## Dynamic 2D and 3D mapping of hyperpolarized pyruvate to lactate conversion in vivo with efficient multi-echo balanced steady-state free precession at 3 T

© 2020 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd., 2020, DOI: 10.1002/nbm.4291 publiziert am 04.05.2020
The aim of this study was to acquire the transient MRI signal of hyperpolarized tracers and their metabolites efficiently, for which specialized imaging sequences are required. In this work, a multi-echo balanced steady-state free precession (me-bSSFP) sequence with Iterative Decomposition with Echo Asymmetry and Least squares estimation (IDEAL) reconstruction was implemented on a clinical 3 T positron-emission tomography/MRI system for fast 2D and 3D metabolic imaging. Simulations were conducted to obtain signal-efficient sequence protocols for the metabolic imaging of hyperpolarized biomolecules. The sequence was applied in vitro and in vivo for probing the enzymatic exchange of hyperpolarized [1-13 C]pyruvate and [1-13 C]lactate. Chemical shift resolution was achieved using a least-square, iterative chemical species separation algorithm in the reconstruction. In vitro, metabolic conversion rate measurements from me-bSSFP were compared with NMR spectroscopy and free induction decay-chemical shift imaging (FID-CSI). In vivo, a rat MAT-B-III tumor model was imaged with me-bSSFP and FID-CSI. 2D metabolite maps of [1-13 C]pyruvate and [1-13 C]lactate acquired with me-bSSFP showed the same spatial distributions as FID-CSI. The pyruvate-lactate conversion kinetics measured with me-bSSFP and NMR corresponded well. Dynamic 2D metabolite mapping with me-bSSFP enabled the acquisition of up to 420 time frames (scan time: 180-350 ms/frame) before the hyperpolarized [1-13 C]pyruvate was relaxed below noise level. 3D metabolite mapping with a large field of view (180 × 180 × 48 mm3 ) and high spatial resolution (5.6 × 5.6 × 2 mm3 ) was conducted with me-bSSFP in a scan time of 8.2 seconds. It was concluded that Me-bSSFP improves the spatial and temporal resolution for metabolic imaging of hyperpolarized [1-13 C]pyruvate and [1-13 C]lactate compared with either of the FID-CSI or EPSI methods reported at 3 T, providing new possibilities for clinical and preclinical applications.

## Classifcation of Polar Maps from Cardiac Perfusion Imaging with Graph-Convolutional Neural Networks

Scientific Reports, 2019, publiziert am 20.05.2019
Myocardial perfusion imaging is a non-invasive imaging technique commonly used for the diagnosis of Coronary Artery Disease and is based on the injection of radiopharmaceutical tracers into the blood stream. The patient’s heart is imaged while at rest and under stress in order to determine its capacity to react to the imposed challenge. Assessment of imaging data is commonly performed by visual inspection of polar maps showing the tracer uptake in a compact, two-dimensional representation of the left ventricle. This article presents a method for automatic classifcation of polar maps based on graph convolutional neural networks. Furthermore, it evaluates how well localization techniquesdeveloped for standard convolutional neural networks can be used for the localization of pathological segments with respect to clinically relevant areas. The method is evaluated using 946 labeled datasets and compared quantitatively to three other neural-network-based methods. The proposed model achieves an agreement with the human observer on 89.3% of rest test polar maps and on 91.1% of stress test polar maps. Localization performed on a fne 17-segment division of the polar maps achieves an agreement of 83.1% with the human observer, while localization on a coarse 3-segment division based on the vessel beds of the left ventricle has an agreement of 78.8% with the human observer. Our method could thus assist the decision-making process of physicians when analyzing polar map data obtained from myocardial perfusion images.

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## A novel chimeric oncolytic virus vector for improved safety and efficacy in hepatocellular carcinoma

2018, publiziert am 12.12.2018

## The influence of different metal-chelate conjugates of pentixafor on the CXCR4 affinity

Poschenrieder et al. EJNMMI Research, 2018, DOI 10.1186/s13550-016-0193-8 publiziert am 11.09.2018
Background: The overexpression of the chemokine receptor 4 (CXCR4) in different epithelial, mesenchymal, and hematopoietic cancers makes CXCR4 an attractive diagnostic and therapeutic target. However, targeting the CXCR4 receptor with small cyclic pentapeptide-based radiopharmaceuticals remains challenging because minor structural modifications within the ligand-linker-chelate structure often significantly affect the receptor affinity. Based on the excellent in vivo properties of CXCR4-directed pentapeptide [68Ga]pentixafor (cyclo(-D-Tyr-N-Me-D-Orn(AMB-DOTA)- L-Arg-L-2-Nal-Gly-)), this study aims to broaden the spectrum of applicable (radio)metal-labeled pentixafor analogs. Methods: Cyclic pentapeptides, based on the pentixafor scaffold, were synthesized by a combined solid- and solutionphase peptide synthesis. The CXCR4 receptor affinities of the cold reference compounds were determined in competitive binding assays using CXCR4-expressing Jurkat T - cell leukemia cells and [125I]FC131 as the radioligand. Results: Metalated pentixafor derivatives with cyclic and acyclic chelators were synthesized by solid-phase peptide

