Angiogenesis Imaging Using (68)Ga-RGD PET/CT: Therapeutic Implications

Current and Emerging Radiotracers and Technologies for Detection of Advanced Differentiated Thyroid Cancer: A Narrative Review

Differentiated thyroid cancer (DTC), which includes papillary and follicular thyroid cancers, differs significantly in pathology compared to other thyroid malignancies such as medullary thyroid cancer (MTC), anaplastic thyroid cancer (ATC), and Hurthle cell carcinoma [...].

Comparative Study of [18F]AlF-LNC1007, [18F]FDG, and [18F]AlF-NOTA-FAPI-04 PET/CT in Breast Cancer Diagnosis: A Methodological Exploration and Analytical Insight

Objective: To compare the diagnostic value of [18F]AlF-LNC1007, [18F]FDG, and [18F]AlF-NOTA-FAPI-04 PET/CT in breast cancer. Methods: 33 patients with highly suspected or already diagnosed but untreated breast cancer were enrolled in the study and underwent [18F]AlF-LNC1007 (30 patients), [18F]FDG (22 patients), and [18F]AlF-NOTA-FAPI-04 (8 patients) PET/CT. Quantitative measurements included the SUVmax and tumor-to-background ratio (TBR) for all lesions and background tissues. The Chi-square test was used for intergroup diagnostic efficacy, and the Wilcoxon test was used for intergroup SUVmax or TBR. Diagnostic efficacy for lymph node metastasis was evaluated using receiver operating characteristic (ROC) analysis. Results: Compared to [18F]FDG, [18F]AlF-LNC1007 had a higher positive predictive value (100% vs 91%, P = 0.0004) in lymph node metastases (42 vs 46) and higher sensitivity (100 vs 76%, P = 0.0003) in bone metastases (33 vs 25) but lower sensitivity (93 vs 100%, P = 0.001) in liver metastases. Apart from liver metastases, [18F]AlF-LNC1007 PET/CT had higher SUVmax in primary tumor and other metastases, with no statistical difference in TBR. Compared to [18F]AlF-NOTA-FAPI-04 PET/CT, [18F]AlF-LNC1007 had less false-positive and a higher positive predictive value in bone metastases (99 vs 95%, P = 0.0003) but had lower SUVmax(P < 0.01) in all primary and metastases lesions. The TBR difference between [18F]AlF-LNC1007 and [18F]AlF-NOTA-FAPI-04 was statistically significant only in bone metastases (5.97 vs 5.02, P = 0.001). The comparison of lymph node detection efficacy between [18F]AlF-LNC1007 and [18F]FDG PET/CT showed significant differences in SUVmax cutoff values for diagnosing lymph node metastases (2.62 vs 3.90), sensitivity (95.2% vs 66.67), and specificity (100% vs 85.00) (all P < 0.001). Conclusion: [18F]AlF-LNC1007 demonstrated superior efficacy compared to [18F]FDG and [18F]AlF-NOTA-FAPI-04 and higher uptake than [18F]FDG in primary tumor, lymph node and bone metastases, and higher TBR than [18F]AlF-NOTA-FAPI-04, especially in bone metastases. [18F]AlF-LNC1007 also showed high specificity in differentiating inflammatory and metastatic lymph nodes.

EGFR- and Integrin αVβ3-Targeting Peptides as Potential Radiometal-Labeled Radiopharmaceuticals for Cancer Theranostics

The burgeoning field of cancer theranostics has witnessed advancements through the development of targeted molecular agents, particularly peptides. These agents exploit the overexpression or mutations of specific receptors, such as the Epidermal Growth Factor receptor (EGFR) and αVβ3 integrin, which are pivotal in tumor growth, angiogenesis, and metastasis. Despite the extensive research into and promising outcomes associated with antibody-based therapies, peptides offer a compelling alternative due to their smaller size, ease of modification, and rapid bioavailability, factors which potentially enhance tumor penetration and reduce systemic toxicity. However, the application of peptides in clinical settings has challenges. Their lower binding affinity and rapid clearance from the bloodstream compared to antibodies often limit their therapeutic efficacy and diagnostic accuracy. This overview sets the stage for a comprehensive review of the current research landscape as it relates to EGFR- and integrin αVβ3-targeting peptides. We aim to delve into their synthesis, radiolabeling techniques, and preclinical and clinical evaluations, highlighting their potential and limitations in cancer theranostics. This review not only synthesizes the extant literature to outline the advancements in peptide-based agents targeting EGFR and integrin αVβ3 but also identifies critical gaps that could inform future research directions. By addressing these gaps, we contribute to the broader discourse on enhancing the diagnostic precision and therapeutic outcomes of cancer treatments.

Incidental Detection of 68 Ga-DOTA-RGD-2 Uptake in Uterine Fibroid

ABSTRACT

Uterine fibroids are benign tumors originating from the smooth muscle cells of the myometrium seen in approximately 20%-50% of women of reproductive age. The Arg-Gly-Asp (RGD) binds to αvβ3 integrin expressed on the surface of angiogenic blood vessels or tumor cells. 18 F-FDG PET/CT has been used to evaluate uterine fibroids, with moderate 18 F-FDG uptake. However, angiogenesis imaging in uterine fibroids has not been evaluated. The present case presents a rare finding of RGD uptake in the uterine fibroid on 68 Ga-DOTA-RGD-2 PET/CT in a patient who underwent angiogenesis imaging for left ankle joint pain and swelling.

