GPC3-targeted immunoPET imaging of hepatocellular carcinomas

Nanobody-Based PET Imaging of CD47 Expression in Thyroid Carcinoma

Thyroid cancer is the most common malignant tumor in the endocrine system. A significant correlation has been established between elevated CD47 expression and the progression of thyroid carcinoma. This study aims to evaluate the diagnostic potential of immuno-positron emission tomography (immunoPET) utilizing CD47-targeting nanobodies in thyroid cancer tumor models. Immunohistochemistry (IHC) was employed to evaluate CD47 expression in patients with thyroid cancer, as well as in anaplastic thyroid carcinoma (ATC) xenograft tumor (OCUT-2C) and differentiated thyroid cancer (DTC) xenograft tumors (TPC-1 and BCPAP). Two nanobodies, C2 and its albumin-binding derivative (ABDC2), specifically targeting CD47 were labeled with 68Ga. The tracers were evaluated using immunoPET imaging in models of thyroid cancer. IHC revealed that CD47 was highly expressed in 34.69% of the tumor tissues from patients with thyroid cancer. Additionally, high levels of CD47 expression were observed in OCUT-2C, TPC-1, and BCPAP tumor tissues. Micro-PET imaging using [68Ga]Ga-NOTA-C2 and [68Ga]Ga-NOTA-ABDC2 demonstrated clear visualization of OCUT-2C tumors. Notably, the tumor uptake of [68Ga]Ga-NOTA-ABDC2 was significantly higher than that of [68Ga]Ga-NOTA-C2 at each imaging time point. Additionally, [68Ga]Ga-NOTA-ABDC2 exhibited specific uptake in the TPC-1 and BCPAP models. This study confirmed that [68Ga]Ga-NOTA-ABDC2 as a innovative PET imaging radiotracer targeting CD47 presented specific and higher tumor uptake to accurately identify CD47 expression and diagnose thyroid cancer. The clinical application of these imaging strategies may aid in selecting patients for CD47-targeted therapies and evaluating their subsequent responses.

Immuno-PET Imaging of a 68Ga-Labeled Single-Domain Antibody for Detecting Tumor TIGIT Expression

Preclinical studies have shown that the expression of T cell immunoglobulin and the immunoreceptor tyrosine-based inhibitory motif domain (TIGIT) in the tumor microenvironment is associated with the efficacy of anti-TIGIT-based immunotherapy. This study aimed to develop a TIGIT single-domain antibody (sdAb)-based positron emission tomography (PET) radiotracer, [68Ga]Ga-NOTA-NABT3A1, and evaluate its characteristics. The NABT3A1 was modified with a NOTA derivative and radiolabeled with 68Ga. In vitro stability of [68Ga]Ga-NOTA-NABT3A1 was assessed in phosphate-buffered saline (PBS) and fetal bovine serum (FBS), along with its specificity for TIGIT stably transfected A375 Human melanoma cells (A375-TIGIT) was performed. In vivo imaging was conducted on A375-TIGIT tumor-bearing nude mice at different time points after the injection of [68Ga]Ga-NOTA-NABT3A1. The synthesized [68Ga]Ga-NOTA-NABT3A1 achieved a radiochemical yield of 70.56 ± 1.14% and purity levels of 95.80 ± 0.58% in PBS and 96.79 ± 1.69% in FBS at 2 h. Immuno-PET imaging revealed specific accumulation of [68Ga]Ga-NOTA-NABT3A1 in A375-TIGIT tumor-bearing nude mice, with a maximum uptake of 3.86 ± 0.29% injected dose/g at 0.5 h. Biodistribution and immunohistochemical analyses confirmed the in vivo imaging results. In conclusion, we successfully synthesized an NABT3A1-derived PET radiotracer with the potential to noninvasively assess TIGIT expression in tumors.

Interplay of GPC3, Hsa-miR-135b-3p, and FTLP3 in lung cancer metastasis

This study investigates crucial genes involved in lung cancer metastasis and their interactions within a Competitive endogenous RNA (ceRNA) regulatory network using comprehensive transcriptomic data from the TCGA and GEO databases. Differential expression analysis identified ten genes associated with lung cancer metastasis, with Glypican-3 (GPC3) emerging as a key mRNA through survival analysis. A ceRNA network involving GPC3, hsa-miR-135b-3p, and FTLP3 was constructed and validated in both cellular and animal models, elucidating their roles in cell migration, invasion, and tumorigenic potential. The analysis confirmed the significance of key genes like GPC3, with the FTLP3/hsa-miR-135b-3p/GPC3 axis playing a fundamental role in lung cancer progression. Additionally, the study identified correlations between GPC3 expression, immune cell infiltration and immune checkpoints, underscoring its impact on the immune landscape of lung cancer. Overexpression of FTLP3 effectively suppressed the migratory, invasive, and metastatic abilities of lung cancer cells, demonstrating the pivotal role of the FTLP3/hsa-miR-135b-3p/GPC3 ceRNA network in modulating tumor progression and immune responses. These results underscore its potential as a therapeutic target for managing lung cancer metastasis.

Development and Characterization of the [177Lu]Lu-Labeled Anti-CDH17 Nanobody Derivative for Radioimmunotherapy in the Gastric Cancer Xenograft Model

Cadherin 17 (CDH17) is highly expressed in digestive system cancers, and the potential of nanobodies targeting CDH17 as imaging probes and delivery vehicles for radioactive β-particles warrants exploration for their theranostic potential in CDH17-overexpressing gastric cancer (GC). In this study, we screened an anti-CDH17 nanobody library and constructed two antibodies: anti-CDH17 VHH (recombinant nanobody fused with a polyhistidine tag) and anti-CDH17 VHH-ABD (recombinant nanobody fused with an albumin-binding domain). VHH targeting CDH17 and its derivative VHH-ABD were conjugated with DOTA and labeled with radionuclide 177Lu. The pharmacokinetics and theranostic efficacy of these agents were evaluated in the GC xenograft models. [177Lu]Lu-VHH and [177Lu]Lu-VHH-ABD exhibited high radiochemical purity (>99%, n = 3) and successfully delineated CDH17-positive gastric cancer tissues on SPECT/CT imaging. Compared with the rapid renal clearance of [177Lu]Lu-VHH, [177Lu]Lu-VHH-ABD demonstrated prolonged circulation times with increased and sustained tumor accumulation. Survival experiments in the MKN-45 tumor model revealed that two doses of [177Lu]Lu-VHH-ABD effectively suppressed tumor growth, with limited systemic biotoxicity. Histological analysis using hematoxylin and eosin (H&E) staining and Ki67 immunohistochemistry confirmed structural disruption and low tumor cell proliferative activity in the tumor tissue. In preclinical studies, [177Lu]Lu-anti-CDH17 VHH-ABD demonstrated substantial antitumor efficacy with manageable toxicity, offering promising clinical potential as a viable therapeutic option for CDH17-overexpressing GC.

Challenges and opportunities in single-domain antibody-based tumor immunotherapy

Single-domain antibodies (sdAbs) have emerged as a promising tool in tumor immunotherapy, garnering significant attention in recent years due to their unique structure and superior properties. Unlike traditional antibodies, sdAbs exhibit several advantages, including small molecular weight, high stability, strong affinity, and high specificity. These characteristics enable sdAbs to effectively target and eliminate tumor cells within the complex tumor microenvironment. Moreover, their structural advantages enhance tissue penetration and reduce immunogenicity, thereby increasing their potential for clinical application. The potential applications of sdAbs include novel immune checkpoint inhibitors, bispecific antibody drugs, innovative immune cell therapies, antibody-drug conjugate therapies, and tumor molecular imaging diagnostics. Despite the promising prospects, several challenges of sdAb-based tumor immunotherapy still require further investigation. This review aims to summarize the status of sdAb-based immunotherapy, identify the challenges encountered, and evaluate the clinical research and application potential of sdAbs in this field.

Label-free determination of glypican-3 using PtPd@H-rGO nanocomposites decorated light-addressable potentiometric sensor

Glypican-3 (GPC3) is exclusively overexpressed in most Hepatocellular carcinoma (HCC) tissue but not in normal liver tissue, making it a promising biomarker for the precise detection of HCC. In this paper, a label-free light-addressable potentiometric sensor (LAPS) decorated by platinumpalladium-hemin-reduced graphene oxide nanocomposites (PtPd@H-rGO NCs) was constructed for determination of GPC3. The GPC3 aptamer (GPC3Apt) and PtPd@H-rGO NCs were modified on the surface of silicon-based LAPS chip to build sensitive unit of LAPS system. A readout photocurrent elicited from a modulated light source, registers the localized surface potential change. When a bias voltage is provided to the LAPS system, the GPC3-GPC3Apt complexes formed by the specific reaction between GPC3 and GPC3Apt at the sensing interface can cause the sensitive membrane surface potential to change, resulting in the photocurrent-voltage (I-V) curves generate a corresponding offset response. Therefore GPC3 concentration can be determined by monitoring the potential shifts (△V). Under optimal conditions, the potential shift is linearly related to the concentration of GPC3 in the range of 0.001-3.00 μg/mL with the limit of detection (LOD) of 0.0001 μg/mL. The LAPS has a good analytical performance with good specificity, reproducibility and stability, and can be used for the detection of GPC3 in actual serum samples, which provides a broad application prospect for the combined application of LAPS and aptamers in biooassay.

