AAZTA5-squaramide ester competing with DOTA-, DTPA- and CHX-A″-DTPA-analogues: Promising tool for 177Lu-labeling of monoclonal antibodies under mild conditions

BACKGROUND

Combining the advantages of both cyclic and acyclic chelator systems, AAZTA (1,4-bis(carboxymethyl)-6-[bis(carboxymethyl)]amino-6-methylperhydro-1,4-diazepine) is well suited for complexation of various diagnostic and therapeutic radiometals such as gallium-68, scandium-44 and lutetium-177 under mild conditions. Due to its specificity for primary amines and pH dependent binding properties, squaric acid (SA) represents an excellent tool for selective coupling of the appropriate chelator to different target vectors. Therefore, the aim of this study was to evaluate radiolabeling properties of the novel bifunctional AAZTA⁵-SA being coupled to a model antibody (bevacizumab) in comparison to DOTA-SA, DTPA-p-Bn-SA and CHX-A″-DTPA-p-Bn-SA using the therapeutic nuclide lutetium-177.

METHODS AND RESULTS

As proof-of-concept, bevacizumab was first functionalized with AAZTA⁵-SA, DOTA-SA, DTPA-p-Bn-SA or CHX-A″-DTPA-p-Bn-SA. After purification via fractionated size exclusion chromatography (SEC), the corresponding immunoconjugates were subsequently radiolabeled with lutetium-177 at pH 7 and room temperature (RT) as well as 37 °C. After 90 min, labeling of AAZTA⁵-SA-mAb resulted in almost quantitative radiochemical yields (RCY) of >98% and >99%, respectively. Formation of [¹⁷⁷Lu]Lu-DTPA-p-Bn-SA-mAb indicated rapid labeling kinetics reaching similar yields at RT already after 30 min. Fast but incomplete radiolabeling of the CHX-A″-analogue could be observed with a yield of 74% after 10 min and no further significant increase. In contrast, ¹⁷⁷Lu-labeling of DOTA-SA-mAb showed negligible radiochemical yields of <2% both at room temperature and 37 °C. In vitro complex stability measurements of [¹⁷⁷Lu]Lu-AAZTA⁵-SA-mAb at 37 °C indicated >94% protein bound activity in human serum and >92% in phosphate buffered saline (PBS), respectively within 15 days. [¹⁷⁷Lu]Lu-DTPA-p-Bn-SA-mAb and [¹⁷⁷Lu]Lu-CHX-A″-DTPA-p-Bn-SA-mAb revealed similar to even slightly higher in vitro stability in both media.

CONCLUSION

Coupling of AAZTA⁵-SA to the monoclonal antibody bevacizumab allowed for ¹⁷⁷Lu-labeling with almost quantitative radiochemical yields both at room temperature and 37 °C. Within 15 days, the resulting radioconjugate indicated very high in vitro complex stability both in human serum and PBS. Therefore, AAZTA⁵-SA is a promising tool for ¹⁷⁷Lu-labeling of sensitive biomolecules such as antibodies for theranostic applications.

Effect of Iron Source and Medium pH on Growth and Development of Sorbus commixta In Vitro

Sorbus commixta is a valuable hardwood plant with a high economical value for its medicinal and ornamental qualities. The aim of this work was to investigate the effects of the iron (Fe) source and medium pH on the growth and development of S. commixta in vitro. The Fe sources used, including non-chelated iron sulfate (FeSO₄), iron ethylenediaminetetraacetic acid (Fe-EDTA), and iron diethylenetriaminepentaacetic acid (Fe-DTPA), were supplemented to the Multipurpose medium with a final Fe concentration of 2.78 mg·L^-1. The medium without any supplementary Fe was used as the control. The pH of the agar-solidified medium was adjusted to either 4.70, 5.70, or 6.70. The experiment was conducted in a culture room for six weeks with 25 °C day and night temperatures, and a 16-h photoperiod with a light intensity of 50 mmol·m^-2·s^-1 photosynthetic photon flux density (PPFD). Both the Fe source and pH affected the growth and development of the micropropagated plants in vitro. The leaves were greener in the pH 4.70 and 5.70 treatments. The tissue Fe content decreased with the increase of the medium pH. The leaf chlorophyll content was similar between plants treated with FeSO₄ and those with Fe-EDTA. The numbers of the shoots and roots of plantlets treated with FeSO₄ were 2.5 and 2 times greater than those of the control, respectively. The fresh and dry weights of the shoot and the root were the greatest for plants treated with Fe-EDTA combined with pH 5.70. The calcium, magnesium, and manganese contents in the plantlets increased in the pH 5.70 treatments regardless of the Fe source. Supplementary Fe decreased the activity of ferric chelate reductase. Overall, although the plantlets absorbed more Fe at pH 4.70, Fe-EDTA combined with pH 5.70 was found to be the best for the growth and development of S. commixta in vitro.

Indium-111-DTPA-octreotide Scintigraphy Modulation by Treatment with Unlabelled Somatostatin Analogue in Smali-Cell Lung Cancer

Aims and background

Small-cell lung cancer (SCLC) tissue expresses somatostatin receptors and can be visualized by means of the indium-111-labelled somatostatin analogue DTPA-D-Pheoctreotide. The aim of the study was to investigate whether treatment with a cold somatostatin analogue can affect the imaging of somatostatin receptor scintigraphy.

Methods

Three patients with SCLC were treated with 200 μg of cold octreotide three times a day subcutaneously for 7 days. Whole body and planar scintigraphy was performed before and after the treatment.

Results

111In-DTPA-octreotide uptake was increased in cancer lesions, whereas fixation in normal tissues (liver, spleen, kidneys) decreased.

Conclusions

This is the first demonstration of an enhancement of SCLC imaging following unlabelled somatostatin analogue administration. Similar results have been described by other authors in a limited number of carcinoid tumors.

Lanthanoid tagging via an unnatural amino acid for protein structure characterization

Lanthanoid pseudo-contact shift (PCS) provides long-range structural information between a paramagnetic tag and protein nuclei. However, for proteins with native cysteines, site-specific attachment may only utilize functional groups orthogonal to sulfhydryl chemistry. Here we report two lanthanoid probes, DTTA-C3-yne and DTTA-C4-yne, which can be conjugated to an unnatural amino acid pAzF in the target protein via azide-alkyne cycloaddition. Demonstrated with ubiquitin and cysteine-containing enzyme EIIB, we show that large PCSs of distinct profiles can be generated for each tag/lanthanoid combination. The DTTA-based lanthanoid tags are associated with large magnetic susceptibility tensors owing to the rigidity of the tags. In particular, introduction of the DTTA-C3 tag affords intermolecular PCSs and enables structural characterization of a transient protein complex between ubiquitin and a UBA domain. Together, we have expanded the repertoire of paramagnetic tags and the applicability of paramagnetic NMR.

Enhancements in hepatobiliary imaging: the spectrum of gadolinium-ethoxybenzyl diethylenetriaminepentaacetic acid usages in hepatobiliary magnetic resonance imaging

Gadolinium-ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) is a unique hepatocyte-specific contrast agent approved for clinical use in the United States in 2008. Gd-EOB-DTPA-enhanced MR has shown to improve detection and characterization of hepatic lesions. Gd-EOB-DTPA is now being routinely used in daily clinical practice worldwide. Therefore, it is important for radiologists to be familiar with the potential uses and pitfalls of Gd-EOB-DTPA, which extends beyond the assessment of focal hepatic lesions. The purpose of this article is to review the various usages of Gd-EOB-DTPA in hepatobiliary MR imaging.

Contrast-enhanced MR imaging of experimental acute tubular necrosis

Purpose: To demonstrate the involvement of the various renal structures in acute tubular necrosis (ATN).

Material and Methods: In 15 rats, using a T1-/T2-weighted sequence, either gadodiamide alone, or gadodiamide in combination with sprodiamide (a susceptibility agent) were used to enhance the various anatomical substrates of the kidney. The results were compared to those of pathological verification.

Results: Experimentally induced ATN of the rat kidney causes profound changes in the medulla, leaving the cortex largely intact. The difference between the normal cortex and the partially necrotic outer medulla, on the one hand, and the papillary region, was significantly enhanced with the combination, whereas a larger region composed of the inner and outer medulla was enhanced after the gadolinium chelate alone.

Conclusion: The results varied considerably between the two procedures; the double contrast demonstrated a clear difference between the inner and outer medulla, and the gadolinium chelate alone demonstrated a clear difference between the medulla and the cortex. These results demonstrated a clear difference in the compartmentalization between the inner and outer medullary regions, providing complementary information about the pathological condition of the kidney.

