Imaging the expression of glypican-3 in hepatocellular carcinoma by PET

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.

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.

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.

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.

The expression of Ki-67 and Glypican -3 in hepatocellular carcinoma was evaluated by comparing DWI and 18F-FDG PET/CT

Objective

The value of DWI and 18F-FDG PET/CT in evaluating the expression of Ki-67 and GPC-3 in HCC was compared.

Materials and methods

Ninety-four patients with primary HCC confirmed by pathology were retrospectively divided into high- and low-Ki-67-expression groups and positive- and negative- GPC-3 groups. The ADC and SUVmax values of the lesions in both groups were measured. ROC curves were used to evaluate the identification efficiency of parameters with significant differences for each group of lesions, and AUCwas calculated. The combined ADC and SUVmax values were analyzed by binary logistic regression. The Delong test was used to compare the AUC values of the combined and single parameters. Pearson (in line with normal distribution) or Spearman (in line with abnormal distribution) correlation analysis was used to analyze the correlation.

Results

The ADC value of the high-Ki-67-expression group was lower than that of the low-Ki-67-expression group (P<0.05), and the SUVmax value of the high-expression group was higher than that of the low-expression group (P<0.05). The ADC value of the positive-GPC-3 group was lower than that of the negative group (P<0.0.tive group (P<0.05). The combined ADC and SUVmax values in the GPC-3 group were better than those of a single parameter (P<0.05). There was a strong negative correlation between the SUVmax value and ADC value in the Ki-67 group (R=-0.578, P<0.001) and a weak negative correlation between the SUVmax value and ADC value in the GPC-3 group (R=-0.279, P=0.006). The SUVmax value was strongly positively correlated with the Ki-67 expression index (R=0.733, P<0.001), while the ADC value was strongly negatively correlated with the Ki-67 expression index (R=-0.687, P<0.001).

Conclusion

DWI and 18F-FDG PET/CT can be used to evaluate the expression of Ki-67 and GPC-3 in HCC, and there is a certain correlation between the ADC value and SUVmax. Combined DWI and 18F-FDG PET/CT is superior to a single technique in evaluating the expression of GPC-3 in HCC patients. However, the combined model did not benefit the Ki-67 group.

pH-activated nanoplatform for visualized photodynamic and ferroptosis synergistic therapy of tumors

To overcome drug resistance and improve precision theranostics for hepatocellular carcinoma (HCC), a nanoplatform with an "off/on" function for multimodality imaging (near-infrared-II (NIR-II) fluorescence imaging, magnetic resonance imaging (MRI), and photoacoustic imaging) and synergistic therapy (photodynamic therapy and ferroptosis) activated by an acidic pH in the tumor microenvironment is proposed. Although many photosensitizers with photodynamic effects have been reported, very few of them have outstanding photodynamic effect and high stability with response to endogenous stimuli capable of NIR-II imaging. Herein, a new amphiphilic photosensitizer SR780 derived from croconaine dye, was developed with satisfactory photodynamic effects and pH-responsive NIR-II imaging. Interestingly, it was deactivated by coordination with Fe³⁺ (SR780@Fe) and activated during their release under mild acidic condition. Ferroptosis can generate hydroxyl free radical and lipid peroxide, which aggravate the oxidative stress of tumor cells and mediate their death while depleting glutathione (GSH) to enhance photodynamic effect. In situ pH-activatable theranostic nanoplatform, SR780@Fe-PAE-GP, was thus developed by loading SR780@Fe with pH-responsive polymers, modified by a glypican-3 (GPC-3) receptor-targeting peptide. The synergistic antitumor effects were confirmed both in vitro and in vivo, and the tumor inhibition rate of the SR780@Fe-PAE-GP + L treatment group reached 98%.

Noninvasively visualize the expression of LAPTM4B protein using a novel 18F-labeled peptide PET probe in hepatocellular carcinoma

OBJECTIVE

Lysosomal protein transmembrane 4 beta (LAPTM4B) is selectively expressed in hepatocellular carcinoma (HCC) cells and thus a potential biomarker for diagnosing HCC. In this study, we designed a novel 18F-labeled PET probe to non-invasively visualize LAPTM4B expression in mouse model of HCC tumor.