VPS35 promotes gastric cancer progression through integrin/FAK/SRC signalling-mediated IL-6/STAT3 pathway activation in a YAP-dependent manner

VPS35 is a key subunit of the retromer complex responsible for recognising cytosolic retrieval signals in cargo and is involved in neurodegenerative disease and tumour progression. However, the function and molecular mechanism of VPS35 in gastric cancer (GC) remains largely unknown. Here, we demonstrated that VPS35 was significantly upregulated in GC, which was associated with poor survival. VPS35 promoted GC cell proliferation and metastasis both in vitro and in vivo. Mechanistically, VPS35 activated FAK-SRC kinases through integrin-mediated outside-in signalling, leading to the activation of YAP and subsequent IL-6 expression induction in tumour cells. What's more, combined mass spectrometry analysis of MGC-803 cell and bioinformatic analysis, we found that phosphorylation of VPS35 was enhanced in GC cells, and phosphorylated VPS35 has enhanced interaction with ITGB3. VPS35 interacted with ITGB3 and affected the recycling of ITGB3 in GC cells. Gain- and loss-of-function experiments revealed that VPS35 promoted tumour proliferation and metastasis via the IL-6/STAT3 pathway. Interestingly, we also found that STAT3 directly bound to the VPS35 promoter and increased VPS35 transcription, thereby establishing a positive regulatory feedback loop. In addition, we demonstrated that VPS35 knockdown sensitised GC cells to 5-FU and cisplatin. These findings provide evidence that VPS35 promotes tumour proliferation and metastasis, and highlight the potential of targeting VPS35- and IL-6/STAT3-mediated tumour interactions as promising therapeutic strategies for GC.

Design and preclinical evaluation of a novel apelin-based PET radiotracer targeting APJ receptor for molecular imaging of angiogenesis

APJ has been extensively described in the pathophysiology of angiogenesis and cell proliferation. The prognostic value of APJ overexpression in many diseases is now established. This study aimed to design a PET radiotracer that specifically binds to APJ. Apelin-F13A-NODAGA (AP747) was synthesized and radiolabeled with gallium-68 ([68Ga]Ga-AP747). Radiolabeling purity was excellent (> 95%) and stable up to 2 h. Affinity constant of [67Ga]Ga-AP747 was measured on APJ-overexpressing colon adenocarcinoma cells and was in nanomolar range. Specificity of [68Ga]Ga-AP747 for APJ was evaluated in vitro by autoradiography and in vivo by small animal PET/CT in both colon adenocarcinoma mouse model and Matrigel plug mouse model. Dynamic of [68Ga]Ga-AP747 PET/CT biodistributions was realized on healthy mice and pigs for two hours, and quantification of signal in organs showed a suitable pharmacokinetic profile for PET imaging, largely excreted by urinary route. Matrigel mice and hindlimb ischemic mice were submitted to a 21-day longitudinal follow-up with [68Ga]Ga-AP747 and [68Ga]Ga-RGD2 small animal PET/CT. [68Ga]Ga-AP747 PET signal in Matrigel was significantly more intense than that of [68Ga]Ga-RGD2. Revascularization of the ischemic hind limb was followed by LASER Doppler. In the hindlimb, [68Ga]Ga-AP747 PET signal was more than twice higher than that of [68Ga]Ga-RGD2 on day 7, and significantly superior over the 21-day follow-up. A significant, positive correlation was found between the [68Ga]Ga-AP747 PET signal on day 7 and late hindlimb perfusion on day 21. We developed a new PET radiotracer that specifically binds to APJ, [68Ga]Ga-AP747 that showed more efficient imaging properties than the most clinically advanced tracer of angiogenesis, [68Ga]Ga-RGD2.

Angiogenesis Imaging of Adrenocortical Carcinoma with Ga-68-NODAGA-RGD Positron Emission Tomography: Opening New Horizons in Multimodality Imaging from Theranostic Perspective

A 53-year-old female, with a known case of adrenocortical carcinoma (ACC), underwent F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for initial staging, which revealed FDG avid large left suprarenal mass contiguous with hypermetabolic tumor thrombus in the inferior vena cava (IVC) through the left renal vein. Thereafter, she underwent angiogenesis imaging using Ga-68-NODAGA-RGD PET/CT, which showed similar avid tracer uptake in both primary and IVC thrombus. Demonstration of RGD avidity in ACC in this case opens a new horizon for targeted radionuclide therapy (e.g., Lu-177 RGD) in selected patients, who may have limited therapeutic options.

Cell-Membrane-Coated Nanoparticles for Targeted Drug Delivery to the Brain for the Treatment of Neurological Diseases

Neurological diseases (NDs) are a significant cause of disability and death in the global population. However, effective treatments still need to be improved for most NDs. In recent years, cell-membrane-coated nanoparticles (CMCNPs) as drug-targeting delivery systems have become a research hotspot. Such a membrane-derived, nano drug-delivery system not only contributes to avoiding immune clearance but also endows nanoparticles (NPs) with various cellular and functional mimicries. This review article first provides an overview of the function and mechanism of single/hybrid cell-membrane-derived NPs. Then, we highlight the application and safety of CMCNPs in NDs. Finally, we discuss the challenges and opportunities in the field.

Targeted delivery of fat extract by platelet membrane-cloaked nanocarriers for the treatment of ischemic stroke

BACKGROUND

Our previous studies suggest that human fat extract (FE) contains a variety of angiogenic factors and may provide an alternative treatment option for stroke. However, the therapeutic effect is largely limited due to its short half-life, and inaccurate targeting.

RESULTS

Herein, we leverage the targeting abilities of platelets (PLTs) to the lesion area of stroke and Arg-Gly-Asp (RGD) peptides to the angiogenic blood vessels to develop a biomimetic nanocarrier that capable of delivering FE precisely to treat stroke. The biomimetic nanocarriers are comprised of FE-encapsulated PLGA (poly(lactic-co-glycolic acid)) core enclosed by RGD peptides decorated plasma membrane of PLTs, namely RGD-PLT@PLGA-FE. We found that RGD-PLT@PLGA-FE not only targeted damaged and inflamed blood vessels but also achieved rapid accumulation in the lesion area of ischemic brain. In addition, RGD-PLT@PLGA-FE kept a sustained release behavior of FE at the lesion site, effectively increased its half-life and promoted angiogenesis and neurogenesis with delivering neurotrophic factors including BDNF, GDNF and bFGF to the brain, that ultimately resulted in blood flow increase and neurobehavioral recovery.

CONCLUSIONS

In conclusion, our study provides a new strategy to design a biomimetic system for FE delivery and it is a promising modality for stroke therapy.

