Preclinical Evaluation of 99mTc-MAG3-5-Fab Targeting TREM2 in Lung Cancer Mouse Models: A Comparison with 99mTc-MAG3-5-F(ab')2.

Triggering receptor expressed on myeloid cells-2 (TREM2), which is expressed on the surface of tumor-associated macrophages (TAMs), has been found to play a major role in the diagnosis and treatment of tumors. TREM2 expression is significantly upregulated in tumor tissues, and therefore, targeting TREM2 for tumor imaging may be of value. Previously, we performed TREM2 targeting imaging by using 68Ga-NOTA-COG1410 or a 124I-labeled monoclonal antibody (mAb) and F(ab')2 in mouse models of colon and gastric tumors. However, some of the shortcomings of these probes (i.e., the high uptake of 68Ga-NOTA-COG1410 in the liver, the difficulty of obtaining iodine-124, and the long half-life of iodine-124) have hindered their clinical use. Herein, we sought to synthesize novel molecular probes targeting TREM2 that are more conducive to clinical translation, eliminating the interference of isotope availability and in vivo probe biodistribution issues. Therefore, we established A549 cell lines with negative human TREM2 (hTREM2) expression (GFP tag; hTREM2- A549) or upregulated hTREM2 expression (GFP tag; hTREM2+ A549) using lentiviral transfection and confirmed these with Western blotting and immunocytochemistry. We then prepared a mouse anti-human TREM2 (5-mAb) by immunizing with the hTREM2 antigen. The antibody fragments 5-F(ab')2 and 5-Fab were prepared from 5-mAb, and 99mTc-MAG3-5-F(ab')2 and 99mTc-MAG3-5-Fab were then synthesized with excellent stability and specificity. 99mTc-MAG3-5-F(ab')2 had a slightly higher in vitro affinity than 99mTc-MAG3-5-Fab (Kd = 3.32 ± 0.05 nmol versus 4.62 ± 0.85 nmol). 99mTc-MAG3-5-F(ab')2 and 99mTc-MAG3-5-Fab both showed excellent specificity: after adding a 100-fold precursor, the two probes binding to the cells were almost blocked. In vivo pharmacokinetics showed that the distribution and elimination half-lives of 99mTc-MAG3-5-Fab (T1/2α = 1.25 ± 0.30 min and T1/2ß = 21.98 ± 2.80 min, respectively) were significantly reduced compared to those of 99mTc-MAG3-5-F(ab')2 (T1/2α = 2.64 ± 0.37 min and T1/2ß = 86.55 ± 26.86 min, respectively). In micro single-photon emission computed tomography/computed tomography (micro-SPECT/CT) imaging, the tumor was clearly displayed at 1 h after 99mTc-MAG3-5-Fab injection, while the blood background was extremely low at 3 h, and the probe was mainly excreted through the kidneys and biliary tract. 99mTc-MAG3-5-F(ab')2 uptake was also detected at the tumor site, although the blood background was consistently high. The biodistribution results were consistent with the micro-SPECT/CT imaging results. 99mTc-MAG3-5-Fab could clearly display hTREM2+ A549 tumors in a short time (1 h) with low uptake in nontumor organs and tissues and thus has clinical application prospects.

Synthesis, Screening, and Evaluation of Theranostic Molecular CPCR4-Based Probe Targeting CXCR4.

Chemokines and chemokine receptors are indispensable to play a key role in the development of malignant tumors. As one of the most widely expressed chemokine receptors, chemokine (C-X-C motif) receptor 4 (CXCR4) has been a popular research focus. In most tumors, CXCR4 expression is significantly upregulated. Moreover, integrated nuclide diagnosis and therapy targeting CXCR4 show great potential. [68Ga]Ga-pentixafor, a radioligand targeting CXCR4, exhibits a strong affinity for CXCR4 both in vivo and in vitro. However, [177Lu]Lu-pentixather, the therapeutic companion of [68Ga]Ga-pentixafor, requires significant refinement to mitigate its pronounced hepatic biodistribution. The objective of this study was to synthesize theranostic molecular tracers with superior CXCR4 targeting functions. The Daudi cell line, which highly expressed CXCR4, and the MM.1S cell line, which weakly expressed CXCR4, were used in this study. Based on the pharmacophore cyclo (-d-Tyr-n-me-d-Orn-l-Arg-L-2-NAL-Gly-) (CPCR4) of pentixafor, six tracers were synthesized: [124I]I-1 ([124I]I-CPCR4), [99mTc]Tc-2 ([99mTc]Tc-HYNIC-CPCR4), [124I]I-3 ([124I]I-pentixafor), [18F]AlF-4 ([18F]AlF-NETA-CPCR4), [99mTc]Tc-5 ([99mTc]Tc-MAG3-CPCR4) and [124I]I-6 ([124I]I-pentixafor-Ga) and their radiochemical purities were all higher than 95%. After positron emission tomography (PET)/single-photon emission computed tomography (SPECT) imaging, the [124I]I-6 group exhibited the best target-nontarget ratio. At the same time, comparing the [68Ga]Ga-pentixafor group with the [124I]I-6 group, we found that the [124I]I-6 group had a better target-nontarget ratio and lower uptake in nontarget organs. Therefore, compound 6 was selected for therapeutic radionuclide (131I) labeling, and the tumor-bearing animal models were treated with [131I]I-6. The volume of the tumor site was significantly reduced in the treatment group compared with the control group, and no significant side effects were found. [124I]I-6 and [131I]I-6 showed excellent affinity for targeting CXCR4, and they showed great potential for the integrated diagnosis and treatment of tumors with high CXCR4 expression.

