Intravenous and oral copper kinetics, biodistribution and dosimetry in healthy humans studied by [64Cu]copper PET/CT

[64Cu]Copper chloride PET-CT: a comparative evaluation of fasting and non-fasting states in patients of prostate carcinoma

Altered copper metabolism in cancer has been linked to increased intracellular copper uptake mediated by human copper transporter 1, with [64Cu]Cu2+ as a potential biomarker for cancer theranostics. [64Cu]CuCl2 PET-CT though explored in various malignancies, a lack of standardized protocol exists, particularly regarding fasting status before imaging. This analysis aimed to evaluate the requirement of fasting for [64Cu]CuCl2 PET-CT along with temporal changes in physiological organ uptake in delayed scans. A total of 26 patients of prostate carcinoma who underwent [64Cu]CuCl2 PET-CT imaging were divided into two groups: (1) nonfasting (n = 12) and (2) fasting (n = 14). The nonfasting group received an average dose of 350 MBq, while the fasting group received 300 MBq of [64Cu]CuCl2, and PET-CT images acquired approximately 60-90 min (1 h image) and 3-3.5 h (delayed image) after intravenous injection of the tracer. An experienced nuclear medicine physician evaluated the images for qualitative assessment between the groups. Multiple spherical regions of interest were placed at sites of physiological organ uptake of the tracer and over the diseased lesions to measure the mean SUVmax. No significant difference was observed in the qualitative assessment of the images between the two groups (except for a slight predilection towards more hepatic tracer retention observed in the fasting group), including in the delayed images. The liver demonstrated the highest tracer uptake in all patients, with a mean SUVmax of 21.5 in the fasting group and 19.7 in the nonfasting group, showing no significant difference (P = 0.32). The kidneys, intestines, and salivary glands also showed similar trends of tracer uptake in both groups. The study illustrated that the fasting or nonfasting status did not affect image quality or semiquantitative measurements significantly in physiological organs and diseased lesions in patients with carcinoma prostate.

64Cu2+ Complexes of Tripodal Amine Ligands' In Vivo Tumor and Liver Uptakes and Intracellular Cu Distribution in the Extrahepatic Bile Duct Carcinoma Cell Line TFK-1: A Basic Comparative Study

Copper (Cu) is a critical element for cancer cell proliferation and considerably accumulates in the nucleus. 64Cu2+ is an anticancer radiopharmaceutical that targets the copper requirement of cancer cells. However, intravenously injected 64Cu2+ ions primarily accumulate in the liver. Ligand complexation of 64Cu2+ may be a promising method for increasing tumor delivery by reducing liver uptake. In this study, we used three tripodal amine ligands [tris(2-aminoethyl)amine (Tren), diethylenetriamine (Dien), and tris(2-pyridylmethyl)amine (TPMA)] to enclose 64Cu2+ ions and compared their in vivo tumor and liver uptakes using a tumor-bearing xenograft mouse model of the extrahepatic bile duct carcinoma cell line TFK-1. We examined intracellular Cu distribution using microparticle-induced X-ray emission (micro-PIXE) analysis of these compounds. 64Cu2+-Tren and 64Cu2+-Dien showed higher tumor uptake than 64Cu2+-TPMA and 64Cu2+ ions in TFK-1 tumors. Among the three 64Cu2+ complexes and 64Cu2+ ions, liver uptake was inversely correlated with tumor uptake. Micro-PIXE analysis showed that in vitro cellular uptake was similar to in vivo tumor uptake, and nuclear delivery was the highest for 64Cu2+-Tren. Conclusively, an inverse correlation between tumor and liver uptake was observed using three 64Cu2+ complexes of tripodal amine ligands and 64Cu2+ ions. These results provide useful information for the future development of anticancer 64Cu radiopharmaceuticals.

