CXCR4-directed theranostics in oncology and inflammation

Ga-68 Pentixafor PET/CT in multiple myeloma and its correlation with clinical parameters: institutional pilot study

OBJECTIVE

This study evaluates the role of Ga-68 Pentixafor PET/CT in staging and follow-up of multiple myeloma (MM) and its correlation with clinical parameters.

METHODS

Thirteen participants (9 males, 4 females; median age: 65 years) with MM were recruited in this prospective observational study. Six participants were included for staging evaluation, seven were included for follow-up evaluation, and underwent Ga-68 Pentixafor PET/CT. Focal PET-positive bone marrow lesions or diffuse bone marrow uptake (uptake more than liver) was considered a positive scan. The quantitative variables like SUVmax, SUVmean, total bone marrow volume and uptake (TBMV & TBMU) and tumor to background ratio (TBRmax) were obtained. Durie Salmon Plus Staging (DSPS) was used for MM staging by PET/CT and was compared with the International Staging System (ISS). Statistical comparison was performed between PET/CT quantitative variables and laboratory parameters.

RESULTS

Twelve participants (12/13) had positive Ga-68 Pentixafor PET/CT, among which one was diagnosed to have anemia of chronic disease. One participant (1/13) who was clinically negative on follow-up had negative Ga-68 Pentixafor PET/CT. The sensitivity, specificity, PPV and NPV of Ga-68 Pentixafor PET/CT in MM (95% CI) were observed to be 100%, 50%, 91.6% and 100%, respectively. The correlation between DSPS and ISS in the patients who came for staging scans was found to be statistically significant (p-value 0.02). In quantitative analysis, either of the quantitative variables in Ga-68 Pentixafor PET/CT was positively correlated with clinical parameters related to tumor burden like CRAB score, serum protein electrophoresis M-protein, beta 2 microglobulin, LDH, percentage of plasma cells infiltrates in bone marrow aspiration, ISS, serum free light chain and negatively correlated with hemoglobin, albumin (p < 0.5).

CONCLUSION

Ga-68 Pentixafor PET/CT is a promising tracer and the only available non-invasive tool to assess the whole-body disease burden of CXCR4 receptors in staging and follow-up of MM. In addition, it has a vital role in the development of CXCR4-targeted theranostics. Dual tracer imaging using F-18 FDG and Ga-68 Pentixafor PET/CT may help in evaluating tumor heterogeneity in MM and add prognostic value at diagnosis and follow-up.

Micro-Nano Convergence-Driven Radiotheranostic Revolution in Hepatocellular Carcinoma

Radiotherapy, as an important means of treating hepatocellular carcinoma (HCC), has shown unique therapeutic advantages, especially in patients who are unable to undergo surgery or transplantation. It mainly includes external radiotherapy, transarterial radioembolization and intratumoral radioactive particle implantation. However, under the influence of factors such as the hypoxic characteristics of the liver tumor microenvironment and the radioresistance of tumor cells, the effect of radiotherapy may be unstable and may cause side effects, affecting the quality of life of patients. In recent years, with the development of nanotechnology, drug delivery systems based on micro-nanomaterials have provided new solutions for improving the effect of radiotherapy for HCC. Despite this, the application of micro-nano drug delivery systems in the treatment of HCC still faces some challenges, mainly including the in vivo safety and in vivo metabolism of micro-nano materials. This article reviews the latest progress of micro-nano materials in the treatment of HCC, especially their application in radiosensitization and their clinical translation potential. This article systematically analyzes the role of micro-nanomaterials in external or internal radiotherapy sensitization and radioimmunotherapy and explores the advantages of micro-nanomaterials in improving the treatment effect of HCC.

Ultrasound Molecular Imaging of Blood Vessel Walls and Vulnerable Plaques via CXCR4-Targeted Nanoscale GVs

Purpose

C-X-C chemokine receptor 4 (CXCR4) mediates the inflammatory response of atherosclerotic vulnerable plaques (ASVP) and is a potential biomarker of atherosclerotic vulnerable plaques. The purpose of this study was to use the imaging ability of a new type of ultrasound contrast agent, nanoscale biosynthetic gas vesicles (GVs), on the vascular wall and to combine the specific ligand of CXCR4 to construct a targeted molecular probe to achieve early identification of atherosclerotic vulnerable plaques and guide clinical treatment decisions.

Materials and Methods

Compared three contrast agents: GVs, the micro-contrast agent SonoVue, and polyethylene glycol (PEG)-modified GVs in the carotid artery. The expression of CXCR4 in atherosclerotic plaques was demonstrated using flow cytometry and immunofluorescence experiments. Cell adhesion and in vivo ultrasound imaging experiments demonstrated their ability to target the nanoscale biosynthetic gas vesicles. The safety of GVs, PEG-GVs, and CXCR4-GVs was tested the CCk8 test, H&E staining, and serum detection.

Results

Strong CXCR4 expression was observed in plaques, whereas little expression was observed in normal vessels. GVs can produce stable contrast signals on the carotid artery walls of rats, whereas PEG-GVs can produce more lasting contrast signals on the carotid artery wall of rats. CXCR4-GVs exhibited excellent binding capability to ox-LDL-induced RAW264.7 cells. Animal experiments showed that compared with Con-GVs, CXCR4-GVs injected plaque imaging signal was stronger and more durable. In vitro scanning of vulnerable plaques in rats injected with fluorescent vesicles demonstrated that CXCR4-GVs oozed through the neovasculars within vulnerable plaques and aggregated in vulnerable plaques. Through the CCK8 test, H&E staining, and serum detection, the safety of CXCR4-GVs was confirmed.

Conclusion

CXCR4-GVs were constructed as targeted molecular probes, which can be proven to have good targeting properties to vulnerable atherosclerotic plaques.

Improvement of tumor-to-blood ratio of radioimmunoconjugates by poly(ethyleneimine)-containing chelating agent

OBJECTIVE

Monoclonal antibody (mAb)-based radioimmunoconjugates (RICs) exhibit marked tumor uptake in cancer imaging and therapy, although their high blood retention has limited the development of RICs. In our previous study, a trifunctional chelating agent with a cationic poly(ethyleneimine) (PEI) structure of tetraethylenepentamine (PEI4), maleimide-DOTA-PEI4 (MDI4), improved the tumor-to-blood ratio of RICs by increasing tumor retention compared with a conventional bifunctional chelating agent. In this study, we developed a novel chelating agent composed of a maleimide moiety, DOTA derivative, and two PEI4 structures as a PEI4-2 unit, maleimide-DOTA-PEI4-2 (MDI4-2), a design for a highly cationized chelating agent to synthesize RICs. The properties of MDI4-2 were compared with MDI4 to evaluate the effect of the PEI4-2 unit on the pharmacokinetics of RICs.

METHODS

Trastuzumab and 111In were selected as a model mAb and radiometal, respectively. Trastuzumab-based RICs were synthesized using MDI4-2 by two-step radiolabeling, wherein conjugation with mAbs is followed by radiolabeling of chelating agents, to obtain trastuzumab-[111In]In-MDI4-2 ([111In]In-TMDI4-2). The immunoreactivity and residualizing properties of [111In]In-TMDI4-2 were evaluated using human epidermal growth factor receptor 2 (HER2)/neu-expressing SK-OV-3 cells. A biodistribution assay using SK-OV-3 tumor-bearing mice was also performed for [111In]In-TMDI4-2 and the results were compared with trastuzumab-[111In]In-MDI4 ([111In]In-TMDI4).

RESULTS

[111In]In-TMDI4-2 was successfully synthesized by two-step radiolabeling at a radiochemical yield of 37.7%. The immunoreactivity of [111In]In-TMDI4-2 was determined as 81.7%, suggesting the maintained binding ability through radiolabeling steps. The internalization assay revealed equivalent internalizing properties of [111In]In-TMDI4-2 to [111In]In-TMDI4. In the biodistribution assay, [111In]In-TMDI4-2 exhibited lower blood retention of radioactivity to and comparable tumor uptake with [111In]In-TMDI4, resulting in an improved tumor-to-blood ratio. These in vitro and in vivo results indicate that the PEI4-2 unit largely contributed to the decrease in the blood radioactivity of RICs without compromising the tumor uptake.

CONCLUSION

MDI4-2 with the PEI4-2 unit exhibited favorable properties for designing RICs with an improved tumor-to-blood ratio.