synthesis and evaluated in vitro. The resulting CXCR4 affinities (IC50) were highly dependent on the chelator and metal used. Two pentapeptides, Ga-NOTA and Bi-DOTA conjugates, offer an improved affinity compared to [68Ga]pentixafor. Conclusions: Based on the pentapeptide [68Ga]pentixafor, a broad range of metal-labeled analogs were investigated. The affinities of the new compounds were found to be strongly dependent on both the chelator and the metal used. Bi-labeled pentixafor showed high receptor affinity and seems to be a promising ligand for further preclinical evaluation and future α-emitter-based endoradiotherapy. Keywords: GPCR, CXCR4, [68Ga]pentixafor, Pentapeptide, DOTA, Chelator, Radiopharmaceutical, Tracer, Cancer

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## Evaluierung und prognostische Bedeutung multiparametrischer Magnetresonanz-Bildgebungsmethoden im PDAC

1Institut für allgemeine Pathologie und pathologische Anatomie, TU München, 2Institut für diagnostische und interventionelle Radiologie, Klinikum rechts der Isar, München, 3II. Medizinische Klinik, Klinikum rechts der Isar, München, 4Nuklearmedizinis, 2016, publiziert am 04.11.2016

## Co-clinical assessment of tumor cellularity in pancreatic cancer

2016, (pdf) publiziert am 03.11.2016

## [11C]Choline PET/CT in therapy response assessment of a neoadjuvant therapy in locally advanced and high risk prostate cancer before radical prostatectomy.

Oncotarget, 2016, DOI: 10.18632/oncotarget.11653 publiziert am 27.08.2016
PURPOSE:

Recent studies have shown promising results of neoadjuvant therapy in prostate cancer (PC). The aim of this study was to evaluate the potential of [11C]Choline PET/CT in therapy response monitoring after combined neoadjuvant docetaxel chemotherapy and complete androgen blockade in locally advanced and high risk PC patients.

RESULTS:

In [11C]Choline PET/CT there was a significant decrease of SUVmax and SUVmean (p = 0.004, each), prostate volume (p = 0.005) and PSA value (p = 0.003) after combined neoadjuvant therapy. MRI showed a significant prostate and tumor volume reduction (p = 0.003 and 0.005, respectively). Number of apoptotic cells was significantly higher in prostatectomy specimens of the therapy group compared to pretherapeutic biopsies and the control group (p = 0.02 and 0.003, respectively).

METHODS:

11 patients received two [11C]Choline PET/CT and MRI scans before and after combined neoadjuvant therapy followed by radical prostatectomy and pelvic lymph node dissection. [11C]Choline uptake, prostate and tumor volume, PSA value (before/after neoadjuvant therapy) and apoptosis (of pretherapeutic biopsy/posttherapeutic prostatectomy specimens of the therapy group and prostatectomy specimens of a matched control group without neoadjuvant therapy) were assessed and tested for differences and correlation using SPSS.

CONCLUSIONS:

The results showing a decrease in choline uptake after combined neoadjuvant therapy (paralleled by regressive and apoptotic changes in histopathology) confirm the potential of [11C]Choline PET/CT to monitor effects of neoadjuvant therapy in locally advanced and high risk PC patients. Further studies are recommended to evaluate its use during the course of neoadjuvant therapy for early response assessment.

## Immuno-PET Imaging of Engineered Human T Cells in Tumors

American Association for Cancer Research, 2016, doi: 10.1158/0008-5472.CAN-15-2784 publiziert am 15.07.2016