Dual Targeting of Integrin αvβ3 and Neuropilin-1 Receptors Improves Micropositron Emission Tomography Imaging of Breast Cancer

The receptors neuropilin-1 (NRP-1) and integrin α_vβ₃ are overexpressed in breast cancer and associated with neovascularization. We synthesized a heterodimeric tracer, ⁶⁸Ga-DOTA-RGD-ATWLPPR, which simultaneously targets integrin α_vβ₃ and NRP-1 in breast cancer. In this study, we evaluated the diagnostic efficacy of ⁶⁸Ga-DOTA-RGD-ATWLPPR during micropositron emission tomography (microPET)/X-ray computed tomography (CT) imaging and gamma counting. We evaluated the receptor-binding characteristics and tumor-targeting efficacy of the tracer in vitro and in vivo. Static microPET/CT imaging and gamma counting studies showed that ⁶⁸Ga-DOTA-RGD-ATWLPPR uptake in MCF-7 tumors is higher than that of monomeric tracers. ⁶⁸Ga-DOTA-RGD-ATWLPPR uptake could be blocked with excess unlabeled RGD or ATWLPPR, demonstrating the sensitivity and specificity of the tracer. We did not observe bone tracer uptake in vivo, but the data indicated that ⁶⁸Ga-DOTA-RGD-ATWLPPR is metabolized in the kidneys and the liver uptake is low. In conclusion, ⁶⁸Ga-DOTA-RGD-ATWLPPR has improved binding affinity, targeting efficiency, and tumor retention time when compared to monomeric tracers, suggesting that it has potential as an imaging probe for breast cancer detection.

Chemotherapy response prediction with diffuser elapser network

In solid tumors, elevated fluid pressure and inadequate blood perfusion resulting from unbalanced angiogenesis are the prominent reasons for the ineffective drug delivery inside tumors. To normalize the heterogeneous and tortuous tumor vessel structure, antiangiogenic treatment is an effective approach. Additionally, the combined therapy of antiangiogenic agents and chemotherapy drugs has shown promising effects on enhanced drug delivery. However, the need to find the appropriate scheduling and dosages of the combination therapy is one of the main problems in anticancer therapy. Our study aims to generate a realistic response to the treatment schedule, making it possible for future works to use these patient-specific responses to decide on the optimal starting time and dosages of cytotoxic drug treatment. Our dataset is based on our previous in-silico model with a framework for the tumor microenvironment, consisting of a tumor layer, vasculature network, interstitial fluid pressure, and drug diffusion maps. In this regard, the chemotherapy response prediction problem is discussed in the study, putting forth a proof of concept for deep learning models to capture the tumor growth and drug response behaviors simultaneously. The proposed model utilizes multiple convolutional neural network submodels to predict future tumor microenvironment maps considering the effects of ongoing treatment. Since the model has the task of predicting future tumor microenvironment maps, we use two image quality evaluation metrics, which are structural similarity and peak signal-to-noise ratio, to evaluate model performance. We track tumor cell density values of ground truth and predicted tumor microenvironments. The model predicts tumor microenvironment maps seven days ahead with the average structural similarity score of 0.973 and the average peak signal ratio of 35.41 in the test set. It also predicts tumor cell density at the end day of 7 with the mean absolute percentage error of [Formula: see text].

It's Time to Shift the Paradigm: Translation and Clinical Application of Non-αvβ3 Integrin Targeting Radiopharmaceuticals

Simple Summary

Cancer cells often present a different set of proteins on their surface than normal cells. This also applies to integrins, a class of 24 cell surface receptors which mainly are responsible for physically anchoring cells in tissues, but also fulfil a plethora of other functions. If a certain integrin is found on tumor cells but not on normal ones, radioactive molecules (named tracers) that specifically bind to this integrin will accumulate in the cancer lesion if injected into the blood stream. The emitted radiation can be detected from outside the body and allows for localization and thus, diagnosis, of cancer. Only one of the 24 integrins, the subtype αvβ3, has hitherto been thoroughly investigated in this context. We herein summarize the most recent, pertinent research on other integrins, and argue that some of these approaches might ultimately improve the clinical management of the most lethal cancers, such as pancreatic carcinoma.

Abstract

For almost the entire period of the last two decades, translational research in the area of integrin-targeting radiopharmaceuticals was strongly focused on the subtype αvβ3, owing to its expression on endothelial cells and its well-established role as a biomarker for, and promoter of, angiogenesis. Despite a large number of translated tracers and clinical studies, a clinical value of αvβ3-integrin imaging could not be defined yet. The focus of research has, thus, been moving slowly but steadily towards other integrin subtypes which are involved in a large variety of tumorigenic pathways. Peptidic and non-peptidic radioligands for the integrins α5β1, αvβ6, αvβ8, α6β1, α6β4, α3β1, α4β1, and αMβ2 were first synthesized and characterized preclinically. Some of these compounds, targeting the subtypes αvβ6, αvβ8, and α6β1/β4, were subsequently translated into humans during the last few years. αvβ6-Integrin has arguably attracted most attention because it is expressed by some of the cancers with the worst prognosis (above all, pancreatic ductal adenocarcinoma), which substantiates a clinical need for the respective theranostic agents. The receptor furthermore represents a biomarker for malignancy and invasiveness of carcinomas, as well as for fibrotic diseases, such as idiopathic pulmonary fibrosis (IPF), and probably even for Sars-CoV-2 (COVID-19) related syndromes. Accordingly, the largest number of recent first-in-human applications has been reported for radiolabeled compounds targeting αvβ6-integrin. The results indicate a substantial clinical value, which might lead to a paradigm change and trigger the replacement of αvβ3 by αvβ6 as the most popular integrin in theranostics.