Whole-body visualization of SARS-CoV-2 biodistribution in vivo by immunoPET imaging in non-human primates

The COVID-19 pandemic has caused at least 780 million cases globally. While available treatments and vaccines have reduced the mortality rate, spread and evolution of the virus are ongoing processes. Despite extensive research, the long-term impact of SARS-CoV-2 infection is still poorly understood and requires further investigation. Routine analysis provides limited access to the tissues of patients, necessitating alternative approaches to investigate viral dissemination in the organism. We address this issue by implementing a whole-body in vivo imaging strategy to longitudinally assess the biodistribution of SARS-CoV-2. We demonstrate in a COVID-19 non-human primate model that a single injection of radiolabeled [89Zr]COVA1-27-DFO human monoclonal antibody targeting a preserved epitope of the SARS-CoV-2 spike protein allows longitudinal tracking of the virus by positron emission tomography with computed tomography (PET/CT). Convalescent animals exhibit a persistent [89Zr]COVA1-27-DFO PET signal in the lungs, as well as in the brain, three months following infection. This imaging approach also allows viral detection in various organs, including the airways and kidneys, of exposed animals during the acute infection phase. Overall, the technology we developed offers a comprehensive assessment of SARS-CoV-2 distribution in vivo and provides a promising approach for the non-invasive study of long-COVID pathophysiology.

Albumin-conjugation enables improved tumor targeting of aptamers via SPECT imaging

Aptamers are single-stranded oligonucleotides with specific spatial structures. They have been widely used in preclinical studies because of their high affinity and specificity for various biological targets. AS1411, an aptamer targeting the nucleolin overexpressed on the cancer cell membrane, is one of the most promising and extensively studied aptamers. However, extremely low bioavailability due to rapid renal excretion remains a great obstacle for aptamers' clinical translation. Human serum albumin (HSA), with long blood circulation and excellent biocompatibility, has been an attractive vehicle for extending drugs' blood half-life in the clinic. This work investigated the effect of an albumin-conjugated strategy in improving aptamers' tumor targeting in vivo for the first time by taking AS1411 as an example. HSA-AS1411 was synthesized via the maleimide-sulfhydryl reaction. The excellent serum stability and maintained target affinity of HSA-AS1411 were demonstrated in vitro. The pharmacokinetic analysis and tumor SPECT imaging studies revealed that HSA-AS1411 had over 14 times longer circulation half-life and superior tumor uptake than those of AS1411. The immunofluorescence staining of tumor tissues further indicated the improved tumor retention of AS1411 as a result of prolonged blood circulation. Therefore, the HSA-conjugated strategy has a promising prospect in improving aptamers' tumor targeting for clinical applications.

Multiplex immunohistochemistry to explore the tumor immune microenvironment in HCC patients with different GPC3 expression

OBJECTIVES

GPC3 has been recognized as a promising target for immunotherapy in hepatocellular carcinoma (HCC). However, the GPC3-targeted immunotherapies have shown limited therapeutic efficacy. The use of anti-PD-1/PD-L1 monoclonal antibodies in HCC treatment is considerably constrained. Furthermore, there is still a notable lack of understanding concerning the immune landscape in HCC, especially regarding varied GPC3 expression levels. Therefore, thorough exploration of the intricate tumor immune microenvironment at different GPC3 expression levels is essential for guiding and improving HCC treatment strategies.

METHODS

Sixty patients with HCC were enrolled in this study, receiving a first-line treatment that combined anti-angiogenesis targeted drugs and immunotherapy. Immunohistochemistry was used to assess the levels of GPC3 expression. Multiple immunohistochemical markers, such as CD8, PD-1, LAG3, TIGIT, TIM-3, CD103, Claudin18.2, PD-L1, CD4, Foxp3, CD68, CD163, GPC3, CD11C, CD14, CD66b, and HLA-DR, were used to characterize the immune microenvironment and spatial distribution of immune cells in HCC tumors with different levels of GPC3 expression. Cell expression levels and spatial distribution were determined by fluorescence staining and subsequent analysis of fluorescence intensity using the Panoramic Pathology Workstation (Pano ATLAS). This approach facilitated a detailed examination of cell characteristics and spatial information within the samples.

RESULTS

Based on the result of GPC3 immunohistochemical analysis, patients with strong positive GPC3 expression were classified as high GPC3 expression, while the others were classified as low GPC3 expression. Patients in the low GPC3 expression group had longer overall survival (OS) than in the high group (P = 0.003, HR = 2.9240). Further exploration of the immune microenvironment based on different GPC3 expression levels revealed that in high GPC3 expression group, the proportions of CD8+ T cells(P = 0.0435), TIM-3+ T cells(P = 0.0447), CD103+CD8+ tissue-resident T cells(P = 0.0410), CD11C+CD14-DC cells(P = 0.0497), CD11C+HLA-DR-DC cells(P = 0.0309), CD11C+CD14-HLA-DR-DC cells(P = 0.0233), and CD11C+CD14-CD66b-DC cells(P = 0.0474) were all higher compared to low expression group. At spatial distances of 10 μm, 20 μm, and 30 μm, the levels of CD8+ T cells were higher in the high expression group compared to the low expression group (high vs. low: P = 0.0281, P = 0.0236, P = 0.0220).

CONCLUSIONS

Multiple immunohistochemistry is a powerful technique for exploring the intricate immune microenvironment of hepatocellular carcinoma, enabling the precise identification of diverse cell subsets and their spatial distribution within the tumor microenvironment. This methodology provides valuable insights into the complex interactions and spatial organization of immune cells in the context of hepatocellular carcinoma progression. Low GPC3 expression in HCC patients indicates potential benefits from combined targeted and immunotherapy. Different levels of GPC3 expression levels can predict the effectiveness of targeted combination immunotherapy in HCC patients. Additionally, different GPC3 expression patterns in HCC patients correspond to unique tumor immune microenvironments, which have implications for guiding HCC treatment approaches.

Synthesis and Preclinical Evaluation of Dual-Specific Probe Targeting Glypican-3 and Prostate-Specific Membrane Antigen for Hepatocellular Carcinoma PET Imaging

Positron emission tomography (PET) is a promising modality for early diagnosis, accurate detection, and staging of hepatocellular carcinoma (HCC). Hereby, a dual-specific probe targeting Glypican-3 (GPC3) and prostate-specific membrane antigen (PSMA) was evaluated for HCC PET imaging. The probe was prepared by conjugating TJ12P2, a GPC3-targeting peptide previously reported by our group, to a highly potent PSMA inhibitor via a polyethylene glycol linker and further tethered to the 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) chelator. The resultant probe, NOTA-TJ12P2-PSMA, abbreviated as T2P, was labeled with gallium-68 and fluorine-18, respectively, and evaluated in murine HCC models of various levels of GPC3 and PSMA expression. Targeting specificity was confirmed by blocking studies. The synthesized [68Ga]Ga-T2P and [18F]AlF-T2P were stable in saline and fetal bovine serum for over 2 h, and bound to their respective targets with high affinity and specificity in cell assays. PET imaging at 60 min postinjection (p.i.) showed that [68Ga]Ga-T2P exhibited higher uptake (1.75 ± 0.16%ID/g) in Huh7 models with high expression of GPC3 and PSMA than gallium-68 labeled TJ12P2 (1.25 ± 0.07%ID/g, p < 0.01) or gallium-68 labeled PSMA-617 (1.07 ± 0.06%ID/g, p < 0.001). The uptake of [68Ga]Ga-T2P in Huh7 tumors was higher than that in PC-3 tumors with low expression of GPC3 or PSMA (0.55 ± 0.24%ID/g, p < 0.01). The uptake of [18F]AlF-T2P or [68Ga]Ga-T2P in the Huh7 tumor was substantially blocked by TJ12P2, TJ12P2 + PSMA, or T2P, but only partially blocked by PSMA. And the PSMA and TJ12P2 monomer blocking effect was less than that of TJ12P2 + PSMA and T2P. [18F]AlF-T2P had higher tumor-to-muscle ratios than [68Ga]Ga-T2P at 90 min postinjection (4.31 ± 0.10 vs 3.80 ± 0.17, p < 0.05) in Huh7 tumor models. To conclude, radiolabeled T2P exhibited a higher uptake and longer retention in Huh7 tumors than its monomeric counterparts. PET imaging via gallium-68 and fluorine-18 labeled T2P showed a similar imaging quality with comparable signal-to-background ratios. Our results demonstrate that T2P is a promising tool for future clinical diagnosis of HCC.

