Development of a high-performance liquid chromatographic method for the determination of a new potent radioiodinated melanoma imaging and therapeutic agent

N-(2-diethylaminoethyl)-6-iodoquinoxaline-2-carbamide (ICF 01012) is a new melanoma imaging agent showing promising properties for application in internal radionuclide therapy. We developed an analytical protocol for detection of ICF 01012 in biological samples using HPLC. The proposed method was first validated using standard of ICF 01012 and four potent metabolites of this compound and then applied to follow the metabolic fate of [(125)I]ICF 01012 after injection in melanoma-bearing mice. The results demonstrate that this method exhibits a good linearity (r(2)=0.9947), specificity and acceptable accuracy. This simple method appears convenient and sufficient for pharmacokinetic studies on [(125)I]ICF 01012.     

Regional distribution study of brain perfusion and metabolic agents in normal and tumour bearing rat brains using autoradiographic technique

Regional distribution of brain perfusion imaging agents, [¹³¹I]N,N,N′-trimethyl-N′-[2-hydroxy-3-methyl-5-iodobenzyl]1,3 propanediamine (HIPDM) and [¹³¹I]N-isopropyl-p-iodoamphetamine (IMP), was compared with the distribution of patterns of [¹⁴C]l-methionine and [¹⁴C]d-glucose in normal and tumour bearing rat brains using autoradiographic technique. There was higher concentration of the radiopharmaceutical in grey than white matter in normal rat brain. Autoradiographs of brain tumour sections showed very low uptake of [¹³¹I]HIPDM and [¹³¹I]IMP as compared to normal brain tissue. There was moderate concentration of [¹⁴C]d-glucose and avid uptake of [¹⁴C]l-methionine in tumours. Autoradiographic study is useful for evaluating distribution patterns of radiopharmaceuticals.     

ANTAGONIST AND AGONIST ACTIVITIES OF THE MOUSE AGOUTI PROTEIN FRAGMENT (91–131) AT THE MELANOCORTIN-1 RECEPTOR

Antagonist and agonist activities of chemically synthetized mouse agouti protein fragment (91–131) (AP_91–131) at the melanocortin type-1 receptor (MC1-R) were assessed using B16-F1 mouse melanoma cells in vitro and the following assay systems: (i) receptor binding, (ii) adenylate cyclase, (iii) tyrosinase, (iv) melanin production, and (v) cell proliferation. In competition binding studies AP_91–131 was about 3-fold less potent than the natural agonist α-melanocyte-stimulating hormone (α-MSH) in displacing the radioligand [¹²⁵I]-[Nle⁴, D-Phe⁷]-α-MSH (K_i 6.5±0.8 nmol/l). α-MSH-induced tyrosinase activation and melanin production were completely inhibited by a 100-fold higher concentration of AP_91–131; the IC₅₀ values for AP_91–131 in the two assay systems were 91±22 nM and 95±15 nM respectively. Basal melanin production and adenylate cyclase activity in the absence of agonist were decreased by AP_91–131 with IC₅₀ values of 9.6±1.8 nM and 5.0±2.4 nM, respectively. This indicates inverse agonist activity of AP_91–131 similar to that of native AP. The presence of 10 nM melanin-concentrating hormone (MCH) slightly potentiated the inhibitory activity of AP_91–131 in the adenylate cyclase and melanin assays. On the other hand, AP_91–131 inhibited cell growth similar to α-MSH (IC₅₀ 11.0±2.1 nM; maximal inhibition 1.8-fold higher than that of α-MSH). Furthermore, MC1-R was down-regulated by AP_91–131 with about the same potency and time-course as with α-MSH. These results demonstrate that AP_91–131 displays both agonist and antagonist activities at the MC1-R and hence that it is the cysteine-rich region of agouti protein which inhibits and mimics the different α-MSH functions, most likely by simultaneous modulation of different intracellular signalling pathways.     

