[Radiation exposure of staff during endovascular brachytherapy with Re-188 after PTA in the peripheral blood stream]. / Strahlenexposition des Personals bei der endovaskulären Brachytherapie (EVBT) mit Re-188 nach PTA im peripheren Stromgebiet.

Endovascular brachytherapy using a balloon catheter filled with Re-188 solution is a promising method for the prophylaxis of restenosis in peripheral blood circulation after percutaneous transluminal angioplasty (PTA) treatments. Thereby about 20 GBq Re-188 with a specific activity of about 5 GBq/ml are used. The high ionisation density of the beta radiation with high energy leads to selective irradiation of the blood vessel wall near the catheter, whereas the surrounding tissue remains almost unaffected. However the hospital staff has to carry out some work steps within close range to the high activity during preparation and therapy, causing a high risk of skin exposure, in particular at the hands. Estimations and measurements of the maximal local skin dose were made with thin-layered thermoluminescence dosimeters. It was assessed that the annual dose limit for skin of 500 mSv may be exceeded considerably when using conventional procedures and considering the expected number of 75 treatments per annum. By using the newly developed rhenium-188 application device "FlowMedical Application System" the exposure risk for the staff could be reduced drastically. The maximum skin dose of 76 mSv for the radiologist and of 50 mSv for the physicist was decreased to 2 mSv per treatment for both of them. Consequently, from the radiation protection point of view, the itm Rhenium-PTA is a safe method. Any exceeding of the dose limit can be prevented.

Cell death triggered by alpha-emitting 213Bi-immunoconjugates in HSC45-M2 gastric cancer cells is different from apoptotic cell death.

PURPOSE: Radioimmunotherapy with alpha-particle-emitting nuclides, such as 213Bi, is a promising concept for the elimination of small tumour nodules or single disseminated tumour cells. The aim of this study was to investigate cellular damage and the mode of cell death triggered by 213Bi-immunoconjugates. METHODS: Human gastric cancer cells (HSC45-M2) expressing d9-E-cadherin were incubated with different levels of activity of 213Bi-d9MAb targeting d9-E-cadherin and 213Bi-d8MAb, which does not bind to d9-E-cadherin. Micronucleated (M) cells, abnormal (A) cells and apoptotic (A) [(MAA)] cells were scored microscopically in the MAA assay following fluorescent staining of nuclei and cytoplasm. Chromosomal aberrations were analysed microscopically following Giemsa staining. The effect of z-VAD-fmk, known to inhibit apoptosis, on the prevention of cell death was investigated following treatment of HSC45-M2 cells with sorbitol as well as 213Bi-d9MAb. Activation of caspase 3 after incubation of HSC45-M2 cells with both sorbitol and 213Bi-d9MAb was analysed via Western blotting. RESULTS: Following incubation of HSC45-M2 human gastric cancer cells expressing d9-E-cadherin with 213Bi-d9MAb the number of cells killed increased proportional to the applied activity concentration. Microscopically visible effects of alpha-irradiation of HSC45-M2 cells were formation of micronuclei and severe chromosomal aberrations. Preferential induction of these lesions with specific 213Bi-d9MAb compared with unspecific 213Bi-d8MAb (not targeting d9-E-cadherin) was not observed if the number of floating, i.e. unbound 213Bi-immunoconjugates per cell exceeded 2 x 10(4), most likely due to intense crossfire. In contrast to sorbitol-induced cell death, cell death triggered by 213Bi-immunoconjugates was independent of caspase 3 activation and could not be inhibited by z-VAD-fmk, known to suppress the apoptotic pathway. CONCLUSION: 213Bi-immunoconjugates seem to induce a mode of cell death different from apoptosis in HSC45-M2 cells.

Locoregional alpha-radioimmunotherapy of intraperitoneal tumor cell dissemination using a tumor-specific monoclonal antibody.

