Molecular Imaging and Biology最新文献

Purpose: Sentinel lymph node (SLN) mapping is a critical procedure in the staging and treatment of cancers, such as breast cancer and melanoma. Current radiocolloids used in SLN localization, like [^99mTc]Tc-Sulfur Colloid, face limitations in imaging resolution and specificity. This study aims to evaluate the biodistribution of [⁶⁸Ga]Ga-DOTA-nanoHSA, a novel nanoparticle-based radiotracer, for SLN mapping using PET/CT imaging in both healthy and tumor-bearing murine models and compare results with [^99mTc]Tc-Sulfur Colloid as the current gold standard for lymph node staging in breast cancer. Additionally, the maximum tolerated dose and potential systemic toxicity of the carrier were assessed in humanized mice.

Methods: Nanoalbumin radiotracers were prepared by thermal denaturation of human serum albumin (HSA), followed by conjugation with 2,2',2″,2″'-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid (DOTA) and labeling with gallium-68. The stability of [⁶⁸Ga]Ga-DOTA-nanoHSA was evaluated in the tracer formulations and in mouse serum. The novel radiotracers were administered subcutaneously and intratumorally in healthy and tumor-bearing mice, respectively, to evaluate SLN uptake via PET/CT imaging. Biodistribution was assessed in major organs, and the tracers' ability to accurately localize SLNs was compared to an existing standard. Toxicity was evaluated in humanized mice, where body weight, clinical scoring, and blood chemistry were monitored over a 14-days period. Mice received escalating doses of DOTA-nanoHSA to determine the maximum tolerated dose.

Results: [⁶⁸Ga]Ga-DOTA-nanoHSA tracers (30 nm and 70 nm) were reliably produced with high radiochemical purity (RCP > 90%). The stability of [⁶⁸Ga]Ga-DOTA-nanoHSA (30 nm) in the final formulations at pH 3.5 and 7.0 and in mouse serum was confirmed up to 4-6 h. [⁶⁸Ga]Ga-DOTA-nanoHSA (30 nm) demonstrated effective SLN localization in both healthy and tumor-bearing mice, with high uptake in SLNs and minimal off-target accumulation in non-lymphatic organs. DOTA-nanoHSA was well-tolerated in humanized mice, with no significant changes in body weight, clinical scores, or blood chemistry parameters, even at higher doses. No dose-dependent toxicity was observed.

Conclusion: [⁶⁸Ga]Ga-DOTA-nanoHSA (30 nm) demonstrated significant potential as a novel imaging agent for SLN mapping. Its favorable toxicity profile, combined with its effectiveness in SLN localization, suggests it could be a valuable alternative for SLN biopsy in clinical practice. Further studies are warranted to confirm these findings in human trials.

Background: Fluorescence-guided molecular imaging may improve colorectal cancer (CRC) patient outcomes by enabling early detection and better surgical treatment, relying on developing targeted fluorescent tracers to highlight tumours. This study investigates visualising primary colon tumours by topically applying EMI-137, a targeted fluorescent tracer designed to bind to c-Met receptor. We introduce a novel viscous formulation to enhance the tracer's performance, aiming for a clear, robust fluorescent signal by improving contact with mucosal surface of ex vivo colon specimens.

Methods: We evaluated fluorescence properties of EMI-137 in phosphate-buffered saline (PBS) and in methylcellulose (m-cellulose) and determined emission spectrum of the tracer in both formulations. Flow cytometry was used to determine EMI-137's specificity for c-Met receptor and its optimal concentration. Live-cell imaging visually confirmed EMI-137's fluorescence signal for the c-Met receptor, highlighting its distinctive characteristics across various solvents. In a prospective cohort study, freshly excised colon cancer specimens were incubated with EMI-137 in PBS or m-cellulose. Specimens underwent a meticulous washing process. Near-infrared fluorescence imaging was performed and compared with histopathological analysis to validate detection accuracy.

Results: Fluorospectrometry showed that m-cellulose enhanced EMI-137's fluorescence intensity compared to PBS. Flow cytometry showed dose-dependent binding of EMI-137 in HT-29 cells, with an optimum at 500 nM. Microscopy confirmed targeting of c-Met receptors. Topical EMI-137 dissolved in m-cellulose visualised colon tumours effectively, resulting in a high tumour-to-background ratio. Histopathological analysis confirmed c-Met expression in these colon tumours.

Conclusion: EMI-137 in a novel viscous vehicle effectively imaged c-Met expressing colon tumors, potentially facilitating fluorescent-guided tumor imaging.

