The copper radioisotopes: a systematic review with special interest to 64Cu. Biomed Res Int. 2014;2014:786463. [PMID: 24895611 PMCID: PMC4033511 DOI: 10.1155/2014/786463]

Alpha and Beta Radiation for Theragnostics

Targeted radionuclide therapy (TRT) has significantly evolved from its beginnings with iodine-131 to employing carrier molecules with beta emitting isotopes like lutetium-177. With the success of Lu-177-DOTATATE for neuroendocrine tumors and Lu-177-PSMA-617 for prostate cancer, several other beta emitting radioisotopes, such as Cu-67 and Tb-161, are being explored for TRT. The field has also expanded into targeted alpha therapy (TAT) with agents like radium-223 for bone metastases in prostate cancer, and several other alpha emitter radioisotopes with carrier molecules, such as Ac-225, and Pb-212 under clinical trials. Despite these advancements, the scope of TRT in treating diverse solid tumors and integration with other therapies like immunotherapy remains under investigation. The success of antibody-drug conjugates further complements treatments with TRT, though challenges in treatment optimization continue.

Multistep synthesis of a novel copper complex with potential for Alzheimer's disease diagnosis

Positron emission tomography (PET) imaging of Aβ plaques, is recognized as a tool for the diagnosis of Alzheimer's disease. As a contribution to the development of new strategies for early diagnosis of the disease, using PET medical imaging technique, a new copper complex, the [Cu(TE1PA-ONO)]+ was synthesized in ten steps. The key step of our strategy is the coupling of a monopicolinate-N-alkylated cyclam-based ligand with a moiety capable of recognizing Aβ plaques via a successful and challenging Buchwald-Hartwig coupling reaction. To our knowledge, it is the first time that such a strategy is used to functionalize polyazamacrocyclic derivatives. The thermodynamic stability constants determined in MeOH/H2O solvent indicate that the attachment of this moiety does not weaken the chelating properties of TE1PA-ONO ligand in relation to parent HTE1PA. The novel complex described here is able to recognize amyloid plaques in brain sections from Alzheimer's disease patients and shows low toxicity to human neuronal cells.

Emerging roles of the copper-CTR1 axis in tumorigenesis

Physiological roles of copper in metabolic homeostasis have been well established, however, whether and how copper is dysregulated in tumors and contributes to tumorigenesis are not recapitulated. Here, we comprehensively summarize the potential origins of copper accumulation in diseases especially in cancers by dysregulating copper transporter 1 (CTR1) or ATPase copper transporting alpha/beta (ATP7A/B) and further demonstrate the underlying mechanism of copper contributing to tumorigenesis. Specifically, in addition to modulating reactive oxygen species (ROS), angiogenesis, immune response, and metabolic homeostasis, copper recently has drawn more attention by directly binding to oncoproteins such as MEK, ULK, Memo, and PDK1 to activate distinct oncogenic signals and account for tumorigenesis. In the end, we disclose the emerging applications of copper in cancer diagnosis and highlight the promising strategies to target the copper-CTR1 axis for cancer therapies.

The Chemical Scaffold of Theranostic Radiopharmaceuticals: Radionuclide, Bifunctional Chelator, and Pharmacokinetics Modifying Linker

Therapeutic radiopharmaceuticals have been researched extensively in the last decade as a result of the growing research interest in personalized medicine to improve diagnostic accuracy and intensify intensive therapy while limiting side effects. Radiometal-based drugs are of substantial interest because of their greater versatility for clinical translation compared to non-metal radionuclides. This paper comprehensively discusses various components commonly used as chemical scaffolds to build radiopharmaceutical agents, i.e., radionuclides, pharmacokinetic-modifying linkers, and chelators, whose characteristics are explained and can be used as a guide for the researcher.

