56 research outputs found
Tc-Glutathione Complex (Tc -GSH) : Labelling, Chemical Characterization and Biodistribution in Rats
The chemical structure of 99mTc-GSH has been estabilished using the 99Tc
isotope.
Labeling of glutathione with technetium in the presence of stanous chloride gave a high yield
result. In a comparative study between 99Tc
and 99Tc
glutathione, the Tc-GSH complex obtained
was purified and characterized by uv, visible spectroscopy, HPLC, Biogel chromatography, mass
and NMR spectroscopy. Stoichiometric analysis showed a 2 : 1 molar ratio of GSH/Tc for the
reaction. The molecular mass assessed by mass spectroscopy was 727 Da corresponding to an
oxo(bis) glutathione technetate. NMR studies demonstrated that each glutathione molecule was
coordinated to technetium via cysteinyl sulfur and nitrogen atoms. The biodistribution of the
complex was studied in normal rats. Blood clearance was rapid during the first hour involving a
biexponential curve ( t1/2
(1) : 50 min, t1/2
(2) : 400 min ). No radioactive accumulation was found in
any specific organ except kidney and bladder. All the activity excreted was found unchanged in
urine. In conclusion, Tc-GSH displayed an anionic dimer form as GSH-Tc-GSH. We assume that the
complex is a tetradentate (2N,2S) complex containing a pentavalent technetium coordinated by two
thiol and nitrogen atoms of both GSH ligands, and an apical oxo group
Alpha-particle emitting 213Bi-anti-EGFR immunoconjugates eradicate tumor cells independent of oxygenation
Hypoxia is a central problem in tumor treatment because hypoxic cells are less sensitive to chemo- and radiotherapy than normoxic cells. Radioresistance of hypoxic tumor cells is due to reduced sensitivity towards low Linear Energy Transfer (LET) radiation. High LET α-emitters are thought to eradicate tumor cells independent of cellular oxygenation. Therefore, the aim of this study was to demonstrate that the cell-bound α-particle emitting 213Bi immunoconjugates efficiently kill hypoxic just like normoxic CAL33 tumor cells. For that purpose CAL33 cells were incubated with 213Bianti- EGFR-MAb or irradiated with photons with a nominal energy of 6 MeV both
under hypoxic and normoxic conditions. Oxygenation of cells was checked via the hypoxia-associated marker HIF-1α. Survival of cells was analysed using the clonogenic assay. Cell viability was monitored with the WST colorimetric assay.
Results were evaluated statistically using a t-test and a Generalized Linear Mixed Model (GLMM). Survival and viability of CAL33 cells decreased both after incubation with increasing 213Bi-anti-EGFR-MAb activity concentrations (9.25 kBq/ml – 1.48 MBq/ml) and irradiation with increasing doses of photons (0.5 – 12 Gy). Following photon irradiation survival and viability of normoxic cells were significantly lower than those of hypoxic cells at all doses analysed. In contrast, cell death induced by 213Bianti- EGFR-MAb turned out to be independent of cellular oxygenation. These results demonstrate for the first time that α-particle emitting 213Bi-immunoconjugates
eradicate hypoxic tumor cells as effective as normoxic cells. Therefore, 213Biradioimmunotherapy seems to be an appropriate strategy for treatment of hypoxic tumors.JRC.E.5-Nuclear chemistr
Targeted alpha therapy in vivo: direct evidence for single cancer cell kill using 149Tb-rituximab
This study demonstrates high-efficiency sterilisation of single cancer cells in a SCID mouse model of leukaemia using rituximab, a monoclonal antibody that targets CD20, labelled with terbium-149, an alpha-emitting radionuclide. Radio-immunotherapy with 5.5MBq labelled antibody conjugate (1.11GBq/mg) 2 days after an intravenous graft of 5·106 Daudi cells resulted in tumour-free survival for >120 days in 89% of treated animals. In contrast, all control mice (no treatment or treated with 5 or 300µg unlabelled rituximab) developed lymphoma disease. At the end of the study period, 28.4%±4% of the long-lived daughter activity remained in the body, of which 91.1% was located in bone tissue and 6.3% in the liver. A relatively high daughter radioactivity concentration was found in the spleen (12%±2%/g), suggesting that the killed cancer cells are mainly eliminated through the spleen. This promising preliminary in vivo study suggests that targeted alpha therapy with 149Tb is worthy of consideration as a new-generation radio-immunotherapeutic approac
Treatment of Peritoneal Carcinomatosis by Targeted Delivery of the Radio-Labeled Tumor Homing Peptide 213Bi-DTPA-[F3]2 into the Nucleus of Tumor Cells
