[SPECT radiopharmaceuticals -- novelties and new possibilities]. / SPECT-radiofarmakonok -- újdonságok és új lehetoségek.

Actual state of affairs and future perspectives of SPECT radiopharmaceuticals regarding local and international data were summarized. Beyond conventional gamma-emitting radioisotopes, localization studies with beta emitting therapeutic radiopharmaceuticals hold increasing importance. Extension of hybrid (SPECT/CT) equipments has modified conventional scintigraphic and SPECT methods as well but more important changes come into the world through novel ligands for specific diagnoses and therapy.

Impact of DOTA-Chelators on the Antitumor Activity of 177Lu-DOTA-Rituximab Preparations in Lymphoma Tumor-Bearing Mice.

Background: This work aimed to evaluate the influence of two chelators: DOTA(SCN) and DOTA(NHS) on radioimmunotherapy using 177Lu-DOTA-Rituximab preparations in murine lymphoma xenograft models. Subsequently, based on animal data, the organ radiation-absorbed doses were extrapolated to humans (adult male). Materials and Methods: Therapeutic efficacy of 177Lu-DOTA-Rituximab was evaluated in male nude mice bearing either Raji (B lymphocyte, CD20+) and Jurkat (T lymphocyte, CD20) xenografts, utilizing an anti-CD20 antibody-Rituximab conjugate with either DOTA(SCN) or DOTA(NHS). The DOTA-Rituximab conjugates were prepared in the form of freeze-dried kits. Results: All radioimmunoconjugates were obtained with high radiolabeling yield (radiochemical purity, RCP > 95%) and specific activity of ca. 0.5 GBq/mg. Therapeutic effects of 177Lu-DOTA-Rituximab were observed in animals regardless whether DOTA(SCN) or DOTA(NHS) were used for conjugation. Importantly, therapy involving 177Lu-DOTA-Rituximab was more effective than use of Rituximab alone. Conclusions: The degree of antitumor efficacy was dependent on the type of applied bifunctional chelators conjugated to mAb. However, this difference was not statistically significant. Dosimetry calculations showed that the absorbed radiation doses extrapolated to humans were very low for osteogenic cells regardless of the conjugates. Organs like the liver and spleen, treated with 177Lu-DOTA(SCN)-Rituximab, showed similar radiation absorbed doses when compared with 177Lu-DOTA(NHS)-Rituximab.

Identification of a novel cis-regulatory element for UV-B-induced transcription in Arabidopsis.

Ultraviolet-B light (UV-B) regulates the expression of genes in a wavelength- and fluence rate-dependent fashion. A signaling pathway consisting of CONSTITUTIVE PHOTOMORPHOGENESIS 1 (COP1) and UV RESISTANCE LOCUS 8 (UVR 8) mediates responsiveness to longer wavelength, low intensity UV-B light-activating, for example, HY5 gene expression. By contrast, transcription of another group of genes, including ANAC13, modulated by shorter wavelength, higher intensity UV-B is controlled by a yet unknown and largely COP1-independent signaling cascade. Here we provide evidence by promoter deletion analysis, and characterization of genetic mutants displaying aberrant expression patterns, that two cis-regulatory elements, designated MRE(ANAC13) and UVBox(ANAC13), are required for maximal UV-B induction of the ANAC13 gene in transgenic plants. These elements are located in the proximal 150-bp region of the ANAC13 promoter. They show no significant similarity to each other; the putative MRE(ANAC13) (-AACCTT-) is closely related to MRE(CHS) (-AACCTA-) found in the CHALCONE SYNTHASE (CHS) gene, whereas UVBox(ANAC13) (with core sequence CAAG) represents a novel cis-regulatory element. The novel UVBox(ANAC13) sequence is significantly enriched in the promoter region of a subset of UV-B-induced genes with similar activation properties as ANAC13. In addition, we demonstrate that expression of a chimeric gene containing only the dimerized 12-mer containing UVBox(ANAC13) fused to a minimal CaMV35S promoter/luciferase reporter is (i) efficiently induced by shorter wavelength, higher intensity UV-B, but (ii) does not respond either to longer wavelength UV-B and red light or (iii) to abscisic acid treatment and osmotic, salt, heat and cold stresses.

Temperature increase induced by modulated electrohyperthermia (oncothermia®) in the anesthetized pig liver.

AIM OF STUDY: Is to show the intrahepatic temperature development in anesthetized pig. MATERIALS AND METHODS: Temperature development in the liver of anesthetized pig is measured to study the thermal effects of capacitive coupled energy transfer. The treatment was made by modulated electrohyperthermia (mEHT, trade name: oncothermia ®), controlled by a fluoroptical temperature sensing positioned by the ultrasound-guided process. Various fits of coupling were studied. RESULTS: The intrahepatic temperature at the end of the treatment ranged 40.5-44.8°C, while the skin temperature ranged 36.8-41.8°C depending on the coupling arrangement. CONCLUSION: mEHT is a feasible method to deliver deep heat to the liver of an anesthetized pig.