A New Preclinical Decision Support System Based on PET Radiomics: A Preliminary Study on the Evaluation of an Innovative 64Cu-Labeled Chelator in Mouse Models

The 64Cu-labeled chelator was analyzed in vivo by positron emission tomography (PET) imaging to evaluate its biodistribution in a murine model at different acquisition times. For this purpose, nine 6-week-old female Balb/C nude strain mice underwent micro-PET imaging at three different time points after 64Cu-labeled chelator injection. Specifically, the mice were divided into group 1 (acquisition 1 h after [64Cu] chelator administration, n = 3 mice), group 2 (acquisition 4 h after [64Cu]chelator administration, n = 3 mice), and group 3 (acquisition 24 h after [64Cu] chelator administration, n = 3 mice). Successively, all PET studies were segmented by means of registration with a standard template space (3D whole-body Digimouse atlas), and 108 radiomics features were extracted from seven organs (namely, heart, bladder, stomach, liver, spleen, kidney, and lung) to investigate possible changes over time in [64Cu]chelator biodistribution. The one-way analysis of variance and post hoc Tukey Honestly Significant Difference test revealed that, while heart, stomach, spleen, kidney, and lung districts showed a very low percentage of radiomics features with significant variations (p-value < 0.05) among the three groups of mice, a large number of features (greater than 60% and 50%, respectively) that varied significantly between groups were observed in bladder and liver, indicating a different in vivo uptake of the 64Cu-labeled chelator over time. The proposed methodology may improve the method of calculating the [64Cu]chelator biodistribution and open the way towards a decision support system in the field of new radiopharmaceuticals used in preclinical imaging trials.

Review: PET imaging with macro- and middle-sized molecular probes

Recent progress in radiolabeling of macro- and middle-sized molecular probes has been extending possibilities to use PET molecular imaging for dynamic application to drug development and therapeutic evaluation. Theranostics concept also accelerated the use of macro- and middle-sized molecular probes for sharpening the contrast of proper target recognition even the cellular types/subtypes and proper selection of the patients who should be treated by the same molecules recognition. Here, brief summary of the present status of immuno-PET, and then further development of advanced technologies related to immuno-PET, peptidic PET probes, and nucleic acids PET probes are described.

Europium-Diethylenetriaminepentaacetic Acid Loaded Radioluminescence Liposome Nanoplatform for Effective Radioisotope-Mediated Photodynamic Therapy

Photodynamic therapy (PDT) is an effective anticancer strategy with a higher selectivity and fewer adverse effects than conventional therapies; however, shallow tissue penetration depth of light has hampered the clinical utility of PDT. Recently, reports have indicated that Cerenkov luminescence-induced PDT may overcome the tissue penetration limitation of conventional PDT. However, the effectiveness of this method is controversial because of its low luminescence intensity. Herein, we developed a radiolabeled diethylenetriaminepentaacetic acid chelated Eu³⁺ (Eu-DTPA)/photosensitizer (PS) loaded liposome (Eu/PS-lipo) that utilizes ionizing radiation from radioisotopes for effective in vivo imaging and radioluminescence-induced PDT. We utilized Victoria blue-BO (VBBO) as a PS and observed an efficient luminescence resonance energy transfer between Eu-DTPA and VBBO. Furthermore, ⁶⁴Cu-labeled Eu lipo demonstrated a strong radioluminescence with a 2-fold higher intensity than Cerenkov luminescence from free ⁶⁴Cu. In our radioluminescence liposome, radioluminescence energy transfer showed a 6-fold higher energy transfer efficiency to VBBO than Cerenkov luminescence energy transfer (CLET). ⁶⁴Cu-labeled Eu/VBBO lipo (⁶⁴Cu-Eu/VBBO lipo) showed a substantial tumor uptake of up to 19.3%ID/g by enhanced permeability and retention effects, as revealed by in vivo positron emission tomography. Finally, the PDT using ⁶⁴Cu-Eu/VBBO lipo demonstrated significantly higher in vitro and in vivo therapeutic effects than Cerenkov luminescence-induced PDT using ⁶⁴Cu-VBBO lipo. This study envisions a great opportunity for clinical PDT application by establishing the radioluminescence liposome which has high tumor targeting and efficient energy transfer capability from radioisotopes.

