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Molecular imaging has experienced enormous advancements in the areas of imaging technology, imaging probe and contrast development, and data quality, as well as machine learning-based data analysis. Positron emission tomography (PET) and its combination with computed tomography (CT) or magnetic resonance imaging (MRI) as a multimodality PET–CT or PET–MRI system offer a wealth of molecular, functional and morphological data with a single patient scan. Despite the recent technical advances and the availability of dozens of disease-specific contrast and imaging probes, only a few parameters, such as tumour size or the mean tracer uptake, are used for the evaluation of images in clinical practice. Multiparametric in vivo imaging data not only are highly quantitative but also can provide invaluable information about pathophysiology, receptor expression, metabolism, or morphological and functional features of tumours, such as pH, oxygenation or tissue density, as well as pharmacodynamic properties of drugs, to measure drug response with a contrast agent. It can further quantitatively map and spatially resolve the intertumoural and intratumoural heterogeneity, providing insights into tumour vulnerabilities for target-specific therapeutic interventions. Failure to exploit and integrate the full potential of such powerful imaging data may lead to a lost opportunity in which patients do not receive the best possible care. With the desire to implement personalized medicine in the cancer clinic, the full comprehensive diagnostic power of multiplexed imaging should be utilized.

We recently reported that miR-146a is differentially expressed in ALK+ and ALK− anaplastic large cell lymphoma (ALCL). In this study, the downstream targets of miR-146a in ALK+ ALCL were investigated by transcriptome analysis, identifying CD147as potential target gene. Because CD147 is differentially expressed in ALK+ ALCL versus ALK− ALCL and normal T cells, this gene emerged as a strong candidate for the pathogenesis of this tumor. Here we demonstrate that CD147 is a direct target of miR-146 and contributes to the survival and proliferation of ALK+ ALCL cells in vitro and to the engraftment and tumor growth in vivo in an ALK+ ALCL-xenotransplant mouse model. CD147 knockdown in ALK+ ALCL cells resulted in loss of monocarboxylate transporter 1 (MCT1) expression, reduced glucose consumption and tumor growth retardation, as demonstrated by [18F]FDG-PET/MRI analysis. Investigation of metabolism in vitro and in vivo supported these findings, revealing reduced aerobic glycolysis and increased basal respiration in CD147 knockdown. In conclusion, our findings indicate that CD147 is of vital importance for ALK+ ALCL to maintain the high energy demand of rapid cell proliferation, promoting lactate export, and tumor growth. Furthermore, CD147 has the potential to serve as a novel therapeutic target in ALK+ ALCL, and warrants further investigation.

Preclinical models of neurological diseases and gene therapy are essential for neurobiological research. However, the evaluation of such models lacks reliable reporter systems for use with noninvasive imaging methods. Here, we report the development of a reporter system based on the CLIP-tag enzyme and [18F]pFBC, an 18F-labeled covalent CLIP-tag-ligand synthesized via a DoE-optimized and fully automated process. We demonstrated its specificity using a subcutaneous xenograft model and a model of viral vector-mediated brain gene transfer by engineering HEK293 cells and striatal neurons to express membrane-tethered CLIP-tag protein. After in vitrocharacterization of the reporter, mice carrying either CLIP-tag expressing or control subcutaneous xenografts underwent dynamic [18F]pFBC PET imaging. The CLIP-tag expressing xenografts showed a significantly higher uptake than control xenografts (tumor-to-muscle ratio 5.0 vs 1.7, p = 0.0379). In vivo, metabolite analysis by radio-HPLC from plasma and brain homogenates showed only one radio-metabolite in plasma and none in the brain. In addition, [18F]pFBC showed fast uptake and rapid clearance from the brain in animals injected with adeno-associated virus (AAV)-CLIP in the right striatum but no right-to-left (R-L) uptake difference in the striata in the acquired PET data. In contrast, autoradiography showed a clear accumulation of radioactivity in the AAV-CLIP-injected right striatum compared to the sham-injected left striatum control. CLIP-tag expression and brain integrity were verified by immunofluorescence and light sheet microscopy. In conclusion, we established a novel reporter gene system for PET imaging of gene expression in the brain and periphery and demonstrated its potential for a wide range of applications, particularly for neurobiological research and gene therapy with viral vectors.

