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Introduction: Measurement of repeatability and reproducibility (R&R) is necessary to realize the full potential of positron emission tomography (PET). Several studies have evaluated the reproducibility of PET using 18F-FDG, the most common PET tracer used in oncology, but similar studies using other PET tracers are scarce. Even fewer assess agreement and R&R with statistical methods designed explicitly for the task. 18F-(2S, 4R)-4-fluoro-glutamine (18F-Gln) is a PET tracer designed for imaging glutamine uptake and metabolism. This study illustrates high reproducibility and repeatability with 18F-Gln for in vivo research. Methods: Twenty mice bearing colorectal cancer cell line xenografts were injected with ~9 MBq of 18F-Gln and imaged in an Inveon microPET. Three individuals analyzed the tumor uptake of 18F-Gln using the same set of images, the same image analysis software, and the same analysis method. Scans were randomly re-ordered for a second repeatability measurement 6 months later. Statistical analyses were performed using the methods of Bland and Altman (B&A), Gauge Reproducibility and Repeatability (Gauge R&R), and Lin's Concordance Correlation Coefficient. A comprehensive equivalency test, designed to reject a null hypothesis of non-equivalence, was also conducted. Results: In a two-way random effects Gauge R&R model, variance among mice and their measurement variance were 0.5717 and 0.024. Reproducibility and repeatability accounted for 31% and 69% of the total measurement error, respectively. B&A repeatability coefficients for analysts 1, 2, and 3 were 0.16, 0.35, and 0.49. One-half B&A agreement limits between analysts 1 and 2, 1 and 3, and 2 and 3 were 0.27, 0.47, and 0.47, respectively. The mean square deviation and total deviation index were lowest for analysts 1 and 2, while coverage probabilities and coefficients of the individual agreement were highest. Finally, the definitive agreement inference hypothesis test for equivalency demonstrated that all three confidence intervals for the average difference of means from repeated measures lie within our a priori limits of equivalence (i.e. ± 0.5%ID/g). Conclusions: Our data indicate high individual analyst and laboratory-level reproducibility and repeatability. The assessment of R&R using the appropriate methods is critical and should be adopted by the broader imaging community. [ABSTRACT FROM AUTHOR]

Early response assessment is critical for personalizing cancer therapy. Emerging therapeutic regimens with encouraging results in the wild-type (WT) KRAS colorectal cancer (CRC) setting include inhibitors of epidermal growth factor receptor (EGFR) and glutaminolysis. Towards predicting clinical outcome, this preclinical study evaluated non-invasive positron emission tomography (PET) with (4S)-4-(3-[18F]fluoropropyl)-L-glutamic acid ([18F]FSPG) in treatment-sensitive and treatment-resistant WT KRAS CRC patient-derived xenografts (PDXs). Tumor-bearing mice were imaged with [18F]FSPG PET before and one week following the initiation of treatment with either EGFR-targeted monoclonal antibody (mAb) therapy, glutaminase inhibitor therapy, or the combination. Imaging was correlated with tumor volume and histology. In PDX that responded to therapy, [18F]FSPG PET was significantly decreased from baseline at 1-week post-therapy, prior to changes in tumor volume. In contrast, [18F]FSPG PET was not decreased in non-responding PDX. These data suggest that [18F]FSPG PET may serve as an early metric of response to EGFR and glutaminase inhibition in the WT KRAS CRC setting. [ABSTRACT FROM AUTHOR]

The design, synthesis and biological application of a new phosphine probe is described for real-time imaging of cell-surface glycans by using bioluminescence. The first phosphine-luciferin probe is prepared for use in real-time bioluminescence imaging (BLI) and has shown that azide-labeled cell-surface glycans is imaged with the reagent by using concentrations as low as single digit nanomolar.

Purpose: There is an urgent need for the development of novel positron emission tomography (PET) tracers for glioma imaging. In this study, we developed a novel PET probe ([18F]VUIIS1018A) by targeting translocator protein (TSPO), an imaging biomarker for glioma. The purpose of this preclinical study was to evaluate this novel TSPO probe for glioma imaging.Procedures: In this study, we synthesized [19F]VUIIS1018A and the precursor for radiosynthesis of [18F]VUIIS1018A. TSPO binding affinity was confirmed using a radioligand competitive binding assay in C6 glioma cell lysate. Further, dynamic imaging studies were performed in rats using a microPET system. These studies include displacement and blocking studies for ligand reversibility and specificity evaluation, and compartment modeling of PET data for pharmacokinetic parameter measurement using metabolite-corrected arterial input functions and PMOD.Results: Compared to previously reported TSPO tracers including [18F]VUIIS1008 and [18F]DPA-714, the novel tracer [18F]VUIIS1018A demonstrated higher binding affinity and BPND. Pretreatment with the cold analog [19F]VUIIS1018A could partially block tumor accumulation of this novel tracer. Further, compartment modeling of this novel tracer also exhibited a greater tumor-to-background ratio, a higher tumor binding potential and a lower brain binding potential when compared with other TSPO probes, such as [18F]DPA-714 and [18F]VUIIS1008.Conclusions: These studies illustrate that [18F]VUIIS1018A can serve as a promising TSPO PET tracer for glioma imaging and potentially imaging of other solid tumors. [ABSTRACT FROM AUTHOR]