Improving Affinity while Reducing Kidney Uptake of CXCR4-Targeting Radioligands Derived from the Endogenous Antagonist EPI-X4

The C-X-C chemokine receptor 4 (CXCR4) is highly upregulated in most cancers, making it an ideal target for delivering radiation therapy to tumors. We previously demonstrated the feasibility of targeting CXCR4 in vivo using a radiolabeled derivative of EPI-X4, an endogenous CXCR4 antagonist, named DOTA-K-JM#173. However, this derivative showed undesirable accumulation in the kidneys, which would limit its clinical use. In this study, we identified that removing a positive charge from the peptide sequence significantly reduced renal uptake. We evaluated a series of optimized derivatives lacking this positive charge, in vitro and in vivo in a xenografted athymic nude mice model, after radiolabeling with 177Lu. The most promising derivatives were further assessed in vivo after 68Ga labeling. Among them, we identified DOTA-JM#173 and D-L1-DOTA-JM#173, where the D-Ile1 was replaced by D-Leu1, two optimized derivatives with a lysine residue removed. These two molecules represent the most advanced DOTA-conjugated ligands derived from EPI-X4 for CXCR4-directed theranostic applications, offering enhanced potential for targeted cancer treatment.

C-X-C motif chemokine receptor 4-directed PET signal in the arterial tree is not consistently linked to calcified plaque burden and cardiovascular risk

Purpose: To establish the extent, distribution and frequency of in-vivo vessel wall [68Ga]Ga-PentixaFor uptake and to determine its relationship with calcified atherosclerotic plaque burden (CAP) and cardiovascular risk factors (CVRF). Methods: 65 oncological patients undergoing [68Ga]Ga-PentixaFor PET/CT were assessed. Radiotracer uptake (target-to-background ratio [TBR]) and CAP burden (including number of CAP sites, calcification circumference and thickness) in seven major vessel segments per patient were determined. We then investigated associations of vessel wall uptake with CAP burden, cardiovascular risk (CVRF and European Society of Cardiology [ESC] SCORE2/SCORE2-OP risk chart) and image noise (determined by coefficient of variation [CoV] from unaffected liver parenchyma). Results: We identified 1292 sites of high focal [68Ga]Ga-PentixaFor uptake (PentixaFor+ sites) in the vessel wall in 65/65 (100%) patients, with concomitant calcification in 385/1292 (29.8%) sites. There were no significant associations between vessel wall uptake and CAP burden (number of PentixaFor+ sites: r ≤ 0.18, P ≥ 0.14; PentixaFor+ TBR: r ≤ 0.08, P ≥ 0.54). The number of PentixaFor+ sites showed a moderate correlation with cardiovascular risk (ESC SCORE2/SCORE2-OP, r = 0.30; number of CVRF, r = 0.26; P = 0.04, respectively), but failed to reach significance for PentixaFor+ TBR (r ≤ 0.18, P ≥ 0.22). In univariable regression analysis, body mass index (odds ratio [OR] 1.08, 95%-confidence interval [CI] 1.02-1.14) and CoV (OR, 1.07; CI, 1.05-1.10) were linked to TBR and the number of PentixaFor+ sites (P < 0.01, respectively), while injected activity was only associated with the latter imaging parameter (OR, 0.99; CI, 0.98-1.00; P = 0.04). In multivariable regression, injected activity (OR, 1.00; CI, 0.99-1.00) and CoV (OR, 1.06; CI, 1.06-1.07) remained significantly associated with the number of PentixaFor+ sites (P < 0.01, respectively). CoV, however, was the only parameter significantly linked to PentixaFor+ TBR on multivariable analysis (OR, 1.02; CI, 1.01-1.03; P < 0.01). Conclusion: On a visual and quantitative level, high focal [68Ga]Ga-PentixaFor uptake in the arterial tree was not consistently linked to vessel wall calcification or cardiovascular risk. Image noise, however, may account for a substantial portion of apparent vessel wall uptake.

PET Imaging in Dementia: Mini-Review and Canadian Perspective for Clinical Use

PET imaging is increasingly recognized as an important diagnostic tool to investigate patients with cognitive disturbances of possible neurodegenerative origin. PET with 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG), assessing glucose metabolism, provides a measure of neurodegeneration and allows a precise differential diagnosis among the most common neurodegenerative diseases, such as Alzheimer's disease, frontotemporal dementia or dementia with Lewy bodies. PET tracers specific for the pathological deposits characteristic of different neurodegenerative processes, namely amyloid and tau deposits typical of Alzheimer's Disease, allow the visualization of these aggregates in vivo. [18F]FDG and amyloid PET imaging have reached a high level of clinical validity and are since 2022 investigations that can be offered to patients in standard clinical care in most of Canada.This article will briefly review and summarize the current knowledge on these diagnostic tools, their integration into diagnostic algorithms as well as perspectives for future developments.

Chemokine Receptor 4-Targeted PET/CT with [68Ga]pentixather in Newly Diagnosed Multiple Myeloma: a Comparative Study with [68Ga]pentixafor PET/CT

PURPOSE

This study aimed to compare the detection rate of [68Ga]pentixather PET/CT and [68Ga]pentixafor PET/CT in newly diagnosed multiple myeloma (NDMM) patients, and to explore the value of [68Ga]pentixather PET/CT for tumor load assessment.

METHODS

Nineteen NDMM Patients were prospectively recruited and underwent both [68Ga]pentixather PET/CT and [68Ga]pentixafor PET/CT. A positive PET scan was defined as the presence of PET-positive focal bone lesions, paraskeletal disease, extramedullary plasmacytoma, or diffuse bone marrow uptake. Lesion numbers, SUVmax and PET-related tumor burden values were compared. The correlations between PET-related tumor burden and clinical risk stratification were analyzed.

RESULTS

[68Ga]pentixather PET/CT showed a tendency of higher positive rate compared with [68Ga]pentixafor PET/CT [94.7% (18/19) vs. 78.9% (15/19), p > 0.05]. Among 14 patients with 151 matched focal bone lesions, [68Ga]pentixather PET detected more or equal number of lesions in 13 patients, and demonstrated higher uptake value than 68 Ga-pentixafor PET [SUVmax, 16.8 (9.0, 23.8) vs. 13.4 (6.5, 20.4), p < 0.001]. For PET related-tumor burden, positive correlations of total bone marrow uptake (TBmU) (r = 0.9540, p < 0.0001) and SUVmean of total bone marrow (r = 0.9632, p < 0.0001) in two PET scans were observed. Higher TBmU [7864.9 (5549.2, 11,616.2) vs. 5383.4(4102.7, 11,041.8), p < 0.001], SUVmean of total bone marrow [1.4 (1.1, 2.2) vs. 1.1 (0.7, 2.1), p < 0.001] were demonstrated on [68Ga]pentixather PET than [68Ga]pentixafor PET. And the level of TBmU in [68Ga]pentixather PET and [68Ga]pentixafor PET were both elevated in Durie-Salmon Staging (DSS) III than DSS I (p < 0.01).

CONCLUSIONS

[68Ga]pentixather PET/CT performed a non-inferior capability for tumor detection compared to [68Ga]pentixafor PET/CT in NDMM patients. [68Ga]pentixather PET/CT can assess tumor load in MM patients and depict a significantly higher PET-related total tumor burden than [68Ga]pentixafor PET/CT.

Nuclear medicine imaging in non-seminomatous germ cell tumors: lessons learned from the past failures

There is an unmet need for a more accurate molecular imaging radiotracer in the field of non-seminomatous germ cell tumors (NSGCT). The clinical problem is that no single imaging modality is able to differentiate teratoma from necrotic tissue in NSGCTs, which the nuclear medicine techniques are no exception. The exponential growth in the list of potentially promising radiotracers may hold promise in the future for imaging of NSGCTs. Here, we have reviewed the past efforts and potential future advances in this field.

[68 Ga]Ga-CXCR4 PET/CT imaging in high-grade glioma for assessment of CXCR4 receptor expression

PURPOSE

Gliomas account for 75 % of primary malignant CNS tumors. High-grade glioma (CNS WHO grades 3 and 4) have an unfavorable treatment response and poor outcome. CXCR4 is a G protein-coupled receptor that plays an important part in the signaling pathway between cancer cells and tumor microenvironment. CXCR4 overexpression has been shown in a variety of cancers. In this study, we evaluate the potential value of [68Ga]Ga-Pentixafor as a PET/CT CXCR4-probe for in vivo assessment of CXCR4 expression in patients with high-grade glioma and its correlation with tumor grade.

MATERIALS AND METHODS

[68Ga]Ga-CXCR4 PET/CT was performed in the prospective single-center study in treatment-naïve biopsy-proven patients with high-grade glioma. The acquired images were analyzed qualitatively and semi-quantitatively.

