Fig. 4.

Increased CDA expression in tumor xenografts is sufficient to reduce plasma dC levels in mice and to increase dCK-dependent tumor [¹⁸F]CFA accumulation. (A) Experimental design and timeline. (B) Plasma dC levels in tumor-bearing mice were measured at the indicated times. On day 20 post-tumor inoculation, plasma dC concentration in the NSG mice injected with CEM-CDA cells was below 10 nM (gray circle), which corresponds to the lowest limit of detection of the LC-MS/MS-MRM assay. ***P < 0.001; n = 5 mice per group. (C) Representative PET/CT scans of a mouse that was serially imaged with [¹⁸F]CFA (day 17), with [¹⁸F]FDG (day 18), and then again with [¹⁸F]CFA on day 19, 2 h after treatment with DI-82 (50 mg/kg in 50% PEG/Tris, pH 7.4, by i.p. injection). GB, gallbladder; H, heart; %ID/g, percentage injected dose per gram; T, tumor. (D and E) Quantification of [¹⁸F]CFA and [¹⁸F]FDG PET/CT scans from C. N.S., nonsignificant; **P < 0.01; n = 5 mice per group.