Radiopharmaceuticals and their applications in medicine

Radiopharmaceuticals involve the local delivery of radionuclides to targeted lesions for the diagnosis and treatment of multiple diseases. Radiopharmaceutical therapy, which directly causes systematic and irreparable damage to targeted cells, has attracted increasing attention in the treatment of refractory diseases that are not sensitive to current therapies. As the Food and Drug Administration (FDA) approvals of [177Lu]Lu-DOTA-TATE, [177Lu]Lu-PSMA-617 and their complementary diagnostic agents, namely, [68Ga]Ga-DOTA-TATE and [68Ga]Ga-PSMA-11, targeted radiopharmaceutical-based theranostics (radiotheranostics) are being increasingly implemented in clinical practice in oncology, which lead to a new era of radiopharmaceuticals. The new generation of radiopharmaceuticals utilizes a targeting vector to achieve the accurate delivery of radionuclides to lesions and avoid off-target deposition, making it possible to improve the efficiency and biosafety of tumour diagnosis and therapy. Numerous studies have focused on developing novel radiopharmaceuticals targeting a broader range of disease targets, demonstrating remarkable in vivo performance. These include high tumor uptake, prolonged retention time, and favorable pharmacokinetic properties that align with clinical standards. While radiotheranostics have been widely applied in tumor diagnosis and therapy, their applications are now expanding to neurodegenerative diseases, cardiovascular diseases, and inflammation. Furthermore, radiotheranostic-empowered precision medicine is revolutionizing the cancer treatment paradigm. Diagnostic radiopharmaceuticals play a pivotal role in patient stratification and treatment planning, leading to improved therapeutic outcomes in targeted radionuclide therapy. This review offers a comprehensive overview of the evolution of radiopharmaceuticals, including both FDA-approved and clinically investigated agents, and explores the mechanisms of cell death induced by radiopharmaceuticals. It emphasizes the significance and future prospects of theranostic-based radiopharmaceuticals in advancing precision medicine.

Preclinical evaluation and pilot clinical study of [68Ga]Ga-NOTA-H006 for non-invasive PET imaging of 5T4 oncofetal antigen

PURPOSE

Trophoblast glycoprotein, the so-called 5T4, is an oncofetal antigen expressed in many different cancers. However, no 5T4-specific radioligand is employed in the clinic for non-invasive diagnosis. Thus, the aim of the current study was to develop a PET radiotracer for imaging 5T4 expression in preclinical and clinical stages.

METHODS

A VHH library was constructed by camel immunization. The specificity of the VHHs toward 5T4 antigen was screened through phage display biopanning and periplasmic extract enzyme-linked immunosorbent assay. 1,4,7-Triazacyclononane-1,4,7-triacetate acid (NOTA) derivative was conjugated to the selected VHH. After radiolabeling, microPET/CT and ex vivo biodistribution were conducted using BxPC-3 and MDA-MB-468 tumor-bearing mice. Cold VHH was co-injected with the tracer to challenge its binding in vivo. For the pilot clinical study, PET/CT images were acquired at 1 h after injection of tracer in patients with pathologically confirmed primary and metastatic tumors.

RESULTS

A library with a capacity of 1.2 × 1012 colony-forming units was constructed after successful camel immunization. Nb1-40 with a median effect concentration of 0.43 nM was selected. After humanization, the resulting H006 maintained a high affinity towards 5T4. [68Ga]Ga-NOTA-H006 with the molar activities of 6.48-54.2 GBq/µmol was prepared with high radiochemical purity (> 98%). Using [68Ga]Ga-NOTA-H006, microPET/CT revealed a clear visualization of 5T4 expression in BxPC-3 tumor-bearing mice. Ex vivo biodistribution showed that the highest tumor-to-blood ratio (∼ 3-fold) and tumor-to-muscle ratio (∼ 5-fold) were achieved at 60 min post-injection. Co-injection of the cold H006 at a dose of 1.5 mg/kg significantly reduced the tumor uptake (p < 0.0001). In the pilot clinical study, [68Ga]Ga-NOTA-H006 demonstrated its capacity to map 5T4-positive lesions in humans and yielded a mean effective dose of 3.4 × 10- 2 mSv/MBq.

CONCLUSIONS

[68Ga]Ga-NOTA-H006, which can visualize 5T4 expression in vivo, has been successfully developed. This opens up opportunities for non-invasively studying 5T4 expression through nuclear medicine. Further clinical investigations are warranted to explore its clinical value in disease progression and companion diagnosis.

Exploring a new chapter in traditional Chinese medicine: The potential of Calculus bovis in liver cancer treatment

In the ongoing quest for new treatments in medicine, traditional Chinese medicine offers unique insights and potential. Recently, studies on the ability of Calculus bovis to inhibit M2-type tumour-associated macrophage polarisation by modulating the Wnt/β-catenin signalling pathway to suppress liver cancer have undoubtedly revealed new benefits and hope for this field of research. The purpose of this article is to comment on this study and explore its strengths and weaknesses, thereby providing ideas for the future treatment of liver cancer.

99mTc-Labeled D-Type PTP as a Plectin-Targeting Single-Photon Emission Computed Tomography Probe for Hepatocellular Carcinoma Imaging

Plectin, a scaffolding protein overexpressed in tumor cells, plays a significant role in hepatocellular carcinoma (HCC) proliferation, invasion, and migration. However, the use of L-type peptides for targeting plectin is hindered by their limited stability and retention. We designed a D-type plectin-targeting peptide (DPTP) and developed a novel single-photon emission computed tomography (SPECT) probe for HCC imaging. The DPTP targeting ability was evaluated in vitro using flow cytometry and ex vivo fluorescence imaging. 99mTc radiolabeling was performed using tricine and ethylenediamine-N,N'-diacetic acid (EDDA) as coligands after modification with 6-hydrazino nicotinamide (HYNIC) at the N termini of DPTP. The radiochemical purity (RCP), in vitro stability, and binding affinity of the prepared 99mTc-HYNIC-DPTP were analyzed. Tumor uptake, metabolic stability, biodistribution, and pharmacokinetics of 99mTc-HYNIC-DPTP were investigated and compared with those of 99mTc-labeled L-type PTP (99mTc-HYNIC-PTP) in HCC tumor-bearing mice. DPTP could be efficiently radiolabeled with 99mTc using the HYNIC/tricine/EDDA system with a high RCP and good in vitro stability. Compared with the L-type PTP, DPTP exhibited improved targeting ability, and 99mTc-HYNIC-DPTP displayed higher tumor uptake, better metabolic stability, longer blood circulation time, and lower kidney retention, resulting in superior imaging performance and biodistribution in vivo. 99mTc-HYNIC-DPTP has great potential as a novel SPECT probe for diagnosing HCC.

Gallium-68 Labeled Positron Emission Computed Tomography Tracer Targeting Glypican-3 with High Contrast for Hepatocellular Carcinoma Imaging

Hepatocellular carcinoma (HCC) represents the predominant form of primary liver cancer, yet early, precise, and noninvasive detection continues to pose a considerable clinical challenge. Glypican-3 (GPC3), a membrane-bound proteoglycan, is markedly overexpressed in most HCC cases, while exhibiting low expression in normal and hepatitis-affected liver tissues. Given its crucial role in malignant transformation and tumor progression, GPC3 emerges as a compelling target for imaging. In this study, we developed and evaluated 2 68Ga-labeled GPC3-targeted positron emission tomography (PET) probes, each incorporating either polyethylene glycol (PEG) or 4-(p-methylphenyl)butanoic acid (an albumin-binding moiety). Comparative analyses revealed that 68Ga-ALB-GBP, which includes the albumin-binding moiety, exhibited superior in vivo stability, enhanced tumor uptake, and an improved tumor-to-liver ratio relative to 68Ga-PEG2-GBP in subcutaneous HCC mouse models. Micro-PET/computed tomography imaging of orthotopic liver cancer with 68Ga-ALB-GBP demonstrated a tumor-to-liver ratio of 2.29 ± 0.13 and a tumor-to-muscle ratio of 13.03 ± 1.63 at 3 h postinjection, outperforming the performance of the clinically used 18F-fluorodeoxyglucose PET imaging. These findings suggest that 68Ga-ALB-GBP is a promising diagnostic tool for HCC and a strong candidate for clinical translation with potential utility in both diagnostic and therapeutic settings. Moreover, the incorporation of an albumin-binding moiety into PET tracers significantly extends blood circulation time, thereby enhancing bioavailability and facilitating high-contrast PET imaging.

CD70-Targeted Immuno-PET/CT Imaging of Clear Cell Renal Cell Carcinoma: A Translational Study

The diagnosis and surveillance of clear cell renal cell carcinoma (ccRCC) remains a clinical challenge. The high and specific expression of the cluster of differentiation 70 (CD70) in ccRCC makes it a potential diagnostic and therapeutic target. Methods: We detected and analyzed CD70 expression in various renal cell carcinomas (RCCs) and normal kidneys using immunohistochemical staining. Two novel CD70-specific single-domain antibodies, RCCB3 and RCCB6, were produced and labeled with 68Ga to develop radiotracers. We performed immuno-PET/CT imaging with [68Ga]Ga-NOTA-RCCB3 and [68Ga]Ga-NOTA-RCCB6 in subcutaneous ccRCC patient-derived xenograft models. We recruited 8 RCC patients in a pilot clinical trial (ClinicalTrials.gov identifier: NCT06148220) to evaluate the diagnostic utility of [68Ga]Ga-NOTA-RCCB3 and [68Ga]Ga-NOTA-RCCB6 immuno-PET/CT. Results: Expression of CD70 is associated with sex, tumor differentiation, tumor thrombus, necrosis, distant metastasis, and overall survival of RCC patients. RCCB3 and RCCB6 had high affinities for recombinant human CD70. Immuno-PET/CT imaging with [68Ga]Ga-NOTA-RCCB3 and [68Ga]Ga-NOTA-RCCB6 rapidly visualized subcutaneous ccRCC with clarity. Tumor uptake of [68Ga]Ga-NOTA-RCCB6 was significantly reduced after the blockade of CD70. [68Ga]Ga-NOTA-RCCB6 PET/CT in ccRCC patients outperformed traditional 18F-FDG PET/CT in specifically identifying CD70-positive ccRCC metastases. Conclusion: CD70-targeted immuno-PET/CT imaging with [68Ga]Ga-NOTA-RCCB6 or [68Ga]Ga-NOTA-RCCB3 is a precise and superior method for evaluating tumor burden and suspected metastases in ccRCC patients. This advancement in imaging technology has the potential to improve the clinical decision-making process for this patient cohort significantly.