Integrins regulate stemness in solid tumor: an emerging therapeutic target

Integrins are the adhesion molecules and transmembrane receptors that consist of α and β subunits. After binding to extracellular matrix components, integrins trigger intracellular signaling and regulate a wide spectrum of cellular functions, including cell survival, proliferation, differentiation and migration. Since the pattern of integrins expression is a key determinant of cell behavior in response to microenvironmental cues, deregulation of integrins caused by various mechanisms has been causally linked to cancer development and progression in several solid tumor types. In this review, we discuss the integrin signalosome with a highlight of a few key pro-oncogenic pathways elicited by integrins, and uncover the mutational and transcriptomic landscape of integrin-encoding genes across human cancers. In addition, we focus on the integrin-mediated control of cancer stem cell and tumor stemness in general, such as tumor initiation, epithelial plasticity, organotropic metastasis and drug resistance. With insights into how integrins contribute to the stem-like functions, we now gain better understanding of the integrin signalosome, which will greatly assist novel therapeutic development and more precise clinical decisions.

There is a world beyond αvβ3-integrin: Multimeric ligands for imaging of the integrin subtypes αvβ6, αvβ8, αvβ3, and α5β1 by positron emission tomography

BACKGROUND

In the context of nuclear medicine and theranostics, integrin-related research and development was, for most of the time, focused predominantly on 'RGD peptides' and the subtype αvβ3-integrin. However, there are no less than 24 known integrins, and peptides without the RGD sequence as well as non-peptidic ligands play an equally important role as selective integrin ligands. On the other hand, multimerization is a well-established method to increase the avidity of binding structures, but multimeric radiopharmaceuticals have not made their way into clinics yet. In this review, we describe how these aspects have been interwoven in the framework of the German Research Foundation's multi-group interdisciplinary funding scheme CRC 824, yielding a series of potent PET imaging agents for selective imaging of various integrin subtypes.

RESULTS

The gallium-68 chelator TRAP was utilized to elaborate symmetrical trimers of various peptidic and non-peptidic integrin ligands. Preclinical data suggested a high potential of the resulting Ga-68-tracers for PET-imaging of the integrins α5β1, αvβ8, αvβ6, and αvβ3. For the first three, we provide some additional immunohistochemistry data in human cancers, which suggest several future clinical applications. Finally, application of αvβ3- and αvβ6-integrin tracers in pancreatic carcinoma patients revealed that unlike αvβ3-targeted PET, αvβ6-integrin PET is not characterized by off-target uptake and thus, enables a substantially improved imaging of this type of cancer.

CONCLUSIONS

Novel radiopharmaceuticals targeting a number of different integrins, above all, αvβ6, have proven their clinical potential and will play an increasingly important role in future theranostics.

Liposomal IR-780 as a Highly Stable Nanotheranostic Agent for Improved Photothermal/Photodynamic Therapy of Brain Tumors by Convection-Enhanced Delivery

Simple Summary

To improve the use of hydrophobic photosensitizer IR-780 in photothermal/photodynamic therapy (PTT/PDT), we entrap IR-780 within the lipid bilayer of liposomes (ILs). Compared to free IR-780, ILs showed well-preserved photothermal response by maintaining the photostability of IR-780 from repeated near infrared (NIR) laser exposure both in vitro and in vivo. Combined with fast endocytosis by human glioblastoma cells, ILs demonstrated enhanced cytotoxicity and induced higher cell apoptosis rate toward human glioblastoma cells over free IR-780, due to PTT with overexpression of heat shock protein and PDT with generation of intracellular reactive oxygen species. To overcome the blood–brain barrier, we used convection enhanced delivery (CED) for specific delivery of ILs to brain tumors in intracranial glioma xenograft. Upon three successive NIR laser irradiations, the liposomal IR-780 could significantly improve the anti-cancer efficacy in glioma treatment, leading to diminished intracranial tumor size and prolonged animal survival time.

Abstract

As a hydrophobic photosensitizer, IR-780 suffers from poor water solubility and low photostability under near infrared (NIR) light, which severely limits its use during successive NIR laser-assisted photothermal/photodynamic therapy (PTT/PDT). To solve this problem, we fabricate cationic IR-780-loaded liposomes (ILs) by entrapping IR-780 within the lipid bilayer of liposomes. We demonstrate enhanced photostability of IR-780 in ILs with well-preserved photothermal response after three repeated NIR laser exposures, in contrast to the rapid decomposition of free IR-780. The cationic nature of ILs promotes fast endocytosis of liposomal IR-780 by U87MG human glioblastoma cells within 30 min. For PTT/PDT in vitro, ILs treatment plus NIR laser irradiation leads to overexpression of heat shock protein 70 and generation of intracellular reactive oxygen species by U87MG cells, resulting in enhanced cytotoxicity and higher cell apoptosis rate. Using intracranial glioma xenograft in nude mice and administration of ILs by convection enhanced delivery (CED) to overcome blood-brain barrier, liposomal IR-780 could be specifically delivered to the brain tumor, as demonstrated from fluorescence imaging. By providing a highly stable liposomal IR-780, ILs significantly improved anti-cancer efficacy in glioma treatment, as revealed from various diagnostic imaging tools and histological examination. Overall, CED of ILs plus successive laser-assisted PTT/PDT may be an alternative approach for treating brain tumor, which can retard glioma growth and prolong animal survival times from orthotopic brain tumor models.

Evaluation of Integrin αvβ3 Expression in Murine Xenograft Models: [68Ga]Ga-DOTA-C(RGDfK) PET Study with Immunohistochemical Confirmation

Tumor blood flow (TBF) is related to drug delivery and hypoxia, both of which can impact the efficacy of anti-cancer therapies. Although integrin α_vβ₃ expression is related to tumor angiogenesis, it remains unclear whether the degree of angiogenesis affects TBF. This study aimed to evaluate the expression of integrin α_vβ₃ in mouse tumor models using [⁶⁸Ga]Ga-DOTA-c(RGDfK) peptide positron emission tomography (PET) and immunohistochemical staining. PET studies were conducted using mouse C6 glioma models and MIA PaCa-2 (n = 6 each). The [⁶⁸Ga]Ga-DOTA-c(RGDfK) peptide was injected via the tail vein (2.17 ± 0.28 MBq), and 10 min static PET scans were performed. Immunohistochemical analysis was conducted using an integrin α_Vβ₃ antibody. [⁶⁸Ga]Ga-DOTA-c(RGDfK) peptide PET revealed higher uptake of the radiotracer in C6 gliomas than in MIA PaCa-2 tumors. The mean standardized uptake value was significantly higher in C6 gliomas (0.35 ± 0.058) than in MIA PaCa-2 tumors (0.17 ± 0.045). Histological analysis revealed intense integrin α_Vβ₃ expression in the C6 gliomas, whereas the MIA PaCa-2 tumors had low expression levels. This study showed that the expression of integrin α_vβ₃ can be differentiated by the [⁶⁸Ga]Ga-DOTA-c(RGDfK) peptide, suggesting the potential applicability of this peptide in the evaluation of the relationship between angiogenesis and TBF.