Evaluation of a Positron Emission Tomography Tracer Targeting Colony-Stimulating Factor 1 Receptor for Detecting Pulmonary Inflammation.

Colony-stimulating factor 1 receptor (CSF1R) is a type III receptor tyrosine kinase that is crucial for immune cell activation, survival, proliferation, and differentiation. Its expression significantly increases in macrophages during inflammation, playing a crucial role in regulating inflammation resolution and termination. Consequently, CSF1R has emerged as a critical target for both therapeutic intervention and imaging of inflammatory diseases. Herein, we have developed a radiotracer, 1-[4-((7-(dimethylamino)quinazolin-4-yl)oxy)phenyl]-3-(4-[18F]fluorophenyl)urea ([18F]17), for in vivo positron emission tomography (PET) imaging of CSF1R. Compound 17 exhibits a comparable inhibitory potency against CSF1R as the well-known CSF1R inhibitor PLX647. The radiosynthesis of [18F]17 was successfully performed by radiofluorination of aryltrimethyltin precursor with a yield of approximately 12% at the end of synthesis, maintaining a purity exceeding 98%. In vivo stability and biodistribution studies demonstrate that [18F]17 remains >90% intact at 30 min postinjection, with no defluorination observed even at 60 min postinjection. The PET/CT imaging study in lipopolysaccharide-induced pulmonary inflammation mice indicates that [18F]17 offers a more sensitive characterization of pulmonary inflammation compared to traditional [18F]FDG. Notably, [18F]17 shows a higher discrepancy in uptake ratio between mice with pulmonary inflammation and the sham group. Furthermore, the variations in [18F]17 uptake ratio observed on day 7 and day 14 correspond to lung density changes observed in CT imaging. Moreover, the expression levels of CSF1R on day 7 and day 14 follow a trend similar to the uptake pattern of [18F]17, indicating its potential for accurately characterizing CSF1R expression levels and effectively monitoring the pulmonary inflammation progression. These results strongly suggest that [18F]17 has promising prospects as a CSF1R PET tracer, providing diagnostic opportunities for pulmonary inflammatory diseases.

Noninvasive evaluation of PD-L1 expression in non-small cell lung cancer by immunoPET imaging using an acylating agent-modified antibody fragment.

PURPOSE: The aim of this study was to explore an effective 124I labeling strategy and improve the signal-to-noise ratio when evaluating the expression of PD-L1 using an 124I-iodinated durvalumab (durva) F(ab')2 fragment. METHODS: The prepared durva F(ab')2 fragments were incubated with N-succinimidyl-3-(4-hydroxyphenyl) propionate (SHPP); after purification, the HPP-durva F(ab')2 was iodinated using Iodo-Gen method. After the radiochemical purity, stability, and specific activities were determined, the binding affinities of probes prepared using different labeling strategies were compared in vitro. The clinical application value of [124I]I-HPP-durva-F(ab')2 was confirmed by PET imaging. To more objectively evaluate the in vivo distribution and clearance of tracers, the pharmacokinetics and biodistribution assays were also performed. RESULTS: After being modified with SHPP, the average conjugation number of SHPP per durva-F(ab')2 identified by LC-MS was about 8.92 ± 2.84. The prepared [124I]I-HPP-durva F(ab')2 was obtained with a satisfactory radiochemical purity of more than 98% and stability of more than 93% when incubated for 72 h. Compared with unmodified [124I]I-durva F(ab')2, the specific activity of [124I]I-HPP-durva-F(ab')2 was improved (52.91 ± 5.55 MBq/mg and 15.91 ± 0.74 MBq/mg), while the affinity did not significantly change. The biodistribution experiments and PET imaging showed that the prepared [124I]I-HPP-durva-F(ab')2 exhibited an accelerated clearance and improved tumor-to-background ratio compared with [124I]I-durva-F(ab')2. The specificity of [124I]I-HPP-durva-F(ab')2 to PD-L1 was well demonstrated both in vitro and in vivo. CONCLUSIONS: A PD-L1 PET imaging probe [124I]I-HPP-durva F(ab')2 was successfully synthesized through the SHPP modification strategy. The prepared probe was able to accurately evaluate the PD-L1 expression level through high-contrast noninvasive imaging.

124I-Labeled Immuno-PET Targeting hTREM2 for the Diagnosis of Gastric Carcinoma.

