• Hypoxia
• Oxygen enhancement ratio
• Resistance
• Targeted radionuclide therapy
• Tumor microenvironment
• α-Emission

• Humans
• Neoplasms/radiotherapy
• Neoplasms/pathology
• Tumor Hypoxia/radiation effects
• Animals
• Molecular Targeted Therapy/methods
• Radioisotopes/therapeutic use

• multimodality imaging
• iron oxide nanoparticles
• nanoceramics
• applied biomaterials
• theranostics
• targeted delivery
• radio-nanomedicines
• pet
• spect
• optical imaging

• H2020 European Research Council
• Innovate UK
• Fundación General CSIC
• University of Bath
• Science and Technology Facilities Council
• Biotechnology and Biological Sciences Research Council
• Engineering and Physical Sciences Research Council

• Cell transformation
• Copper
• Pathogenic mechanisms
• Targeted therapy

• cancer
• gamma counter
• imaging
• in vitro test
• radiopharmaceuticals radiobiology
• radiotheranostics

• CN00000033, CUP B73C21001300006 National Center 5 "National Biodiversity Future Center", theme "Bio-diversità", in the frame-work of the Piano Nazionale di Ripresa e Resilienza, Mission 4 Component 2 Investment 1.4, funded by the European Union-NextGenerationEU, identification code CN00

• OE-MRI
• [18F]-FAZA
• [18F]-FMISO
• [64Cu]-ATSM
• cancer
• hypoxia

• RBE
• dose rate
• dosimetry
• heterogeneity
• preclinical
• proliferation
• targeted radionuclide therapy
• tumor control probability

Targeted radionuclide theranostics is becoming more and more prominent in clinical oncology. Currently, most nuclear medicine compounds researched for cancer theranostics are directed towards targets expressed in only a small subset of cancer types, limiting clinical applicability. The identification of cancer-specific targets that are (more) universally expressed will allow more cancer patients to benefit from these personalized nuclear medicine–based interventions. A tumor is not merely a collection of cancer cells, it also comprises supporting stromal cells embedded in an altered extracellular matrix (ECM), together forming the tumor microenvironment (TME). Since the TME is less genetically unstable than cancer cells, and TME phenotypes can be shared between cancer types, it offers targets that are more universally expressed. The TME is characterized by the presence of altered processes such as hypoxia, acidity, and increased metabolism. Next to the ECM, the TME consists of cancer-associated fibroblasts (CAFs), macrophages, endothelial cells forming the neo-vasculature, immune cells, and cancer-associated adipocytes (CAAs). Radioligands directed at the altered processes, the ECM, and the cellular components of the TME have been developed and evaluated in preclinical and clinical studies for targeted radionuclide imaging and/or therapy. In this review, we provide an overview of the TME targets and their corresponding radioligands. In addition, we discuss what developments are needed to further explore the TME as a target for radionuclide theranostics, with the hopes of stimulating the development of novel TME radioligands with multi-cancer, or in some cases even pan-cancer, application.

• Cancer stroma
• Pan-cancer therapy
• Radionuclide imaging and therapy
• Theranostics
• Tumor microenvironment

• copper-64
• purification
• quality control
• solid targetry

• Cyclotrons
• Copper Radioisotopes/chemistry
• Radiochemistry/instrumentation
• Radiochemistry/methods
• Quality Control
• Hospitals
• Positron-Emission Tomography/instrumentation

• 16463 Cancer Research UK

Tumor hypoxia (low tissue oxygenation) is an adverse condition of the solid tumor environment, associated with malignant progression, radiotherapy resistance, and poor prognosis. One method to detect tumor hypoxia is by positron emission tomography (PET) with the tracer [⁶⁴Cu][Cu-diacetyl-bis(N(4)-methylthiosemicarbazone)] ([⁶⁴Cu][Cu(ATSM)]), as demonstrated in both preclinical and clinical studies. In addition, emerging studies suggest using [⁶⁴Cu][Cu(ATSM)] for molecular radiotherapy, mainly due to the release of therapeutic Auger electrons from copper-64, making [⁶⁴Cu][Cu(ATSM)] a “theranostic” agent. However, the radiocopper retention based on a metal-ligand dissociation mechanism under hypoxia has long been controversial. Recent studies using ionic Cu(II) salts as tracers have raised further questions on the original mechanism and proposed a potential role of copper itself in the tracer uptake. We have reviewed the evidence of using the copper radiopharmaceuticals [^60/61/62/64Cu][Cu(ATSM)]/ionic copper salts for PET imaging of tumor hypoxia, their possible therapeutic applications, issues related to the metal-ligand dissociation mechanism, and possible explanations of copper trapping based on studies of the copper metabolism under hypoxia.

We found that hypoxia selectivity of [⁶⁴Cu][Cu(ATSM)] has been clearly demonstrated in both preclinical and clinical studies. Preclinical therapeutic studies in mice have also demonstrated promising results, recently reporting significant tumor volume reductions and improved survival in a dose-dependent manner. Cu(II)-[Cu(ATSM)] appears to be accumulated in regions with substantially higher CD133⁺ expression, a marker for cancer stem cells. This, combined with the reported requirement of copper for activation of the hypoxia inducible factor 1 (HIF-1), provides a possible explanation for the therapeutic effects of [⁶⁴Cu][Cu(ATSM)]. Comparisons between [⁶⁴Cu][Cu(ATSM)] and ionic Cu(II) salts have showed similar results in both imaging and therapeutic studies, supporting the argument for the central role of copper itself in the retention mechanism.