RESULT

A total of 26 patients (mean age: 53.3±14.4 years, 11 women, 15 men) were enrolled. CNS WHO grade 3 pathology was seen in 19 % (5/26) of the sample. The patient-based sensitivity of 68Ga-CXCR4 was 96.2 %. Overall, 28 pathologic lesions were detected, leading to a lesion-based sensitivity of 96.4 %. The median (IQR) SUVmax of grade 4 lesions was substantially greater than the grade 3(3.03(2.5-3.7) vs. 1.51(1.2-1.8), p = 0.0145).). The highest tracer activity of organs -beside bladder as the main excretion reservoir-was in lymphoid tissue of Waldeyer's ring (mean SUVmax: 7.41), and spleen (mean SUVmax: 6.62).

CONCLUSION

In conclusion, this new application for [68Ga]Ga-Pentixafor PET tracer exhibits excellent visual and semi-quantitative diagnostic properties. Further studies are warranted.

[99mTc]-PentixaTec SPECT/CT for Imaging of Chemokine Receptor 4 Expression After Myocardial Infarction

BACKGROUND

Accumulation of CXCR4 (C-X-C motif chemokine receptor 4)-positive immune cells after acute myocardial infarction (AMI) can be visualized by positron emission tomography. For a broader clinical application, there is a need for CXCR4-directed radiotracers labeled with isotopes that can be used with single-photon emission computed tomography (SPECT). We report on the detection of CXCR4 expression after AMI in humans using the novel tracer [99mTc]-PentixaTec.

METHODS

In this retrospective analysis, 9 patients with AMI after mechanical revascularization underwent myocardial inflammation imaging with [99mTc]-PentixaTec SPECT/computed tomography and rest perfusion SPECT imaging. Tracer uptake in the infarcted area, spleen, bone marrow, and blood pool were used for semiquantitative analysis and calculation of signal-to-background ratios. The extent and intensity of SPECT-derived inflammatory changes were compared with serological markers and perfusion defects.

RESULTS

CXCR4-directed SPECT was positive in all patients. Increased CXCR4 expression was only detected in areas with diminished perfusion corresponding to the affected vessel in coronary angiography, with a signal-to-background ratio (infarcted area-to-blood pool) of 2.36±0.74. Uptake in bone marrow and spleen showed a significant correlation with CXCR4 expression in the infarcted areas (r=0.73 and P=0.03 for spleen and r=0.81 and P=0.008 for bone marrow, respectively). The extent and intensity of SPECT-derived inflammatory changes showed no significant association with serum troponin, CK (creatine kinase), leukocyte, or CRP (C-reactive protein) levels.

CONCLUSIONS

This is the first report of in vivo CXCR4 imaging after AMI using a 99mTc-labeled tracer. Increased CXCR4 expression was observed locally in the infarcted region and was related to a systemic inflammatory response in the reticuloendothelial system. This proof-of-concept investigation demonstrates the general feasibility of evaluating the inflammation-related CXCR4 expression in the myocardium after AMI using conventional scintigraphy or SPECT and might, thus, broaden its worldwide application in clinical practice.

New PET Tracers for Lymphoma

While functional imaging with [18F]Fluoro-deoxy-glucose positron emission tomography (PET)/computed tomography is a well-established imaging modality in most lymphoma entities, novel tracers addressing cell surface receptors, tumor biology, and the microenvironment are being developed. Especially, with the emergence of immuno-PET targeting surface markers of lymphoma cells, a new imaging modality of immunotherapies is evolving, which might especially aid in relapsed and refractory disease stages. This review highlights different new PET tracers in indolent and aggressive lymphoma subtypes and summarizes the current state of immuno-PET imaging in lymphoma.

Exploring innovative strides in radiolabeled nanoparticle progress for multimodality cancer imaging and theranostic applications

Multimodal imaging unfolds as an innovative approach that synergistically employs a spectrum of imaging techniques either simultaneously or sequentially. The integration of computed tomography (CT), magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), positron emission tomography (PET), and optical imaging (OI) results in a comprehensive and complementary understanding of complex biological processes. This innovative approach combines the strengths of each method and overcoming their individual limitations. By harmoniously blending data from these modalities, it significantly improves the accuracy of cancer diagnosis and aids in treatment decision-making processes. Nanoparticles possess a high potential for facile functionalization with radioactive isotopes and a wide array of contrast agents. This strategic modification serves to augment signal amplification, significantly enhance image sensitivity, and elevate contrast indices. Such tailored nanoparticles constructs exhibit a promising avenue for advancing imaging modalities in both preclinical and clinical setting. Furthermore, nanoparticles function as a unified nanoplatform for the co-localization of imaging agents and therapeutic payloads, thereby optimizing the efficiency of cancer management strategies. Consequently, radiolabeled nanoparticles exhibit substantial potential in driving forward the realms of multimodal imaging and theranostic applications. This review discusses the potential applications of molecular imaging in cancer diagnosis, the utilization of nanotechnology-based radiolabeled materials in multimodal imaging and theranostic applications, as well as recent advancements in this field. It also highlights challenges including cytotoxicity and regulatory compliance, essential considerations for effective clinical translation of nanoradiopharmaceuticals in multimodal imaging and theranostic applications.

Discovery of novel CXCR4 inhibitors for the treatment of inflammation by virtual screening and biological evaluation

C-X-C chemokine receptor type 4 (CXCR4) exerts considerable influence on the pathogenesis of inflammatory disorders and offers a potent avenue for drug intervention. This research utilizes a hybrid virtual screening methodology constructed using computer-aided drug design to discover novel CXCR4 inhibitors for the treatment of inflammation. First, a compound library was screened by Lipinski's five rules and adsorption, distribution, metabolism, excretion and toxicity properties. Second, the HypoGen algorithm was used in constructing a 3D-QSAR pharmacophore model and verify it layer by layer, and the obtained optimal pharmacophore 1 (Hypo 1) was used as a 3D query for compound screening. Then, hit compounds were obtained through molecular docking (Libdock and CDOCKER). The toxicity of the compounds to MDA-MB-231 cells was evaluated in vitro, and their binding affinity to the target was evaluated according to how they compete with 12G5 antibody for CXCR4 on the surfaces of the MDA-MB-231 cells. Compound Hit14 showed the strongest binding affinity among the hit compounds and inhibited cell migration and invasion in Matrigel invasion and wound healing assay at a concentration of 100 nM, demonstrating a better effect than AMD3100. Western Blot experiments further showed that Hit14 blocked the CXCR4/CXCL12-mediated phosphorylation of Akt. Meanwhile, cellular thermal displacement assay analysis showed that CXCR4 protein bound to Hit14 had high thermal stability. Finally, through in vivo experiments, we found that Hit14 inhibited mouse ear inflammation and reduced ear swelling and damage. Therefore, Hit14 is a promising drug for the further development of CXCR4 inhibitors for inflammation treatment.

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

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

Progression of radio-labeled molecular imaging probes targeting chemokine receptors

Chemokine receptors are significantly expressed in the surface of most inflammatory cells and tumor cells. Guided by chemokines, inflammatory cells which express the relevant chemokine receptors migrate to inflammatory lesions and participate in the evolution of inflammation diseases. Similarly, driven by chemokines, immune cells infiltrate into tumor lesions not only induces alterations in the tumor microenvironment, disrupting the efficacy of tumor therapies, but also has the potential to selectively target tumoral cells and diminish tumor progression. Chemokine receptors, which are significantly expressed on the surface of tumor cell membranes, are regulated by chemokines and initiate tumor-associated signaling pathways within tumor cells, playing a complex role in tumor progression. Based on the antagonists targeting chemokine receptors, radionuclide-labeled molecular imaging probes have been developed for the emerging application of molecular imaging in diseases such as tumors and inflammation. The value and limitations of molecular probes in disease imaging are worth reviewing.

Advances in PET Imaging of the CXCR4 Receptor: [68Ga]Ga-PentixaFor

[68Ga]Ga-PentixaFor, a PET agent targeting CXCR4 is emerging as a versatile radiotracer with promising applications in oncology, cardiology and inflammatory disease. Preclinical work in various cancer cell lines have demonstrated high specificity and selectivity. In human investigations of several tumors, the most promising applications may be in multiple myeloma, certain lymphomas and myeloproliferative neoplasms. In the nononcologic setting, [68Ga]Ga-PentixaFor could greatly improve detection for primary aldosteronism and other endocrine abnormalities. Similarly, atherosclerotic disease and other inflammatory conditions could also benefit from enhanced identification by CXCR4 targeting. Rapidly cleared from the body with a favorable imaging and radiation dosimetry profile that has been already studied in over 1000 patients, [68Ga]Ga-PentixaFor is a worthy agent for further clinical exploration with potential for theranostic applications in hematologic malignancies.