Mild and efficient 64Cu labeling of perhydro-1, 4-diazepine derivatives for potential use with large peptides, proteins and antibodies

DATA (6-Amino-1,4-diazapine-triacetate) and AAZTA (6-Amino-1,4-diazapine-tetracetate) chelators represent a novel approach representing hybrid-chelates: possessing significant cyclic and acyclic character. It is believed that flexibility of the acyclic part facilitates rapid complexation, whilst the preorganized cyclic part minimizes the energy barrier to complexation and inhibits decomplexation processes. So far, these chelators have been used exclusively with 44Sc and 68Ga only. Recent results with natCu predict high stabilities for Cu-AAZTA, yet no radioactive labeling of AAZTA or DATA with 64Cu or any additional radioactive isotope has been reported. We present the one pot synthesis of the bifunctional derivatives AAZTA5OMe and DATA5mOMe and their labeling with 64Cu. In addition, in vitro stability of the respective complexes are presented.

Biological Applications of Thiocarbohydrazones and Their Metal Complexes: A Perspective Review

Although organic compounds account for more than 99% of currently approved clinical drugs, the established clinical use of cisplatin in cancer or auranofin in rheumatoid arthritis have paved the way to several research initiatives to identify metal-based drugs for a wide range of human diseases. Nitrogen and sulfur donor ligands, characterized by different binding motifs, have been the subject in recent years of one of the main research areas in coordination chemistry. Among the nitrogen/sulfur compounds, very little is known about thiocarbohydrazones (TCH), the higher homologues of the well-known thiosemicarbazones (TSC), and their metal complexes. The extra hydrazine moiety provides the ligands of variable metal binding modes, structural diversity and promising biological implications. The interesting coordination chemistry of TCH has mainly been focused on symmetric derivatives, which are relatively simple to synthesize while few examples of asymmetric ligands have been reported. This informative review on TCHs and their metal complexes will be helpful for improving the design of metal-based pharmaceuticals for applications ranging from anticancer to antinfective therapy.

64Cu-based Radiopharmaceuticals in Molecular Imaging

Copper-64 (T_1/2 = 12.7 hours; β⁺: 19%, β^-: 38%) has a unique decay profile and can be used for positron emission tomography imaging and radionuclide therapy. The well-established coordination chemistry of copper allows for its reaction with different types of chelator systems. It can be linked to antibodies, proteins, peptides, and other biologically relevant small molecules. Two potential ways to produce copper-64 radioisotopes concern the use of the cyclotron or the reactor. This review summarized several commonly used biomarkers of copper-64 radionuclide.

Preparation of Zirconium-89 Solutions for Radiopharmaceutical Purposes: Interrelation Between Formulation, Radiochemical Purity, Stability and Biodistribution

Zirconium-89 is a promising radionuclide for nuclear medicine. The aim of the present work was to find a suitable method for obtaining zirconium-89 solutions for radiopharmaceutical purposes. For this purpose, the ion exchange behavior of zirconium-89 solutions was studied. Radio-TLC (thin layer chromatography) and biodistribution studies were carried out to understand speciation of zirconium-89 complexes and their role in the development of new radiopharmaceuticals. Three methods of zirconium-89 isolation were studied using ZR (hydroxamate) and Chelex-100 resins. It was found that ZR-resin alone is not enough to obtain stable zirconium-89 formulations. An easy and effective method of reconstitution of [⁸⁹Zr]Zr-oxalate to [⁸⁹Zr]Zr-citrate using Chelex-100 resin was developed. Developed procedures allow obtaining [⁸⁹Zr]Zr-oxalate (in 0.1 M sodium oxalate solution) and [⁸⁹Zr]Zr-citrate (in 0.1–1.0 M sodium citrate solution). These solutions are perfectly suitable and convenient for radiopharmaceutical purposes. Our results prove [⁸⁹Zr]Zr-citrate to be advantageous over [⁸⁹Zr]Zr-oxalate. During evaluation of speciation of zirconium-89 complexes, a new TLC method was developed, since it was proved that there is no comprehensive method for analysis or zirconium-89 preparations. The new method provides valuable insights about the content of “active” ionic form of zirconium-89. The interrelation of the chromatographic behavior of zirconium-89 preparations and their biodistribution was studied.