Evidence for a secretion of thyroxine by isolated hog thyroid cells

Isolated thyroid cells prepared from hog thyroid glands by tryptic dispersion were incubated with ¹³¹I⁻ for 1–6 h. Free [¹³¹I]thyroxine was identified in the incubation medium by three chromatographic methods. Neither [¹³¹I]iodotyurosines nor [¹³¹I]triiodothyronine were detected. The [¹³¹I]thyroxine released in the medium by 100 μl of cells (packed cell volume) after a 6-h incubation period amounted to 1.16% (S.E. = ± 0.39) of the total radioactivity. The medium [¹³¹I]thyroxine represented 15–25% of the total [¹³¹I]thyroxine synthesized during the 6 h of incubation. Thyrotropin, 1–60 munits/ml, increased the medium [¹³¹I]thyroxine content 2–4 fold. Dibutyryl cyclic AMP mimicked the effect of thyrotropin. The amount of medium [¹³¹I]thyroxine was strictly related to the amount of incubated cells but was independent of the volume of the incubation medium. When prelabeled cells were incubated in the presence of methimazole the increase in medium [¹³¹I]thyroxine was quantitatively related to a decrease in the intracellular [¹³¹I]thyroxine. Addition of dinitrotyrosine, an inhibitor of the deiodinase activity, induced the release of iodotyrosines in the incubation medium. That the incubation supernatant of isolated thyroid cells did contain free thyroxine but no iodotyrosines suggests that the normal mechanisms of proteolysis of thyroglobulin and deiodination of iodotyrosines inside the cells are preserved. From these data, it was concluded that the thyroxine release by isolated cells represents a real secretion.     

α-MSH Receptor Autoradiography on Mouse and Human Melanoma Tissue Sections and Biopsies

Abstract

MSH receptors and their binding characteristics of [¹²⁵I]-labelled derivatives of α-MSH have been studied extensively on various mouse and human melanoma cell lines in culture. The aim of this study was to determine the binding characteristics of α-MSH radioligands to MSH receptors occurring in experimental mouse and human melanoma tumours as well as in human melanoma biopsies. For this reason, solid tumours were grown on experimental animals by inoculation of murine B16-F1 and human D10 and HBL melanoma cells. After excision and cryosectioning of the tumours, frozen tissue sections were incubated with [(¹²⁵I)Tyr²]-α-MSH or [(¹²⁵I)Tyr²,Nle⁴,D-Phe⁷]-α-MSH and specific α-MSH binding sites were visualized by subsequent autoradiography. The presence of increasing concentrations of unlabelled α-MSH during incubation with tracer led to a dose-dependent displacement of the radioligand. Quantitative analysis of the autoradiograms produced dissociation constants which were comparable with those obtained with cell binding assays: K_D = 1.87 and 1.31 nmol/l for B16 tumours and cells, respectively; 0.32 and 0.33 nmol/l for D10, and 2.24 and 1.36 nmol/l for HBL tumours and cells, respectively. This indicates similar binding properties of α-MSH radioligands to both cultured melanoma cells and tissue sections of melanoma tumours from experimental animals. Similar binding characteristics were also observed with human melanoma tissue sections originating from biopsies of melanoma patients.     

Transfectant mosaic spheroids: a new model for evaluation of tumour cell killing in targeted radiotherapy and experimental gene therapy

Background

We describe an in vitro tumour model for targeted radiotherapy and gene therapy that incorporates cell population heterogeneity.

Materials and methods

Transfectant mosaic spheroids (TMS) and transfected mosaic monolayers (TMM) are composed of two cell populations derived from a single cell line. The cells of one population were transfected with the noradrenaline transporter gene (NAT), allowing active uptake of a radiolabelled targeting agent meta‐[¹³¹I]iodobenzylguanidine ([¹³¹I]MIBG); the other population of cells was derived from the same parent line and transfected with a marker gene – green fluorescent protein (GFP). After treatment with [¹³¹I]MIBG, cell kill was determined in TMM by clonogenic assay and in TMS by clonogenic assay and spheroid growth delay.