Effects of trientine and penicillamine on intestinal copper uptake: A mechanistic 64 Cu PET/CT study in healthy humans

BACKGROUND AND AIMS

Trientine (TRI) and D-penicillamine (PEN) are used to treat copper overload in Wilson disease. Their main mode of action is thought to be through the facilitation of urinary copper excretion. In a recent study, TRI was noninferior to PEN despite lower 24-hour urinary copper excretion than PEN. We tested whether TRI and/or PEN also inhibit intestinal copper absorption.

APPROACH AND RESULTS

Sixteen healthy volunteers were examined with positron emission tomography (PET)/CT 1 and 15 hours after an oral Copper-64 ( 64 Cu) dose. They then received 7 days of either PEN or TRI (trientine tetrahydrochloride), after which the 64 Cu PET/CT scans were repeated. Venous blood samples were also collected. Pretreatment to posttreatment changes of the hepatic 64 Cu uptake reflect the effect of drugs on intestinal absorption. 64 Cu activity was normalized to dose and body weight and expressed as the mean standard uptake value. TRI (n=8) reduced hepatic 64 Cu activity 1 hour after 64 Cu dose from 6.17 (4.73) to 1.47 (2.97) standard uptake value, p <0.02, and after 15 hours from 14.24 (3.09) to 6.19 (3.43), p <0.02, indicating strong inhibition of intestinal 64 Cu absorption. PEN (n=8) slightly reduced hepatic standard uptake value at 15 hours, from 16.30 (5.63) to 12.17 (1.44), p <0.04.

CONCLUSIONS

In this mechanistic study, we show that TRI inhibits intestinal copper absorption, in addition to its cupriuretic effect. In contrast, PEN has modest effects on the intestinal copper absorption. This may explain why TRI and PEN are equally effective although urinary copper excretion is lower with TRI. The study questions whether the same therapeutic targets for 24-hour urinary excretion apply to both drugs.

Effects of tetrathiomolybdate on copper metabolism in healthy volunteers and in patients with Wilson disease

BACKGROUND & AIMS

In Wilson disease (WD), copper accumulates in the liver and brain causing disease. Bis-choline tetrathiomolybdate (TTM) is a potent copper chelator that may be associated with a lower risk of inducing paradoxical neurological worsening than conventional therapy for neurologic WD. To better understand the mode of action of TTM, we investigated its effects on copper absorption and biliary excretion.

METHODS

In a double-blind randomized setting, hepatic 64Cu activity was examined after orally administered 64Cu by PET/CT in 16 healthy volunteers before and after seven days of TTM treatment (15 mg/d) or placebo. Oral 64Cu was administered one hour after the final TTM dose. Changes in hepatic 64Cu activity reflected changes in intestinal 64Cu uptake. Additionally, in four patients with WD, the distribution of 64Cu in venous blood, liver, gallbladder, kidney, and brain was followed after i.v. 64Cu dosing for up to 68 hours before and after seven days of TTM (15 mg/day), using PET/MRI. Increased gallbladder 64Cu activity was taken as evidence of increased biliary 64Cu excretion.

RESULTS

In healthy volunteers, TTM reduced intestinal 64Cu uptake by 82% 15 hours after the oral 64Cu dose. In patients with WD, gallbladder 64Cu activity was negligible before and after TTM, while TTM effectively retained 64Cu in the blood, significantly reduced hepatic 64Cu activity at all time-points and significantly reduced cerebral 64Cu activity two hours after the intravenous 64Cu dose.

CONCLUSIONS

While we did not show an increase in biliary excretion of 64Cu following TTM administration, we demonstrated that TTM effectively inhibited most intestinal 64Cu uptake and retained 64Cu in the blood stream, limiting the exposure of organs like the liver and brain to 64Cu.

IMPACT AND IMPLICATIONS

Bis-choline tetrathiomolybdate (TTM) is an investigational copper chelator being developed for the treatment of Wilson disease. In animal models of Wilson disease, TTM has been shown to facilitate biliary copper excretion. In the present human study, TTM surprisingly did not facilitate biliary copper excretion but instead reduced intestinal copper uptake to a clinically significant degree. Our study builds on our understanding of human copper metabolism and the mechanism of action of TTM.

