RUNX3 regulates the susceptibility against EGFR-targeted non-small cell lung cancer therapy using 47Sc-conjugated cetuximab.

BACKGROUND: Radioimmunotherapy with cetuximab and conjugates with various radioisotopes is a feasible treatment option for different tumor models. Scandium-47 (47Sc), one of several ß--particle-emitting radioisotopes, displays favorable physical and chemical properties for conjugation to monoclonal antibodies. However, the therapeutic efficacy of 47Sc in preclinical and clinical studies is largely unknown. Given that intrinsic alterations in tumors greatly contribute to resistance to anti-epidermal growth factor receptor (EGFR)-targeted therapy, research on overcoming resistance to radioimmunotherapy using cetuximab is required. METHODS: 47Sc was produced by irradiation of a CaCO3 target at the HANARO research reactor in KAERI (Korea Atomic Energy Research Institute) and prepared by chromatographic separation of the irradiated target. Cetuximab was conjugated with 47Sc using the bifunctional chelating agent DTPA. Radiochemical purity was determined using instant thin-layer chromatography. The immunoreactivity of 47Sc-DTPA-cetuximab was evaluated using the Lindmo method and an in vitro cell-binding assay. The inhibitory effects of cetuximab and 47Sc-DTPA-cetuximab were confirmed using cell growth inhibition and BrdU cell proliferation assays. Differences in protein expression levels between cetuximab- and 47Sc-DTPA-cetuximab-treated cells were confirmed using western blotting. Complex formation between RUNX3 and DNA repair components was confirmed using immunoprecipitation and western blotting. RESULTS: Cetuximab induces cell cycle arrest and cell death in EGFR-overexpressing NSCLC cells. Radiolabeling of cetuximab with 47Sc led to increased therapeutic efficacy relative to cetuximab alone. Application of 47Sc-DTPA-cetuximab induced DNA damage responses, and activation of RUNX3 significantly enhanced the therapeutic efficacy of 47Sc-DTPA-cetuximab. RUNX3 mediated susceptibility to EGFR-targeted NSCLC therapy using 47Sc-DTPA-cetuximab via interaction with components of the DNA damage and repair machinery. CONCLUSIONS: 47Sc-DTPA-cetuximab promoted cell death in EGFR-overexpressing NSCLC cells by targeting EGFR and inducing DNA damage as a result of ß irradiation emitted from the conjugated 47Sc. Activation of RUNX3 played a key role in DNA damage and repair processes in response to the ionizing radiation and inhibited cell growth, thus leading to more effective tumor suppression. RUNX3 can potentially moderate susceptibility to 47Sc-conjugated cetuximab by modulating DNA damage and repair process mechanisms.

Accelerator-Based Production of Scandium Radioisotopes for Applications in Prostate Cancer: Toward Building a Pipeline for Rapid Development of Novel Theranostics.

In the field of nuclear medicine, the ß+ -emitting 43Sc and ß- -emitting 47Sc are promising candidates in cancer diagnosis and targeted radionuclide therapy (TRT) due to their favorable decay schema and shared pharmacokinetics as a true theranostic pair. Additionally, scandium is a group-3 transition metal (like 177Lu) and exhibits affinity for DOTA-based chelators, which have been studied in depth, making the barrier to implementation lower for 43/47Sc than for other proposed true theranostics. Before 43/47Sc can see widespread pre-clinical evaluation, however, an accessible production methodology must be established and each isotope's radiolabeling and animal imaging capabilities studied with a widely utilized tracer. As such, a simple means of converting an 18 MeV biomedical cyclotron to support solid targets and produce 43Sc via the 42Ca(d,n)43Sc reaction has been devised, exhibiting reasonable yields. The NatTi(γ,p)47Sc reaction is also investigated along with the successful implementation of chemical separation and purification methods for 43/47Sc. The conjugation of 43/47Sc with PSMA-617 at specific activities of up to 8.94 MBq/nmol and the subsequent imaging of LNCaP-ENZaR tumor xenografts in mouse models with both 43/47Sc-PSMA-617 are also presented.

PSMA-D4 Radioligand for Targeted Therapy of Prostate Cancer: Synthesis, Characteristics and Preliminary Assessment of Biological Properties.

