Figure 7.

Panel A presents the structure of a PSMA theranostic agent that carries a prodrug enzyme to convert 5-fluorocytosine (5-FC) to 5-fluorouracil (5-FU) that is detected by ¹⁹F MRS and siRNA to downregulate choline kinase, thereby resulting in a decrease of total choline detected by ¹H MRSI. Panel B shows increased retention of the theranostic agent in a PSMA expressing tumor compared to a non-PSMA expressing tumor. Panel C indicates functional changes in tumor metabolism detected by ¹H MRSI and the formation of the cytotoxic drug 5-FU from 5-FC in the tumor detected by ¹⁹F MRS. Adapted from (103).