[Functionalized Metal Chelates Based on Diethylenetriaminetetraacetic Acids for Chemical Modification of Proteins and Small Biomolecules]

Bifunctional reagents based on diethylenetriaminetetraacetic acid containing a bound metal ion and a reactive functional group for the interaction with proteins and low-molecular-weight substances have been synthesized. An Amino-derivative of a complexonate was obtained by acylation of monosubstituted diamine with diethylenetriaminepentaacetic acid dianhydride followed by deprotection ofthe amino group, purification by anion exchange chromatography and chelation of Eu3+. This metal chelate derivative was used for labeling 17α-hydroxyprogesterone 3-(O-carboxymethyl)oxime and horseradish peroxidase. The enzyme modified with the Eu3+ complexonate at the carbohydrate component and with a cortisol derivative at the polypeptide chain was used in a dissociation-enhanced lanthanide fluorescent immunoassay (DELFIA) as well as in an enzyme immunoassay of the steroid hormone. DELFIA showed that labeled 17α-hydroxyprogesterone retained the affinity for corresponding antibodies. A Eu(3+)-complexonate carboxy-derivative N-succinimide ester was obtained by acylation of the aminochelate with p-phthalic acid di-N-succinimide ester. It was used for modification of amino groups of lysine residues in polypeptide chains of human serum albumin and some immunoglobulins G. Purification of Eu3+ complexonate-protein conjugates by gel-chromatography on a Superose- 12 column allowed to separate the modified proteins from unreacted low molecular weight Eu(3+)-derivatives and to determine a degree of lanthanide inclusion into a protein. The amount of Eu3+ covalently attached to a protein was determined by measuring the fluorescence of a conjugate in the dissociative-enhancement solution. The obtained values correlated well with the results of ICP-MS determination of Eu3+ concentration in a conjugate solution. It was shown that conjugates of monoclonal antibodies obtained by the proposed method possessed the required characteristics of fluorescence intensity, signal-to-noise ratio, sensitivity and specificity in DELFIA medical diagnostic systems.

Comparison of 111In-[DTPA0]Octreotide Versus Non Carrier Added 177Lu- [DOTA0,Tyr3]-Octreotate Efficacy in Patients With GEP-NET Treated Intra-arterially for Liver Metastases

AIM

In patients with progressive, metastatic neuroendocrine tumors (NET), intra-arterial radionuclide infusions with high activities of In-[DTPA]-octreotide and more recently with non-carrier added (nca) Lu-[DOTA,Tyr]-octreotate have been performed with encouraging results. However, the affinity profiles (IC50) of these radiopeptides for human sst2 receptors are markedly different (In-[DTPA]-octreotide, 22 ± 3.6 nM and nca Lu-[DOTA,Tyr]-octreotate, 1.5 ± 4.0 nM). The total administered activity is determined by organ dose limits (kidneys and bone marrow), and our aim therefore was to compare and evaluate the therapeutic efficacy of both radiopeptides in metastatic NETs.

METHODS

Thirty patients with gastroenteropancreatic (GEP) somatostatin-positive NETs with liver metastases confirmed on biopsy and In-pentetreotide scan were included. They were treated with In-[DTPA]-octreotide (n = 17) or nca Lu-[DOTA,Tyr]-octreotate (n = 13). Blood samples were collected 2, 4, 8, and 24 hours postadministration to calculate residence time in blood and in red marrow. The maximum percentage uptake in organs and tumors was estimated by region of interest analysis, and tumor dosimetry calculations were performed using OLINDA/EXM/ 1.0 software.

RESULTS

ncaLu-[DOTA,Tyr3]-octreotate blood radioactivity, expressed as a percentage of the injected dose, was significantly lower than In-[DTPA]-octreotide (P < 0.05), as clearly depicted from the time-activity curves; the background-corrected tumor uptake was significantly higher than In-[DTPA]-octreotide but without any significant difference in other organs (spleen, kidneys, and liver).

CONCLUSIONS

Using Lu-[DOTA,Tyr]-octreotate, a 3-fold higher absorbed dose to tumor tissue was achieved compared with In-[DTPA] octreotide. Residence time of nca Lu-[DOTA,Tyr]-octreotate results in a significantly higher absorbed dose to bone marrow compared with In-[DTPA]-octreotide. However, a drawback of In-[DTPA]-octreotide therapy is that the number of administrations would need to be almost doubled to achieve an equal therapeutic outcome as compared with Lu-[DOTA,Tyr]-octreotate.

Development of magnetic separation and quantum dots labeled immunoassay for the detection of mercury in biological samples

A rapid and sensitive immunoassays of mercury (Hg) in biological samples was developed using quantum dots (QDs) and magnetic beads (MBs) as fluorescent and separated probes, respectively. A monoclonal antibody (mAb) that recognizes an Hg detection antigen (BSA-DTPA-Hg) complex was produced by the injection of BALB/c mice with an Hg immunizing antigen (KLH-DTPA-Hg). Then the ascites monoclonal antibodies were purified. The Hg monoclonal antibody (Hg-mAb) is conjugated with MBs to separate Hg from biological samples, and the other antibody, which is associated with QDs, is used to detect the fluorescence. The Hg in biological samples can be quantified using the relationship between the QDs fluorescence intensity and the concentration of Hg in biological samples following magnetic separation. In this method, the detection linear range is 1-1000ng/mL, and the minimum detection limit is 1ng/mL. The standard addition recovery rate was 94.70-101.18%. The relative standard deviation values were 2.76-7.56%. Furthermore, the Hg concentration can be detected in less than 30min, the significant interference of other heavy metals can be avoided, and the simultaneous testing of 96 samples can be performed. These results indicate that the method could be used for rapid monitoring Hg in the body.

Species-dependent chelation of (241)Am by DTPA Di-ethyl ester

Diethylenetriaminepentaacetic acid (DTPA) is an FDA-approved chelating agent for enhancing the elimination of transuranic elements such as americium from the body. Early access to therapy minimizes deposition of these radionuclides in tissues such as the bone. Due to its poor oral bioavailability, DTPA is administered as an IV injection, delaying access. Therefore, a diethyl-ester analog of DTPA, named C2E2, was synthesized as a means to increase oral absorption. As a hexadentate ligand, it was hypothesized that C2E2 was capable of binding americium directly. Therefore, the protonation constants and americium stability constant for C2E2 were determined by potentiometric titration and a solvent extraction method, respectively. C2E2 was shown to bind americium with a log K of 19.6. The concentrations of C2E2, its metabolite C2E1, and DTPA required to achieve effective binding in rat, beagle, and human plasma were studied in vitro. Dose response curves for each ligand were established, and the 50% maximal effective concentrations were determined for each species. As expected, higher concentrations of C2E2 were required to achieve the same degree of binding as DTPA. The results indicated that chelation in beagle plasma is more representative of the human response than rats. Finally, the pharmacokinetics of C2E2 were investigated in beagles, and the data was fit to a two-compartment model with elimination from the central compartment, along with first-order absorption. Based on the in vitro data, a 100 mg kg dose of C2E2 can be expected to have an effective duration of action of 3.8 h in beagles.

Decorporation of systemically distributed americium by a novel orally administered diethylenetriaminepentaacetic acid (DTPA) formulation in beagle dogs

Novel decorporation agents are being developed to protect against radiological accidents and terrorists attacks. Radioactive americium is a significant component of nuclear fallout. Removal of large radioactive materials, such as 241Am, from exposed persons is a subject of significant interest due to the hazards they pose. The objective of this study was to evaluate the dose-related efficacy of daily doses of NanoDTPA™ Capsules for decorporating Am administered intravenously as a soluble citrate complex to male and female beagle dogs. In addition, the efficacy of the NanoDTPA™ Capsules for decorporating 241Am was directly compared to intravenously administered saline and DTPA. Animals received a single IV administration of 241Am(III)-citrate on Day 0. One day after radionuclide administration, one of four different doses of NanoDTPA™ Capsules [1, 2, or 6 capsules d(-1) (30 mg, 60 mg, or 180 mg DTPA) or 2 capsules BID], IV Zn-DTPA (5 mg kg(-1) pentetate zinc trisodium) as a positive control, or IV saline as a placebo were administered. NanoDTPA™ Capsules, IV Zn-DTPA, or IV saline was administered on study days 1-14. Animals were euthanized on day 21. A full necropsy was conducted, and liver, spleen, kidneys, lungs and trachea, tracheobronchial lymph nodes (TBLN), muscle samples (right and left quadriceps), gastrointestinal (GI) tract (stomach plus esophagus, upper and lower intestine), gonads, two femurs, lumbar vertebrae (L1-L4), and all other soft tissue remains were collected. Urinary and fecal excretion profiles were increased approximately 10-fold compared to those for untreated animals. Tissue contents were decreased compared to untreated controls. In particular, liver content was decreased by approximately eightfold compared to untreated animals. The results from this study further demonstrate that oral NanoDTPA™ Capsules are equally efficient compared to IV Zn-DTPA in decorporation of actinides.

Evaluation and comparison of a new DOTA and DTPA-bombesin agonist in vitro and in vivo in low and high GRPR expressing prostate and breast tumor models

We evaluated and compared a new bombesin analog [Tyr-Gly5, Nle(14)]-BBN(6-14) conjugated to DOTA or DTPA and radiolabeled with In-111 in low and high GRPR expressing tumor models. Both peptides were radiolabeled with high radiochemical purity and specific activity. In vitro assays on T-47D, LNCaP and PC-3 cells showed that the affinity of peptides is similar and a higher binding and internalization of DOTA-peptide to PC-3 cells was observed. Both peptides could target PC-3 and LNCaP tumors in vivo and both tumor types could be visualized by microSPECT/CT.