Low ß-2-[18F]-fluoro-2-deoxy-d-glucose (18F-FDG) uptake in gastric mucinous adenocarcinoma may cause false-negative diagnosis and erroneous staging. Thus, there is an urgent need for developing tumor-specific imaging agents in gastric cancer diagnostics. Triggering receptor expressed on myeloid cells 2 (TREM2) is a transmembrane protein expressed on the surface of tumor-associated macrophages (TAMs) and is considerably overexpressed in tumor tissues. This study aimed to develop new human TREM2 (hTREM2)-targeting imaging agents to diagnose and monitor gastric cancer. We established a cell line, MGC803, with upregulated expression of hTREM2, at the cell surface. We produced a monoclonal antibody (5-mAb) against hTREM2 by immunizing mice with the hTREM2 antigen to obtain the antibody fragment 5-F(ab')2 using an immunoglobulin G-degrading enzyme of Streptococcus pyogenes (IdeS). Another anti-TREM2-mAb (clone 237920) and its fragment anti-TREM2-F(ab')2 were employed for the comparative study in vitro and in vivo. After 124I labeling, we constructed the probes: 124I-5-mAb, 124I-5-F(ab')2, 124I-anti-TREM2-mAb, and 124I-anti-TREM2-F(ab')2. We found that 5-mAb exhibited higher hTREM2 affinity and slower blood clearance than anti-TREM2-mAb, whose corresponding F(ab')2 fragments demonstrated the same trend. The micro-PET/CT revealed that 124I-5-F(ab')2 exhibited advantages of tumor enrichment and fast metabolism. The biodistribution study results were consistent with those of micro-PET/CT. Among the four tracers, 124I-5-F(ab')2 was the most suitable specific radiotracer for targeting hTREM2 and displayed potential utility as a tumor-imaging tracer for diagnosing gastric carcinoma.

Noninvasive Evaluation of EGFR Expression of Digestive Tumors Using 99mTc-MAG3-Cet-F(ab')2-Based SPECT/CT Imaging.

Purpose: This study is aimed at investigating the feasibility of cetuximab (Cet) F(ab')2 fragment- (Cet-F(ab')2-) based single photon emission tomography/computed tomography (SPECT/CT) for assessing the epidermal growth factor receptor (EGFR) expression in digestive tumor mouse models. Methods: Cet-F(ab')2 was synthesized using immunoglobulin G-degrading enzyme of Streptococcus pyogenes (IdeS) protease and purified with protein A beads. The product and its in vitro stability in normal saline and 1% bovine serum albumin were analyzed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The EGFR expression in the human colon tumor cell line HT29 and the human stomach tumor cell line MGC803 were verified using western blotting and immunocytochemistry. Cet-F(ab')2 was conjugated with 5(6)-carboxytetramethylrhodamine succinimidyl ester to demonstrate its binding ability to the MGC803 and HT29 cells. Cet-F(ab')2 was conjugated with NHS-MAG3 for 99mTc radiolabeling. The best imaging time was determined using a biodistribution assay at 1, 4, 16, and 24 h after injection of the 99mTc-MAG3-Cet-F(ab')2 tracer. Furthermore, 99mTc-MAG3-Cet-F(ab')2 SPECT/CT was performed on MGC803 and HT29 tumor-bearing nude mice. Results: HT29 cells had low EGFR expression while MGC803 cell exhibited the high EGFR expression. Cet-F(ab')2 and intact cetuximab showed similar high binding ability to MGC803 cells but not to HT29 cells. Cet-F(ab')2 and 99mTc-MAG3-Cet-F(ab')2 showed excellent in vitro stability. The biodistribution assay showed that the target to nontarget ratio was the highest at 16 h (17.29 ± 5.72, n = 4) after tracer injection. The 99mTc-MAG3-Cet-F(ab')2-based SPECT/CT imaging revealed rapid and sustained tracer uptake in MGC803 tumors rather than in HT29 tumors with high image contrast, which was consistent with the results in vitro. Conclusion: SPECT/CT imaging using 99mTc-MAG3-Cet-F(ab')2 enables the evaluation of the EGFR expression in murine EGFR-positive tumors, indicating the potential utility for noninvasive evaluation of the EGFR expression in tumors.

Synthesis and Evaluation of 68Ga-NOTA-COG1410 Targeting to TREM2 of TAMs as a Specific PET Probe for Digestive Tumor Diagnosis.

