Mitigating Radiotoxicity in the Central Nervous System: Role of Proton Therapy.

OPINION STATEMENT: Central nervous system (CNS) radiotoxicity remains a challenge in neuro-oncology. Dose distribution advantages of protons over photons have prompted increased use of brain-directed proton therapy. While well-recognized among pediatric populations, the benefit of proton therapy among adults with CNS malignancies remains controversial. We herein discuss the role of protons in mitigating late CNS radiotoxicities in adult patients. Despite limited clinical trials, evidence suggests toxicity profile advantages of protons over conventional radiotherapy, including retention of neurocognitive function and brain volume. Modelling studies predict superior dose conformality of protons versus state-of-the-art photon techniques reduces late radiogenic vasculopathies, endocrinopathies, and malignancies. Conversely, potentially higher brain tissue necrosis rates following proton therapy highlight a need to resolve uncertainties surrounding the impact of variable biological effectiveness of protons on dose distribution. Clinical trials comparing best photon and particle-based therapy are underway to establish whether protons substantially improve long-term treatment-related outcomes in adults with CNS malignancies.

A comparison of the chemo- and radiotoxicity of thorium and uranium at different enrichment grades.

Uranium and thorium are heavy metals, and all of their isotopes are radioactive, so it is impossible to study chemical effects entirely independent of the radiation effects. In the present study, we tried to compare the chemo- and radiotoxicity of both metals, taking into account deterministic radiation damages reflected by acute radiation sickness and stochastic radiation damages leading to long-term health impairments (e.g., tumor induction). We made at first a literature search on acute median lethal doses that may be expected to be caused by chemical effects, as even acute radiation sickness as a manifestation of acute radiotoxicity occurs with latency. By simulations based on the biokinetic models of the International Commission on Radiological Protection and using the Integrated Modules for Bioassay Analysis software, we determined the amounts of uranium at different enrichment grades and thorium-232 leading to a short-term red bone marrow equivalent dose of 3.5 Sv considered to cause 50% lethality in humans. Different intake pathways for incorporation were considered, and values were compared to the mean lethal doses by chemotoxicity. To assess stochastic radiotoxicity, we calculated the uranium and thorium amounts leading to a committed effective dose of 200 mSv that is often considered critical. Mean lethal values for uranium and thorium are in the same order of magnitude so that the data do not give evidence for substantial differences in acute chemical toxicity. When comparing radiotoxicity, the reference units (activity in Bq or weight in g) must always be taken into account. The mean lethal equivalent dose to the red bone marrow of 3.5 Sv is reached by lower activities of thorium compared to uranium in soluble compounds. However, for uranium as well as thorium-232, acute radiation sickness is expected only after incorporation of amounts exceeding the mean lethal doses by chemotoxicity. Thus, acute radiation sickness is not a relevant clinical issue for either metal. Concerning stochastic radiation damages, thorium-232 is more radiotoxic than uranium if incorporating the same activities. Using weight units for comparison show that for soluble compounds, thorium-232 is more radiotoxic than low-enriched uranium in the case of ingestion but even more toxic than high-enriched uranium after inhalation or intravenous administration. For insoluble compounds, the situation differs as the stochastic radiotoxicity of thorium-232 ranges between depleted and natural uranium. For acute effects, the chemotoxicity of uranium, even at high enrichment grades, as well as thorium-232 exceeds deterministic radiotoxicity. Simulations show that thorium-232 is more radiotoxic than uranium expressed in activity units. If the comparison is based on weight units, the rankings depend on the uranium enrichment grades and the route of intake.

Radiation-Induced Pericardial Disease: Mechanisms, Diagnosis, and Treatment.