We found promising evidence of using copper-64 radiopharmaceuticals for both PET imaging and treatment of hypoxic tumors. The Cu(II)-[Cu(ATSM)] retention mechanism remains controversial and future mechanistic studies should be focused on understanding the role of copper itself in the hypoxic tumor metabolism.

• Copper-64
• Metabolism
• Positron emission tomography
• Radiation
• Tumor hypoxia

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.

• auger therapy
• copper-64 chloride
• prostate cancer
• radiobiology
• theranostics

This review describes artificial modular nanotransporters (MNTs) delivering their cargos into target cells and then into the nuclei – the most vulnerable cell compartment for most anticancer agents and especially for radionuclides emitting short-range particles. The MNT strategy uses natural subcellular transport processes inherent in practically all cells including cancer cells. The MNTs use these processes just as a passenger who purchased tickets for a multiple-transfer trip making use of different kinds of public transport to reach the desired destination. The MNTs are fusion polypeptides consisting of several parts, replaceable modules, accomplishing binding to a specific receptor on the cell and subsequent internalization, endosomal escape and transport into the cell nucleus. Radionuclides emitting short-range particles, like Auger electron emitters, acquire cell specificity and significantly higher cytotoxicity both in vitro and in vivo when delivered by the MNTs into the nuclei of cancer cells. MNT modules are interchangeable, allowing replacement of receptor recognition modules, which permits their use for different types of cancer cells and, as a cocktail of several MNTs, for targeting several tumor-specific molecules for personalized medicine.

• Auger electron emitters
• cancer
• cell nucleus
• modular nanotransporters
• nuclear medicine
• subcellular drug delivery

• Aged
• Carcinoma, Non-Small-Cell Lung/diagnostic imaging
• Coordination Complexes
• Copper Radioisotopes
• Female
• Fractals
• Head and Neck Neoplasms/diagnostic imaging
• Humans
• Image Interpretation, Computer-Assisted/methods
• Lung Neoplasms/diagnostic imaging
• Male
• Middle Aged
• Organometallic Compounds
• Pilot Projects
• Positron Emission Tomography Computed Tomography/methods
• Positron Emission Tomography Computed Tomography/statistics & numerical data
• Radiopharmaceuticals
• Thiosemicarbazones

• cancer
• hypoxia
• imaging agents
• metal complexes

• 2-Nitroimidazole
• Carbonic anhydrase 9
• Copper-64
• Hypoxia imaging
• Positron emission tomography

• contrast agents
• copper
• gallium
• positron emission tomography
• radiopharmaceuticals
• technetium
• zirconium

• A16463 Cancer Research UK
• 084052 Wellcome Trust
• 088641 Wellcome Trust
• Wellcome Trust
• MC_PC_14105 Medical Research Council

In lung cancer, tumor hypoxia is a characteristic feature, which is associated with a poor prognosis and resistance to both radiation therapy and chemotherapy. As the development of tumor hypoxia is associated with decreased perfusion, perfusion measurements provide more insight into the relation between hypoxia and perfusion in malignant tumors. Positron emission tomography (PET) is a highly sensitive nuclear imaging technique that is suited for non-invasive in vivo monitoring of dynamic processes including hypoxia and its associated parameter perfusion. The PET technique enables quantitative assessment of hypoxia and perfusion in tumors. To this end, consecutive PET scans can be performed in one scan session. Using different hypoxia tracers, PET imaging may provide insight into the prognostic significance of hypoxia and perfusion in lung cancer. In addition, PET studies may play an important role in various stages of personalized medicine, as these may help to select patients for specific treatments including radiation therapy, hypoxia modifying therapies, and antiangiogenic strategies. In addition, specific PET tracers can be applied for monitoring therapy. The present review provides an overview of the clinical applications of PET to measure hypoxia and perfusion in lung cancer. Available PET tracers and their characteristics as well as the applications of combined hypoxia and perfusion PET imaging are discussed.

• Molecular imaging
• Positron emission tomography
• Hypoxia
• Perfusion
• Quantification
• Lung cancer