Generated by gram-negative bacteria, lipopolysaccharides (LPSs) are one of the most abundant and potent immunomodulatory substances present in the intestinal lumen. Interaction of agonistic LPS with the host myeloid-differentiation-2/Toll-like receptor 4 (MD-2/TLR4) receptor complex results in nuclear factor κB (NF-κB) activation, followed by the robust induction of pro-inflammatory immune responses. Here we have isolated LPS from a common gut commensal, Bacteroides vulgatusmpk (BVMPK), which provides only weak agonistic activity. This weak agonistic activity leads to the amelioration of inflammatory immune responses in a mouse model for experimental colitis, and it was in sharp contrast to strong agonists and antagonists. In this context, the administration of BVMPK LPS into mice with severe intestinal inflammation re-established intestinal immune homeostasis within only 2 weeks, resulting in the clearance of all symptoms of inflammation. These inflammation-reducing properties of weak agonistic LPS are grounded in the induction of a special type of endotoxin tolerance via the MD-2/TLR4 receptor complex axis in intestinal lamina propria CD11c+cells. Thus, weak agonistic LPS represents a promising agent to treat diseases involving pathological overactivation of the intestinal immune system, e.g., in inflammatory bowel diseases.

Radiosynthesis of [1-11C]acetate is well described in literature, but all syntheses either require adaptations in complex commercial synthesizers or rely on closed-source hardware and software control. Arduino microcontrollers are ideal for the compact, flexible, and inexpensive control of low-complexity hardware, making them particularly suited for radiochemistry where operation in space-limited shielded hot cells is mandatory. We established a [1-11C]acetate radiosynthesis module for combination with a [11C]MeI module available in almost every lab working with 11C. Its small footprint even enables back-to-back production in a hot cell already occupied by other modules. Using this setup, we achieved a reliable and flexible supply of this tracer, with radiochemical yields of 51.4 ± 28.2% and radiochemical purities (RCPs) of 94.4 ± 6.7% (n= 9) in a synthesis time of 15 minutes. Positron emission tomography (PET) and biodistribution analysis demonstrated low background uptake in healthy mice, with highest uptake in liver and kidneys. Arduino microcontrollers have become valuable and versatile tools in our lab for the automatization of low-complexity procedures not requiring full-blown commercial radiochemistry synthesizers, as showcased here for the production of [1-11C]acetate.

Radiosynthesis of [1-11C]acetate is well described in literature, but all syntheses either require adaptations in complex commercial synthesizers or rely on closed-source hardware and software control. Arduino microcontrollers are ideal for the compact, flexible, and inexpensive control of low-complexity hardware, making them particularly suited for radiochemistry where operation in space-limited shielded hot cells is mandatory. We established a [1-11C]acetate radiosynthesis module for combination with a [11C]MeI module available in almost every lab working with 11C. Its small footprint even enables back-to-back production in a hot cell already occupied by other modules. Using this setup, we achieved a reliable and flexible supply of this tracer, with radiochemical yields of 51.4 ± 28.2% and radiochemical purities (RCPs) of 94.4 ± 6.7% (n= 9) in a synthesis time of 15 minutes. Positron emission tomography (PET) and biodistribution analysis demonstrated low background uptake in healthy mice, with highest uptake in liver and kidneys. Arduino microcontrollers have become valuable and versatile tools in our lab for the automatization of low-complexity procedures not requiring full-blown commercial radiochemistry synthesizers, as showcased here for the production of [1-11C]acetate.

A potential major application of simultaneous avalanche photodiode–based positron emission tomography (PET)magnetic resonance imaging (MRI) systems are quantitative brain studies for cerebral blood flow measurements in combination with blood-oxygen-level–dependent or perfusion MRI, requiring a high performance for both modalities. Thus, we evaluated PET quantification accuracy and homogeneity for 2 different simultaneous PETMRI systems (whole–body and brain scanner) compared with those of a state-of-the-art PET detector (PETcomputed tomography) using phantom studies. In addition, we investigated the long-term stability of PET and quality of functional MRI measurements of a clinical whole-body PETMRI scanner.

