Superiority of 18F-FAPI-42 PET/CT in the detection of primary tumor and management of appendiceal neoplasm to 18F-FDG PET/CT and CE-CT.

BACKGROUND: In the present study, we investigated the value of 18F-fibroblast-activation protein inhibitor (FAPI) positron emission tomography/computed tomography (18F-FAPI-42 PET/CT) to preoperative evaluations of appendiceal neoplasms and management for patients. METHODS: This single-center retrospective clinical study, including 16 untreated and 6 treated patients, was performed from January 2022 to May 2023 at Southern Medical University Nanfang Hospital. Histopathologic examination and imaging follow-up served as the reference standard. 18F-FAPI-42 PET/CT was compared to 18F-fluorodeoxyglucose (18F-FDG) PET/CT and contrast-enhanced CT (CE-CT) in terms of maximal standardized uptake value (SUVmax), diagnostic efficacy and impact on treatment decisions. RESULTS: The accurate detection of primary tumors and peritoneal metastases were improved from 28.6% (4/14) and 50% (8/16) for CE-CT, and 43.8% (7/16) and 85.0% (17/20) for 18F-FDG PET/CT, to 87.5% (14/16) and 100% (20/20) for 18F-FAPI-42 PET/CT. Compared to 18F-FDG PET/CT, 18F-FAPI-42 PET/CT detected more regions infiltrated by peritoneal metastases (108 vs. 43), thus produced a higher peritoneal cancer index (PCI) score (median PCI: 12 vs. 5, P < 0.01). 18F-FAPI-42 PET/CT changed the intended treatment plans in 35.7% (5/14) of patients compared to CE-CT and 25% (4/16) of patients compared to 18F-FDG PET/CT but did not improve the management of patients with recurrent tumors. CONCLUSIONS: The present study revealed that 18F-FAPI-42 PET/CT can supplement CE-CT and 18F-FDG PET/CT to provide a more accurate detection of appendiceal neoplasms and improved treatment decision making for patients.

Radiosynthesis, preclinical evaluation and pilot clinical PET imaging study of a 18F-labeled tracer targeting fibroblast activation protein.

Fibroblast activation protein (FAP) is a promising molecular target for imaging in various types of cancers. Several 18F-labeled FAP inhibitor (FAPI) tracers have been evaluated in clinical study. However, these tracers display high physiological uptake in gallbladder and bile duct system. To overcome the limitation, we herein designed a novel radiotracer named 18F-FAPTG. 18F-FAPTG was produced with a non-decay-corrected radiochemical yield of 24.0 ± 6.0% and 22.0 ± 7.0% for manual and automatic synthesis, respectively. 18F-FAPTG exhibited high hydrophilicity and stability in vitro. The studies of cellular uptake, internalization, efflux properties and competitive binding to FAP of 18F-FAPTG indicated that the tracer showed high specificity, rapid internalization and low cellular efflux in FAP-positive cells. Biodistribution studies and microPET in mice bearing FAP-positive xenografts demonstrated extremely low uptake in the majority of other organs and main excretion of 18F-FAPTG through the urinary system. Furthermore, compared to 18F-FAPI-42, 18F-FAPTG showed significantly lower uptake in gallbladder, higher tumor uptake and longer tumor retention. In the pilot clinical study, 18F-FAPTG PET/CT demonstrated favorable tumor-to-background ratios in most organs and clearly displayed the malignant lesions. Our findings indicated that 18F-FAPTG had an advantage over 18F-FAPI-42 in PET imaging for cancers located in gallbladder the bile duct system. Thus, 18F-FAPTG could be an alternative to the currently available FAPI tracers.

A proper protocol for routine 18F-FDG uEXPLORER total-body PET/CT scans.