METHODS

A PET targeting tracer named [18F]FP-LAP2H was radio-synthesized using a LAPTM4B targeting peptide, LAP2H, coupled with 4-nitrophenyl-2-[18F]fluoropropionate ([18F]NFP). Radio-stability, cell uptake, micro PET/CT imaging and ex vivo biodistribution were performed for determining its stability, cell binding specificity, and tumor targeting in vivo.

RESULTS

[18F]FP-LAP2H was successfully synthesized with radiochemical yields of 6-14% (decay-corrected yield) and molar activity of 10-44 GBq/μmol. The tracer showed stable (~90%) in phosphate-buffered saline, pH 7.4, and in human serum (~80%) for 2 h. In vitro cell uptake studies indicated the radioactivity accumulation in HCC cells was LAPTM4B protein-specific. Micro PET/CT demonstrated that implanted LAPTM4B positive HepG2 and BEL7402 tumors could be clearly visualized. The ex vivo biodistribution studies demonstrated that the tumor/liver ratio were 1.80 ± 0.65 and 2.09 ± 0.68 in implanted HepG2 and BEL7402 tumors respectively. Negative control and blocking experiments revealed that the radioactivity uptake in the HCC tumor was LAPTM4B protein-specific.

CONCLUSIONS

[18F]FP-LAP2H appears to be a potential PET tracer for imaging LAPTM4B-positive HCC tumor. Further endeavors need to do to improve tumor/liver ratio.

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

Simple Summary

Liver cancer, the majority of which is hepatocellular carcinoma, is a typically fatal adult liver malignancy. It is hard to detect in the early stages of the cancer, and therefore patients are often diagnosed at the advanced stages, when treatment options become more limited and survival outcomes are poor. To improve early detection, and therefore treatment and prognosis of liver cancer patients, we have developed an imaging probe for positron emission tomography, targeting a protein, glypican-3, which is specifically expressed at high levels in liver cancer cells. Our probe consists of the ⁸⁹Zr radioisotope conjugated to a humanized monoclonal antibody against glypican-3, and it demonstrates specific ability to detect patient-derived liver cancer xenografts in a mouse model. With a high tumor to normal liver contrast, we believe this imaging probe can provide a useful tool in the early diagnosis and timely medical intervention for liver cancer patients.

Abstract

Glypican-3 (GPC3) is an attractive diagnostic marker for hepatocellular carcinoma (HCC). We previously reported the potential of an ⁸⁹Zr-labeled murine anti-GPC3 antibody (clone 1G12) for immunoPET imaging of HCC in orthotopic patient-derived xenograft (PDX) mouse models. We now humanized the murine antibody by complementarity determining region (CDR) grafting, to allow its clinical translation for human use. The engineered humanized anti-GPC3 antibody, clone H3K3, retained comparable binding affinity and specificity to human GPC3. H3K3 was conjugated with desferrioxamine (Df) and radiolabeled with ⁸⁹Zr to produce the PET/CT tracer ⁸⁹Zr-Df-H3K3. When injected into GPC3-expressing orthotopic HCC PDX in NOD SCID Gamma (NSG) mice, ⁸⁹Zr-Df-H3K3 showed specific high uptake into the orthotopic PDX and minimal, non-specific uptake into the non-tumor bearing liver. Specificity was demonstrated by significantly higher uptake of ⁸⁹Zr-Df-H3K3 into the non-blocked PDX mice, compared with the blocked PDX mice (which received prior injection of 100 mg of unlabeled H3K3). Region of interest (ROI) analysis showed that the PDX/non-tumor liver ratio was highest (mean ± SD: 3.4 ± 0.31) at 168 h post injection; this ratio was consistent with biodistribution studies at the same time point. Thus, our humanized anti-GPC3 antibody, H3K3, shows encouraging potential for use as an immunoPET tracer for diagnostic imaging of HCC patients.

Evaluation of Glypican-3 Expression in Hepatocellular Carcinoma by Using IDEAL IQ Magnetic Resonance Imaging

RATIONALE AND OBJECTIVES

To investigate the value of iterative decomposition of water and fat with echo asymmetry and least squares estimation (IDEAL IQ) and gadolinium-ethoxybenzyl-diethylenetriamine (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) for evaluating Glypican-3 (GPC3) expression in hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Seventy-six patients with histopathologic diagnosis of HCC were retrospectively included in this study. In all patients IDEAL IQ and Gd-EOB-DTPA-enhanced MRI were performed preoperatively using a 3 T MRI system. For an identical slice through the liver of each patient a region of interest was drawn on the tumor in the hepatobiliary phase image and copied to the R2* map and fat fraction map produced by IDEAL IQ. A Mann-Whitney U test was used to compare the region of interest values of R2*, fat fraction and uptake of Gd-EOB-DTPA values between patients with positive and negative GPC3 expression HCC. Receiver operating characteristic analysis was used to determine the diagnostic performances of each of the MRI parameters in evaluating GPC3 expression and histological grade in HCC.