Prospective Comparison of Angiogenesis-Specific 68Ga-RGD2 PET/CT Imaging Parameters and DAS28-ESR in Rheumatoid Arthritis

OBJECTIVE

The aim of this study was to compare the performance of angiogenesis-specific 68Ga-RGD2 PET/CT with Disease Activity Score 28-erythrocyte sedimentation rate (DAS28-ESR) in assessing disease activity and treatment response in rheumatoid arthritis (RA).

METHODS

This was a prospective study comparing the performance of 68Ga-RGD2 PET/CT and DAS28-ESR in 30 RA patients. All of them underwent 68Ga-RGD2 PET/CT scan from head to toe and clinical examination at the baseline. A repeat scan and clinical examination were done in 27 patients after 3 months of treatment with disease-modifying antirheumatic drugs ± steroids. Three PET parameters, that is, PJC (PET-positive joint count), aSUVmax (average SUVmax), and hSUVmax (highest SUVmax), of positive joints were compared with the DAS28-ESR for disease activity assessment and response evaluation.

RESULTS

Among the 3 PET parameters, PJC showed a significant correlation with the DAS28-ESR (0.64, P < 0.01). A significant change was observed with treatment in the DAS28-ESR and PET parameters of 27 patients at follow-up. There was significant correlation between percentage changes in DAS28-ESR and scan parameters such as PJC (0.689, P < 0.001), aSUVmax (0.712, P < 0.001), and hSUVmax (0.555, P = 0.003) values. The absolute change in aSUVmax value could accurately discriminate (area under the curve, 0.98; P = 0.001) European League Against Rheumatism responders from nonresponders.

CONCLUSIONS

68Ga-RGD2 PET/CT is a promising tool for objective assessment of disease activity and treatment response in patients with RA.

Research Progress of Radiolabeled Asn-Gly-Arg (NGR) Peptides for Imaging and Therapy

Asn-Gly-Arg (NGR) motifs have vasculature-homing properties via interactions with the aminopeptidase N (CD13) expressed on tumor neovasculature. Numerous NGR peptides with different molecular scaffolds have been exploited for targeted delivery of different compounds for imaging and therapy. When conjugated with NGR, complexes recognize the CD13 receptor expressed on the tumor vasculature, which improves the specificity to tumor and avoids systematic toxic reactions. Both preclinical and clinical studies performed with these products suggest that NGR-mediated vascular targeting is an effective strategy for delivering bioactive amounts of cytokines to tumor endothelial cells. For molecular imaging, radiolabeled peptides have been the most successful approach and have been translated into clinic. This review describes current data on radiolabeled tumor vasculature-homing NGR peptides for imaging and therapy.

RGD-Binding Integrins Revisited: How Recently Discovered Functions and Novel Synthetic Ligands (Re-)Shape an Ever-Evolving Field

Integrins have been extensively investigated as therapeutic targets over the last decades, which has been inspired by their multiple functions in cancer progression, metastasis, and angiogenesis as well as a continuously expanding number of other diseases, e.g., sepsis, fibrosis, and viral infections, possibly also Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2). Although integrin-targeted (cancer) therapy trials did not meet the high expectations yet, integrins are still valid and promising targets due to their elevated expression and surface accessibility on diseased cells. Thus, for the future successful clinical translation of integrin-targeted compounds, revisited and innovative treatment strategies have to be explored based on accumulated knowledge of integrin biology. For this, refined approaches are demanded aiming at alternative and improved preclinical models, optimized selectivity and pharmacological properties of integrin ligands, as well as more sophisticated treatment protocols considering dose fine-tuning of compounds. Moreover, integrin ligands exert high accuracy in disease monitoring as diagnostic molecular imaging tools, enabling patient selection for individualized integrin-targeted therapy. The present review comprehensively analyzes the state-of-the-art knowledge on the roles of RGD-binding integrin subtypes in cancer and non-cancerous diseases and outlines the latest achievements in the design and development of synthetic ligands and their application in biomedical, translational, and molecular imaging approaches. Indeed, substantial progress has already been made, including advanced ligand designs, numerous elaborated pre-clinical and first-in-human studies, while the discovery of novel applications for integrin ligands remains to be explored.

Angiogenesis-Targeted 68Ga-DOTA-RGD2 PET/CT Imaging: a Potential Theranostic Application in the Case of Chondrosarcoma

Chondrosarcoma is a cartilaginous tumor of mesenchymal origin. The histology and grade of the tumor determine the chances of relapse and survival. These tumors usually respond poorly to chemo-radiotherapy in cases of non-resectable and recurrent disease. ¹⁸F-FDG PET/CT has been used in evaluation of recurrence. However, these tumors show only mild to moderate FDG avidity due to their lower mitotic activity and large acellular matrix. These tumors are known to have a high degree of angiogenesis, especially in those of higher grade. We present a case of a 53-year-old man with grade II chondrosarcoma of the left femur showing only mild avidity on ¹⁸F-FDG PET/CT but showing moderate to intense tracer avidity on ⁶⁸Ga-DOTA-RGD₂ PET/CT. This may enable the use of angiogenesis-targeted positron and beta-emitting radiopharmaceuticals as a potentially new theranostic alternative treatment in cases of refractory metastatic chondrosarcoma.

