Abstract #0036

Direct Detection of Cytosine Deaminase Enzymatic Activity Using CEST MRI

Guanshu Liu^1,2, Segun M. Bernard^2,3, Terence Tse², Piotr Walczak^2,3, Michael T. McMahon^1,2, Jeff W.M. Bulte^2,3, Peter C.M. van Zijl^1,2, Assaf A. Gilad^2,3

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.