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2-Methoxyestradiol (2ME) is involved in the pathogenesis of preeclampsia and antitumor activity. In addition to its low concentration in healthy human serum, presence of isomers makes quantification of 2ME for clinical research and laboratory medicine difficult. The objective of this study was to develop a highly sensitive and accurate method for quantifying 2ME using LC-MS/MS combined with derivatization with 1-(2,4-dinitro-5-fluorophenyl)-4,4-dimethylpiperazinium iodide (MPDNP-F). This approach significantly enhanced the detectability of 2ME in positive electrospray ionization-tandem mass spectrometry (ESI-MS/MS) and enabled the chromatographic separation of 2ME from isomeric metabolites possessing a methoxy group, including 4-methoxyestradiol, 3-O-methyl 2-hydroxyestradiol, and 3-O-methyl 4-hydroxyestradiol (3M4OH). Although the derivatized 2ME and 3M4OH were closely eluted under the optimized LC conditions, the different fragmentation patterns of these isomers during MS/MS allowed their distinction. The lower limit of quantification for 2ME was 2.5 pg/mL, indicating a satisfactory sensitivity. These findings demonstrated that this LC-MS/MS method combined with the MPDNP-F derivatization can provide accurate and highly sensitive quantification of 2ME.

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.

Abstract Background Osteoblastic skeletal metastasis is frequently observed in prostate cancer. An effective therapy has not been developed due to the unclear molecular mechanism. The Wnt family is involved in various biological phenomena including bone metabolism. There is no direct evidence that the family causes osteoblastic skeletal metastasis. Aims The present study aims to evaluate whether overexpressed Wnt induces osteoblastic bone metastasis in a well‐established osteolytic bone metastatic model. Methods and Results The breast cancer‐derived 5a‐D‐Luc‐ZsGreen cells were transfected with Wnt1, Wnt3A, and Wnt5A expression vectors, producing stably highly expressing cells. These cells were intracardially transplanted in nude mice. Bone metastasis development was confirmed by fluorescence imaging. Hind‐limb bones including metastasis were dissected and visualized through micro‐CT imaging. After imaging, sections were stained with hematoxylin and eosin (H&E), and immunohistochemically stained with an anti‐SATB2 antibody. Luminescent imaging confirmed mice with bone metastases in the hind limbs. Micro‐CT imaging found an osteoblastic change only in bone metastasis of mice transplanted with Wnt1‐expressing cells. This was confirmed on H&E‐stained sections. SATB2 immunostaining showed differentiated osteoblasts were at the site of bone metastases in the diaphysis. SATB2 in the Wnt/β‐catenin pathway activated by overexpressed Wnt1 could induce osteoblastic change. Conclusion Our findings provided direct evidence Wnt1 is involved in osteoblastic bone metastasis development. Our model would be a powerful tool for further elucidating molecular mechanisms underlying the disease and developing effective therapies.

[64Cu]Cu-diacetyl-bis(N4-methylthiosemicarbazone) ([64Cu]Cu-ATSM) is a radioactive hypoxia-targeting therapeutic agent being investigated in clinical trials for malignant brain tumors. For the quality management of [64Cu]Cu-ATSM, understanding trace metal impurities’ effects on the chelate formation of 64Cu and ATSM is important. In this study, we conducted coordination chemistry studies on metal–ATSM complexes. First, the effects of nonradioactive metal ions (Cu2+, Ni2+, Zn2+, and Fe2+) on the formation of [64Cu]Cu-ATSM were evaluated. When the amount of Cu2+ or Ni2+ added was 1.2 mol or 288 mol, equivalent to ATSM, the labeling yield of [64Cu]Cu-ATSM fell below 90%. Little effect was observed even when excess amounts of Zn2+ or Fe2+ were added to the ATSM. Second, these metals were reacted with ATSM, and chelate formation was measured using ultraviolet–visible (UV-Vis) absorption spectra. UV-Vis spectra showed a rapid formation of Cu2+ and the ATSM complex upon mixing. The rate of chelate formation by Ni2+ and ATSM was lower than that by Cu-ATSM. Zn2+ and Fe2+ showed much slower reactions with the ATSM than Ni2+. Trace amounts of Ni2+, Zn2+, and Fe2+ showed little effect on [64Cu]Cu-ATSM’ quality, while the concentration of impurity Cu2+ must be controlled. These results can provide process management tools for radiopharmaceuticals.