Purpose: Sarcomas, malignancies of mesenchymal origin, present significant diagnostic and therapeutic challenges due to their heterogeneity and low incidence. This review aims to examine the evolving role of fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in the management of soft tissue and musculoskeletal sarcomas. Specifically, it seeks to evaluate 18F-FDG PET/CT's utility in detecting metastatic lesions, differentiating benign from malignant tumors, and assessing treatment responses.

Procedures: A comprehensive review of the literature was conducted to analyze advancements in PET imaging for sarcomas. Emphasis was placed on 18F-FDG PET/CT's role in complementing conventional imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI). Key aspects of PET imaging in musculoskeletal and cardiac tumors were examined, including its sensitivity and specificity in identifying metastases and its metabolic characterization of various tumor types.

Results: 18F-FDG PET/CT has demonstrated high sensitivity and specificity in detecting metastatic sarcoma lesions and grading musculoskeletal tumors, such as osteosarcoma, chondrosarcoma, and Ewing sarcoma. Its ability to provide metabolic insights has enhanced differentiation between benign and malignant tumors, including myxomas, lipomas, angiosarcomas, and leiomyosarcomas. Furthermore, in primary and secondary cardiac tumors, 18F-FDG PET/CT has proven valuable for treatment planning by offering detailed metabolic characterization.

Conclusions: 18F-FDG PET/CT serves as a critical imaging modality in the diagnosis, staging, and treatment monitoring of sarcomas. By complementing conventional imaging techniques, it enhances the accuracy of tumor characterization and facilitates improved clinical decision-making. Its application in both musculoskeletal and cardiac sarcomas underscores its growing significance in oncologic imaging, making it a valuable tool in optimizing patient outcomes.

To investigate magnetic relaxation properties of the tailored contrast using paramagnetic gadolinium (Gd) chelates and superparamagnetic iron oxide particles (SPIOs) for cellular magnetic resonance imaging. The study included three different exposed environments with two different characteristic contrast agents which used gadodiamide (Omniscan; Gd-DTPA-BMA) and ferumoxide (Feridex; SPIO) in C6 brain cancer cells. Based on the minimal mutual interaction between these two agents in vitro, we examined the possibility of using mixture of cells that are separately labeled with two contrast agents or using concurrently labeled cells with different concentrations of the two contrast agents. In order to characterize the MR relaxation properties, aqueous solutions containing various concentrations of the two contrast agents were prepared as well as Ficoll solution suspensions containing labeled cells by different labeling schemes and subsequently investigated R₁ and R₂ relaxation rates. The tailored contrast can be created by concurrent labeling of the two contrast agents as well as combining separately labeled cells with the two contrast agents. The proposed method would be applied to generate tailored contrast for efficient detection of magnetically-labeled cells in molecular imaging and cell-based therapy.

Purpose: This study aimed to elucidate the molecular and genetic factors contributing to negative ⁶⁸Ga-DOTATATE PET imaging in neuroendocrine tumors (NETs). By integrating whole exome sequencing (WES) and single-cell RNA sequencing (scRNA-seq), we sought to unravel the interplay between negative results of ⁶⁸Ga-DOTATATE PET and genetic mutations in NETs.

Methods: A total of 18 patients with lung, ileal, or pancreatic NETs who underwent ⁶⁸Ga-DOTATATE and ¹⁸F-FDG PET/CT scans as part of their initial diagnostic workup were retrospectively reviewed. WES analysis was conducted to investigate the genetic profile of circulating tumor cells of patients with negative ⁶⁸Ga-DOTATATE scans. Leveraging scRNA-seq and single-cell somatic variant calling analysis, we compared the mutation burden and genetic hallmarks of NET cells with high /positive SSTR2 expression to those with negative/low SSTR2 expression.

Results: Our analysis identified an association between negative ⁶⁸Ga-DOTATATE scans and reduced survival rates, regardless of tumor grade. WES highlighted a predominance of missense mutations, including CREBBP mutation, particularly in patients with negative PET results (incidence of %67 vs. %0). We observed a deleterious mutation in the SSTR2, likely accounting for the observed negative PET scans (incidence of %33). Single-cell single nucleotide variant (SNV) analysis showed that the total unique mutation burden in cells with negative/low SSTR2 expression was significantly higher compared to cells with positive/high expression; and notably, the CREBBP mutation was observed in more than 50% of patients and approximately 35% of NET cells. These results indicate that the frequency of CREBBP mutations is nearly as high as other well-known NET mutations such as MEN1, PTEN, and RB1. Additionally, CREBBP mutations are significantly more frequent in tumors with negative/low SSTR2 expression.

Conclusion: This study suggests that CREBBP mutations in NETs may potentially alter SSTR2 expression, indicating that patients with the mutated CREBBP genotype may not be suitable candidates for SSTR2-targeted PET imaging and radionuclide therapy.

