Byunghee Yoo1, Vipul R. Sheth2,
Christine A. Howison3, Matthew Douglas4, Carlos T.
Pineda5, Amanda F. Baker6, Mark D. Pagel7
1Biomedical Engineering,
University of Arizona, Tucson, AZ, United States; 2Biomedical
Engineering, Case Western Reserve University, Cleveland, OH, United States; 3Arizona
Research Laboratories, University of Arizona, Tucson, AZ, United States; 4College
of Medicine, University of Arizona, Tucson, AZ, United States; 5Arizona
Cancer Center, University of Arizona, Tucson, AZ, United States; 6Hematology/Oncology,
Arizona Cancer Center, University of Arizona, Tucson, AZ, United States; 7Biomedical
Engineering & Chemistry & Biochemistry, University of Arizona,
Tucson, AZ, United States
We have detected the enzyme activity of urokinase Plasminogen Activator within a Capan-2 pancreatic tumor model. After i.v. injection of a mixture of a uPA-responsive PARACEST agent and an unresponsive "control" PARACEST agent, CEST-FISP MR images were acquired for 18 minutes to monitor both agents. The initial increase in CEST effects in the tumor from both agents was equivalent indicating equivalent pharmacokinetics, but the CEST effect of the enzyme-responsive agent decreased more rapidly than the CEST effect of the control agent after 6 minutes, indicating that the agent was being cleaved by uPA.