Non-invasive magnetic resonance imaging follow-up of sono-sensitive liposome tumor delivery and controlled release after high-intensity focused ultrasound

This work examines the use of lanthanide-based contrast agents and magnetic resonance imaging in monitoring liposomal behavior in vivo. Dysprosium (Dy) and gadolinium (Gd) chelates, Dy-diethylenetriaminepentaacetic acid bismethylamide (Dy-DTPA-BMA) and Gd-DTPA-BMA, were encapsulated in pegylated distearoylphosphatidylethanolamine-based (saturated) liposomes, and then intravenously injected into Copenhagen rats with subcutaneous Dunning AT2 xenografts. Liposome-encapsulated Dy chelate shortens transverse relaxation times (T(2) and T(2)*) of tissue; thus, liposomal accumulation in the tumor can be monitored by observing the decrease in T(2)* relaxation time over time. The tumor was treated at the time of maximum liposomal accumulation (48 h) with confocal, cavitating high-intensity focused ultrasound to induce liposomal payload release. Using liposome-encapsulated Gd chelate at high enough concentrations and saturated liposomal phospholipids induces an exchange-limited longitudinal (T(1)) relaxation when the liposomes are intact; when the liposomes are released, exchange limitation is relieved, thus allowing in vivo observation of payload release as a decrease in tumor T(1).

Radionuclide decorporation: matching the biokinetics of actinides by transdermal delivery of pro-chelators

The threat of nuclear terrorism by the deliberate detonation of a nuclear weapon or radiological dispersion device ("dirty bomb") has made emergency response planning a priority. The only FDA-approved treatments for contamination with isotopes of the transuranic elements Am, Pu, and Cm are the Ca and Zn salts of diethylenetriaminepentaacetic acid (DTPA). These injectable products are not well suited for use in a mass contamination scenario as they require skilled professionals for their administration and are rapidly cleared from the circulation. To overcome the mismatch in the pharmacokinetics of the DTPA and the biokinetics of these transuranic elements, which are slowly released from contamination sites, the penta-ethyl ester of DTPA (C2E5) was prepared and formulated in a nonaqueous gel for transdermal administration. When gels comprised of 40% C2E5, 40-45% Miglyol® 840, and 15-20% ethyl cellulose were spiked with [(14)C]-C2E5 and applied to rat skin; over 60% of the applied dose was absorbed within a 24-h period. Radioactivity was observed in urinary and fecal excretions for over 3 days after removal of the gel. Using an (241)Am wound contamination model, transdermal C2E5 gels were able to enhance total body elimination and reduce the liver and skeletal burden of (241)Am in a dose-dependent manner. The efficacy achieved by a single 1,000 mg/kg dose to contaminated rats was statistically comparable to intravenous Ca-DTPA at 14 mg/kg. The effectiveness of this treatment, favorable sustained release profile of pro-chelators, and ease of administration support its use following radiological emergencies and for its inclusion in the Strategic National Stockpile.

A comparative study of two novel nanosized radiolabeled analogues of methionine for SPECT tumor imaging

It has been reported that most tumor cells show an increased uptake of variety of amino acids specially methionine when compared with normal cells and amino acid transport is generally increased in malignant transformation. Based on the evidences, two novel nanosized analogues of methionine (Anionic Linear Globular Dendrimer G(2), a biodigredabale anionic linear globular-Methionin, and DTPA-Methionine(1) conjugates) were synthesized and labeled with (99m)Tc and used in tumor imaging/ therapy in vitro and in vivo. The results showed marked tumor SPECT molecular imaging liabilities for both compounds but with a better performance by administration of (99m)Tc-Dendrimer G(2)-Methionin. The results also showed a good anticancer activity for 99mTc-DTPA-Methionine. Based on the present study (99m)Tc-Dendrimer G(2)-Methionin or 99mTc-DTPA-(Methionine)(1) have potentials to be used in tumor molecular imaging as well as cancer therapy in future.

Nanographene oxide-based radioimmunoconstructs for in vivo targeting and SPECT imaging of HER2-positive tumors

Nanographene oxide (NGO) is a novel nano-wall material that tracks to tumors in vivo, and which, as a consequence of its large surface area, has the capacity to carry a large payload. This study explores the use of anti-HER2 antibody (trastuzumab)-conjugated NGO, radiolabeled with (111)In-benzyl-diethylenetriaminepentaacetic acid (BnDTPA) via ππ-stacking, for functional imaging. In two HER2-overexpressing murine models of human breast cancer, high tumor-to-muscle ratio was achieved, resulting in clear visualization of tumor using single-photon emission computed tomography (SPECT). In the BALB/neuT model and in BALB/c nu/nu mice bearing 231/H2N xenografts, tumor accumulation amounted to 12.7 ± 0.67 and 15.0 ± 3.7% of the injected dose/g (%ID/g) of tumor tissue at 72 h, with tumor-to-muscle ratios of 35:1 and 7:1, respectively. Radiolabeled NGO-trastuzumab conjugates demonstrated superior pharmacokinetics compared to radiolabeled trastuzumab without NGO, with more rapid clearance from the circulation. The use of NGO as a scaffold to build radiolabeled nano-immunoconstructs holds promise for molecular imaging of tumors.

Preparation and characterization of artificial antigens for cadmium and lead

Cadmium and lead were conjugated to two carrier proteins using a bifunctional chelator [2-(4-aminobenzyl)-diethylenetriaminepentaacetic acid] to synthesize artificial antigens for cadmium and lead. The techniques, including ultraviolet spectrometry, circular dichroism, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and inductively coupled plasma optical emission spectroscopy, were utilized for characterizing the artificial antigens. The results of ultraviolet spectrometry showed characteristic absorption peak shifts between conjugates and carrier proteins. Circular dichroism resulted that the second structure of the conjugates was α-helix. The sodium dodecyl sulfate polyacrylamide gel electrophoresis results revealed the differences of band migration and molecular weight among antigens, chelator protein conjugate, and carrier proteins. The result of coupling ratios revealed that the metal content of the antigens was much higher than that of carrier proteins. These results indicated that the artificial antigens of cadmium and lead were synthesized successfully and had potential application in immunoassays of cadmium and lead ions.

Relationship between chromatin structure and sensitivity to molecularly targeted auger electron radiation therapy

PURPOSE

The open structure of euchromatin renders it susceptible to DNA damage by ionizing radiation (IR) compared with compact heterochromatin. The effect of chromatin configuration on the efficacy of Auger electron radiotherapy was investigated.

METHODS AND MATERIALS

Chromatin structure was altered in MDA-MB-468 and 231-H2N human breast cancer cells by suberoylanilide hydroxamic acid (SAHA), 5-aza-2-deoxycytidine, or hypertonic treatment. The extent and duration of chromatin structural changes were evaluated using the micrococcal nuclease assay. DNA damage (γH2AX assay) and clonogenic survival were evaluated after exposure to (111)In-DTPA-hEGF, an Auger electron-emitting radiopharmaceutical, or IR. The intracellular distribution of (111)In-DTPA-hEGF after chromatin modification was investigated in cell fractionation experiments.

RESULTS

Chromatin remained condensed for up to 20 minutes after NaCl and in a relaxed state 24 hours after SAHA treatment. The number of γH2AX foci per cell was greater in MDA-MB-468 and 231-H2N cells after IR (0.5 Gy) plus SAHA (1 μM) compared with IR alone (16 ± 0.6 and 14 ± 0.3 vs. 12 ± 0.4 and 11 ± 0.2, respectively). More γH2AX foci were observed in MDA-MB-468 and 231-H2N cells exposed to (111)In-DTPA-hEGF (6 MBq/μg) plus SAHA vs. (111)In-DTPA-hEGF alone (11 ± 0.3 and 12 ± 0.7 vs. 9 ± 0.4 and 7 ± 0.3, respectively). 5-aza-2-deoxycytidine enhanced the DNA damage caused by IR and (111)In-DTPA-hEGF. Clonogenic survival was reduced in MDA-MB-468 and 231-H2N cells after IR (6 Gy) plus SAHA (1 μM) vs. IR alone (0.6% ± 0.01 and 0.3% ± 0.2 vs. 5.8% ± 0.2 and 2% ± 0.1, respectively) and after (111)In-DTPA-hEGF plus SAHA compared to (111)In-DTPA-hEGF alone (21% ± 0.4% and 19% ± 4.6 vs. 33% ± 2.3 and 32% ± 3.7). SAHA did not affect (111)In-DTPA-hEGF nuclear localization. Hypertonic treatment resulted in fewer γH2AX foci per cell after IR and (111)In-DTPA-hEGF compared to controls but did not significantly alter clonogenic survival.

CONCLUSIONS

Chromatin structure affects DNA damage and cell survival after exposure to Auger electron radiation.

Immunohistochemical localization and quantitative expression of somatostatin receptors in normal human spleen and thymus: Implications for the in vivo visualization during somatostatin receptor scintigraphy

BACKGROUND

[111In-DTPA-D-Phe1]-octreotide scintigraphy allows the visualization of SRIF receptor (SSR)-expressing tumors, including thymic tumors, and normal tissues. While the spleen is clearly visualized, the thymus is not depicted, although both contain SSR.

AIM

We evaluated whether the heterogeneity, the type, and the amount of SSR might explain this contrasting finding.

MATERIALS, METHODS, AND RESULTS

By ligand-binding the number of [125I-Tyr11]-SRIF- 14 binding sites resulted comparable between the two tissues, whereas the number of [125I-Tyr3]-octreotide sites was significantly higher in the spleen (p<0.001). Quantitative RTPCR showed a significantly higher expression of sst2A mRNA in the spleen, whereas a significantly higher expression of SRIF and sst3 in the thymus. The highest density of sst2A in the spleen is in line with the in vivo uptake of [111In-DTPA-D-Phe1]- octreotide, which is considered a sst2-preferring ligand. The specificity is confirmed by the evidence that in vivo [111In-DTPA- D-Phe1]-octreotide uptake can be abolished during chronic administration of "cold" octreotide. Immunohistochemistry confirmed a preferential expression of sst2A on microenvironmental cells and of sst3 on lymphoid cells.