RESULTS

R2* value was significantly higher in cases of positive than negative GPC3 expression HCCs (p < 0.001), whereas there were no significant differences in fat fraction and uptake of Gd-EOB-DTPA between the 2 groups (both p > 0.05). R2* value had higher areas under receiver operating characteristic (0.881), sensitivity (85.96%), and specificity (84.21%) compared to the fat fraction and uptake of Gd-EOB-DTPA.

CONCLUSION

R2* value yielded from IDEAL IQ could reliably predict GPC3 expression in HCC prior to surgery.

The development of a Glypican-3-specific binding peptide using in vivo and in vitro two-step phage display screening for the PET imaging of hepatocellular carcinoma

Glypican-3 (GPC3) is a diagnostic biomarker for hepatocellular carcinoma (HCC). Although numerous designs targeting GPC3 have been reported, the HCC diagnostic agents with specific tumor accumulation and low background, particularly in normal liver tissue, are still in need. Peptides have attracted considerable attention as an imaging probe due to their low immunogenicity, short in vivo circulation time, and acceptable production cost. Herein, a two-step phage display screening approach was performed against GPC3-high expression tumor xenografts in vivo, followed by human recombinant GPC3 protein in vitro. A GPC3-specific binding peptide, named TJ12P2, with the sequence of Ser-Asn-Asp-Arg-Pro-Pro-Asn-Ile-Leu-Gln-Lys-Arg (SNDRPPNILQKR) was identified. The apparent Kd value between TJ12P2 and the GPC3 protein was measured as 158.2 ± 26.25 nM. After 18F labeling, 18F-AlF-NOTA-TJ12P2 was found accumulated in the tumors by positron emission tomography (PET) imaging in two HCC subcutaneous tumor models (HepG2 and SMMC-7721) with high GPC3 expression. Static PET imaging revealed that 18F-AlF-NOTA-TJ12P2 accumulation in the HepG2 and SMMC-7721 tumors reached 1.825 ± 0.296 %ID g-1 and 1.575 ± 0.520 %ID g-1, with tumor-to-muscle ratios of 4.14 ± 0.50 and 4.25 ± 0.25, respectively, at 30 min post-injection (p.i.). Much less accumulation (0.533 ± 0.078 %ID g-1) of the 18F-AlF-NOTA-TJ12P2 was found in the control PC3 tumors with low GPC3 expression. More importantly, no obvious normal liver uptake of TJ12P2 was observed in the abovementioned animal models. As a result, a novel peptide targeting GPC3, TJ12P2, with strong affinity and specificity was identified using a two-step phage display screening technique in the present study. The 18F-AlF-NOTA-TJ12P2 may be a promising PET imaging probe with translational potential for accurate HCC diagnosis.

SPECT Imaging of Hepatocellular Carcinoma Detection by the GPC3 Receptor

The glypican-3 (GPC3) receptor is a membrane protein that is highly expressed in tumor tissues but rarely expressed in the normal liver and can be used as a target for early diagnosis of hepatocellular carcinoma (HCC). Herein, we developed a GPC3-targeted ^99mTc-labeled probe for SPECT imaging in HCC. ^99mTc-HPG was rapidly radiosynthesized within 20 min with an excellent radiochemical purity (>98%), possessing good stability. Results from in vitro cell binding assays indicated that the binding specificity of ^99mTc-HPG to GPC3-positive HepG2 cells was acceptable. For SPECT/CT imaging, the HepG2 tumors were clearly visualized with the highest tumor/muscle ratio (11.55 ± 0.54) at 1 h post-injection, and the tumor uptake of ^99mTc-HPG reduced from 2.99 ± 0.15 to 1.17 ± 0.09% ID/g in the blocking study. Convenient preparation, excellent GPC3 specificity in HCC, rapid clearance from normal organs, and good biosafety profiles of ^99mTc-HPG warrant further investigations for clinical translation.