BACKGROUND: Conventional clinical PET scanners typically have an axial field of view (AFOV) of 15-30 cm, resulting in limited coverage and relatively low photon detection efficiency. Taking advantage of the development of long-axial PET/CT, the uEXPLORER PET/CT scanner with an axial coverage of 194 cm increases the effective count rate by approximately 40 times compared to that of conventional PET scanners. Ordered subset expectation maximization (OSEM) is the most widely used iterative algorithm in PET. The major drawback of OSEM is that the iteration process must be stopped before convergence to avoid image degradation due to excessive noise. A new Bayesian penalized-likelihood iterative PET reconstruction, named HYPER iterative, was developed and is now available on the uEXPLORER total-body PET/CT, which incorporates a noise control component by using a penalty function in each iteration and finds the maximum likelihood solution through repeated iterations. To date, its impact on lesion visibility in patients with a full injected dose or half injected dose is unclear. The goal of this study was to determine a proper protocol for routine 18F-FDG uEXPLORER total-body PET/CT scans. RESULTS: The uEXPLORER total-body PET/CT images reconstructed using both OSEM and HYPER iterative algorithms of 20 tumour patients were retrospectively reviewed. The quality of the 5 min PET image was excellent (score 5) for all of the dose and reconstruction methods. Using the HYPER iterative method, the PET images reached excellent quality at 1 min with full-dose PET and at 2 min with half-dose PET. The PET image reached a similar excellent quality at 2 min with a full dose and at 3 min with a half dose using OSEM. The noise in the OSEM reconstruction was higher than that in the HYPER iterative. Compared to OSEM, the HYPER iterative had a slightly higher SUVmax and TBR of the lesions for large positive lesions (≥ 2 cm) (SUVmax: up to 9.03% higher in full dose and up to 12.52% higher in half dose; TBR: up to 8.69% higher in full dose and up to 23.39% higher in half dose). For small positive lesions (≤ 10 mm), the HYPER iterative had an obviously higher SUVmax and TBR of the lesions (SUVmax: up to 45.21% higher in full dose and up to 74.96% higher in half dose; TBR: up to 44.91% higher in full dose and up to 93.73% higher in half dose). CONCLUSIONS: A 1 min scan with a full dose and a 2 min scan with a half dose are optimal for clinical diagnosis using the HYPER iterative and 2 min and 3 min for OSEM. For quantification of the small lesions, HYPER iterative reconstruction is preferred.

Noninvasive imaging of FAP expression using positron emission tomography: A comparative evaluation of a [18F]-labeled glycopeptide-containing FAPI with [18F]FAPI-42.

PURPOSE: Research on fibroblast activating protein (FAP)-targeting inhibitor (FAPI) has become an important focus for cancer imaging and radiotherapy. Quinoline-based tracers [68 Ga]FAPI-04 and [18F]FAPI-42 have been widely used for positron emission tomography (PET) imaging of most tumors. However, there exist some limitations of these tracers with high uptake in biliary duct system and unstable uptake in pancreas, unsuitable for abdominal tumors PET imaging. Here we developed a [18F]-labeled glycopeptide-containing FAPI tracer (named [18F]FAPT) for PET imaging of FAP in cancers. METHODS: [18F]FAPT was synthesized manually and automatically. The competitive binding to FAP, cellular internalization, and efflux characteristics were examined in vitro using A549-FAP cells. Dynamic MicroPET and biodistribution studies of [18F]FAPT were then conducted in A549-FAP and U87MG xenograft tumor mouse models compared with [18F]FAPI-42. Five healthy volunteers and three patients with cancer underwent [18F]FAPT PET/CT. RESULTS: Preclinical and clinical studies showed specific binding of [18F]FAPT to FAP and favorable pharmacokinetic properties with better hydrophilicity, lower uptake in biliary duct system, higher tumor uptake and longer tumor retention compared with [18F]FAPI-42. The biodistribution of [18F]FAPT in healthy volunteers and patients with cancer displayed low uptake in most normal tissues except for pancreas, thyroid and salivary gland, which could contribute to high tumor-to-background ratios in most cancers. CONCLUSION: [18F]FAPT is better PET tracer than [18F]FAPI-42 for imaging of biliary duct system cancer, potentially providing a tool to examine FAP expression in most cancers with high tumor-to-background ratios.

Pharmacokinetic analysis of 6-O-[18F]FEE for PET imaging of EGFR mutation.

