Improved labelling of DTPA- and DOTA-conjugated peptides and antibodies with 111In in HEPES and MES buffer

Contains fulltext : 108269.pdf (publisher's version ) (Open Access)ABSTRACT: BACKGROUND: In single photon emission computed tomography [SPECT], high specific activity of 111In-labelled tracers will allow administration of low amounts of tracer to prevent receptor saturation and/or side effects. To increase the specific activity, we studied the effect of the buffer used during the labelling procedure: NaAc, NH4Ac, HEPES and MES buffer. The effect of the ageing of the 111InCl3 stock and cadmium contamination, the decay product of 111In, was also examined in these buffers. METHODS: Escalating amounts of 111InCl3 were added to 1 mug of the diethylene triamine pentaacetic acid [DTPA]- and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid [DOTA]-conjugated compounds (exendin-3, octreotide and anti-carbonic anhydrase IX [CAIX] antibody). Five volumes of 2-(N-morpholino)ethanesulfonic acid [MES], 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid [HEPES], NH4Ac or NaAc (0.1 M, pH 5.5) were added. After 20 min at 20 degrees C (DTPA-conjugated compounds), at 95 degrees C (DOTA-exendin-3 and DOTA-octreotide) or at 45 degrees C (DOTA-anti-CAIX antibody), the labelling efficiency was determined by instant thin layer chromatography. The effect of the ageing of the 111InCl3 stock on the labelling efficiency of DTPA-exendin-3 as well as the effect of increasing concentrations of Cd2+ (the decay product of 111In) were also examined. RESULTS: Specific activities obtained for DTPA-octreotide and DOTA-anti-CAIX antibody were five times higher in MES and HEPES buffer. Radiolabelling of DTPA-exendin-3, DOTA-exendin-3 and DTPA-anti-CAIX antibody in MES and HEPES buffer resulted in twofold higher specific activities than that in NaAc and NH4Ac. Labelling of DTPA-exendin-3 decreased with 66% and 73% for NaAc and NH4Ac, respectively, at day 11 after the production date of 111InCl3, while for MES and HEPES, the maximal decrease in the specific activity was 10% and 4% at day 11, respectively. The presence of 1 pM Cd2+ in the labelling mixture of DTPA-exendin-3 in NaAc and NH4Ac markedly reduced the labelling efficiency, whereas Cd2+ concentrations up to 0.1 nM did not affect the labelling efficiency in MES and HEPES buffer. CONCLUSIONS: We showed improved labelling of DTPA- and DOTA-conjugated compounds with 111In in HEPES and MES buffer. The enhanced labelling efficiency appears to be due to the reduced competitive chelation of cadmium. The enhanced labelling efficiency will allow more sensitive imaging of the biomarkers with SPECT

68Ga-labelled exendin-3, a new agent for the detection of insulinomas with PET

Contains fulltext : 89596.pdf (publisher's version ) (Closed access)PURPOSE: Insulinomas are neuroendocrine tumours derived from pancreatic beta-cells. The glucagon-like peptide 1 receptor (GLP-1R) is expressed with a high incidence (>90%) and high density in insulinomas. Glucagon-like peptide 1 (GLP-1), the natural ligand of GLP-1R, is rapidly degraded in vivo. A more stable agonist of GLP-1R is exendin-3. We investigated imaging of insulinomas with DOTA-conjugated exendin-3 labelled with (68)Ga. METHODS: Targeting of insulinomas with [Lys(40)(DOTA)]exendin-3 labelled with either (111)In or (68)Ga was investigated in vitro using insulinoma tumour cells (INS-1). [Lys(40)((111)In-DTPA)]Exendin-3 was used as a reference in this study. In vivo targeting was investigated in BALB/c nude mice with subcutaneous INS-1 tumours. PET imaging was performed using a preclinical PET/CT scanner. RESULTS: In vitro exendin-3 specifically bound and was internalized by GLP-1R-positive cells. In BALB/c nude mice with subcutaneous INS-1 tumours a high uptake of [Lys(40)((111)In-DTPA)]exendin-3 in the tumour was observed (33.5 +/- 11.6%ID/g at 4 h after injection). Uptake was specific, as determined by coinjection of an excess of unlabelled [Lys(40)]exendin-3 (1.8 +/- 0.1%ID/g). The pancreas also exhibited high and specific uptake (11.3 +/- 1.0%ID/g). High uptake was also found in the kidneys (144 +/- 24%ID/g) and this uptake was not receptor-mediated. In this murine tumour model optimal targeting of the GLP-1R expressing tumour was obtained at exendin doses < or =0.1 microg. Remarkably, tumour uptake of (68)Ga-labelled [Lys(40)(DOTA)]exendin-3 was lower (8.9 +/- 3.1%ID/g) than tumour uptake of (111)In-labelled [Lys(40)(DTPA)]exendin-3 (25.4 +/- 7.2%ID/g). The subcutaneous tumours were clearly visualized by small-animal PET imaging after injection of 3 MBq of [Lys(40)((68)Ga-DOTA)]exendin-3. CONCLUSION: [Lys(40)((68)Ga-DOTA)]Exendin-3 specifically accumulates in insulinomas, although the uptake is lower than that of [Lys(40)((111)In-DTPA)]exendin-3. Therefore, [Lys(40)((68)Ga-DOTA)]exendin-3 is a promising tracer to visualize insulinomas with PET.01 juli 201