CONCLUSIONS

The heterogeneity of SSR expression and the higher SRIF content explain the lack of thymus visualization during scintigraphy, whereas thymic tumors, which do not express SRIF, are visualized. Apart from the affinity of the radioligand, also the efficacy of the internalization is crucial for the in vivo uptake, and both heterogeneity and SRIF content affect this process. These observations might have an important impact when interpretating in vivo visualization of SSR-positive lesions, and when treatment with novel SRIF analogs is considered.

New clathrin-based nanoplatforms for magnetic resonance imaging

Background

Magnetic Resonance Imaging (MRI) has high spatial resolution, but low sensitivity for visualization of molecular targets in the central nervous system (CNS). Our goal was to develop a new MRI method with the potential for non-invasive molecular brain imaging. We herein introduce new bio-nanotechnology approaches for designing CNS contrast media based on the ubiquitous clathrin cell protein.

Methodology/Principal Findings

The first approach utilizes three-legged clathrin triskelia modified to carry 81 gadolinium chelates. The second approach uses clathrin cages self-assembled from triskelia and designed to carry 432 gadolinium chelates. Clathrin triskelia and cages were characterized by size, structure, protein concentration, and chelate and gadolinium contents. Relaxivity was evaluated at 0.47 T. A series of studies were conducted to ascertain whether fluorescent-tagged clathrin nanoplatforms could cross the blood brain barriers (BBB) unaided following intranasal, intravenous, and intraperitoneal routes of administration. Clathrin nanoparticles can be constituted as triskelia (18.5 nm in size), and as cages assembled from them (55 nm). The mean chelate: clathrin heavy chain molar ratio was 27.04±4.8: 1 for triskelia, and 4.2±1.04: 1 for cages. Triskelia had ionic relaxivity of 16 mM⁻¹s⁻¹, and molecular relaxivity of 1,166 mM⁻¹s⁻¹, while cages had ionic relaxivity of 81 mM⁻¹s⁻¹ and molecular relaxivity of 31,512 mM⁻¹s⁻¹. Thus, cages exhibited 20 times higher ionic relaxivity and 8,000-fold greater molecular relaxivity than gadopentetate dimeglumine. Clathrin nanoplatforms modified with fluorescent tags were able to cross or bypass the BBB without enhancements following intravenous, intraperitoneal and intranasal administration in rats.

Conclusions/Significance

Use of clathrin triskelia and cages as carriers of CNS contrast media represents a new approach. This new biocompatible protein-based nanotechnology demonstrated suitable physicochemical properties to warrant further in vivo imaging and drug delivery studies. Significantly, both nanotransporters crossed and/or bypassed the BBB without enhancers. Thus, clathrin nanoplatforms could be an appealing alternative to existing CNS bio-nanotechnologies.

Melanocortins protect against multiple organ dysfunction syndrome in mice

BACKGROUND AND PURPOSE

Melanocortins reverse circulatory shock and improve survival by counteracting the systemic inflammatory response, and through the activation of the vagus nerve-mediated cholinergic anti-inflammatory pathway. To gain insight into the potential therapeutic value of melanocortins against multiple organ damage following systemic inflammatory response, here we investigated the effects of the melanocortin analogue [Nle⁴ D-Phe⁷]α-MSH (NDP-α-MSH) in a widely used murine model of multiple organ dysfunction syndrome (MODS).

EXPERIMENTAL APPROACH

MODS was induced in mice by a single intraperitoneal injection of lipopolysaccharide followed, 6 days later (= day 0), by zymosan. After MODS or sham MODS induction, animals were randomized to receive intraperitoneally NDP-α-MSH (340 µg·kg⁻¹ day) or saline for up to 16 days. Additional groups of MODS mice were concomitantly treated with the melanocortin MC₄ receptor antagonist HS024, or the nicotinic acetylcholine receptor antagonist chlorisondamine, and NDP-α-MSH.

KEY RESULTS

At day 7, in the liver and lung NDP-α-MSH, significantly reduced mRNA expression of tumour necrosis factor-α (TNF-α), increased mRNA expression of interleukin-10 and improved the histological picture, as well as reduced TNF-α plasma levels; furthermore, NDP-α-MSH dose-dependently increased survival rate, as assessed throughout the 16 day observation period. HS024 and chlorisondamine prevented all the beneficial effects of NDP-α-MSH in MODS mice.

CONCLUSIONS AND IMPLICATIONS

These data indicate that NDP-α-MSH protects against experimental MODS by counteracting the systemic inflammatory response, probably through brain MC₄ receptor-triggered activation of the cholinergic anti-inflammatory pathway. These findings reveal previously undescribed effects of melanocortins and could have clinical relevance in the MODS setting.

Tikhonov adaptively regularized gamma variate fitting to assess plasma clearance of inert renal markers

The Tk-GV model fits Gamma Variates (GV) to data by Tikhonov regularization (Tk) with shrinkage constant, λ, chosen to minimize the relative error in plasma clearance, CL (ml/min). Using (169)Yb-DTPA and (99m)Tc-DTPA (n = 46, 8-9 samples, 5-240 min) bolus-dilution curves, results were obtained for fit methods: (1) Ordinary Least Squares (OLS) one and two exponential term (E₁ and E₂), (2) OLS-GV and (3) Tk-GV. Four tests examined the fit results for: (1) physicality of ranges of model parameters, (2) effects on parameter values when different data subsets are fit, (3) characterization of residuals, and (4) extrapolative error and agreement with published correction factors. Test 1 showed physical Tk-GV results, where OLS-GV fits sometimes-produced nonphysical CL. Test 2 showed the Tk-GV model produced good results with 4 or more samples drawn between 10 and 240 min. Test 3 showed that E₁ and E₂ failed goodness-of-fit testing whereas GV fits for t > 20 min were acceptably good. Test 4 showed CL(Tk-GV) clearance values agreed with published CL corrections with the general result that CL(E1) > CL(E2) > CL(Tk-GV) and finally that CL(Tk-GV) were considerably more robust, precise and accurate than CL(E2), and should replace the use of CL(E2) for these renal markers.

Association of somatostatin receptor 2 immunohistochemical expression with [111In]-DTPA octreotide scintigraphy and [68Ga]-DOTATOC PET/CT in neuroendocrine tumors

In the absence of preoperative somatostatin receptor ( SST) scans, knowledge of immunohistochemical SST2 tumor expression may help predicting the success of somatostatin analogue-based follow-up studies and treatment of neuroendocrine tumors (NET). We studied the association between SST immunostaining and tracer uptake in [(111)In]-DTPA octreotide (DTPAOC) scintigraphy and [(68)Ga]-DOTA-D-Phe(1)-Tyr(3)-octreotide (DOTATOC) positron emission tomography (PET)/computed tomography (CT). Retrospective analy-sis of 36 NET patients was carried out. In 40 tumors, immunohistochemical SST2, SST3, and SST5 expressions were analyzed using a pathological scoring, applying monoclonal ( SST2) or polyclonal antibodies (SST3, SST5). In 14 lesions, [(111)In]-DTPAOC uptake was assessed by a semiquantitative score. In 26 tumors, [(68)Ga]-DOTATOC PET/CT was quantified using an uptake score and maximal standard uptake value (SUV(max)). Combined and separate qualitative analysis of SST scans revealed significant associations between increased tracer uptake and immunohistochemical SST2 detection (combined: rho=0.56, p=0.0002, [(111)In]-DTPAOC: rho=0.63, p=0.0152, and [(68)Ga]-DOTATOC: rho=0.52, p=0.0065, respectively). In contrast, SST3 and SST5 immunostaining was not associated with tracer uptake (all p>0.14). The semiquantitative immunohistochemical score for SST2 was associated with the [(68)Ga]-DOTATOC uptake score and SUV (max) values (rho=0.67, p=0.0002 and rho=0.63, p=0.0010, respectively), but not with the [(111)In]-DTPAOC uptake score (rho=0.24, p=0.4). In patients without preoperative SST scans, knowledge of immunohistochemical SST2 expression may help estimating the value of SST imaging in the clinical follow-up, in particular in those lesions with positive SST2 immunostaining. Negativity for SST2, however, does not rule out tracer uptake in some patients, with heterogeneous SST2 expression within the tumor as a potential explanation.

