RT Journal Article SR Electronic T1 Increased Cell Death After Therapy with an Arg-Gly-Asp-Linked Somatostatin Analog JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1716 OP 1720 VO 45 IS 10 A1 Astrid Capello A1 Eric P. Krenning A1 Bert F. Bernard A1 Wout A.P. Breeman A1 Martin P. van Hagen A1 Marion de Jong YR 2004 UL http://jnm.snmjournals.org/content/45/10/1716.abstract AB Receptor-targeted scintigraphy and radionuclide therapy with radiolabeled somatostatin analogs are successfully applied for somatostatin receptor-positive tumors. The synergistic effects of an apoptosis-inducing factor, for example, the Arg-Gly-Asp (RGD) motif, can increase the radiotherapeutic efficacy of these peptides. Hence, the tumoricidal effects of the hybrid peptide RGD-diethylaminetriaminepentaacetic acid (DTPA)-Tyr3-octreotate (cyclic[c](Arg-Gly-Asp-d-Tyr-Asp)-Lys(DTPA)-d-Phe-c(Cys-Tyr-d-Trp-Lys-Thr-Cys)-Thr), hereafter referred to as RGD-DTPA-octreotate, were evaluated in comparison with those of RGD (c(Arg-Gly-Asp-d-Tyr-Asp)) and Tyr3-octreotate (d-Phe-c(Cys-Tyr-d-Trp-Lys-Thr-Cys)-Thr). Methods: The therapeutic effects of RGD-111In-DTPA-octreotate, 111In-DTPA-RGD, and 111In-DTPA-Tyr3-octreotate were investigated with various cell lines by use of a colony-forming assay, and caspase-3 activity was also determined. Results: Tumoricidal effects were found with 111In-DTPA-RGD, 111In-DTPA-Tyr3-octreotate, and RGD-111In-DTPA-octreotate, in order from least effective to most effective. Also, the largest increase in caspase-3 levels was found with RGD-111In-DTPA-octreotate. Conclusion: RGD-111In-DTPA-octreotate has more pronounced tumoricidal effects than 111In-DTPA-RGD and 111In-DTPA-Tyr3-octreotate, because of increased apoptosis, as indicated by increased caspase-3 activity.