Normal physiological distribution and tumor localization of 64 CuCl 2 in different human malignancies along with semiquantitative scoring: a comparative evaluation with 18 Fluorodeoxyglucose ( 18 FDG) PET-CT

OBJECTIVE

This study aimed to explore 64-Copper-Chloride ( 64 CuCl 2 ) PET-CT in various malignancies and demonstrate a head-to-head comparison of uptake on 64 CuCl 2 PET/computed tomography (CT) and 18 fluorodeoxyglucose ( 18 FDG)-PET/CT scans for different malignancies, with an emphasis on 18 FDG nonavid malignancies.

METHODS

Fifty-three patients diagnosed with various biopsy-proven malignancies (except prostate cancer) were recruited in this prospective study. All the patients underwent both 64 CuCl 2 PET/CT and 18 FDG-PET/CT. 64 CuCl 2 PET/CT was acquired at 1, 3 and 24 h time points. We studied the physiological biodistribution of 64 CuCl 2 in the various organs, corroborated the uptake of 64 CuCl 2 with various types of malignancies and comparison of their uptake with 18 FDG-PET/CT and their correlation with each other in various lesions.

RESULTS

The biodistribution study showed that the liver concentrated 64 CuCl 2 the most out of all the organs, followed by the pancreas and large intestine. Liver and intestinal activity increased subsequently with delayed imaging, and the washout of 64 CuCl 2 was noted in the pancreas in delayed images and followed a hepatobiliary excretion of tracer over a period of time. In lesion-wise analysis, it was noted that the primary neuroendocrine tumor, melanoma and renal/urothelial malignancy group showed more uptake of 64 CuCl 2 , than that in metastasis and vice-versa was noted in lung and soft tissue malignancies. Comparing it with 18 FDG, it was seen that FDG showed more uptake in lesions and showed no significant correlation (Kappa value: 0.089) with the uptake of 64 CuCl 2 in the lesion-wise comparison.

CONCLUSION

64 CuCl 2 PET/CT did not show any added advantage over 18 FDG-PET/CT in the evaluation of the studied malignancies, both primary and their metastasis. Biodistribution studies showed the liver as the organ with maximum uptake, which implies it may hinder the detection of abdominal or hepatic involvement of the disease.

Mesenchymal Stem Cell-Derived Exosomes in Various Chronic Liver Diseases: Hype or Hope?

Chronic liver conditions are associated with high mortality rates and have a large adverse effect on human well-being as well as a significant financial burden. Currently, the only effective treatment available for the effects of liver failure and cirrhosis resulting from the progression of several chronic liver diseases is liver transplantation carried out at the original location. This implies that developing novel and effective treatments is imperative. Regenerative medicine has long been associated with stem cell therapy. Mesenchymal stem cells (MSCs), a type of cell with great differentiation potential, have become the preferred source for stem cell therapy. According to recent studies, MSCs' paracrine products-rather than their capacity for differentiation-play a significant therapeutic effect. MSC exosomes, a type of extracellular vesicle (MSC-EV), came into view as the paracrine substances of MSCs. According to research, MSC exosomes can maintain tissue homeostasis, which is necessary for healthy tissue function. All tissues contain them, and they take part in a variety of biological activities that support cellular activity and tissue regeneration in order to preserve tissue homeostasis. The outcomes support the use of MSCs and the exosomes they produce as a therapeutic option for a range of diseases. This review provides a brief overview of the source of MSC-EVs and outlines their physiological roles and biochemical capabilities. The elucidation of the role of MSC-EVs in the recovery and repair of hepatic tissues, as well as their contribution to maintaining tissue homeostasis, is discussed in relation to different chronic liver diseases. This review aims to provide new insights into the unique roles that MSC-EVs play in the treatment of chronic liver diseases.