Enantioselective Synthesis of Carbon-11-Labeled Amino Acids and Peptides

Radiolabeled amino acids (AAs), their derivatives, and peptides are essential radiotracers in nuclear imaging. Despite its potential, the preparation of enantiopure radiopharmaceuticals poses several challenges, demanding a great need for rapid and stereocontrolled reactions. This chapter describes a highly stereoselective carbon-11 alkylation of Schiff bases, to obtain radiolabeled AAs and small peptides. The method uses chiral quaternary ammonium salt phase-transfer catalyst with two alkylating agents, namely, [11C]methyl iodide and [11C]benzyl iodide. This methodology allows the radiolabeling of AAs and peptides with excellent regioselectivity and enantiomeric or diastereomeric excess.

Preparation of [68Ga]GaCl3 Using a Cyclotron

Recent developments in 68Ga-radiopharmaceuticals, including a number of regulatory approvals for clinical use, has created a hitherto unprecedented demand for 68Ga. Reliable access to enough 68Ga to meet growing clinical demand using only 68Ge/68Ga generators has been problematic in recent years. To address this challenge, we have optimized the direct production of 68Ga on a cyclotron via the 68Zn(p,n)68Ga reaction using a liquid target. This protocol describes the cyclotron-based production of [68Ga]GaCl3 implemented at the University of Michigan using a liquid target on GE PETtrace instrumentation. The protocol provides 56 ± 4 mCi (n = 3) of [68Ga]GaCl3 that meets the necessary quality control criteria to use for the preparation of 68Ga-radiopharmaceuticals for human use.

Design of a New 99mTc-radiolabeled Cyclo-peptide as Promising Molecular Imaging Agent of CXCR4 Receptor: Molecular Docking, Synthesis, Radiolabeling, and Biological Evaluation

INTRODUCTION

C-X-C Chemokine receptor type 4 (CXCR4) is often overexpressed or overactivated in different types and stages of cancer disease. Therefore, it is considered a promising target for imaging and early detection of primary tumors and metastasis. In the present research, a new cyclo-peptide radiolabelled with 99mTc, 99mTc-Cyclo [D-Phe-D-Tyr-Lys (HYNIC)- D-Arg-2-Nal-Gly-Lys(iPr)], was designed based on the parental LY251029 peptide, as a potential in vivo imaging agent of CXCR4-expressing tumors.

METHODS

The radioligand was successfully prepared using the method of Fmoc solid-phase peptide synthesis and was evaluated in biological assessment. Molecular docking findings revealed high affinity (binding energy of -9.7 kcal/mol) and effective interaction of Cyclo [D-Phe- D-Tyr-Lys (HYNIC)-D-Arg-2-Nal-Gly-Lys(iPr)] in the binding pocket of CXCR4 receptor (PDB code: 3OE0) as well.

RESULT

The synthesized peptide and its purity were assessed by both reversed-phase high-performance liquid chromatography (RP-HPLC) and mass spectroscopy. High stability (95%, n = 3) in human serum and favorable affinity (Kd = 28.70 ± 13.56 nM and Bmax = 1.896 ± 0.123 fmol/mg protein) in the B16-F10 cell line resulted. Biodistribution evaluation findings and planar image interpretation of mice both showed high affinity and selectivity of the radiotracer to the CXCR4 receptors.

CONCLUSION

Therefore, the findings indicate this designed radioligand could be used as a potential SPECT imaging agent in highly proliferated CXCR4 receptor tumors.

Melittin: a possible regulator of cancer proliferation in preclinical cell culture and animal models

BACKGROUND

Melittin is a water-soluble cationic peptide derived from bee venom that has been thoroughly studied for the cure of different cancers. However, the unwanted interactions of melittin produce hemolytic and cytotoxic effects that hinder their therapeutic applications. To overcome the shortcomings, numerous research groups have adopted different approaches, including conjugation with tumor-targeting proteins, gene therapy, and encapsulation in nanoparticles, to reduce the non-specific cytotoxic effects and potentiate their anti-cancerous activity.

PURPOSE

This article aims to provide mechanistic insights into the chemopreventive activity of melittin and its nanoversion in combination with standard anti-cancer drugs for the treatment of cancer.

METHODS

We looked over the pertinent research on melittin's chemopreventive properties in online databases such as PubMed and Scopus.

CONCLUSION

In the present article, the anti-cancerous effects of melittin on different cancers have been discussed very nicely, as have their possible mechanisms of action to act against different tumors. Besides, it interacts with different signal molecules that regulate the diverse pathways of cancerous cells, such as cell cycle arrest, apoptosis, metastasis, angiogenesis, and inflammation. We also discussed the recent progress in the synergistic combination of melittin with standard anti-cancer drugs and a nano-formulated version of melittin for targeted delivery to improve its anticancer potential.

[99mTc]Tc-PentixaTec: development, extensive pre-clinical evaluation, and first human experience

PURPOSE

The clinical success non-invasive imaging of CXCR4 expression using [68 Ga]Ga-PentixaFor-PET warrants an expansion of the targeting concept towards conventional scintigraphy/SPECT with their lower cost and general availability. To this aim, we developed and comparatively evaluated a series of 99mTc-labeled cyclic pentapeptides based on the PentixaFor scaffold.

METHODS

Six mas3-conjugated CPCR4 analogs with different 4-aminobenzoic acid (Abz)-D-Ala-D-Arg-aa3 linkers (L1-L6) as well as the corresponding HYNIC- and N4-analogs of L6-CPCR4 were synthesized via standard SPPS. Competitive binding studies (IC50 and IC50inv) were carried out using Jurkat T cell lymphoma cells and [125I]FC-131 as radioligand. Internalization kinetics were investigated using hCXCR4-overexpressing Chem-1 cells. Biodistribution studies and small animal SPECT/CT imaging (1 h p.i.) were carried out using Jurkat xenograft bearing CB17/SCID mice. Based on the preclinical results, [99mTc]Tc-N4-L6-CPCR4 ([99mTc]Tc-PentixaTec) was selected for an early translation to the human setting. Five patients with hematologic malignancies underwent [99mTc]Tc-N4-L6-CPCR4 SPECT/planar imaging with individual dosimetry.

RESULTS

Of the six mas3-conjugated peptides, mas3-L6-CPCR4 (mas3-dap-r-a-Abz-CPCR4) showed the highest CXCR4 affinity (IC50 = 5.0 ± 1.3 nM). Conjugation with N4 (N4-L6-CPCR4) further improved hCXCR4 affinity to 0.6 ± 0.1 nM. [99mTc]Tc-N4-L6-CPCR4 also showed the most efficient internalization (97% of total cellular activity at 2 h) and the highest tumor accumulation (8.6 ± 1.3% iD/g, 1 h p.i.) of the compounds investigated. Therefore, [99mTc]Tc-N4-L6-CPCR4 (termed [99mTc]Tc-PentixaTec) was selected for first-in-human application. [99mTc]Tc-PentixaTec was well tolerated, exhibits a favorable biodistribution and dosimetry profile (2.1-3.4 mSv per 500 MBq) and excellent tumor/background ratios in SPECT and planar imaging.

CONCLUSION

The successive optimization of the amino acid composition of the linker structure and the N-terminal 99mTc-labeling strategies (mas3 vs HYNIC vs N4) has provided [99mTc]Tc-PentixaTec as a novel, highly promising CXCR4-targeted SPECT agent for clinical application. With its excellent CXCR4 affinity, efficient internalization, high uptake in CXCR4-expressing tissues, suitable clearance/biodistribution characteristics, and favorable human dosimetry, it holds great potential for further clinical use.

Diagnostic value of [ 68 Ga]Ga-Pentixafor versus [ 18 F]FDG PET/CTs in non-small cell lung cancer: a head-to-head comparative study

OBJECTIVE

In this study, we aimed to compare the diagnostic value of [ 68 Ga]Ga-Pentixafor and [ 18 F]FDG PET/CT in the evaluation of non-small cell lung cancer (NSCLC) patients.

METHODS

Patients with pathology-proven NSCLC were prospectively included. Patients underwent [ 18 F]FDG and [ 68 Ga]Ga-Pentixafor PET/CT within 1 week. All suspicious lesions were interpreted as benign or malignant, and the corresponding PET/CT semi-quantitative parameters were recorded. A two-sided P -value <0.05 was considered significant.