A dedicated phantom design for positron emission mammography performance evaluation

A standard protocol for performance evaluation of positron emission mammography (PEM) systems has not yet been established. In this work we propose a methodology based on the design of specific phantoms for this imaging modality with component dimensions in accordance with typical breast lesion sizes together with the adaptation of current international protocols designed for clinical and preclinical positron emission tomographs (PET) systems. This methodology was used to evaluate the performance of the Flex Solo II PEM scanner in terms of spatial resolution, uniformity and contrast lesion detectability, recovery coefficients and spill-over ratios. Positron range effects were studied with ¹⁸F and ⁶⁸Ga, which have very different energy spectra. Our results indicate that in-plane spatial resolution of the system is around 3.0 mm and 4.4 mm for ¹⁸F and ⁶⁸Ga, respectively. Lesion detectability tests with sphere diameters between 4 and 10 mm confirmed that the PEM system can resolve all the spheres (hot or cold). Percent contrast values for ¹⁸F lie between 6%-38% and 34%-51% for hot- and cold- spheres, respectively; the corresponding intervals for ⁶⁸Ga are lower, 4%-25% and 32%-44%. Regarding uniformity quantification, the system shows percentage standard deviations within 4.9%-5.7%, while the percent background variability measurements ranged between 6.7% and 10.9% for both radionuclides. Recovery coefficients measured with hot rod diameters between 1.5 and 9 mm, have values between 0.2-1.05 and 0.17-0.69 for ¹⁸F and ⁶⁸Ga, respectively. Spill-over ratios have large values (0.22 in average) for both radionuclides. Our results indicate that the phantoms and the methodology developed in this work can serve as the basis for establishing an image quality protocol for the systematic evaluation of PEM systems, with a potential extension for performance evaluation of dedicated breastPET scanners.

A Comparison of Angiogenesis and Glycolytic Imaging in Patients With Clinical Suspected Locally Advanced Breast Cancer

F-FDG PET/CT imaging is an important diagnostic tool for accurate staging and assessment of response to neoadjuvant chemotherapy (NACT) in patients with locally advanced breast carcinoma (LABC). However, F-FDG being non-specific marker, it also accumulates in inflammatory conditions, leading to false positive results. Angiogenesis, an essential characteristic for tumor development, intrusion and metastasis can be imaged using Ga-labeled RGD tripeptide. We here depict a series of clinically staged LABC patients who underwent both Ga-DOTA-RGD2 and F-FDG PET/CT imaging for staging and illustrate the similarities and significant differences between the two tracers.

[68Ga]RGD Versus [18F]FDG PET Imaging in Monitoring Treatment Response of a Mouse Model of Human Glioblastoma Tumor with Bevacizumab and/or Temozolomide

PURPOSE

The aim of this study was to evaluate positron emission tomography (PET) imaging with [⁶⁸Ga]NODAGA-c(RGDfK) ([⁶⁸Ga]RGD), in comparison with 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG), for early monitoring of the efficacy of an antiangiogenic agent associated or not with chemotherapy, in a mouse model of glioblastoma (GB).

PROCEDURES

Mice bearing U87MG human GB cells line were parted into five groups of five mice each. One group was imaged at baseline before the treatment phase; another group was treated with bevacizumab (BVZ), another group with temozolomide (TMZ), another group with both agents, and the last one was the control group. Tumors growth and biological properties were evaluated by caliper measurements and PET imaging at three time points (baseline, during treatment t1 = 4-6 days and t2 = 10-12 days). At the end of the study, tumors were counted and analyzed by immunohistochemistry (CD31 to evaluate microvessel density).

RESULTS

The tumor volume assessed by caliper measurements was significantly greater at t1 in the control group than in the TMZ + BVZ-treated group or in the BVZ-treated group. At t2, tumor volume of all treated groups was significantly smaller than that of the control group. [¹⁸F]FDG PET failed to reflect this efficacy of treatment. In contrast, at t1, the [⁶⁸Ga]RGD tumor uptake was concordant with tumor growth in controls and in treated groups. At t2, a significant increase in tumor uptake of [⁶⁸Ga]RGD vs. t1 was only observed in the TMZ-treated group, reflecting a lack of angiogenesis inhibition, whereas TMZ + BVZ resulted in a dramatic tumor arrest, reduction in microvessel density and stable tumor [⁶⁸Ga]RGD uptake.

CONCLUSIONS

[⁶⁸Ga]RGD is a useful PET agent for in vivo angiogenesis imaging and can be useful for monitoring antiangiogenic treatment associated or not with chemotherapy.

The beginning of the end for conventional RECIST - novel therapies require novel imaging approaches

Owing to improvements in our understanding of the biological principles of tumour initiation and progression, a wide variety of novel targeted therapies have been developed. Developments in biomedical imaging, however, have not kept pace with these improvements and are still mainly designed to determine lesion size alone, which is reflected in the Response Evaluation Criteria in Solid Tumors (RECIST). Imaging approaches currently used for the evaluation of treatment responses in patients with solid tumours, therefore, often fail to detect successful responses to novel targeted agents and might even falsely suggest disease progression, a scenario known as pseudoprogression. The ability to differentiate between responders and nonresponders early in the course of treatment is essential to allowing the early adjustment of treatment regimens. Various imaging approaches targeting a single dedicated tumour feature, as described in the hallmarks of cancer, have been successful in preclinical investigations, and some have been evaluated in pilot clinical trials. However, these approaches have largely not been implemented in clinical practice. In this Review, we describe current biomedical imaging approaches used to monitor responses to treatment in patients receiving novel targeted therapies, including a summary of the most promising future approaches and how these might improve clinical practice.

Preclinical Evaluation of Radiolabeled Peptides for PET Imaging of Glioblastoma Multiforme

In this study, we have compared four ⁶⁸Ga-labeled peptides (three Arg-Gly-Asp (RGD) peptides and substance-P) with two ¹⁸F-tracers clinically approved for tumor imaging. We have studied in vitro and in vivo characteristics of selected radiolabeled tracers in a glioblastoma multiforme tumor model. The in vitro part of the study was mainly focused on the evaluation of radiotracers stability under various conditions. We have also determined in vivo stability of studied ⁶⁸Ga-radiotracers by analysis of murine urine collected at various time points after injection. The in vivo behavior of tested ⁶⁸Ga-peptides was evaluated through ex vivo biodistribution studies and PET/CT imaging. The obtained data were compared with clinically used ¹⁸F-tracers. ⁶⁸Ga-RGD peptides showed better imaging properties compared to ¹⁸F-tracers, i.e., higher tumor/background ratios and no accumulation in non-target organs except for excretory organs.

