Targeting of MMP2 activity in malignant tumors with a 68Ga-labeled gelatinase inhibitor cyclic peptide

Synthesis and Characterization of a Novel PET Tracer for Noninvasive Evaluation of FGL1 Status in Tumors

Fibrinogen-like protein 1 (FGL1) is a potential novel immune checkpoint target for malignant tumor diagnosis and therapy. Accurate detection of FGL1 levels in tumors via noninvasive PET imaging might be beneficial for managing the disease. To achieve this, multiple FGL1-targeting peptides (FGLP) were designed, and a promising candidate, 68Ga-NOTA-FGLP2, was identified through a high-throughput screening approach using microPET imaging of 68Ga-labeled peptides. Subsequent in vitro cell experiments showed that uptake values of 68Ga-NOTA-FGLP2 in FGL1 positive Huh7 tumor cells were significantly higher than those in FGL1 negative U87 MG tumor cells. Further microPET imaging showed that the Huh7 xenografts were clearly visualized with a favorable contrast. ROI analysis showed that the uptake values of the tracer in Huh7 xenografts were 2.63 ± 0.07% ID/g at 30 min p.i.. After treatment with an excess of unlabeled FGLP2, the tumor uptake significantly decreased to 0.54 ± 0.05% ID/g at 30 min p.i.. Moreover, the uptake in U87 MG xenografts was 0.44 ± 0.06% ID/g at the same time point. The tracer was excreted mainly through the renal system. 18F-FDG PET imaging was also performed in mice bearing Huh7 and U87 MG xenografts, respectively. However, there was no significant difference in the uptake between the tumors with different FGL1 expressions. Preclinical data indicated that 68Ga-NOTA-FGLP2 might be a suitable radiotracer for in vivo noninvasive visualization of tumors with abundant expression of FGL1. Further investigation of 68Ga-NOTA-FGLP2 for tumor diagnosis and therapy is undergoing.

Functionally Heterogenous Macrophage Subsets in the Pathogenesis of Giant Cell Arteritis: Novel Targets for Disease Monitoring and Treatment

Giant cell arteritis (GCA) is a granulomatous large-vessel vasculitis that affects adults above 50 years of age. In GCA, circulating monocytes are recruited to the inflamed arteries. With cues from the vascular microenvironment, they differentiate into macrophages and play important roles in the pathogenesis of GCA via pro-inflammatory cytokine production and vascular remodeling. However, a deeper understanding of macrophage heterogeneity in GCA pathogenesis is needed to assist the development of novel diagnostic tools and targeted therapies. Here, we review the current knowledge on macrophage heterogeneity and diverse functions of macrophage subsets in the pathogenesis of GCA. We next discuss the possibility to exploit their heterogeneity as a source of novel biomarkers and as targets for nuclear imaging. Finally, we discuss novel macrophage-targeted therapies and future directions for targeting these cells in GCA.

Molecular Imaging of Angiogenesis in Oncology: Current Preclinical and Clinical Status

Angiogenesis is an active process, regulating new vessel growth, and is crucial for the survival and growth of tumours next to other complex factors in the tumour microenvironment. We present possible molecular imaging approaches for tumour vascularisation and vitality, focusing on radiopharmaceuticals (tracers). Molecular imaging in general has become an integrated part of cancer therapy, by bringing relevant insights on tumour angiogenic status. After a structured PubMed search, the resulting publication list was screened for oncology related publications in animals and humans, disregarding any cardiovascular findings. The tracers identified can be subdivided into direct targeting of angiogenesis (i.e., vascular endothelial growth factor, laminin, and fibronectin) and indirect targeting (i.e., glucose metabolism, hypoxia, and matrix metallo-proteases, PSMA). Presenting pre-clinical and clinical data of most tracers proposed in the literature, the indirect targeting agents are not 1:1 correlated with angiogenesis factors but do have a strong prognostic power in a clinical setting, while direct targeting agents show most potential and specificity for assessing tumour vascularisation and vitality. Within the direct agents, the combination of multiple targeting tracers into one agent (multimers) seems most promising. This review demonstrates the present clinical applicability of indirect agents, but also the need for more extensive research in the field of direct targeting of angiogenesis in oncology. Although there is currently no direct tracer that can be singled out, the RGD tracer family seems to show the highest potential therefore we expect one of them to enter the clinical routine.

Achievement in active agent structures as a power tools in tumor angiogenesis imaging

According to World Health Organization (WHO) cancer is the second most important cause of death globally. Because angiogenesis is considered as an essential process of growth, proliferation and tumor progression, within this review we decided to shade light on recent development of chemical compounds which play a significant role in its imaging and monitoring. Indeed, the review gives insight about the current achievements of active agents structures involved in imaging techniques such as: positron emission computed tomography (PET), magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT), as well as combination PET/MRI and PET/CT. The review aims to provide the journal audience with a comprehensive and in-deep understanding of chemistry policy in tumor angiogenesis imaging.

Peptide-Based Strategies for Targeted Tumor Treatment and Imaging

Cancer is one of the leading causes of death worldwide. The development of cancer-specific diagnostic agents and anticancer toxins would improve patient survival. The current and standard types of medical care for cancer patients, including surgery, radiotherapy, and chemotherapy, are not able to treat all cancers. A new treatment strategy utilizing tumor targeting peptides to selectively deliver drugs or applicable active agents to solid tumors is becoming a promising approach. In this review, we discuss the different tumor-homing peptides discovered through combinatorial library screening, as well as native active peptides. The different structure–function relationship data that have been used to improve the peptide’s activity and conjugation strategies are highlighted.

