MicroPET Imaging of Gene Transfer with a Somatostatin Receptor–Based Reporter Gene and ^94mTc-Demotate 1

Representative plot of ^94mTc-Demotate 1–Demotate 1 saturation binding curve (A) and Scatchard transformation (B) for membrane preparations from A-427 cells infected with AdHASSTR2 at 10 pfu per cell. It should be noted that ^94mTc-Demotate 1 concentrations included unlabeled Demotate 1 and that saturation binding curve represented specific binding (nonspecifically bound subtracted from total bound). Each data point represents mean ± SEM of triplicate measurements.

Specific internalization at 37°C of ^94mTc-Demotate 1 into A-427 cells infected with AdHASSTR2 at 10 pfu per cell. ^94mTc-Demotate 1 (1 nmol/L) was incubated with cells for various times in presence or absence of inhibitor. Cells were acid washed to remove surface-bound radioactivity and then were harvested to determine internalized radioactivity. Specific internalized radioactivity (internalized with inhibitor subtracted from internalized without inhibitor) (▪) and specific surface-bound radioactivity (surface bound with inhibitor subtracted from surface bound without inhibitor) (•) are shown. Data for each time point are presented as mean ± SEM of 2–5 experiments each performed in triplicate.

Biodistribution of ^94mTc-Demotate 1 in mice bearing A-427 tumor xenografts. Tumors were injected directly with either AdHASSTR2 or AdGRPR as control, and ^94mTc-Demotate 1 was injected via tail vein 2 d later. Mice were sacrificed 1 h (▪) and 2 h (□) later (n = 6 for each group). Data are presented as mean ± SEM %ID/g for each type of tissue (A) and as ratio of AdHASSTR2-injected tumor uptake to tissue uptake at both time points (B).