Calculations of dose point kernels of 64 Cu in different media with PENELOPE Monte Carlo code

PURPOSE

The unique decay properties of copper-64 (⁶⁴ Cu) has made it a radionuclide of interest in theragnostic applications of nuclear medicine. This study aims to calculate the dose point kernels (DPKs) of ⁶⁴ Cu in various media with PENELOPE Monte Carlo code.

METHODS

Monte Carlo simulations were performed using PENELOPE code (version 2014). To calculate DPKs, the simulation comprised an isotropic point radiation source positioned at the origin of a spherical object of radius 50 cm. The absorbed dose along the radial direction outwards from the point source were scored with a resolution of 20 μm. Validations were firstly performed by calculating the DPKs of monoenergetic electrons and photons in water and the results were compared against the literature values. The continuous energy spectra of the beta minus and positron emissions from ⁶⁴ Cu were numerically modeled and used as inputs to the simulation. DPKs of ⁶⁴ Cu were calculated in water, soft tissue, lung tissue, and cortical bone, including all emissions types.

RESULTS

The simulations have been successfully validated against literature values. The largest deviations have been observed with 10 keV monoenergetic electrons with the average and maximum dose difference of -1.01% and -10.56%. The modeled energy spectra closely compared with the average energies from Brookhaven Laboratory National Nuclear Data Centre and the combined spectral shapes from the RAdiation Dose Assessment Resource (RADAR). The DPKs of ⁶⁴ Cu demonstrated different radial dose deposition in different media owing to the different physical density and effective atomic number.

CONCLUSIONS

The DPKs of ⁶⁴ Cu have been calculated with Monte Carlo simulations in four different media. They will be useful to study the dosimetric properties of ⁶⁴ Cu-labeled radiopharmaceuticals and perform therapeutic dose planning.

Application of Immuno-PET in Antibody-Drug Conjugate Development

Targeted therapies hold great promise for cancer treatment and may exhibit even greater efficacy when combined with patient selection tools. The clinical impact of identifying likely responders includes reducing the number of unnecessary and ineffective therapies as well as more accurately determining drug effects. Positron emission tomography (PET) imaging using zirconium-89 radiolabeled monoclonal antibodies (mAbs), also referred to as zirconium-89 (⁸⁹Zr)-immuno-PET, provides a potential biomarker to measure target expression and verify optimal delivery of targeted agents to tumors. Antibody-drug conjugates (ADCs) combine the high affinity and specificity of mAbs with the potency of cytotoxic drugs to target tumor-expressing antigen and destroy cancer cells. Thus, ⁸⁹Zr-immuno-PET of whole-body biodistribution, pharmacokinetics, and tumor targeting of antibodies and ADCs to predict toxicity and efficacy could help guide individualized treatment. Here, we review how ⁸⁹Zr-immuno-PET is being used as a companion diagnostic with the development of ADCs. Furthermore, we discuss how ⁸⁹Zr-immuno-PET may be utilized in future clinical trials as an adjunct tool with novel ADCs to select cancer patients who have the greatest potential to benefit from treatment and improve ADC dosing regimens.

Radiobiological Characterization of 64CuCl₂ as a Simple Tool for Prostate Cancer Theranostics

⁶⁴CuCl₂ has recently been proposed as a promising agent for prostate cancer (PCa) theranostics, based on preclinical studies in cellular and animal models, and on the increasing number of human studies documenting its use for PCa diagnosis. Nevertheless, the use of ⁶⁴CuCl₂ raises important radiobiological questions that have yet to be addressed. In this work, using a panel of PCa cell lines in comparison with a non-tumoral prostate cell line, we combined cytogenetic approaches with radiocytotoxicity assays to obtain significant insights into the cellular consequences of exposure to ⁶⁴CuCl₂. PCa cells were found to exhibit increased ⁶⁴CuCl₂ uptake, which could not be attributed to increased expression of the main copper cellular importer, hCtr1, as had been previously suggested. Early DNA damage and genomic instability were also higher in PCa cells, with the tumoral cell lines exhibiting deficient DNA-damage repair upon exposure to ⁶⁴CuCl₂. This was corroborated by the observation that ⁶⁴CuCl₂ was more cytotoxic in PCa cells than in non-tumoral cells. Overall, we showed for the first time that PCa cells had a higher sensitivity to ⁶⁴CuCl₂ than healthy cells, supporting the idea that this compound deserved to be further evaluated as a theranostic agent in PCa.