Head-to-head study of [18F]FAPI-04 PET/CT and [18F]FDG PET/CT for non-invasive assessment of liver cancer and its immunohistochemical markers

OBJECTIVE

To compare the performance of [18F]FDG and [18F]FAPI-04 in PET/CT evaluation for liver cancer lesions, with a further exploration of the associations between PET semiquantitative data and immunohistochemical markers to liver cancer.

METHODS

Patients with suspected malignant liver lesions (MLL) underwent [18F]FDG and [18F]FAPI-04 PET/CT scanning. Liver lesions were visually classified as positive or negative based on their uptake level exceeding that of adjacent normal liver tissue. SUVmax and tumor-to-background ratio (TBR) were recorded for semi-quantitative analysis. Sensitivity, specificity and accuracy of each tracer were determined using pathological findings as the gold standard. Furthermore, immunohistochemical analysis provided the molecular characteristics of all MLLs. Comprehensive analysis explored correlations between these molecular markers and PET semiquantitative parameters (SUVmax andTBR) to identify potential associations.

RESULTS

The study enrolled 44 patients, with 39 confirmed cases of MLL, comprising 28 hepatocellular carcinomas (HCC) and 11 intrahepatic cholangiocarcinomas (ICC). For MLL detection, [18F]FAPI-04 and [18F]FDG exhibited sensitivities of 84.6% (33/39) and 76.9% (30/39), specificitiesy of 60% (3/5) and 100%(5/5), and accuracy of 81.8% (36/44) and 79.5%(35/44). Across all liver lesions, [18F]FAPI-04 significantly surpassed [18F]FDG in SUVmax(10.54 ± 6.72 VS. 7.68 ± 6.79) and TBR(4.35 ± 3.78 Vs. 3.17 ± 3.05). Notably, [18F]FAPI-04 displayed markebly elevated SUVmax in benign liver lesions (BLLs) (P = 0.032), HCCs (P = 0.005), and ICCs (P = 0.011). Lesions with hepatocyte negativity (P = 0.023), CD34 negativity(P = 0.044), and high Ki67 expression (> 30%) (P = 0.001) had higher SUVmax on [18F]FAPI-04. Additionally, ARG-1-negative lesions demonstrated higher TBR on [18F]FAPI-04 than ARG-1-positive lesions(P = 0.018). No significant SUVmax/TBR differences were observed with [18F]FDG based on these markers. A linear relationship was identified between Ki67 scores and SUVmax of [18F]FAPI-04 (R = 0.603, P < 0.001).

CONCLUSION

[18F]FAPI-04 exhibits superior performance over [18F]FDG in PET/CT evaluation of liver cancer, characterized by increased sensitivity and SUVmax/TBR. Significant correlations with molecular markers, including Ki67, suggest [18F]FAPI-04's potential for characterizing liver cancer subtypes and assessing tumor proliferation. However, further research is required to validate these findings and their clinical significance.

TRIAL REGISTRATION

NCT05485792, Registered 01 August 2022.

Trends in cancer imaging

Molecular imaging of cancer is a collaborative endeavor, uniting scientists and physicians from diverse fields. Such collaboration is actively developing and translating cutting-edge molecular imaging approaches to enhance the diagnostic landscape of human malignancies. The advent of positron emission tomography (PET) and PET imaging tracers has realized non-invasive target annotation and tumor characterization at the molecular level. In surgical procedures, novel imaging techniques, such as fluorescence or Cherenkov luminescence, help identify tumors and enhance surgical precision. Simultaneously, progress in imaging equipment, innovative algorithms, and artificial intelligence has opened avenues for next-generation cancer screening and imaging, augmenting the efficiency and accuracy of cancer diagnosis. In this review, we provide a panorama of molecular cancer imaging and ongoing developments in the field.

Developing targeted therapeutics for hepatocellular carcinoma: a critical assessment of promising phase II agents

INTRODUCTION

Hepatocellular carcinoma (HCC) is the sixth most common cancer worldwide and the first for primary liver tumors. In recent years greater therapeutic advancement was represented by employment of tyrosine kinase inhibitors (TKIs) either in monotherapy or in combination with immune checkpoint inhibitors (ICIs).

AREAS COVERED

Major attention was given to target therapies in the last couple of years, especially in those currently under phase II trials. Priority was given either to combinations of novel ICI and TKIs or those targeting alternative mutations of major carcinogenic pathways.

EXPERT OPINION

As TKIs are playing a more crucial role in HCC therapeutic strategies, it is fundamental to further expand molecular testing and monitoring of acquired resistances. Despite the recent advancement in both laboratory and clinical studies, further research is necessary to face the discrepancy in clinical practice.

Glypican-3 deficiency in liver cancer upregulates MAPK/ERK pathway but decreases cell proliferation

Glypican-3 (GPC3) is overexpressed in hepatocellular carcinomas and hepatoblastomas and represents an important therapeutic target but the biologic importance of GPC3 in liver cancer is unclear. To date, there are limited data characterizing the biological implications of GPC3 knockout (KO) in liver cancers that intrinsically express this target. Here, we report on the development and characterization of GPC3-KO liver cancer cell lines and compare to them to parental lines. GPC3-KO variants were established in HepG2 and Hep3B liver cancer cell lines using a lentivirus-mediated CRISPR/Cas9 system. We assessed the effects of GPC3 deficiency on oncogenic properties in vitro and in murine xenograft models. Downstream cellular signaling pathway changes induced by GPC3 deficiency were examined by RNAseq and western blot. To confirm the usefulness of the models for GPC3-targeted drug development, we evaluated the target engagement of a GPC3-selective antibody, GC33, conjugated to the positron-emitting zirconium-89 (89Zr) in subcutaneous murine xenografts of wild type (WT) and KO liver cancer cell lines. Deletion of GPC3 significantly reduced liver cancer cell proliferation, migration, and invasion compared to the parental cell lines. Additionally, the tumor growth of GPC3-KO liver cancer xenografts was significantly slower compared with control xenografts. RNA sequencing analysis also showed GPC3-KO resulted in a reduction in the expression of genes associated with cell cycle regulation, invasion, and migration. Specifically, we observed the downregulation of components in the AKT/NFκB/WNT signaling pathways and of molecules related to cell cycle regulation with GPC3-KO. In contrast, pMAPK/ERK1/2 was upregulated, suggesting an adaptive compensatory response. KO lines demonstrated increased sensitivity to ERK (GDC09994), while AKT (MK2206) inhibition was more effective in WT lines. Using antibody-based positron emission tomography (immunoPET) imaging, we confirmed that 89Zr-GC33 accumulated exclusively in GPC3-expression xenografts but not in GPC3-KO xenografts with high tumor uptake and tumor-to-liver signal ratio. We show that GPC3-KO liver cancer cell lines exhibit decreased tumorigenicity and altered signaling pathways, including upregulated pMAPK/ERK1/2, compared to parental lines. Furthermore, we successfully distinguished between GPC3+ and GPC3- tumors using the GPC3-targeted immunoPET imaging agent, demonstrating the potential utility of these cell lines in facilitating GPC3-selective drug development.

A-to-I RNA co-editing predicts clinical outcomes and is associated with immune cells infiltration in hepatocellular carcinoma

Aberrant RNA editing has emerged as a pivotal factor in the pathogenesis of hepatocellular carcinoma (HCC), but the impact of RNA co-editing within HCC remains underexplored. We used a multi-step algorithm to construct an RNA co-editing network in HCC, and found that HCC-related RNA editings are predominantly centralized within the network. Furthermore, five pairs of risk RNA co-editing events were significantly correlated with the overall survival in HCC. Based on presence of risk RNA co-editings resulted in the categorization of HCC patients into high-risk and low-risk groups. Disparities in immune cell infiltrations were observed between the two groups, with the high-risk group exhibiting a greater abundance of exhausted T cells. Additionally, seven genes associated with risk RNA co-editing pairs were identified, whose expression effectively differentiates HCC tumor samples from normal ones. Our research offers an innovative perspective on the etiology and potential therapeutics for HCC.

ImmunoPET/CT imaging of clear cell renal cell carcinoma with [18F]RCCB6: a first-in-human study

PURPOSE

The cluster of differentiation (CD70) is a potential biomarker of clear cell renal cell carcinoma (ccRCC). This study aims to develop CD70-targeted immuno-positron emission tomography/computed tomography (immunoPET/CT) imaging tracers and explore the diagnostic value in preclinical studies and the potential value in detecting metastases in ccRCC patients.