Abstract Background We recently reported a new absorbed dose conversion method, RAP (RAtio of Pharmacokinetics), for 211At-meta-astatobenzylguanidine (211At-MABG) using a single biodistribution measurement, the percent injected dose/g. However, there were some mathematical ambiguities in determining the optimal timing of a single measurement of the percent injected dose/g. Thus, we aimed to mathematically reconstruct the RAP method and to examine the optimal timing of a single measurement. Methods We derived a new formalism of the RAP dose conversion method at time t. In addition, we acquired a formula to determine the optimal timing of a single measurement of the percent injected dose/g, assuming the one-compartment model for biological clearance. Results We investigated the new formalism’s performance using a representative RAP coefficient with radioactive decay weighting. Dose conversions by representative RAP coefficients predicted the true [211At]MABG absorbed doses with an error of 10% or less. The inverses of the representative RAP coefficients plotted at 4 h post-injection, which was the optimal timing reported in the previous work, were very close to the new inverses of the RAP coefficients 4 h post-injection. Next, the behavior of the optimal timing was analyzed by radiolabeled compounds with physical half-lives of 7.2 h and 10 d on various biological clearance half-lives. Behavior maps of optimal timing showed a tendency to converge to a constant value as the biological clearance half-life of a target increased. The areas of optimal timing for both compounds within a 5% or 10% prediction error were distributed around the optimal timing when the biological clearance half-life of a target was equal to that of the reference. Finally, an example of RAP dose conversion was demonstrated for [211At]MABG. Conclusions The RAP dose conversion method renovated by the new formalism was able to estimate the [211At]MABG absorbed dose using a similar pharmacokinetics, such as [131I]MIBG. The present formalism revealed optimizing imaging time points on absorbed dose conversion between two radiopharmaceuticals. Further analysis and clinical data will be needed to elucidate the validity of a behavior map of the optimal timing of a single measurement for targeted alpha-nuclide therapy.

Understanding the physicochemical properties of antibody–drug conjugates is critical to assess their quality at manufacturing and monitor them during subsequent storage. For radiometal–antibody complexes, it is important to control the properties of the antibody–chelator conjugate to maintain the quality of the final product. We have been developing 64Cu-labeled anti-epidermal growth factor receptor antibody NCAB001 (64Cu-NCAB001) for the early diagnosis and therapy of pancreatic cancer with positron-emission tomography. Here, we characterized the larger size variants contained in the antibody–chelator conjugate PCTA-NCAB001 by multi-angle light scattering coupled with size-exclusion chromatography. Secondly, we developed a chromatographic method to remove these size variants. Lastly, we demonstrated the stability of PCTA-NCAB001 after the removal of size variants. Dimer and oligomers were identified in PCTA-NCAB001. These larger size variants, together with some smaller size variants, could be removed by hydrophobic interaction chromatography. The PCTA-NCAB001 product, after the removal of these size variants, could be stored at 4 °C for six months. The methods developed here can be applied to assure the quality of PCTA-NCAB001 and other antibody–drug conjugates to facilitate the development of antibody–radiometal conjugates for positron-emission tomography and radioimmunotherapy of malignant cancers.

CD137 is an attractive target for cancer immunotherapy, but its expression in normal tissues induces some adverse effects in patients receiving CD137-targeted therapy. To overcome this issue, we developed a switch antibody, STA551, that binds to CD137 only under high ATP concentrations around cells. This study quantified biodistribution of murine switch antibodies in human CD137 knock-in mice to show the viability of the switch antibody concept in vivo. We utilized four antibodies: Sta-MB, Ure-MB, Sta-mIgG1, and KLH-MB. Sta-MB is a switch antibody having the variable region of STA551. The MB is a murine Fc highly binding to murine Fcγ receptor II. Ure-MB has a variable region mimicking the clinically available anti-CD137 agonist antibody urelumab, binding to CD137 regardless of ATP concentration. Sta-mIgG1 has the same variable region as Sta-MB but has the standard murine constant region. KLH-MB binds to keyhole limpet hemocyanin. The four antibodies were radiolabeled with In-111, SPECT/CT imaging was conducted in human CD137 knock-in mice, and the uptake in regions of interest was quantified. 111In-labeled Sta-MB and Sta-mIgG1 showed high uptake in tumors but low uptake in the lymph nodes and spleen in human CD137 knock-in mice. On the other hand, Ure-MB highly accumulated not only in tumors but also in the lymph nodes and spleen. KLH-MB showed low uptake in the tumors, lymph nodes, and spleen. The present study provides evidence that the switch antibody concept works in vivo. Our findings encourage further clinical imaging studies to evaluate the biodistribution of STA551 in patients.

