Abstract:The activity of cysteine peptidases (cathepsins B and L) was estimated in homogenates of tissues sampled during surgery from 60 patients operated due to colorectal tumors. The results were compared to those obtained using tissues in which histopathology disclosed no tumorous cells, obtained from 20 patients of the same group, treated as a control. Activity of the enzymes was inhibited using cysteine peptidase inhibitors isolated from chicken egg proteins. Application of the inhibitors was found to inhibit activity of the enzymes which play a key role in tumor development. It is suggested that in future the inhibitors may provide a component of new generation drugs in the so-called inhibitor therapy.

4Large intestine malignancy is the second most common malignancy and second leading cause of cancer mortality in Poland. This is related to late detection of these lesions, e.g. due to lack of effective screening tests. Lesions found by a surgeon are clinically advanced, making the treatment often ineffective and sometimes even completely impossible. Discovery of a substance that would be able to stop key processes for the development of malignancy could change such situation. Activity of certain enzymes was found to increase in malignant cells and invasion of malignancy could be triggered by inadequate amount of endogenous inhibitors of these enzymes in the surrounding healthy tissues. Inhibitors identical with that produced in human cells were found in egg whites. the aim of the study was to determine ability of cystatin isolated from egg whites to inhibit activity of cathepsin B and L. material and methods. Immunohistochemistry and histology of tissue specimen collected from malignant lesions resected from 60 patients diagnosed with large intestine adenocarcinoma, who underwent surgical treatment in 2 nd Department of General and Oncological Surgery, Medical University of Wrocław between 2007 and 2009. Results. Differences were fund between health tissues, margins and center of the malignant lesions with regard to amount and distribution of stained cathepsin B -cystatin complexes. The above mentioned inhibitors were able to inhibit 90% of primary activity of cathepsin B and L in malignant tissues. Conclusions. Cystatins obtained from egg whites could be used as substances supporting anti-cancer therapy in the future. Key words: malignancy, large intestine, cystatins, cathepsins, inhibitor therapyIncidence of large intestine malignancy is growing and it is estimated that a lifetime risk of large intestine malignancy among the worldwide population is 6%; high percentage of them will die. Cancer of the large intestine (colorectal cancer) is the second most common malignancy and second leading cause of cancer mortality in Poland, both in women and men. Its incidence in our country is increasing at a rate of 2.5% per year. Colorectal cancer is diagnosed too late in our country. Currently no screening method that would result in early detection of colorectal cancer with high sensitivity and specificity, that would be cheap and accepted by patients, is available. Studies and analyses suggest that the most effective screening programs are based on colonoscopy.