PURPOSE OF REVIEW: We aim to give a concise overview of the different clinical manifestations of both acute and long-term radiotherapy-related pericardial diseases, the underlying pathophysiology as well as the diagnosis and treatment options. RECENT FINDINGS: Radiotherapy-related pericardial disease is common, but despite radiotherapy being a cornerstone of many cancer treatments, this disease entity is relatively underrepresented in clinical trials, resulting in a paucity of research data on pathophysiology and management. Since the development of innovative cancer treatments, survival has significantly improved. Therefore, the importance of long-term treatment-related side effects increases, most notably cancer treatment-related cardiovascular toxicity. In patients undergoing radiotherapy as a part of their cancer treatment, radiotherapy-related pericardial disease can manifest early (during or shortly after radiotherapy administration) or very late (several years to decades after treatment). This exceptionally long latency period confronts physicians with treatment-related side effects of radiotherapy regimens that may have been abandoned already.

Safety of [177Lu]Lu-NeoB treatment: a preclinical study characterizing absorbed dose and acute, early, and late organ toxicity.

PURPOSE: The radiolabeled gastrin-releasing peptide receptor (GRPR)-targeting antagonist NeoB is a promising radioligand for imaging and therapy of GRPR-expressing malignancies. In the current study, we aimed to discover the target organs of toxicity and the radiotoxic effects to these organs, when repeated dosages of [177Lu]Lu-NeoB are administered to healthy female and male mice. METHODS: Animals received either 3 injections, with a 7-day interval, of vehicle (control group 1), 1200 pmol [175Lu]Lu-NeoB (control group 2) or 40 MBq/400 pmol, 80 MBq/800 pmol, and 120 MBq/1200 pmol [177Lu]Lu-NeoB (treatment groups 1, 2, and 3, respectively). At week 5, 19, and 43 after the first injection acute, early, and late organ toxicity, respectively, was determined. For this, histopathological and blood analyses were performed. To correlate the observed toxicity to absorbed dose, we also performed extensive biodistribution and dosimetry studies. RESULTS: The biodistribution study showed the highest absorbed doses in GRPR-expressing pancreas, the liver, and the kidneys (the main organs of excretion). Both control groups and almost all animals of treatment group 1 did not show any treatment-related toxicological effects. Despite the high absorbed doses, no clear microscopic signs of toxicity were found in the pancreas and the liver. Histological analysis indicated kidney damage in the form of hydronephrosis and nephropathy in treatment groups 2 and 3 that were sacrificed at the early and late time point. In the same groups, increased blood urea nitrogen levels were found. CONCLUSION: In general, repeated administration of [177Lu]Lu-NeoB was tolerated. The most significant radiotoxic effects were found in the kidneys, similar to other clinically applied radioligands. The results of this study underline the potential of [177Lu]Lu-NeoB as a promising option for clinical therapy.

Circulating levels of IL-6 and TGF-ß1 in patients with prostate cancer undergoing radiotherapy: associations with acute radiotoxicity and fatigue symptoms.

BACKGROUND: The goal of research was to investigate the possible relations between serum concentrations of IL-6 and TGF-ß1, individual and clinical characteristics, and adverse effects of radiotherapy in patients with prostate cancer: acute and late genitourinary and gastrointestinal toxicity, and fatigue. METHODS: Thirty-nine patients with localized or locally advanced prostate cancer who were treated with radiotherapy were enrolled in this study. The acute radiotoxicity grades and fatigue levels were assessed during the radiotherapy and 1 month after the radiotherapy. Estimation of the late radiotoxicity was performed every three months in the first year, every four months in the second year, and then every six months. Serum levels of IL-6 and TGF-ß1 were determined before radiotherapy and after the 25th radiotherapy fraction by ELISA. RESULTS: The significant positive association between diabetes mellitus and changes in acute genitourinary toxicity grades during the radiotherapy was observed in prostate cancer patients. In addition, patients who were smokers had significantly higher maximum fatigue levels in comparison with patients who were non-smokers. The circulating IL-6 levels were significantly higher after the 25th radiotherapy fraction in comparison with levels determined before radiotherapy. The significant positive correlations between pretreatment TGF-ß1 levels and maximum genitourinary toxicity grades and between TGF-ß1 levels after the 25th fraction and genitourinary toxicity grades after the 25th fraction, were found. The pretreatment IL-6 concentrations and TGF-ß1 concentrations after the 25th fraction were positively correlated with maximum genitourinary toxicity grades. The IL-6 levels after the 25th fraction were positively associated with genitourinary toxicity grades after this fraction. The pretreatment IL-6 concentrations were significantly positively correlated with maximum fatigue scores. The significant positive correlation between IL-6 concentrations and fatigue scores after the 25th fraction was determined. The positive correlations between IL-6 and TGF-ß1 concentrations measured after the 25th fraction and maximum fatigue scores were observed. CONCLUSIONS: Our results suggest that serum levels of IL-6 and TGF-ß1 might influence the severity of acute genitourinary radiotoxicity and fatigue in patients with prostate cancer. Combining clinical parameters and circulating cytokine levels might be useful for the prediction of adverse reactions to radiotherapy.

