Kringle domains are composed of about 90 amino acid residues.They are are found throughout the blood clotting and fibrinolytic proteins.In recent years,kringle domains are also found to have antitumor activities such as anti-angiogenesis.We investigated the antitumor effect of human plasminogen kringle 5 domain (rhPK5) and kringle-containing amino-terminal fragment (ATF) of uPA.Combined treatment using rhPK5 and radiotherapy displayed obvious suppressive effect on LLC tumor growth and resulted in a more additive effect on tumor growth delay and significant enhancement of the survival,but no toxic effect.