Abstract The differentiation of non-small cell lung cancer (NSCLC) and radiation pneumonitis (RP) is critically essential for selecting optimal clinical therapeutic strategies to manage post carbon-ion radiotherapy (CIRT) in patients with NSCLC. The aim of this study was to assess the ability of 18F-FDG PET/CT metabolic parameters and its textural image features to differentiate NSCLC from RP after CIRT to develop a differential diagnosis of malignancy and benign lesion. We retrospectively analyzed 18F-FDG PET/CT image data from 32 patients with histopathologically proven NSCLC who were scheduled to undergo CIRT and 31 patients diagnosed with RP after CIRT. The SUV parameters, metabolic tumor volume (MTV), total lesion glycolysis (TLG) as well as fifty-six texture parameters derived from seven matrices were determined using PETSTAT image-analysis software. Data were statistically compared between NSCLC and RP using Wilcoxon rank-sum tests. Diagnostic accuracy was assessed using receiver operating characteristics (ROC) curves. Several texture parameters significantly differed between NSCLC and RP (p

Recent studies demonstrate that redox imbalance of NAD+/NADH and NADP+/NADPH pairs due to impaired respiration may trigger two “hidden” metabolic pathways on the crossroad between mitochondrial dysfunction, senescence, and proliferation: “β-oxidation shuttle” and “hydride transfer complex (HTC) cycle”. The “β-oxidation shuttle” induces NAD+/NADH redox imbalance in mitochondria, while HTC cycle maintains the redox balance of cytosolic NAD+/NADH, increasing the redox disbalance of NADP+/NADPH. Senescence appears to depend on high cytoplasmic NADH but low NADPH, while proliferation depends on high cytoplasmic NAD+ and NADPH that are under mitochondrial control. Thus, activating or deactivating the HTC cycle can be crucial to cell fate – senescence or proliferation. These pathways are a source of enormous cataplerosis. They support the production of large amounts of NADPH and intermediates for lipid synthesis and membrane biogenesis, as well as for DNA synthesis.

We investigated whether benzothiazepines could produce anxiolytic effects via allopregnanolone (ALLO) biosynthesis in mice. We compared the behavioral effects caused by benzothiazepines to those caused by carbamazepine and sodium valproate. We found that a pretreatment with finasteride (a 5 alpha-reductase inhibitor) suppressed carbamazepine-induced anxiolytic effects but not the effects of sodium valproate. Similar to carbamazepine, diltiazem and JTV-519 displayed anxiolytic effects that were suppressed by a pretreatment with finasteride. We clearly demonstrate that the benzothiazepines, diltiazem and JTV-519, exert an anxiolytic-like effect via ALLO biosynthesis in mice.

α-Sulfoquinovosylacyl-1,3-propanediol (SQAP) is a semi-synthetic derivative of natural sulfoglycolipid that sensitizes tumors to external-beam radiotherapy. How SQAP affects internal radiotherapy, however, is not known. Here, we investigated the effects of SQAP for radioimmunotherapy (RIT) targeting tissue factor (TF) in a stroma-rich refractory pancreatic cancer mouse model, BxPC-3. A low dose of SQAP (2 mg/kg) increased tumor uptake of the 111In-labeled anti-TF antibody 1849, indicating increased tumor perfusion. The addition of SQAP enhanced the growth-inhibitory effect of 90Y-labeled 1849 without leading to severe body weight changes, allowing for the dose of 90Y-labeled 1849 to be reduced to half that when used alone. Histologic analysis revealed few necrotic and apoptotic cells, but Ki-67–positive proliferating cells and increased vascular formation were detected. These results suggest that the addition of a low dose of SQAP may improve the therapeutic efficacy of TF-targeted RIT by increasing tumor perfusion, even for stroma-rich refractory pancreatic cancer.