METHODS

Four novel CD70-specific single-domain antibodies (sdAbs) were produced and labelled with 18F by the aluminium fluoride restrained complexing agent (AlF-RESCA) method to develop radiotracers. The visualisation properties of the tracers were evaluated in a subcutaneous ccRCC patient-derived xenograft (PDX) model. In a registered prospective clinical trial (NCT06148220), six patients with pathologically confirmed RCC were included and underwent immunoPET/CT examination exploiting one of the developed tracers (i.e., [18F]RCCB6).

RESULTS

We engineered four sdAbs (His-tagged RCCB3 and RCCB6, His-tag-free RB3 and RB6) specifically targeting recombinant human CD70 without cross-reactivity to murine CD70. ImmunoPET/CT imaging with [18F]RCCB3 and [18F]RCCB6 demonstrated a high tumour-to-background ratio in a subcutaneous ccRCC PDX model, with the latter showing better diagnostic potential supported by higher tumour uptake and lower bone accumulation. In comparison, [18F]RB6, developed by sequence optimisation, has significantly lower kidney accumulation than that of [18F]RCCB6. In a pilot translational study, [18F]RCCB6 immunoPET/CT displayed ccRCC metastases in multiple patients and demonstrated improved imaging contrast and diagnostic value than 18F-FDG PET/CT in a patient with ccRCC.

CONCLUSION

The work successfully developed a series of CD70-targeted immunoPET/CT imaging tracers. Of them, [18F]RCCB6 clearly and specifically identified inoculated ccRCCs in preclinical studies. Clinical translation of [18F]RCCB6 suggests potential for identifying recurrence and/or metastasis in ccRCC patients.

Pilot study of humanized glypican-3-targeted zirconium-89 immuno-positron emission tomography for hepatocellular carcinoma

Purpose

Glypican-3 (GPC3)-targeted radioisotope immuno-positron emission tomography (immunoPET) may lead to earlier and more accurate diagnosis of hepatocellular carcinoma (HCC), thus facilitating curative treatment, decreasing early recurrence, and enhancing patient survival. We previously demonstrated reliable HCC detection using a zirconium-89-labeled murine anti-GPC3 antibody (89Zr-αGPC3M) for immunoPET. This study evaluated the efficacy of the humanized antibody successor (αGPC3H) to further clinical translation of a GPC3-based theranostic for HCC.

Methods

In vitro αGPC3 binding to HepG2 cells was assessed by flow cytometry. In vivo 89Zr-αGPC3H and 89Zr-αGPC3M tumor uptake was evaluated by PET/CT and biodistribution studies in an orthotopic xenograft mouse model of HCC.

Results

αGPC3H maintained binding to GPC3 in vitro and 89Zr-αGPC3H immunoPET identified liver tumors in vivo. PET/CT and biodistribution analyses demonstrated high 89Zr-αGPC3H tumor uptake and tumor-to-liver ratios, with no difference between groups.

Conclusion

Humanized αGPC3 successfully targeted GPC3 in vitro and in vivo. 89Zr-αGPC3H immunoPET had comparable tumor detection to 89Zr-αGPC3M, with highly specific tumor uptake, making it a promising strategy to improve HCC detection.

Synthesis and preclinical evaluation of a novel probe [18F]AlF-NOTA-IPB-GPC3P for PET imaging of GPC3 positive tumor

Glypican-3 (GPC3) is markedly overexpressed in hepatocellular carcinoma (HCC) and not expressed in normal liver tissues. In this study, a novel peptide PET imaging agent ([18F]AlF-NOTA-IPB-GPC3P) was developed to target GPC3 expressed in tumors. The overall radiochemical yield of [18F]AlF-NOTA-IPB-GPC3P was 10-15 %, and its lipophilicity, expressed as the logD value at a pH of 7.4, was -1.18 ± 0.06 (n = 3). Compared to the previously reported tracer [18F]AlF-GP2633, [18F]AlF-NOTA-IPB-GPC3P exhibited higher cellular uptake (15.13 vs 5.96) and internalized rate (80.63 % vs 35.93 %) in Huh7 cells at 120 min. Micro-PET/CT and biodistribution studies further demonstrated that [18F]AlF-NOTA-IPB-GPC3P exhibited significantly increased tumor uptake and prolonged tumor residence in Huh7 tumors compared to [18F]AlF-GP2633 (4.66 ± 0.22 % ID/g vs 0.72 ± 0.09 % ID/g at 60 min, p < 0.001; 5.05 ± 0.23 % ID/g vs 0.35 ± 0.08 % ID/g at 120 min, p < 0.001, respectively). Furthermore, the tumor-to-organ ratios of [18F]AlF-NOTA-IPB-GPC3P surpassed those of [18F]AlF-GP2633. Our results support the utilization of [18F]AlF-NOTA-IPB-GPC3P as a PET imaging agent targeting the GPC3 receptor for tumor detection.

Recent Advances in Radiotracers Targeting Novel Cancer-Specific Biomarkers in China: A Brief Overview

Radiopharmaceuticals play a critical role in nuclear medicine, providing novel tools for specifically delivering radioisotopes for the diagnosis and treatment of cancers. As the starting point for developing radiopharmaceuticals, cancer-specific biomarkers are important and receive worldwide attention. This field in China is currently experiencing a rapid expansion, with multiple radiotracers targeting novel targets being developed and translated into clinical studies. This review provides a brief overview of the exploration of novel imaging targets, preclinical evaluation of their targeting ligands, and translational research in China from 2020 to 2023, for detecting cancer, guiding targeted therapy, and visualizing the immune microenvironment. We believe that China will play an even more important role in the development of nuclear medicine in the world in the future.

ImmunoPET imaging of Trop2 in patients with solid tumours

Accurately predicting and selecting patients who can benefit from targeted or immunotherapy is crucial for precision therapy. Trophoblast cell surface antigen 2 (Trop2) has been extensively investigated as a pan-cancer biomarker expressed in various tumours and plays a crucial role in tumorigenesis through multiple signalling pathways. Our laboratory successfully developed two 68Ga-labelled nanobody tracers that can rapidly and specifically target Trop2. Of the two tracers, [68Ga]Ga-NOTA-T4, demonstrated excellent pharmacokinetics in preclinical mouse models and a beagle dog. Moreover, [68Ga]Ga-NOTA-T4 immuno-positron emission tomography (immunoPET) allowed noninvasive visualisation of Trop2 heterogeneous and differential expression in preclinical solid tumour models and ten patients with solid tumours. [68Ga]Ga-NOTA-T4 immunoPET could facilitate clinical decision-making through patient stratification and response monitoring during Trop2-targeted therapies.

Preclinical development of novel PD-L1 tracers and first-in-human study of [68Ga]Ga-NOTA-RW102 in patients with lung cancers

BACKGROUND

The programmed cell death protein-1 (PD-1)/programmed death receptor ligand 1 (PD-L1) axis critically facilitates cancer cells' immune evasion. Antibody therapeutics targeting the PD-1/PD-L1 axis have shown remarkable efficacy in various tumors. Immuno-positron emission tomography (ImmunoPET) imaging of PD-L1 expression may help reshape solid tumors' immunotherapy landscape.

METHODS

By immunizing an alpaca with recombinant human PD-L1, three clones of the variable domain of the heavy chain of heavy-chain only antibody (VHH) were screened, and RW102 with high binding affinity was selected for further studies. ABDRW102, a VHH derivative, was further engineered by fusing RW102 with the albumin binder ABD035. Based on the two targeting vectors, four PD-L1-specific tracers ([68Ga]Ga-NOTA-RW102, [68Ga]Ga-NOTA-ABDRW102, [64Cu]Cu-NOTA-ABDRW102, and [89Zr]Zr-DFO-ABDRW102) with different circulation times were developed. The diagnostic efficacies were thoroughly evaluated in preclinical solid tumor models, followed by a first-in-human translational investigation of [68Ga]Ga-NOTA-RW102 in patients with non-small cell lung cancer (NSCLC).

RESULTS

While RW102 has a high binding affinity to PD-L1 with an excellent KD value of 15.29 pM, ABDRW102 simultaneously binds to human PD-L1 and human serum albumin with an excellent KD value of 3.71 pM and 3.38 pM, respectively. Radiotracers derived from RW102 and ABDRW102 have different in vivo circulation times. In preclinical studies, [68Ga]Ga-NOTA-RW102 immunoPET imaging allowed same-day annotation of differential PD-L1 expression with specificity, while [64Cu]Cu-NOTA-ABDRW102 and [89Zr]Zr-DFO-ABDRW102 enabled longitudinal visualization of PD-L1. More importantly, a pilot clinical trial shows the safety and diagnostic value of [68Ga]Ga-NOTA-RW102 immunoPET imaging in patients with NSCLCs and its potential to predict immune-related adverse effects following PD-L1-targeted immunotherapies.

CONCLUSIONS

We developed and validated a series of PD-L1-targeted tracers. Initial preclinical and clinical evidence indicates that immunoPET imaging with [68Ga]Ga-NOTA-RW102 holds promise in visualizing differential PD-L1 expression, selecting patients for PD-L1-targeted immunotherapies, and monitoring immune-related adverse effects in patients receiving PD-L1-targeted treatments.

TRIAL REGISTRATION NUMBER

NCT06165874.

