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PubMed1990

Steps towards cancer therapy with radionuclides--a review including radiation biophysical aspects.

Though great advantages will be connected with endoradiotherapy, a lot of problems has still to be overcome, the greatest of them being without doubt the problem of selectivity of the carrier compounds. Some few of them have proved to be able to accumulate in certain cancers by reason of their incorporation as metabolites, especially in melanomas. The other great hope are the monoclonal antibodies or their fragments, and in this field much endeavour has been spent in the last years. Especially the two-step method of loading the radioactive nuclide to the antibodies when their binding to the cancer cells is complete appears very promising. Some other, unspecific vehicles may also prove suitable for accumulation in certain tumor types. For the selection of the nuclides it has to be considered that radiation biophysical experiments demonstrated that the critical targets for radiation action are with high probability the DNA superstructure units, and that the distribution of ionizations within them is decisive for the inactivation of a cell. With sparsely ionizing radiation (e.g. beta-radiation) rather high doses are required for reaching an adequate concentration of ionizations in these DNA units. Densely ionizing radiation with an LET of about 150 keV/microns exhibits the maximum relative biological effectiveness (12-16 referred to X-radiation). Therefore emitters of alpha-particles the LET of which lies actually somewhat lower, near 100 keV/microns, seem to be very suitable for endoradiotherapy. Moreover the short ranges of these particles (about 60 microns in tissue) render an extensive sparing of the surrounding normal tissue possible. The second group of effective nuclides is that of Auger electron emitters. The low-energy proportion of Auger electrons leads to a high ionization density in small volumes. The very short ranges of these electrons (in the nanometer range), however, require an incorporation of the nuclide into the cell nucleus if an effective cell inactivation is to occur. 211At (alpha-emitter) and 125I (Auger electron emitter) already proved their high inactivating effectiveness in cell cultures and their curative action in animal experiments, and studies of binding 211At to monoclonal antibodies are encouraging. Some other approaches proposed for the transport of radionuclides into tumor cells or for generating them within tumor tissue are also aimed in essential at the release of densely ionizing alpha-particles or of Auger electrons.

Animals↗
PubMed1998

Characterization and localization of thromboxane A2 receptor in human and guinea-pig nasal mucosa using radiolabelled (+)-S-145.

1. TxA2 receptor (TP-receptor) antagonists such as S-1452 and Bay u 3405 have been shown to be effective in alleviating nasal blockage in patients with allergic rhinitis as well as guinea-pig allergic rhinitis models. The present study was conducted to examine the existence and localization of the TP-receptor in human and guinea-pig nasal mucosa by in vitro receptor binding autoradiography using radiolabelled (+)-S-145, which is a potent and specific TP-receptor antagonist with an extremely slow dissociation rate. 2. We ascertained the binding specificity of [3H]-(+ )-S-145 in human and guinea-pig platelet membranes by comparing the ability of four TP-receptor ligands of U-46619, (+)-S-145, I-(+)-S-145 and Bay u 3405 to displace the specific binding of [3H]-(+)-S-145 and [3H]-U-46619. The rank order of potency (Ki) for the displacement was correlated highly with that determined from [3H]-U-46619 binding to the same preparations. 3. Quantitative autoradiography using a radioluminographic imaging plate system, in which the radioactivity of [3H]-(+)-S-145 is expressed as photostimulated luminescence (PSL) per area (mm2), revealed that specific binding of [3H]-(+)-S-145 to human and guinea-pig nasal mucosa was saturable. Scatchard analysis showed about three fold higher affinity and two fold greater maximal binding to the nasal mucosa of humans than that of guinea-pigs: the KD and Bmax values in human mucosa were 2.82+/-0.35 nM and 6.47+/-0.33 PSL mm(-2) and those in guinea-pig mucosa were 8.23+/-1.93 nM and 3.37+/-0.66 PSL mm(-2), respectively. 4. Specific [3H]-(+)-S-145 binding to cryostat sections of human and guinea-pig nasal mucosa was displaced by another TP-receptor antagonist, Bay u 3405, and a TP-receptor agonist, U-46619. The order of potency (Ki value: nM) was (+)-S-145 (2.5) > Bay u 3405 (15.4) > > U-46619 (359.6) in human nasal mucosa and (+)-S-145 (22.8) > U-46619 (49.8) approximately Bay u 3405 (62.1) in guinea-pig nasal mucosa. These rank orders showed rather good correlation with those obtained for the respective platelet membranes. 5. Autoradiographs of human nasal mucosa demonstrated that specific [125I]-(+)-S-145 binding sites mainly exist on the smooth muscle layers of venous sinusoids and arterioles in the lamina propria, with few or no binding sites in the epithelium and nasal gland. 6. We concluded that radiolabelled (+)-S-145 can be used as a TP-receptor ligand for autoradiographic study, and that the TP-receptor is exclusively located on smooth muscle layers of venous sinusoids and arterioles in the nasal mucosa. The potent vasoconstrictive activity of TxA2 may cause reduction of local blood flow followed by mucosal oedema probably through mechanisms of vascular injury such as ischaemia-reperfusion.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2000

Induction of DNA single-strand breaks by 131I and 99mTc in human mononuclear blood cells in vitro and extrapolation to the in vivo situation.