The purpose of this study was to compare parameter estimates for the 2-compartment and diffusion kurtosis imaging models obtained from diffusion-weighted imaging (DWI) of aquaporin-4 (AQP4) expression-controlled cells, and to look for biomarkers that indicate differences in the cell membrane water permeability. DWI was performed on AQP4-expressing and non-expressing cells and the signal was analyzed with the 2-compartment and diffusion kurtosis imaging models. For the 2-compartment model, the diffusion coefficients (Df, Ds) and volume fractions (Ff, Fs, Ff = 1-Fs) of the fast and slow compartments were estimated. For the diffusion kurtosis imaging model, estimates of the diffusion kurtosis (K) and corrected diffusion coefficient (D) were obtained. For the 2-compartment model, Ds and Fs showed clear differences between AQP4-expressing and non-expressing cells. Fs was also sensitive to cell density. There was no clear relationship with the cell type for the diffusion kurtosis imaging model parameters. Changes to cell membrane water permeability due to AQP4 expression affected DWI of cell suspensions. For the 2-compartment and diffusion kurtosis imaging models, Ds was the parameter most sensitive to differences in AQP4 expression.

Hypoxia plays important roles in the prognosis of malignant brain tumors such as glioblastoma because it causes drug delivery deficiencies and the induction of hypoxia-inducible factor-1α in tumor cells. Extensive hypoxic areas are associated with poor prognosis of these fatal diseases. We previously reported that multiple administrations of the hypoxia-targeted internal radiotherapy agent 64Cu-diacetyl-bis(N4-methylthiosemicarbazone) (64Cu-ATSM), four times at intervals of 1 or 2 weeks, show antitumor effects in glioblastoma without treatment-related adverse events. Before initiating clinical trials, preclinical safety studies using Cu-ATSM composed of stable isotopes and its precursor ATSM were required to understand the potential risks of systemic and repeated chemical exposure of our investigational drug. In this study, the concentrations of Cu-ATSM and ATSM in mouse plasma after intravenous administration were determined by liquid chromatography–tandem mass spectrometry, and the half-lives were estimated to be 21.5 and 22.4 minutes for Cu-ATSM and ATSM, respectively. Based on this result, approach 2 of the current ICH M3 [R2] guideline was adopted, and a 7-day intravenous toxicity study was conducted in mice. Cu-ATSM and ATSM in a ratio of 2:25 mimicking our current investigational drug was used, and no adverse effects were observed when Cu-ATSM and ATSM were administered at 81 μg/kg. These results and those of previous studies suggest that our current investigational drug formulation containing Cu-ATSM and ATSM at a dose of 15 μg can be safely administered to patients once per week for 4 weeks for treatment with 64Cu-ATSM.

The α-emitter 211At-labeled meta-astatobenzylguanidine (211At-MABG) has a strong antitumor effect on pheochromocytoma xenograft tumors and holds great promise as a new therapeutic option for malignant pheochromocytoma. To evaluate the acute radiation-related toxicity of 211At-MABG, we conducted biodistribution and dosimetry studies of 211At-MABG in ICR mice to estimate the doses absorbed by organs. We determined the maximum tolerated doses (MTD) of 211At-MABG on the basis of body weight loss and assessed the acute radiation-related toxicity induced by MTD administration on the basis of organ weights, histologic features, hematologic indices, and biochemical indices. The biodistribution and dosimetry studies of α-emitting 211At-MABG revealed high doses absorbed by most organs except the brain in ICR mice. The administration of 1.1, 2.2, and 3.3 MBq of 211At-MABG induced transient body weight loss, and 4.4 MBq of 211At-MABG induced unrecoverable body weight loss; thus, the MTD was 3.3 MBq for ICR mice. Although by day 5 the administration of 3.3 MBq had induced some radiation-related toxicity symptoms—such as body weight loss and leucopenia, which are generally observed in radiation therapy including β−-emitting radiopharmaceuticals—the mice had recovered by day 28. We observed no unexpected severe toxicity in ICR mice despite the high absorbed doses in most organs, especially the thyroid, heart, stomach, and adrenal glands. Our findings suggest that therapeutic treatments with appropriate doses of 211At-MABG estimated by dosimetry in each patient could be tolerated, although lower doses may initially be necessary to ensure patient safety in the first-in-human study.