GenX caused liver injury and potential hepatocellular carcinoma of mice via drinking water even at environmental concentration

Hexafluoropropylene oxide dimer acid (GenX) is an alternative to perfluorooctanoic acid (PFOA), whose environmental concentration is close to its maximum allowable value established by the US Environmental Protection Agency, so its effects on human health are of great concern. The liver is one of the most crucial target organ for GenX, but whether GenX exposure induces liver cancer still unclear. In this research project, male C57 mice were disposed to GenX in drinking water at environmental concentrations (0.1 and 10 μg/L) and higher concentrations (1 and 100 mg/L) for 14 weeks to explore its effects on liver injury and potential carcinogenicity in mice. GenX was found to cause a dose-dependent increase in the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC), and triglyceride (TG). As the content of GenX in drinking water increased, so did the concentrations of Glypican-3 (GPC-3) and detachment gamma-carboxyprothrombin (DCP), indicators of early hepatocellular cancer. GenX destroyed the boundaries and arrangements of hepatocytes, in which monocyte infiltration, balloon-like transformation, and obvious lipid vacuoles were observed between cells. Following exposure to GenX, Masson sections revealed a significant quantity of collagen deposition in the liver. Alpha-feto protein (AFP), vascular endothelial growth factor (VEGF), Ki67, matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9) gene expression increased in a dose-dependent manner in the treatment group relative to the control group. In general, drinking water GenX exposure induced liver function impairment, elevated blood lipid level, caused liver pathological structure damage and liver fibrosis lesions, changed the liver inflammatory microenvironment, and increased the concentration of liver-related tumor indicator even in the environmental concentration, suggesting GenX is a potential carcinogen.

FGF19-Based Mini Probe Targeting FGFR4 for Diagnosis and Surgical Navigation of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a frequent malignancy that has a high death rate and a high rate of recurrence following surgery, owing to insufficient surgical resection. Furthermore, HCC is prone to peritoneal metastasis (HCC-PM), resulting in a significant number of tiny cancer lesions, making surgical removal more challenging. As a potential imaging target, FGFR4 is highly expressed in tumors, especially in HCC, but is less expressed in the normal liver. In this study, we used computational simulation approaches to develop peptide I0 derived from FGF19, a particular ligand of FGFR4, and labeled it with the NIRF dye, MPA, for HCC detection. In surgical navigation, the TBR was 9.31 ± 1.36 and 8.57 ± 1.15 in HepG2 in situ tumor and HCC-PM models, respectively, indicating considerable tumor uptake. As a result, peptide I0 is an excellent clinical diagnostic reagent for HCC, as well as a tool for surgically resecting HCC peritoneal metastases.

The role and mechanism of HIF-1α-mediated glypican-3 secretion in hypoxia-induced tumor progression in hepatocellular carcinoma

OBJECTIVE

To explore the expression and secretion mechanism of glypican-3 (GPC3) in hepatocellular carcinoma (HCC) cells under hypoxic conditions, and its role in tumor progression.

METHODS

Huh7 cells with and without the knockdown of hypoxia-inducible factor 1-alpha (HIF-1α) were cultured under 1% O2 for varying durations to induce hypoxia. The expression levels of GPC3, HSP70, CD63, STX11 and SYT7 in the cytoplasm and exosomes of Huh7 cells were evaluated by western blotting and immunofluorescence. GPC3 protein expression was further measured in cells treated with GW4869 under hypoxic conditions. Huh7 cells and human umbilical vein endothelial cells (HUVECs) were cultured with the exosomes extracted from the control and GPC3-knockdown cells, the cell proliferation, migration, epithelial-mesenchymal transition (EMT), invasion, and in vitro angiogenesis were analyzed. Tumor xenografts were established to assess the role of GPC3-deficient exosomes in tumor growth.

RESULTS

Hypoxic culture conditions downregulated GPC3, STX11 and SYT7 protein levels in the Huh7 cells and upregulated GPC3 mRNA, and also increased GPC3 protein expression in the exosomes. HIF-1α knockdown, as well as treatment with GW4869, upregulated GPC3 protein in the Huh7 cells grown under 1% O2, but downregulated exosomal GPC3. Furthermore, exosomes derived from the GPC3-knockdown cells inhibited the proliferation and migration of Huh7 cells, decreased the expression of N-cadherin, vimentin, β-catenin, c-Myc and cyclin D1, and increased that of E-cadherin. Likewise, the GPC3-deficient exosomes also suppressed the invasion and tube formation ability of the HUVECs compared to that of control cells. Consistent with the in vitro results, the GPC3-deficient exosomes also repressed tumor growth in vivo.

CONCLUSION

Hypoxia promoted secretion of exosomal GPC3 through the activation of HIF-1α. GPC3-deficient exosomes inhibited the proliferation, migration and EMT of HCC cells via the Wnt/β-catenin signaling pathway, and suppressed the angiogenic potential of HUVECs. This provided a novel understanding of the role of exosomal GPC3 in HCC progression.

Promising Diagnostic and Therapeutic Approaches Based on VHHs for Cancer Management

The discovery of the distinctive structure of heavy chain-only antibodies in species belonging to the Camelidae family has elicited significant interest in their variable antigen binding domain (VHH) and gained attention for various applications, such as cancer diagnosis and treatment. This article presents an overview of the characteristics, advantages, and disadvantages of VHHs as compared to conventional antibodies, and their usage in diverse applications. The singular properties of VHHs are explained, and several strategies that can augment their utility are outlined. The preclinical studies illustrating the diagnostic and therapeutic efficacy of distinct VHHs in diverse formats against solid cancers are summarized, and an overview of the clinical trials assessing VHH-based agents in oncology is provided. These investigations demonstrate the enormous potential of VHHs for medical research and healthcare.

Current methods for the detection of glypican-3

Glypican-3 (GPC3) is a heparan sulfate proteoglycan (HSPG) that binds to the cell membrane via glycosylphosphatidylinositol (GPI), widely expressed in human embryos, and is undetectable in healthy adult liver but overexpressed in human hepatocellular carcinoma (HCC). Therefore, accurate and sensitive detection of GPC3 is critical for disease diagnosis. In recent years, a series of methods have been developed for the highly sensitive detection of GPC3, but there is a lack of reviews on recent advances in GPC3-related assays. In this review, we provide the recent advances in GPC3 detection and GPC3 concentration detection, mainly in terms of various optical sensor-based assays and electrochemical assays, and also provide new insights into the challenges and future directions of the field.

ImmunoPET imaging of Trop2 expression in solid tumors with nanobody tracers

PURPOSE

The high expression of the transmembrane glycoprotein trophoblast cell-surface antigen 2 (Trop2) was strongly associated with the progression of solid tumors, including pancreatic and gastric cancers. Our study aimed to construct Trop2-specific immuno-positron emission tomography (immunoPET) probes and assess the diagnostic abilities in preclinical pancreatic and gastric cancer models.

METHODS

The expression of Trop2 in pancreatic cancer was determined by single-cell sequencing and immunohistochemistry on tissue microarray (TMA). Flow cytometry was used to screen the expression of Trop2 in pancreatic cancer cell lines. Two nanobodies (i.e., RTD98 and RTD01) targeting Trop2 were developed and labeled with gallium-68 (68Ga, T1/2 = 1.1 h) to construct immunoPET imaging probes. The agents were researched in cell-derived pancreatic and patient-derived gastric cancer models expressing varying Trop2.

RESULTS

Single-cell sequencing results showed high expression of Trop2 in pancreatic ductal cells as well as acinar cells and immunohistochemical staining of TMA from pancreatic cancers showed significantly higher expression of Trop2 in cancerous than in paracancerous tissues. ImmunoPET utilizing [68Ga]Ga-NOTA-RTD98 could clearly delineate subcutaneous tumors, both in cell-derived pancreatic cancer models and patient-derived gastric cancer models, superior to imaging using [18F]-FDG or a non-specific probe [68Ga]Ga-NOTA-RTD161. Another probe with improved pharmacokinetics targeting Trop2, [68Ga]Ga-NOTA-RTD01, was further prepared and showed advantageous diagnostic capabilities in preclinical pancreatic cancer models.

CONCLUSION

In the work, we reported two nanobody tracers targeting human Trop2 which may facilitate better use of Trop2-targeted therapeutics by noninvasively displaying expression dynamics of the target.

Construction of GPC3-modified Lipopolymer SiRNA Delivery System

BACKGROUND

Gene therapy has been widely concerned because of its unique therapeutic mechanism. However, due to the lack of safe and effective carries, it has not been widely used in clinical practice. Glypican 3 (GPC3) is a highly specific proteoglycan for hepatocellular carcinoma and is a potential diagnostic and therapeutic target for hepatocellular carcinoma. Herein, to monitor the effect of gene therapy and enhance the transfection efficiency of gene carriers, GPC3-modified lipid polyethyleneimine-modified superparamagnetic nanoparticle (GLPS), a type of visualized carrier for siRNA (small-interfering RNA) targeting the liver, was prepared.

METHODS

We performed in vitro gene silencing, cytotoxicity, and agarose gel electrophoresis to identify the optimal GLPS formulation. In vitro MRI and Prussian blue staining verified the liver-targeting function of GLPS. We also analyzed the biocompatibility of GLPS by co-culturing with rabbit red blood cells. Morphological changes were evaluated using HE staining.