Results

We have used the TMS model to assess the ‘radiological bystander effect’ (radiation cross‐fire) conferred by the β‐emitting radiopharmaceutical [¹³¹I] MIBG whose cellular uptake is facilitated by the transfected gene encoding NAT. We show that cell killing by [¹³¹I]MIBG in both TMS and TMM cultures increased in direct proportion to the fraction of NAT‐transfected cells and that the degree of cell killing against fraction transfected was greater in TMS, suggestive of a greater bystander effect in the three‐dimensional culture system.

Conclusions

TMS provide a useful model for assessment of the effectiveness of targeted radiotherapy in combination with gene therapy when less than 100% of the target cell population is expressing the NAT transgene. Further, this novel model offers the unique opportunity to investigate radiation‐induced bystander effects and their contribution to cell cytotoxicity in radiotherapy and other gene therapy applications. Copyright © 2002 John Wiley & Sons, Ltd.

     

Feasibility study of fluorine-18 labeled dopa for melanoma imaging

Feasibility of fluorine-18 labeled l-dopa for melanoma imaging was investigated. In B16 melanoma-bearing mice given 2-[¹⁸F]fluoro-l-dopa, the radioactivity in the B16 decreased for the first 60 min and then remained constant, while all other tissues investigated decreased with time. High tumor uptake ratios for all other tissues except for the pancreas were obtained at 120 min. 6-[¹⁸F]Fluoro-l-dopa showed a similar tissue distribution. However, the B16 uptake was about half that value for the 2-fluoro analogue. A higher incorporation rate of 2-[¹⁸F]fluoro-l-dopa into the acid-precipitable fraction of the melanoma also showed that the 2-[¹⁸F]fluoro-l-dopa was a preferable melanin precursor. Among the four kinds of non-melanoma tumors in mice or rats three tumors showed an uptake of 2-[¹⁸F]fluoro-l-dopa similar to the B16 at 60 min. However, larger melanoma-to-tissue uptake ratios were observed when compared to non-melanoma tumors.     

Intrathyroidal iodine metabolism in the rat. The influence of diet and the administration of thyroid-stimulating hormone

1. Ratios of mono[¹³¹I]iodotyrosine and di[¹³¹I]iodotyrosine (R values) and the incorporation of ¹³¹I into iodothyronines have been estimated in rat thyroid glands from 30min. to 38hr. after the administration of [¹³¹I]iodide. 2. In rats receiving a powdered low-iodine diet the R values were close to unity and did not change with time after the administration of [¹³¹I]iodide. In rats receiving a commercial pellet diet the R values fell from a mean of 0·8 at 30min. after [¹³¹I]iodide administration to 0·49 at 38hr. 3. Administration of 0·5–2·0i.u. of thyroid-stimulating hormone before giving the injection of [¹³¹I]iodide caused a small diminution in the R value when the time between injecting [¹³¹I]iodide and killing the animal was 16hr. or more. 4. Iodothyronines represented a greater percentage of the total thyroid-gland radioactivity in the iodine-deficient animals than in animals fed on the pellet diet. Thyroid-stimulating hormone had little effect, if any, on the iodothyronine contents.     

211At-Methylene Blue in Targeted Radiotherapy of Disseminated Melanoma

Targeted radiotherapy with ²¹¹At-methylene blue (²¹¹At-MTB) is a systemic treatment selectively directed at melanoma due to a high affinity of MTB to melanin synthesized in the tumor cells. Since MTB forms a strong complex with melanin, it is an effective carrier for a number of radioisotopes to be addressed to the tumor deposits of any size including individually dispersed melanoma cells. Thus, appropriately radiolabeled MTB can be used for either diagnosis or therapy of the neoplasm. As predicted and found in animal experiments, ²¹¹At-MTB is most effective therapeutically. Histopathological investigations showed that the highly pigmented ²¹¹At-MTB-treated tumors were characterized initially by perivascular oedema and hydropic degeneration of tumor cells followed by gradual development of extensive areas of coagulative necrosis. The necrotic tumor areas contained microvessels occluded by thrombi and tended to undergo microfocal calcification. Although melanoma-bearing animals successfully treated with ²¹¹At-MTB did not reveal any adverse effects of the therapy, detailed toxicological studies were undertaken. No serious macro- or microscopic lesions were observed in normal organs of ²¹¹At-MTB treated mice. Only the relative number of small lymphocytes in the groin lymph nodes in a minority of animals was variably reduced, most often in conjunction with the treatment of highly, but not poorly, pigmented tumors.     

