PLAU and cancer: As a control, the Eu-DOTA-Gly4, which is unresponsive to uPA activity, was used, and it was demonstrated that after injection of probes to the tail vein of the cancer bearing mouse, the CEST effect increased in tumor tissues right after injection to be later decreased more rapidly in Z-GGR-l-amino-(Tm-DOTA) then in control Eu-DOTA-Gly4 as a result of peptide cleavage by uPA.