Guanshu Liu1,2, Segun M. Bernard2,3, Terence Tse2, Piotr Walczak2,3, Michael T. McMahon1,2, Jeff W.M. Bulte2,3, Peter C.M. van Zijl1,2, Assaf A. Gilad2,3
1F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States; 2Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States; 3Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, United States
A new MRI method for assessing cytosine deaminase (CD) enzymatic activity was developed. This method allows the direct detection and quantification of CD by observing the changes in Chemical Exchange Saturation Transfer (CEST) signal when the substrates cytosine and 5-Fluorocytosine (5-FC) are converted to products uracil and 5-Fluorouracil (5-FU) by CD respectively. In addition, this method is capable of continuously monitoring the CD activity using the natural compounds in the cytosine/uracil system. Possible applications for this method include monitoring of in vivo CD activity and CD gene therapy for cancer.