A new PSMA ligand (PSMA-D4) containing the Glu-CO-Lys pharmacophore connected with a new linker system (L-Trp-4-Amc) and chelator DOTA was developed for radiolabeling with therapeutic radionuclides. Herein we describe the synthesis, radiolabeling, and preliminary biological evaluation of the novel PSMA-D4 ligand. Synthesized PSMA-D4 was characterized using TOF-ESI-MS, NMR, and HPLC methods. The novel compound was subject to molecular modeling with GCP-II to compare its binding mode to analogous reference compounds. The radiolabeling efficiency of PSMA-D4 with 177Lu, 90Y, 47Sc, and 225Ac was chromatographically tested. In vitro studies were carried out in PSMA-positive LNCaP tumor cells membranes. The ex vivo tissue distribution profile of the radioligands and Cerenkov luminescence imaging (CLI) was studied in LNCaP tumor-bearing mice. PSMA-D4 was synthesized in 24% yield and purity >97%. The radio complexes were obtained with high yields (>97%) and molar activity ranging from 0.11 to 17.2 GBq mcmol-1, depending on the radionuclide. In vitro assays confirmed high specific binding and affinity for all radiocomplexes. Biodistribution and imaging studies revealed high accumulation in LNCaP tumor xenografts and rapid clearance of radiocomplexes from blood and non-target tissues. These render PSMA-D4 a promising ligand for targeted therapy of prostate cancer (PCa) metastases.

47Sc and 46Sc cross-section measurement for an optimized 47Sc production with an 18 MeV medical PET cyclotron.

The availability of novel radionuclides plays a fundamental role in the development of personalized nuclear medicine. In particular, there is growing interest in pairs formed by two radioisotopes of the same element, the so-called true theranostic pairs, such as 61,64Cu/67Cu, 43,44Sc/47Sc and 155Tb/149,161Tb. In this case, the two radionuclides have identical kinetics and chemical reactivity, allowing to predict whether the patient will benefit from a therapeutic treatment on the basis of nuclear imaging data. 47Sc [t1/2 = 3.349 d, E [Formula: see text] = 440.9 keV (68.4%); 600.3 keV (31.6%), Eγ = 159.4 keV (68.3%)] is a promising radionuclide for theranostic applications in nuclear medicine. Its physical characteristics make it suitable for radionuclide therapy and allow SPECT imaging during treatment. Moreover, 47Sc is foreseen as the therapeutic partner of the ß+-emitters 43Sc and 44Sc, both under study for PET imaging, opening new avenues towards the true theranostics concept. 47Sc can be produced by proton irradiation of an enriched 50Ti oxide target with a medical cyclotron equipped with a solid target station. To optimize the production yield and the radionuclidic purity, an accurate knowledge of the production cross sections is necessary. In this paper, we report on measurements of the production cross section of 47Sc and 46Sc using enriched 50Ti titanium oxide targets, performed at the Bern University Hospital cyclotron laboratory. On the basis of the obtained results, a study of the production yield and purity was performed to assess the optimal irradiation conditions. A production test was also carried out to confirm these findings.

Branching ratios for the three most intense gamma rays in the decay of 47Ca.

A sample of 47Ca produced through isotope harvesting at the National Superconducting Cyclotron Laboratory was used to measure branching ratios of 7.17(5)%, 7.11(5)%, and 75.0(5)% for the 489.2, 807.9, and 1297.1 keV characteristic gamma rays, respectively. Based on these updated branching ratios, the ground state to ground state 47Ca to 47Sc beta decay branching ratio has been indirectly measured as 17.7(5)% and the ground state to 1297.1 keV excited state as 82.2(5)%. These values represent a greatly increased precision for all five branching ratios compared to the currently accepted values (Burrows, 2007). The measurements presented here were made relative to the ingrown 47Sc daughter in a47Ca sample and the well-established 159.4 keV gamma-ray branching ratio and the half-life for the decay of 47Sc (Reher et al., 1986; Meadows and Mode, 1968; Mommsen et al., 1980). These measurements were supported by verifying that the half-lives measured from characteristic gamma-ray peaks over multiple spectra for both 47Ca and 47Sc were consistent with previously reported values. Additionally, the half-lives of both 47Ca and 47Sc were independently measured with Liquid Scintillation Counting to reverify the previously reported values used in this study to find updated gamma-ray branching ratio values.

Investigations of proton and deuteron induced nuclear reactions on natural and enriched Titanium, Calcium and Vanadium targets, with special reference to the production of 47Sc.

47Sc could be used in SPECT imaging and also suitable for targeted therapy of small tumors. The excitation functions for the production of 47Sc and accompanying impurities via proton and deuteron bombardment of Calcium, Titanium and Vanadium targets were evaluated by three nuclear codes, ALICE, TALYS and EMPIRE. Therefrom, integral yields of 47Sc and also 46gSc as a main impurity were calculated. The various production routes of 47Sc were compared together. The results consistency with available experimental data was checked for each reaction. Based on the results, the 46Ca(d,n)47Sc reaction can leads to the high purity 47Sc with the moderate yield.

