Evidence of 68Ga-DOTA-NT-20.3 Uptake in Pancreatic Adenocarcinoma AsPC-1 Cell Line – in vitro Study

Abstract

Background Neurotensin receptors are overexpressed in several cancer types including pancreatic ductal adenocarcinoma. Three NTR subtypes have been cloned: NTR-1, NTR-2 and NTR-3. The most expressed NTR-1 is not present in normal pancreatic tissue and has a low expression in chronic pancreatitis. Objective Objective of this study was to test in vitro affinity of the new 68Ga labelled neurotensin analogue DOTA-NT-20.3 (fragment 6-13, Ac-Lys(DOTA)-Pro-Arg(N-CH3)-Arg-Pro-Tyr-Tle-Leu) on the human pancreatic ductal adenocarcinoma cell line AsPC-1. Method For the preparation of 68Ga-DOTA-NT-20.3, 68GaCl3 solution (eluted from 68Ge/68Ga generator) and 50 µg of precursor (Iason, Graz, Austria) water dissolved were used in an automatic synthesis module. The labeled compound was added to cell culture flask and incubated at 37°C. At various time points after tracer addition up to 80min, cells were recovered, rinsed and counted for radioactivity. Results were expressed as percent binding normalized to 200000 cells and affinity parameters were calculated. Results Labeling yield was ≥98 %. The molar ratio between labelled and total peptide was about 1/400. AsPC-1 cell line showed rapid uptake of the tracer including surface and internalized binding, tending to a plateau phase 80 min after tracer addition (11%/200.000 cells). The Kd (7.335 pmol) and Bmax (90.52 kBq) value indicated high tracer affinity for AsPC-1cell line especially if compared with the literature data regarding other malignancies (e.g. colonic cancer cell line). Binding sites were 1.09x106 sites per cell. Conclusion New tracer 68Ga-DOTA-NT-20.3 can be a suitable candidate for the clinical use in patients with pancreatic ductal adenocarcinoma.

Design of Bimodal Ligands of Neurotensin Receptor 1 for Positron Emission Tomography Imaging and Fluorescence-Guided Surgery of Pancreatic Cancer

“…A series of bimodal agents was synthesized (Scheme ). Their structure derives from the sequence of the well-validated peptide agonist NT-20.3 (Ac-Lys-Pro-N-Me-Arg-Arg-Pro-Tyr-Tle-Leu-OH). − , A lysine residue was introduced at the N-terminal end of the peptide to conjugate the radiometal chelator and the fluorophore, and different spacers were inserted before the lysine: no spacer, a PEG 2 analogue (8-amino-3,6-dioxaoctanoic acid, or AEEAc), or a PEG 4 chain.…”

“…Their structure derives from the sequence of the well-validated peptide agonist NT-20.3 (Ac-Lys-Pro-N-Me-Arg-Arg-Pro-Tyr-Tle-Leu-OH). [21][22][23]26 A lysine residue was introduced at the N-terminal end of the peptide to conjugate the radiometal chelator and the fluorophore, and different spacers were inserted before the lysine: no spacer, a PEG 2 analogue (8-amino-3,6-dioxaoctanoic acid, or AEEAc), or a PEG 4 chain. For the PET modality, we chose to use 68 Ga among other positron-emitting radioisotopes because its short physical halflife matches well with the rapid pharmacokinetics of peptides, and it provides safer dosimetry for the patients compared to 64 Cu.…”

Molecular imaging of pancreatic ductal adenocarcinoma

“…82 Neurotensin (NT) is the endogenous ligand of NTR1 and NT-20.3 is an NT(6−13) analogue, showed an excellent affinity for NTR1. 83 After demonstrating binding affinity to cell lines, 84 preclinical researches showed that NT-20.3-based probes were excellent candidates for imaging and therapy of NTR-1-positive PDAC models. 85 Building on previous success, a recent small trial performed by Hodolic et al on three patients with PDAC showed that 68 Ga-NT-20.3 was safe and well tolerated.…”

New Isotopes for the Treatment of Pancreatic Cancer in Collaboration With CERN: A Mini Review

“…In pancreatic adenocarcinoma cells, there is an overexpression of neurotensin receptors, which can be targeted with radiolabelled neurotensin analogs (21). In vitro studies showed a high affinity of the 68 Ga-labeled neurotensin analog ( 68 Ga-DOTA-NT-20.3) for the human pancreatic ductal adenocarcinoma cell line AsPC-1 (22).…”