Currently, positron emission tomography/computed tomography (PET/CT) is an important method for the discovery and diagnosis of digestive system tumors. However, the shortage of specific imaging tracer limits the effectiveness of PET. Triggering receptor expressed on myeloid cells 2 (TREM2) as an M2-type macrophage biomarker is receiving much attention considering its high abundance and specificity, which could be an ideal target for PET imaging. First, the expression of TREM2 in tumors and corresponding normal tissues was analyzed using a database and was verified by tissue microarrays and murine model slices, and we found that the expression of TREM2 in tumor tissues was significantly higher than that in normal tissues and enteritis tissues. Then, we established a macrophage co-culture system to obtain tumor-associated macrophages (TAMs). Compared with M1-type macrophages and tumor cells, TAMs had a higher expression level of TREM2. The novel radioligand 68Ga-NOTA-COG1410 was successfully synthesized for TREM2 targeting PET imaging. The biodistribution and micro-PET/CT results showed high uptake of 68Ga-NOTA-COG1410 in the tumor but not in areas of inflammation. The data testified that 68Ga-NOTA-COG1410 was a specific radioligand targeting TREM2, which could be used to distinguish tumors from inflammation. Using 68Ga-NOTA-COG1410, the effectiveness of PET on digestive tumors imaging may be enhanced.

P2X7 receptor-specific radioligand 18F-FTTM for atherosclerotic plaque PET imaging.

PURPOSE: P2X7 receptors have been considered as a promising biomarker for vulnerable atherosclerotic plaques, which are highly expressed by that instability-associated factors such as macrophages. Thus, we aim to investigate the feasibility of using specific P2X7-targeted 18F-labeled tracer 18F-FTTM ((2-chloro-3-[18F]fluorophenyl)[1,4,6,7-tetrahydro-1-(2-pyrimidinyl)-5H-1,2,3-triazolo[4,5-c]pyridin-5-yl]methanone) for PET study of vulnerable atherosclerotic plaques identification. METHOD: The radioligand 18F-FTTM was achieved based on the copper-mediated radiofluorination of arylstannane. In vitro and in vivo experiments were performed to verify the biochemical properties. Dynamic 18F-FTTM Micro-PET/CT imaging was performed for 1 h on ApoE-/- mice (10, 20, 30 weeks on high-fat diet) and wild-type C57BL/6 J mice on normal diet. Ex vivo PET imaging was conducted to verify the specificity of the radioligand. Serum inflammatory cytokines, lipids, and lipoproteins profiles were detected by ELISA. The lipid distribution and morphology of plaques were evaluated by Oil Red O, HE, Masson, and immunofluorescence stainings. RESULTS: 18F-FTTM was afforded with decay-corrected radiochemical yields of 5-10%, specific activity of 269-320 MBq/nmol (n = 8, EOS), and radiochemical purity of above 99%. 18F-FTTM showed excellent stability in vitro, rapid blood clearance in mice, good affinity to RAW264.7 cells. We observed an increase in both in vivo and ex vivo imagings as disease progressed, and the imaging signatures correlated with histopathological features. Furthermore, compared with 18F-FDG imaging, the SUVmax values of 18F-FTTM at the aortic arch of ApoE-/- mice of high-fat feeding for 20 and 30 weeks were 43% and 53% higher than those of the control group, respectively. CONCLUSION: We innovatively apply a new type P2X7-targeted PET probe (18F-FTTM) to identify vulnerable atherosclerotic plaques, to detect the inflammatory response of atherosclerosis, and to provide a powerful non-invasive method for the diagnosis of atherosclerotic lesions and new drug screening for accurate treatment.

Targeting Infiltrating Myeloid Cells in Gastric Cancer Using a Pretargeted Imaging Strategy Based on Bio-Orthogonal Diels-Alder Click Chemistry and Comparison with 89Zr-Labeled Anti-CD11b Positron Emission Tomography Imaging.

Gastric cancer (GC) is a common cancer worldwide, with high incidence and mortality rates. Therefore, early and precise diagnosis is critical to improving GC prognosis. Tumor-associated myeloid cells infiltrate the tumor microenvironment (TME) and can produce immunosuppressive effects in the early stage of the tumor. The surface integrin receptor CD11b is widely expressed in the specific subsets of myeloid cells, and it has the characteristics of high abundance, high specificity, and high potential for targeted immunotherapy. In this study, two strategies for labeling anti-CD11b, including 89Zr-DFO-anti-CD11b and pretargeted imaging (68Ga-NOTA-polypeptide-PEG11-Tz/anti-CD11b-TCO), were used to evaluate the value of early diagnosis of GC and confirm the advantages of the pretargeted strategy for the diagnosis of GC. Pretargeted molecular probe 68Ga-NOTA-polypeptide-PEG11-Tz was synthesized. The binding affinity of the Tz-radioligand to CD11b was evaluated in vitro, and its blood pharmacokinetic test was performed in vivo. Moreover, the anti-CD11b antibody was conjugated with a p-isothiocyanatobenzyl-desferrioxamine (SCN-DFO) chelator and radiolabeled with zirconium-89. Biodistribution and positron-emission computed tomography imaging experiments were performed in MGC-803 tumor-bearing model mice to evaluate the value of the early diagnosis of GC. Histological evaluation of MGC-803 tumors was conducted to confirm the infiltration of the GC TME with CD11b+ myeloid cells. 68Ga-NOTA-polypeptide-PEG11-Tz was successfully radiosynthesized, with the radiochemical purity above 95%, as confirmed by reversed-phase high-performance liquid chromatography. The radioligand showed favorable stability in normal saline and phosphate-buffered saline, good affinity to RAW264.7 cells, and rapid blood clearance in mice. The results of biodistribution and imaging experiments using the pretargeted method showed that the tumor/muscle ratios were 5.17 ± 2.98, 5.94 ± 1.46, and 4.46 ± 2.73 at the pretargeting intervals of 24, 48, and 72 h, respectively. The experimental results using the method of the directly labeling antibody (89Zr-DFO-anti-CD11b) showed that, despite radioactive accumulation in the tumor, there was a higher level of radioactive accumulation in normal tissues. The tumor/muscle ratios were 1.09 ± 0.67, 1.66 ± 0.95, 2.94 ± 1.24, 3.64 ± 1.21, and 3.55 ± 1.64 at 1, 24, 48, 72, and 120 h. The current research proved the value of 68Ga-NOTA-polypeptide-PEG11-Tz/anti-CD11b-TCO in the diagnosis of GC using the pretargeted strategy. Compared to 89Zr-DFO-anti-CD11b, the image contrast achieved by the pretargeted strategy was relatively improved, and the background accumulation of the probe was relatively low. These advantages can improve the diagnostic efficiency for GC and provide supporting evidence for radioimmunotherapy targeting CD11b receptors.