18F-Labelled exendin to image GLP-1 receptor-expressing tissues: from niche to blockbuster?

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Outcomes and risk factors for cancer patients undergoing endoscopic intervention of malignant biliary obstruction

Background: Malignant bile duct obstruction is a common problem among cancer patients with hepatic or lymphatic metastases. Endoscopic retrograde cholangiography (ERC) with the placement of a stent is the method of choice to improve biliary flow. Only little data exist concerning the outcome of patients with malignant biliary obstruction in relationship to microbial isolates from bile. Methods: Bile samples were taken during the ERC procedure in tumor patients with biliary obstruction. Clinical data including laboratory values, tumor-specific treatment and outcome data were prospectively collected. Results: 206 ERC interventions in 163 patients were recorded. In 43 % of the patients, systemic treatment was (re-) initiated after successful biliary drainage. A variety of bacteria and fungi was detected in the bile samples. One-year survival was significantly worse in patients from whom multiresistant pathogens were isolated than in patients, in whom other species were detected. Increased levels of inflammatory markers were associated with a poor one-year survival. The negative impact of these two factors was confirmed in multivariate analysis. In patients with pancreatic cancer, univariate analysis showed a negative impact on one-year survival in case of detection of Candida species in the bile. Multivariate analysis confirmed the negative prognostic impact of Candida in the bile in pancreatic cancer patients. Conclusion: Outcome in tumor patients with malignant bile obstruction is associated with the type of microbial biliary colonization. The proof of multiresistant pathogens or Candida, as well as the level of inflammation markers, have an impact on the prognosis of the underlying tumor disease

Multicentre quantitative Ga-68 PET/CT performance harmonisation

Purpose Performance standards for quantitative F-18-FDG PET/CT studies are provided by the EANM Research Ltd. (EARL) to enable comparability of quantitative PET in multicentre studies. Yet, such specifications are not available for Ga-68. Therefore, our aim was to evaluate Ga-68-PET/CT quantification variability in a multicentre setting. Methods A survey across Dutch hospitals was performed to evaluate differences in clinical Ga-68 PET/CT study protocols. Ga-68 and F-18 phantom acquisitions were performed by 8 centres with 13 different PET/CT systems according to EARL protocol. The cylindrical phantom and NEMA image quality (IQ) phantom were used to assess image noise and to identify recovery coefficients (RCs) for quantitative analysis. Both phantoms were used to evaluate cross-calibration between the PET/CT system and local dose calibrator. Results The survey across Dutch hospitals showed a large variation in clinical Ga-68 PET/CT acquisition and reconstruction protocols. Ga-68 PET/CT image noise was below 10%. Cross-calibration was within 10% deviation, except for one system to overestimate F-18 and two systems to underestimate the Ga-68 activity concentration. RC-curves for F-18 and Ga-68 were within and on the lower limit of current EARL standards, respectively. After correction for local Ga-68/F-18 cross-calibration, mean Ga-68 performance was 5% below mean EARL performance specifications. Conclusions Ga-68 PET/CT quantification performs on the lower limits of the current EARL RC standards for F-18. Correction for local Ga-68/F-18 cross-calibration mismatch is advised, while maintaining the EARL reconstruction protocol thereby avoiding multiple EARL protocols