18F-Alfatide II PET/CT for Identification of Breast Cancer: A Preliminary Clinical Study

¹⁸F-alfatide II has been proven to have excellent clinical translational potential. In this study, we investigated ¹⁸F-alfatide II for identifying breast cancer and compared the performances between ¹⁸F-alfatide II and ¹⁸F-FDG. Methods: Forty-four female patients with suspected primary breast cancer were recruited. PET/CT images using ¹⁸F-alfatide II and ¹⁸F-FDG were acquired within 7 d. Tracer uptake in breast lesions was evaluated by visual analysis, and semiquantitative analysis with SUV_max and SUV_mean Results: Forty-two breast cancer lesions and 11 benign breast lesions were confirmed by histopathology in 44 patients. Both ¹⁸F-alfatide II and ¹⁸F-FDG had higher uptake in breast cancer lesions than in benign breast lesions (P < 0.05 for ¹⁸F-alfatide II, P < 0.05 for ¹⁸F-FDG). The area under the curve of ¹⁸F-alfatide II was slightly less than that of ¹⁸F-FDG. Both ¹⁸F-alfatide II and ¹⁸F-FDG had high sensitivity (88.1% vs. 90.5%), high positive predictive value (88.1% vs. 88.4%), moderate specificity (54.5% vs. 54.5%), and moderate negative predictive value (54.5% vs. 60.0%) for differentiating breast cancer from benign breast lesions. By combining ¹⁸F-alfatide II and ¹⁸F-FDG, the sensitivity and negative predictive value significantly increased to 97.6% and 85.7%, respectively, with positive predictive value slightly increased to 89.1% and no change to the specificity (54.5%). The uptake of ¹⁸F-alfatide II (SUV_max: 3.77 ± 1.78) was significantly lower than that of ¹⁸F-FDG (SUV_max: 7.37 ± 4.48) in breast cancer lesions (P < 0.05). ¹⁸F-alfatide II uptake in triple-negative subtype was significantly lower than that in luminal A and luminal B subtypes. By contrast, human epidermal growth factor receptor-2 (HER-2)-overexpressing subtype had higher ¹⁸F-FDG uptake than the other 3 subtypes. There were 8 breast cancer lesions with higher ¹⁸F-alfatide II uptake than ¹⁸F-FDG uptake, which all had a common characteristic that HER-2 expression was negative and estrogen receptor expression was strongly positive. Conclusion: ¹⁸F-alfatide II is suitable for clinical use in breast cancer patients. ¹⁸F-alfatide II is of good performance, but not superior to ¹⁸F-FDG in identifying breast cancer. ¹⁸F-alfatide II may have superiority to ¹⁸F-FDG in detecting breast cancer with strongly positive estrogen receptor expression and negative HER-2 expression.

Comparison and evaluation of two RGD peptides labelled with 68Ga or 18F for PET imaging of angiogenesis in animal models of human glioblastoma or lung carcinoma

The aim of this study was to evaluate two RGD radiotracers radiolabelled with fluorine-18 or gallium-68, in detecting angiogenesis in grafted human tumours and monitoring their treatment with the anti-angiogenic agent bevacizumab.

Sixteen mice bearing an U87MG tumour in one flank and a contralateral A549 tumour were treated with intravenous injections of bevacizumab twice a week for 3 weeks. PET images with ¹⁸F-RGD-K5 and ⁶⁸Ga-RGD were acquired before treatment (baseline), after three bevacizumab injections (t1) and after seven bevacizumab injections (t2).

In A549 tumours, the treatment stopped the tumour growth, with a tumour volume measured by calliper remaining between 0.28 and 0.40 cm³. The decrease in tumour uptake of both RGD tracers was non-significant. Therefore it was not possible to predict this efficacy on tumour growth based on RGD PET results, whereas ex vivo measurements showed a significantly lower tumour uptake of both tracers in mice sacrificed at t2 vs. at baseline.

In U87MG tumours, the uptake measured on PET decreased during treatment, reflecting the partial therapeutic effect observed on tumour volume, consisting in a decrease in the slope of tumour growth. Using ¹⁸F-RGD-K5, this decrease in tumour SUVmax became significant at t1, whereas it was also observed with the ⁶⁸Ga-RGD tracer, but only at t2. ¹⁸F-RGD-K5 appeared more efficient than ⁶⁸Ga-RGD in the visualisation and follow-up of U87MG tumours.

The comparison of those results with those of immunohistochemistry at baseline and at t2 favoured the hypothesis that tumour RGD uptake reflects other cancer properties than just its angiogenic capacity.

Oxyresveratrol prevents murine H22 hepatocellular carcinoma growth and lymph node metastasis via inhibiting tumor angiogenesis and lymphangiogenesis

The purpose of this study was to investigate the effects and mechanisms of oxyresveratrol (Oxyres) on hepatocellular carcinoma (HCC) in vitro and in vivo. The MTT and Transwell assays were performed to investigate the effects of Oxyres on cell proliferation and migration of two HCC cell lines, QGY-7701 and SMMC-7721 cells. H22 cells were subcutaneously injected into hind foot pads of 70 male mice to establish a lymph node metastasis model. These mice were randomly divided into seven groups as follows, control group, HCC group, Oxyres 20 mg/kg group, Oxyres 40 mg/kg group, Oxyres 60 mg/kg group, Resveratrol (Res) group, and Adriamycin (ADM) group. Oxyres, Res, and ADM were intraperitoneally injected daily for consecutive 21 days. Tumors and popliteal lymph node were isolated and embedded for histology analysis. Expressions of CD31 and vascular endothelial growth factor receptor-3 (VEGFR3) in tumors were detected by immunohistocehmistry. Expressions of vascular endothelial growth factor C (VEGF-C) were measured by Western blot. Oxyres significantly inhibited the proliferation and migration of QGY-7701 and SMMC-7721 cells. Oxyres significantly inhibited tumor growth (p < 0.001) and metastasis to sentinel lymph nodes (70%) in a dose-dependent manner. Oxyres showed a similar inhibition rate as Res. Oxyres also significantly decreased micro-blood vessel density and micro-lymphatic vessel density in tumors (p < 0.05). Expressions of CD31, VEGFR3, and VEGF-C of tumors were also inhibited by Oxyres (p < 0.05). Oxyres exerts anti-tumor effects against HCC through inhibiting both angiogenesis and lymph node metastasis, which suggests Oxyres be a potential therapeutic agent.