pH (low) insertion peptides (pHLIPs) have been developed for cancer imaging and therapy targeting the acidic extracellular microenvironment. However, the characteristics of intratumoral distribution (ITD) of pHLIPs are not yet fully understood. This study aimed to reveal the details of the ITD of pHLIPs and their spatial relationship with other tumor features of concern. The fluorescent dye-labeled pHLIPs were intravenously administered to subcutaneous xenograft mouse models of U87MG and IGR-OV1 expressing αVβ3 integrins (using large necrotic tumors). The αVβ3 integrin-targeting Cy5.5-RAFT-c(-RGDfK-)4 was used as a reference. In vivo and ex vivo fluorescence imaging, whole-tumor section imaging, fluorescence microscopy, and multiplexed fluorescence colocalization analysis were performed. The ITD of fluorescent dye-labeled pHLIPs was heterogeneous, having a high degree of colocalization with necrosis. A direct one-to-one comparison of highly magnified images revealed the cellular localization of pHLIP in pyknotic, karyorrhexis, and karyolytic necrotic cells. pHLIP and hypoxia were spatially contiguous but not overlapping cellularly. The hypoxic region was found between the ITDs of pHLIP and the cRGD peptide and the Ki-67 proliferative activity remained detectable in the pHLIP-accumulated regions. The results provide a better understanding of the characteristics of ITD of pHLIPs, leading to new insights into the theranostic applications of pHLIPs.

Detecting tumor lesions 64Cu-labeled anti-epidermal growth factor receptor (EGFR) antibody (64Cu-NCAB001 ipPET). Here, we conducted an extended single-dose toxicity study of 64Cu-NCAB001 ipPET in mice based on approach 1 of the current ICH M3 [R2] guideline, as our new drug formulation contains 45 μg of the antibody. We used NCAB001 labeled with stable copper isotope instead of 64Cu. The total content of size variants was approximately 6.0% throughout the study. The relative binding potency of Cu-NCAB001 to recombinant human EGFR was comparable to that of cetuximab. The general and neurological toxicities of Cu-NCAB001 ipPET at 62.5 or 625 μg/kg were assessed in mice. The no-observed-adverse-effect level of Cu-NCAB001 was 625 μg/kg, a dose approximately 1000-fold higher at the μg/kg level than the dose of 64Cu-NCAB001 in our formulation (45 µg). The size variants did not affect the safety of the formulation. Therefore, clinical studies on the efficacy of 64Cu-NCAB001 ipPET for early detection of pancreatic cancer using PET imaging can be safely conducted.

We evaluated the long-term stability of a newly developed viscoelastic phantom made of polyacrylamide (PAAm) gel for magnetic resonance elastography (MRE) and ultrasound-based shear-wave elastography (US SWE). The stiffness of the cylindrical phantom was measured at 0, 13 and 18 months. Storage and loss moduli were measured with MRE, and shear-wave speed (SWS) was measured with US SWE. Long-term stability was evaluated in accordance with the Quantitative Imaging Biomarker Alliance (QIBA) profiles for each modality. The initial storage and loss moduli of the phantom were 5.01±0.22 and 1.11±0.15 respectively, and SWS was 2.57±0.04 m/s. The weight of the phantom decreased by 0.6% over the 18 months. When measured with MRE, the stiffness of the phantom decreased and changes to the storage and loss moduli were -3.0% and -4.6% between 0 and 13 months, and -4.3% and 0.0% between 0 and 18 months. The US measurements found that SWS decreased by 2.4% over the first 13 months and 3.6% at 18 months. These changes were smaller than the tolerances specified in the QIBA profiles, so the viscoelastic PAAm gel phantom fulfilled the condition for long-term stability. This new phantom has the potential to be used as a quality assurance and quality control phantom for MRE and US SWE.

This review is directed to the redox-modulating properties and anticancer effect of vitamin K. The concept is focused on two aspects: (i) redox-cycle of vitamin K and its effect on the calcium homeostasis, “oncogenic” and “onco-suppressive” reactive oxygen species and the specific induction of oxidative stress in cancer; (ii) vitamin K plus C as a powerful redox-system, which forms a bypass between mitochondrial complexes II and III and thus prevents mitochondrial dysfunction, restores oxidative phosphorylation and aerobic glycolysis, modulates the redox-state of endogenous redox-pairs, eliminates the hypoxic environment of cancer cells and induces cell death. The analyzed data suggest that vitamin C&K can sensitize cancer cells to conventional chemotherapy, which allows achievement of a lower effective dose of the drug and minimizing the harmful side-effects. The review is intended for a wide audience of readers - from students to specialists in the field.

