Since cysteine endopeptidase (cathepsins B and L) have been proposed to be implicated in tumor malignancy, we have attempted to decrease these in vivo. Large amounts of urine cysteine peptidase inhibitors (UCPI) are present in the urine of patients. Our results indicate protective effects of a UCIP preparation against human serum cysteine endopeptidases.