6-O-[18F]Fluoroethylerlotinib (6-O-[18F]FEE), with a suitable half-life for commercial distribution, may be a good replacement for [11C]erlotinib to identify epidermal growth factor receptor (EGFR) positive tumors with activating mutations to tyrosine kinase inhibitors therapy. In this study, we explored the fully automated synthesis of 6-O-[18F]FEE and investigated its pharmacokinetics in tumor-bearing mice. 6-O-[18F]FEE with high specific activity (28-100 GBq/µmol) and radiochemistry purity (over 99 %) was obtained by two-step reaction and Radio-HPLC separation in PET-MF-2 V-IT-1 automated synthesizer. PET imaging of 6-O-[18F]FEE in HCC827, A431, and U87 tumor-bearing mice with different EGFR expression and mutation was performed. Uptake and blocking of PET imaging indicated that the probe specifically targeted exon 19 deleted EGFR (the quantitative analysis of tumor-to-mouse ratio for HCC827, HCC827 blocking, U87, A431 was 2.58 ± 0.24, 1.20 ± 0.15, 1.18 ± 0.19, and 1.05 ± 0.13 respectively). Dynamic imaging was used to study the pharmacokinetics of the probe in tumor-bearing mice. Logan plot graphical analysis demonstrated late linearity and a high fitting correlation coefficient (0.998), supporting reversible kinetics. According to the Akaike Information Criterion (AIC) rule, the 2-compartment reversible model was more consistent with the metabolic properties of 6-O-[18F]FEE. The automated radiosynthesis and pharmacokinetic analysis will promote clinically transformation of 6-O-[18F]FEE.

Optimal clinical protocols for total-body 18F-FDG PET/CT examination under different activity administration plans.

BACKGROUND: Highly sensitive digital total-body PET/CT scanners (uEXPLORER) have great potential for clinical applications and fundamental research. Given their increasing sensitivity, low-dose scanning or snapshot imaging is now possible in clinics. However, a standardized total-body 18F-FDG PET/CT protocol is still lacking. Establishing a standard clinical protocol for total-body 18F-FDG PET/CT examination under different activity administration plans can help provide a theoretical reference for nuclear radiologists. METHODS: The NEMA image quality (IQ) phantom was used to evaluate the biases of various total-body 18F-FDG PET/CT protocols related to the administered activity, scan duration, and iterations. Several objective metrics, including contrast recovery (CR), background variability (BV), and contrast-to-noise ratio (CNR), were measured from different protocols. In line with the European Association of Nuclear Medicine Research Ltd. (EARL) guidelines, optimized protocols were suggested and evaluated for total-body 18F-FDG PET/CT imaging for three different injected activities. RESULTS: Our NEMA IQ phantom evaluation resulted in total-body PET/CT images with excellent contrast and low noise, suggesting great potential for reducing administered activity or shortening the scan duration. Different to the iteration number, prolonging the scan duration was the first choice for achieving higher image quality regardless of the activity administered. In light of image quality, tolerance of oncological patients, and the risk of ionizing radiation damage, the 3-min acquisition and 2-iteration (CNR = 7.54), 10-min acquisition and 3-iteration (CNR = 7.01), and 10-min acquisition and 2-iteration (CNR = 5.49) protocols were recommended for full-dose (3.70 MBq/kg), half-dose (1.95 MBq/kg), and quarter-dose (0.98 MBq/kg) activity injection schemes, respectively. Those protocols were applied in clinical practices, and no significant differences were observed for the SUVmax of large/small lesions or the SUVmean of different healthy organs/tissues. CONCLUSION: These findings support that digital total-body PET/CT scanners can generate PET images with a high CNR and low-noise background, even with a short acquisition time and low administered activity. The proposed protocols for different administered activities were determined to be valid for clinical examination and can maximize the value of this imaging type.

Effects of replication domains on genome-wide UV-induced DNA damage and repair.

Nucleotide excision repair is the primary repair mechanism that removes UV-induced DNA lesions in placentals. Unrepaired UV-induced lesions could result in mutations during DNA replication. Although the mutagenesis of pyrimidine dimers is reasonably well understood, the direct effects of replication fork progression on nucleotide excision repair are yet to be clarified. Here, we applied Damage-seq and XR-seq techniques and generated replication maps in synchronized UV-treated HeLa cells. The results suggest that ongoing replication stimulates local repair in both early and late replication domains. Additionally, it was revealed that lesions on lagging strand templates are repaired slower in late replication domains, which is probably due to the imbalanced sequence context. Asymmetric relative repair is in line with the strand bias of melanoma mutations, suggesting a role of exogenous damage, repair, and replication in mutational strand asymmetry.