BACKGROUND: Alpha-particle emitting isotopes are effective novel tools in cancer therapy, but targeted delivery into tumors is a prerequisite of their application to avoid toxic side effects. Peritoneal carcinomatosis is a widespread dissemination of tumors throughout the peritoneal cavity. As peritoneal carcinomatosis is fatal in most cases, novel therapies are needed. F3 is a tumor homing peptide which is internalized into the nucleus of tumor cells upon binding to nucleolin on the cell surface. Therefore, F3 may be an appropriate carrier for alpha-particle emitting isotopes facilitating selective tumor therapies. PRINCIPAL FINDINGS: A dimer of the vascular tumor homing peptide F3 was chemically coupled to the alpha-emitter (213)Bi ((213)Bi-DTPA-[F3](2)). We found (213)Bi-DTPA-[F3](2) to accumulate in the nucleus of tumor cells in vitro and in intraperitoneally growing tumors in vivo. To study the anti-tumor activity of (213)Bi-DTPA-[F3](2) we treated mice bearing intraperitoneally growing xenograft tumors with (213)Bi-DTPA-[F3](2). In a tumor prevention study between the days 4-14 after inoculation of tumor cells 6x1.85 MBq (50 microCi) of (213)Bi-DTPA-[F3](2) were injected. In a tumor reduction study between the days 16-26 after inoculation of tumor cells 6x1.85 MBq of (213)Bi-DTPA-[F3](2) were injected. The survival time of the animals was increased from 51 to 93.5 days in the prevention study and from 57 days to 78 days in the tumor reduction study. No toxicity of the treatment was observed. In bio-distribution studies we found (213)Bi-DTPA-[F3](2) to accumulate in tumors but only low activities were found in control organs except for the kidneys, where (213)Bi-DTPA-[F3](2) is found due to renal excretion. CONCLUSIONS/SIGNIFICANCE: In conclusion we report that (213)Bi-DTPA-[F3](2) is a novel tool for the targeted delivery of alpha-emitters into the nucleus of tumor cells that effectively controls peritoneal carcinomatosis in preclinical models and may also be useful in oncology
Fractionated Locoregional Low-Dose Radioimmunotherapy Improves Survival in a Mouse Model of Diffuse Type Gastric Cancer Using A 213BI-conjugated Monoclonal Antibody
Locoregional radioimmunotherapy of intraperitoneal tumor cell dissemination of diffuse type gastric cancer using the Alpha-emitter 213Bi displayed good therapeutic results after single application depending on the time interval between tumor cell inoculation and injection of the 213Bi-immunoconjugate. The aim of the present study was to compare single versus double intraperitoneal injection of a tumor specific antibody (d9MAb) conjugated with low activities of 213Bi in terms of therapeutic efficacy and toxicity.JRC.E.5-Nuclear chemistr
177Lu-immunotherapy of experimental peritoneal carcinomatosis shows comparable effectiveness to 213Bi-immunotherapy, but causes toxicity not observed with 213Bi
Abstract
Purpose 213Bi-d9MAb-immunoconjugates targeting gastric
cancer cells have effectively cured peritoneal carcinomatosis
in a nude mouse model following intraperitoneal
injection. Because the β-emitter 177Lu has proven to be
beneficial in targeted therapy, 177Lu-d9MAb was investigated
in this study in order to compare its therapeutic
efficacy and toxicity with those of 213Bi-d9MAb.
Methods Nude mice were inoculated intraperitoneally with
HSC45-M2 gastric cancer cells expressing d9-E-cadherin
and were treated intraperitoneally 1 or 8 days later with
different activities of specific 177Lu-d9MAb immunoconjugates
targeting d9-E-cadherin or with nonspecific 177Lud8MAb.
Therapeutic efficacy was evaluated by monitoring
survival for up to 250 days. For evaluation of toxicity, both
biodistribution of 177Lu-d9MAb and blood cell counts were
determined at different time points and organs were
examined histopathologically.
Results Treatment with 177Lu-immunoconjugates (1.85,
7.4, 14.8 MBq) significantly prolonged survival. As
expected, treatment on day 1 after tumour cell inoculation
was more effective than treatment on day 8, and specific
177Lu-d9MAb conjugates were superior to nonspecific
177Lu-d8MAb. Treatment with 7.4 MBq of 177Lu-d9MAb
was most successful, with 90% of the animals surviving
longer than 250 days. However, treatment with therapeutically
effective activities of 177Lu-d9MAb was not free of
toxic side effects. In some animals lymphoblastic lymphoma,
proliferative glomerulonephritis and hepatocarcinoma
were seen but were not observed after treatment with 213Bid9MAb
at comparable therapeutic efficacy.