## Probing lactate secretion in tumours with hyperpolarised NMR

NMR Biomed, 2016, doi: 10.1002/nbm.3574. publiziert am 27.06.2016
Most tumours exhibit a high rate of glycolysis and predominantly produce energy by lactic acid fermentation. To maintain energy production and prevent toxicity, the lactate generated needs to be rapidly transported out of the cell. This is achieved by monocarboxylate transporters (MCTs), which therefore play an essential role in cancer metabolism and development. In vivo experiments were performed on eight male Fisher F344 rats bearing a subcutaneous mammary carcinoma after injection of hyperpolarised [1-(13) C]pyruvate. A Gd(III)DO3A complex that binds to pyruvate and its metabolites was used to efficiently destroy the extracellular magnetisation after hyperpolarised lactate had been formed. Moreover, a pulse sequence including a frequency-selective saturation pulse was designed so that the pyruvate magnetisation could be destroyed to exclude effects arising from further conversion. Given this preparation, metabolite transport out of the cell manifested as additional decay and apparent cell membrane transporter rates could thus be obtained using a reference measurement without a relaxation agent. In addition to slice-selective spectra, spatially resolved maps of apparent membrane transporter activity were acquired using a single-shot spiral gradient readout. A considerable increase in decay rate was detected for lactate, indicating rapid transport out of the cell. The alanine signal was unaltered, which corresponds to a slower efflux rate. This technique could allow for better understanding of tumour metabolism and progression, and enable treatment response measurements for MCT-targeted cancer therapies. Moreover, it provides vital insights into the signal kinetics of hyperpolarised [1-(13) C]pyruvate examinations.

## Noninvasive In Vivo Imaging and Biologic Characterization of Thyroid Tumors by ImmunoPET Targeting of Galectin-3

American Association for Cancer Research, 2016, doi: 10.1158/0008-5472.CAN-15-3046 publiziert am 20.06.2016

## Targeted positron emission tomography imaging of CXCR4 expression in patients with acute myeloid leukemia.

Haematologica, 2016, 10.3324/haematol.2016.142976 publiziert am 12.05.2016
Acute myeloid leukemia originates from leukemia-initiating cells that reside in the protective bone marrow niche. CXCR4/CXCL12 interaction is crucially involved in recruitment and retention of leukemia-initiating cells within this niche. Various drugs targeting this pathway have entered clinical trials. To evaluate CXCR4 imaging in acute myeloid leukemia, we first tested CXCR4 expression in patient-derived primary blasts. Flow cytometry revealed that high blast counts in patients with acute myeloid leukemia correlate with high CXCR4 expression. The wide range of CXCR4 surface expression in patients was reflected in cell lines of acute myeloid leukemia. Next, we evaluated the CXCR4-specific peptide Pentixafor by positron emission tomography imaging in mice harboring CXCR4 positive and CXCR4 negative leukemia xenografts, and in 10 patients with active disease. [(68)Ga]Pentixafor-positron emission tomography showed specific measurable disease in murine CXCR4 positive xenografts, but not when CXCR4 was knocked out with CRISPR/Cas9 gene editing. Five of 10 patients showed tracer uptake correlating well with leukemia infiltration assessed by magnetic resonance imaging. The mean maximal standard uptake value was significantly higher in visually CXCR4 positive patients compared to CXCR4 negative patients. In summary, in vivo molecular CXCR4 imaging by means of positron emission tomography is feasible in acute myeloid leukemia. These data provide a framework for future diagnostic and theranostic approaches targeting the CXCR4/CXCL12-defined leukemia-initiating cell niche.

## Variation of Specific Activities of 68Ga-Aquibeprin and 68Ga-Avebetrin Enables Selective PET Imaging of Different Expression Levels of Integrins α5β1 and αvβ3.

Society of Nuclear Medicine and Molecular Imaging, Inc., 2016, DOI: 10.2967/jnumed.116.173948 publiziert am 05.05.2016
68Ga-aquibeprin and 68Ga-avebetrin are tracers for selective in vivo mapping of integrins α5β1 and αvβ3, respectively, by PET. Because both tracers exhibit high affinity to their respective targets, the aim of this study was to investigate the influence of the specific activity of preparations of both tracers on in vivo imaging results.

METHODS:

Fully automated 68Ga labeling of 0.3 nmol of aquibeprin or avebetrin was done using buffered eluate fractions (600-800 MBq, pH 2) of an SnO2-based generator, affording the radiopharmaceuticals with specific activities greater than 1,000 MBq/nmol. Lower values ranging from 150 to 0.4 MBq/nmol were adjusted by addition of inactive compound (∼0.15-50 nmol) to the injected activity (∼20 MBq for PET, 5-7 MBq for biodistribution). For in vivo experiments, 6- to 12-wk-old female severe combined immunodeficiency mice bearing M21 xenografts (human melanoma, expressing both integrins α5β1 and αvβ3) were used. The expression density of integrin β3 was determined by immunohistochemistry on paraffin slices.