PURPOSE: The locoregional application of tumor-specific antibodies conjugated with highly cytotoxic alpha-emitters is a promising new strategy for therapy of i.p. tumor cell dissemination. Using this approach, an antibody specifically targeting diffuse-type gastric cancer cells was coupled to the high linear energy transfer alpha-emitter (213)Bi for treatment of i.p. tumor cell spread in a nude mouse model. EXPERIMENTAL DESIGN: Nude mice were inoculated with HSC45-M2 human gastric cancer cells expressing mutant d9-E-cadherin. Twenty-four h after cell inoculation, mice received i.p. injections of either (213)Bi-d9MAb specifically binding to mutant d9-E-cadherin of HSC45-M2 cells or unspecific (213)Bi-d8MAb (7.4 or 22.2 MBq). Survival of treated animals was monitored compared with controls that had been injected with nonlabeled monoclonal antibody (MAb) or saline. Toxicity was evaluated by WBC counts after injection of 1.85, 7.4, or 22.2 MBq and analysis of chromosomal aberrations of bone marrow cells after injection of 7.4, 14.8, or 22.2 MBq. RESULTS: Survival rates of control mice and of mice treated with (213)Bi-MAbs differed significantly: the mean survival of untreated controls and mice that were given the nonlabeled antibody was 23 and 26 days. After injection of 22.2 MBq of the specific (213)Bi-d9MAb or the unspecific (213)Bi-d8MAb, mean survival was at least 143 or 130 days, respectively. Treatment with 7.4 MBq of (213)Bi-d9MAb increased mean survival to at least 232 days and with (213)Bi-d8MAb to at least 172 days. WBC counts decreased within 2 days after (213)Bi-therapy but reached pretreatment values between day 14 and 21 after activity injection. Chromosomal aberrations in bone marrow cells could only be detected at day 1 after (213)Bi-therapy. The frequency of chromosomal damages increased depending on the applied (213)Bi-activity. CONCLUSIONS: The therapeutic efficacy of the (213)Bi-d9MAb together with a low bone marrow toxicity support the locoregional therapy for that subgroup of diffuse-type gastric carcinoma patients expressing d9-E-cadherin.

In vitro evaluation of 213Bi-rituximab versus external gamma irradiation for the treatment of B-CLL patients: relative biological efficacy with respect to apoptosis induction and chromosomal damage.

External source radiotherapy and beta radioimmunotherapy (RIT) are effective treatments for lymphoid malignancies. The development of RIT with alpha emitters is attractive because of the high linear energy transfer (LET) and short path length, allowing higher tumour cell kill and lower toxicity to healthy tissues. We assessed the relative biological efficacy (RBE) of alpha RIT (in vitro) compared to external gamma irradiation with respect to induction of apoptosis in B chronic lymphocytic leukaemia (B-CLL) and induction of chromosomal damage in healthy donor B and T lymphocytes. The latter was measured by a micronucleus assay. 213Bi was eluted from a 225Ac generator and conjugated to CD20 antibody (rituximab) with CHX-A"-DTPA as a chelator. B-CLL cells from five patients were cultured for 24 h in RPMI/10% FCS while exposed to 213Bi conjugated to CD20 antibody or after external 60Co gamma irradiation. Binding assays were performed in samples of all patients to calculate the total absorbed dose. Apoptosis was scored by flow cytometric analyses of the cells stained with annexin V-FITC and 7-AAD. Apoptosis was expressed as % excess over spontaneous apoptosis in control. Full dose range experiments demonstrated 213Bi-conjugated CD20 antibody to be more effective than equivalent doses of external gamma irradiation, but showed that similar plateau values were reached at 10 Gy. The RBE for induction of apoptosis in B-CLL was 2 between 1.5 and 7 Gy. The micronucleus yield in lymphocytes of healthy volunteers was measured to assess the late toxicity caused by induction of chromosomal instability. While gamma radiation induced a steady increase in micronucleus yields in B and T cells, the damage induced by 213Bi was more dramatic, with RBE ranging from 5 to 2 between 0.1 Gy and 2 Gy respectively. In contrast to gamma irradiation, 213Bi inhibited mitogen-stimulated mitosis almost completely at 2 Gy. In conclusion, high-LET targeted alpha particle exposure killed B-CLL cells more effectively than did external gamma irradiation at a low dose (RBE=2), while a plateau was reached at a high dose. Long-term toxicity on healthy B and T lymphocytes was systematically higher for the alpha emitter (RBE=5 to 2).