Marine Bacteria under Low-Intensity Radioactive Exposure: Model Experiments.

Radioactive contaminants create problems all over world, involving marine ecosystems, with their ecological importance increasing in the future. The review focuses on bioeffects of a series of alpha and beta emitting radioisotopes (americium-241, uranium-(235 + 238), thorium-232, and tritium) and gamma radiation. Low-intensity exposures are under special consideration. Great attention has been paid to luminous marine bacteria as representatives of marine microorganisms and a conventional bioassay system. This bioassay uses bacterial bioluminescence intensity as the main testing physiological parameter; currently, it is widely applied due to its simplicity and sensitivity. Dependences of the bacterial luminescence response on the exposure time and irradiation intensity were reviewed, and applicability of hormetic or threshold models was discussed. A number of aspects of molecular intracellular processes under exposure to low-intensity radiation were analyzed: (a) changes in the rates of enzymatic processes in bacteria with the bioluminescent system of coupled enzymatic reactions of NADH:FMN-oxidoreductase and bacterial luciferase taken as an example; (b) consumption of an intracellular reducer, NADH; (c) active role of reactive oxygen species; (d) repairing of the DNA damage. The results presented confirm the function of humic substances as natural radioprotectors.

One-Decade-Spanning transgenerational effects of historic radiation dose in wild populations of bank voles exposed to radioactive contamination following the chernobyl nuclear disaster.

The concept of historic radiation doses associated with accidental radioactive releases and their role in leading to radiation-induced non-targeted effects on affected wild animals are currently being evaluated. Previous research studying Fukushima butterfly, Chernobyl bird and fruit fly populations shows that the effects are transgenerational, underlined by the principles of genomic instability, and varied from one species to another. To further expand on the responses of and their sensitivity in different taxonomically distinct groups, the present study sought to reconstruct historic radiation doses and delineate their effects on bank voles (Clethrionomys glareolus) found within a 400-km radius of the Chernobyl Nuclear Power Plant meltdown site. Historic dose reconstruction from the whole-body dose rates for the bank vole samples for their parental generation at the time of radioactive release was performed. Relationships between the historic doses and cytogenetic aberrations and embryonic lethality were examined via graphical presentations. Results suggest that genomic instability develops at the historic dose range of 20-51 mGy while a radioadaptive response develops at the historic dose range of 51-356 mGy. The Linear No-Threshold (LNT) relationship was absent at historic doses of lower than 356 mGy at all generations. However, LNT was apparent when the very high historic dose of 10.28 Gy in one sampling year was factored into the dose response curve for the bank vole generation 21-22. It is worth being reminded that natural mutation accumulation and other environmental stressors outside the realm of dose effects could contribute to the observed effects in a multiple-stressor environment. Nevertheless, the consistent development of genomic instability and radio-adaptive response across generations and sampling sites unearths the utmost fundamental radiobiological principle of transgenerational non-targeted effects. As a result, it calls for better attention and regulation from global governing bodies of environmental health protection.