RESULTS:

For mass doses (specific activities) of less than 20 pmol (>1,000 MBq/nmol) and 1 nmol (20 MBq/nmol) per mouse, respectively, uptake of 68Ga-aquibeprin and 68Ga-avebetrin in M21 tumors dropped from 5.3 and 3.5 to 3.0 and 2.4 percentage injected dose per gram (%ID/g), respectively. When less than 20 pmol was applied, high uptake of 68Ga-aquibeprin in the eyes (4.5 %ID/g) or 68Ga-avebetrin in adrenals (25.9 %ID/g), respectively, were found, which was reduced by 90% and 65% (0.44 and 6.2 %ID/g, respectively), for doses of 1 nmol. The highest tumor-to-tissue ratios were observed both in ex vivo biodistribution and PET for comparably large doses, for example, 6 nmol (0.65 mg/kg) 68Ga-aquibeprin per mouse (3.5 MBq/nmol).

CONCLUSION:

Presumably because of their high affinities, 68Ga-aquibeprin and 68Ga-avebetrin allow for selective addressing of target sites with different integrin expression levels by virtue of adjusting specific activity, which can be exploited for visualization of low-level target expression or optimization of tumor-to-background contrast.

## Structure-Preserving Color Normalization and Sparse Stain Separation for Histological Images.

IEEE Trans Med Imaging, 2016, doi: 10.1109/TMI.2016.2529665 publiziert am 27.04.2016
Staining and scanning of tissue samples for microscopic examination is fraught with undesirable color variations arising from differences in raw materials and manufacturing techniques of stain vendors, staining protocols of labs, and color responses of digital scanners. When comparing tissue samples, color normalization and stain separation of the tissue images can be helpful for both pathologists and software. Techniques that are used for natural images fail to utilize structural properties of stained tissue samples and produce undesirable color distortions. The stain concentration cannot be negative. Tissue samples are stained with only a few stains and most tissue regions are characterized by at most one effective stain. We model these physical phenomena that define the tissue structure by first decomposing images in an unsupervised manner into stain density maps that are sparse and non-negative. For a given image, we combine its stain density maps with stain color basis of a pathologist-preferred target image, thus altering only its color while preserving its structure described by the maps. Stain density correlation with ground truth and preference by pathologists were higher for images normalized using our method when compared to other alternatives. We also propose a computationally faster extension of this technique for large whole-slide images that selects an appropriate patch sample instead of using the entire image to compute the stain color basis.

## Modeling Therapy Response and Spatial Tissue Distribution of Erlotinib in Pancreatic Cancer

American Association for Cancer Research., 2016, doi: 10.1158/1535-7163.MCT-15-0165 publiziert am 25.05.2016
Pancreatic ductal adenocarcinoma (PDAC) is likely the most aggressive and therapy-resistant of all cancers. The aim of this study was to investigate the emerging technology of matrixassisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) as a powerful tool to study drug delivery andspatial tissue distribution in PDAC. We utilized an established genetically engineered mouse model of spontaneous PDAC to examine the distribution of the small-molecule inhibitor erlotinib in healthy pancreas and PDAC. MALDI IMS was utilized on sections of single-dose or long-term–treated mice to measure drug tissue distribution. Histologic and statistical analyses were performed to correlate morphology, drug distribution, and survival. We found that erlotinib levels were significantly lower in PDAC compared with healthy tissue (P ¼ 0.0078). Survival of long-term–treated mice did not correlate with overall levels of erlotinib or with overall histologic tumor grade but did correlate both with the percentage of atypical glands in the cancer (P ¼ 0.021, rs ¼ 0.59) and the level of erlotinib in those atypical glands (P ¼ 0.019, rs ¼ 0.60). The results of this pilot study present MALDI IMS as a reliable technology to study drug delivery and spatial distribution of compounds in a preclinical setting and support drug imaging– based translational approaches. Mol Cancer Ther; 15(5); 1–8. 2016 AACR.

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## A Continuously Infused Microfluidic Radioassay System for the Characterization of Cellular Pharmacokinetics

Dept. Nuclear Medicine, Technische Universität München, Munich, Germany Dept. Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, USA, 2016, publiziert am 12.04.2016
Measurement of cellular tracer uptake is widely applied to understand the physiological status of cells and their interactions with imaging agents and pharmaceuticals. In-culture measurements have the advantage of less stress to cells. However, the tracer solution still needs to be loaded, unloaded and purged from the cell culture during the measurements. Here, we propose a continuously infused microfluidic radioassay (CIMR) system for continuous in-culture measurement of cellular uptake. The system was tested to investigate the influence of glucose concentration in cell culture medium on the 2-deoxy-2-(18F)fluoro-D-glucose (18F-FDG) uptake kinetics.