Tecnetium-99m as alternative to produce somatostatin-labeled derivatives: comparative biodistribution evaluation with 111In-DTPA-octreotide

Synthetic somatostatin (SST) analogues have been used in the preparation of receptor-specific radiopharmaceuticals for diagnostic and therapy of neuroendocrine tumors. This work studied the labeling conditions with (99m)Tc and biological distribution in Swiss mice of two SST analogs (HYNIC-Tyr(3)-Octreotide and HYNIC-Tyr(3)-Octreotate) and compared the biodistribution pattern with (111)In-DTPA-Octreotide. Biological distribution studies were performed after injection of radiopharmaceuticals on Swiss mice. Labeling procedures resulted on high radiochemical yield for all three preparations and the labeled products presented high in vitro stability. Biological distribution studies evidenced similar general biodistribution of (99m)Tc-labeled peptides when compared with indium-labeled peptide with fast blood clearance and elimination by urinary tract. Kidneys uptake of (99m)Tc-HYNIC-TATE are similar to (111)In-DTPA-Octreotide, and both are significantly higher than (99m)Tc-HYNIC-OCT. All labeled peptides presented similar uptake on liver, but the retention in time at intestines, particularly at large intestine, was more expressive for (111)In-labeled peptide. The %ID of (99m)Tc-HYNIC-OCT and (99m)Tc-HYNIC-TATE in organs with high density of SST receptors like pancreas and adrenals were significant and similar to obtained for (111)In-DTPA-Octreotide, confirming the affinity of these radiopharmaceuticals for the receptors.

Non-destructive separation of metal ions from wastewater containing excess aminopolycarboxylate chelant in solution with an ion-selective immobilized macrocyclic material

Although the excellent metal-binding capacities of aminopolycarboxylate chelants (APCs) facilitate their extensive use, pre- and post-toxicity of APCs and their high persistence in aquatic environments evoke concerns. Several treatment techniques with a principal focus on the degradation of APCs at the pre-release step have been proposed. Here, we report a technique for the separation of metal ions from waste solution containing excess APCs using a solid phase extraction system with an ion-selective immobilized macrocyclic material, commonly known as a molecular recognition technology (MRT) gel. Synthetic metal solutions with 100-fold chelant content housed in H2O matrices were used as samples. The MRT gel showed a higher recovery rate compared with other SPE materials at 20 degrees C using a flow rate of 0.2 mL min(-1). The effects of solution pH, metal-chelant stability constants and ionic radii were assessed for 32 metals. Compared to the conventional treatment options for such waste solutions, our proposed technique has the advantage of non-destructive separation of both metal ions and chelants.

Preparation and in vitro evaluation of 111In-CHX-A"-DTPA-labeled anti-VEGF monoclonal antibody bevacizumab

Bevacizumab is a humanized monoclonal antibody that binds to vascular endothelial growth factor (VEGF) and prevents tumor angiogenesis. Radionuclide imaging using radiolabeled bevacizumab might be useful for selection of patients for anti-VEGF therapy. This study describes preparation of a potential imaging agent, 111In-CHX-A"-DTPA-bevacizumab, and evaluation of specificity of its binding to three tumor cell lines, SKOV3, LS174T and DU 145. Bevacizumab was conjugated with CHX-A"-DTPA and radiolabeled with 111In with high yield and excellent stability. Specificity of cellular binding was examined by a saturation assay using 100-fold excess of non-radiolabeled antibody. SKOV3 and LS174T tumor cell lines showed significantly specific binding, while DU 145 cells did not showed any specific binding. The specific binding is dependent to type of cell lines, which it is important for selection of tumor model for scintigraphic imaging of the VEGF expression.

Therapeutic efficacy of 177Lu-CHX-A''-DTPA-hu3S193 radioimmunotherapy in prostate cancer is enhanced by EGFR inhibition or docetaxel chemotherapy

BACKGROUND

This study investigated the biodistribution and therapeutic efficacy of Lutetium-177 (177Lu) radiolabeled anti-Lewis Y monoclonal antibody hu3S193 radioimmunotherapy (RIT) in mice bearing prostate cancer xenografts. The ability of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor AG1478 and docetaxel chemotherapy to enhance the efficacy of RIT was also assessed in vivo.

METHODS

The in vitro cytotoxicity of 177Lu labeled hu3S193 on Le(y) positive DU145 prostate cancer cells was assessed using proliferation assays, with induction of apoptosis measured by ELISA. The in vivo biodistribution and tumor localization of 177Lu-hu3S193 was assessed in mice bearing established DU145 tumor xenografts. The efficacy and maximum tolerated dose of 177Lu-hu3S193 RIT in vivo was determined by a dose escalation study. EGFR inhibitor AG1478 or docetaxel chemotherapy was administered at sub-therapeutic doses in conjunction with RIT in vivo.

RESULTS

177Lu-hu3S193 mediated significant induction of cytotoxicity and apoptosis in vitro. In vivo analysis of 177Lu-hu3S193 biodistribution demonstrated specific targeting of DU145 prostate cancer xenografts, with maximal tumor uptake of 33.2 +/- 3.9%ID/g observed at 120 hr post-injection. In RIT studies, 177Lu-hu3S193 caused specific and dose-dependent inhibition of prostate cancer tumor growth. A maximum tolerated dose of 350 microCi was determined for 177Lu-hu3S193. Combination of 177Lu-hu3S193 RIT with EGFR inhibitor AG1478 or docetaxel chemotherapy both significantly improved efficacy.

CONCLUSIONS

177Lu-hu3S193 RIT is effective as a single agent in the treatment of Le(y) positive prostate cancer models. The enhancement of RIT by AG1478 or docetaxel indicates the promise of combined modality strategies.

Octreo-SPECT/CT imaging for accurate detection and localization of suspected neuroendocrine tumors

AIM

The aim of the present study was to prospectively evaluate the add value provided by [(111)In]DTPA-octreotide single-photon emission computed tomography/computed tomography (Octreo-SPECT/CT) with respect to [(111)In]DTPA-octreotide SPECT (Octreo-SPECT) in terms of diagnostic accuracy and localization of neuroendocrine tumors (NETs).

METHODS

Eighty-one consecutive patients with known or suspected NET underwent [(111)In]DTPA-octreotide scintigraphy using an integrated SPECT/low-energy-CT system (Infinia & Hawkeye; GE Medical Systems, Milwaukee, WI, USA). SPECT and fused SPECT/CT images were interpreted separately and a lesion-by-lesion analysis was performed with regard to classification (probability of NET graded on a 5-point scale) and localization of each abnormal focal tracer uptake. A subgroup analysis, distinguishing between abdominal and thoracic lesions, and a patient-by-patient analysis for likelihood of NET in each patient was also performed. Standard of reference for confirming presence or absence of NET was either histopathology or clinical/imaging follow-up data. The value of SPECT/CT imaging was assessed by ROC analysis and McNemar test.

RESULTS

A final diagnosis of NET was achieved in 43 out of 81 patients and a total of 169 areas (138 NET and 31 benign/physiological) with focal tracer uptake were included in the final lesion-by-lesion analysis. SPECT/CT imaging led to a significantly higher proportion of patients (75/81=92.6% vs 64/81=79%) and lesions (163/169=96.4% vs 138/169=81.1%) correctly classified vs SPECT alone. ROC analysis confirmed that Octreo-SPECT/CT performed significantly better than Octreo-SPECT for the detection of NET on both patient- and lesion-based analysis, improving especially evaluation of abnormal tracer uptake in the abdomen. Moreover, Octreo-SPECT/CT accurately localized 160/169 (94.7%) lesions, significantly higher than SPECT alone (77/169= 45.6%).

CONCLUSIONS

Octreo-SPECT/CT allows more accurate detection and localization of NETs than simple Octreo-SPECT, with major benefits for lesions located in the abdomen.

Intraoperative hand held gamma probe detection of a recurrent nonfunctional neuroendocrine tumor

CONTEXT

The advantage of intraoperative gamma probe detection with (111)In-DPTA-octreotide radiotracer has previously been demonstrated in functional neuroendocrine tumors. We report the only known case of a recurrent nonfunctional pancreatic neuroendocrine neoplasm localized intraoperatively using this radiotracer and a hand held gamma probe.

CASE REPORT

A 51-year-old woman was found to have a recurrence 23 months after laparoscopic distal pancreatectomy, splenectomy and wedge resection of a liver metastasis for a non-functional neuroendocirne neoplasm of the pancreas. CT scan and (111)In-DPTA-octreotide scan displayed two lesions in the right lobe of the liver and a third area of increased isotope uptake adjacent to kidney and pancreas. A single liver lesion was seen on CT. There were concerns regarding the ability to localize the lesion in the upper abdomen. In order to facilitate identification the patient was injected with (111)In-DPTA-octreotide preoperatively and intraoperatively a gamma probe was used to identify two lymph node posterior to the pancreas, only one of which could be palpated.

CONCLUSION

In this case the technique of preoperative injection with octreotide radiotracer and intraoperative hand held gamma probe successfully localized a nonfunctional neuroendocrine tumor that CT scan and intraoperative exploration failed to identify.

Multimodality palliative treatment of (111)In-pentetreotide negative/(123)I-MIBG positive metastatic carcinoid - a case report

Patients with carcinoid tumours frequently present with metastatic disease. There are only a few therapeutic options for these patients, and the main goal of palliative treatment is to reduce symptoms and thus to improve quality of life. Current therapy includes surgical resection, hepatic artery embolisation, chemotherapy and somatostatin analogue treatment; however, all these options have limitations. It seems probable that therapeutic modalities based on radiopharmaceuticals may provide better therapy, not only in relation to symptom reduction but may also improve patient survival. In this case report we present a 46-year-old woman with a symptomatic carcinoid, who at the time of diagnosis had liver and abdominal lymph node metastases, the primary tumour being located in the terminal ileum. (111)In-pentetreotide scanning was negative, whereas (123)I-MIBG scanning showed high avidity in the tumour tissue. After right hemicolectomy, two courses of (131)I-MIBG treatment were given (12.95 GBq and 12 GBq, respectively). After the second dose of (131)I-MIBG temporary pancytopenia was present. Octreotide therapy was given empirically only for a short time and was stopped because of drug intolerance. The patient underwent tricuspid and pulmonary valve replacement because of her carcinoid heart disease, followed by two courses of embolisation of liver metastases. While (131)I-MIBG therapy reduced the patient's symptoms of flushing and diarrhoea, there has not yet been any effect on tumour response or 5-HIAA production. This case illustrates the multimodality and multidisciplinary approach to such patients.