Radiolabeled Peptide Probes for Liver Cancer Imaging

Liver cancer/Hepatocellular Carcinoma (HCC) is a leading cause of cancer death and represents an important cause of mortality worldwide. Several biomarkers are overexpressed in liver cancer, such as Glypican 3 (GPC3) and Epidermal Growth Factor Receptor (EGFR). These biomarkers play important roles in the progression of tumors and could serve as imaging and therapeutic targets for this disease. Peptides with adequate stability, receptor binding properties, and biokinetic behavior have been intensively studied for liver cancer imaging. A great variety of them have been radiolabeled with clinically relevant radionuclides for liver cancer diagnosis, and many are promising imaging and therapeutic candidates for clinical translation. Herein, we summarize the advancement of radiolabeled peptides for the targeted imaging of liver cancer.

Serum Tumor Markers for Early Diagnosis of Primary Hepatocellular Carcinoma

Primary hepatocellular carcinoma (HCC) is one of the most frequently occurring pernicious tumors in the world. It is typically very insidious in the early stages with no obvious symptoms. Its development and metastasis are very rapid. Upon diagnosis, most patients have already reached a local advanced stage or have established distant metastases. The treatment of HCC is limited, with poor prognosis and short natural survival time. In order to improve the efficiency of early diagnosis, it is particularly significant to choose economic and effective diagnosis methods. Ultrasound, magnetic resonance imaging, and computed tomography are usually used in the clinic, but these methods are extremely limited in the diagnosis of HCC. Tumor markers have become the main effective early clinical diagnosis method. Potential serum tumor markers include alpha fetoprotein heterogeneity, Golgi protein 73, phosphatidylinositol proteoglycan (GPC-3), osteopontin, abnormal prothrombin, and heat shock protein. These tumor markers provide new ideas and methods for the diagnosis of HCC. A combination of multiple markers can make up for the deficiency of single marker detection and provide a new strategy for the prognosis and auxiliary diagnosis of HCC. This review introduces protein tumor markers utilized over the past five years.

A novel targeted GPC3/CD3 bispecific antibody for the treatment hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most frequent primary liver cancer but has shown limited success to date in the treatment of advanced stage. Recruitment of T cells for cancer treatment is a rapidly growing strategy in immunotherapy such as chimeric antigen receptor T cells and bispecific antibodies. However, unwanted aggregations, structural instability or short serum half-life are major challenges of bispecific antibodies. Here, we developed a new format of T cell-redirecting antibody that is bispecific for membrane proteoglycans GPC3 of HCC and the T-cell-specific antigen CD3, which demonstrated to be favorable stability and productivity. Cross-linking of T cells with GPC3 positive tumor cells by the anti-GPC3/CD3 bispecific antibody-mediated potent GPC3-dependent and concentration-dependent cytotoxicity in vitro. Administration of the bispecific antibody with different concentrations in murine xenograft models of human HCC significantly inhibited tumor growth. In addition, no effects on tumor growth were observed in the absence of human effector cells or the bispecific antibody. Taken together, the anti-GPC3/CD3 bispecific antibody might be a potential therapeutic treatment for HCC.

Radiofluorinated GPC3-Binding Peptides for PET Imaging of Hepatocellular Carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) remains one of the most challenging diseases worldwide. Glypican-3 (GPC-3) is a cell surface proteoglycan that is overexpressed on the membrane of HCC cells. The purpose of this study was to develop a target-specific radiofluorinated peptide for positron emission tomography (PET) imaging of GPC3 expression in hepatocellular carcinoma.

PROCEDURES

New GPC3-binding peptides (GP2076 and GP2633) were radiolabeled with F-18 using Al[¹⁸F]F labeling approach, and the resulting PET probes were subsequently subject to biological evaluations. A highly hydrophilic linker was incorporated into GP2633 with an aim of reducing the probe uptake in liver and increasing tumor-to-liver (T/L) contrast. Both GP2076 and GP2633 were radiolabeled using Al[¹⁸F]F chelation approach. The binding affinity, octanol/water partition coefficient, cellular uptake and efflux, and stability of both F-18 labeled peptides were tested. Tumor targeting efficacy and biodistribution of Al[¹⁸F]F-GP2076 and Al[¹⁸F]F-GP2633 were determined by PET imaging in HCC-bearing mice. Immunohistochemistry analyses were performed to compare the findings from PET scans.