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## Complementary, Selective PET Imaging of Integrin Subtypes α5β1 and αvβ3 Using 68Ga-Aquibeprin and 68Ga-Avebetrin.

Journla of nuclear medicine, 2015, doi: 10.2967/jnumed.115.165720 publiziert am 03.12.2015

Despite in vivo mapping of integrin αvβ3 expression being thoroughly investigated in recent years, its clinical value is still not well defined. For imaging of angiogenesis, the integrin subtype α5β1 appears to be a promising target, for which purpose we designed the PET radiopharmaceutical (68)Ga-aquibeprin.

#### METHODS:

(68)Ga-aquibeprin was obtained by click-chemistry (CuAAC) trimerization of a α5β1 integrin-binding pseudopeptide on the triazacyclononane-triphosphinate (TRAP) chelator, followed by automated (68)Ga labeling. Integrin α5β1 and αvβ3 affinities were determined in enzyme linked immune sorbent assay on immobilized integrins, using fibronectin and vitronectin, respectively, as competitors. M21 (human melanoma)-bearing severe combined immunodeficient mice were used for biodistribution, PET imaging, and determination of in vivo metabolization. The expression of α5 and β3 subunits was determined by immunohistochemistry on paraffin sections of M21 tumors.

#### RESULTS:

(68)Ga-aquibeprin shows high selectivity for integrin α5β1 (50% inhibition concentration [IC50] = 0.088 nM) over αvβ3 (IC50 = 620 nM) and a pronounced hydrophilicity (log D = -4.2). Severe combined immunodeficient mice xenografted with M21 human melanoma were found suitable for in vivo evaluation, as M21 immunohistochemistry showed not only an endothelial and strong cytoplasmatic expression of the β3 integrin subunit but also an intense expression of the α5 integrin subunit particularly in the endothelial cells of intratumoral small vessels. Ex vivo biodistribution (90 min after injection) showed high uptake in M21 tumor (2.42 ± 0.21 percentage injected dose per gram), fast renal excretion, and low background; tumor-to-blood and tumor-to-muscle ratios were 10.6 ± 2.5 and 20.9 ± 2.4, respectively. (68)Ga-aquibeprin is stable in vivo; no metabolites were detected in mouse urine, blood serum, kidney, and liver homogenates 30 min after injection. PET imaging was performed for (68)Ga-aquibeprin and the previously described, structurally related c(RGDfK) trimer (68)Ga-avebetrin, which shows an inverse selectivity for integrin αvβ3 (IC50 = 0.22 nM) over α5β1 (IC50 = 39 nM). In vivo target specificity was proven by cross-competition studies; tumor uptake of either tracer was not affected by the coadministration of 40 nmol (∼5 mg/kg) of the respective other compound.

#### CONCLUSION:

(68)Ga-aquibeprin and (68)Ga-avebetrin are recommendable for complementary mapping of integrins α5β1 and αvβ3 by PET, allowing for future studies on the role of these integrins in angiogenesis, tumor progression, metastasis, and myocardial infarct healing.

## High-resolution MALDI-FT-ICR MS Imaging for the analysis of metabolites from formalin-fixed paraffin-embedded clinical tissue samples

The Journal of Pathology - Volume 237, Issue 1, 2015, doi: 10.1002/path.04560 publiziert am 01.12.2015
We present the first analytical approach to demonstrate the in situ imaging of metabolites from formalin-fixed paraffin-embedded (FFPE) human tissue samples. Using high-resolution Matrix-Assisted Laser Desorption/Ionization Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry Imaging (MALDI-FT-ICR MSI), we conducted a proof of principle experiment comparing metabolite measurements from FFPE and fresh frozen tissue sections, and found an overlap of 72% amongst 1700 m/z species. In particular, we observed conservation of biomedically relevant information at the metabolite level in FFPE tissues. In biomedical applications, we analysed tissues from 350 different cancer patients, and were able to discriminate between normal and tumour tissues, and different tumours from the same organ, and found an independent prognostic factor for patient survival. This study demonstrates the ability to measure metabolites in FFPE tissues using MALDI-FT-ICR MSI, which can then be assigned to histology and clinical parameters. Our approach is a major technical, histochemical and clinicopathological advance that highlights the potential for investigating diseases in archived FFPE tissues.