Current Concepts in Multi-Modality Imaging of Solid Tumor Angiogenesis

Simple Summary

The recent increase in the use of targeted molecular therapy including anti-angiogenetic agents in cancer treatment necessitate the use of robust tools to assess and guide treatment. Angiogenesis, the formation of new disorganized blood vessels, is used by tumor cells to grow and spread using different mechanisms that could be targeted by anti-angiogenetic agents. In this review, we discuss the biological principles of tumor angiogenesis and the imaging modalities that could provide information beyond gross tumor size and morphology to capture the efficacy of anti-angiogenetic therapeutic response.

Abstract

There have been rapid advancements in cancer treatment in recent years, including targeted molecular therapy and the emergence of anti-angiogenic agents, which necessitate the need to quickly and accurately assess treatment response. The ideal tool is robust and non-invasive so that the treatment can be rapidly adjusted or discontinued based on efficacy. Since targeted therapies primarily affect tumor angiogenesis, morphological assessment based on tumor size alone may be insufficient, and other imaging modalities and features may be more helpful in assessing response. This review aims to discuss the biological principles of tumor angiogenesis and the multi-modality imaging evaluation of anti-angiogenic therapeutic responses.

Recent Trends in Cyclic Peptides as Therapeutic Agents and Biochemical Tools

Notable progress has been made in the therapeutic and research applications of cyclic peptides since our previous review. New drugs based on cyclic peptides are entering the market, such as plecanatide, a cyclic peptide approved by the United States Food and Drug Administration in 2017 for the treatment of chronic idiopathic constipation. In this review, we discuss recent developments in stapled peptides, prepared with the use of chemical linkers, and bicyclic/tricyclic peptides with more than two rings. These have widespread applications for clinical and research purposes: imaging, diagnostics, improvement of oral absorption, enzyme inhibition, development of receptor agonist/antagonist, and the modulation of protein-protein interaction or protein-RNA interaction. Many cyclic peptides are expected to emerge as therapeutics and biochemical tools.

Molecular Imaging of Hydrolytic Enzymes Using PET and SPECT

Hydrolytic enzymes are a large class of biological catalysts that play a vital role in a plethora of critical biochemical processes required to maintain human health. However, the expression and/or activity of these important enzymes can change in many different diseases and therefore represent exciting targets for the development of positron emission tomography (PET) and single-photon emission computed tomography (SPECT) radiotracers. This review focuses on recently reported radiolabeled substrates, reversible inhibitors, and irreversible inhibitors investigated as PET and SPECT tracers for imaging hydrolytic enzymes. By learning from the most successful examples of tracer development for hydrolytic enzymes, it appears that an early focus on careful enzyme kinetics and cell-based studies are key factors for identifying potentially useful new molecular imaging agents.

PET Imaging of VCAM-1 Expression and Monitoring Therapy Response in Tumor with a 68Ga-Labeled Single Chain Variable Fragment

Vascular cell adhesion molecule-1 (VCAM-1) is a transmembrane glycoprotein closely related to tumorigenicity as well as tumor metastasis. It is also a well-known candidate for detecting tumors. LY2409881, an IKKβ inhibitor, could induce apoptosis of VCAM-1 positive cells. Our purpose is to prepare a novel tracer to evaluate its feasibility of detecting VCAM-1 expression and monitoring LY2409881 tumor curative effect. The tracer was prepared by conjugating the single chain variable fragment (scFv) of VCAM-1 and NOTA-NHS-ester and then labeled with ⁶⁸Ga. ⁶⁸Ga-NOTA-VCAM-1_scFv was successfully prepared with high radiochemical yield. VCAM-1 overexpression and underexpression melanoma cell lines, B16F10 and A375m, were used in this study. The results of microPET/CT imaging in small animals indicated that the uptake of ⁶⁸Ga-NOTA-VCAM-1_scFv in B16F10 tumor was much higher than that of A375m, which was also confirmed by the biodistribution and autoradiography results. LY2409881 inhibits the growth of B16F10 melanoma in vivo by inducing dose- and time-dependent growth inhibition and apoptosis of the cells. The LY2409881 treated group and DMSO control group were established and imaged by microPET/CT. In the LY2409881 group, uptake of the tracer in tumor was decreased at the first week, and then gradually recovered to the initial level. In DMSO control, the uptake of the tracer remained at the same level during the whole time. The results suggested that LY2409881 inhibits the expression of VCAM-1 and suppresses tumor growth. ⁶⁸Ga-NOTA-VCAM-1_scFv, an easily synthesized probe, has a potential clinical application in the visual monitoring of IKKβ inhibitor intervention on VCAM-1 positive tumors.

Multimodality Imaging in Tumor Angiogenesis: Present Status and Perspectives

Angiogenesis is a complex biological process that plays a central role in progression of tumor growth and metastasis. It led to a search for antiangiogenic molecules, and to design antiangiogenic strategies for cancer treatment. Noninvasive molecular imaging, such as positron emission tomography (PET) and single photon emission computed tomography (SPECT), could be useful for lesion detection, to select patients likely to respond to antiangiogenic therapies, to confirm successful targeting, and dose optimization. Additionally, nuclear imaging techniques could also aid in the development of new angiogenesis-targeted drugs and their validation. Angiogenesis imaging can be categorized as targeted at three major cell types: (I) non-endothelial cell targets, (II) endothelial cell targets, and (III) extracellular matrix proteins and matrix proteases. Even if radiopharmaceuticals studying the metabolism and hypoxia can be also used for the study of angiogenesis, many of the agents used in nuclear imaging for this purpose are yet to be investigated. The purpose of this review is to describe the role of molecular imaging in tumor angiogenesis, highlighting the advances in this field.