Nuclear uptake and dosimetry of 64Cu-labeled chelator somatostatin conjugates in an SSTr2-transfected human tumor cell line (original) (raw)
Related papers
Nuclear Medicine and Biology, 2005
Copper-64-labeled monoclonal antibodies (mAbs) have previously demonstrated unexpectedly effective tumor control in rodent models of cancer at relatively low tumor-absorbed radiation doses. This property has been associated with delivery platforms resulting in cellular internalization. The purpose of the present studies was to evaluate the in vitro internalization and in vivo distribution of a two-antibody model of 64 Cu radioimmunotherapy (RIT) in the same cell and animal models of cancer. Biodistributions of an internalizing antibody, cBR96, and a noninternalizing antibody, cT84.66, labeled with 64 Cu, were obtained in nude mice bearing LS174T colon carcinoma xenografts from 15 min to 48 h. The 64 Cu-DOTA-cBR96 conjugate demonstrated rapid tumor uptake, reaching 20.2% ID/g at 3 h and peaking at 35.4% ID/g by 24 h. Tumor accumulation of 64 Cu-DOTA-cT84.66 was more gradual, 8.19% ID/g at 3 h and 43.8% ID/g by 24 h, but maximum uptake was not statistically different from 64 Cu-DOTA-cBR96. Mouse xenograft dosimetry was estimated to be 1128 rad/mCi (304.9 mGy/MBq) for 64 Cu-DOTA-cBR96 and 1409 rad/mCi (380.5 mGy/MBq) for 64 Cu-DOTA-cT84.66. In LS174T cells, internalized radioactivity increased by a factor of 3.8 over 4 h for 64 Cu-DOTA-cBR96, but remained unchanged 64 Cu-DOTA-cT84.66. When normalized to uptake at 1 h, cellular efflux of 64 Cu was essentially identical for both mAbs. The biodistributions and tumor dosimetry of these internalizing and noninternalizing radiolabeled mAbs were sufficiently similar for direct comparison of the therapeutic efficacies of low doses of 64 Cu RIT agents in the same animal model of cancer. D 2005 Elsevier Inc. All rights reserved.
Cancer research, 2003
Copper-64 (T(1/2) = 12.7 h; beta(+), 17.4%; beta(-), 39%) has been used both in positron emission tomography imaging and in radiotherapy. Copper-64 radiopharmaceuticals have shown tumor growth inhibition with a relatively low radiation dose in animal models; however, the mechanism of cytotoxicity has not been fully elucidated. These studies incorporate the use of somatostatin receptor-positive AR42J rat pancreatic tumor cells in vitro to understand the cell killing mechanism of (64)Cu by focusing on subcellular distribution of the somatostatin analogues (64)Cu-labeled 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid-octreotide ((64)Cu-TETA-OC) and (111)In-labeled diethylenetriaminepentaacetic acid-octreotide ((111)In-DTPA-OC). Cell uptake and organelle isolation studies were conducted on (64)Cu-TETA-OC and (111)In-DTPA-OC. Nuclear localization of (64)Cu and (111)In from (64)Cu-TETA-OC and (111)In-DTPA-OC, respectively, increased over time, with 19.5 +/- 1.4% and 6.0 +/- 1...
Bioconjugate Chemistry, 1996
The bifunctional chelating agents (BFCs), 6-[p-(bromoacetamido)benzyl]-1, , 6-[p-(isothiocyanato)benzyl]-1, methyl]benzoic acid (CPTA), and 1- [(1,4,7,10,13-pentaazacyclopentadec-1-yl)methyl]benzoic acid (PCBA), were synthesized and conjugated to the anti-colorectal monoclonal antibody (mAb), 1A3, and antibody fragments, 1A3-F(ab′) 2 , for radiolabeling with 64,67 Cu and comparison in animal models. In vivo metabolism studies were carried out in liver and kidneys in order to correlate the nature of the metabolites formed to the uptake and retention of the radiolabel in each organ. Animal biodistribution studies were performed in Golden Syrian hamsters bearing the GW39 human colon cancer tumors and in normal Sprague-Dawley rats. All conjugates showed good tumor uptake in hamsters. Biodistribution in rats showed that 64 Cu-BAT-2IT-1A3 had the lowest liver and kidney uptake of the intact 1A3 conjugates (p < 0.03), whereas