Copper release by MOF-74(Cu): a novel pharmacological alternative to diseases with deficiency of a vital oligoelement

Copper deficiency can trigger various diseases such as Amyotrophic Lateral Sclerosis (ALS), Parkinson's disease (PD) and even compromise the development of living beings, as manifested in Menkes disease (MS). Thus, the regulated administration (controlled release) of copper represents an alternative to reduce neuronal deterioration and prevent disease progression. Therefore, we present, to the best of our knowledge, the first experimental in vitro investigation for the kinetics of copper release from MOF-74(Cu) and its distribution in vivo after oral administration in male Wistar rats. Taking advantage of the abundance and high periodicity of copper within the crystalline-nanostructured metal-organic framework material (MOF-74(Cu)), it was possible to control the release of copper due to the partial degradation of the material. Thus, we simultaneously corroborated a low accumulation of copper in the liver (the main detoxification organ) and a slight increase of copper in the brain (striatum and midbrain), demonstrating that MOF-74(Cu) is a promising pharmacological alternative (controlled copper source) to these diseases.

Exploratory analysis of 64 CuCl 2 PET-CT imaging in carcinoma prostate and its comparison with 68 Ga-PSMA-11 and 18 F-FDG PET-CT

AIM

Exploratory analysis of 64 CuCl 2 PET-CT imaging in patients of carcinoma prostate and its head-to-head comparison with 68 Ga-PSMA-11 and 18 F-FDG PET-CT.

METHODS

In this prospective study, 50 patients of biopsy-proven carcinoma prostate belonging to the entire spectrum of disease were evaluated, out of which 21 patients were for initial staging and 29 were for restaging/response evaluation. Both 64 CuCl 2 (early and delayed) and 68 Ga-PSMA-11 PET-CT were undertaken in all patients and 18 F-FDG PET-CT was done in patients whenever possible. All scans were done within a period of 2 weeks, without any interim therapeutic intervention. 64 CuCl 2 PET-CT was acquired at 1 and 3 h. We evaluated the physiological uptake of 64 CuCl 2 , correlated the uptake in primary with disease parameters like Gleason score and serum PSA levels, and compared the detection rates for primary and metastatic disease with 68 Ga-PSMA-11 and 18 F-FDG PET-CT.

RESULTS

The detection rates of primary disease were same for both 64 CuCl 2 and 68 Ga-PSMA-11 PET-CT and both agents performed similarly in detecting extra-prostatic disease. There was no statistically significant correlation observed between the uptake of 64 CuCl 2 in the primary lesion with disease parameters. With regard to the evaluation of metastatic disease, the detection rate of 64 CuCl 2 PET-CT was 86% for lymph nodes, 77.3% for skeletal metastases and 80.6% for soft tissue metastases while 68 Ga-PSMA-11 PET-CT performed better with detection rates were 98%, 99% and 85.4%, respectively. In 17 patients where 18 F-FDG PET-CT was available, 64 CuCl 2 PET-CT detected more metastatic disease than 18 F-FDG PET-CT.

CONCLUSION

64 CuCl 2 PET-CT did not show any additional advantage over 68 Ga-PSMA-11 PET-CT in evaluation of local disease or for the assessment of metastatic disease. When compared to 68 Ga-PSMA-11 PET-CT, the absence of urinary bladder and ureteric activity allows better contrast for evaluating local disease, but it does not translate into increased disease detection.

Wilson's disease: best practice

Wilson's disease is an autosomal recessive disorder arising from pathogenic variants in the Atp7b gene on chromosome 13. The defective translated ATPase copper (Cu) transport protein produced leads to Cu accumulation, initially affecting the liver but eventually affecting other cells. It is just over 20 years since the last Best Practice on this topic in this journal. This review is an update on this, covering new disease biomarkers, pathogenesis, assumptions around clinical features and developments in therapy.

