A Humanized Anti-GPC3 Antibody for Immuno-Positron Emission Tomography Imaging of Orthotopic Mouse Model of Patient-Derived Hepatocellular Carcinoma Xenografts

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.

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.

Nucleic acid-triggered tumoral immunity propagates pH-selective therapeutic antibodies through tumor-driven epitope spreading

Important roles of humoral tumor immunity are often pointed out; however, precise profiles of dominant antigens and developmental mechanisms remain elusive. We systematically investigated the humoral antigens of dominant intratumor immunoglobulin clones found in human cancers. We found that approximately half of the corresponding antigens were restricted to strongly and densely negatively charged polymers, resulting in simultaneous reactivities of the antibodies to both densely sulfated glycosaminoglycans (dsGAGs) and nucleic acids (NAs). These anti-dsGAG/NA antibodies matured and expanded via intratumoral immunological driving force of innate immunity via NAs. These human cancer-derived antibodies exhibited acidic pH-selective affinity across both antigens and showed specific reactivity to diverse spectrums of human tumor cells. The antibody-drug conjugate exerted therapeutic effects against multiple cancers in vivo by targeting cell surface dsGAG antigens. This study reveals that intratumoral immunological reactions propagate tumor-oriented immunoglobulin clones and demonstrates a new therapeutic modality for the universal treatment of human malignancies.

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.

Imaging ligands targeting glypican-3 receptor expression in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer mortality. Early detection of HCC is important since potentially curative therapies exist in the initial stages of HCC; no curative therapies exist for late-stage HCC. However, the initial detection of HCC remains challenging due to the lack of symptoms during the early stage of the disease. Other methods of screening and detecting HCC, including blood serum tests and conventional imaging methods, remain inadequate due to genetic differences between patients and the high background activity of liver tissues. Thus, there is a need for an accurate imaging agent for the diagnosis, staging, and prognosis of HCC. Glypican-3 (GPC3) is an oncofetal receptor responsible for regulating cell division, growth, and survival. GPC3 is a clinically relevant biomarker for imaging and therapeutics, as its expression is HCC tumor-specific and absent from normal and other pathological liver tissues. The development of novel GPC3-targeting imaging agents has encompassed three classes of biomolecules: peptides, antibodies, and aptamers. These biomolecules serve as constructs for diagnostic imaging (demonstrating potential as positron emission tomography [PET], single-photon emission tomography [SPECT], and optical imaging agents) and HCC treatment delivery. More than 20 unique ligands have been identified in the literature as showing specificity for the GPC3 receptor. Although several ligands are currently under clinical investigation as therapies for HCC, clinical translation of GPC3-targeting ligands as imaging agents is lacking. This review highlights the current landscape of ligands targeting GPC3 and describes their promising possibilities as imaging agents for HCC.

ImmunoPET: Antibody-Based PET Imaging in Solid Tumors

Immuno-positron emission tomography (immunoPET) is a molecular imaging modality combining the high sensitivity of PET with the specific targeting ability of monoclonal antibodies. Various radioimmunotracers have been successfully developed to target a broad spectrum of molecules expressed by malignant cells or tumor microenvironments. Only a few are translated into clinical studies and barely into clinical practices. Some drawbacks include slow radioimmunotracer kinetics, high physiologic uptake in lymphoid organs, and heterogeneous activity in tumoral lesions. Measures are taken to overcome the disadvantages, and new tracers are being developed. In this review, we aim to mention the fundamental components of immunoPET imaging, explore the groundbreaking success achieved using this new technique, and review different radioimmunotracers employed in various solid tumors to elaborate on this relatively new imaging modality.

Peptide-Conjugated Aggregation-Induced Emission Fluorogenic Probe for Glypican-3 Protein Detection and Hepatocellular Carcinoma Cells Imaging

Hepatocellular carcinoma (HCC) is a malignant tumor with high morbidity and mortality on a global scale, and the development of accurate detection and imaging methods for HCC cells is urgently needed. Herein, by connecting peptide L5, which can specifically bind to the overexpressed Glypican-3 (GPC-3) protein of HCC cells with aggregation-induced emission (AIE) moiety ammonium cation-functionalized 9,10-distyrylanthracene (NDSA) via the “click” reaction, we synthesized a fluorescent probe NDSA-L5. In an aqueous solution, the probe shows weak emission, whereas, in the presence of the GPC-3 protein, bright fluorescence can be obtained since NDSA-L5 binds to the GPC-3 protein, leading to the restricted intramolecular movement of AIE-active NDSA-L5. The imaging and flow cytometry experiments demonstrate that the NDSA-L5 probe can rapidly accumulate in the subcutaneous HCC cells and liver tumor tissue and shows a potential application in early detection and surgical navigation for HCC cancer.

GPC3-targeted immunoPET imaging of hepatocellular carcinomas

PURPOSE

Early detection of hepatocellular carcinoma (HCC) remains a clinical challenge. Glypican 3 (GPC3) is a proteoglycan highly specific for HCC and is a potential diagnostic and therapeutic target for HCC. This work aims to develop GPC3-targeted immuno-positron emission tomography (immunoPET) imaging strategies and to assess the diagnostic values in preclinical HCC models.

METHODS

Flow cytometry was used to screen GPC3-positive HCC cell lines. The expression of GPC3 in HCCs was detected by immunohistochemistry on tissue microarray. A novel GPC3-specific single domain antibody (sdAb) was produced and labeled with gallium-68 (⁶⁸Ga, T_1/2 = 1.1 h) and fluorine-18 (¹⁸F, T_1/2 = 1.8 h) to develop radiotracers with different half-lives. The diagnostic efficacies of the developed probes (i.e., [⁶⁸Ga]Ga-NOTA-G2, [¹⁸F]F-G2, and [⁶⁸Ga]Ga-NOTA-ABDG2) were interrogated in preclinical HCC models bearing varying GPC3 levels.

RESULTS

GPC3 was strongly expressed on HCC cell lines and patients with poorly differentiated HCC. [⁶⁸Ga]Ga-NOTA-G2 immunoPET imaging specifically delineated the subcutaneous HCC lesions, outperforming the traditional ¹⁸F-fluorodeoxyglucose PET and the nonspecific [⁶⁸Ga]Ga-NOTA-NbGFP immunoPET. ImmunoPET imaging with [¹⁸F]F-G2 also efficiently diagnosed the tumors with clarity. Moreover, the fusion of G2 to an albumin-binding domain (ABD) significantly increased the tumor uptake and decreased kidney accumulation of the radiotracer when compared to [⁶⁸Ga]Ga-NOTA-G2.

CONCLUSIONS

In the work, we successfully developed sdAb-derived GPC3-targeted immunoPET imaging strategies and characterized the superior diagnostic accuracies in preclinical HCC models. Furthermore, we synthesized a fusion protein ABDG2 with improved targeting and pharmacokinetic properties, serving as a promising candidate for developing radioimmunotherapy agents.