Production and purification of Scandium-47: A potential radioisotope for cancer theranostics.

In this study, production of 47Sc radionuclide by irradiating the natural titanium dioxide powder (TiO2) in the fast neutron flux (~3*1013ncm-2s-1) for 4 days in Tehran Research Reactor (TRR, Iran) and separation from titanium target was investigated. The study showed the feasibility of production 47Sc by TRR. The separation efficiency and radiochemical purity (ScCl3) of radio-scandium, 47Sc radionuclide purity were obtained 98%, 99% and 88% respectively.

Comparison between Three Promising ß-emitting Radionuclides, (67)Cu, (47)Sc and (161)Tb, with Emphasis on Doses Delivered to Minimal Residual Disease.

PURPOSE: Radionuclide therapy is increasingly seen as a promising option to target minimal residual disease. Copper-67, scandium-47 and terbium-161 have a medium-energy ß(-) emission which is similar to that of lutetium-177, but offer the advantage of having diagnostic partner isotopes suitable for pretreatment imaging. The aim of this study was to compare the efficacy of (67)Cu, (47)Sc and (161)Tb to irradiate small tumors. METHODS: The absorbed dose deriving from a homogeneous distribution of (67)Cu, (47)Sc or (161)Tb in water-density spheres was calculated with the Monte Carlo code CELLDOSE. The diameters of the spheres ranged from 5 mm to 10 µm, thus simulating micrometastases or single tumor cells. All electron emissions, including ß(-) spectra, Auger and conversion electrons were taken into account. Because these radionuclides differ in electron energy per decay, the simulations were run assuming that 1 MeV was released per µm(3), which would result in a dose of 160 Gy if totally absorbed. RESULTS: The absorbed dose was similar for the three radionuclides in the 5-mm sphere (146-149 Gy), but decreased differently in smaller spheres. In particular, (161)Tb delivered higher doses compared to the other radionuclides. For instance, in the 100-µm sphere, the absorbed dose was 24.1 Gy with (67)Cu, 14.8 Gy with (47)Sc and 44.5 Gy with (161)Tb. Auger and conversion electrons accounted for 71% of (161)Tb dose. The largest dose differences were found in cell-sized spheres. In the 10-µm sphere, the dose delivered by (161)Tb was 4.1 times higher than that from (67)Cu and 8.1 times that from (47)Sc. CONCLUSION: (161)Tb can effectively irradiate small tumors thanks to its decay spectrum that combines medium-energy ß(-) emission and low-energy conversion and Auger electrons. Therefore (161)Tb might be a better candidate than (67)Cu and (47)Sc for treating minimal residual disease in a clinical setting.

The modeling of the reaction cross sections in the production of teranositic radionuclides / La modelación de las secciones eficaces de reacción en la producción de radionúclidos teranosíticos

Abstract We utilize various nuclear reaction codes with the aim to guide, interpret, and support the experiments in the proton-induced production measurements of radionuclides for the development of innovative radio-pharmaceuticals. The understanding of reaction cross sections at low-intermediate energies is crucial in this context and requires the knowledge of nuclear models available in different codes, such as EMPIRE, TALYS, and FLUKA. These nuclear reaction codes serve as tool to interpret the measurement of production cross-sections and to complete the measurements with estimates of production of contaminants and/or stable isotopes that are difficult to measure. We illustrate different model calculations to simulate isotope production useful in experiments devoted to the measurement of proton-induced production of the two theranostic radio-isotopes 67Cu and 47Sc.

Resumen Utilizamos varios códigos de reacción nuclear con el objetivo de guiar, interpretar y respaldar los experimentos en las mediciones de producción de radionúclidos inducidas por protones para el desarrollo de productos radio-farmacéuticos innovadores. La comprensión de las secciones eficaces de reacción en energías intermedias bajas es crucial en este contexto y requiere el conocimiento de modelos nucleares disponibles en diferentes códigos, como EMPIRE, TALYS y FLUKA. Estos códigos de reacción nuclear sirven como herramienta para interpretar la medición de secciones eficaces de producción y para completar las mediciones con estimaciones de producción de contaminantes y / o isótopos estables que son difíciles de medir. Ilustramos diferentes cálculos de modelos para simular la producción de isótopos útiles en experimentos dedicados a la medición de la producción inducida por protones de los dos isótopos teranósticos 67Cu y 47Sc.