Protein-based fluorescent bioassay for low-dose gamma radiation exposures.

The study suggests an application of a coelenteramide-containing fluorescent protein (CLM-CFP) as a simplest bioassay for gamma radiation exposures. "Discharged obelin," a product of the bioluminescence reaction of the marine coelenterate Obelia longissima, was used as a representative of the CLM-CFP group. The bioassay is based on a simple enzymatic reaction-photochemical proton transfer in the coelenteramide-apoprotein complex. Components of this reaction differ in fluorescence color, providing, by this, an evaluation of the proton transfer efficiency in the photochemical process. This efficiency depends on the microenvironment of the coelenteramide within the protein complex, and, hence, can evaluate a destructive ability of gamma radiation. The CLM-CFP samples were exposed to gamma radiation (137Cs, 2 mGy/h) for 7 and 16 days at 20 °C and 5 °C, respectively. As a result, two fluorescence characteristics (overall fluorescence intensity and contributions of color components to the fluorescence spectra) were identified as bioassay parameters. Both parameters demonstrated high sensitivity of the CLM-CFP-based bioassay to the low-dose gamma radiation exposure (up to 100 mGy). Higher temperature (20 °C) enhanced the response of CLM-CFP to gamma radiation. This new bioassay can provide fluorescent multicolor assessment of protein destruction in cells and physiological liquids under exposure to low doses of gamma radiation. Graphical abstract ᅟ.

Fluorescent coelenteramide-containing protein as a color bioindicator for low-dose radiation effects.

The study addresses the application of fluorescent coelenteramide-containing proteins as color bioindicators for radiotoxicity evaluation. Biological effects of chronic low-dose radiation are under investigation. Tritiated water (200 MBq/L) was used as a model source of low-intensive ionizing radiation of beta type. 'Discharged obelin,' product of bioluminescent reaction of marine coelenterate Obelia longissimi, was used as a representative of the coelenteramide-containing proteins. Coelenteramide, fluorophore of discharged obelin, is a photochemically active molecule; it produces fluorescence forms of different color. Contributions of 'violet' and 'blue-green' forms to the visible fluorescence serve as tested parameters. The contributions depend on the coelenteramide's microenvironment in the protein, and, hence, evaluate distractive ability and toxicity of radiation. The protein samples were exposed to beta radiation for 18 days, and maximal dose accumulated by the samples was 0.28 Gy, being close to a tentative limit of a low-dose interval. Increase of relative contribution of 'violet' fluorescence under exposure to the beta irradiation was revealed. High sensitivity of the protein-based test system to low-dose ionizing radiation (to 0.03 Gy) was demonstrated. The study develops physicochemical understanding of radiotoxic effects. Graphical abstract Coelenteramide-containing protein (discharged obelin) changes fluorescence color under exposure to low-dose ionizing radiation of tritium.

Osteochondroma in long-term survivors of high-risk neuroblastoma.