Thulium-170-labeled microparticles for local radiotherapy: preliminary studies.

The present article describes the preparation, characterization, and biological evaluation of Thulium-170 ((170)Tm) [T1/2 = 128.4 days; Eßmax = 968 keV; Eγ = 84 keV (3.26%)] labeled tin oxide microparticles for its possible use in radiation synovectomy (RSV) of medium-sized joints. (170)Tm was produced by irradiation of natural thulium oxide target. 170Tm-labeled microparticles were synthesized with high yield and radionuclidic purity (> 99%) along with excellent in vitro stability by following a simple process. Particle sizes and morphology of the radiolabeled particles were examined by light microscope, dynamic light scattering, and transmission electron microscope and found to be of stable spherical morphology within the range of 1.4-3.2 µm. The preparation was injected into the knee joints of healthy Beagle dogs intraarticularly for biological studies. Serial whole-body and regional images were taken by single-photon-emission computed tomography (SPECT) and SPECT-CT cameras up to 9 months postadministration, which showed very low leakage (< 8% of I.D.) of the instilled particles. The majority of leaked radiocolloid particles were found in inguinal lymph nodes during the 9 months of follow-up. All the animals tolerated the treatment well; the compound did not show any possible radiotoxicological effect. These preliminary studies showed that 170Tm-labeled microparticles could be a promising nontoxic and effective radiopharmaceutical for RSV applications or later local antitumor therapy.

(99m)Tc-labelled nanosystem as tumour imaging agent for SPECT and SPECT/CT modalities.

We report the synthesis, in vitro and in vivo investigation of folate-targeted, biocompatible, biodegradable self-assembled nanoparticles radiolabelled with (99m)Tc, as potential new SPECT or SPECT/CT imaging agent. Nanoparticles with hydrodynamic size in the range of 75-200 nm were prepared by self-assembly of chitosan and folated poly-γ-glutamic acid, and then radiolabelled with (99m)Tc. The nanoparticles target tumour cells overexpressing folate receptors and internalize specifically into them to realize early tumour diagnosis detected by SPECT and SPECT/CT modalities. Rat hepatocellular carcinoma cells were used as model system. Cell specificity and tumour targeting efficacy of these nanosystems were investigated in vitro, and in vivo using SPECT and fusion nanoSPECT/CT imaging. In vitro results showed that the radiolabeled nanosystem was efficiently internalized by tumour cells. Whole-body biodistribution of the new radiolabelled, folate-targeted nanoparticles revealed higher uptake in the tumorous kidney compared to the non-tumorous contralateral side. Uptake by the lungs and thyroids was negligible, which confirmed the stability of the nanoparticles in vivo. In vivo SPECT and SPECT/CT imaging visually reinforced the uptake results and were in accordance with the biodistribution data: the new nanoparticles as a targeted contrast agent improve tumour targeting and are able to detect folate-receptor-overexpressing tumours in animal models with enhanced contrast.

In vitro and biodistribution examinations of Tc-99m-labelled doxorubicin-loaded nanoparticles.

BACKGROUND: Nanoparticles represent promising drug carrier systems. In the case of cytostatics such as doxorubicin, carrier colloid systems as human serum albumin (HSA) nanoparticles, may increase their therapeutic efficiency and decrease their side-effects (toxicity) and any potential multidrug resistance. In the present study, doxorubicin, as a widely used antineoplastic agent, was incorporated into the matrix of human serum albumin and three different particle-sized doxorubicin-loaded HSA nanoparticles were prepared, using a previously described desolvation method. Our objective was to find out if different particle sizes of colloid carriers can allow regarding the given cytostatic agent. MATERIAL AND METHODS: The three prepared nanoparticles were labelled using technetium (Tc-99m) and were tested for their physicochemical colloidal quality, fluctuations, and radiochemical stability. Biodistribution of different-sized radiolabelled colloids were determined by means of scintigraphic imaging studies in healthy male Wistar rats. Images were taken by gamma camera at several times and organ uptakes were estimated by quantitative ROI analysis. RESULTS: In vitro measurements showed that more than 95% of doxorubicin proportion was permanently adsorbed to human serum albumin. Radiolabelled doxorubicin-loaded particles had high-degree and durable labelling efficiency and particle size stability. Biodistribution results had a close correlation to earlier described results of radiocolloids in similar particle size ranges. In vivo examinations verified that colloid carriers have insignificant size fluctuations after an intravenous application and they show the proper distribution according to their particle size. CONCLUSIONS: Our investigations verified that different and stable particle sizes make drug carrier HSA nanoparticles possible to apply different drug targeting in a potential clinical use.