RESULTS

Twelve consecutive NSCLC patients (mean age: 60 ± 7) were included. All patients underwent both [ 18 F]FDG and [ 68 Ga]Ga-Pentixafor PET/CT scans with a median interval of 2 days. Overall, 73 abnormal lesions were detected, from which 58 (79%) were concordant between [ 18 F]FDG and [ 68 Ga]Ga-Pentixafor PET/CT. All primary tumors were clearly detectable in both scans visually. Also, [ 68 Ga]Ga-Pentixafor PET/CT demonstrated rather comparable results with [ 18 F]FDG PET/CT scan in detecting metastatic lesions. However, malignant lesions demonstrated significantly higher SUVmax and SUVmean in [ 18 F]FDG PET/CT ( P -values <0.05). Regarding the advantages, [ 68 Ga]Ga-Pentixafor depicted two brain metastases that were missed by [ 18 F]FDG PET/CT. Also, a highly suspicious lesion for recurrence on [ 18 F]FDG PET/CT scan was correctly classified as benign by subsequent [ 68 Ga]Ga-Pentixafor PET/CT.

CONCLUSION

[ 68 Ga]Ga-Pentixafor PET/CT was concordant with [ 18 F]FDG PET/CT in detecting primary NSCLC tumors and could visualize the majority of metastatic lesions. Moreover, this modality was found to be potentially helpful in excluding tumoural lesions when the [ 18 F]FDG PET/CT was equivocal, as well as in detecting brain metastasis where [ 18 F]FDG PET/CT suffers from poor sensitivity. However, the count statistics were significantly lower.

Peptide-Based Agents for Cancer Treatment: Current Applications and Future Directions

Peptide-based strategies have received an enormous amount of attention because of their specificity and applicability. Their specificity and tumor-targeting ability are applied to diagnosis and treatment for cancer patients. In this review, we will summarize recent advancements and future perspectives on peptide-based strategies for cancer treatment. The literature search was conducted to identify relevant articles for peptide-based strategies for cancer treatment. It was performed using PubMed for articles in English until June 2023. Information on clinical trials was also obtained from ClinicalTrial.gov. Given that peptide-based strategies have several advantages such as targeted delivery to the diseased area, personalized designs, relatively small sizes, and simple production process, bioactive peptides having anti-cancer activities (anti-cancer peptides or ACPs) have been tested in pre-clinical settings and clinical trials. The capability of peptides for tumor targeting is essentially useful for peptide-drug conjugates (PDCs), diagnosis, and image-guided surgery. Immunomodulation with peptide vaccines has been extensively tested in clinical trials. Despite such advantages, FDA-approved peptide agents for solid cancer are still limited. This review will provide a detailed overview of current approaches, design strategies, routes of administration, and new technological advancements. We will highlight the success and limitations of peptide-based therapies for cancer treatment.

Clinical Advances and Perspectives in Targeted Radionuclide Therapy

Targeted radionuclide therapy has become increasingly prominent as a nuclear medicine subspecialty. For many decades, treatment with radionuclides has been mainly restricted to the use of iodine-131 in thyroid disorders. Currently, radiopharmaceuticals, consisting of a radionuclide coupled to a vector that binds to a desired biological target with high specificity, are being developed. The objective is to be as selective as possible at the tumor level, while limiting the dose received at the healthy tissue level. In recent years, a better understanding of molecular mechanisms of cancer, as well as the appearance of innovative targeting agents (antibodies, peptides, and small molecules) and the availability of new radioisotopes, have enabled considerable advances in the field of vectorized internal radiotherapy with a better therapeutic efficacy, radiation safety and personalized treatments. For instance, targeting the tumor microenvironment, instead of the cancer cells, now appears particularly attractive. Several radiopharmaceuticals for therapeutic targeting have shown clinical value in several types of tumors and have been or will soon be approved and authorized for clinical use. Following their clinical and commercial success, research in that domain is particularly growing, with the clinical pipeline appearing as a promising target. This review aims to provide an overview of current research on targeting radionuclide therapy.

Next generation radiotheranostics promoting precision medicine

Radiotheranostics is a field of rapid growth with some approved treatments including 131I for thyroid cancer, 223Ra for osseous metastases, 177Lu-DOTATATE for neuroendocrine tumors, and 177Lu-PSMA (prostate-specific membrane antigen) for prostate cancer, and several more under investigation. In this review, we will cover the fundamentals of radiotheranostics, the key clinical studies that have led to current success, future developments with new targets, radionuclides and platforms, challenges with logistics and reimbursement and, lastly, forthcoming considerations regarding dosimetry, identifying the right line of therapy, artificial intelligence and more.

Diagnostics of atherosclerosis: Overview of the existing methods

Atherosclerosis was and remains an extremely common and serious health problem. Since the elderly are most at risk of cardiovascular risk, and the average life expectancy is increasing, the spread of atherosclerosis and its consequences increases as well. One of the features of atherosclerosis is its asymptomaticity. This factor makes it difficult to make a timely diagnosis. This entails the lack of timely treatment and even prevention. To date, in the arsenal of physicians, there is only a limited set of methods to suspect and fully diagnose atherosclerosis. In this review, we have tried to briefly describe the most common and effective methods for diagnosing atherosclerosis.

Contribution of nuclear medicine to the diagnosis and management of primary brain tumours

Positron emission tomography (PET) is a powerful tool that can help physicians manage primary brain tumours at diagnosis and follow-up. In this context, PET imaging is used with three main types of radiotracers: ¹⁸F-FDG, amino acid radiotracers, and ⁶⁸Ga conjugated to somatostatin receptor ligands (SSTRs). At initial diagnosis, ¹⁸F-FDG helps to characterize primary central nervous system (PCNS) lymphomas and high-grade gliomas, amino acid radiotracers are indicated for gliomas, and SSTR PET ligands are indicated for meningiomas. Such radiotracers provide information on tumour grade or type, assist in directing biopsies and help with treatment planning. During follow-up, in the presence of symptoms and/or MRI modifications, the differential diagnosis between tumour recurrence and post-therapeutic changes, in particular radiation necrosis, may be challenging, and there is strong interest in using PET to evaluate therapeutic toxicity. PET may also contribute to identifying specific complications, such as postradiation therapy encephalopathy, encephalitis associated with PCNS lymphoma, and stroke-like migraine after radiation therapy (SMART) syndrome associated with glioma recurrence and temporal epilepsy, originally illustrated in this review. This review summarizes the main contribution of PET to the diagnosis, management, and follow-up of brain tumours, specifically gliomas, meningiomas, and primary central nervous system lymphomas.

Gallium-68 Labelled Radiopharmaceuticals for Imaging Inflammatory Disorders

Inflammation is an important component of several chronic and debilitating diseases that result in significant morbidity and mortality. This is best evidenced within the cardiovascular system where it may manifest as atherosclerosis or myocarditis, and at the extreme end of the spectrum as myocardial infarction, ventricular remodeling, or cardiac failure. Early non-invasive detection and monitoring of inflammation in these and other settings may better guide patient management with resultant improved outcomes. Key role players in inflammation pathophysiology include chemokines, macrophages, neutrophils, fibroblasts, integrins, and reactive oxygen species, amongst others. Examples of receptor expression and over-expression include somatostatin receptors, CXCR4-, folate-, mannose-, TSPO- receptors and secretion of various vascular adhesion molecules (such as VCAM and ICAM). Gallium-68-based PET offers imaging possibilities for nearly all the major pathophysiological role players in inflammation, with mounting recent interest in macrophage differentiation, various forms of receptor expression and secretion of chemokines and vascular adhesion molecules. The advantages in terms of logistics and costs of having generator-produced PET probes available is well known, and a ⁶⁸Ga-based tracer provides easily translatable theranostic possibilities to especially Lu-177. Some of the more versatile and better validated Ga-68-based inflammation probes include ⁶⁸Ga-DOTA-TATE/NOC/TOC, ⁶⁸Ga-NOTA-RGD, ⁶⁸Ga-CXCR4, ⁶⁸Ga-citrate and ⁶⁸Ga-FAPI.

Automated synthesis and quality control of [68Ga]Ga-PentixaFor using the Gaia/Luna Elysia-Raytest module for CXCR4 PET imaging

BACKGROUND

[⁶⁸Ga]Ga-PentixaFor is a promising radiotracer for positron emission tomography imaging of several human tumors overexpressing the chemokine receptor-4 (CXCR4). CXCR4 overexpression has been demonstrated in patients with hematologic malignancies, solid cancers, as well as cardiovascular pathologies of inflammatory origins. However, its radio synthesis is not yet fully developed in France, and existing methods do not use our type of synthesis module. Therefore, we aimed at developing a [⁶⁸Ga]Ga-PentixaFor synthesis with Gaia/Luna Elysia-Raytest module to use it in clinical purpose.