Synthesis and In Vitro Comparison of DOTA, NODAGA and 15-5 Macrocycles as Chelators for the 64Cu-Labelling of Immunoconjugates

The development of ⁶⁴Cu-based immuno-PET radiotracers requires the use of copper-specific bifunctional chelators (BFCs) that contain functional groups allowing both convenient bioconjugation and stable copper complexes to limit in vivo bioreduction, transmetallation and/or transchelation. The excellent in vivo kinetic inertness of the pentaazamacrocyclic [⁶⁴Cu]Cu-15-5 complex prompted us to investigate its potential for the ⁶⁴Cu-labelling of monoclonal antibodies (mAbs), compared with the well-known NODAGA and DOTA chelators. To this end, three NODAGA, DOTA and 15-5-derived BFCs, containing a pendant azadibenzocyclooctyne moiety, were synthesised and a robust methodology was determined to form covalent bonds between them and azide-functionalised trastuzumab, an anti-HER2 mAb, using strain-promoted azide-alkyne cycloaddition. Unlike the DOTA derivative, the NODAGA- and 15-5-mAb conjugates were radiolabelled with ⁶⁴Cu, obtaining excellent radiochemical yields, under mild conditions. Although all the radioimmunoconjugates showed excellent stability in PBS or mouse serum, [⁶⁴Cu]Cu-15-5- and [⁶⁴Cu]Cu-NODAGA-trastuzumab presented higher resistance to transchelation when challenged by EDTA. Finally, the immunoreactive fraction of the radioimmunoconjugates (88-94%) was determined in HER-2 positive BT474 human breast cancer cells, confirming that the bioconjugation and radiolabelling processes implemented had no significant impact on antigen recognition.

PET Imaging of the Neurotensin Targeting Peptide NOTA-NT-20.3 Using Cobalt-55, Copper-64 and Gallium-68

Introduction: Neurotensin receptor 1 (NTSR1) is an emerging target for imaging and therapy of many types of cancer. Nuclear imaging of NTSR1 allows for noninvasive assessment of the receptor levels of NTSR1 on the primary tumor, as well as potential metastases. This work focuses on a the neurotensin peptide analogue NT-20.3 conjugated to the chelator NOTA for radiolabeling for use in noninvasive positron emission tomography (PET). NOTA-NT-20.3 was radiolabeled with gallium-68, copper-64, and cobalt-55 to determine the effect that modification of the radiometal has on imaging and potential therapeutic properties of NOTA-NT-20.3. Methods: In vitro assays investigating cell uptake and subcellular localization of the radiolabeled peptides were performed using human colorectal adenocarcinoma HT29 cells. In vivo PET/CT imaging was used to determine the distribution and clearance of the peptide in mice bearing NTSR1 expressing HT29 tumors. Results: Cell uptake studies showed that the highest uptake was obtained with [55Co] Co-NOTA-NT-20.3 (18.70 ± 1.30%ID/mg), followed by [64Cu] Cu-NOTA-NT-20.3 (15.46 ± 0.91%ID/mg), and lastly [68Ga] Ga-NOTA-NT-20.3 (10.94 ± 0.46%ID/mg) (p < 0.001). Subcellular distribution was similar across the three constructs, with the membranous fraction containing the highest amount of radioactivity. In vivo PET/CT imaging of the three constructs revealed similar distribution and tumor uptake at the 1 h imaging timepoint. Tumor uptake was receptor-specific and blockable by co-injection of non-radiolabeled NOTA-NT-20.3. SUV ratios of tumor to heart at the 24 h imaging timepoint show that [55Co] Co-NOTA-NT-20.3 (20.28 ± 3.04) outperformed [64Cu] Cu-NOTA-NT-20.3 (6.52 ± 1.97). In conclusion, our studies show that enhanced cell uptake and increasing tumor to blood ratios over time displayed the superiority of [55Co] Co-NOTA-NT-20.3 over [68Ga] Ga-NOTA-NT-20.3 and [64Cu] Cu-NOTA-NT-20.3 for the targeting of NTSR1.