Synthesis and biological evaluation of radioiodinated 2NUBTA as a cerebral ischemia marker

N-[4-(Benzothiazol-2-yl)phenyl]-11-(2-nitroimidazole-1-yl)undecanamide (2NUBTA) was synthesized and radiolabeled with iodine-131. In vitro evaluation of the [¹³¹I]2NUBTA using murine sarcoma S180 cells showed increase in radioactivity in hypoxic cells up to 4 h, while it was not in aerobic cells. Its potential as a cerebral ischemia marker was evaluated using gerbil stroke models that had been subjected to right common carotid artery ligation to produce cerebral ischemia. The uptake in the right cerebral hemisphere decreased slowly than that of the left and the right/left hemisphere uptake ratios increased with time going on. It indicated that [¹³¹I]2NUBTA might be a possible cerebral ischemia marker.     

Activation of Tyrosinase Reduces the Cytotoxic Effects of the Superoxide Anion in B16 Mouse Melanoma Cells

Tyrosinase may protect against oxidative stress by using the superoxide anion (O^?₂) in the production of melanin. We have examined this by comparing its cytotoxic effects in B16/F10 and B16/F10-differential deficient (-DD) mouse melanoma cells that express high and low levels of tyrosinase activity respectively. Xanthine oxidase (XO) was used to generate O^?₂ and cytotoxicity assessed by measuring cell survival. XO increased O^?₂ concentrations and 3 h later dose related decreases in cell survival were seen. F10 cells were more resistant to these cytotoxic effects than the F10-DD cells. [Nle⁴,DPhe⁷]MSH increased tyrosinase activity and melanin content, reduced O^?₂ concentration and increased the resistance of F10 cells to the cytotoxic effects of O^?₂. No such effects were seen in F10-DD cells. The effect of [Nle⁴,DPhe⁷]MSH on the resistance of the F10 cells was time-dependent and noticeable when tyrosinase activity but not melanin was increased. This suggests that it was the activation of tyrosinase rather than the increase in the melanin that provided the protection against O^?₂. In support of this, inhibition of tyrosinase with phenylthiocarbamide reduced the increased resistance induced by [Nle⁴,DPhe⁷]MSH. Moreover, although melanin was capable of scavenging O^?₂ it had little effect at concentrations comparable to those in the activated F10 cells. XO also increased the melanin content of F10 but not F10-DD cells. We conclude that tyrosinase is able to utilise O^?₂ to produce melanin and this provides pigment cells with a unique anti-oxidant mechanism.     

[D‐(p‐Benzoylphenylalanine)13, tyrosine19]‐melanin‐concentrating hormone,a potent analogue for MCH receptor crosslinking