Usefulness of [111In-DTPA0] octreotide scintigraphy in a family with von Hippel-Lindau disease

The identification of patients with von Hippel-Lindau (VHL) disease dictates accurate genetic counseling of family members, whereas screening for early detection of visceral and neurological involvement is usually performed by a combination of radiological and nuclear medicine techniques such as ultrasonography or contrast-enhanced computed tomography of the upper abdomen, magnetic resonance imaging of the central nervous system and 131I-metaiodobenzylguanidine-scintigraphy. The role of 111-indium-diethylenetriaminepentaacetic acid [111In-DTPA0] octreotide scintigraphy in this clinical context has never been investigated. Here, we report imaging findings in a VHL patient and in 3 consecutive family members undergoing clinical and radiological screening that included [111In-DTPA0] octreotide scintigraphy in addition to the above-mentioned procedures. Somatostatin receptor expression was investigated in vitro by immunohistochemistry in pancreatic tumor sections. On the basis of in vivo and in vitro findings, octreotide long-acting release treatment followed by 90Y-1,4,7,10-Tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA0)-Tyr3-octreotide led to a lack of progression in this patient although this result is a possibility which needs to be proved by further investigation and longer follow-up. The results of this study suggest that [111In-DTPA0] octreotide scintigraphy may be helpful in the routine work-up of VHL patients for diagnostic and therapeutic purposes.

Radioimmunotherapy with alpha-particle emitting 213Bi-C-functionalized trans-cyclohexyl-diethylenetriaminepentaacetic acid-humanized 3S193 is enhanced by combination with paclitaxel chemotherapy

PURPOSE

Previous experience in solid tumor radioimmunotherapy studies has indicated that greatest therapeutic efficacy is achieved in the treatment of small-volume disease. alpha-Particle-emitting radioisotopes possess several physical characteristics ideally suited to the treatment of minimal residual disease. Therefore, we have investigated the efficacy of the alpha-particle-emitting bismuth-213 (213Bi) radioimmunotherapy using the humanized anti-Lewis Y (Ley) monoclonal antibody humanized 3S193 (hu3S193).

EXPERIMENTAL DESIGN

The intracellular localization of hu3S193 in Ley-positive MCF-7 breast carcinoma cells was assessed by confocal microscopy. Cytotoxicity of 213Bi-hu3S193 and apoptosis was assessed using [3H]thymidine incorporation assay and ELISA, respectively. Immunoblotting for gamma-H2AX assessed DNA strand breaks. In vivo efficacy of 213Bi-hu3S193 was assessed using a minimal residual disease model in BALB/c nude mice, with radioconjugate [15, 30, and 60 microCi (9.2 microg)] injected 2 days after s.c. implantation of MCF-7 cells. Radioimmunotherapy was also combined with a single injection of 300 microg paclitaxel to explore improved efficacy. Further, mice with established tumors received 30, 60, or 120 microCi (14.5 microg) of 213Bi-hu3S193 to assess the effect of tumor volume on treatment efficacy.

RESULTS

hu3S193 is internalized via an endosomal and lysosomal trafficking pathway. Treatment with 213Bi-hu3S193 results in >90% cytotoxicity in vitro and induces apoptosis and increased gamma-H2AX expression. 213Bi-hu3S193 causes specific and significant retardation of tumor growth even in established tumors, and efficacy was enhanced by paclitaxel to produce defined complete responses.

CONCLUSIONS

These studies show the potency of alpha-particle radioimmunotherapy and warrant its further exploration in the treatment of micrometastatic disease in Ley-positive malignancies.

Evaluation of [(111/114m)In]CHX-A''-DTPA-ZHER2:342, an affibody ligand coniugate for targeting of HER2-expressing malignant tumors

AIM

Radionuclide imaging of the HER2 receptor, which is a target for trastuzumab therapy, can provide important diagnostic information. Further, targeting radionuclide therapy might be an option for treatment of HER2 expressing tumors. The phage-display selected Affibody ligand Z(HER2:342), which binds to HER2 with an affinity of 22 pM, may here play an important role. The small size of the Z(HER2:342), 7.5 kDa, enables quick tumor localization and fast blood clearance. Earlier, successful targeting of HER2-expressing xenografts using Z(HER2:342) labeled using [(111)In]benzyl-DTPA was reported. By changing to the CHX-A''-DTPA chelator, the stability and labeling kinetics of the radiometal-Z(HER2:342) conjugate can be improved. The aim of this study was to evaluate the labeling of the CHX-A''-DTPA-Z(HER2:342) conjugate with (111)In for diagnostic imaging and with (114m)In for locoregional radionuclide therapy.

METHODS

The isothiocyanate derivative of CHX-A''-DTPA was coupled to Z(HER2:342) in alkaline conditions at 37 degrees C. The conjugate was labeled with both (111)In and (114m)In and evaluated in vitro and in vivo.

RESULTS

Labeling with (111)In and (114m)In provided >95% yield after 30 min at RT. Specific radioactivity was 0.5 and 12 MBq/nmol, for (114m)In and (111)In, respectively. The radiolabeled conjugates demonstrated specific binding to HER2 expressing SKOV-3 cells. In mice bearing SKOV-3 xenografts, the tumor uptake of [(111)In]CHX-A''-DTPA-Z(HER2:342) 4 h postinjection was 10.3+/-3.6% IA/g and tumor-to-blood ratio about 190.

CONCLUSION

[(111)In]CHX-A''-DTPA-Z(HER2:342) is a promising candidate for the visualization of HER2 expression in malignant tumors. Labeled with (114m)In it could also be used for locoregional treatment of HER2 expressing tumors.

[Imaging of pediatric brain tumors using somatostatin analogue 111Ih-DTPA-D-Phe1-octreotide]

Malignant solid tumors and leukemias are the second most common causes of death in childhood. The most frequent pediatric solid tumors are brain tumors. Brain tumors, especially medulloblastoma should be treated by surgery, irradiation and chemotherapy. However, chemotherapy has only moderate effect. Pediatric brain tumors, especially medulloblastomas, express somatostatin receptors. The aim of this study was the investigation of the expression of somatostatin receptors in pediatric brain tumors for diagnostic and therapeutic purpose. Fifty-six scintigraphic imagings (111In-DTPA-D-Phe1-octreotide) made in 45 children treated with brain tumor at the Unit of Oncology of the 2nd Department of Pediatrics, Semmelweis University. The diagnosis was medulloblastoma in 21 cases (46.7%). MRI scans have been performed parallel with the Octreoscan images. Octreoscan images were positive in 27 of 56 (48.2%) cases. The 27 positive Octreoscan images consisted of 16 medulloblastomas, 4 ependymomas, 4 astrocytomas and 3 glioblastomas. In 37 (66.1%) cases the results of Octreoscans were the same as those of the MRI scans. However, in 19 scans (33.9%) the outcome was different. Octreoscan imaging is not suitable for differential diagnosis in pediatric brain tumors, including medulloblastomas. Isotopes specifically binding to the somatostatin receptors (111In-DTPA-D-Phe1-octreotide) can be applied in medulloblastomas for diagnosis and follow-up treatment. In Octreoscan-positive tumors the Octreoscan images establish the opportunity to somatostatin analogue and/or specifically targeted radiation therapies.

Radio-guided surgery in neuroendocrine tumors

The majority of Neuroendocrine tumors (NET) express somatostatin (SS) receptors, and thus can be successfully targeted with radiolabeled SS analogs in vivo. Somatostatin receptor scintigraphy (SRS) with (111)In-DTPA Octreotide is the main imaging technique for evaluation of NETs. Radio-guided surgery for NETs, therefore, primarily utilizes (111)In-DTPA Octreotide tumor localization mechanism and kinetics. Somatostatin analog radiopharmacy continues to evolve to include the development of more selective and higher affinity analogs and PET tracers. These changes are expected to open new venues for radio-guided surgery technology.

Epidural blood patch therapy for chronic whiplash-associated disorder

BACKGROUND

Despite the absence of objective neurological deficits, patients with chronic whiplash-associated disorder (WAD) complain of symptoms such as headache, dizziness, and nausea. These symptoms are also often experienced by patients with cerebrospinal fluid (CSF) leak. It was recently reported that radioisotope (RI) cisternography is useful in the diagnosis of intracranial hypotension due to CSF leak. We investigated the relation between chronic WAD and CSF leak by RI cisternography and evaluated whether epidural blood patch (EBP) administration is effective in the treatment of chronic WAD.

METHODS

We studied 66 patients with chronic WAD with symptoms lasting longer than 3 mo. All patients underwent RI cisternography to determine the presence of CSF leak. In patients in whom CSF leak was identified, EBP was administered. Symptoms were assessed before, 1 wk after, and 6 mo after EBP. Work status was also assessed and follow-up RI cisternography was performed.