The radionuclides (131)I and (99m)Tc are frequently used for therapy of benign and malignant thyroid disease ((131)I) and for diagnosis of thyroid and other diseases ((99m)Tc). However, the levels of DNA single-strand breaks (SSBs) induced in cells of patients after administration of (131)I and (99m)Tc are not known. In this study, we measured the number of SSBs per cell induced by (131)I and (99m)Tc in vitro, extrapolated the results to the clinical situation, and assessed their biological relevance by comparing levels of SSBs induced after therapeutic administration of (131)I and (99m)Tc to those induced by endogenous processes or by occupational exposure to genotoxic substances. A linear dose-response relationship between the radioactivity concentrations of (131)I and (99m)Tc and SSBs in human mononuclear blood cells (determined by alkaline elution) was obtained after incubation at 4 and 37 degrees C. At 4 degrees C, where almost no repair of SSBs takes place, (131)I and (99m)Tc induced 81 and 7 SSBs per cell per hour/(MBq/ml), respectively. At 37 degrees C, only 20 and 1.6 SSBs per cell per hour/(MBq/ml) were observed after incubation with (131)I and (99m)Tc. To estimate the induction of SSBs in vivo in cells of patients after administration of 3700 MBq (131)I (oral) or 60 MBq (99m)Tc (i.v.), the rates of induction of SSBs obtained in vitro were extrapolated to the concentrations of (131)I and (99m)Tc measured in blood of patients. The total number of SSBs (mean +/- standard deviation) accumulated after oral administration of 3700 MBq (131)I up to 70 h after administration was calculated as 200 +/- 59 SSBs/cell. After administration of 60 MBq (99m)Tc (i.v.), 0.032 +/- 0.009 SSBs per cell (total SSBs up to 2 h after administration) were cumulated. The induction of SSBs by endogenous processes (estimated 2,000 SSBs per cell per hour) and by occupational exposure to genotoxic substances (125-430 SSBs per cell) has been estimated in earlier studies. In conclusion, the frequency of SSBs induced by thyroid diagnosis with 60 MBq (99m)Tc is approximately 5 orders of magnitude smaller than the frequency of spontaneous SSBs and thus is most probably without biological relevance. Since the frequency of induction of SSBs by therapy with (131)I (3700 MBq) is about 6000-fold higher compared to thyroid diagnosis by (99m)Tc, its biological relevance is more difficult to assess. Nevertheless, the number of SSBs induced by therapy with (131)I is substantially lower than that induced by endogenous processes.

DNA Damage↗
PubMed2002

Value of continuous leakage monitoring with radioactive iodine-131-labeled human serum albumin during hyperthermic isolated limb perfusion with tumor necrosis factor-alpha and melphalan.

BACKGROUND: The aim of this study was to analyze the value of continuous leakage monitoring with radioactive iodine-131-labeled human serum albumin (RISA) in patients treated with hyperthermic isolated limb perfusion with tumor necrosis factor-alpha (TNF alpha) and melphalan. METHODS: Forty-eight patients with melanoma (n = 14) or soft tissue sarcoma (n = 34) of an extremity underwent 51 perfusions. Perfusion was performed at the iliac level in 22 cases, at the popliteal level in 16 cases, at the femoral level in 7 cases, and at the axillary level in 6 cases. Leakage rates and perfusion circuit and systemic levels of TNF alpha, interleukin-6, and C-reactive protein were determined, as were systemic hematological and metabolic profiles and tumor response. RESULTS: The mean isotopically measured leakage was 2.9%. Systemic leakage was < or = 2% in 28 perfusions and >2% in 23 perfusions. The correlation between the maximal monitored leakage and maximal systemic TNF alpha levels was.7114. The area under the curve for TNF alpha in the perfusion circuit, indicating the exposure of the perfused limb to TNF alpha, was 18.7% lower in the >2% leakage group. No significant differences in tumor response were found between groups. The area under the curve for systemic TNF alpha, indicating the exposure of the patient to TNF alpha, was 18.1 times higher in the >2% leakage group, resulting in a significant decrease in leukocyte and platelet count, hyperbilirubinemia, hypocholesterolemia, and proteinemia. No beneficial effect of the systemically leaked TNF and melphalan was seen on the occurrence of distant metastasis during follow-up. There was a significant difference between perfusions performed at the iliac and femoral levels compared with leakage values at the popliteal level. CONCLUSIONS: A good correlation between RISA leakage measurement and TNF alpha exposure during and after hyperthermic isolated limb perfusion with TNF alpha and melphalan was demonstrated. RISA leakage measurement serves as a good guide for the effectiveness of isolation during perfusion. If leakage exceeds the 2% limit during perfusion, less exposure of the tumor-bearing limb to TNF alpha, increased exposure of the patient systemic circulation to TNF alpha, and more systemic side effects can be expected.