RESULTS

The GLPS optimal formulation consisted of LPS and siRNA at a mass ratio of 25:1 and LPS and DSPE-PEG-GPC3 at a molar ratio of 2:3. GLPS exhibited evident liver-targeting function. In vitro, we did not observe morphological changes in red blood cells or hemolysis after co-culture. In vivo, routine blood analysis revealed no abnormalities after GLPS injection. Moreover, the tissue morphology of the kidney, spleen, and liver was normal without injury or inflammation.

CONCLUSION

GLPS could potentially serve as an effective carrier for liver-targeted MRI monitoring and siRNA delivery.

Site-Specific Modification of Single Domain Antibodies by Enzyme-Immobilized Magnetic Beads

Nanobodies as imaging agents and drug conjugates have shown great potential for cancer diagnostics and therapeutics. However, site-specific modification of a nanobody with microbial transglutaminase (mTGase) encounters problems in protein separation and purification. Here, we describe a facile yet reliable strategy of immobilizing mTGase onto magnetic beads for site-specific nanobody modification. The mTGase immobilized on magnetic beads (MB-mTGase) exhibits catalytic activity nearly equivalent to that of the free mTGase, with good reusability and universality. Magnetic separation simplifies the protein purification step and reduces the loss of nanobody bioconjugates more effectively than size exclusion chromatography. Using MB-mTGase, we demonstrate site-specific conjugation of nanobodies with fluorescent dyes and polyethylene glycol molecules, enabling targeted immunofluorescence imaging and improved circulation dynamics and tumor accumulation in vivo. The combined advantages of MB-mTGase method, including high conjugation efficiency, quick purification, less protein loss, and recycling use, are promising for site-specific nanobody functionalization and biomedical applications.

ImmunoPET Imaging of CD47 with VHH-Derived Tracers in Pancreatic Cancers

Pancreatic ductal adenocarcinoma (PDAC) is a malignant tumor with insidious onset, rapid progression, and a very poor prognosis. CD47 is a transmembrane protein associated with the development and poor prognosis of pancreatic cancer. The aim of this study was to evaluate the diagnostic value of novel immunoPET tracers targeting CD47 in preclinical pancreatic cancer models. The association of CD47 expression with pancreatic cancer was analyzed using the Gene Expression Profiling Interactive Analysis platform. Immunohistochemical analysis of tissue microarrays was performed to detect CD47 expression in PDAC. CD47 expression levels on BxPC-3 and AsPC-1 cell membranes were compared using flow cytometry. A VHH (C2)-targeting human CD47 and its albumin-binding derivative (ABDC2) were labeled with 68Ga or 89Zr, respectively. The developed tracers were evaluated by immuno-positron emission tomography (immunoPET) imaging in tumor-bearing nude and CD47-humanized mice. [68Ga]Ga-NOTA-C2 effectively detected tumor lesions in nude mice models and further showed confirmative imaging capacity in CD47-humanized PDAC models. Compared with [68Ga]Ga-NOTA-C2, [89Zr]Zr-DFO-ABDC2 had a significantly prolonged circulation time, increased tumor uptake, and reduced accumulation in the kidneys. Finally, biodistribution and histological staining confirmed the results of the immunoPET imaging studies. In this study, we validated that two novel VHH-derived molecular imaging tracers for immunoPET imaging ([68Ga]Ga-NOTA-C2 and [89Zr]Zr-DFO-ABDC2) can effectively annotate CD47 expression and diagnose PDAC in a target-specific manner. Clinical application of the imaging strategies may help select patients for CD47-targeted therapies and assess the response thereafter.

Site-Specifically Conjugated Single-Domain Antibody Successfully Identifies Glypican-3-Expressing Liver Cancer by Immuno-PET

Primary liver cancer is the third leading cause of cancer-related deaths, and its incidence and mortality are increasing worldwide. Hepatocellular carcinoma (HCC) accounts for 80% of primary liver cancer cases. Glypican-3 (GPC3) is a heparan sulfate proteoglycan that histopathologically defines HCC and represents an attractive tumor-selective marker for radiopharmaceutical imaging and therapy for this disease. Single-domain antibodies are a promising scaffold for imaging because of their favorable pharmacokinetic properties, good tumor penetration, and renal clearance. Although conventional lysine-directed bioconjugation can be used to yield conjugates for radiolabeling full-length antibodies, this stochastic approach risks negatively affecting target binding of the smaller single-domain antibodies. To address this challenge, site-specific approaches have been explored. Here, we used conventional and sortase-based site-specific conjugation methods to engineer GPC3-specific human single-domain antibody (HN3) PET probes. Methods: Bifunctional deferoxamine (DFO) isothiocyanate was used to synthesize native HN3 (nHN3)-DFO. Site-specifically modified HN3 (ssHN3)-DFO was engineered using sortase-mediated conjugation of triglycine-DFO chelator and HN3 containing an LPETG C-terminal tag. Both conjugates were radiolabeled with 89Zr, and their binding affinity in vitro and target engagement of GPC3-positive (GPC3+) tumors in vivo were determined. Results: Both 89Zr-ssHN3 and 89Zr-nHN3 displayed nanomolar affinity for GPC3 in vitro. Biodistribution and PET/CT image analysis in mice bearing isogenic A431 and A431-GPC3+ xenografts, as well as in HepG2 liver cancer xenografts, showed that both conjugates specifically identify GPC3+ tumors. 89Zr-ssHN3 exhibited more favorable biodistribution and pharmacokinetic properties, including higher tumor uptake and lower liver accumulation. Comparative PET/CT studies on mice imaged with both 18F-FDG and 89Zr-ssHN3 showed more consistent tumor accumulation for the single-domain antibody conjugate, further establishing its potential for PET imaging. Conclusion: 89Zr-ssHN3 showed clear advantages in tumor uptake and tumor-to-liver signal ratio over the conventionally modified 89Zr-nHN3 in xenograft models. Our results establish the potential of HN3-based single-domain antibody probes for GPC3-directed PET imaging of liver cancers.

Glypican-3 (GPC-3) Structural Analysis and Cargo in Serum Small Extracellular Vesicles of Hepatocellular Carcinoma Patients

Glypican-3 (GPC-3) is a heparin sulfate proteoglycan located extracellularly and anchored to the cell membrane of transformed hepatocytes. GPC-3 is not expressed in normal or cirrhotic liver tissue but is overexpressed in hepatocellular carcinoma (HCC). Because of this, GPC-3 is one of the most important emerging immunotargets for treatment and as an early detection marker of HCC. To determine if GPC-3 domains associated with serum small extracellular vesicles (sEVs) could be used as an HCC diagnostic marker, we predicted in silico GPC-3 structural properties and tested for the presence of its full-length form and/or cleaved domains in serum sEVs isolated from patients with HCC. Structural analysis revealed that the Furin cleavage site of GPC-3 is exposed and readily accessible, suggesting the facilitation of GPC-3 cleavage events. Upon isolation of sEVs from both hepatocytes, culture media and serum of patients with HCC were studied for GPC-3 content. This data suggests that Furin-dependent GPC-3 cleaved domains could be a powerful tool for detection of initial stages of HCC and serve as a predictor for disease prognosis.

A nomogram based on LI-RADS features, clinical indicators and quantitative contrast-enhanced MRI parameters for predicting glypican-3 expression in hepatocellular carcinoma

Purpose

Noninvasively assessing the tumor biology and microenvironment before treatment is greatly important, and glypican-3 (GPC-3) is a new-generation immunotherapy target for hepatocellular carcinoma (HCC). This study investigated the application value of a nomogram based on LI-RADS features, quantitative contrast-enhanced MRI parameters and clinical indicators in the noninvasive preoperative prediction of GPC-3 expression in HCC.

Methods and materials

We retrospectively reviewed 127 patients with pathologically confirmed solitary HCC who underwent Gd-EOB-DTPA MRI examinations and related laboratory tests. Quantitative contrast-enhanced MRI parameters and clinical indicators were collected by an abdominal radiologist, and LI-RADS features were independently assessed and recorded by three trained intermediate- and senior-level radiologists. The pathological and immunohistochemical results of HCC were determined by two senior pathologists. All patients were divided into a training cohort (88 cases) and validation cohort (39 cases). Univariate analysis and multivariate logistic regression were performed to identify independent predictors of GPC-3 expression in HCC, and a nomogram model was established in the training cohort. The performance of the nomogram was assessed by the area under the receiver operating characteristic curve (AUC) and the calibration curve in the training cohort and validation cohort, respectively.

Results

Blood products in mass, nodule-in-nodule architecture, mosaic architecture, contrast enhancement ratio (CER), transition phase lesion-liver parenchyma signal ratio (TP-LNR), and serum ferritin (Fer) were independent predictors of GPC-3 expression, with odds ratios (ORs) of 5.437, 10.682, 5.477, 11.788, 0.028, and 1.005, respectively. Nomogram based on LI-RADS features (blood products in mass, nodule-in-nodule architecture and mosaic architecture), quantitative contrast-enhanced MRI parameters (CER and TP-LNR) and clinical indicators (Fer) for predicting GPC-3 expression in HCC was established successfully. The nomogram showed good discrimination (AUC of 0.925 in the training cohort and 0.908 in the validation cohort) and favorable calibration. The diagnostic sensitivity and specificity were 76.9% and 92.3% in the training cohort, 76.8% and 93.8% in the validation cohort respectively.