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## PET Imaging of Oncolytic VSV Expressing the Mutant HSV-1 Thymidine Kinase Transgene in a Preclinical HCC Rat Mode

The American Society of Gene & Cell Therapy, 2015, doi:10.1038/mt.2015.12 publiziert am 17.02.2015
Hepatocellular carcinoma (HCC) is the most predominant form of liver cancer and the third leading cause of cancerrelated death worldwide. Due to the relative ineffectiveness of conventional HCC therapies, oncolytic viruses have emerged as novel alternative treatment agents. Our previous studies have demonstrated significant prolongation of survival in advanced HCC in rats after oncolytic vesicular stomatitis virus (VSV) treatment. In this study, we aimed to establish a reporter system to reliably and sensitively image VSV in a clinically relevant model of HCC for clinical translation. To this end, an orthotopic, unifocal HCC model in immune-competent Buffalo rats was employed to test a recombinant VSV vector encoding for an enhanced version of the herpes simplex virus 1 (HSV-1) thymidine kinase (sr39tk) reporter, which would allow the indirect detection of VSV via positron emission tomography (PET). The resulting data revealed specific tracer uptake in VSV-HSV1-sr39tk–treated tumors. Further characterization of the VSV-HSV1-sr39tk vector demonstrated its optimal detection time-point after application and its detection limit via PET. In conclusion, oncolytic VSV expressing the HSV1-sr39tk reporter gene allows for highly sensitive in vivo imaging via PET. Therefore, this imaging system may be directly translatable and beneficial in further clinical applications. Received 8 August 2014; accepted 12 January 2015; advance onlinepublication 17 February 2015. doi:10.1038/mt.2015.

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## Early recognition of lung cancer by integrin targeted imaging in K-ras mouse model

Int. J. Cancer: 137, 1107–1118 (2015) C 2014 UICC, 2014, DOI: 10.1002/ijc.29372 publiziert am 02.12.2014
Non-small cell lung cancer is characterized by slow progression and high heterogeneity of tumors. Integrins play an important role in lung cancer development and metastasis and were suggested as a tumor marker; however their role in anticancer therapy remains controversial. In this work, we demonstrate the potential of integrin-targeted imaging to recognize early lesions in transgenic mouse model of lung cancer based on spontaneous introduction of mutated human gene bearing K-ras mutation. We conducted ex vivo and fluorescence molecular tomography-X-ray computed tomography (FMT-XCT) in vivo imaging and analysis for specific targeting of early lung lesions and tumors in rodent preclinical model for lung cancer. The lesions and tumors were characterized by histology, immunofluorescence and immunohistochemistry using a panel of cancer markers. Ex vivo, the integrintargeted fluorescent signal significantly differed between wild type lung tissue and K-ras pulmonary lesions (PL) at all ages studied The panel of immunofluorescence experiments demonstrated that PL, which only partially show cancer cell features weredetected by avb3-integrin targeted imaging. Human patient material analysis confirmed the specificity of target localization in different lung cancer types. Most importantly, small tumors in the lungs of 4-week-old animals could be noninvasively detected in vivo on the fluorescence channel of FMT-XCT. Our findings demonstrated avb3-integrin targeted fluorescent imaging to specifically detect premalignant pleural lesions in K-ras mice. Integrin targeted imaging may find application areas in preclinical research and clinical practice, such as early lung cancer diagnostics, intraoperative assistance or therapy monitoring.

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## Spatially Resolved Quantification of Gadolinium(III)-Based Magnetic Resonance Agents in Tissue by MALDI Imaging Mass Spectrometry after In Vivo MRI

Angwandte Chemie Int. Ed. 2015, 54, 1 – 6, 2014, DOI: 10.1002/anie.201410555 publiziert am 27.02.2015
Gadolinium(III)-based contrast agents improve the sensitivity and specificity of magnetic resonance imaging (MRI), especially when targeted contrast agents are applied. Because of nonlinear correlation between the contrast agent concentration in tissue and the MRI signal obtained in vivo, quantification of certain biological or pathophysiological processes by MRI remains a challenge. Up to now, no technology has been able to provide a spatially resolved quantification of MRI agents directly within the tissue, which would allow a more precise verification of in vivo imaging results. MALDI imaging mass spectrometry for spatially resolved in situ quantification of gadolinium(III) agents, in correlation to in vivo MRI, were evaluated. Enhanced kinetics of Gadofluorine M were determined dynamically over time in a mouse model of myocardial infarction. MALDI imaging was able to corroborate the in vivo imaging MRI signals and enabled in situ quantification of the gadolinium probe with high spatial resolution.