RESULTS

Of the 66 patients, 37 showed CSF leak, and 36 of these patients received EBP 2.2 +/- 0.7 times. The mean duration of symptoms was 33 mo. One week after EBP, the percentage of patients with symptoms was decreased significantly compared with that before EBP; headache: 100% vs 17%, respectively, memory loss: 94% vs 28%, dizziness: 83% vs 47%, visual impairment: 81% vs 25%, nausea: 78% vs 42% (P < 0.01). These effects were also observed at the 6 month follow-up examination (P < 0.01). Work status was also significantly improved at follow-up.

CONCLUSIONS

We conclude that CSF leak should be considered in some cases of chronic WAD and that EBP is an effective therapy for chronic WAD.

[Indium-111-DTPA-phenyl-pentetreotide somatostatin receptors' scintigraphy in the evaluation of patients with suspected gastro-entero-pancreatic tumors. Comparison with computerized tomography]

Gastro-entero-pancreatic tumors (GEP) contain, in their majority, somatostatin receptors. In-111-DTPA-phenyl-pentetreotide has been proved to have high affinity for somatostatin receptors subtypes 2, 3 and 5. The aim of the present study was to evaluate the utility of (111)In-DTPA-O somatostatin receptors' scintigraphy (SRS) in the diagnosis of suspected GEP. Thirty-five consecutive patients (17 males and 18 females-mean age 57.9+/-7.6) with GEP as a possible diagnosis were enrolled in the study. The primary diagnosis was diarrheic syndrome susceptive of intestinal carcinoid tumor (24 patients), carcinoid of the rectum (2 patients), adenocarcinoma of the pancreas (2 patients), insulinoma (2 patients), gastrinoma (3 patients) and hepatocellular carcinoma (2 patients). All patients were submitted to computerized tomography (CT) of the thorax and the abdomen and pentetreotide SRS was performed 4 h (total body and SPET acquisition) and 24 h (planar views), post iv injection of 185 MBq of the radiolabeled compound. Results showed: Four of the patients were false positive diagnosed as having inflammatory intestinal disease and gallbladder dilatation. At the time of the evaluation, 14 of the remaining patients were free of disease, concerning secondary involvement. In these cases, CT and SRS studies matched each other, with no pathological lesions and no abnormal accumulation of the radiopharmaceutical respectively. Concerning pathological cases, only one SRS study in a patient with rectum carcinoid was normal, with liver lesions in the CT study. These lesions were considered as subtypes 2, 3 and 5 somatostatin receptors negative. SRS revealed three lesions more than CT. According to these results, sensitivity of SRS study was 93.8% and specificity 86.9%. The authors believe that molecular imaging of somatostatin receptors, is a sensitive method for the evaluation of patients with GEP tumors. However, in cases of intestinal disease, we should be aware of false positive results due to inflammatory processes and the presence of lymphocyte infiltration.

Pre-clinical evaluation of [111In]-benzyl-DOTA-Z(HER2:342), a potential agent for imaging of HER2 expression in malignant tumors

Imaging of expression of human epidermal growth factor receptor type 2 (HER2) in breast carcinomas may help to select patients eligible for trastuzumab therapy. The Affibody molecule Z(HER2:342) is a small (7-kDa) non-immunoglobulin affinity protein, which binds to HER2 with a picomolar affinity. Previously, a benzyl-DTPA conjugate of Z(HER2:342) was labeled with 111In and demonstrated good targeting in murine xenografts. We considered that the use of the macrocyclic chelator DOTA could increase the label stability and enhance a choice of nuclides, which could be used as a label for Z(HER2:342). The goal of this study was the preparation and pre-clinical evaluation of the indium-111- labeled DOTA-derivative of Z(HER2:342). Isothiocyanate-benzyl-DOTA was coupled to recombinant Z(HER2:342), and the conjugate was efficiently labeled with 111In at 60 degrees C. The specificity of 111In-benzyl-DOTA-Z(HER2:342) binding to HER2 was confirmed in vitro using HER2-expressing breast carcinoma BT474 and ovarian carcinoma SKOV-3 cell lines. Biodistribution of 111In-benzyl-DOTA-Z(HER2:342) was performed in nude mice bearing LS174T xenografts and compared directly with the biodistribution of 111In-benzyl-DTPA-Z(HER2:342). In vivo, 111In-benzyl-DOTA-Z(HER2:342) demonstrated quick clearance from blood and non-specific organs except the kidneys. Four hours post injection (pi), the tumor uptake of 111In-benzyl-DOTA-Z(HER2:342) (4.4+/-1.0% IA/g) was specific and the tumor-to-blood ratio was 23. The use of benzyl-DTPA provided higher tumor-to-blood and tumor-to-liver ratios. gamma-camera imaging showed clear visualization of HER2-expressing xenografts using 111In-benzyl-DOTA-Z(HER2:342). 111In-benzyl-DOTA-Z(HER2:342) has a potential for imaging of HER2 expression in malignant tumors.

Quantification of bifunctional diethylenetriaminepentaacetic acid derivative conjugation to monoclonal antibodies by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The results of the characterization of a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry-based method that was developed to establish the stoichiometry of CHX-A''-diethylenetriaminepentaacetic acid (DTPA) or benzyl-DTPA conjugated to a recombinant immunoglobulin G (IgG) are reported. This simple method does not require an accurate measurement of the sample protein concentration to accurately quantify the number of DTPA conjugated. It is also not necessary to thoroughly remove nonconjugated DTPA from the sample. The average number of moles of DTPA attached per mole of IgG was calculated from the difference in the observed masses of DTPA-IgG and nonconjugated IgG divided by the molecular weight of the DTPA derivative. As more DTPA is attached, the [M+H](+) peak of DTPA-IgG becomes broader and noisier. Also, the signal intensity in the mass spectrum decreases, apparently due to the increase in the heterogeneity in the number of DTPA attached to each molecule of IgG. The standard deviation of the measured mass and that of the stoichiometry of the DTPA attached per IgG increased as more DTPA was attached. The standard deviation, expressed as coefficient of variation for samples with 2 to 4 mol of DTPA attached per mole of IgG, was 8 to 9%.

Design, synthesis, and characterization of a dual modality positron emission tomography and fluorescence imaging agent for monoclonal antibody tumor-targeted imaging

A novel lysine-based trifunctional chelate 3 was designed, synthesized, and characterized and bears both a chelating moiety (CHX-A' ') for sequestering radiometals (86Y or 111In) and the near-infrared dye Cy5.5 for dual modality PET (or SPECT) and fluorescence imaging, respectively. Successful conjugation of 3 to the monoclonal antibody trastuzumab (Herceptin) was achieved by efficient thiol-maleimide chemistry, thereby yielding immunoconjugate 2. Analysis of 2 by flow cytometry and competitive binding assay demonstrates that immunoconjugate 2 binds to SKOV3 tumor cells comparably to native trastuzumab and, thus, may be used as a tumor-targeted monoclonal antibody probe for multimodality imaging.

Epidermal growth factor receptor inhibition modulates the nuclear localization and cytotoxicity of the Auger electron emitting radiopharmaceutical 111In-DTPA human epidermal growth factor

(111)In-DTPA-human epidermal growth factor ((111)In-DTPA-hEGF [DTPA is diethylenetriaminepentaacetic acid]) is an Auger electron-emitting radiopharmaceutical that targets EGF receptor (EGFR)-positive cancer. The purpose of this study was to determine the effect of EGFR inhibition by gefitinib on the internalization, nuclear translocation, and cytotoxicity of (111)In-DTPA-hEGF in EGFR-overexpressing MDA-MB-468 human breast cancer cells.

METHODS

Western blot analysis was used to determine the optimum concentration of gefitinib to abolish EGFR activation. Internalization and nuclear translocation of fluorescein isothiocyanate-labeled hEGF were evaluated by confocal microscopy in MDA-MB-468 cells (1.3 x 10(6) EGFRs/cell) in the presence or absence of 1 microM gefitinib. The proportion of radioactivity partitioning into the cytoplasm and nucleus of MDA-MB-468 cells after incubation with (111)In-DTPA-hEGF for 24 h at 37 degrees C in the presence or absence of 1 microM gefitinib was measured by cell fractionation. DNA double-strand breaks caused by (111)In were quantified using the gamma-H2AX assay, and radiation-absorbed doses were estimated. Clonogenic survival assays were used to measure the cytotoxicity of (111)In-DTPA-hEGF alone or in combination with gefitinib.

RESULTS

Gefitinib (1 microM) completely abolished EGFR phosphorylation in MDA-MB-468 cells. Internalization and nuclear translocation of fluorescein isothiocyanate-labeled EGF were not diminished in gefitinib-treated cells compared with controls. The proportion of internalized (111)In that localized in the nucleus was statistically significantly greater when (111)In-DTPA-hEGF was combined with gefitinib compared with (111)In-DTPA-hEGF alone (mean +/- SD: 26.0% +/- 5.5% vs. 14.6% +/- 4.0%, respectively; P < 0.05). Induction of gamma-H2AX foci was greater in MDA-MB-468 cells that were treated with (111)In-DTPA-hEGF (250 ng/mL, 1.5 MBq/mL) plus gefitinib (1 microM ) compared with those treated with (111)In-DTPA-hEGF alone (mean +/- SD: 35 +/- 4 vs. 24 +/- 5 foci per nucleus, respectively). In clonogenic assays, a significant reduction in the surviving fraction was observed when (111)In-DTPA-hEGF (5 ng/mL, 6 MBq/microg) was combined with gefitinib (1 microM ) compared with (111)In-DTPA-hEGF alone (42.9% +/- 5.7% vs. 22.9% +/- 3.6%, respectively; P < 0.01).