Porphyrins as ligands for 64copper: background and trends

Porphyrins and 64Cu have emerged as a novel synergic option for applications in PET molecular imaging. Both the characteristics and photophysical properties of macrocyclic porphyrins and the relatively long half-life of the copper isotope, in addition to the increased tumor-specific uptake of porphyrins compared to normal cells, make this complex an attractive option not only for diagnosis but also for therapeutic applications. Herein, we present an overview of the latest results on the development of PET agents based on porphyrins and 64Cu, including methods used to improve the selectivity of these macrocycles when conjugated with biological units such as monoclonal antibodies, peptides or proteins.

PET radiometals for antibody labeling

Recent advances in molecular characterization of tumors have made possible the emergence of new types of cancer therapies where traditional cytotoxic drugs and nonspecific chemotherapy can be complemented with targeted molecular therapies. One of the main revolutionary treatments is the use of monoclonal antibodies (mAbs) that selectively target the disseminated tumor cells while sparing normal tissues. mAbs and related therapeutics can be efficiently radiolabeled with a wide range of radionuclides to facilitate preclinical and clinical studies. Non-invasive molecular imaging techniques, such as Positron Emission Tomography (PET), using radiolabeled mAbs provide useful information on the whole-body distribution of the biomolecules, which may enable patient stratification, diagnosis, selection of targeted therapies, evaluation of treatment response, and prediction of dose limiting tissue and adverse effects. In addition, when mAbs are labeled with therapeutic radionuclides, the combination of immunological and radiobiological cytotoxicity may result in enhanced treatment efficacy. The pharmacokinetic profile of antibodies demands the use of long half-life isotopes for longitudinal scrutiny of mAb biodistribution and precludes the use of well-stablished short half-life isotopes. Herein, we review the most promising PET radiometals with chemical and physical characteristics that make the appealing for mAb labeling, highlighting those with theranostic radioisotopes.

Radiopharmaceuticals for Assessment of Altered Metabolism and Biometal Fluxes in Brain Aging and Alzheimer's Disease with Positron Emission Tomography

Aging is a risk factor for Alzheimer's disease (AD). There are changes of brain metabolism and biometal fluxes due to brain aging, which may play a role in pathogenesis of AD. Positron emission tomography (PET) is a versatile tool for tracking alteration of metabolism and biometal fluxes due to brain aging and AD. Age-dependent changes in cerebral glucose metabolism can be tracked with PET using 2-deoxy-2-[18F]-fluoro-D-glucose (18F-FDG), a radiolabeled glucose analogue, as a radiotracer. Based on different patterns of altered cerebral glucose metabolism, 18F-FDG PET was clinically used for differential diagnosis of AD and Frontotemporal dementia (FTD). There are continued efforts to develop additional radiopharmaceuticals or radiotracers for assessment of age-dependent changes of various metabolic pathways and biometal fluxes due to brain aging and AD with PET. Elucidation of age-dependent changes of brain metabolism and altered biometal fluxes is not only significant for a better mechanistic understanding of brain aging and the pathophysiology of AD, but also significant for identification of new targets for the prevention, early diagnosis, and treatment of AD.

Copper Selective Polymeric Extractant Synthesized by Ring-Opening Metathesis Polymerization

Novel polymers bearing pendant picolinic acid functionalities have been synthesized by ring-opening metathesis polymerization (ROMP) for applications in separations-based purification protocols. These polymers and their corresponding monomer were shown to be selective for Cu²⁺ over a variety of other divalent metal cations as inferred from pH dependent studies carried out under both liquid-liquid and solid-liquid extraction conditions. The polymer system of this study also showed high selectivity for Cu²⁺ over Ni²⁺ in mock protocols that could be relevant to the purification of Cu radioisotopes. Separation factors as high as 290 were achieved for extractions from solutions containing a 100-fold excess of Ni²⁺ relative to Cu²⁺.