Comparison of the radiotoxicity of two alpha-particle-emitting immunoconjugates, terbium-149 and bismuth-213, directed against a tumor-specific, exon 9 deleted (d9) E-cadherin adhesion protein.

We investigated the effects of the alpha-particle emitters (149)Tb and (213)Bi coupled to a tumor-specific antibody targeting the mutated delta 9 E-cadherin (d9 E-Cad) on single cells and cell pellets. The d9 mutation of the adhesion molecule E-cadherin is found in 10% of diffuse-type gastric cancers and is not expressed in normal tissue. Human breast cancer cells (MDA-MB-435S) transfected with d9 E-Cad or the wild-type E-cadherin gene were used to study the effects of anti-d9 E-Cad MAb coupled to (149)Tb and (213)Bi ((149)Tb-d9 MAb and (213)Bi-d9 MAb). The density of binding sites determined on transfected MDA tumor cells by Scatchard analysis and flow cytometry varied from 4 x 10(4) to 6 x 10(4) antigens per cell. Internalization of radioimmunoconjugates by cells expressing d9 E-Cad was less than 10% of bound antibody within 240 min. The effect of the radioimmunoconjugates on cell suspensions and cell pellets was quantified by [(3)H]thymidine incorporation, and the dose to the cell nuclei was determined using microdosimetric calculations. (149)Tb and (213)Bi immunoconjugates affected cells in suspension similarly. Significant differences in the proliferation capacity of d9 E-cadherin- and wild-type E-cadherin-expressing cells were observed at activity concentrations around 185 kBq/ml, corresponding to antibody concentrations between 200 ng/ml and 1000 ng/ml. Proliferation after incubation with (213)Bi-d9 MAb was 50% greater in pelleted wild-type E-Cad-expressing cells compared to wild-type E-Cad cells in suspension. In contrast, the proliferation of pelleted d9 E-Cad cells was similar to that of d9 E-Cad cells in suspension. For (149)Tb-d9 MAb, no significant difference was found between pelleted cells and cells in suspension for low activity concentrations. However, at high activity concentrations, (149)Tb-d9 MAb had only a small effect on pelleted cells. These in vitro studies demonstrate different effects of (149)Tb and (213)Bi conjugated to a tumor-specific antibody toward single cells and tumor cell pellets. Microdosimetric simulation of single cell survival after alpha-particle irradiation modeled the experimental results with reasonable accuracy.

IGF-I, IgA, and IgG responses to bovine colostrum supplementation during training.

This study examined the effect of bovine colostrum (Dynamic colostrum) supplementation on blood and saliva variables (study 1) and the absorption of orally administered human recombinant insulin-like growth factor (IGF)-I (rhIGF-I) labeled with 123I (123I-rhIGF-I) (study 2). In study 1, adult male and female athletes were randomly assigned in a double-blind fashion to either an experimental (Dynamic; n = 19) or a control (Placebo; n = 11) group. The former consumed daily 20 g of Dynamic supplement, and the latter 20 g of maltodextrin during a 2-wk training period. After bovine colostrum supplementation, significant increases were noticed in serum IGF-I (P < 0.01) and saliva IgA (P < 0.01) in Dynamic compared with Placebo. In study 2, gel electrophoresis was carried out in 12 adult subjects with serum samples taken 60 min after ingestion of 123I-rhIGF-I and showed peaks at 0.6 and at 40-90 kDa, with the former inducing 96% and the latter 4% of the total radioactivity. It was concluded that a long-term supplementation of bovine colostrum (Dynamic) increases serum IGF-I and saliva IgA concentration in athletes during training. Absorption data show that ingested 123I-rhIGF-I is fragmented in circulation and that no radioactive IGF-I is eluted at the positions of free, or the IGF, binding proteins, giving no support to the absorption of IGF-I from bovine colostrum.