A photoreactive analogue of human melanin‐concentrating hormone was designed, [d‐ Bpa¹³,Tyr¹⁹]‐MCH, containing the d‐ enantiomer of photolabile p‐benzoylphenylalanine (Bpa) in position 13 and tyrosine for radioiodination in position 19. The linear peptide was synthesized by the continuous‐flow solid‐ phase methodology using Fmoc‐strategy and PEG‐PS resins, purified to homogeneity and cyclized by iodine oxidation. Radioiodination of [d ‐Bpa¹³,Tyr¹⁹]‐MCH at its Tyr¹⁹ residue was carried out enzymatically using solid‐ phase bound glucose oxidase/lactoperoxidase, followed by purification on a reversed‐ phase mini‐column and HPLC. Saturation binding analysis of [¹²⁵I]‐[d‐ Bpa¹³,Tyr¹⁹]‐MCH with G4F‐7 mouse melanoma cells gave a K_D of 2.2±0.2×10⁻¹⁰ mol/l and a B_max of 1047±50 receptors/cell. Competition binding analysis showed that MCH and rANF(1–28) displace [¹²⁵I]‐[d‐ Bpa¹³,Tyr¹⁹]‐MCH from the MCH binding sites on G4F‐7 cells whereas α‐MSH has no effect. Receptor crosslinking by UV‐irradiation of G4F‐7 cells in the presence of [¹²⁵I]‐[d‐ Bpa¹³,Tyr¹⁹]‐MCH followed by SDS‐polyacrylamide gel electrophoresis and autoradiography yielded a band of 45–50 kDa. Identical crosslinked bands were also detected in B16‐F1 and G4F mouse melanoma cells, in RE and D10 human melanoma cells as well as in COS‐7 cells. Weak staining was found in rat PC12 phaeochromocytoma and Chinese hamster ovary cells. No crosslinking was detected in human MP fibroblasts. These data demonstrate that [¹²⁵I]‐[d‐ Bpa¹³,Tyr¹⁹]‐MCH is a versatile photocrosslinking analogue of MCH suitable to identify MCH receptors in different cells and tissues; the MCH receptor in these cells appears to have the size of a G protein‐coupled receptor, most likely with a varying degree of glycosylation. Copyright © 1999 European Peptide Society and John Wiley & Sons, Ltd.     

INTERACTION OF MELANIN-CONCENTRATING HORMONE (MCH), NEUROPEPTIDE E-I (NEI), NEUROPEPTIDE G-E (NGE), AND α-MSH WITH MELANOCORTIN AND MCH RECEPTORS ON MOUSE B16 MELANOMA CELLS

Melanin-concentrating hormone (MCH) and α-melanocyte-stimulating hormone (α-MSH) are known to exhibit mostly functionally antagonistic, but in some cases agonistic activities, e.g., in pigment cells and in the brain. Neuropeptide E-I (NEI) displays functional MCH-antagonist and MSH-agonist activity in different behavioral paradigms; the role of neuropeptide G-E (NGE) is not known. This study addressed the question of possible molecular interactions between α-MSH, MCH and the MCH-precursor-derived peptides NEI and NGE at the level of the pigment cell MCH receptor subtype (MCH-R_pc) and the different melanocortin (MC) receptors. Radioreceptor assays using [¹²⁵I]MCH, [¹²⁵I]α-MSH and [¹²⁵I]NEI as radioligands and bioassays were performed with MC1-R-positive and MC1-R-negative mouse B16 melanoma cells and with COS cells expressing the different MC receptors. The IC₅₀s of α-MSH and NEI or NGE for [¹²⁵I]MCH displacement from mouse MCH-R_pc were 80-fold and, respectively, > 300-fold higher than that of MCH, and the IC₅₀s for MCH and NEI or NGE for [¹²⁵I]α-MSH displacement from mouse MC1-R were 50,000-fold and > 200,000-fold higher than that of α-MSH. No high-affinity binding sites for NEI were detected on B16 melanoma cells and there was no significant displacement of [¹²⁵I]α-MSH by MCH, NEI or NGE with MC3-R, MC4-R and MC5-R expressed in COS cells. At concentrations of 100 nM to 10 μM, however, MCH, NEI and NGE induced cAMP formation and melanin synthesis which could be blocked by agouti protein or inhibitors of adenylate cyclase or protein kinase A. This shows that mammalian MCH-precursor-derived peptides may mimic MSH signalling via MC1-R activation at relatively high, but physiologically still relevant concentrations, as e.g. found in autocrine/paracrine signalling mechanisms.     