124I-Labeled Monoclonal Antibody and Fragment for the Noninvasive Evaluation of Tumor PD-L1 Expression In Vivo.

Lung cancer is a highly heterogeneous cancer and is divided broadly into small and nonsmall cell lung cancer (SCLC or NSCLC). In all NSCLC patients, it is estimated that 50%-60% are programmed cell death ligand 1 (PD-L1) positive, and anti-PD-1/PD-L1 therapies have shown their clinical application prospects in advanced NSCLC. To avoid unnecessary adverse effects and provide anti-PD-1/PD-L1 therapy to the most appropriate patient population, the PD-L1 expression in patients preparing for treatment must be evaluated accurately and in real time. In this study, we noninvasively evaluate the PD-L1 expression in an NSCLC xenograft using 124I-labeled F(ab')2 fragments of durvalumab (Durva) and compared it with the 124I-labeled intact antibody in terms of the biodistribution and dosimetry. The aim is to develop a nuclide labeled molecular probe with better performance for PD-L1 immunoPET imaging. After cleaving using IdeS protease, the F(ab')2 fragments of Durva were labeled with 124I. The radioligand showed a high radiochemical purity (>96%) and outstanding stability. Western blot, quantitative real-time polymerase chain reaction, and flow cytometry were performed on the two selected NSCLC cell lines to measure the in vitro PD-L1 expression. The H460 cells showed a much higher PD-L1 expression than the A549 cells, both at the protein level and the mRNA level. In the following cell binding experiment and binding specificity assay, the labeled radioligand showed good affinity to high PD-L1 expression cells and could be blocked with excess unlabeled intact Durva. The results of the biodistribution and the positron emission tomography (PET) image showed that the peak tumor uptake of 124I-Durva-F(ab')2 was close to 124I-Durva, but much earlier (5.29 ± 0.42% ID/g for 124I-Durva-F(ab')2 at 12 h vs 5.18 ± 0.73% ID/g for 124I-Durva at 48 h). Compared with 124I-Durva, an accelerated blood clearance was observed for 124I-Durva-F(ab')2. The faster blood clearance allowed for a higher tumor-to-background ratio, which was reflected on the image in contrast. The H460 tumors showed excellent contrast as early as 4 h after injection with 124I-Durva-F(ab')2, and for 124I-Durva, the xenograft could not be distinguished clearly until 24 h after injection. Interestingly, 124I-Durva-F(ab')2 showed lower accumulations compared to other metal isotopes labeled PD-L1 antibodies in bone, liver, spleen etc., which will be beneficial for metastasis detection. Another benefit of accelerated blood clearance was a reduction in the radiation dose. According to the results of the OLINDA/EXM, the effective dose for the total body of 124I-Durva was 4.25-times greater than that of 124I-Durva-F(ab')2 (186 µSv/MBq vs 43.8 µSv/MBq). All of these data indicated that 124I-Durva-F(ab')2 is a promising immunoPET tracer for evaluating the in vivo PD-L1 levels in an NSCLC model and is expected to be successful in future clinical application.

Synthesis and biological evaluation of novel PET tracers [18F]AG120 & [18F]AG135 for imaging mutant isocitrate dehydrogenase 1 expression.