CONCLUSION

The efficacy of (111)In-DTPA-hEGF depends on internalization and nuclear uptake of the radionuclide. Nuclear uptake, DNA damage, and cytotoxicity are enhanced when (111)In-DTPA-hEGF is combined with gefitinib. These results suggest a potential therapeutic role for peptide receptor radionuclide therapy in combination with tyrosine kinase inhibitors.

Characterization of monoclonal antibodies for lead-chelate complexes: applications in antibody-based assays

Monoclonal antibodies against lead were generated by immunizing BALB/c mice with lead conjugated to keyhole limpet hemocyanin (KLH) via a bifunctional chelator, S-2-(4-aminobenzyl)diethylenetriamine pentaacetic acid (DTPA). Stable hybridoma cell lines were produced by fusion of murine splenocytes and SP2/0 myeloma cells. One of the hybridomas generated from this fusion (4/7) synthesized and secreted an antibody that bound tightly to Pb2+-DTPA complexes but not to metal-free DTPA. The performance for a competitive inhibition enzyme-linked immunosorbent assay (ELISA) incorporating this antibody was assessed for its sensitivity to changes in pH, ionic strength, and blocking reagents. The cross-reactivities in this ELISA were less than 3% for Fe3+, Cd2+, Hg2+, and Cu2+ and less than 0.3% for Cr3+, Mn2+, Mg2+, In3+, Ag1+, Ni2+, Co2+, Zn2+, Ca2+, Cu1+, and Hg1+. The IC50 value achieved for lead was 2.72 +/- 0.034 microM, showing the detection range of 0.092-87.2 microM and the lowest detection limit of 0.056 +/- 0.005 microM. Recoveries from the analyte-fortified tap water and ultrapure water were in the range of 80-114% . These results indicate that the ELISA could be a convenient analytical tool for monitoring lead residues in drinking water.

Chemical design of a radiolabeled gelatinase inhibitor peptide for the imaging of gelatinase activity in tumors

Since elevated levels of gelatinases [matrix metalloproteinase (MMP)-2 and MMP-9] are associated with a poor prognosis in cancer patients, these enzymes are potential targets for tumor imaging. In the present study, a cyclic decapeptide, cCTTHWGFTLC (CTT), was selected as a mother compound because of its selective inhibitory activity toward gelatinases. For imaging gelatinase activity in tumors, we designed a CTT-based radiopharmaceutical taking into consideration that (1) the HWGF motif of the peptide is important for the activity, (2) hydrophilic radiolabeled peptides show low-level accumulation in the liver and (3) an increase in the negative charge of radiolabeled peptides is effective in reducing renal accumulation. Thus, a highly hydrophilic and negatively charged radiolabel, indiun-111-diethylenetriaminepentaacetic acid ((111)In-DTPA), was attached to an N-terminal residue distant from the HWGF motif ((111)In-DTPA-CTT). In MMP-2 inhibition assays, In-DTPA-CTT significantly inhibited the proteolytic activity in a concentration-dependent fashion. When injected into normal mice, (111)In-DTPA-CTT showed low levels of radioactivity in the liver and kidney. A comparison of the pharmacokinetic characteristics of (111)In-DTPA-CTT with those of other CTT derivatives having different physicochemical properties revealed that the increase in hydrophilicity and negative charge caused by the conjugation of (111)In-DTPA reduced levels of radioactivity in the liver and kidney. In tumor-bearing mice, a significant correlation was observed between the accumulation in the tumor as well as tumor-to-blood ratio of (111)In-DTPA-CTT and gelatinase activity. These findings support the validity of the chemical design of (111)In-DTPA-CTT for reducing accumulation in nontarget tissues and maintaining the inhibitory activity of the mother compound. Furthermore, (111)In-DTPA-CTT derivatives would be potential radiopharmaceuticals for the imaging of gelatinase activity in metastatic tumors in vivo.

Somatostatin receptor subtype 2-mediated uptake of radiolabelled somatostatin analogues in the human kidney

PURPOSE

Renal irradiation is a dose-limiting factor in peptide receptor radionuclide therapy using radiolabelled somatostatin analogues. This irradiation is mainly caused by reabsorption of radiolabelled peptides in the proximal tubule. In the human kidney, somatostatin receptors are expressed in the vasa recta, tubuli and glomeruli. It is not clear to what extent these receptors contribute to the total kidney radioactivity uptake.

METHODS

Retrospectively, [(111)In-DTPA(0)]octreotide scans of ten selected patients with carcinoids (well-differentiated gastrointestinal endocrine tumour) with liver metastases were evaluated. For each patient, two scans were obtained: one scan was performed without (control) and one during treatment with unlabelled octreotide. Kidney, tumour, spleen and liver uptake was measured in both scans.

RESULTS

The interval between the two scans per patient varied from 50 to 397 days. Octreotide treatment substantially lowered kidney [(111)In-DTPA(0)]octreotide uptake in eight out of ten patients. Kidney uptake in all patients was reduced to 82%+/-15% of control, (p < 0.01). A correlation between kidney uptake and spleen uptake was found (r=0.67, p < 0.05). Serum creatinine was unchanged. Surprisingly, tumour and liver [(111)In-DTPA(0)]octreotide uptake was not significantly influenced by unlabelled octreotide therapy, but spleen uptake was significantly lowered by treatment (30.6% of control, p < 0.002).

CONCLUSION

We conclude that the somatostatin receptor plays a role in the total renal uptake of radiolabelled somatostatin analogues. The long interval between scans might explain the finding that tumour and liver metastasis uptake of [(111)In-DTPA(0)]octreotide was unchanged. Further studies are needed to confirm and eludicate the results of this study.

Preparation and Imaging Research on 188Re-DTPA-Deoxyglucose in MCF-7 Tumor-Bearing Mice

OBJECTIVE

To investigate the preparation of (188)Re-diethylenetriaminepentaacetic acid-2-deoxyglucose ((188)Re-DTPA-DG) and its imaging quality and therapeutic effect.

METHODS

Labeling of DTPA-DG with (188)Re was performed in the presence of stannous ion and sodium D-gluconate at a pH of 5.5 with 3 hours of incubation at 37 degrees C. The radiolabeling yields of (188)Re-DTPA-DG were determined by paper chromatography with a solution of acetone and saline (0.9% NaCl) as a developing agent. The imaging quality of (188)Re-DTPA-DG was determined by injecting 0.1 mL of a preparation having a radioactivity of 92.5GBq/L into the tail vein of nude mice bearing MCF-7 mammary tumors and imaging the tumors at 2, 4, 8, 12, and 24 hours after injection of the radiolabeled agent. Tumor volume was recorded every 2 or 3 days for 21 days.

RESULTS

The radiochemical purity of the (188)Re-DTPA-DG complex was 95.0%. In the imaging study, the tumor-to-nontumor-tissue ratios (T/NT) of radioactivity at 12 and 24 hours after intravenous injection of the radiolabeled agent were 5.9 and 7.8, respectively. The tumor volume in the (188)Re-DTPA-DG-treated group of mice increased more slowly than that in the control group, and the two groups differed greatly in this measure at 21 days, with tumor volumes of 823.6 +/- 50.58 mm(3) and 1162.7 +/- 73.08 mm(3) in the (188)Re-DTPA-DG treated and control groups, respectively (p < 0.01).

CONCLUSIONS

(188)Re-DTPA-DG showed excellent tumor targeting and tumor-growth-suppressing effects, and holds promise as an internal agent for tumor radiotherapy.

Visualizing the acute effects of vascular-targeted therapy in vivo using intravital microscopy and magnetic resonance imaging: correlation with endothelial apoptosis, cytokine induction, and treatment outcome

The acute effects of the vascular-disrupting agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA) were investigated in vivo using intravital microscopy (IVM) and magnetic resonance imaging (MRI). Changes in vascular permeability and blood flow of syngeneic CT-26 murine colon adenocarcinomas were assessed at 4 and 24 hours after DMXAA treatment (30 mg/kg, i.p.) and correlated with induction of tumor necrosis factor-alpha (TNF-alpha), endothelial damage [CD31/terminal deoxynucleotidyl transferase (TdT)], and treatment outcome. Intravital imaging revealed a marked increase in vascular permeability 4 hours after treatment, consistent with increases in intratumoral mRNA and protein levels of TNF-alpha. Parallel contrast-enhanced MRI studies showed a approximately 4-fold increase in longitudinal relaxation rates (DeltaR(1)), indicative of increased contrast agent accumulation within the tumor. Dual immunostained tumor sections (CD31/TdT) revealed evidence of endothelial apoptosis at this time point. Twenty-four hours after treatment, extensive hemorrhage and complete disruption of vascular architecture were observed with IVM, along with a significant reduction in DeltaR(1); and virtual absence of CD31 immunostaining. DMXAA-induced tumor vascular damage resulted in significant long-term (60-day) cures compared to untreated controls. Multimodality imaging approaches are useful in visualizing the effects of antivascular therapy in vivo. Such approaches allow cross validation and correlation of findings with underlying molecular changes contributing to treatment outcome.