Hypoxia is a central problem in tumor treatment because hypoxic cells are less sensitive to chemo- and radiotherapy than normoxic cells. Radioresistance of hypoxic tumor cells is due to reduced sensitivity towards low Linear Energy Transfer (LET) radiation. High LET α-emitters are thought to eradicate tumor cells independent of cellular oxygenation. Therefore, the aim of this study was to demonstrate that cell-bound α-particle emitting ²¹³Bi immunoconjugates kill hypoxic and normoxic CAL33 tumor cells with identical efficiency. For that purpose CAL33 cells were incubated with ²¹³Bi-anti-EGFR-MAb or irradiated with photons with a nominal energy of 6 MeV both under hypoxic and normoxic conditions. Oxygenation of cells was checked via the hypoxia-associated marker HIF-1α. Survival of cells was analysed using the clonogenic assay. Cell viability was monitored with the WST colorimetric assay. Results were evaluated statistically using a t-test and a Generalized Linear Mixed Model (GLMM). Survival and viability of CAL33 cells decreased both after incubation with increasing ²¹³Bi-anti-EGFR-MAb activity concentrations (9.25 kBq/ml–1.48 MBq/ml) and irradiation with increasing doses of photons (0.5–12 Gy). Following photon irradiation survival and viability of normoxic cells were significantly lower than those of hypoxic cells at all doses analysed. In contrast, cell death induced by ²¹³Bi-anti-EGFR-MAb turned out to be independent of cellular oxygenation. These results demonstrate that α-particle emitting ²¹³Bi-immunoconjugates eradicate hypoxic tumor cells as effective as normoxic cells. Therefore, ²¹³Bi-radioimmunotherapy seems to be an appropriate strategy for treatment of hypoxic tumors.

• Alpha Particles/therapeutic use
• Antibodies, Monoclonal, Humanized/pharmacology
• Antibodies, Monoclonal, Humanized/therapeutic use
• Bismuth/therapeutic use
• Blotting, Western
• Cell Hypoxia/drug effects
• Cell Hypoxia/radiation effects
• Cell Line, Tumor
• Cell Survival/drug effects
• Cell Survival/radiation effects
• ErbB Receptors/immunology
• Humans
• Hypoxia-Inducible Factor 1, alpha Subunit/metabolism
• Immunoconjugates/therapeutic use
• Neoplasms/drug therapy
• Neoplasms/immunology
• Neoplasms/pathology
• Neoplasms/radiotherapy
• Oxygen/pharmacology
• Particle Accelerators
• Photons
• Radioisotopes/therapeutic use

Human and feline head and neck squamous cell carcinoma (HNSCC) share histology, certain molecular features, as well as locally aggressive and highly recurrent clinical behavior. In human HNSCC, the presence of significant hypoxia within these tumors is considered an important factor in the development of a more aggressive phenotype and poor response to therapy. We hypothesized that feline head and neck tumors, particularly HNSCC, would exhibit hypoxia and that ⁶⁴Cu-diacetyl-bis(N4-methylthiosemicarbazone) (Cu-ATSM) positron emission tomography/computed tomography (PET/CT) would permit detection of intratumoral hypoxia.

12 cats with measureable head and neck tumors were given ⁶⁴Cu-ATSM and iodinated contrast for PET/CT scan. The presence or absence of hypoxia was also assessed using an intratumoral fluorescent life-time probe to quantitate pO₂ and pimonidazole immunohistochemical staining in biopsy specimens. In two cats, intratumoral O₂ and ⁶⁴Cu-ATSM uptake was measured before and after treatment with anti-angiogenic agents to determine the effect of these agents on hypoxia.

Eleven of twelve feline tumors demonstrated significant ⁶⁴Cu-ATSM uptake, regardless of malignant or benign etiology. The presence (and absence) of hypoxia was confirmed using the fluorescent O₂ detection probe in nine tumors, and using pimonidazole staining in three tumors. Squamous cell carcinomas (HNSCC) demonstrated the highest degree of hypoxia, with T_max/M ratios ranging from 4.3 to 21.8. Additional non-neoplastic tissues exhibited ⁶⁴Cu-ATSM uptake suggestive of hypoxia including reactive draining lymph nodes, non-malignant thyroid pathology, a tooth root abscess, and otitis media. In two cats with HNSCC that received anti-vascular agents, the pattern of ⁶⁴Cu-ATSM uptake was altered after treatment, demonstrating the potential of the feline model to study the modulation of tumor oxygenation.

Feline HNSCC serves as a clinically relevant model for the investigation of intratumoral hypoxia including its measurement, modulation and targeting.

• Adult
• Aged
• Biomarkers, Tumor/metabolism
• Brain Neoplasms/diagnostic imaging
• Brain Neoplasms/metabolism
• Coordination Complexes
• Copper Radioisotopes/pharmacokinetics
• Female
• Glioma/diagnostic imaging
• Glioma/metabolism
• Humans
• Hypoxia-Inducible Factor 1, alpha Subunit/metabolism
• Male
• Middle Aged
• Organometallic Compounds/pharmacokinetics
• Positron-Emission Tomography/methods
• Radiopharmaceuticals/pharmacokinetics
• Reproducibility of Results
• Sensitivity and Specificity
• Thiosemicarbazones/pharmacokinetics
• Young Adult

• bifunctional chelator
• copper
• molecular imaging
• positron emission tomography
• radionuclide
• radiopharmaceutical

• Copper Radioisotopes/chemistry
• Copper Radioisotopes/pharmacokinetics
• Copper Radioisotopes/therapeutic use
• Humans
• Molecular Imaging
• Positron-Emission Tomography
• Radiopharmaceuticals/chemistry
• Radiopharmaceuticals/pharmacokinetics
• Radiopharmaceuticals/therapeutic use

• F32 CA115148 NCI NIH HHS