BIOMEDICAL APPLICATION OF K5 PLASMINOGEN FRAGMENT

Aim. Plasminogen kringle 5 is an endogenous angiogenic inhibitor. The purpose of the present review was to highlight the potential biomedical application of kringle 5 in the regulation of angiogenesis and tumor growth. Methods. Angiogenesis is a complex process that involves endothelial cell proliferation, migration, basement membrane degradation, and neovessel organization. Since the uncontrolled growth of new blood vessels causes the progression of many common diseases, first of all, oncological diseases, autoimmune disorders, neovascular damage of the eye, the use of angiostatins can be a promising pharmacotherapeutic approach to the prevention and adjuvant therapy of these pathological conditions. The advantages of angiostatins application are their non-toxicity even at high doses, non-immunogenicity, lack of tolerance of target cells to their action. Angiostatins comprise a group of kringle-containing proteolytically-derived fragments of plasminogen/plasmin, which act as potent inhibitory mediators of endothelial proliferation and migration. Among all known angiostatin species, isolated K5 plasminogen fragment was shown to display the most potent inhibitory activity against proliferation of endothelial cells via triggering multiple signaling pathways, which lead to cell death and resulting angiogenesis suppression. Results. Current literature data suggest that in addition to expressed and highly specific cytotoxicity in relation to endotheliocytes and some types of tumor cells, the kringle domain 5 of human plasminogen has other advantages as an antiangiogenic and antitumor regulator, including its specific inhibitory activity, which affects only activated, proliferating endothelial cells, and therefore is non-toxic to other types of normal cells. As an endogenous protein, which is formed in the human organism, K5 does not provoke an immune response. K5 as a small polypeptide molecule with a stable structure can be obtained as a recombinant protein in E. coli cells, and can also be used in pharmacokinetic systems of targeted delivery and sustained release. Conclusions. The prospect of successful use of K5 as a therapeutic agent to manage pathological processes associated with dysregulation of angiogenesis makes it necessary to develop and improve methods of its production and to further test its plausible pleiotropic biological activities.