Targeting the sheddase activity of ADAM17 by an anti-ADAM17 antibody D1(A12) inhibits head and neck squamous cell carcinoma cell proliferation and motility via blockage of bradykinin induced HERs transactivation.

A disintegrin and metalloproteinase 17 (ADAM17) regulates key cellular processes including proliferation and migration through the shedding of a diverse array of substrates such as epidermal growth factor receptor (EGFR) ligands. ADAM17 is implicated in the pathogenesis of many diseases including rheumatoid arthritis and cancers such as head and neck squamous cell carcinoma (HNSCC). As a central mediator of cellular events, overexpressed EGFR is a validated molecular target in HNSCC. However, EGFR inhibition constantly leads to tumour resistance. One possible mechanism of resistance is the activation of alternative EGFR family receptors and downstream pathways via the release of their ligands. Here, we report that treating human HNSCC cells in vitro with a human anti-ADAM17 inhibitory antibody, D1(A12), suppresses proliferation and motility in the absence or presence of the EGFR tyrosine kinase inhibitor (TKI) gefitinib. Treatment with D1(A12) decreases both the endogenous and the bradykinin (BK)-stimulated shedding of HER ligands, accompanied by a reduction in the phosphorylation of HER receptors and downstream signalling pathways including STAT3, AKT and ERK. Knockdown of ADAM17, but not ADAM10, also suppresses HNSCC cell proliferation and migration. Furthermore, we show that heregulin (HRG) and heparin-binding epidermal growth factor like growth factor (HB-EGF) predominantly participate in proliferation and migration, respectively. Taken together, these results demonstrate that D1(A12)-mediated inhibition of cell proliferation, motility, phosphorylation of HER receptors and downstream signalling is achieved via reduced shedding of ADAM17 ligands. These findings underscore the importance of ADAM17 and suggest that D1(A12) might be an effective targeted agent for treating EGFR TKI-resistant HNSCC.

Development of a 'mouse and human cross-reactive' affinity-matured exosite inhibitory human antibody specific to TACE (ADAM17) for cancer immunotherapy.

We previously showed that a human anti-TACE antibody, D1(A12), is a potent inhibitor of TNF-α converting enzyme (TACE) ectodomain proteolysis and has pharmacokinetic properties suitable for studies of the inhibition of TACE-dependent growth factor shedding in relation to possible therapeutic applications. However, the lack of murine TACE immunoreactivity limits pre-clinical in vivo studies to human xenograft models which are poor analogies to in situ pathology and are not considered clinically predictive. Here, to overcome these limitations, we set out to develop a 'mouse and human cross-reactive' specific anti-TACE antibody. We first re-investigated the originally selected anti-TACE ectodomain phage-display clones, and isolated a lead 'mouse-human cross-reactive' anti-TACE scFv, clone A9. We reformatted scFv-A9 into an IgG2 framework for comprehensive biochemical and cellular characterization and further demonstrated that A9 is an exosite TACE inhibitor. However, surface plasmon resonance analysis and quenched-fluorescent (QF) peptide assay indicated that IgG reformatting of A9 caused low binding affinity and an 80-fold reduction in TACE ectodomain inhibition, severely limiting its efficacy. To address this, we constructed second generation phage-display randomization libraries focused on the complementarity-determining region 3, and carried out affinity selections shuffling between human and mouse TACE ectodomain as antigen in addition to an off-rate selection to increase the chance of affinity improvement. The bespoke 'three-step' selections enabled a 100-fold affinity enhancement of A9 IgG, and also improved its IC50 in a QF peptide assay to 0.2 nM. In human and mouse cancer cell assays, matured A9 IgG showed significant cell-surface TACE inhibition as a monotherapy or combination therapy with chemotherapeutic agent. Collectively, these data suggest that we successfully developed an exosite inhibitor of TACE with sub-nanomolar affinity, which possesses both murine and human immunoreactive properties that can be used for in vivo application in murine pre-clinical cancer models.

[Effect of selenium on the uptake and translocation of manganese, iron, phosphorus and selenium in rice (Oryza sativa L.)].