Labeling proteins using aryl iodide acylation agents: Influence of meta vs para substitution on in vivo stability

The effect of para vs meta substitution on the biological behavior of an intact antibody and an F(ab′)₂ fragment was investigated. Paired-label studies were performed using 81C6 IgG and OC 125 F(ab′)₂ labeled using the N-succinimidyl esters of both p-[¹²⁵I]- and m-[¹³¹I]iodobenzoate as well as with the potential catabolites, p-[¹²⁵I]- and m-[¹³¹I]iodobenzoic acid. In all 3 studies, up to 55% lower uptake of ¹³¹I in thyroid and stomach was observed, suggesting that the m-substituted species were more inert to dehalogenation in vivo.     

4-Borono-2-[18F]fluoro-d,l-phenylalanine: a possible tracer for melanoma diagnosis with PET

The potential of 4-borono-2-[¹⁸F]fluoro-d,l-phenylalanine ([¹⁸F]FBPA), a fluorinated derivative of a target compound for boron neutron capture therapy, for melanoma imaging by positron emission tomography (PET) was studied using animal models. A high uptake of [¹⁸F]FBPA was found in murine B16 melanoma or in Greene's melanoma No. 179, a melanotic cell line in hamsters, for the first 6 h after injection. Whole body autoradiography using [¹⁸F]FBPA gave a clear image of the B16 tumor. The acid-insoluble ¹⁸F in the B16 increased to 27% by 6h, and most of the free ¹⁸F was detected as [¹⁸F]FBPA in both B16 and plasma. In the hamster models, No. 179 showed a 1.7 times higher uptake than amelanotic Greene's melanoma No. 178 at 6 h post-injection, although both melanomas indicated similar metabolic activities when examined by a tracer uptake study using l-[¹⁴C]methionine, 2-deoxy-d-[¹⁴C]glucose and [³H]thymidine. [¹⁸F]FBPA may be a very promising PET tracer for melanoma imaging.     

Influence of starvation,Triton WR-1339 and [131I]-human serum albumin on rat liver lysosomes

The response of rat liver lysosomes to starvation and administration of lysosomotropic agentsviz. Triton WR-1339 and [¹³¹I]-human serum albumin, was assessed in terms of their distribution pattern after isopycnic sucrose density gradient centrifugation. Starvation induced changes in lysosomes appeared to be similar to that produced by the detergent uptake. Both the treatments caused a distinct decline in the equilibration densities of the organelles. On the other hand, injected labelled protein failed to comigrate with the lysosomal markers in starved as well as Triton treated rats and conspicuously remained in a region of high specific gravity in the gradient. These findings indicate retarded fusion between secondary lysosomes and [¹³¹I]-human serum albumin containing phagosomes in the livers of rats subjected to starvation or detergent treatment     

Synthesis and bioevaluation of radioiodinated nitroimidazole hypoxia imaging agents by one-pot click reaction

Eight radioiodinated 2-nitroimidazole derivatives for use as hypoxia imaging agents were synthesized by one-pot click reaction using four azides, two alkynes, and [¹³¹I]iodide ions and evaluated by hypoxic cellular uptake and biodistribution experiments. The results suggested that radiotracers with suitable partition coefficients (log P: −0.2–1.2) were more likely to have higher hypoxic cellular uptake. Among these eight molecules, [¹³¹I]15 ([¹³¹I]-(5-iodo-1-(2-(2-(2-nitro-1H-imidazol-1-yl)ethoxy)ethyl)-4-((2-nitro-1H-imidazol-1-yl)methyl)-1H-1,2,3-triazole)) had a suitable log P (0.05 ± 0.03) and contained two 2-nitroimidazole groups. The hypoxic/aerobic cellular uptake ratio of [¹³¹I]15 was 4.4 ± 0.5, and the tumor/blood (T/B) and tumor/muscle (T/M) ratios were 2.03 ± 0.45 and 6.82 ± 1.70, respectively. These results suggested that [¹³¹I]15 was a potential hypoxia imaging agent.     