Conclusion

The nomogram constructed from LI-RADS features, quantitative contrast-enhanced MRI parameters and clinical indicators has high application value, can accurately predict GPC-3 expression in HCC and may help noninvasively identify potential patients for GPC-3 immunotherapy.

Development and Characterization of Nanobody-Derived CD47 Theranostic Pairs in Solid Tumors

Overexpression of CD47 is frequently observed in various types of human malignancies, inhibiting myeloid-mediated elimination of tumor cells and affecting the prognosis of cancer patients. By mapping biomarker expression, immuno-positron emission tomography has been increasingly used for patient screening and response monitoring. By immunization alpacas with recombinant human CD47, we prepared a CD47-targeting nanobody C2 and developed [⁶⁸Ga]Ga-NOTA-C2, followed by an exploration of the diagnostic value in CD47-expressing tumor models including gastric-cancer patient-derived xenograft models. By fusing C2 to an albumin binding domain (ABD), we synthesized ABDC2, which had increased in vivo half-life and improved targeting properties. We further labeled ABDC2 with ⁶⁸Ga/⁸⁹Zr/¹⁷⁷Lu to develop radionuclide theranostic pairs and evaluated the pharmacokinetics and theranostic efficacies of the agents in cell- and patient-derived models. Both C2 and ABDC2 specifically reacted with human CD47 with a high K _D value of 23.50 and 84.57 pM, respectively. [⁶⁸Ga]Ga-NOTA-C2 was developed with high radiochemical purity (99 >%, n = 4) and visualized CD47 expression in the tumors. In comparison to the rapid renal clearance and short half-life of [⁶⁸Ga]Ga-NOTA-C2, both [⁶⁸Ga]Ga-NOTA-ABDC2 and [⁸⁹Zr]Zr-DFO-ABDC2 showed prolonged circulation and increased tumor uptake, with the highest uptake of [⁸⁹Zr]Zr-DFO-ABDC2 occurring at 72 h post-injection. Moreover, [¹⁷⁷Lu]Lu-DOTA-ABDC2 radioimmunotherapy suppressed the tumor growth but was associated with toxicity, warranting further optimization of the treatment schedules. Taken together, we reported a series of nanobody-derived CD47-targeted agents, of which [⁶⁸Ga]Ga-NOTA-C2 and [⁸⁹Zr]Zr-DFO-ABDC2 are readily translatable. Optimization and translation of CD47-targeted theranostic pair may provide new prospects for CD47-targeted management of solid tumors.

PET imaging of hepatocellular carcinoma by targeting tumor-associated endothelium using [68Ga]Ga-PSMA-617

OBJECTIVE

Hepatocellular carcinoma (HCC) is a malignant tumor associated with high morbidity and mortality rates. In many non-prostate solid tumors such as HCC, prostate-specific membrane antigens (PSMA) are overexpressed in tumor-associated endothelial cells. Therefore, the aim of this study was to evaluate the performance of [68Ga]Ga-PSMA-617 PET imaging on HCC with different animal models, including cell line-derived xenografts (CDX) and patient-derived xenografts (PDX), and to explore its mechanisms of function.

METHODS

[68Ga]Ga-PSMA-617 was prepared. The expression level of PSMA in two human hepatocellular cancer cells (HepG2 and HuH-7) was evaluated, and the cellular uptakes of [68Ga]Ga-PSMA-617 were assayed. HepG2 and HuH-7 subcutaneous xenograft models, HepG2 orthotopic xenograft models, and four different groups of PDX models were prepared. Preclinical pharmacokinetics and performance of [68Ga]Ga-PSMA-617 were evaluated in different types of HCC xenografts models using small animal PET and biodistribution studies.

RESULTS

Low PSMA expression level of HepG2 and HuH-7 cells was observed, and the cellular uptake and blocking study confirmed the non-specificity of the PSMA-targeted probe binding to HepG2 and HuH-7 cells. In the subcutaneous xenograft models, the tumor uptakes at 0.5 h were 0.76 ± 0.12%ID/g (HepG2 tumors) and 0.78 ± 0.08%ID/g (HuH-7 tumors), respectively, which were significantly higher than those of the blocking groups (0.23 ± 0.04%ID/g and 0.20 ± 0.04%ID/g, respectively). In the orthotopic xenograft models, PET images clearly displayed the tumor locations based on the preferential accumulation of [68Ga]Ga-PSMA-617 in tumor tissue versus normal liver tissue, suggesting the possibility of using [68Ga]Ga-PSMA-617 PET imaging to detect primary HCC lesions in deep tissue. In the four different groups of HCC PDX models, PET imaging with [68Ga]Ga-PSMA-617 provided clear tumor uptakes with prominent tumor-to-background contrast, further demonstrating its potential for the clinical imaging of PSMA-positive HCC lesions. The staining of tumor tissue sections with CD31- and PSMA-specific antibodies visualized the tumor-associated blood vessels and PSMA expression on endothelial cells in subcutaneous, orthotopic tissues, and PDX tissues, confirming the imaging with [68Ga]Ga-PSMA-617 might be mediated by targeting tumor associated endothelium.

CONCLUSION

In this study, in vivo PET on different types of HCC xenograft models illustrated high uptake within tumors, which confirmed that [68Ga]Ga-PSMA-617 PET may be a promising imaging modality for HCC by targeting tumor associated endothelium.

Novel Nanotechnology Approaches to Overcome Drug Resistance in the Treatment of Hepatocellular Carcinoma: Glypican 3 as a Useful Target for Innovative Therapies

Hepatocellular carcinoma (HCC) is the second most lethal tumor, with a 5-year survival rate of 18%. Early stage HCC is potentially treatable by therapies with curative intent, whereas chemoembolization/radioembolization and systemic therapies are the only therapeutic options for intermediate or advanced HCC. Drug resistance is a critical obstacle in the treatment of HCC that could be overcome by the use of targeted nanoparticle-based therapies directed towards specific tumor-associated antigens (TAAs) to improve drug delivery. Glypican 3 (GPC3) is a member of the glypican family, heparan sulfate proteoglycans bound to the cell surface via a glycosylphosphatidylinositol anchor. The high levels of GPC3 detected in HCC and the absence or very low levels in normal and non-malignant liver make GPC3 a promising TAA candidate for targeted nanoparticle-based therapies. The use of nanoparticles conjugated with anti-GPC3 agents may improve drug delivery, leading to a reduction in severe side effects caused by chemotherapy and increased drug release at the tumor site. In this review, we describe the main clinical features of HCC and the common treatment approaches. We propose the proteoglycan GPC3 as a useful TAA for targeted therapies. Finally, we describe nanotechnology approaches for anti-GPC3 drug delivery systems based on NPs for HCC treatment.

IgG-Binding Nanobody Capable of Prolonging Nanobody-Based Radiotracer Plasma Half-Life and Enhancing the Efficacy of Tumor-Targeted Radionuclide Therapy

Nanobodies have been developed rapidly as targeted probes for molecular imaging owing to their high affinity, outstanding tissue penetration, and rapid blood clearance. However, the short retention time at the tumor site limits their application in targeted radionuclide therapy. In this study, we designed a dual-targeting nanobody referred to as MIRC213-709, which can specifically bind to the HER2 receptor in tumor cell lines with high affinity (by nanobody MIRC213) and endogenous IgG in plasma to prolong the half-life by the MIRC213 C-terminal fusion nanobody, MIRC709. The nanobodies were site-specifically radiolabeled with ^99mTc and ¹⁷⁷Lu, and radiochemical purity was >95% after purification. The long blood circulation time and tumor retention property of ^99mTc/¹⁷⁷Lu-MIRC213-709 were confirmed by a blood clearance assay, single-photon emission computed tomography (SPECT), and a biodistribution study. The blood clearance assay showed that the distribution phase half-life (T_1/2α) and elimination phase half-life (T_1/2β) of ^99mTc-MIRC213-709 were 6.74- and 19.04-fold longer than those of ^99mTc-MIRC213, respectively. The SPECT/CT and biodistribution results showed that the highest uptake of ¹⁷⁷Lu-MIRC213 in the NCI-N87 model was 5.24 ± 0.95% ID/g at 6 h p.i., while the highest uptake of ¹⁷⁷Lu-MIRC213-709 in the NCI-N87 model was 30.82 ± 7.29% ID/g at 48 h p.i. Compared with ¹⁷⁷Lu-MIRC213, ¹⁷⁷Lu-MIRC213-709 had a 16.9-fold increased tumor cumulative uptake (2606 ± 195.1 vs 153.9 ± 22.37% ID/g·h). The targeted radionuclide therapy assay was performed in the NCI-N87 tumor model, and treatment monitoring ended on day 32. The post-treatment/pretreatment tumor volumes were 12.99 ± 1.66, 3.58 ± 0.96, 1.26 ± 0.17, and 1.54 ± 0.50 in the 0, 9, and 18 MBq single-dose groups and the two 9 MBq divided dose group (14 days apart), respectively. All treatment groups showed significant therapeutic effects (P < 0.0001). Thus, fusion with the IgG-binding nanobody MIRC709 provides MIRC213 derivatives with improved metabolic properties for targeted radionuclide therapy.