To increase the achievement of negative R0 surgical margins and increase the low survival rates of pancreatic cancer, improvements in assessing tumor margins during surgical resections are needed. This can be accomplished by using pancreatic cancer-targeted fluorescence molecular imaging agents to intraoperatively detect tumor margins in real time. Because Toll-like receptor 2 (TLR2) is broadly expressed among many cancer types including pancreatic adenocarcinomas, a high-affinity TLR2-targeted fluorescence molecular imaging agent (TLR2L-800) was developed. We investigate the potential for increased survival by employing real-time intraoperative tumor detection in a preclinical orthotopic human pancreatic xenograft tumor model using TLR2L-800. Three cohorts of nude mice bearing orthotopic human pancreatic xenograft tumors were intravenously injected with TLR2L-800. At 24 hours postinjection, one cohort underwent in vivo fluorescence-guided surgical removal of tumors using a real-time fluorescence imaging platform, a second cohort underwent visible light surgery (VLS), and a third cohort did not undergo surgery. A fourth, nontumor-bearing cohort was administered TLR2L-800 with no surgery. At 41 days postsurgery, the survival rates were 53% for the fluorescence-guided surgery (FGS) group and 0% for both the VLS and the tumor-bearing no-surgery group. The overall 200-day survival rate of 35% for the FGS group was significant compared with 0% for the VLS group (P value = 0.0018). This study demonstrates the potential of increasing disease-free survival for patients with pancreatic cancer by increasing the attainment of R0 margins using a novel tumor-targeted lipopeptide ligand-based fluorescence molecular imaging agent, TLR2L-800, during real-time FGS., Significance: Human TLR2 is broadly expressed among pancreatic adenocarcinomas, and the highly specific TLR2L-800 fluorescence molecular imaging agent has potential for use in fluorescence-guided surgery to increase R0 margins and improve patient survival., (©2024 The Authors; Published by the American Association for Cancer Research.)

Early response assessment is critical for personalizing cancer therapy. Emerging therapeutic regimens with encouraging results in the wild-type (WT) KRAS colorectal cancer (CRC) setting include inhibitors of epidermal growth factor receptor (EGFR) and glutaminolysis. Towards predicting clinical outcome, this preclinical study evaluated non-invasive positron emission tomography (PET) with (4S)-4-(3-[ 18 F]fluoropropyl)-L-glutamic acid ([ 18 F]FSPG) in treatment-sensitive and treatment-resistant WT KRAS CRC patient-derived xenografts (PDXs). Tumor-bearing mice were imaged with [ 18 F]FSPG PET before and one week following the initiation of treatment with either EGFR-targeted monoclonal antibody (mAb) therapy, glutaminase inhibitor therapy, or the combination. Imaging was correlated with tumor volume and histology. In PDX that responded to therapy, [ 18 F]FSPG PET was significantly decreased from baseline at 1-week post-therapy, prior to changes in tumor volume. In contrast, [ 18 F]FSPG PET was not decreased in non-responding PDX. These data suggest that [ 18 F]FSPG PET may serve as an early metric of response to EGFR and glutaminase inhibition in the WT KRAS CRC setting.

Altered metabolism is a hallmark of cancer. In addition to glucose, glutamine is an important nutrient for cellular growth and proliferation. Noninvasive imaging via PET may help facilitate precision treatment of cancer through patient selection and monitoring of treatment response. l-[5- 11 C]-glutamine ( 11 C-glutamine) is a PET tracer designed to study glutamine uptake and metabolism. The aim of this first-in-human study was to evaluate the radiologic safety and biodistribution of 11 C-glutamine for oncologic PET imaging. Methods: Nine patients with confirmed metastatic colorectal cancer underwent PET/CT imaging. Patients received 337.97 ± 44.08 MBq of 11 C-glutamine. Dynamic PET acquisitions that were centered over the abdomen or thorax were initiated simultaneously with intravenous tracer administration. After the dynamic acquisition, a whole-body PET/CT scan was acquired. Volume-of-interest analyses were performed to obtain estimates of organ-based absorbed doses of radiation. Results: 11 C-glutamine was well tolerated in all patients, with no observed safety concerns. The organs with the highest radiation exposure included the bladder, pancreas, and liver. The estimated effective dose was 4.46E-03 ± 7.67E-04 mSv/MBq. Accumulation of 11 C-glutamine was elevated and visualized in lung, brain, bone, and liver metastases, suggesting utility for cancer imaging. Conclusion: PET using 11 C-glutamine appears safe for human use and allows noninvasive visualization of metastatic colon cancer lesions in multiple organs. Further studies are needed to elucidate its potential for other cancers and for monitoring response to treatment., (© 2022 by the Society of Nuclear Medicine and Molecular Imaging.)

A method for the rapid sequence determination of peptoids [oligo(N-substituted glycines)] and peptide-peptoid hybrids selected from one-bead-one-compound combinatorial libraries has been developed. In this method, beads carrying unique peptoid (or peptide-peptoid) sequences were subjected to multiple cycles of partial Edman degradation (PED) by treatment with a 1:3 (mol/mol) mixture of phenyl isothiocyanate (PITC) and 9-fluorenylmethyl chloroformate (Fmoc-Cl) to generate a series of N-terminal truncation products for each resin-bound peptoid. After PED, the Fmoc group was removed from the N-terminus and any reacted side chains via piperidine treatment. The resulting mixture of the full-length peptoid and its truncation products was analyzed by matrix-assisted laser desorption ionization (MALDI) mass spectrometry, to reveal the sequence of the full-length peptoid. With a slight modification, the method was also effective in the sequence determination of peptide-peptoid hybrids. This rapid, high-throughput, sensitive, and inexpensive sequencing method should greatly expand the utility of combinatorial peptoid libraries in biomedical and materials research.