Determination of photon emission probability for the main gamma ray and half-life measurements of 64Cu

The National Institute of Standards and Technology (NIST) performed new standardization measurements for 64Cu. As part of this work the photon emission probability for the main gamma-ray line and the half-life were determined using several high-purity germanium (HPGe) detectors. Half-life determinations were also carried out with a NaI(Tl) well counter and two pressurized ionization chambers.

The role of radionuclide probes for monitoring anti-tumor drugs efficacy: A brief review

Despite recent advances in the development of new therapeutic agents and diagnostic imaging modalities, cancer is still one of the main causes of death worldwide. A better understanding of the molecular signature of cancer has promoted the development of a new generation of anti-cancer drugs and diagnostic agents that specifically target molecular components such as genes, ligands, receptors and signaling pathways. However, intrinsic heterogeneity of tumors has hampered the overall success of target therapies even among patients with similar tumor types but unpredictable different responses to therapy. In this sense, post-treatment response monitoring becomes indispensable and nuclear medicine imaging modalities could provide the tools for an early indication of therapeutic efficacy. Herein, we briefly discuss the current role of PET and SPECT imaging in monitoring cancer therapy together with an update on the current radiolabeled probes that are currently investigated for tumor therapy response assessment.

Multimodality Imaging in Tumor Angiogenesis: Present Status and Perspectives

Angiogenesis is a complex biological process that plays a central role in progression of tumor growth and metastasis. It led to a search for antiangiogenic molecules, and to design antiangiogenic strategies for cancer treatment. Noninvasive molecular imaging, such as positron emission tomography (PET) and single photon emission computed tomography (SPECT), could be useful for lesion detection, to select patients likely to respond to antiangiogenic therapies, to confirm successful targeting, and dose optimization. Additionally, nuclear imaging techniques could also aid in the development of new angiogenesis-targeted drugs and their validation. Angiogenesis imaging can be categorized as targeted at three major cell types: (I) non-endothelial cell targets, (II) endothelial cell targets, and (III) extracellular matrix proteins and matrix proteases. Even if radiopharmaceuticals studying the metabolism and hypoxia can be also used for the study of angiogenesis, many of the agents used in nuclear imaging for this purpose are yet to be investigated. The purpose of this review is to describe the role of molecular imaging in tumor angiogenesis, highlighting the advances in this field.

Somatostatin analogues labeled with copper radioisotopes: current status

Peptide receptor radionuclide therapy (PRRT) is a promising way to treat patients with inoperable tumors or metastatic neuroendocrine tumors. This therapeutic strategy is using radiolabeled peptides, which are capable of selective biding to receptors overexpressed in the cancer cells. One of the group of receptor-avid peptide used in the PRRT are the analogues of somatostatin (SST) connected to the complexes of radionuclides (e.g. ⁹⁰Y, ¹⁷⁷Lu or ¹¹¹In). Many studies have shown that radiopharmaceuticals based on Cu radioisotopes are promising for the diagnosis and treatment of various cancers. This mini-review focuses on recent developments and summarises the results of multiple studies addressing SST agonists and antagonists radiolabeled to Cu radioisotopes.

Radiolabeled bombesin derivatives for preclinical oncological imaging

Despite efforts, cancer is still one of the leading causes of morbidity and mortality worldwide, with approximately 14 million new cases and 8.2 million cancer-related deaths each year, according to the World Health Organization. Among the strategies to reduce cancer progression and improving its management, implementing early detection technologies is crucial. Based on the fact that several types of cancer cells overexpress surface receptors, small molecule ligands, such as peptides, have been developed to allow tumor identification at earlier stages. Allied with imaging techniques such as PET and SPECT, radiolabeled peptides play a pivotal role in nuclear medicine. Bombesin, a peptide of 14 amino acids, is an amphibian homolog to the mammalian gastrin-releasing peptide (GRP), that has been extensively studied as a targeting ligand for diagnosis and therapy of GRP positive tumors, such as breast, pancreas, lungs and prostate cancers. In this context, herein we provide a review of reported bombesin derivatives radiolabeled with a multitude of radioactive isotopes for diagnostic purposes in the preclinical setting. Moreover, since animal models are highly relevant for assessing the potential of clinical translation of this radiopeptides, a brief report of the currently used GRP-positive tumor-bearing animal models is described.