RESULTS

12 syntheses were carried out by varying the temperature conditions and radiolabeling times, and led to choose specific labelling conditions with the Gaia/Luna Elysia-Raytest module: 97 °C, 4 min. The mean synthesis time of the 3 validation runs under good manufacturing practice (GMP) was 24 min 27 s (± 8 s), and the mean radiochemical yield was 87.0% [standard deviation (SD) 6.67%]. Different quality control parameters were also evaluated in accordance with European Pharmacopeia: radiochemical and radionuclidic purity, pH, sterility, stability and endotoxins levels. The average radiochemical purity was 99.1% (SD 0.25%) assessed by instant thin layer chromatography and 99.8% (SD 0.092%) assessed by high pressure liquid chromatography. average [⁶⁸Ge] breakthrough was 1.48 × 10^-5%, under the recommended level of 0.001%. We assessed the stability of the radiotracer up to 4 h at room temperature (no augmentation of the [⁶⁸Ga] chloride in the final product, i.e. radiochemical purity (RCP) > 98.5%). The endotoxins levels were < 5 EU/mL, and the pH was 6.5 (same for the three syntheses).

CONCLUSION

The [⁶⁸Ga]Ga-PentixaFor synthesis process developed on the Gaia/Luna Elysia-Raytest module has fulfilled all acceptance criteria for injectable radiopharmaceutical products regarding the European Pharmacopeia. The radiochemical purity, stability, efficacy, as well as the microbiological quality of the three GMP batches were found to be good. The robustness of the synthesis process may be suitable for multi-dose application in clinical settings.

Immunoexpression of CXCL12 and CXCR4 in Radicular Cysts, Dentigerous Cysts, and Odontogenic Keratocysts

The aim of this study was to evaluate the immunoexpression of chemokine CXCL12 and its receptor CXCR4 in radicular cysts (RCs), dentigerous cysts (DCs), and odontogenic keratocysts (OKCs), and to correlate the findings with morphologic parameters of RCs (inflammatory infiltrate and cystic epithelium). Twenty RCs, 20 DCs, and 20 OKCs were submitted to immunohistochemistry. The percentages of cytoplasmic (CXCL12 and CXCR4) and nuclear (CXCR4) staining in epithelial and fibrous capsule cells were determined. RCs and DCs exhibited higher epithelial expression of CXCL12 than OKCs ( P <0.05). The expression of CXCL12 in the fibrous capsule was higher in DCs than in RCs and OKCs ( P <0.05). Higher cytoplasmic expression of CXCR4 was observed in the epithelial lining and fibrous capsule of RCs and DCs compared with OKCs ( P <0.05). In the fibrous capsule, DCs exhibited higher nuclear expression of CXCR4 than OKCs ( P <0.05). No significant differences in the immunoexpression of CXCL12 or CXCR4 were observed according to the morphologic parameters of RCs ( P >0.05). Strong positive correlations were found between cytoplasmic and nuclear expression of CXCR4 in the epithelial lining of RCs and DCs and in the fibrous capsule of all groups ( P <0.05). The results suggest the participation of CXCL12 and CXCR4 in the pathogenesis of RCs, DCs, and OKCs. These proteins may be particularly relevant for the development of odontogenic cysts with less aggressive biological behavior, irrespective of their nature (inflammatory or developmental). In RCs, the expression of CXCL12 and CXCR4 may not be related to the intensity of the inflammatory infiltrate or the status of cystic epithelium.

Predicting Microenvironment in CXCR4- and FAP-Positive Solid Tumors-A Pan-Cancer Machine Learning Workflow for Theranostic Target Structures

(1) Background: C-X-C Motif Chemokine Receptor 4 (CXCR4) and Fibroblast Activation Protein Alpha (FAP) are promising theranostic targets. However, it is unclear whether CXCR4 and FAP positivity mark distinct microenvironments, especially in solid tumors. (2) Methods: Using Random Forest (RF) analysis, we searched for entity-independent mRNA and microRNA signatures related to CXCR4 and FAP overexpression in our pan-cancer cohort from The Cancer Genome Atlas (TCGA) database-representing n = 9242 specimens from 29 tumor entities. CXCR4- and FAP-positive samples were assessed via StringDB cluster analysis, EnrichR, Metascape, and Gene Set Enrichment Analysis (GSEA). Findings were validated via correlation analyses in n = 1541 tumor samples. TIMER2.0 analyzed the association of CXCR4 / FAP expression and infiltration levels of immune-related cells. (3) Results: We identified entity-independent CXCR4 and FAP gene signatures representative for the majority of solid cancers. While CXCR4 positivity marked an immune-related microenvironment, FAP overexpression highlighted an angiogenesis-associated niche. TIMER2.0 analysis confirmed characteristic infiltration levels of CD8+ cells for CXCR4-positive tumors and endothelial cells for FAP-positive tumors. (4) Conclusions: CXCR4- and FAP-directed PET imaging could provide a non-invasive decision aid for entity-agnostic treatment of microenvironment in solid malignancies. Moreover, this machine learning workflow can easily be transferred towards other theranostic targets.

[68Ga] Ga-Pentixafor diffuse bilateral Adrenal & Breast uptake in a patient with High-grade Glioma: A note of caution on normal variants

[⁶⁸Ga] Ga-labeled C-X-C motif receptor4 as a novel radio-ligand using PET/CT has been investigated for tracing various kinds of solid and hematopoietic malignancies in recent years. High-grade Glioma (WHO classification 2016 grade III and IV) shows elevated levels of CXCR4 ligand expression in the affected tumoral cells. Healthy and non-affected organ cells express low-level CXCR4 ligands density. We performed [⁶⁸Ga] Ga-Pentixafor (Pars-Cixafor™) PET/CT in a patient with high-grade Glioma (anaplastic oligodendroglioma WHO grade III) with no other documented medical condition and history. In addition to the Pentixafor-avid tumor remnant in the PET/CT images, we observed mild symmetrical bilateral uptake in the fibro glandular tissue of the breasts and moderate CXCR4(Pentixafor) avidity in both adrenal glands without any discernable pathology and abnormal density changes in the CT component of the study. Attention should be paid to the interpreting [⁶⁸Ga] Ga-Pentixafor PET/CT examination and its normal uptakes and variants.

The Role of G Protein-Coupled Receptor Kinase 6 Regulation in Inflammation and Pain

The G protein-coupled receptor kinase 6 is associated with inflammation and pathological pain. Impairment of GRK6 expression was described in chronic inflammatory diseases such as rheumatoid arthritis and this was shown to be accompanied by an imbalance of downstream signaling pathways. Here, we discuss novel aspects of GRK6 interaction and its impact upon hyperalgesia and inflammatory processes. In this review, we compile important findings concerning GRK6 regulation for a better pathophysiological understanding of the intracellular interaction in the context of inflammation and show clinical implications-for example, the identification of possible therapy goals in the treatment of chronic inflammatory hyperalgesia.

Current Status of 68Ga-Pentixafor in Solid Tumours

Chemokine receptor CXCR4 is overexpressed in neoplasms and its expression is related to tumour invasion, metastasis and aggressiveness. ⁶⁸Ga-Pentixafor is used to non-invasively image the expression of CXCR4 in tumours and has been widely used in haematological malignancies. Recent evidence shows that therapies targeting CXCR4 can increase the chemosensitivity of the tumour as well as inhibit tumour metastasis and aggressiveness. ⁶⁸Ga-Pentixafor has shown promise as an elegant radiotracer to aid in the selection of patients whose tumours demonstrate CXCR4 overexpression and who therefore may benefit from novel therapies targeting CXCR4. In addition, its therapeutic partners ¹⁷⁷Lu- and ⁹⁰Y-Pentixather have been investigated in the treatment of patients with advanced haematological malignancies, and initial studies have shown a good treatment response in metabolically active lesions. ⁶⁸Ga-Pentixafor in solid tumours complements ¹⁸F-FDG by providing prognostic information and selecting patients who may benefit from therapies targeting CXCR4. This review summarises the available literature on the potential applications of ⁶⁸Ga-Pentixafor in solid tumours.

