In vivo specificity of [125I]I-Tyr-PEG2-RM26 and [111In]In-DOTA-PEG2-RM26 binding to GRPR-expressing PC-3 in tumour xenografts was evaluated by saturation of receptors using a co-injection of non-labelled peptide (NOTA-PEG4-RM26) (Figure 7) at 0.5 h after injection. This evidence concerns the gene GRPR and neoplasm.