Imaging of Brain Tumors with Copper-64 Chloride: Early Experience and Results

OBJECTIVES

To conduct the first investigational study that is aimed at evaluating the ability of the simple salt (64)CuCl2 to diagnose cerebral tumors in patients affected by glioblastoma multiforme (GBM).

METHODS

Nineteen patients with a documented history and radiologic evidence of brain tumors were enrolled in the study. Eighteen patients were diagnosed with GBM, and one patient was diagnosed with grade II astrocytoma. After initial cerebral magnetic resonance imaging (MRI), patients were administered with (64)CuCl2 (13 MBq/kg) and brain positron emission tomography (PET)/computed tomography (CT) imaging was performed at 1, 3, and 24 hours after administration. Standardized uptake values (SUVs) were calculated and used to figure out the pharmacokinetic profile of the tracer. Absorbed radiation doses were estimated using OLINDA/EXM.

RESULTS

Copper-64 chloride clearly visualized brain cancerous lesions within 1 hour after injection, with stable retention of radioactivity at 3 and 24 hours. Excellent agreement was found between PET/CT and MRI. No uptake of the tracer was observed in low-grade astrocytoma. The agent cleared rapidly from the blood and was mostly excreted through the liver, without significant kidney washout. Analysis of time variation of SUVmax values showed persistent uptake in malignant tissues with a slight increase of radioactive concentration at 24 hours.

CONCLUSIONS

Copper-64 chloride has favorable biological properties for brain imaging and warrants further investigation as a diagnostic tracer for GBM.

Pre-clinical Positron Emission Tomography Reconstruction Algorithm Effect on Cu-64 ATSM Lesion Hypoxia

Objective:

Application of distinct positron emission tomography (PET) scan reconstruction algorithms can lead to statistically significant differences in measuring lesion functional properties. We looked at the influence of two-dimensional filtered back projection (2D FBP), two-dimensional ordered subset expectation maximization (2D OSEM), three-dimensional ordered subset expectation maximization (3D OSEM) without 3D maximum a posteriori and with (3D OSEM MAP) on lesion hypoxia tracer uptake using a pre-clinical PET scanner.

Methods:

Reconstructed images of a rodent tumor model bearing P22 carcinosarcoma injected with hypoxia tracer Copper-64-Diacetyl-bis (N4-methylthiosemicarbazone) (i.e. Cu-64 ATSM) were analyzed at 10 minute intervals till 60 minute post injection. Lesion maximum standardized uptake values (SUV_max) and SUV_max/background SUV_mean (T/B) were recorded and investigated after application of multiple algorithm and reconstruction parameters to assess their influence on Cu-64 ATSM measurements and associated trends over time.

Results:

SUV_maxSUV_max or T/B between 2D FBP, exhibited convergence for OSEM reconstructions while ANOVA results showed a significant difference in SUV_max or T/B between 2D FBP, 2D OSEM, 3D OSEM and 3D OSEM MAP reconstructions across all time frames. SUV_max and T/B were greatest in magnitude for 2D OSEM followed by 3D OSEM MAP, 3D OSEM and then 2D FBP at all time frames respectively. Similarly SUV_max and T/B standard deviations (SD) were lowest for 2D OSEM in comparison with other algorithms.

Conclusion:

Significantly higher magnitude lesion SUV_max and T/B combined with lower SD were observed using 2D OSEM reconstruction in comparison with 2D FBP, 3D OSEM and 3D OSEM MAP algorithms at all time frames. Results are SUV_max or T/B between 2D FBP, consistent with other published studies however more specimens are required for full validation.