RESULTS

Al[¹⁸F]F-GP2076 and Al[¹⁸F]F-GP2633 were rapidly radiosynthesized within 20 min in excellent radiochemical purity (> 97 %). Al[¹⁸F]F-GP2633 was determined to be more hydrophilic than Al[¹⁸F]F-GP2076 in terms of octanol/water partition coefficient. Both Al[¹⁸F]F-GP2076 and Al[¹⁸F]F-GP2633 demonstrated good in vitro and in vivo stability and binding specificity to GPC3-positive HepG2 cells. For PET imaging, Al[¹⁸F]F-GP2633 exhibited enhanced uptake in HepG2 tumor (%ID/g 3.37 ± 0.35 vs. 2.13 ± 0.55, P = 0.031) and reduced accumulation in liver (%ID/g 1.70 ± 0.26 vs. 3.70 ± 0.98, P = 0.027) at 60 min post-injection (pi) as compared to Al[¹⁸F]F-GP2076, resulting in significantly improved tumor-to-liver (T/L) contrast (ratio 2.00 ± 0.18 vs. 0.59 ± 0.14, P = 0.0004). Higher uptake of Al[¹⁸F]F-GP2633 in GPC3-positive HepG2 tumor was observed as compared to GPC3-negative McA-RH7777 tumor (%ID/g 3.37 ± 0.35 vs. 1.64 ± 0.03, P = 0.001) at 60 min pi, confirming GPC3-specific accumulation of Al[¹⁸F]F-GP2633 in HepG2 tumor.

CONCLUSION

The results demonstrated that Al[¹⁸F]F-GP2633 is a promising probe for PET imaging of GPC3 expression in HCC. Convenient preparation, excellent GPC3 specificity in HCC, and favorable excretion profile of Al[¹⁸F]F-GP2633 warrant further investigation for clinical translation. PET imaging with a GPC3-specific probe would provide clinicians with vital diagnostic information that could have a significant impact on the management of HCC patients.

808 nm Near-Infrared Light-Excited UCNPs@mSiO2-Ce6-GPC3 Nanocomposites For Photodynamic Therapy In Liver Cancer

Background

It is important to explore effective treatment for liver cancer. Photodynamic therapy (PDT) is a novel technique to treat liver cancer, but its clinical application is obstructed by limited depth of visible light penetration into tissue. The near-infrared (NIR) photosensitizer is a potential solution to the limitations of PDT for deep tumor tissue treatment.

Purpose

We aimed to investigate 808 nm NIR light-excited UCNPs@mSiO₂-Ce6-GPC3 nanocomposites for PDT in liver cancer.

Methods

In our study, 808 nm NIR light-excited upconversion nanoparticles (UCNPs) were simultaneously loaded with the photosensitizer chlorin e6 (Ce6) and the antibody glypican-3 (GPC3), which is overexpressed in hepatocellular carcinoma cells. The multitasking UCNPs@mSiO₂-Ce6-GPC3 nanoparticles under 808 nm laser irradiation with enhanced depth of penetration would enable the effective targeting of PDT.

Results

We found that the UCNPs@mSiO₂-Ce6-GPC3 nanoparticles had good biocompatibility, low toxicity, excellent cell imaging in HepG2 cancer cells and high anti-tumor effect in vitro and in vivo.

Conclusion

We believe that the utilization of 808 nm NIR excited UCNPs@mSiO₂-Ce6-GPC3 nanoparticles for PDT is a safe and potential therapeutic option for liver cancer.

Cobalt Chloride Induced Apoptosis by Inhibiting GPC3 Expression via the HIF-1α/c-Myc Axis in HepG2 Cells

Purpose

To investigate the role of glypican-3 (GPC3) in cobalt chloride (CoCl₂)-induced cell apoptosis in hepatocellular carcinoma.

Methods

HepG2 cells were treated with CoCl₂ in the absence or presence of GPC3 plasmid transfection. Cell viability and apoptosis were assessed by MTT assay and flow cytometry, respectively. The expression of GPC3, hypoxia-inducible factor 1α (HIF-1α), c-myc, sp1, poly-ADP-ribose polymerase (PARP) and caspase-3 was determined by real-time PCR, Western blotting, and immunofluorescence after the cells were treated with different concentrations of CoCl₂ or siRNA targeting HIF-1α.