BACKGROUND: Osteochondromas are benign bony protrusions that can be spontaneous or associated with radiotherapy (RT). Current treatment of high-risk neuroblastoma includes dose-intensive chemotherapy, local RT, an anti-GD2 monoclonal antibody (MoAb), and isotretinoin. Late effects are emerging. METHODS: The authors examined osteochondromas in 362 patients who were aged <10 years when diagnosed with neuroblastoma, had received a MoAb plus isotretinoin since 2000, and had survived >24 months from the time of the first dose of the MoAb. The incidence rate of osteochondroma was determined using the competing risks approach, in which the primary event was osteochondroma calculated from the date of neuroblastoma diagnosis and the competing event was death without osteochondroma. RESULTS: A total of 21 osteochondroma cases were found among 14 patients who were aged 5.7 to 15.3 years (median, 10.4 years) and 3.1 to 11.2 years (median, 8.2 years) from the time of neuroblastoma diagnosis. The cumulative incidence rate was 0.6% at 5 years and 4.9% at 10 years from the neuroblastoma diagnosis. Nine osteochondromas were revealed incidentally during assessments of neuroblastoma disease status or bone age. Thirteen osteochondromas were detected outside RT portals and had characteristics of spontaneous forms. Complications were limited to pain necessitating surgical resection in 3 patients, but follow-up was short at 0.3 to 7.7 years (median, 3.5 years). CONCLUSIONS: Osteochondromas in long-term survivors of neuroblastoma should be expected because these benign growths can be related to RT and these patients undergo radiologic studies over years, are monitored for late toxicities through and beyond adolescence, and receive special attention (because of concerns about disease recurrence) if they develop a bony protuberance. A pathogenic role for chemotherapy, anti-GD2 MoAbs, or isotretinoin remains speculative.

Severe radiotoxicity in an allogeneic transplant recipient with a heterozygous ATM mutation.

Patients receiving radiotherapy often experience toxicity of the skin and mucous membranes. While radiotherapy is a mainstay of myeloablative conditioning for allogeneic hematopoietic stem cell transplantation (ASCT), no risk factors for radiotoxicity have been identified in this setting. Here, we report on a patient with excessive radiation-induced toxicity after ASCT who carried a heterozygous mutation in the Ataxia telangiectasia mutated (ATM) gene. This is the first case to suggest a genetic basis for increased radiotoxicity after myeloablative ASCT.

Estimating how contouring differences affect normal tissue complication probability modelling.

Background and purpose: Normal tissue complication probability (NTCP) models are developed from large retrospective datasets where automatic contouring is often used to contour the organs at risk. This study proposes a methodology to estimate how discrepancies between two sets of contours are reflected on NTCP model performance. We apply this methodology to heart contours within a dataset of non-small cell lung cancer (NSCLC) patients. Materials and methods: One of the contour sets is designated the ground truth and a dosimetric parameter derived from it is used to simulate outcomes via a predefined NTCP relationship. For each simulated outcome, the selected dosimetric parameters associated with each contour set are individually used to fit a toxicity model and their performance is compared. Our dataset comprised 605 stage IIA-IIIB NSCLC patients. Manual, deep learning, and atlas-based heart contours were available. Results: How contour differences were reflected in NTCP model performance depended on the slope of the predefined model, the dosimetric parameter utilized, and the size of the cohort. The impact of contour differences on NTCP model performance increased with steeper NTCP curves. In our dataset, parameters on the low range of the dose-volume histogram were more robust to contour differences. Conclusions: Our methodology can be used to estimate whether a given contouring model is fit for NTCP model development. For the heart in comparable datasets, average Dice should be at least as high as between our manual and deep learning contours for shallow NTCP relationships (88.5 ± 4.5 %) and higher for steep relationships.

Assessment of cancer risk and radiological effects from 210Po and 210Pb with consumption of wild medicinal herbal plants.

BACKGROUND: Plants' raw materials can accumulate chemical elements, including radioisotopes, to some extent and reflect the region they grow in. Due to their high environmental content and toxicity, natural radionuclides - polonium 210Po and lead 210Pb are the most dangerous radioisotopes for human health. METHODS: 70 raw medicinal herbal materials from 54 popular wild-growing medicinal plant species, most of them included in the European Pharmacopoeia, were collected across three regions. In 210 samples, the activity concentrations of 210Po and 210Pb were determined, and their radiotoxicity and cancer risk were calculated. RESULTS: The results of 210Po and 210Pb activities measured in herbal raw material were from 0.12 mBq g-1 dry weight in the fruits of the common chestnut (Aesculus hippocastanum) to 19.7 mBq g-1 dw in herb of ground elder (Aegopodium podagraria) for 210Po, while for 210Pb ranged from 0.16 mBq g-1 dw to 34.3 mBq g-1 dw in the same plants. There were statistically significant differences between 210Po and 210Pb content in leaves, herbs, flowers, and fruit. The studies indicated that the estimated annual effective radiation dose from Polish medicinal herbs consumption was low, ranging 0.03-105 µSv from 210Po and 0.02-98.2 µSv from 210Pb, while the risk of cancer morbidity and mortality ranged from 10-5 to 10-9. CONCLUSIONS: Consumption of the tested medicinal herbs is safe from the radiological point of view and, based on the predictions related to the calculated risk of cancer, should not increase the probability of its occurrence.