Antagonist and agonist activities of the mouse agouti protein fragment (91-131) at the melanocortin-1 receptor.

Antagonist and agonist activities of chemically synthetized mouse agouti protein fragment (91-131) (AP91-131) at the melanocortin type-1 receptor (MC1-R) were assessed using B 16-F1 mouse melanoma cells in vitro and the following assay systems: (i) receptor binding, (ii) adenylate cyclase, (iii) tyrosinase, (iv) melanin production, and (v) cell proliferation. In competition binding studies AP91-131 was about 3-fold less potent than the natural agonist alpha-melanocyte-stimulating hormone (alpha-MSH) in displacing the radioligand [125I]-[Nle4, D-Phe7]-alpha-MSH (Ki 6.5 +/- 0.8 nmol/l). Alpha-MSH-induced tyrosinase activation and melanin production were completely inhibited by a 100-fold higher concentration of AP9 l -131; the IC50 values for AP91-131 in thetwo assay systems were 91 +/- 22 nM and 95 +/- 15 nM respectively. Basal melanin production and adenylate cyclase activity in the absence of agonist were decreased by AP91-131 with IC50 values of 9.6+/-1.8 nM and 5.0+/-2.4 nM, respectively. This indicates inverse agonist activity of AP91-131 similar to that of native AP. The presence of 10 nM melanin-concentrating hormone (MCH) slightly potentiated the inhibitory activity of AP91-131 in the adenylate cyclase and melanin assays. On the other hand, AP91-131 inhibited cell growth similar to alpha-MSH (IC50 11.0 +/- 2.1 nM; maximal inhibition 1.8-fold higher than that of alpha-MSH). Furthermore, MC1-R was down-regulated by AP91-131 with about the same potency and time-course as with alpha-MSH. These results demonstrate that AP91-131 displays both agonist and antagonist activities at the MC1-R and hence that it is the cysteine-rich region of agouti protein which inhibits and mimics the different alpha-MSH functions, most likely by simultaneous modulation of different intracellular signalling pathways.     

Improved synthesis of 17β-hydroxy-16α-iodo-wortmannin, 17β-hydroxy-16α-iodoPX866, and the [131I] analogue as useful PET tracers for PI3-kinase

An improved method for the synthesis of 17β-hydroxy-16α-iodo-wortmannin along with the first synthesis of 17β-hydroxy-16α-iodoPX866 and [¹³¹I] radiolabeled 17β-hydroxy-16α-[¹³¹I]iodo-wortmannin, as potential PET tracers for PI3K was also described. The differences between wortmannin and its iodo analogue were compared by covalently docking each structure to L833 in PI3K.     

Micronucleus formation in lymphocytes of children from the vicinity of Chernobyl after <Superscript>131</Superscript>I therapy

After the Chernobyl accident a statistically significant increase in the number of children with thyroid tumours was observed. In this study 166 children with and 75 without thyroid tumours were analysed for micronucleus formation in peripheral blood lymphocytes using the cytochalasin B approach. The following factors did not significantly affect micronucleus formation: gender, age at the time of the first ¹³¹I treatment, tumour stage, tumour type, or metastases; a statistically significant increase in the number of micronuclei, however, was observed for the residents of Gomel compared to other locations, such as Brest, Grodno, and Minsk. The children with tumours received ¹³¹I treatment after surgical resection of the tumours. This gave us the opportunity to systematically follow the effect of ¹³¹I on micronucleus formation. A marked increase was observed 5 days after the ¹³¹I treatment followed by a decrease within a 4–7 months interval up to the next application, but the pre-treatment levels were not achieved. Up to 10 therapy cycles were followed each including an analysis of micronucleus formation before and 5 days after ¹³¹I application. The response of the children was characterised by clear individual differences and the increase/decrease pattern of micronucleus frequencies induced by iodine-131 was correlated with a decrease/increase pattern in the number of lymphocytes.