Reduced splenic uptake on 68Ga-Pentixafor-PET/CT imaging in multiple myeloma - a potential imaging biomarker for disease prognosis

Beyond being a key factor for tumor growth and metastasis in human cancer, C-X-C motif chemokine receptor 4 (CXCR4) is also highly expressed by a number of immune cells, allowing for non-invasive read-out of inflammatory activity. With two recent studies reporting on prognostic implications of the spleen signal in diffusion-weighted magnetic resonance imaging in patients with plasma cell dyscrasias, the aim of this study was to correlate splenic ⁶⁸Ga-Pentixafor uptake in multiple myeloma (MM) with clinical parameters and to evaluate its prognostic impact.

Methods: Eighty-seven MM patients underwent molecular imaging with ⁶⁸Ga-Pentixafor-PET/CT. Splenic CXCR4 expression was semi-quantitatively assessed by peak standardized uptake values (SUV_peak) and corresponding spleen-to-bloodpool ratios (TBR) and correlated with clinical and prognostic features as well as survival parameters.

Results:⁶⁸Ga-Pentixafor-PET/CT was visually positive in all MM patients with markedly heterogeneous tracer uptake in the spleen. CXCR4 expression determined by ⁶⁸Ga-Pentixafor-PET/CT corresponded with advanced disease and was inversely associated with the number of previous treatment lines as compared to controls or untreated smouldering multiple myeloma patients (SUV_peakSpleen 4.06 ± 1.43 vs. 6.02 ± 1.16 vs. 7.33 ± 1.40; P < 0.001). Moreover, reduced splenic ⁶⁸Ga-Pentixafor uptake was linked to unfavorable clinical outcome. Patients with a low SUV_peakSpleen (<3.35) experienced a significantly shorter overall survival of 5 months as compared to 62 months in patients with a high SUV_peakSpleen >5.79 (P < 0.001). Multivariate Cox analysis confirmed SUV_peakSpleen as an independent predictor of survival (HR 0.75; P = 0.009).

Conclusion: These data suggest that splenic ⁶⁸Ga-Pentixafor uptake might provide prognostic information in pre-treated MM patients similar to what was reported for diffusion-weighted magnetic resonance imaging. Further research to elucidate the underlying biologic implications is warranted.

Simultaneous PET/MRI: The future gold standard for characterizing motor neuron disease-A clinico-radiological and neuroscientific perspective

Neuroimaging assessment of motor neuron disease has turned into a cornerstone of its clinical workup. Amyotrophic lateral sclerosis (ALS), as a paradigmatic motor neuron disease, has been extensively studied by advanced neuroimaging methods, including molecular imaging by MRI and PET, furthering finer and more specific details of the cascade of ALS neurodegeneration and symptoms, facilitated by multicentric studies implementing novel methodologies. With an increase in multimodal neuroimaging data on ALS and an exponential improvement in neuroimaging technology, the need for harmonization of protocols and integration of their respective findings into a consistent model becomes mandatory. Integration of multimodal data into a model of a continuing cascade of functional loss also calls for the best attempt to correlate the different molecular imaging measurements as performed at the shortest inter-modality time intervals possible. As outlined in this perspective article, simultaneous PET/MRI, nowadays available at many neuroimaging research sites, offers the perspective of a one-stop shop for reproducible imaging biomarkers on neuronal damage and has the potential to become the new gold standard for characterizing motor neuron disease from the clinico-radiological and neuroscientific perspectives.

COVID-19 vaccination, implications for PET/CT image interpretation and future perspectives

Introduction

The present paper aims to systematically review the literature on COVID-19 vaccine-related findings in patients undergoing PET/CT.

Methods

The search algorithms included the following combination of terms: "PET" OR "positron emission tomography" AND "COVID"; "PET" OR "positron emission tomography" AND "COVID" AND "vaccination"; "PET" OR "positron emission tomography" AND "COVID", AND "autoimmune".

Results

We selected 17 articles which were assessed for quality and included in the systematic analysis. The most frequent vaccine-related signs on PET/CT were the deltoid [18F]FDG uptake and axillary hypermetabolic lymph nodes, which were described in 8-71% and 7-90% of the patients, respectively. Similarly, frequency of these findings using other tracers than [18F]FDG was greatly variable. This large variability was related to the variability in time elapsed between vaccination and PET/CT, and the criteria used to define positivity. In addition, vaccine-related findings were detected more frequently in young and immunocompetent patients than in elderly and immunocompromised ones.

Discussion

Therefore, awareness on vaccination status (timing, patient characteristics, and concurrent therapies) and knowledge on patterns of radiopharmaceutical uptake are necessary to properly interpret PET/CT findings.

Novel Endometrial Cancer Models Using Sensitive Metastasis Tracing for CXCR4-Targeted Therapy in Advanced Disease

Advanced endometrial cancer (EC) lacks therapy, thus, there is a need for novel treatment targets. CXCR4 overexpression is associated with a poor prognosis in several cancers, whereas its inhibition prevents metastases. We assessed CXCR4 expression in EC in women by using IHC. Orthotopic models were generated with transendometrial implantation of CXCR4-transduced EC cells. After in vitro evaluation of the CXCR4-targeted T22-GFP-H6 nanocarrier, subcutaneous EC models were used to study its uptake in tumor and normal organs. Of the women, 91% overexpressed CXCR4, making them candidates for CXCR4-targeted therapies. Thus, we developed CXCR4⁺ EC mouse models to improve metastagenesis compared to current models and to use them to develop novel CXCR4-targeted therapies for unresponsive EC. It showed enhanced dissemination, especially in the lungs and liver, and displayed 100% metastasis penetrance at all clinically relevant sites with anti-hVimentin IHC, improving detection sensitivity. Regarding the CXCR4-targeted nanocarrier, 60% accumulated in the SC tumor; therefore, selectively targeting CXCR4⁺ cancer cells, without toxicity in non-tumor organs. Our CXCR4⁺ EC models will allow testing of novel CXCR4-targeted drugs and development of nanomedicines derived from T22-GFP-H6 to deliver drugs to CXCR4⁺ cells in advanced EC. This novel approach provides a therapeutic option for women with metastatic, high risk or recurrent EC that have a dismal prognosis and lack effective therapies.

Radiotheranostic Agents in Hematological Malignancies

Radioimmunotherapy (RIT) is a cancer treatment that combines radiation therapy with tumor-directed monoclonal antibodies (Abs). Although RIT had been introduced for the treatment of CD20 positive non-Hodgkin lymphoma decades ago, it never found a broad clinical application. In recent years, researchers have developed theranostic agents based on Ab fragments or small Ab mimetics such as peptides, affibodies or single-chain Abs with improved tumor-targeting capacities. Theranostics combine diagnostic and therapeutic capabilities into a single pharmaceutical agent; this dual application can be easily achieved after conjugation to radionuclides. The past decade has seen a trend to increased specificity, fastened pharmacokinetics, and personalized medicine. In this review, we discuss the different strategies introduced for the noninvasive detection and treatment of hematological malignancies by radiopharmaceuticals. We also discuss the future applications of these radiotheranostic agents.

Radionuclide imaging and therapy directed towards the tumor microenvironment: a multi-cancer approach for personalized medicine

Targeted radionuclide theranostics is becoming more and more prominent in clinical oncology. Currently, most nuclear medicine compounds researched for cancer theranostics are directed towards targets expressed in only a small subset of cancer types, limiting clinical applicability. The identification of cancer-specific targets that are (more) universally expressed will allow more cancer patients to benefit from these personalized nuclear medicine–based interventions. A tumor is not merely a collection of cancer cells, it also comprises supporting stromal cells embedded in an altered extracellular matrix (ECM), together forming the tumor microenvironment (TME). Since the TME is less genetically unstable than cancer cells, and TME phenotypes can be shared between cancer types, it offers targets that are more universally expressed. The TME is characterized by the presence of altered processes such as hypoxia, acidity, and increased metabolism. Next to the ECM, the TME consists of cancer-associated fibroblasts (CAFs), macrophages, endothelial cells forming the neo-vasculature, immune cells, and cancer-associated adipocytes (CAAs). Radioligands directed at the altered processes, the ECM, and the cellular components of the TME have been developed and evaluated in preclinical and clinical studies for targeted radionuclide imaging and/or therapy. In this review, we provide an overview of the TME targets and their corresponding radioligands. In addition, we discuss what developments are needed to further explore the TME as a target for radionuclide theranostics, with the hopes of stimulating the development of novel TME radioligands with multi-cancer, or in some cases even pan-cancer, application.