Abstract Background The present study proposed a new concept for targeted radionuclide therapy (TRT) to improve the intratumoral distribution of radioactivity using two different radiopharmaceuticals. We examined the efficacy of a combination of a tetrameric cyclic Arg-Gly-Asp (cRGD) peptide-based radiopharmaceutical, 64Cu-cyclam-RAFT-c(-RGDfK-)4 (64Cu-RaftRGD, an αVβ3 integrin [αVβ3] tracer), and 64Cu-diacetyl-bis (N 4-methylthiosemicarbazone) (64Cu-ATSM, a supposed tracer for hypoxic metabolism) in a small animal tumor model. Results Mice with subcutaneous αVβ3-positive U87MG glioblastoma xenografts were used. The intratumoral distribution of a near-infrared dye, Cy5.5-labeled RAFT-c(-RGDfK-)4 (Cy5.5-RaftRGD), 64Cu-RaftRGD, and 64Cu-ATSM was visualized by fluorescence imaging and autoradiography of the co-injected Cy5.5-RaftRGD with 64Cu-RaftRGD or 64Cu-ATSM at 3 h postinjection. Mice were treated with a single intravenous dose of the vehicle solution (control), 18.5 or 37 MBq of 64Cu-RaftRGD or 64Cu-ATSM, or a combination (18.5 MBq of each agent). The tumor volume, tumor cell proliferation, body weight, survival, and tumor and organ uptake of radiopharmaceuticals were assessed. It was shown that Cy5.5-RaftRGD colocalized with 64Cu-RaftRGD and could be used as a surrogate for the radioactive agent. The intratumoral distribution of Cy5.5-RaftRGD and 64Cu-ATSM was discordant and nearly complementary, indicating a more uniform distribution of radioactivity achievable with the combined use of 64Cu-RaftRGD and 64Cu-ATSM. Neither 64Cu-RaftRGD nor 64Cu-ATSM showed significant effects on tumor growth at 18.5 MBq. The combination of both (18.5 MBq each) showed sustained inhibitory effects against tumor growth and tumor cell proliferation and prolonged the survival of the mice, compared to that by either single agent at 37 MBq. Interestingly, the uptake of the combination by the tumor was higher than that of 64Cu-RaftRGD alone, but lower than that of 64Cu-ATSM alone. The kidneys showed the highest uptake of 64Cu-RaftRGD, whereas the liver exhibited the highest uptake of 64Cu-ATSM. No obvious adverse effects were observed in all treated mice. Conclusions The combination of 64Cu-RaftRGD and 64Cu-ATSM achieved an improved antitumor effect owing to the more uniform intratumoral distribution of radioactivity. Thus, combining different radiopharmaceuticals to improve the intratumoral distribution would be a promising concept for more effective and safer TRT.

Early diagnosis of pancreatic cancer using current imaging modalities remains challenging. We have developed a new approach to identify tumor lesions ≥ 3 mm in the pancreas by positron emission tomography (PET) with a new intraperitoneally administered 64Cu-labeled anti-epidermal growth factor receptor (EGFR) antibody (encoded as NCAB001), called 64Cu-NCAB001 ipPET. Generally, in clinical research, a radiometal-antibody complex must be prepared immediately before use at the imaging site. To make 64Cu-NCAB001 ipPET available to daily clinical practices in a sustainable way, the NCAB001-chelator conjugate and 64Cu-NCAB001 must be characterized and stabilized. NCAB001 was manufactured under cGMP conditions. NCAB001 was conjugated with a bifunctional chelator (p-SCN-Bn-PCTA), and the antibody-chelator conjugate (PCTA-NCAB001) was characterized by LC/MS and ELISA. Thereafter, to effectively manufacture 64Cu-NCAB001, we developed a new formulation to stabilize PCTA-NCAB001 and 64Cu-NCAB001. An average of three PCTA chelators were conjugated per molecule of NCAB001. The relative binding potency of PCTA-NCAB001 was comparable to cetuximab. The formulation consisting of acetate buffer, glycine, and polysorbate-80 stabilized PCTA-NCAB001 for a year-long storage. Additionally, this formulation enabled the stabilization of 64Cu-NCAB001 for up to 24 h after radiolabeling with a sufficient radioactivity concentration for clinical use. These results may accelerate the future use of 64Cu-NCAB001 ipPET in clinical settings for the early diagnosis and treatment of pancreatic cancer.