High value of 64Cu as a tool to evaluate the restoration of physiological copper excretion after gene therapy in Wilson's disease

Wilson’s disease (WD) is an inherited disorder of copper metabolism associated with mutations in ATP7B gene. We have shown that the administration of an adeno-associated vector (AAV) encoding a mini version of human ATP7B (VTX-801) provides long-term correction of copper metabolism in a murine WD model. In preparation of a future clinical trial, we have evaluated by positron emission tomography (PET) the value of ⁶⁴Cu biodistribution, excretion pattern, and blood kinetics as pharmacodynamic biomarkers of VTX-801 effects. Six-week-old WD mice were injected intravenously with increasing doses of VTX-801 and 3 weeks or 3 months later with [⁶⁴Cu]CuCl₂. Untreated WD and wild-type (WT) mice were included as controls. Control WD mice showed increased hepatic ⁶⁴Cu retention, reduced fecal excretion of the radiotracer, and altered ⁶⁴Cu blood kinetics (BK) compared with WT mice. VTX-801 treatment in WD mice resulted in a significant reduction of hepatic ⁶⁴Cu accumulation, the restoration of fecal ⁶⁴Cu excretion, and the correction of ⁶⁴Cu BK. This study showed that VTX-801 restores physiological copper metabolism in WD mice, confirming the mechanism of action of VTX-801, and demonstrated the translational potential of [⁶⁴Cu]CuCl₂-PET to explore VTX-801 pharmacodynamics in a minimally invasive and sensitive manner in WD patients.

Effect of oral zinc regimens on human hepatic copper content: a randomized intervention study

Zinc inhibits intestinal copper uptake, an effect utilized for treating Wilson’s disease (WD). We used copper-64 (⁶⁴Cu) PET/CT to examine how much four weeks of treatment with different zinc regimens reduced the hepatic ⁶⁴Cu content after oral ⁶⁴Cu administration and test if alternative regimens were noninferior to the standard regimen of zinc acetate 50 mg × 3 daily. Forty healthy persons were randomized to four different zinc protocols. The WD standard treatment zinc acetate 50 mg × 3 reduced the hepatic ⁶⁴Cu content from 26.9 ± 7.5% to 13.3 ± 5.6% of the administered ⁶⁴Cu. Zinc gluconate 50 mg × 3 was noninferior (P = 0.02) (35.8 ± 9.0% to 17.4 ± 7.5%). Zinc acetate 150 mg × 1 (33.1 ± 9.9% to 17.4 ± 7.5%) and zinc gluconate 150 mg × 1 (28.1 ± 6.7% to 22.0 ± 6.7%) were less effective. These effects were intra- and inter-individually highly variable, and 14% had no effect of any zinc regimen, which may explain disparities in zinc treatment efficacy in WD patients.

64CuCl2 PET Imaging of 4T1-Related Allograft of Triple-Negative Breast Cancer in Mice

64CuCl2 is an economic radiotracer for oncologic PET investigations. In the present study, we characterized the uptake of 64CuCl2 in vivo by µPET/CT in an allograft 4T1-related mouse model (BALB/c) of advanced breast cancer. 18F-FDG was used as a comparator. Twenty-two animals were imaged 7-9 days following 4T1-cell implantation inside mammary glands. Dynamic 64CuCl2 µPET/CT acquisition or iterative static images up to 8 h p.i. were performed. Animal biodistribution and tumor uptake were first evaluated in vivo by µPET analysis and then assessed on tissue specimens. Concerning 18F-FDG µPET, a static acquisition was performed at 15 min and 60 min p.i. Tumor 64CuCl2 accumulation increased from 5 min to 4 h p.i., reaching a maximum value of 5.0 ± 0.20 %ID/g. Liver, brain, and muscle 64CuCl2 accumulation was stable over time. The tumor-to-muscle ratio remained stable from 1 to 8 h p.i., ranging from 3.0 to 3.7. Ex vivo data were consistent with in vivo estimations. The 18F-FDG tumor accumulation was 8.82 ± 1.03 %ID/g, and the tumor-to-muscle ratio was 4.54 ± 1.11. 64CuCl2 PET/CT provides good characterization of the 4T1-related breast cancer model and allows for exploration of non-glycolytic cellular pathways potentially of interest for theragnostic strategies.

