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One of the most important issues facing health care is the prevention and treatment of different types of cancer. Among the most frequently encountered types of cancer leading to lethality are lung cancer, breast cancer and colon cancer. The search for new drugs for cancer cells treatment and clarifying the mechanisms of their anti-tumor effect is a scientific challenge and a necessary basis for new more effective methods of cancer treatment. A major role in tumor growth, invasion, angiogenesis and metastasis have different types of proteases whose activities are inhibited by some synthetic drugs. Protease inhibitors of plant origin have the potential to be an alternative or supplement to the treatment with synthetic drugs, but the mechanisms of their anti-tumor effects are poorly understood. In this review the current knowledge of plant protease inhibitors as tumor preventive and suppresive agents, and the perspectives of their use as antitumour drugs are discussed. [ABSTRACT FROM AUTHOR]

In order to evaluate the role of aminopeptidases (APs) in drought response and their potential as protein markers to distinguish between stress tolerant and sensitive varieties, various AP activities were studied in roots and leaves of winter wheat seedlings, subjected to severe but recoverable soil drought stress. Two varieties with contrasting drought tolerance - Yantar (drought tolerant) and Miziya (sensitive) were compared. Activity changes under severe water stress and subsequent recovery were related to changes in the pools of the major redox buffers ascorbate and glutathione, changes in protein profiles and total proteolysis in roots and leaves. Glutathione was responsive to drought both in roots and leaves, with increased total pool and transient rise in the oxidized form; stronger response in the roots of Yantar was observed. The sensitive variety had higher ascorbate content in leaves under stress. Severe drought led to reversible changes in protein profiles and increase in major protease bands in leaves but not in roots. AP activities were partly independent from the predominant endoprotease activities. Highest activities in roots were detected with substrates releasing terminal leucine, lysine and metionine. In stressed leaves AP activities toward most of the substrates increased under drought, without clear differences comparing varieties. Activities tested with Gly-pNA were raised in leaves only in recovery from stress. In roots, the tolerant variety Yantar presented increased AP activities under stress with most of the substrates used except Leu-pNA and Phe-pNA, whereas the sensitive variety Miziya had almost unchanged AP activities. Based on activity profile changes, at least two different AP enzymes should exist in wheat. It remains to be established which activities towards different substrates reflect distinct aminopeptidases. [ABSTRACT FROM AUTHOR]

Proteases and their specific inhibitors are ubiquitously distributed and play a key regulatory role in many biological processes. Gene expression and activity of certain proteases has been shown to increase in Triticum aestivum L. leaves under drought, with a major contribution of cysteine proteases, especially in sensitive wheat varieties. However, little is known about the stress response of protease inhibitors (PIs) and their role in the regulation of intracellular proteolysis. In this study the changes in transcript abundance of some protease inhibitors (belonging to cystatin and serpin classes) were evaluated by semi-quantitative RT-PCR in leaves and roots of winter wheat seedlings from two varieties with differing tolerance. The expression of two cysteine proteases in the same samples was also assessed. The expression of the studied genes was compared in the tolerant variety "Katya" and the more susceptible to water deprivation variety "Sadovo", applying severe but recoverable soil drought. Growth inhibition and stress related parameters confirmed the relatively higher drought sensitivity of variety "Sadovo". Serpin transcript abundance in control roots was higher than in the leaves. An opposite trend was documented for cystatins - the level of their expression was stronger in the non-treated leaves compared to roots. Drought stress inhibited PI expression in roots, while varying effects on the transcript levels were detected in the leaves of water deprived plants. The levels of the two cysteine protease transcripts under drought exhibited organ-specific response - they declined in roots, and increased in leaves. Further detailed studies using more sensitive methods are necessary to evaluate the potential of protease inhibitors as biochemical markers for drought tolerance. [ABSTRACT FROM AUTHOR]