Response Assessment of 68Ga-DOTA-E-[c(RGDfK)]2 PET/CT in Lung Adenocarcinoma Patients Treated with Nintedanib Plus Docetaxel

Nintedanib is an oral angiokinase inhibitor used as second-line treatment for non-small cell lung cancer. New radiotracers, such as ⁶⁸Ga-DOTA-E-[c(RGDfK)]², that target α_vβ₃ integrin might have an impact as a noninvasive method for assessing angiogenesis inhibitors. Methods: From July 2011 through October 2015, 38 patients received second-line nintedanib plus docetaxel. All patients underwent PET/CT with ⁶⁸Ga-DOTA-E-[c(RGDfK)]² radiotracer and blood-sample tests to quantify angiogenesis factors (fibroblast growth factor, vascular endothelial growth factor, and platelet-derived growth factor AB) before and after completing 2 therapy cycles. Results: Of the 38 patients, 31 had available baseline and follow-up PET/CT. Baseline lung tumor volume addressed with ⁶⁸Ga-DOTA-E-[c(RGDfK)]² PET/CT correlated with serum vascular endothelial growth factor levels, whereas baseline lung/liver SUV_max index correlated with platelet-derived growth factor AB. After treatment, the overall response rate and disease control rate were 7.9% and 47.3%, respectively. A greater decrease in lung tumor volume (-37.2% vs. -27.6%) was associated with a better disease control rate in patients (P = 0.005). Median progression-free survival was 3.7 mo. Nonsmokers and patients with a higher baseline lung tumor volume were more likely to have a higher progression-free survival (6.4 vs. 3.74 [P = 0.023] and 6.4 vs. 2.1 [P = 0.003], respectively). Overall survival was not reached. Patients with a greater decrease in lung SUV_max (not reached vs. 7.1 mo; P = 0.016) and a greater decrease in the lung/spleen SUV_max index (not reached vs. 7.1; P = 0.043) were more likely to have a longer overall survival. Conclusion:⁶⁸Ga-DOTA-E-[c(RGDfK)]² PET/CT is a potentially useful tool for assessing responses to angiogenesis inhibitors. Further analysis and novel studies are warranted to identify patients who might benefit from this therapy.

[Prospective: How will renal, prostatic and urothelial tumours be treated in 10 years?]

Forward thinking does not seek to predict the future, to unveil it as if it were already in existence, rather, its aim is to help us to construct it. Although today's epidemiological and therapeutic situations for urogenital tumours can evolve over the next 10 years, diagnostic and therapeutic methods, as well as the treatment and implementation of innovations, are already rapidly changing. Rather than reducing our prospective thinking to the therapeutic treatment of cancer only, we will aim at proposing a global sanitary vision that includes diagnosis, therapies, prevention, routine utilisation of technomedicine, genomics and even nanomedicine. This journey into the near future of tomorrow's cancerology holds the promise of being better adapted to the evolution of the medical thinking process. Imagining the way we will be treating renal, prostatic and urothelial tumours in 10 years' time is as much an introspection into our present day treatment system as a projection into its hoped for future evolution.

68Ga-Chelation and comparative evaluation of N,N'-bis-[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N'-diacetic acid (HBED-CC) conjugated NGR and RGD peptides as tumor targeted molecular imaging probes

Peptides containing RGD and NGR motifs display high affinity towards tumor vasculature molecular markers, integrin α_vβ₃ and CD13 receptors, respectively. In the present study, RGD and NGR peptides were conjugated with the novel acyclic chelator N,N'-bis-[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N'-diacetic acid (HBED-CC) for radiolabeling with ⁶⁸Ga. The radiotracers [⁶⁸Ga-HBED-CC-c(NGR)] and [⁶⁸Ga-HBED-CC-c(RGD)] were quite hydrophilic with respective log P values being -2.8 ± 0.14 and -2.1 ± 0.17. ⁶⁸Ga-HBED-CC-c(RGD) displayed a significantly higher (p < 0.05) uptake in murine melanoma B16F10 tumors as compared to ⁶⁸Ga-HBED-CC-c(NGR) indicating its higher specificity towards integrin α_vβ₃-positive tumors. The two radiotracers showed similar uptake in CD13-positive human fibrosarcoma HT-1080 tumor xenografts (∼1.5 ± 0.2% ID g^-1). The tumor uptake of the two radiotracers was significantly reduced (p < 0.05) in both animal models during blocking studies. The tumor-to-blood ratio was observed to be ∼2-2.5 for the two radiotracers, whereas the tumor-to-muscle ratio was significantly higher (p < 0.005) for ⁶⁸Ga-HBED-CC-c(RGD) in the two animal models. The two radiotracers ⁶⁸Ga-HBED-CC-c(NGR) and ⁶⁸Ga-HBED-CC-c(RGD) exhibited renal excretion with rapid clearance from blood and other non-target organs. Thus, ⁶⁸Ga-chelated HBED-CC conjugated NGR and RGD peptides expressed features conducive towards development as tumor targeted molecular imaging probes. This study further opens avenues for the successful conjugation of different peptides with the acyclic chelator HBED-CC and expansion of ⁶⁸Ga-based radiopharmaceuticals.