Mutations in isocitrate dehydrogenase 1 (IDH1) are commonly found in various human malignancies. Inhibitors of several mutant IDH1 enzymes have entered clinical trials as target therapeutic drugs for the treatment of patients with IDH1 mutations. Herein, we report the synthesis and evaluation of two 18F-labeled tracers, [18F]AG120 and [18F]AG135 for imaging expression of mutated IDH1 in positron emission tomography (PET). [18F]AG120 and [18F]AG135 were synthesized in decay-corrected radiochemical yield of 1 % and 3 %, respectively, high molar activity (52-66 MBq/nmol and 216-339 MBq/nmol, respectively) and high radiochemical purity (>99%). Both tracers showed good in vitro stability, selective uptake into mutated IDH1-expressing cells and good pharmacokinetic profiles with low uptake in most organs/tissues. Furthermore, [18F]AG120 micro-PET/CT imaging displayed significantly greater uptake in IDH1-mutant than in wild-type tumors, Relatively, uptake of [18F]AG135 was observed neither in IDH1-mutant tumor xenografts nor in wild-type tumors. This study suggests that [18F]AG120 is a promising radiotracer for PET imaging of IDH1 mutation, However, further optimization and investigation are necessary for [18F]AG135 due to the limited uptake in mutated IDH1-expressing tumors.

Comparison of post-therapeutic sequential 131I whole-body scans in the detection of metastatic thyroid cancer.

BACKGROUND: The aim was to compare the detect ability of three sequential 131I whole-body scans (tri-WBS) on the second, third, and fourth day after 131I therapy for metastatic thyroid cancer. METHODS: Differentiated thyroid cancer patients who received oral high-dose 131I therapy underwent routinely tri-WBS on the second, third, and fourth day after total or near-total thyroidectomy in Zhongshan Hospital, Fudan University. We enrolled 137 patients with 261 tri-WBSs in this study between January 2015 and November 2017. The inclusion criteria was that at least one metastasis was found in the tri-WBS. We classified radioactive uptake of metastatic lesions by visual assessment into three grades: grade 0 = no uptake, grade 1= suspicious uptake, and grade 2 = definite uptake. The fourth day 131I WBS images were also compared with concurrent pre-therapeutic 99mTc-pertechnetate WBS images when available. We also analyzed the serum Tg levels of probably statistical difference in the patients with only lymph node, lung, bone, and multiple metastases when they underwent the first radioiodine ablation. RESULTS: A total of 722 metastatic accumulations were identified in the final decisions, including 293 lymph node metastases, 261 nodular pulmonary metastases, 49 diffuse bilateral pulmonary metastases, 106 bone metastases, and 13 other metastases. The differences of intensity of uptake in sequential three day images were significant in visualization of lymph node metastasis (χ2=124.432, P<0.001), nodular pulmonary metastasis (χ2=160.334, P<0.001), diffuse bilateral pulmonary metastasis (χ2=41.710, P<0.001), and bone metastasis (χ2=22.118, P<0.001) in our study. Compared to the second day scans, the fourth day scans detected 87 (29.70%) more metastatic lymph nodes, 111 (42.53%) more nodular pulmonary metastases, 26 (53.06%) more diffuse bilateral pulmonary metastases and 17 (16.95%) more bone metastases. The differences of intensity of uptake between 99mTc-pertechnetate WBS and the fourth day 131I WBS were significant in visualization of lymph node metastasis (χ2=172.624, P<0.001), nodular pulmonary metastasis (χ2=111.004, P<0.001), diffuse bilateral pulmonary metastasis (χ2=17.400, P<0.001) and bone metastasis (χ2=46.298, P<0.001). The means of RTg in the patients with only lymph node, lung, bone metastasis, and multiple metastases were 47.20, 76.58, 89.00, and 91.56, respectively. The differences of serum Tg levels in the patients with only lymph node, lung, bone metastasis, and multiple metastases were significant (χ2=35.850, P<0.001). CONCLUSIONS: The detect ability of tri-WBS was significantly different even for consecutive three-day images on the second, third, and fourth day after 131I therapy for metastatic thyroid cancer. There was a linear trend of increasing 131I uptake from the second to fourth day 131I WBS. The pre-therapy 99mTc-pertechnetate WBS demonstrated a poor ability to detect metastatic thyroid cancer compared to 131I WBS. There was an increasing trend of the means of RTg in patients with more extensive metastases.

Synthesis and evaluation of 18F labeled crizotinib derivative [18F]FPC as a novel PET probe for imaging c-MET-positive NSCLC tumor.

c-MET-positive NSCLC is an important subtype accounting for about 5%~22% of lung cancer. NSCLC patients with activating c-MET are intensively sensitive to c-MET selective receptor tyrosine kinase (RTK) inhibitors, so we aimed to develop a specific PET probe targeting to c-MET-positive NSCLC for potential patients screened by PET/CT. Herein, PET tracer 18F-radiolabeled crizotinib derivative ([18F]FPC) was successfully achieved through a simple one-step 18F-labeling method. [18F]FPC PET imaging on c-MET-positive (as well as blocking group) and negative NSCLC models were further evaluated, and results showed that [18F]FPC was effective as a PET imaging probe that targeted c-MET-positive tumor. Therefore, [18F]FPC could be a potential PET imaging probe for NSCLC tumor which was sensitive to c-MET-TKIs. By virtue of this property, it will benefit NSCLC patients for c-MET-TKI treatment.

Correction to: SPECT/CT imaging of apoptosis in aortic aneurysm with radiolabeled duramycin.