TGF-ß3 increases the severity of radiation-induced oral mucositis and salivary gland fibrosis in a mouse model.

PURPOSE: Toxicities from head and neck (H&N) radiotherapy (RT) may affect patient quality of life and can be dose-limiting. Proteins from the transforming growth factor beta (TGF-ß) family are key players in the fibrotic response. While TGF-ß1 is known to be pro-fibrotic, TGF-ß3 has mainly been considered anti-fibrotic. Moreover, TGF-ß3 has been shown to act protective against acute toxicities after radio- and chemotherapy. In the present study, we investigated the effect of TGF-ß3 treatment during fractionated H&N RT in a mouse model. MATERIALS AND METHODS: 30 C57BL/6J mice were assigned to three treatment groups. The RT + TGF-ß3 group received local fractionated H&N RT with 66 Gy over five days, combined with TGF-ß3-injections at 24-hour intervals. Animals in the RT reference group received identical RT without TGF-ß3 treatment. The non-irradiated control group was sham-irradiated according to the same RT schedule. In the follow-up period, body weight and symptoms of oral mucositis and lip dermatitis were monitored. Saliva was sampled at five time points. The experiment was terminated 105 d after the first RT fraction. Submandibular and sublingual glands were preserved, sectioned, and stained with Masson's trichrome to visualize collagen. RESULTS: A subset of mice in the RT + TGF-ß3 group displayed increased severity of oral mucositis and increased weight loss, resulting in a significant increase in mortality. Collagen content was significantly increased in the submandibular and sublingual glands for the surviving RT + TGF-ß3 mice, compared with non-irradiated controls. In the RT reference group, collagen content was significantly increased in the submandibular gland only. Both RT groups displayed lower saliva production after treatment compared to controls. TGF-ß3 treatment did not impact saliva production. CONCLUSIONS: When repeatedly administered during fractionated RT at the current dose, TGF-ß3 treatment increased acute H&N radiation toxicities and increased mortality. Furthermore, TGF-ß3 treatment may increase the severity of radiation-induced salivary gland fibrosis.

Tritiated stainless steel (nano)particle release following a nuclear dismantling incident scenario: Significant exposure of freshwater ecosystem benthic zone.

Nuclear facilities continue to be developed to help meet global energy demands while reducing fossil fuel use. However, an incident during the dismantling of these facilities could accidentally release tritiated particles (e.g. stainless steel) into the environment. Herein, we investigated the environmental dosimetry, fate, and impact of tritiated stainless steel (nano)particles (1 mg.L-1 particles and 1 MBq.L-1 tritium) using indoor freshwater aquatic mesocosms to mimic a pond ecosystem. The tritium (bio)distribution and particle fate and (bio)transformation were monitored in the different environmental compartments over 4 weeks using beta counting and chemical analysis. Impacts on picoplanktonic and picobenthic communities, and the benthic freshwater snail, Anisus vortex, were assessed as indicators of environmental health. Following contamination, some tritium (∼16%) desorbed into the water column while the particles rapidly settled onto the sediment. After 4 weeks, the particles and the majority of the tritium (>80%) had accumulated in the sediment, indicating a high exposure of the benthic ecological niche. Indeed, the benthic grazers presented significant behavioral changes despite low steel uptake (<0.01%). These results provide knowledge on the potential environmental impacts of incidental tritiated (nano)particles, which will allow for improved hazard and risk management.