Glioblastoma is the most aggressive malignant brain tumor in humans and is difficult to cure using current treatment options. Hypoxic regions are frequently found in glioblastoma, and increased levels of hypoxia are associated with poor clinical outcomes of glioblastoma patients. Hypoxia plays important roles in the progression and recurrence of glioblastoma because of drug delivery deficiencies and induction of hypoxia-inducible factor-1α in tumor cells, which lead to poor prognosis. We focused on a promising hypoxia-targeted internal radiotherapy agent, 64Cu-diacetyl-bis (N4-methylthiosemicarbazone) (64Cu-ATSM), to address the need for additional treatment for glioblastoma. This compound can target the overreduced state under hypoxic conditions within tumors. Clinical positron emission tomography studies using radiolabeled Cu-ATSM have shown that Cu-ATSM accumulates in glioblastoma and its uptake is associated with high hypoxia-inducible factor-1α expression. To evaluate the therapeutic potential of this agent for glioblastoma, we examined the efficacy of 64Cu-ATSM in mice bearing U87MG glioblastoma tumors. Administration of single dosage (18.5, 37, 74, 111, and 148 MBq) and multiple dosages (37 MBq × 4) of 64Cu-ATSM was investigated. Single administration of 64Cu-ATSM in high-dose groups dose-dependently inhibited tumor growth and prolonged survival, with slight and reverse signs of adverse events. Multiple dosages of 64Cu-ATSM remarkably inhibited tumor growth and prolonged survival. By splitting the dose of 64Cu-ATSM, no adverse effects were observed. Our findings indicate that multiple administrations of 64Cu-ATSM have effective antitumor effects in glioblastoma without side effects, indicating its potential for treating this fatal disease.

Actinium-225 (225Ac) is a promising radionuclide used in targeted alpha therapy (TAT). Although 225Ac labeling of bifunctional chelating ligands is effective, previous in vivo studies reported that free 225Ac can be released from the drugs and that such free 225Ac is predominantly accumulated in the liver and could cause unexpected toxicity. To accelerate the clinical development of 225Ac TAT with a variety of drugs, preparing methods to deal with any unexpected toxicity would be valuable. The aim of this study was to evaluate the feasibility of various chelators for reducing and excreting free 225Ac and compare their chemical structures. Nine candidate chelators (D-penicillamine, dimercaprol, Ca-DTPA, Ca-EDTA, CyDTA, GEDTA TTHA, Ca-TTHA, and DO3A) were evaluated in vitro and in vivo. The biodistribution and dosimetry of free 225Ac were examined in mice before an in vivo chelating study. The liver exhibited pronounced 225Ac uptake, with an estimated human absorbed dose of 4.76 SvRBE5/MBq. Aminopolycarboxylate chelators with five and six carboxylic groups, Ca-DTPA and Ca-TTHA, significantly reduced 225Ac retention in the liver (22% and 30%, respectively). Significant 225Ac reductions were observed in the heart and remainder of the body with both Ca-DTPA and Ca-TTHA, and in the lung, kidney, and spleen with Ca-TTHA. In vitro interaction analysis supported the in vivo reduction ability of Ca-DTPA and Ca-TTHA. In conclusion, aminopolycarboxylate chelators with five and six carboxylic groups, Ca-DTPA and Ca-TTHA, were effective for whole-body clearance of free 225Ac. This feasibility study provides useful information for reducing undesirable radiation exposure from free 225Ac.

The prognosis of advanced mesothelioma is poor. Podoplanin (PDPN) is highly expressed in most malignant mesothelioma. This study aimed to evaluate the potential alpha-radioimmunotherapy (RIT) with a newly developed anti-PDPN antibody, NZ-16, compared with a previous antibody, NZ-12. Methods: The in vitro properties of radiolabeled antibodies were evaluated by cell binding and competitive inhibition assays using PDPN-expressing H226 mesothelioma cells. The biodistribution of 111In-labeled antibodies was studied in tumor-bearing mice. The absorbed doses were estimated based on biodistribution data. Tumor volumes and body weights of mice treated with 90Y- and 225Ac-labeled NZ-16 were measured for 56 days. Histologic analysis was conducted. Results: The radiolabeled NZ-16 specifically bound to H226 cells with higher affinity than NZ-12. The biodistribution studies showed higher tumor uptake of radiolabeled NZ-16 compared with NZ-12, providing higher absorbed doses to tumors. RIT with 225Ac- and 90Y-labeled NZ-16 had a significantly higher antitumor effect than RIT with 90Y-labeled NZ-12. 225Ac-labeled NZ-16 induced a larger amount of necrotic change and showed a tendency to suppress tumor volumes and prolonged survival than 90Y-labeled NZ-16. There is no obvious adverse effect. Conclusions: Alpha-RIT with the newly developed NZ-16 is a promising therapeutic option for malignant mesothelioma.