The original version of this article unfortunately contains errors in Figure 4. An incorrect Figure 4D is published which is actually a repetition of Figure 2C (i.e., apoptosis rate in control vs. H2O2-treated group). The correct Figure 4D should be the aortic diameter of control vs. experimental groups. Also, the order of part figures (a\b\c\d) in Figure 4E is incorrect. The correct Figure 4 is given below.

SPECT/CT imaging of apoptosis in aortic aneurysm with radiolabeled duramycin.

The objective of this research was to estimate whether a [99mTc]duramycin probe can be used for apoptosis imaging in patients with aortic aneurysm (AA). Vascular smooth muscle cell (SMC) apoptosis has an important influence on AA development. Thus, non-invasive imaging of SMC apoptosis may be able to evaluate AA progress and risk stratification. SMCs were treated with hydrogen peroxide (H2O2; 200 µΜ) or culture medium as a control. Apoptosis was measured using flow cytometry and [99mTc]duramycin to detect the binding efficiency to apoptotic SMCs. C57/BL6 mice were administered angiotensin-II and beta-aminopropionitrile (BAPN) subcutaneously to establish an AA model, or saline for controls. Aortic specimens underwent pathological evaluation and their aortic diameters were measured after 6 weeks. Micro-SPECT/CT scanning of [99mTc]duramycin and 18F-FDG PET detection were performed. SMCs treated with H2O2 showed more apoptosis compared with the control group (67.2 ± 3.8% vs. 16.1 ± 0.6%, P < 0.01). The experimental group showed a high rate of AA formation (70%) compared with no AA formation in the control group. The average aorta diameter was higher and [99mTc]duramycin uptake at the AA site was higher in the experimental group compared with the control group. Compared with the normal aorta in the control group, AA in experiment group had more severe medial degeneration, elastic fiber reduction and fracture, and collagen degeneration. TUNEL staining verified the higher apoptosis rate at the AA site in experiment group compared with the control group (63.9 ± 3.7% in ascending AA, 66.4 ± 4.0% in thoracic AA, vs. 3.5 ± 0.3% in normal aorta, P < 0.01). [99mTc]Duramycin may be an effective probe to evaluate apoptosis in AA.

Fluorine-18 click radiosynthesis and microPET/CT evaluation of a small peptide-a potential PET probe for carbonic anhydrase IX.

Carbonic anhydrase IX (CA IX) is the first carbonic anhydrase found to be associated with cancer that is over-expressed in a variety of human solid tumors. As a surrogate marker for hypoxia, the expression of CA IX is strongly upregulated in hypoxic tumors by hypoxia and hypoxia-inducible factor 1a (HIF-1a). In our pursuit of a CA IX-specific PET probe, we designed and synthesized a peptide-based CA IX imaging probe by the efficient click reaction of 1,3-dipolar cycloaddition of terminal alkynes and organic azides. The probe 18F-CA IX-P1-4-10 was obtained with a radiochemical yield of 35-45% (n = 5) and radiochemical purity of >99% in 70-80 min (HPLC purification time included). 18F-CA IX-P1-4-10 had good stability in phosphate buffered saline (PBS), but about 51% peptide degradation was detected in new-born calf serum (NBCS) after incubation. Preliminary microPET/CT experiments demonstrated a specific uptake of 18F-CA IX-P1-4-10 in HT29 tumor and the uptake of 18F-CA IX-P1-4-10 was blocked by peptide CA IX-P1-4-10-Yne pretreatment. Immunohistochemical staining and western blotting studies confirmed the HT29 tumor was CA IX-positive which further proved tumor accumulation of 18F-CA IX-P1-4-10 was correlated with CA IX expression. The results suggest that 18F-CA IX-P1-4-10 is a promising PET tracer for the specific imaging of CA IX-expressing tumors at the molecular level.

Decreased vesicular acetylcholine transporter related to memory deficits in epilepsy: A [18 F] VAT positron emission tomography brain imaging study.

OBJECTIVE: Vesicular acetylcholine transporter (VAChT) is a rate-limiting factor for synaptic acetylcholine transport. Our study focused on whether [18 F] VAT, a novel positron emission tomography (PET) tracer, could be used in detecting cognitive deficits in epilepsy. METHODS: Morris water maze test was used to evaluate learning and memory deficits in pilocarpine-induced chronic epilepsy rats 12 weeks after status epilepticus. Interictal [18 F] VAT PET was performed 13 weeks after status epilepticus to evaluate the level of VAChT in cholinergic pathways compared with [18 F] fluorodeoxyglucose PET. The association between VAChT levels and memory measures was analyzed. Neuropathological tests were performed. RESULTS: Epileptic rats exhibited significant memory deficits in Morris water maze test. [18 F] VAT uptake decreased in septum, hippocampus, thalamus, and basal forebrain, and correlated to memory function. Of note, the level of VAChT in basal forebrain significantly decreased, yet no glucose hypometabolism was detected. Immunofluorescence and Western blot demonstrated decreased expression of VAChT in hippocampus and basal forebrain in the epilepsy group, but no change of expression of acetyltransferase or activity of acetylcholinesterase was detected. SIGNIFICANCE: [18 F] VAT PET is a promising method to test the level of VAChT as a valuable biomarker for memory deficits in pilocarpine-induced chronic epileptic rats.

