Internalization of radiolabelled [DTPA0]octreotide and [DOTA0,Tyr3]octreotide: peptides for somatostatin receptor-targeted scintigraphy and radionuclide therapy.

We compared the internalization of [90Y-DOTA0,Tyr3]octreotide and [111In-DOTA0,Tyr3]octreotide with that of [125I-Tyr3]octreotide and [111In-DTPA0]octreotide in the subtype 2 somatostatin receptor (sst2)-positive rat pancreatic tumour cell lines CA20948 and AR42J and in the somatostatin receptor-negative human anaplastic thyroid tumour cell line ARO. We demonstrated that [111In-DTPA0]octreotide, [90Y-DOTA0,Tyr3]octreotide and [111In-DOTA0,Tyr3]octreotide are internalized by a receptor-specific, time- and temperature-dependent process. The amount of [90Y-DOTA0,Tyr3]octreotide internalized was higher than that of [111In-DOTA0,Tyr3]octreotide and [111In-DTPA0]octreotide.