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## High-resolution metabolite imaging of light and dark treated retina using MALDI-FTICR mass spectrometry

Proteomics, 2014, 913-923, DOI 10.1002 / pmic.201300407 publiziert am 14.04.2014
MS imaging (MSI) is a valuable tool for diagnostics and systems biology studies, being a highly sensitive, label-free technique capable of providing comprehensive spatial distribution of different classes of biomolecules. The application of MSI to the study of endogenous compounds has received considerable attention because metabolites are the result of the interactions of a biosystem with its environment. MSI can therefore enhance understanding of disease mechanisms and elucidate mechanisms for biological variation. We present the in situ comparative metabolomics imaging data for analyses of light- and dark-treated retina using MALDI-FTICR. A wide variety of tissue metabolites were imaged at a high spatial resolution. These include nucleotides, central carbon metabolism pathway intermediates, 2-oxocarboxylic acid metabolism, oxidative phosphorylation, glycerophospholipid metabolism, and cysteine and methionine metabolites. The high lateral resolution enabled the differentiation of retinal layers, allowing determination of the spatial distributions of different endogenous compounds. A number of metabolites demonstrated differences between light and dark conditions. These ﬁndings add to the understanding of metabolic activity in the retina

## Non-Negative Matrix Factorization Based Input Function Extraction for Mouse Imaging in Small Animal PET Comparison with Arterial Blood Sampling and Factor Analysis

J Mol Imaging Dynam, 2012, publiziert am 27.04.2012

Objectives

Retrieving the accurate time-tracer activity concentration curve of the blood (arterial inputfunction) is mandatory for performing bio kinetic model analysis of dynamic PET data. Especially in small rodents, gathering the input function remains an active area of research äs no generally applicable solution was found so far. While surgically catheterizing biood vessels of rodents is possible, it is labour intensive and time resolution of blood sampling is restricted due to the limited amount of overall blood and the procedure of blood withdrawal itself. Obtaining the input function from the PET images themselves seems thus to be favourable, but suffers from several factors, one of them being spill-in of adjacent tissues. Particularly in mice and for [18F]FDG, the spill-in complicates using the time-activity curve (TAG) from a region of interest (ROI) over the left ventricle (LV) because the Signal of the ROI contains contributions from both, myocardial uptake äs well äs arterial blood activity. We propose non-negative matrix factorization (NMF) äs an image based algorithm for separating myocardial tracer concentration from the blood input function. The aim of this study was to evaluate the potential of NMF äs an image based algorithm for retrieving the input function by comparison with blood sampling and Factor Analysis (FA).

Method

The femoral arteries of eight mice were surgically catheterized. With the injection of [1SF]FDG, a 60 minute PET scan was started during which arterial blood samples were manually drawn from the catheter. For analysis, NMF and FA were performed in a ROI placed over the LV. The NMF algorithm shares similarities with principal component analysis and FA, the advantage over the later two being its non-negativity constraint. For normalization of the NMF extracted curve, the peak value of tracer activity in an early irnage of the LV and a late blood sample was used. The normalized NMF curve was visually compared to the TAG retrieved from the blood samples and to the FA retrieved TAG. For a quantitative comparison of performance, Pearson correlation and square-root of sum of squares (RSS) between NMF/FA and blood sampling curves was calculated.

Results

TAG based on NMF, FAand arterial blood samples were obtained and compared in all 8 mice. The NMF derived curves described the blood sampling based curves visually significantly better than FA. Pearson correlation between NMF and blood sampling curves ranged from 0.21 to 0.92 with an average of 0.69. Pearson correlation for FA ranged from 0.46 to 0.81 with an average of 0.65. Mean RSS was 2.70E + 006 for NMF and 3.40E + 006 for FA.

Conclusion

In the examined Parameters, visua! accordance, Pearson correlation and RSS, NMF performs superior to FA and seems to be a promising method for the extraction of the input function from PET images of small rodents without the need for arterial blood sampling.

## 68Ga-NODAGA-RGD is a suitable substitute for 18F-Galacto-RGD and can be produced with high specific activity in a cGMP/GRP compliant automated process

Nuclear Medicine and Biology, 2012, Available online, publiziert am 22.03.2012

Introduction

18F-Galacto-cyclo(RGDfK) is a well investigated tracer for imaging of ανβ3 expression in vivo, but suffers from the drawback of a time consuming multistep synthesis that can hardly be established under GMP conditions. In this study, we present a direct comparison of the pharmacokinetic properties of this tracer with 68Ga-NODAGA-cyclo(RGDyK), in order to assess its potential as an alternative for 18F-Galacto-cyclo(RGDfK).

Methods

68Ga labeling of NODAGA-cyclo(RGDyK) was done in full automation using HEPES-buffered eluate of an SnO2 based 68Ga-generator. Using M21 (human melanoma) xenografted BALB/c nude mice, biodistribution studies and micro-PET scans were performed for both 18F-Galacto-cyclo(RGDfK) and 68Ga-NODAGA-cyclo(RGDyK), and for the latter, in vivo stability was assessed. IC50 was determined in a displacement assay on M21 cells against 125I-echistatin.