The aim of this study was to test and demonstrate the feasibility of diffusion tensor imaging (DTI) with a hybrid positron emission tomography (PET)/magnetic resonance imaging system for simultaneous PET and magnetic resonance (MR) data acquisition.

Signaling through tumor necrosis factor receptor 1 (TNFR1) controls bacterial infections and the induction of inflammatory Th1 cell–mediated autoimmune diseases. By dissecting Th1 cell–mediated delayed-type hypersensitivity responses (DTHRs) into single steps, we localized a central defect to the missing TNFR1 expression by endothelial cells (ECs). Adoptive transfer and mast cell knockin experiments into KitW/KitW-v, TNF−/−, and TNFR1−/−mice showed that the signaling defect exclusively affects mast cell–EC interactions but not T cells or antigen-presenting cells. As a consequence, TNFR1−/−mice had strongly reduced mRNA and protein expression of P-selectin, E-selectin, ICAM-1, and VCAM-1 during DTHR elicitation. In consequence, intravital fluorescence microscopy revealed up to 80% reduction of leukocyte rolling and firm adhesion in TNFR1−/−mice. As substitution of TNF−/−mice with TNF-producing mast cells fully restored DTHR in these mice, signaling of mast cell-derived TNF through TNFR1-expressing ECs is essential for the recruitment of leukocytes into sites of inflammation.

Signaling through tumor necrosis factor receptor 1 (TNFR1) controls bacterial infections and the induction of inflammatory Th1 cell–mediated autoimmune diseases. By dissecting Th1 cell–mediated delayed-type hypersensitivity responses (DTHRs) into single steps, we localized a central defect to the missing TNFR1 expression by endothelial cells (ECs). Adoptive transfer and mast cell knockin experiments into KitW/KitW-v, TNF−/−, and TNFR1−/− mice showed that the signaling defect exclusively affects mast cell–EC interactions but not T cells or antigen-presenting cells. As a consequence, TNFR1−/− mice had strongly reduced mRNA and protein expression of P-selectin, E-selectin, ICAM-1, and VCAM-1 during DTHR elicitation. In consequence, intravital fluorescence microscopy revealed up to 80% reduction of leukocyte rolling and firm adhesion in TNFR1−/− mice. As substitution of TNF−/− mice with TNF-producing mast cells fully restored DTHR in these mice, signaling of mast cell-derived TNF through TNFR1-expressing ECs is essential for the recruitment of leukocytes into sites of inflammation.

In vivo optical instruments designed for small animal imaging generally measure the integrated light intensity across a broad band of wavelengths, or make measurements at a small number of selected wavelengths, and primarily use any spectral information to characterize and remove autofluorescence. We have developed a flexible hyperspectral imaging instrument to explore the use of spectral information to determine the 3D source location for in vivo fluorescence imaging applications. We hypothesize that the spectral distribution of the emitted fluorescence signal can be used to provide additional information to 3D reconstruction algorithms being developed for optical tomography. To test this hypothesis, we have designed and built an in vivo hyperspectral imaging system, which can acquire data from 400 to 1000 nm with 3 nm spectral resolution and which is flexible enough to allow the testing of a wide range of illumination and detection geometries. It also has the capability to generate a surface contour map of the animal for input into the reconstruction process. In this paper, we present the design of the system, demonstrate the depth dependence of the spectral signal in phantoms and show the ability to reconstruct 3D source locations using the spectral data in a simple phantom. We also characterize the basic performance of the imaging system.