Prediction of radiotherapy toxicity: 20 years of COPERNIC radiosensitivity diagnosis procedure.

PURPOSE: Since 2004, in the frame of the care pathway, our Research Unit has replied to the demand of expertise of radiation oncologists about the individual radiosensitivity of some of their patients. This procedure, called COPERNIC, is based on a skin biopsy and the radiation-induced nucleoshuttling of the ATM protein (the RIANS model), a major actor of DNA break repair and signaling. In 2016, with the first 117COPERNIC fibroblast lines, we obtained a significant correlation between the maximum number of the nuclear ATM foci, pATMmax, and the CTCAE severity grade of the post-radiotherapy tissue reactions. In this study, we propose to verify the validity of our previous findings with a new COPERNIC data subset obtained in the 2014-2024 period. MATERIALS AND METHODS: We applied a standard immunofluorescence technique to quiescent COPERNIC fibroblasts to assess, after 2Gy, the level of micronuclei, γH2AX and pATM foci. The 117 COPERNIC data published in 2016 were considered as the reference data subset. A new COPERNIC data subset composed of 133fibroblast cell lines was considered as the validating data subset. RESULTS: Our data showed that spontaneous or residual micronuclei levels, and residual γH2AX foci levels cannot predict CTCAE grades. Conversely, the linear formula linking the maximal number of pATM foci and the corresponding CTCAE grade and obtained in 2016 from the reference data subset fitted well the validating data. CONCLUSIONS: The maximal number of pATM foci appears to be one of the most reliable biomarkers for predicting post-radiotherapy radiotoxicity.

Extended acute toxicity study of (188) Re-liposome in rats.

Liposomes can selectively target cancer sites and carry payloads, thereby improving diagnostic and therapeutic effectiveness as well as reducing toxicity. To evaluate therapeutic strategies, it is essential to use animal models reflecting important safety aspects before clinical application. As our previous study found that a high dosage (185 of MBq) of (188) Re-N,N-bis (2-mercaptoethyl)-N',N'-diethylethylenediamine-labeled pegylated liposomes ((188) Re-liposome) induced a decrease in white blood cell (WBC) count in Sprague-Dawley rats 7 days postinjection, the objective of the present study was to investigate extended acute radiotoxicity of (188) Re-liposome. Rats were administered via intravenous (i.v.) injection with (188) Re-liposome (185, 55.5 and 18.5 MBq), normal saline as a blank control or non-radioactive liposome as a vehicle control. Mortality, clinical signs, food consumption, body weights, urinary, biochemical and hematological analyzes were examined. In addition, gross necropsy and histopathological examinations were also performed at the end of the follow-up period. None of the rats died and no clinical sign was observed during the 28-day study period. Only male rats receiving (188) Re-liposome at a high dosage (185 MBq) displayed a slight weight loss compared with the control rats. In both male and female rats, the WBC counts of both high-dose and medium-dose (55.5 MBq) groups reduced significantly 7 days postinjection, but recovered to the normal range on Study Day 29. There was no significant difference in urinary analyzes, biochemical parameters and histopathological assessments between the (188) Re-liposome-treated and control groups. The information generated from the present study on extended acute toxicity of (188) Re-liposome will serve as a safety reference for radiopharmaceuticals in early-phase clinical trials.

Evaluation of the Effect of Chelating Arms and Carrier Agents on t he Radiotoxicity of TAT Agents.

Targeted Alpha Therapy (TAT) is considered an evolving therapeutic option for cancer cells, in which a carrier molecule labeling with an α-emitter radionuclide make the bond with a specific functional or molecular target. α-particles with high Linear Energy Transfer (LET) own an increased Relative Biological Effectiveness (RBE) over common ß-emitting radionuclides. Normal tissue toxicity due to non-specific uptake of mother and daughter α-emitter radionuclides seems to be the main conflict in clinical applications. The present survey reviews the available preclinical and clinical studies investigating healthy tissue toxicity of the applicable α -emitters and particular strategies proposed for optimizing targeted alpha therapy success in cancer patients.