An imaging target TGF-ß1 for hepatocellular carcinoma in mice.

It has been reported that the positive detection rate of Fluorine-18-fluorodeoxyglucose (18F-FDG) metabolism in positron emission tomography (PET) imaging, for the diagnosis of hepatocellular carcinoma (HCC) is only about 50%. In particular, 18F-FDG PET imaging is prone to false negative findings in HCC. Transforming growth factor-beta1 (TGF-ß1) shows over expression rates in early HCC liver tissue growth and promotes tumor invasion and metastases. Our aim was to use In this study, we used the feasibility of iodine-125 (125I)-labeled TGF-ß1 antibody as a nuclear medicine imaging target in HCC. MATERIALS AND METHODS: The TGF-ß1 antibody was obtained from Bioss Inc. The Huh-7 cell line (Liver Cancer Institute, Zhongshan Hospital, Fudan University) is a HCC cell line with high metastatic potential. Each mouse was subcutaneously injected with 5×106/0.1mL Huh-7 cells in the right upper flank region for the establishment of a subcutaneous xenograft model. The Iodogen method was used to label TGF-ß1 antibody with 125I. In this experiment, 100µL of 125I- TGF-ß1 antibody solution, which contained approximately 18,5MBq of 125I-liraglutide, was injected into the tail veins of each of three nude mice with Huh-7 HCC. Micro SPET/CT imaging was performed for each mouse using a nano SPET/CT. RESULTS: The average percentage of injected dose per gram of tissue (ID%) was 1,3% and 2,4%. The tumor was strongly positive for TGF-ß1. CONCLUSION: This pilot study provides an experimental basis for further exploration of the feasibility of TGF-ß1 receptor as a target in HCC imaging and in other cancers.

Nineteen cases with synchronous multiple primary cancers studied by 18F-FDG PET/CT.

OBJECTIVE: To evaluate the value of fluorine -18-fuoro-2-deoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in evaluating synchronous multiple primary cancers (SMPC). METHODS: Nineteen patients with pathologically-confirmed SMPC were collected. Clinical and 18F-FDG PET/CT characteristics of these patients were reviewed and analyzed. Maximum standardized uptake value, (SUVmax) of all lesions was measured and difference (Δ)SUVmax between the SUV of two primary tumors in each patient was calculated as: [(the larger SUVmax - the smaller SUVmax)/ the larger SUVmax]×100%. RESULTS: A total of 38 lesions were identified, which were most frequently located in gastrointestinal tract (n=16), followed by lung (n=10), breast (n=4), kidney (n=4), liver (n=2), pancreas (n=1) and thyroid (n=1). Pathologies of these 38 lesions were 18 adenocarcinomas, 8 squamous cell carcinomas, 4 breast invasive ductal carcinomas, 4 renal cell carcinomas, 2 hepatocellular carcinomas, 1 pancreatic ductal adenocarcinoma and 1 papillary thyroid carcinoma. The mean SUVmax of all lesions was 8.5±6.9, most of them being more than 2.5 (n=30). The mean ΔSUVmax was 57.3%±24.6%, indicating different metabolism of the primary cancers in each patient. CONCLUSION: In our center, SMPC most commonly involved the gastrointestinal tract and adenocarcinomas were the most common pathology type. 18F-FDG PET/CT was useful in the diagnosis of SMPC and the ΔSUVmax indicates different pathological origins of the synchronous cancers.

Re-188 Enhances the Inhibitory Effect of Bevacizumab in Non-Small-Cell Lung Cancer.

The malignant behaviors of solid tumors such as growth, infiltration and metastasis are mainly nourished by tumor neovascularization. Thus, anti-angiogenic therapy is key to controlling tumor progression. Bevacizumab, a humanized anti-vascular endothelial growth factor (VEGF) antibody, plus chemotherapy or biological therapy can prolong survival for cancer patients, but treatment-related mortality is a concern. To improve inhibitory effect and decrease side-effects on non-small-cell lung cancer (NSCLC), we used Re-188, which is a ß emitting radionuclide, directly labeled with bevacizumab for radioimmunotherapy in a human A549 tumor model. Cytotoxic assay data showed that, after 188ReO4- or 188Re-bevacizumab at different concentration for 4 and 24 h, a time- and radioactivity does-dependent reduction in cell viability occurred. Also, an apoptosis assay conformed great apoptosis in the 188Re-bevacizumab group compared with controls and other treatment groups. In vivo, tumor volumes in the 188Re-bevacizumab (11.1 MBq/mice) group were not reduced but growth was delayed compared with other groups. Thus, 188Re-bevacizumab enhanced the therapeutic effect of bevacizumab, suggesting a potential therapeutic strategy for NSCLC treatment.