Computational redesign of thioredoxin is hypersensitive towards minor conformational changes in the backbone template

Despite the development of powerful computational tools, the full-sequence design of proteins still remains a challenging task. To investigate the limits and capabilities of computational tools, we conducted a study of the ability of the program Rosetta to predict sequences that recreate the authentic fold of thioredoxin. Focusing on the influence of conformational details in the template structures, we based our study on 8 experimentally determined template structures and generated 120 designs from each. For experimental evaluation, we chose six sequences from each of the eight templates by objective criteria. The 48 selected sequences were evaluated based on their progressive ability to (1) produce soluble protein in Escherichia coli and (2) yield stable monomeric protein, and (3) on the ability of the stable, soluble proteins to adopt the target fold. Of the 48 designs, we were able to synthesize 32, 20 of which resulted in soluble protein. Of these, only two were sufficiently stable to be purified. An X-ray crystal structure was solved for one of the designs, revealing a close resemblance to the target structure. We found a significant difference among the eight template structures to realize the above three criteria despite their high structural similarity. Thus, in order to improve the success rate of computational full-sequence design methods, we recommend that multiple template structures are used. Furthermore, this study shows that special care should be taken when optimizing the geometry of a structure prior to computational design when using a method that is based on rigid conformations

Myeloid STAT3 promotes formation of colitis-associated colorectal cancer in mice

Myeloid cells lacking STAT3 promote antitumor responses of NK and T cells but it is unknown if this crosstalk affects development of autochthonous tumors. We deleted STAT3 in murine myeloid cells (STAT3(Δm)) and examined the effect on the development of autochthonous colorectal cancers (CRCs). Formation of Azoxymethane/Dextransulfate (AOM/DSS)-induced CRCs was strongly suppressed in STAT3(Δm) mice. Gene expression profiling showed strong activation of T cells in the stroma of STAT3(Δm) CRCs. Moreover, STAT3(Δm) host mice were better able to control the growth of transplanted MC38 colorectal tumor cells which are known to be killed in a T cell-dependent manner. These data suggest that myeloid cells lacking STAT3 control formation of CRCs mainly via cross activation of T cells. Interestingly, the few CRCs that formed in STAT3(Δm) mice displayed enhanced stromalization but appeared normal in size indicating that they have acquired ways to escape enhanced tumor surveillance. We found that CRCs in STAT3(Δm) mice consistently activate STAT3 signaling which is implicated in immune evasion and might be a target to prevent tumor relapse

A 3D-printed anatomical pancreas and kidney phantom for optimizing SPECT/CT reconstruction settings in beta cell imaging using 111In-exendin

Contains fulltext : 165641.pdf (publisher's version ) (Open Access)BACKGROUND: Quantitative single photon emission computed tomography (SPECT) is challenging, especially for pancreatic beta cell imaging with 111In-exendin due to high uptake in the kidneys versus much lower uptake in the nearby pancreas. Therefore, we designed a three-dimensionally (3D) printed phantom representing the pancreas and kidneys to mimic the human situation in beta cell imaging. The phantom was used to assess the effect of different reconstruction settings on the quantification of the pancreas uptake for two different, commercially available software packages. METHODS: 3D-printed, hollow pancreas and kidney compartments were inserted into the National Electrical Manufacturers Association (NEMA) NU2 image quality phantom casing. These organs and the background compartment were filled with activities simulating relatively high and low pancreatic 111In-exendin uptake for, respectively, healthy humans and type 1 diabetes patients. Images were reconstructed using Siemens Flash 3D and Hermes Hybrid Recon, with varying numbers of iterations and subsets and corrections. Images were visually assessed on homogeneity and artefacts, and quantitatively by the pancreas-to-kidney activity concentration ratio. RESULTS: Phantom images were similar to clinical images and showed comparable artefacts. All corrections were required to clearly visualize the pancreas. Increased numbers of subsets and iterations improved the quantitative performance but decreased homogeneity both in the pancreas and the background. Based on the phantom analyses, the Hybrid Recon reconstruction with 6 iterations and 16 subsets was found to be most suitable for clinical use. CONCLUSIONS: This work strongly contributed to quantification of pancreatic 111In-exendin uptake. It showed how clinical images of 111In-exendin can be interpreted and enabled selection of the most appropriate protocol for clinical use