title: Targeting Gastrointestinal Stromal Tumor with68Ga-Labeled Peptides: An In Vitro Study on Gastrointestinal Stromal Tumor-Cell Lines.
abstract: The gastrointestinal stromal tumor (GIST) is a rare disease with limited therapeutic options when resistance to tyrosine kinase inhibitor (TKI) treatment occurs. The authors investigated binding of various68Ga-labeled peptides, targeting receptors reported to be overexpressed in GIST, in different cell lines. For this purpose, three GIST cell lines were tested: GIST-T1, GIST882 (Imatinib sensitive), and GIST430 (Imatinib resistant). DOTA-NT 8-13 (targeting NTR1), DOTA-TATE (targeting SSTR2), CP04 (a minigastrin derivative targeting CCK2-R), VIP-DOTA (targeting VPAC2-R), and 2 DOTA-bombesin derivatives [targeting gastrin releasing peptide receptors (GRPR)] were radiolabeled with68Ga and incubated with the respective tumor cell and control cell lines. Membrane-bound and internalized activity was measured. Very low or no specific binding to GIST cells was found for all68Ga-labeled DOTA peptides except for bombesin derivatives indicating no or very low expression of respective receptors. Related to GRPR a pronounced specific binding to all GIST cell lines with no preference related to TKI resistance status was found, both for an agonist (AMBA) with high internalization and for an antagonist (NeoBOMB1) with mainly membrane-bound activity (with up to >80% bound/mg protein). GRPR expression was confirmed by immunohistochemistry. The results show that radiolabeled bombesin analogues, especially antagonists are very promising candidates for targeting GIST.
authors.affiliation: 1 Department of Nuclear Medicine, Medical University Innsbruck , Innsbruck, Austria .
authors.forename: Achim
authors.initials: A
authors.lastname: Paulmichl
authors.affiliation: 1 Department of Nuclear Medicine, Medical University Innsbruck , Innsbruck, Austria .
authors.forename: Dominik
authors.initials: D
authors.lastname: Summer
authors.affiliation: 2 Department of General Pathology, Medical University Innsbruck , Innsbruck, Austria .
authors.forename: Claudia
authors.initials: C
authors.lastname: Manzl
authors.affiliation: 1 Department of Nuclear Medicine, Medical University Innsbruck , Innsbruck, Austria .
authors.forename: Christine
authors.initials: C
authors.lastname: Rangger
authors.affiliation: 3 Advanced Accelerator Applications , Colleretto Giacosa, Italy .
authors.forename: Francesca
authors.initials: F
authors.lastname: Orlandi
authors.affiliation: 4 Division of Molecular Imaging and Radiochemistry, Department of Clinical Radiology and Nuclear Medicine, Medical Faculty Mannheim of Heidelberg University , Mannheim, Germany .
authors.forename: Sabrina
authors.initials: S
authors.lastname: Niedermoser
authors.affiliation: 5 Division of Human Health and Medical Science, Graduate School of Kuroshio Science, Kochi University , Nankoku, Japan .|6 Department of Molecular and Cellular Biology, Kochi Medical School , Nankoku, Japan .
authors.forename: Takahiro
authors.initials: T
authors.lastname: Taguchi
authors.affiliation: 4 Division of Molecular Imaging and Radiochemistry, Department of Clinical Radiology and Nuclear Medicine, Medical Faculty Mannheim of Heidelberg University , Mannheim, Germany .
authors.forename: Björn
authors.initials: B
authors.lastname: Wängler
authors.affiliation: 1 Department of Nuclear Medicine, Medical University Innsbruck , Innsbruck, Austria .
authors.forename: Clemens
authors.initials: C
authors.lastname: Decristoforo
mesh_terms: D001839:Bombesin / Q000493:pharmacokinetics / Q000494:pharmacology; D045744:Cell Line, Tumor; D056831:Coordination Complexes / Q000493:pharmacokinetics / Q000494:pharmacology; D005710:Gallium Radioisotopes / Q000494:pharmacology; D005770:Gastrointestinal Neoplasms / Q000378:metabolism / Q000532:radiotherapy*; D046152:Gastrointestinal Stromal Tumors / Q000378:metabolism / Q000532:radiotherapy*; D019073:HT29 Cells; D006801:Humans; D007150:Immunohistochemistry; D010455:Peptides / Q000493:pharmacokinetics / Q000494:pharmacology*
chemical_list: D056831:Coordination Complexes; D005710:Gallium Radioisotopes; D010455:Peptides; D001839:Bombesin
keywords: GIST; GRP; Ga-68; TKI resistance; bombesin; regulatory peptide