The pathophysiology of Wilson's disease visualized: A human 64 Cu PET study

BACKGROUND AND AIMS

Wilson's disease (WD) is a genetic disease with systemic accumulation of copper that leads to symptoms from the liver and brain. However, the underlying defects in copper transport kinetics are only partly understood. We sought to quantify hepatic copper turnover in patients with WD compared with heterozygote and control subjects using PET with copper-64 (64 Cu) as a tracer. Furthermore, we assessed the diagnostic potential of the method.

APPROACH AND RESULTS

Nine patients with WD, 5 healthy heterozygote subjects, and 8 healthy controls were injected with an i.v. bolus of 64 Cu followed by a 90-min dynamic PET scan of the liver and static whole-body PET/CT scans after 1.5, 6, and 20 h. Blood 64 Cu concentrations were measured in parallel. Hepatic copper retention and redistribution were evaluated by standardized uptake values (SUVs). At 90 min, hepatic SUVs were similar in the three groups. In contrast, at 20 h postinjection, the SUV in WD patients (mean ± SEM, 31 ± 4) was higher than in heterozygotes (24 ± 3) and controls (21 ± 4; p < 0.001). An SUV-ratio of hepatic 64 Cu concentration at 20 and 1.5 h completely discriminated between WD patients and control groups (p < 0.0001; ANOVA). By Patlak analysis of the initial 90 min of the PET scan, the steady-state hepatic clearance of 64 Cu was estimated to be slightly lower in patients with WD than in controls (p = 0.04).

CONCLUSIONS

64 Cu PET imaging enables visualization and quantification of the hepatic copper retention characteristic for WD patients. This method represents a valuable tool for future studies of WD pathophysiology, and may assist the development of therapies, and accurate diagnosis.

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.

Non-invasive radionuclide imaging of trace metal trafficking in health and disease: "PET metallomics"

Several specific metallic elements must be present in the human body to maintain health and function. Maintaining the correct quantity (from trace to bulk) and location at the cell and tissue level is essential. The study of the biological role of metals has become known as metallomics. While quantities of metals in cells and tissues can be readily measured in biopsy and autopsy samples by destructive analytical techniques, their trafficking and its role in health and disease are poorly understood. Molecular imaging with radionuclides - positron emission tomography (PET) and single photon emission computed tomography (SPECT) - is emerging as a means to non-invasively study the acute trafficking of essential metals between organs, non-invasively and in real time, in health and disease. PET scanners are increasingly widely available in hospitals, and methods for producing radionuclides of some of the key essential metals are developing fast. This review summarises recent developments in radionuclide imaging technology that permit such investigations, describes the radiological and physicochemical properties of key radioisotopes of essential trace metals and useful analogues, and introduces current and potential future applications in preclinical and clinical investigations to study the biology of essential trace metals in health and disease.