Results

68Ga-NODAGA-cyclo(RGDyK) was produced with high specific activity (routinely ca. 500 GBq/μmol) within 15 min. IC50 values are similar for both substances. Tracer uptake was similar in ανβ3 positive tumors (1.45% ± 0.11% ID/g and 1.35% ± 0.53% ID/g for 68Ga-NODAGA-RGD and 18F-Galacto-RGD, respectively) as well as for all other organs and tissues, with the exception of gall bladder and intestines, where 18F-Galacto-cyclo(RGDfK) uptake was significantly higher, which can be explained by the higher hydrophilicity of 68Ga-NODAGA-cyclo(RGDyK) (logP = −4.0 vs. − 3.2 for 18F-Galacto-RGD). Only intact tracer was detected 30 min p.i. in organs and tumor; however, minor amounts of metabolites were found in the urine (6% of total urine activity).

Conclusion

68Ga-labeling of NODAGA-RGD can be performed rapidly and efficiently within 15 min in a GMP compliant process. Similar preclinical results were obtained in comparison with 18F-Galacto-RGD. Therefore, 68Ga-NODAGA-cyclo(RGDyK) is a suitable replacement for 18F-Galacto-cyclo(RGDfK).

## Origin of pancreatic ductal adenocarcinoma from atypical flat lesions: a comparative study in transgenic mice and human tissues

J Pathol., 2011, doi. 10.1002, path.3017 publiziert am 07.10.2011

Pancreatic ductal adenocarcinoma (PDAC) and its precursor lesions, pancreatic intraepithelial neoplasia (PanIN), display a ductal phenotype. However, there is evidence in genetically defined mouse models for PDAC harbouring a mutated kras under the control of a pancreas-specific promoter that ductal cancer might arise in the centroacinar-acinar region, possibly through a process of acinar-ductal metaplasia (ADM). In order to further elucidate this model of PDAC development, an extensive expression analysis and molecular characterization of the putative and already established (PanIN) precursor lesions were performed in the Kras$^{G{\it{\bf{12}}}D/+}$ ; Ptf1a-Cre$^{ex{\it{\bf{1}}}/+}$ mouse model and in human tissues, focusing on lineage markers, developmental pathways, cell cycle regulators, apomucins, and stromal activation markers. The results of this study show that areas of ADM are very frequent in the murine and human pancreas and represent regions of increased proliferation of cells with precursor potential. Moreover, atypical flat lesions originating in areas of ADM are the most probable precursors of PDAC in the Kras$^{G{\it{\bf{12}}}D/+}$; Ptf1a-Cre$^{ex{\it{\bf{1}}}/+}$ mice and similar lesions were also found in the pancreas of three patients with a strong family history of PDAC. In conclusion, PDAC development in Kras$^{G{\it{\bf{12}}}D/+}$; Ptf1a-Cre$^{ex{\it{\bf{1}}}/+}$ mice starts from ADM and a similar process might also take place in patients with a strong family history of PDAC. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

## Classification of HER2 Receptor Status in Breast Cancer Tissues by MALDI Imaging Mass Spectrometry

J Proteome Res, 2010, [Epub ahead of print], publiziert am 05.03.2010

Clinical laboratory testing for HER2 status in breast cancer tissues is critically important for therapeutic decision making. Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) is a powerful tool for investigating proteins through the direct and morphology-driven analysis of tissue sections. We hypothesized that MALDI-IMS may determine HER2 status directly from breast cancer tissues. Breast cancer tissues (n=48) predefined for HER2 status were subjected to MALDI-IMS and protein profiles were obtained through direct analysis of tissue sections. Protein identification was performed by tissue micro-extraction and fractionation followed by top-down tandem mass spectrometry. A discovery and an independent validation set were used to predict HER2 status by applying proteomic classification algorithms. We found that specific protein/peptide expression changes strongly correlated with the HER2 over-expression. Among these, we identified m/z 8404 as Cysteine-rich-intestinal-protein 1. The proteomic signature was able to accurately define HER2-positive from HER2-negative tissues achieving high values for sensitivity of 83%, for specificity of 92% and an overall accuracy of 89%. Our results underscore the potential of MALDI-IMS proteomic algorithms for morphology-driven tissue diagnostics such as HER2 testing and show that MALDI-IMS can reveal biologically significant molecular details from tissues which are not limited to traditional high-abundance proteins.

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