The cysteine protease inhibitor cystatin was purified from chicken egg white and its antimicrobial activity determined for a series of pathogenic bacteria. The results indicate that Acinetobacter lwoffii, Escherichia coli, Oligella sp. and Pseudomonas aeruginosa are highly sensitive to low concentrations of cystatin, which possesses bactericidal activity. No inhibition was observed with a Citrobacter freundii strain. Fifty percent growth inhibition (IC 50 ) was observed at cystatin concentrations in the range of 80 and 100 lg/ml, and the growth was completely inhibited at concentrations in the range of 100 and 200 lg/ml. Fifty percent growth inhibition (IC 50 ) for Staphylococcus aureus, Staphylococcus gallinarum, and Staphylococcus xylosus strains was observed at 150 and 200 lg of cystatin/ml respectively, and growth was completely inhibited at cystatin concentrations in the range of 300 and 1000 lg/ml. The activity of cysteine proteases was significantly decreased in the culture supernatant of microorganisms when chicken cystatin was added. In this study, we observed that chicken cystatin may be a candidate for antibacterial drug development aiming at controlling bacterial pathogens including Escherichia coli, Pseudomonas aeruginosa, and another possible application might be as a therapeutic agent for health improvement.

Our experiment demonstrated that the cysteine peptidases cathepsins B and L may be useful for the early detection of gastric cancer. The results suggest that addition of egg white cystatin reduces the activities of cathepsins B and L to that of non-cancerous values.

Cysteine cathepsin B and its endogenous inhibitor play an important role in tumor progression. Increase in cathepsin B expression and reduced levels of its inhibitors were associated with tumor malignancy in breast cancer. The objective of this study was to investigate the effects of a new therapy combining vitamin E and placental inhibitor on the level of endogenous protease inhibitor in sera and tumor tissues with mammary cancer. The inhibitor was used in doses of 100 and 200 micrograms per animal for 8 days. Vitamin E was added after the last treatment with inhibitor and was injected daily in doses of 10 and 20 mg per animal for one mouth. The size and survival time of treated animals as well as cathepsin B and the inhibitor activity in tumor and sera before and after treatment in comparison with the control groups were determined. The activity of cathepsin B significantly decreased both in tumor tissues and in sera (P < or = 0.0001). Cathepsin B activity in tumor tissue homogenates and in sera decreased two-fold and three-fold, respectively, after the animals were treated with vitamin E at a dose of 20 mg, and decreased five-fold and 15-fold, respectively, when treated with vitamin E plus inhibitor in comparison with untreated animals. Endogenous inhibitor activity increased six-fold and 12-fold in the sera and tissue homogenates, respectively, after the animals were treated with 200 micrograms of cysteine protease inhibitor plus 20 mg of vitamin E, in comparison with untreated animals. The total cure responses were higher in eight of 10 rats, as compared with untreated animals. The combination of placental inhibitor and vitamin E resulted in a significant reduction in breast metastasis and might provide a therapeutic basis for anti-metastasis therapy.

situated in the zone of tumor invasion [1,2]. The understanding of changes in the activities of these proteolytic enzymes that initiate carcinogenesis has led to the concept of a cascade of mutual activation of proteolytic enzymes, which determines the ongoing activation of enzymes that take part in the crucial processes of carcinogenesis [3]. These changes are initiated by the presence of active cathepsin D or pepsin, which in acidic pH, activate precursors of cysteine endopeptidases. During malignant invasion, cathepsin B is initially produced in its precursor form, and the activity of this enzyme is stimulated by cathepsin D or pepsin in a low pH. Both low pH and high pepsin activity are present in the stomach, thus providing optimal conditions for the activation of cysteine peptidase precursors. The precursor enzymes are produced within cancer cells and only after secretion to the surrounding tissues are they activated and catalyze tumor invasion [4,5]. Of all cysteine peptidases (EC 3.4.22) mainly cathepsins B and L are involved in the metabolism of malignant tumors; these subsequently catalyze the conversion of other peptidases into their active forms, which are responsible for the degradation of normal tissues, and also for bringing about tumor invasion and metastases [5,6]. It has been confirmed that active cathepsin B is associated with many key processes in tumor growth; this finding was achieved by measurements of its activity in tissues and serum of people hospitalized for gastric cancer [7,8].A positive correlation between tumor invasiveness, as well as its metastatic potential, and the secretion of cysteine peptidases (particularly cathepsins B and L) has been well documented in the literature on this subject [3,9]. We postulate that cysteine peptidase activity could be used as a marker of cancer aggressiveness in diagnostic procedures in oncology. The correlation between the progression of early gastric cancer and the activity of cathepsins B and L has been studied by Dohchin et al. [10]. Their results correlated well with immunohistology and it was confirmed that the level of Conclusion. The local activities of cysteine peptidases and their inhibitors reflect the topographical differences between the center of the tumor, the zone of invasion, and healthy tissues in gastric cancer patients. In addition, the results for the pattern of changes in the activity of cysteine peptidases according to the degree of tissue infiltration were not dependent on the method of measurement (colorimetry vs spectrofluorometry).

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The combination of PDT and CPI could be a useful approach in tumour therapy as the two agents appear to be synergistic and probably decrease VEGF production by the tumour tissue.

Mouse polyclonal antibodies against placental cysteine proteinase inhibitor (CPI) react with the placental 67 kDa CPI on Western blots, and CPI present in ovarian cancer homogenate and serum was shown by double immunodiffusion to react with the same antiserum. By immunohistochemical staining, positive expression of high molecular weight CPI was observed on the tumour cell surface in serous and endometrioid ovarian carcinomas with metastasis. Normal endometrioid tissue was not stained with anti-placental CPI antibodies. Cathepsin B and pro-cathepsin B median levels in ovarian cancer tissue homogenates increased progressively with FIGO stage of the disease. The enzyme level decreased 22-fold after treatment of tissue homogenates with 5 nM purified CPI. These results provide evidence that addition of CPI reduces the levels of cysteine-type cathepsins to those of normal non-cancerous values.

The data indicate formation of metastasis significantly reduced in treated rats, which might provide a therapeutic basis for anti-cancer therapy.