Adrenal functional imaging

Given the more widespread use of conventional imaging techniques such as magnetic resonance imaging or computed tomography, recent years have witnessed an increased rate of incidental findings in the adrenal gland and those adrenal masses can be either of benign or malignant origin. In this regard, routinely conducted morphological imaging cannot always reliably distinguish between cancerous and noncancerous lesions. As such, those incidental adrenal masses trigger further diagnostic work-up, including molecular functional imaging providing a non-invasive read-out on a sub-cellular level. For instance, [¹⁸F]FDG positron emission tomography (PET) as a marker of glucose consumption has been widely utilized to distinguish between malignant vs benign adrenal lesions. In addition, more adrenal cortex-targeted radiotracers for PET or single photon emission computed tomography have entered the clinical arena, e.g., Iodometomidate or IMAZA, which are targeting CYP11B enzymes, or Pentixafor identifying CXCR4 in adrenal tissue. All these tracers are used for diagnosing tumors deriving from the adrenal cortex. Furthermore, radiolabeled MIBG, DOPA, and DOTATOC/-TATE are radiotracers that are quite helpful in detecting pheochromocytomas originating from the adrenal medulla. Of note, after having quantified the retention capacities of the target in-vivo, such radiotracers have the potential to be used as anti-cancer therapeutics by using their therapeutic equivalents in a theranostic setting. The present review will summarize the current advent of established and recently introduced molecular image biomarkers for investigating adrenal masses and highlight its transformation beyond providing functional status towards image-guided therapeutic approaches, in particular in patients afflicted with adrenocortical carcinoma.

Radiolabeled Nanocarriers as Theranostics-Advancement from Peptides to Nanocarriers

Endogenous targeted radiotherapy is emerging as an integral modality to treat a variety of cancer entities. Nevertheless, despite the positive clinical outcome of the treatment using radiolabeled peptides, small molecules, antibodies, and nanobodies, a high degree of hepatotoxicity and nephrotoxicity still persist. This limits the amount of dose that can be injected. In an attempt to mitigate these side effects, the use of nanocarriers such as nanoparticles (NPs), dendrimers, micelles, liposomes, and nanogels (NGs) is currently being explored. Nanocarriers can prolong circulation time and tumor retention, maximize radiation dosage, and offer multifunctionality for different targeting strategies. In this review, the authors first provide a summary of radiation therapy and imaging and discuss the new radiotracers that are used preclinically and clinically. They then highlight and identify the advantages of radio-nanomedicine and its potential in overcoming the limitations of endogenous radiotherapy. Finally, the review points to the ongoing efforts to maximize the use of radio-nanomedicine for efficient clinical translation.

Positron emission tomography-magnetic resonance imaging as a research tool in musculoskeletal conditions

Compared to positron emission tomography/computed tomography (PET/CT), the uptake of PET- magnetic resonance imaging (MRI) has been slow, even more so in clinical practice compared to the (pre-)clinical research setting. However, for applications in musculoskeletal (MSK) research, the combination of PET and MRI into a single modality offers attractive advantages over other imaging modalities. Most importantly, MRI has exquisite soft-tissue detail without the use of contrast agents or ionizing radiation, superior bone marrow visualization, and an extensive spectrum of distinct multiparametric assessment methods. In the preclinical setting, the introduction of PET inserts for small-animal MRI machines has proven to be a successful concept in bringing this technology to the lab. Initial hurdles in quantification have been mainly overcome in this setting. In parallel, a promising range of radiochemistry techniques has been developed to create multimodality probes that offer the possibility of simultaneously querying different metabolic pathways. Not only will these applications help in elucidating disease mechanisms, but they can also facilitate drug development. The clinical applications of PET/MRI in MSK are still limited, but encouraging initial results with novel radiotracers suggest a high potential for use in various MSK conditions, including osteoarthritis, rheumatoid arthritis, ankylosing spondylitis and inflammation and infection. Further innovations will be required to bring down the cost of PET/MRI to justify a broader clinical implementation, and remaining issues with quality control and standardization also need to be addressed. Nevertheless, PET/MRI is a powerful platform for MSK research with distinct qualities that are not offered by other techniques.

Molecular Imaging in Multiple Myeloma-Novel PET Radiotracers Improve Patient Management and Guide Therapy

Due to its proven value in imaging of multiple myeloma (MM), including staging, prognostication, and assessment of therapy response, 2-deoxy-2-[18F]fluoro-D-glucose (FDG) positron emission tomography (PET) is utilized extensively in the clinic. However, its accuracy is hampered by imperfect sensitivity (e.g., so-called FDG-negative MM) as well as specificity (e.g., inflammatory processes), with common pitfalls including fractures and degenerative changes. Novel approaches providing a read-out of increased protein or lipid membrane syntheses, such as [11C]methionine and [11C]choline or the C-X-C motif chemokine receptor 4-targeting radiotracer [68Ga]Pentixafor, have already been shown to be suitable adjuncts or alternatives to FDG. In the present focused review, those imaging agents along with their theranostic potential in the context of MM are highlighted.

Melittin Prevents Metastasis of Epidermal Growth Factor-Induced MDA-MB-231 Cells through The Inhibition of The SDF-1α/CXCR4 Signaling Pathway

Objective

Melittin is one of the natural components of bee venom (Apis mellifera), and its anticancer and antimetastatic properties have been well established, but the underlying mechanism remains elusive. The MDA-MB-231 is a triplenegative cell line that is highly aggressive and invasive. Besides, many critical proteins are involved in tumor invasion and metastasis. In this study, we investigated whether melittin inhibits the migration and metastasis of epidermal growth factor (EGF)-induced MDA-MB-231 cells via the suppression of SDF-1α/CXCR4 and Rac1-mediated signaling pathways.

Materials and Methods

In this experimental study, cells were treated with melittin (0.5-4 μg/ml), and the toxicity of melittin was assessed by the MTT assay. Afterward, the migration assay was conducted to measure the degree of the migration of EGF-induced cells. The western blot technique was performed to analyze the rate of Rac1, p-Rac1, SDF- 1α, and CXCR4 expression in different groups.

Results

The results demonstrated that melittin markedly suppressed the migration of EGF-induced cells and decreased the expression of p-Rac1, CXCR4, and SDF-1α proteins.

Conclusion

The results of the present study suggested that the anti-tumor properties of melittin could be through the blocking of the SDF-1α/CXCR4 signaling pathway, which is beneficial for the reduction of tumor migration and invasion.

Kirenol: A Potential Natural Lead Molecule for a New Drug Design, Development, and Therapy for Inflammation

Kirenol, a potential natural diterpenoid molecule, is mainly found in Sigesbeckia species. Kirenol has received a lot of interest in recent years due to its wide range of pharmacological actions. In particular, it has a significant ability to interact with a wide range of molecular targets associated with inflammation. In this review, we summarise the efficacy and safety of kirenol in reducing inflammation, as well as its potential mechanisms of action and opportunities in future drug development. Based on the preclinical studies reported earlier, kirenol has a good therapeutic potential against inflammation involved in multiple sclerosis, inflammatory bowel disorders, diabetic wounds, arthritis, cardiovascular disease, bone damage, and joint disorders. We also address the physicochemical and drug-like features of kirenol, as well as the structurally modified kirenol-derived molecules. The inhibition of pro-inflammatory cytokines, reduction in the nuclear factor kappa-B (NF-κB), attenuation of antioxidant enzymes, stimulation of heme-oxygenase-1 (HO-1) expression, and nuclear factor erythroid 2-related factor 2 (Nrf2) phosphorylation are among the molecular mechanisms contributing to kirenol's anti-inflammatory actions. Furthermore, this review also highlights the challenges and opportunities to improve the drug delivery of kirenol for treating inflammation. According to the findings of this review, kirenol is an active molecule against inflammation in numerous preclinical models, indicating a path to using it for new drug discovery and development in the treatment of a wide range of inflammations.

Multimodal molecular imaging evaluation for early diagnosis and prognosis of cholangiocarcinoma

Cholangiocarcinoma (CCA) is an aggressive and lethal malignancy with limited therapeutic options. Despite recent advances in diagnostic imaging for CCA, the early diagnosis of CCA and evaluation of tumor invasion into the bile duct and its surrounding tissues remain challenging. Most patients with CCA are diagnosed at an advanced stage, at which treatment options are limited. Molecular imaging is a promising diagnostic method for noninvasive imaging of biological events at the cellular and molecular level in vivo. Molecular imaging plays a key role in the early diagnosis, staging, and treatment-related evaluation and management of cancer. This review will describe different methods for molecular imaging of CCA, including nuclear medicine, magnetic resonance imaging, optical imaging, and multimodal imaging. The main challenges and future directions in this field are also discussed.