in hamsters, there were no significant differences in liver and kidney uptake between the four intact BFC-1A3 conjugates. Tumor-bearing hamsters injected with 64 Cu-CPTA-1A3-F(ab′) 2 and 64 Cu-PCBA-1A3-F(ab′) 2 had from 3 to 7 times greater uptake in the kidneys than hamsters given 64 Cu-labeled BAT and SCN-TETA 1A3-F(ab′) 2 conjugates, while rats injected with 64 Cu-CPTA-1A3-F(ab′) 2 and 64 Cu-PCBA-1A3-F(ab′) 2 had nearly twice the uptake. The in vivo metabolism of the mAbs 1A3 and 1A3-F(ab′) 2 radiolabeled with 67 Cu through the SCN-TETA, CPTA, and PCBA BFCs was investigated by excising the livers and kidneys of normal rats from 1-5 days post-injection of the radiolabeled conjugates. Liver and kidney homogenates were analyzed by size exclusion chromatography and thin layer chromatography (TLC). The size exclusion chromatography data showed that all of the 67 Cu-labeled 1A3-F(ab′) 2 conjugates were >85% degraded in the kidneys to small molecular weight metabolites by 1 day post-injection. In contrast, in the liver at 1 day post-injection, greater than 70% of the 67 Cu-labeled 1A3 conjugates were unmetabolized. By day 5, a 35 kDa peak appeared in the liver of rats injected with the 67 Cu-labeled 1A3 conjugates, possibly due to transchelation of the 67 Cu to proteins. Superoxide dismutase chromatographically elutes at the same retention time as this 67 Cu-labeled metabolite. The TLC data indicate that the low molecular weight metabolite (<5 kDa) of both 67 Cu-CPTA-1A3 and 67 Cu-CPTA-1A3-F(ab′) 2 conjugates co-chromatographed with a 67 Cu-CPTA--lysine standard. Our data suggest that chelate charge and lipophilicity play a large role in kidney retention of 64/67 Cu-labeled BFC-1A3-F(ab′) 2 conjugates, while transchelation of the copper label appears to be the major factor for liver accumulation of 64/67 Cu-labeled BFC-1A3 conjugates.
Evaluation of novel bifunctional chelates for the development of Cu-64-based radiopharmaceuticals
Nuclear Medicine and Biology, 2008
Background: Currently available bifunctional chelates (BFCs) for attaching Cu-64 to a targeting molecule are limited by either their radiolabeling conditions or in vivo stability. With the goal of identifying highly effective BFCs, we compared the properties of two novel BFCs, 1-oxa-4,7,10-triazacyclododecane-S-5-(4-nitrobenzyl)-4,7,10-triacetic acid (p-NO 2 -Bn-Oxo) and 3,6,9,15-tetraazabicyclo[9.3.1] pentadeca-1(15),11,13-triene-S-4-(4-nitrobenzyl)-3,6,9-triacetic acid (p-NO 2 -Bn-PCTA), with the commonly used S-2-(4-nitrobenzyl)-1,4,7,10-tetraazacyclododecanetetraacetic acid (p-NO 2 -Bn-DOTA). Methods: p-NO 2 -Bn-DOTA, p-NO 2 -Bn-Oxo and p-NO 2 -Bn-PCTA were each radiolabeled with Cu-64 under various conditions to assess the reaction kinetics and robustness of the radiolabeling. Stability of each Cu-64 BFC complex was evaluated at low pH and in serum. Small animal positron emission tomography imaging and biodistribution studies in mice were undertaken. Results: p-NO 2 -Bn-Oxo and p-NO 2 -Bn-PCTA possessed superior reaction kinetics compared to p-NO 2 -Bn-DOTA under all radiolabeling conditions; N98% radiochemical yields were achieved in b5 min at room temperature even when using near stoichiometric amounts of BFC. Under nonideal conditions, such as low or high pH, high radiochemical yields were still achievable with the novel BFCs. The radiolabeled compounds were stable in serum and at pH 2 for 48 h. The imaging and biodistribution of the Cu-64-radiolabeled BFCs illustrated differences between the BFCs, including preferential clearance via the kidneys for the p-NO 2 -Bn-PCTA Cu-64 complex. Conclusions: The novel BFCs facilitated efficient Cu-64 radiolabeling under mild conditions to produce stable complexes at potentially high specific activities. These BFCs may find wide utility in the development of Cu-64-based radiopharmaceuticals.