Validation of Freshly Isolated Rat Renal Cells as a Tool for Preclinical Assessment of Radiolabeled Receptor-Specific Peptide Uptake in the Kidney.

The synthetic analogs of regulatory peptides radiolabeled with adequate radionuclides are perspective tools in nuclear medicine. However, undesirable uptake and retention in the kidney limit their application. Specific in vitro methods are used to evaluate undesirable renal accumulation. Therefore, we investigated the usefulness of freshly isolated rat renal cells for evaluating renal cellular uptake of receptor-specific peptide analogs. Special attention was given to megalin as this transport system is an important contributor to the active renal uptake of the peptides. Freshly isolated renal cells were obtained from native rat kidneys by the collagenase method. Compounds with known accumulation in renal cells were used to verify the viability of cellular transport systems. Megalin expressions in isolated rat renal cells were compared to two other potential renal cell models by Western blotting. Specific tubular cell markers were used to confirm the presence of proximal tubular cells expressing megalin in isolated rat renal cell preparations by immunohistochemistry. Colocalization experiments on isolated rat kidney cells confirmed the presence of proximal tubular cells bearing megalin in preparations. The applicability of the method was tested by an accumulation study with several analogs of somatostatin and gastrin labeled with indium-111 or lutetium-177. Therefore, isolated rat renal cells may be an effective screening tool for in vitro analyses of renal uptake and comparative renal accumulation studies of radiolabeled peptides or other radiolabeled compounds with potential nephrotoxicity.

Modifications in cellular viability, DNA damage and stress responses inflicted in cancer cells by copper-64 ions.

Due to combined therapeutical emissions, a high linear energy transfer Auger-electrons with the longer ranged ß- particles, 64Cu-based radiopharmaceuticals raise particular theragnostic interest in cancer, by joined therapeutic and real-time PET imaging properties. The in vitro study aimed to investigate the biological and molecular background of 64CuCl2 therapy by analyzing the damages and stress responses inflicted in various human normal and tumor cell lines. Colon (HT29 and HCT116) and prostate carcinoma (DU145) cell lines, as well as human normal BJ fibroblasts, were treated up to 72 h with 2-40 MBq/mL 64CuCl2. Radioisotope uptake and retention were assessed, and cell viability/death, DNA damage, oxidative stress, and the expression of 84 stress genes were investigated at various time points after [64Cu]CuCl2 addition. All the investigated cells incorporated 64Cu ions similarly, independent of their tumoral or normal status, but their fate after exposure to [64Cu]CuCl2 was cell-dependent. The most striking cytotoxic effects of the radioisotope were registered in colon carcinoma HCT116 cells, for which a substantial decrease in the number of metabolically active cells, and an increased DNA damage and oxidative stress were registered. The stress gene expression study highlighted the activation of both death and repair mechanisms in these cells, related to extrinsic apoptosis, necrosis/necroptosis or autophagy, and cell cycle arrest, nucleotide excision repair, antioxidant, and hypoxic responses, respectively. The in vitro study indicated that 40 MBq/mL [64Cu]CuCl2 delivers a therapeutic effect in human colon carcinoma, but its use is limited by harmful, yet lower effects on normal fibroblasts. The exposure of tumor cells to 20 MBq/mL [64Cu]CuCl2, might be used for a softer approach aiming for a lower radiotoxicity in normal fibroblasts as compared to tumor cells. This radioactive concentration was able to induce a persistent decrease in the number of metabolically active cells, accompanied by DNA damage and oxidative stress, associated with significant changes in stress gene expression in HCT116 colon cancer cells.