Detectors used for positron emission tomography (PET) provide fast, randomly distributed signals that need to be digitized for further processing. One possibility is to sample the signals at the peak initiated by a trigger from a constant fraction discriminator (CFD). For PET detectors, simultaneous acquisition of many channels is often important. To develop and evaluate novel PET detectors, a flexible, relatively low cost and high performance laboratory data acquisition (DAQ) system is therefore required. The use of dedicated DAQ systems, such as a multi-channel analysers (MCAs) or continuous sampling boards at high rates, is expensive. This work evaluates the suitability of well-priced peripheral component interconnect (PCI)-based 8-channel DAQ boards (PD2-MFS-8 2M/14 and PD2-MFS-8-500k/14, United Electronic Industries Inc., Canton, MA, USA) for signal acquisition from novel PET detectors. A software package was developed to access the board, measure basic board parameters, and to acquire, visualize, and analyse energy spectra and position profiles from block detectors. The performance tests showed that the boards input linearity is >99.2% and the standard deviation is <9 mV at 10 V for constant signals. Synchronous sampling of multiple channels and external synchronization of more boards are possible at rates up to 240 kHz per channel. Signals with rise times as fast as 130 ns (<2 V amplitude) can be acquired without slew rate effects. However, for signals with amplitudes of up to 5 V, a rise time slower than 250 ns is required. The measured energy resolution of a lutetium oxyorthosilicate (LSO)-photomultiplier tube (PMT) detector with a 22Na source was 14.9% (FWHM) at 511 keV and is slightly better than the result obtained with a high-end single channel MCA (8000A, Amptek, USA) using the same detector (16.8%). The crystals (1.2 × 1.2 × 12 mm3) within a 9 × 9 LSO block detector could be clearly separated in an acquired position profile. Thus, these boards are well suited for data acquisition with novel detectors developed for nuclear imaging.

Given the clinical potential of poly(ADP-ribose) polymerases (PARP) imaging for the detection and stratification of various cancers, the development of novel PARP imaging probes with improved pharmacological profiles over established PARP imaging agents is warranted. Here, we present a novel 18F-labeled PARP radiotracer based on the clinically superior PARP inhibitor talazoparib. An automated radiosynthesis of [18F]talazoparib (RCY: 13 ± 3.4%; n= 4) was achieved using a “design of experiments” (DoE) optimized copper-mediated radiofluorination reaction. The chiral product was isolated from the reaction mixture using 2D reversed-phase/chiral radio-HPLC (>99% ee). (8S,9R)-[18F]Talazoparib demonstrated PARP binding in HCC1937 cells in vitroand showed an excellent tumor-to-blood ratio in xenograft-bearing mice (10.2 ± 1.5). Additionally, a favorable pharmacological profile in terms of excretion, metabolism, and target engagement was observed. This synthesis of [18F]talazoparib exemplifies how DoE can enable the radiosyntheses of synthetically challenging radiolabeled compounds of high interest to the imaging community.

T cells, engineered to express chimeric antigen receptors (CAR), are capable to generate an extremely potent and highly specific immune response against defined surface-expressed antigens. The very same features however hinder a more general clinical application, first because on-target off-tumor toxicity can cause life-threatening damage to vitally important healthy tissue and second because heterogeneity as well as plasticity of tumor tissue circumvent elimination through modulation or loss of target epitopes.

Stimulating the immune system to attack cancer is a promising approach, even for the control of advanced cancers. Several cytokines that promote interferon-γ-dominated immune responses show antitumor activity, with interleukin 12 (IL-12) being of major importance. Here, we used an antibody-IL-12 fusion protein (NHS-IL12) that binds histones of necrotic cells to treat human sarcoma in humanized mice. Following sarcoma engraftment, NHS-IL12 therapy was combined with either engineered IL-7 (FcIL-7) or IL-2 (IL-2MAB602) for continuous cytokine bioavailability. NHS-IL12 strongly induced innate and adaptive antitumor immunity when combined with IL-7 or IL-2. NHS-IL12 therapy significantly improved survival of sarcoma-bearing mice and caused long-term remissions when combined with IL-2. NHS-IL12 induced pronounced cancer cell senescence, as documented by strong expression of senescence-associated p16INK4aand nuclear translocation of p-HP1γ, and permanent arrest of cancer cell proliferation. In addition, this cancer immunotherapy initiated the induction of myogenic differentiation, further promoting the hypothesis that efficient antitumor immunity includes mechanisms different from cytotoxicity for efficient cancer control in vivo.

No relevant conflicts of interest to declare.

Abstract 2905