Molecular imaging and therapy targeting copper metabolism in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide. Significant efforts have been devoted to identify new biomarkers for molecular imaging and targeted therapy of HCC. Copper is a nutritional metal required for the function of numerous enzymatic molecules in the metabolic pathways of human cells. Emerging evidence suggests that copper plays a role in cell proliferation and angiogenesis. Increased accumulation of copper ions was detected in tissue samples of HCC and many other cancers in humans. Altered copper metabolism is a new biomarker for molecular cancer imaging with position emission tomography (PET) using radioactive copper as a tracer. It has been reported that extrahepatic mouse hepatoma or HCC xenografts can be localized with PET using copper-64 chloride as a tracer, suggesting that copper metabolism is a new biomarker for the detection of HCC metastasis in areas of low physiological copper uptake. In addition to copper modulation therapy with copper chelators, short-interference RNA specific for human copper transporter 1 (hCtr1) may be used to suppress growth of HCC by blocking increased copper uptake mediated by hCtr1. Furthermore, altered copper metabolism is a promising target for radionuclide therapy of HCC using therapeutic copper radionuclides. Copper metabolism has potential as a new theranostic biomarker for molecular imaging as well as targeted therapy of HCC.

Copper-64 Dichloride as Theranostic Agent for Glioblastoma Multiforme: A Preclinical Study

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor in adults with a median survival time less than one year. To date, there are only a limited number of effective agents available for GBM therapy and this does not seem to add much survival advantage over the conventional approach based on surgery and radiotherapy. Therefore, the development of novel therapeutic approaches to GBM is essential and those based on radionuclide therapy could be of significant clinical impact. Experimental evidence has clearly demonstrated that cancer cells have a particularly high fractional content of copper inside the nucleus compared to normal cells. This behavior can be conveniently exploited both for diagnosis and for delivering therapeutic payloads (theranostic) of the radionuclide copper-64 into the nucleus of cancerous cells by intravenous administration of its simplest chemical form as dichloride salt [⁶⁴Cu]CuCl₂. To evaluate the potential theranostic role of [⁶⁴Cu]CuCl₂ in GBM, the present work reports results from a preclinical study carried out in a xenografted GBM tumor mouse model. Biodistribution data of this new agent were collected using a small-animal PET tomograph. Subsequently, groups of tumor implanted nude mice were treated with [⁶⁴Cu]CuCl₂ to simulate single- and multiple-dose therapy protocols, and results were analyzed to estimate therapeutic efficacy.

Radiolabeling and evaluation of (64)Cu-DOTA-F56 peptide targeting vascular endothelial growth factor receptor 1 in the molecular imaging of gastric cancer

Noninvasive imaging of vascular endothelial growth factor receptor 1 (VEGFR1) remains a great challenge in early diagnosis of gastric cancer. Here we reported the synthesis, radiolabeling, and evaluation of a novel (64)Cu-radiolabeled peptide for noninvasive positron emission tomography (PET) imaging of VEGFR1 positive gastric cancer. The binding of modified peptide WHSDMEWWYLLG (termed as F56) to VEGER-1 expressed in gastric cancer cell BCG823 has been confirmed by immune-fluorescence overlap. DOTA-F56 was designed and prepared by solid-phase synthesis and folded in vitro. (64)Cu-DOTA-F56 was synthesized in high radiochemical yield and high specific activity (S.A. up to 255.6 GBq/mmol). It has excellent in vitro stability. Micro-PET imaging of (64)Cu-DOTA-F56 identifies tumor in BCG823 tumor-bearing mice, while that of (18)F-FDG does not. Immunohistochemical analysis of excised BCG823 xenograft showed colocalization between the PET images and the staining of VEGFR1. These results demonstrated that (64)Cu-DOTA-F56 peptide has potential as a noninvasive imaging agent in VEGFR1 positive tumors.

Future Perspectives of Radionanomedicine Using the Novel Micelle-Encapsulation Method for Surface Modification

The emerging radionanomedicine has multifunctional and theranostic purposes. For these purposes, radionanomedicine should achieve the efficient and specific delivery of therapeutic agents by multifunctional characteristics, using low amounts of nanomaterials in vivo. Recent research on radiolabeled micelle-encapsulated nanomaterials has been made on the their efficacy and safety using a one-step surface modification method (Jeong's method). This one-step multifunctional approach to the nanoparticle can be the important challenge in producing effective nanoplatforms for cancer imaging and therapy.