In PC3-PIP tumor-bearing mice, high background activities were observed and reasonable tumor-to-background ratios could only be obtained after 24 or 72 h p.i. Thus, a target-specific uptake by both GRPR and PSMA could only be shown for [125I]I-9, exhibiting the lowest lipophilicity in the line of compounds evaluated. This evidence concerns the gene FOLH1 and neoplasm.