Radiolabelled pyrimidine nucleosides to monitor the expression of HSV-1 thymidine kinase in gene therapy.

Selective radiolabelling and imaging of transduced HSV tk expressing cells was studied using [123I]IVFRU, [125I]FIRU and [125I]FIAU. Although all three radionucleosides accumulated in the KBALB-STK transduced murine tumour line in vitro and in vivo, [125I]FIRU provided optimal performance in terms of selectivity for HSV tk expressing cells and % of injected dose accumulating in the tumor.