Objectives: To improve the prognosis of pancreatic cancer, new imaging methods to identify tumor lesions at a size of 64Cu-labeled new anti-epidermal growth factor receptor (EGFR) antibody (encoded as NCAB001), called 64Cu-NCAB001 ipPET. Methods: NCAB001 was manufactured under cGMP conditions and labeled with 64Cu. The radiochemical and biological properties of 64Cu-NCAB001 were evaluated. Tumor uptake of an ip-administered 64Cu-NCAB001 in mice with orthotopic pancreatic tumor xPA1-DC xenografts was also evaluated. Pharmacokinetics and radiation dosimetry were examined using PET images acquired after the ip administration of 64Cu-NCAB001 into cynomolgus monkeys with pharmacologic safety monitoring. Results: Radio-chromatography, cell-binding assays, and biodistribution of 64Cu-NCAB001 in mice were identical to those of our previous data with clinically available cetuximab. Small tumor lesions in the pancreas (≥3 mm) of mice could be identified by 64Cu-NCAB001 ipPET. The ip administration of 64Cu-NCAB001 into monkeys was safely conducted using ultrasound imaging. PET images in monkeys showed that ip-administered 64Cu-NCAB001 was distributed throughout the intraperitoneal cavity for up to 6 h and cleared thereafter. Most of the radioactivity was distributed in the liver and the large intestine. The radioactivity around the pancreas became negligible 24 h after administration. The estimated human effective dose was 0.0174 mSv/MBq. Conclusion: Our data support the initiation of clinical trials of 64Cu-NCAB001 ipPET to transfer this promising tool for the early diagnosis of pancreatic cancers.

Our graphical review expands the analysis of cancer vulnerabilities for high dose vitamin C, based on several facts, illustrating the cytotoxic potential of the ascorbate free radical (AFR) via impairment of mitochondrial respiration and the mechanisms of its elimination in mammals by the membrane-bound NADH:cytochrome b5 oxidoreductase 3 (Cyb5R3). We propose that vitamin C can function in “protective mode” or “destructive mode” affecting cellular homeostasis, depending on the intracellular “steady-state” concentration of AFR and differential expression/activity of Cyb5R3 in cancerous and normal cells. Thus, a specific anti-cancer effect can be achieved at high doses of vitamin C therapy. The review is intended for a wide audience of readers – from students to specialists in the field. Keywords: Cancer, Mitochondria, Ascorbate free radical, NADH:Cytochrome b5 oxidoreductase 3, Redox signaling

Colorectal cancer is a frequent cause of death worldwide. The detection and treatment of small nodules are crucial for improving survival of colorectal cancer patients. Submillimeter tumors are useful tools for developing novel methods to approach this issue. However, there are no suitable in vivo models that allow easy monitoring of the growth of these tumors. This study established a xenograft mouse model of subcutaneous submillimeter tumors with human colorectal cancer HT-29 cells. We transplanted a single spheroid formed by HT-29 cells expressing red fluorescent protein (RFP) (HT-29-RFP). Additionally, we adopted our newly developed radiation-crosslinked gelatin hydrogel microwells (rGHMs), which can be used as a culture base to form spheroids and as a transplantation scaffold with biocompatibility and biodegradability. Spheroids approximately 700 μm in size were uniformly created in seven days in the respective rGHMs. Every single spheroid was extracted either with or without rGHM and transplanted into the subcutis of severe combined immunodeficiency (SCID) mice (n = 4). After 21 days, the spheroids inoculated together with rGHM successfully formed uniform subcutaneous submillimeter tumor xenografts that were observable in vivo in a stereoscopic fluorescence microscope in all transplanted mice. In contrast, spheroids transplanted without rGHM also developed small tumors in all mice but showed higher variability in size than those transplanted with rGHM. During transplantation, the rGHM ensured easy handling and stabilization of the position of a single spheroid. Inoculation of spheroids with rGHM in the nude mice was similarly examined (n = 4), showing that only one out of four mice formed tumors. In conclusion, rGHM effectively formed spheroids and created uniformed xenografted submillimeter tumors of HT-29-RFP in SCID mice. Our model could provide a useful platform to develop medicines and methods for detection and treatment of small nodules of colorectal cancer.