Results

CoCl₂ significantly inhibited the proliferation of HepG2 cells and induced apoptosis. Additionally, the expression of GPC3 mRNA and protein was decreased, and overexpression of GPC3 attenuated the tumour inhibiting effects. Further studies showed that CoCl₂ increased the expression of HIF-1α while reducing the expression of sp1 and c-myc; knockdown of HIF-1α elevated the expression of GPC3, sp1, and c-myc.

Conclusion

CoCl₂ inhibited the growth of HepG2 cells through downregulation of GPC3 expression via the HIF-1α/c-myc axis.

Glypican 3-Targeted Therapy in Hepatocellular Carcinoma

Glypican-3 (GPC3) is an oncofetal glycoprotein attached to the cell membrane by a glycophosphatidylinositol anchor. GPC3 is overexpressed in some kinds of tumors, particularly hepatocellular carcinoma (HCC). The prognostic significance of serum GPC3 levels and GPC3 immunoreactivity in tumor cells has been defined in patients with HCC. In addition to its usefulness as a biomarker, GPC3 has attracted attention as a novel therapeutic target molecule, and clinical trials targeting GPC3 are in progress. The major mechanism of anti-GPC3 antibody (GPC3Ab) against cancer cells is antibody-dependent cellular cytotoxicity and/or complement-dependent cytotoxicity. Since GPC3Ab is associated with immune responses, a combination of protocols with immune checkpoint inhibitors has also been investigated. Moreover, some innovative approaches for GPC3-targeting therapy have emerged in recent years. This review introduces the results of recent clinical trials targeting GPC3 in HCC and summarizes the latest knowledge regarding the role of GPC3 in HCC progression and clinical application targeting GPC3.

In Vitro Performance of Published Glypican 3-Targeting Peptides TJ12P1 and L5 Indicates Lack of Specificity and Potency

Background: Glypican 3 (GPC3), a plasma membrane heparan sulfate proteoglycan, is overexpressed on human hepatocellular carcinoma and may represent a promising biomarker. Several studies have reported peptides that selectively bind to GPC3 and could serve as scaffolds for imaging or therapeutic agents.

Materials and Methods: We synthesized variants of two previously published peptides, DHLASLWWGTEL (TJ12P1) and RLNVGGTYFLTTRQ (L5), and evaluated their in vitro binding performance in paired isogenic cell lines, A431(GPC3⁻) and A431-GPC3⁺ (G1), as well as the liver cancer cell line HepG2. Using flow cytometry and biolayer interferometry (BLI), we compared the binding of the TJ12P1 and L5 peptide variants to the binding of corresponding scrambled peptides having the same amino acid composition, but in random sequence.

Results: While both peptides bound to G1 and HepG2, they also bound to A431. The corresponding scrambled peptides demonstrated greater apparent binding to both G1 and A431 than their specific counterparts. BLI confirmed lack of binding at 0.5–1 μM for both peptides.

Conclusions: We conclude that neither TJ12P1 nor L5 variant demonstrates selectivity for GPC3 at concentrations near the reported K_D, and that the peptides lack potency or are nonspecific, making them inadequate for use as imaging agents.

An innovative peptide with high affinity to GPC3 for hepatocellular carcinoma diagnosis

Glypican-3 (GPC3) is a key biomarker for early diagnosis of human hepatocellular carcinoma (HCC) due to its overexpression in most HCC tumor tissues. Recently, peptides with high affinity to GPC3 have attracted more attention because of their high biocompatibility, non-immunogenicity, fast clearing and easy modification. Herein, we have designed an innovative GPC3 targeting peptide (sequence: DYEMHLWWGTEL, denoted as IPA) by using structure-based virtual simulation. The higher binding abilities of IPA over the reported peptide (YP) were displayed on different cell lines, showing a positive correlation with GPC3 expressions, which were further verified by the GPC3 protein binding assay. The GPC3 targeting specificity of IPA was proved by peptide blocking and siRNA experiment. The localized anchor of peptide IPA on the cell membranes of HepG2 and Huh-7 with GPC3 overexpression confirmed the GPC3 binding capacity. By connecting a near-infrared dye MPA, the in vivo identification ability of IPA to GPC3 was also demonstrated on GPC3-positive (HepG2) and GPC3-negative (U87) xenograft-bearing mice. These results indicated that the designed IPA presented desirable GPC3 targeting ability, showing promising prospects in detecting the expression of GPC3 for HCC targeting imaging.