Adult↗
PubMed2004

Technetium-99m labeled 1-(4-fluorobenzyl)-4-(2-mercapto-2-methyl-4-azapentyl)-4-(2-mercapto-2-methylpropylamino)-piperidine and iodine-123 metaiodobenzylguanidine for studying cardiac adrenergic function: a comparison of the uptake characteristics in vascular smooth muscle cells and neonatal cardiac myocytes, and an investigation in rats.

In developing technetium-99m-based radioligands for in vivo studies of cardiac adrenergic neurons, we compared the uptake characteristics of the (99m)Tc-labeled 1-(4-fluorobenzyl)-4-(2-mercapto-2-methyl-4-azapentyl)-4-(2-mercapto-2-methylpropylamino)-piperidine ((99m)Tc-FBPBAT) with those of the clinically established meta-[(123)I]iodobenzylguanidine ((123)I-MIBG) in rat vascular smooth muscle cells and neonatal cardiac myocytes. Furthermore, the cardiac and extracardiac uptake of both radiopharmaceuticals was assessed in intact rats and in rats pretreated with various alpha- and beta-adrenoceptor drugs, and adrenergic reuptake blocking agents. The uptake of (99m)Tc-FBPBAT and (123)I-MIBG into vascular smooth muscle cells and neonatal cardiac myocytes was rapid; more than 85% of the radioactivity accumulation into the cells occurring within the first 3 minutes. Radioactivity uptake after a 60-minute incubation at 37 degrees C (pH 7.4) varied from 15% to 65% of the total loaded activity per million cells. In all cases, (99m)Tc-FBPBAT showed the higher uptake, relative to (123)I-MIBG, at any given cell concentration. The cellular uptake of (99m)Tc-FBPBAT was lower at 4 degrees C and 20 degrees C than at 37 degrees C. In contrast, the (123)I-MIBG uptake was only slightly temperature dependent. Inhibition experiments confirmed that the cellular uptake of (123)I-MIBG is mediated by the uptake-I carrier, whereas alpha(1)- and beta(1)-adrenoceptors were predominantly involved in the uptake of (99m)Tc-FBPBAT into the cardiovascular tissues. Biodistribution studies in rats showed that (99m)Tc-FBPBAT accumulated in myocardium after intravenous injection. Radioactivity in rat heart amounted to 2.32% and 1.91% of the injected dose per gram at 15 and 60 minutes postinjection, compared with 3.10% and 2.21% injected dose per gram of tissue (%ID/g) in the experiment with (123)I-MIBG, respectively. Prazosin, urapidil, and metoprolol were as effective as treatment with other adrenergic drugs in lowering cardiac uptake of (99m)Tc-FBPBAT. Uptake reduction was more pronounced in myocardium than in other adrenergic-rich organs, including the lung, spleen, kidney, and adrenals, suggesting that the (99m)Tc-FBPBAT uptake in myocardium specifically reflects a high degree of alpha(1)/beta(1)-receptor binding to cardiac adrenergic neurons. In comparison, reduction of cardiac and pulmonary uptake of (123)I-MIBG was effective after pretreatment of rats with desipramine and reserpine, confirming distinct neuronal binding sites for (99m)Tc-FBPBAT and (123)I-MIBG. (99m)Tc-FBPBAT was excreted via urine and to a lower degree via feces. Urine analysis 6 hours p.i. revealed that more than 40% of the total excreted radioactivity was unmetabolized (99m)Tc-FBPBAT. In conclusion, the uptake of (99m)Tc-FBPBAT in rat myocardium specifically reflects binding to cardiac adrenergic neurons. The (99m)Tc-FBPBAT uptake appears to be predominantly mediated via the alpha(1)/beta(1)-adrenoceptor pathway. These data indicate that (99m)Tc-FBPBAT, like (123)I-MIBG, may be suitable for mapping cardiac adrenergic innervation by SPET, especially for alpha(1)/beta(1)-adrenoceptors as target in numerous heart diseases.

3-Iodobenzylguanidine↗