A pot experiment was conducted to clarify the effect of selenium on the uptake and translocation of manganese (Mn), iron (Fe) , phosphorus (P) and selenium (Se) in rice ( Oryza sativa L.). The results showed that addition of Se led to the significant increase of Se concentration in iron plaque on the root surface, root, shoot, husk and brown rice, and significant decrease of Mn concentration in shoot, husk and brown rice. At the Se concentrations of 0.5 and 1.0 mg.kg-1 in soil, Mn concentrations in rice shoot decreased by 32. 2% and 35.0% respectively, in husk 22.0% and 42.6% , in brown rice 27.5% and 28.5% , compared with the Se-free treatment. There was no significant effect of Se on the P and Fe concentrations in every parts of rice, except for Fe concentrations in husk. The translocation of P and Fe from iron plaque, root, shoot and husk to brown rice was not significantly affected by Se addition, but Mn translocation from iron plaque and root to brown rice was significantly inhibited by Se addition. Addition of 1.0 mg.kg-1. Se resulted in the decrease of translocation factor from iron plaque and root to brown rice by 38.9% and 37.9%, respectively, compared with the control treatment. The distribution ratios of Mn, Fe, P and Se in iron plaque, root, shoot, husk and brown rice were also affected by Se addition. The results indicated that Mn uptake, accumulation and translocation in rice could be decreased by the addition of Se in soil, therefore, Se addition could reduce the Mn harm to human health through food chain.

Calpain 3 is a modulator of the dysferlin protein complex in skeletal muscle.

Muscular dystrophies comprise a genetically heterogeneous group of degenerative muscle disorders characterized by progressive muscle wasting and weakness. Two forms of limb-girdle muscular dystrophy, 2A and 2B, are caused by mutations in calpain 3 (CAPN3) and dysferlin (DYSF), respectively. While CAPN3 may be involved in sarcomere remodeling, DYSF is proposed to play a role in membrane repair. The coexistence of CAPN3 and AHNAK, a protein involved in subsarcolemmal cytoarchitecture and membrane repair, in the dysferlin protein complex and the presence of proteolytic cleavage fragments of AHNAK in skeletal muscle led us to investigate whether AHNAK can act as substrate for CAPN3. We here demonstrate that AHNAK is cleaved by CAPN3 and show that AHNAK is lost in cells expressing active CAPN3. Conversely, AHNAK accumulates when calpain 3 is defective in skeletal muscle of calpainopathy patients. Moreover, we demonstrate that AHNAK fragments cleaved by CAPN3 have lost their affinity for dysferlin. Thus, our findings suggest interconnectivity between both diseases by revealing a novel physiological role for CAPN3 in regulating the dysferlin protein complex.

AHNAK, a novel component of the dysferlin protein complex, redistributes to the cytoplasm with dysferlin during skeletal muscle regeneration.

Mutations in dysferlin cause limb girdle muscular dystrophy 2B, Miyoshi myopathy and distal anterior compartment myopathy. Dysferlin is proposed to play a role in muscle membrane repair. To gain functional insight into the molecular mechanisms of dysferlin, we have searched for dysferlin-interacting proteins in skeletal muscle. By coimmunoprecipitation coupled with mass spectrometry, we demonstrate that AHNAK interacts with dysferlin. We defined the binding sites in dysferlin and AHNAK as the C2A domain in dysferlin and the carboxyterminal domain of AHNAK by glutathione S-transferase (GST)-pull down assays. As expected, the N-terminal domain of myoferlin also interacts with the carboxyterminal domain of AHNAK. In normal skeletal muscle, dysferlin and AHNAK colocalize at the sarcolemmal membrane and T-tubules. In dysferlinopathies, reduction or absence of dysferlin correlates with a secondary muscle-specific loss of AHNAK. Moreover, in regenerating rat muscle, dysferlin and AHNAK showed a marked increase and cytoplasmic localization, consistent with the direct interaction between them. Our data suggest that dysferlin participates in the recruitment and stabilization of AHNAK to the sarcolemma and that AHNAK plays a role in dysferlin membrane repair process. It may also have significant implications for understanding the biology of AHNAK-containing exocytotic vesicles, "enlargosomes," in plasma membrane remodeling and repair.