Fibrotic diseases are characterized by excessive accumulation of extracellular matrix (ECM) components following tissue injury, ultimately leading to organ dysfunction and failure. The progression of fibrosis is governed by complex molecular signaling pathways, including TGF-β, PDGF, FGF, CTGF, VEGF, and many others, which regulate myofibroblast activation, ECM production, and tissue remodeling. Traditional diagnostic modalities such as magnetic resonance imaging (MRI), computed tomography (CT), and biopsy are limited in their ability to distinguish active fibrogenesis from established fibrosis or detect early molecular changes. Recent advances in molecular imaging such as the development of targeted radiotracers and MRI contrast agents-have enabled more precise detection and characterization of fibrotic processes at both preclinical and clinical levels. The integration of molecular imaging with targeted probes holds promise for improving early diagnosis, guiding therapeutic strategies, and advancing clinical management of fibrosis. This review presents a comprehensive overview of the molecular mechanisms underlying fibrogenesis, highlights key signaling pathways and biomarkers, and discusses current and emerging molecular imaging agents for fibrotic diseases diagnosis and monitoring.

Purpose: While PSMA-targeted radioligand therapy (RLT) has shown remarkable efficacy for treating end-stage prostate cancer, the α-emitting RLT often results in severe salivary gland toxicity, limiting its use. Various strategies to mitigate this side effect have been attempted with limited success. Accordingly, this study introduced a new PSMA-targeting ligand with more favorable binding characteristics than the existing ligands.

Procedures: The binding affinity of PSMA-1-DOTA to PSMA was compared with that of PSMA-11 and PSMA I&T. Comparison of uptake in the salivary glands, kidneys and PC3pip tumor cells in the xenograft mouse models between [⁶⁸ Ga]Ga-PSMA-1-DOTA, [⁶⁸ Ga]Ga-PSMA-11 and [⁶⁸ Ga]Ga-PSMA I&T was conducted with microPET/CT within the same week. The same mouse models were treated with [¹⁷⁷Lu]Lu-PSMA-1-DOTA or [¹⁷⁷Lu]Lu-PSMA-617. A compassionate use PET imaging study on a patient with metastatic castration-resistant prostate cancer was performed using [⁶⁸ Ga]Ga-PSMA-1-DOTA.

Results: The binding affinity of PSMA-1-DOTA to PSMA was found to be approximately four times greater than other PSMA-targeted ligands. Imaging with microPET/CT revealed significantly lower kidney, uptake and little salivary and lacrimal gland uptake with [⁶⁸ Ga]Ga-PSMA-1-DOTA compared to other PSMA-radioligands. Preclinical efficacy studies demonstrated that [¹⁷⁷Lu]Lu-PSMA-1-DOTA inhibited tumor growth comparable to that with [¹⁷⁷Lu]Lu-PSMA-617, suggesting its potential to enhance the therapeutic window of targeted RLT by avoiding damage to the salivary glands. The compassionate use PET imaging confirmed the reduced salivary gland uptake of [⁶⁸ Ga]Ga-PSMA-1-DOTA in the patient, indicating its potential utility as a targeting agent for RLT with α- or β-emitting radionuclides in patients with PSMA-positive prostate cancer.

Conclusion: PSMA-1-DOTA shows reduced uptake in salivary glands while effectively targeting PSMA-expressing tumors, thus potentially avoiding the side effects of xerostomia, and possibly moving PSMA-targeted RLT to a more frontline therapy for prostate cancer rather than the current use as a last resort.

Purpose: Since prostate-specific membrane antigen (PSMA) is widely expressed in nearly all stages of prostate cancer (PCa), PSMA tracers can be considered a viable diagnostic tool for PCa. Compared to ⁶⁸Ga-labeled PSMA agents, ¹⁸F-labeled analogues have various advantages, including the ability to achieve large scale production; easy to commercialize due to its longer half-life; and the ability to image late time points. Because [¹⁸F]vinyl sulfone (VS) is a good intermediate for labeling thiol groups in mild conditions with high labeling yield, we explored the use of various VS groups for PSMA modifications in this study.

Procedures: We developed six ¹⁸F-labeled radiotracers targeting PSMA from radioactive intermediates to explore targeting ability and distribution in vivo in LNCaP and 22RV1 tumor-bearing mice. Different labeling methods were compared on their ability to lead to PSMA agents with high contrast and uptake.