Conclusion The therapeutic efficacy of 177Lu-d9MAb
conjugates in peritoneal carcinomatosis is impaired by
toxic side effects. Because previous therapy with 213Bid9MAb
revealed comparable therapeutic efficacy without
toxicity it should be preferred for the treatment of
peritoneal carcinomatosis.JRC.DG.E.5-Nuclear chemistr
Therapeutic efficacy of intravesical -radioimmunotherapy with Bi-213-anti-EGFR-MAb in a human bladder cancer nude mouse model
Objectives: Due to a high recurrence rate after transurethral resection of urothelial cancer new therapeutic strategies are urgently needed. The aim of this study was to establish an orthotopic human bladder cancer mouse model using an EGFR-overexpressing cancer cell line and to compare the therapeutic efficacy of intravesically instilled Bi-213-anti-EGFR-MAb with Mitomycin C.
Methods: Female swiss nu/nu mice were catheterized and urothelial lesions were set by electrocautery. 2x106 luciferase transfected EJ28 cells were inoculated intravesically in 7 groups of 10 mice each. 1h, 7d and 14d after cancer cell inoculation 0.925 MBq of Bi-213-MAb were instilled into the bladder. 2 groups received 40µg Mitomycin C at 1h and 7d, 1 group received unconjugated MAb, the control only PBS. Tumor development and therapy response were imaged by bioluminescence imaging and survival observed up to 300d.
Results: Mice of the control group and those treated with the unconjugated MAb reached a median survival of 41d and 69d, respectively. Mice that underwent Bi-213-MAb therapy 1h, 7d and 14d after cell instillation survived >300d in 90%, 80% and 40%, respectively. Mitomycin C treatment after 1h and 7d resulted in a survival >300d in 40% and 50%, respectively.
Conclusions: Intravesically instilled Bi-213-MAb significantly prolonged survival without toxicity whereas Mitomycin C induced nephrotoxicity. Thus, therapy using Bi-213-anti-EGFR-MAb is a very promising approach to reduce the high recurrence rate of urothelial carcinoma.JRC.E.5-Nuclear chemistr
Lysine Protection against Bismuth Accumulation in the Kidneys when Using 213-Bi-DTPA-MAB.
Abstract not availableJRC.E-Institute for Transuranium Elements (Karlsruhe
High molecular mass radioimmunoconjugates are promising for intraperitoneal α-emitter immunotherapy due to prolonged retention in the peritoneum
Abstract
Aim. Therapeutic efficacy of intraperitoneal radioimmunotherapy is dependent on the time of retention of the radioimmunoconjugates within the peritoneal cavity. Therefore, the aim of this study was to investigate intraperitoneal retention of Fab, IgG and IgM radioimmunoconjugates.
Methods. Female Balb/c mice were injected with 213Bi- or 111In-labeled IgM, IgG and recombinant Fab conjugates intraperitoneally or intravenously. At different time points after injection, whole body distribution of radionuclides was imaged using a gamma camera. Distribution of radionuclides in selected organs was determined via γ-counting after sacrifice. Biological half-lives of the conjugates were calculated from whole body activities.
Results. After i.p. injection 213Bi-Fab rapidly accumulated in the kidneys indicative of glomerular filtration and reabsorption. Accumulation of 213Bi-IgG in the kidneys was significantly lower. 213Bi-IgM showed a striking accumulation in the liver 180 min after i.p. injection. 111In-IgG persisted in the circulation up to 72 h both after i.p. and i.v. injection. 111In-IgM showed a continuous accumulation in the liver. Moreover, 111In-IgM was significantly higher 24 h after i.v. injection than i.p. injection both in liver and spleen. These differences could be confirmed via scintigraphy. After injection of 111In-IgG differences in scintigraphic images between i.v. and i.p. were clearly visible only at 3 h. Biological half lives were 24 h, 45 h and 165 h for 111In-IgM, 111In-Fab and 111In-IgG, respectively.
Conclusion. Retention of radioimmunoconjugates in the peritoneal cavity positively correlates with the molecular mass of the antibody. Therefore, IgM radioimmunoconjugates should be preferably used in intraperitoneal radioimmunotherapy.JRC.E.5-Nuclear chemistr
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