Recent Advances in Cancer Imaging with 64CuCl2 PET/CT

Copper is required for cancer cell proliferation and tumor angiogenesis. Radioactive copper-64 chloride (⁶⁴CuCl₂) is a useful radiotracer for cancer imaging with position emission tomography (PET) based on increased cellular uptake of copper mediated by human copper transporter 1 (hCtr1) expressed on cancer cell membrane. Significant progress has been made in research of using ⁶⁴CuCl₂ as a radiotracer for cancer imaging with PET. Radiation dosimetry study in humans demonstrated radiation safety of ⁶⁴CuCl₂. Recently, ⁶⁴CuCl₂ was successfully used for PET imaging of prostate cancer, bladder cancer, glioblastoma multiforme (GBM), and non-small cell lung carcinoma in humans. Based on the findings from the preclinical research studies, ⁶⁴CuCl₂ PET/CT also holds potential for diagnostic imaging of human hepatocellular carcinoma (HCC), malignant melanoma, and detection of intracranial metastasis of copper-avid tumors based on low physiological background of radioactive copper uptake in the brain. Copper-64 radionuclide emits both β⁺ and β^- particles, suggesting therapeutic potential of ⁶⁴CuCl₂ for radionuclide cancer therapy of copper-avid tumors. Recent progress in production of therapeutic copper-67 radionuclide invites clinical research in use of theranostic pair of ⁶⁴CuCl₂ and ⁶⁷CuCl₂ for cancer imaging and radionuclide therapy.

Advancement in production of radiotracers

After introduction of the first commercial combined PET and/or CT technology in 2001, this diagnostic tool quickly became a clinical success and was considered the fastest growing diagnostic imaging technology ever. However, this technique is very dependent on the availability of positron emitting isotopes and radiochemistry to incorporate the radioactive isotopes into larger molecules of physiological interest. Within this review article a historical overview starting with the first applications of positron emitting isotopes in the 1930's is presented. Afterwards a more detailed presentation summarizing the physical basis and advancements in cyclotron technology is given. Radiochemical and/or pharmaceutical advancements are presented systematically for the most significant isotopes like ¹⁵O, ¹³N, ¹¹C, ¹⁸F and ⁶⁸Ga Besides these major PET isotopes, advancements of other radio-metals and future perspectives regarding application of new radionuclides will be discussed. Finally, very interesting new and compact accelerator technology and microfluidic chemical reaction approaches will be discussed. Especially, new compact accelerator technology might be new quantum leap within this radiodiagnostic technology and might result in even further prevalence, ultimately envisioned by the dose-on-demand concept that will be briefly discussed.

Highlight selection of radiochemistry and radiopharmacy developments by editorial board (January-June 2020)

BACKGROUND

The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biyearly highlight commentary to describe trends in the field.

RESULTS

This commentary of highlights has resulted in 19 different topics selected by each member of the Editorial Board addressing a variety of aspects ranging from novel radiochemistry to first in man application of novel radiopharmaceuticals.

CONCLUSION

Trends in radiochemistry and radiopharmacy are highlighted demonstrating the progress in the research field being the scope of EJNMMI Radiopharmacy and Chemistry.

The emerging value of 64Cu for molecular imaging and therapy

Along with other novel metallic radionuclides, copper-64 (⁶⁴Cu) is currently being investigated as an alternative option to the gallium-68 (⁶⁸Ga) and lutetium-177 (¹⁷⁷Lu) radiopharmaceuticals widely used for targeting somatostatin receptors, expressed by neuroendocrine tumors (NETs), and recently prostate specific membrane antigen (PSMA), expressed by prostate cancer cells. This interest is mostly driven by the peculiar nuclear properties of ⁶⁴Cu that make it an almost ideal example of theranostic radionuclide. In fact, ⁶⁴Cu emits both low-energy positrons, β^- particles and a swarm of Auger electrons. This combination of different emissions may allow to collect high-resolution PET images, but also to use the same radiopharmaceutical for eliciting a therapeutic effect. Another unique behavior of ⁶⁴Cu originates from the fundamental biological role played in organisms by the ionic forms of the copper element, which is naturally involved in a multitude of cellular processes including cell replication. These intrinsic biological characteristics has led to the discovery that ⁶⁴Cu, under its simplest dicationic form Cu²⁺, is able to specifically target a variety of cancerous cells and to detect the onset of a metastatic process in its initial stage. This short review reports an outline of the status of ⁶⁴Cu radiopharmaceuticals and of the most relevant results that are constantly disclosed by preclinical and investigational clinical studies.