Results: In vitro stability assay showed that the tracer [¹⁸F]4a had high stability, with more than 95% of the radiochemical purities remaining as intact forms after 0.5, 1, and 2 h incubation, respectively. In vitro binding assays showed that [¹⁸F]4a has a low-micromole binding affinity of 9.45 µM. Cell uptake and internalization assays found that [¹⁸F]4a exhibited the highest cell uptake and internalization in 22RV1 cells (1.25 ± 0.06, 1.32 ± 0.11, 1.73 ± 0.08, and 2.03 ± 0.14%ID/10⁶ cells after 10 min, 30 min, 1 h, and 2 h incubation, respectively for cell uptake assay; 0.52 ± 0.02, 0.70 ± 0.11, 0.78 ± 0.04, and 0.98 ± 0.15%ID/10⁶ cells after 10 min, 30 min, 1 h, and 2 h incubation, respectively for cell internalization assay.) Analysis of the PET images showed that the tracer [¹⁸F]4a had the highest tumor uptake (3.38 ± 0.35%ID/g at 2 h p. i. in 22RV1 tumor-bearing mice; 30.16 ± 13.00%ID/g at 2 h p. i. in LNCaP tumor-bearing mice.) Of note, the tracer [¹⁸F]4a showed an approximately threefold increase in tumor uptake compared to [⁶⁸Ga]PSMA-11 in LNCaP tumor-bearing mice at 2 h p. i. The biodistribution experiment verified the accuracy of the in vivo distribution of [¹⁸F]4a in LNCaP and 22RV1 tumor-bearing mice by PET/CT imaging.

Conclusions: PSMA-targeted radiotracer [¹⁸F]4a is a promising PET agent for prostate cancer diagnosis.

Purpose: Prostate-specific membrane antigen-targeted radioligand therapy (PSMA-RLT) is a promising approach to treating metastatic castration-resistant prostate cancer (mCRPC). With the emergence of oxalyldiaminopropionic acid urea (ODAP-Urea) based radioligands targeting PSMA, novel paradigms focused on PSMA-RLT are garnering attention. This study aims to assess potentially novel ODAP-Urea-based radioligands prepared for PSMA-RLT.

Methods: Albumin binding moieties (ABMs) were selected for optimization. Candidates were evaluated in vitro and subsequently investigated through biodistribution and imaging studies in 22Rv1 tumor-bearing mice.

Results: We synthesized five novel ODAP-Urea-based derivatives (CXY-18, CXY-19, CXY-20, CXY-21, CXY-23) with specific ABM. All compounds demonstrated high affinities for PSMA (K_i values ranging from 0.21 nM to 3.6 nM) and strong human albumin protein binding abilities (83.4 ± 1.6% to 94.6 ± 0.4%). [⁶⁸Ga]Ga-CXY-18 (CXY-18) PET/CT exhibited the highest tumor uptake and blood retention properties. Moreover, the internalization of [⁶⁸Ga]Ga-CXY-18 in the 22Rv1 cell line (23.81 ± 1.67%) exceeded that of [⁶⁸Ga]Ga-PSMA-617 (9.99 ± 0.98%). Biodistribution studies confirmed prolonged blood retention and enhanced tumor uptake with [¹⁷⁷Lu]Lu-CXY-18, peaking at 48 h post-injection (4 h: 27.22 ± 3.61%ID/g; 24 h: 30.61 ± 4.96%ID/g; 48 h: 33.92 ± 2.98%ID/g; 96 h: 30.97 ± 1.87%ID/g; 192 h: 9.03 ± 3.49%ID/g).

Conclusion: Our study indicates that CXY-18 possesses high PSMA specificity and tumor uptake, underscoring its promising potential for PSMA-RLT using 4-IBA.

Purpose: To assess alterations in H3R availability with age and body mass index (BMI) in healthy humans using in vivo [¹¹C]GSK189254 positron emission tomography (PET) imaging.

Procedure: Twenty-four healthy individuals (2 females, 22 males; age range 20-47 years) were scanned with [¹¹C]GSK189254 with High-Resolution Research Tomograph (HRRT) or HR plus scanner. Regional V_T (volume of distribution) values were computed using the two-tissue compartment model. The correlation between V_T and age, BMI were examined, adjusting for relevant potential confounding effects of age or gender and injected mass.

Results: H3R availability (V_T) was correlated with age but not BMI. V_T displayed a negative correlation with age in the anterior cingulate cortex (r = -0.61, p = 0.004), frontal cortex (r = -0.50, p = 0.020), olfactory cortex (r = -0.50, p = 0.022), parietal cortex (r = -0.58, p = 0.006), cerebellum cortex (r = -0.53, p = 0.013), insula (r = -0.48, p = 0.027), putamen (r = -0.46, p = 0.034), thalamus (r = -0.45, p = 0.038), and hippocampus (r = 0.45, p = 0.039).

Conclusion: This in vivo H3R study found a significant age-related decline in most cortical and subcortical regions.