EJNMMI Research, 2018
Background: The aim of the present study is to evaluate the kinetics and dosimetry of 64 CuCl 2 in human prostate cancer (PCa) lesions. We prospectively evaluated 50 PCa patients with biochemical relapse after surgery or external beam radiation therapy. All patients underwent 64 CuCl 2-PET/CT to detect PCa recurrence/metastases. Volumes of interest were manually drawn for each 64 CuCl 2 avid PCa lesion with a diameter > 1 cm on mpMRI in each patient. Time-activity curves for all lesions were obtained. The effective and biological half-life and the standard uptake values (SUVs) were calculated. Tumour/background ratio (TBR) curves as a function of time were considered. Finally, the absorbed dose per lesion was estimated. Results: The mean effective half-life of 64 CuCl 2 calculated in the lymph nodes (10.2 ± 1.7 h) was significantly higher than in local relapses (8.8 ± 1.1 h) and similar to that seen in bone metastases (9.0 ± 0.4 h). The mean 64 CuCl 2 SUV max calculated 1 h after tracer injection was significantly higher in the lymph nodes (6.8 ± 4.3) and bone metastases (6.8 ± 2.9) than in local relapses (4.7 ± 2.4). TBR mean curve of 64 CuCl 2 revealed that the calculated TBR max value was 5.0, 7.0, and 6.2 in local relapse and lymph node and bone metastases, respectively, and it was achieved about 1 h after 64 CuCl 2 injection. The mean absorbed dose of the PCa lesions per administrated activity was 6.00E-2 ± 4.74E-2mGy/MBq. Indeed, for an administered activity of 3.7 GBq, the mean dose absorbed by the lesion would be 0.22 Gy. Conclusions: Dosimetry showed that the dose absorbed by PCa recurrences/metastases per administrated activity was low. The dosimetric study performed does not take into account the possible therapeutic effect of the Auger electrons. Clinical trials are needed to evaluate 64 Cu internalization in the cell nucleus that seems related to the therapeutic effectiveness reported in preclinical studies.
EJNMMI research, 2017
In recent years, Copper-64 (T1/2 = 12.7 h) in the chemical form of copper dichloride ([64Cu]CuCl2) has been identified as a potential agent for PET imaging and radionuclide therapy targeting the human copper transporter 1, which is overexpressed in a variety of cancer cells. Limited human biodistribution and radiation dosimetry data is available for this tracer. The aim of this research was to determine the biodistribution and estimate the radiation dosimetry of [64Cu]CuCl2, using whole-body (WB) PET scans in healthy volunteers. Six healthy volunteers were included in this study (3 women and 3 men, mean age ± SD, 54.3 ± 8.6 years; mean weight ± SD, 77.2 ± 12.4 kg). After intravenous injection of the tracer (4.0 MBq/kg), three consecutive WB emission scans were acquired at 5, 30, and 60 min after injection. Additional scans were acquired at 5, 9, and 24 h post-injection. Low-dose CT scan without contrast was used for anatomic localization and attenuation correction. OLINDA/EXM softwa...
Basic characterization of 64Cu-ATSM as a radiotherapy agent
Nuclear Medicine and Biology, 2005
64 Cu-diacetyl-bis(N 4 -methylthiosemicarbazone) ( 64 Cu-ATSM) is a promising radiotherapy agent for the treatment of hypoxic tumors. In an attempt to elucidate the radiobiological basis of 64 Cu-ATSM radiotherapy, we have investigated the cellular response patterns in vitro cell line models. Cells were incubated with 64 Cu-ATSM, and the dose-response curves were obtained by performing a clonogenic survival assay. Radiation-induced damage in DNA was evaluated using the alkali comet assay and apoptotic cells were detected using Annexin V-FITC and propidium iodide staining methods. Washout rate and subcellular distribution of 64 Cu in cells were investigated to further assess the effectiveness of 64 Cu-ATSM therapy on a molecular basis. A direct comparison of subcellular localization of Cu-ATSM was made with the flow tracer analog Cu-pyruvladehyde-bis(N 4 -methylthiosemicarbazone). In this study, 64 Cu-ATSM was shown to reduce the clonogenic survival rate of tumor cells in a dose-dependent manner. Under hypoxic conditions, cells took up 64 Cu-ATSM and radioactive 64 Cu was highly accumulated in the cells. In the 64 Cu-ATSM-treated cells, DNA damage by the radiation emitted from 64 Cu was detected, and inhibition of cell proliferation and induction of apoptosis was observed at 24 and 36 h after the treatment. The typical features of postmitotic apoptosis induced by radiation were observed following 64 Cu-ATSM treatment. The majority of the 64 Cu taken up into the cells remained in the postmitochondrial supernatant (the cellular residue after removal of the nuclei and mitochondria), which indicates that the h À particle emitted from 64 Cu may be as effective as the Auger electrons in 64 Cu-ATSM therapy. These data allow us to postulate that 64 Cu-ATSM will be able to attack the hypoxic tumor cells directly, as well as potentially affecting the peripheral nonhypoxic regions indirectly by the h À particle decay of 64 Cu. D