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Glypican-3-targeted 89Zr PET imaging of hepatocellular carcinoma.

ABSTRACT: Hepatocellular carcinoma (HCC) is a devastating malignancy in which imperfect imaging plays a primary role in diagnosis. Glypican-3 (GPC3) is an HCC-specific cell surface proteoglycan overexpressed in most HCCs. This paper presents the use of (89)Zr-conjugated monoclonal antibody against GPC3 ((89)Zr-?GPC3) for intrahepatic tumor localization using PET.Polymerase chain reaction confirmed relative GPC3 expression in cell lines. In vitro binding, in vivo biodistribution, and small-animal PET studies were performed on GPC3-expressing HepG2 and non-GPC3-expressing HLF and RH7777 cells and orthotopic xenografts.(89)Zr-?GPC3 demonstrated antibody-dependent, antigen-specific tumor binding. HepG2 liver tumors exhibited high peak uptake (836.6 ± 86.6 percentage injected dose [%ID]/g) compared with background liver (27.5 ± 1.6 %ID/g). Tumor-to-liver contrast ratio was high and peaked at 32.5. The smallest HepG2 tumor (<1 mm) showed lower peak uptake (42.5 ± 6.4 %ID/g) and tumor-to-liver contrast (1.57) but was still clearly visible on PET. Day 7 tissue activity was still substantial in HepG2 tumors (466.4 ± 87.6 %ID/g) compared with control RH7777 tumors (3.9 ± 1.3 %ID/g, P < 0.01), indicating antigen specificity by (89)Zr-?GPC3. HepG2 tumor treated with unlabeled ?GPC3 or heat-denatured (89)Zr-?GPC3 demonstrated tumor activity (2.1 %ID/g) comparable to that of control xenografts, confirming antibody dependency.This study demonstrated the feasibility of using (89)Zr-?GPC3 to image HCC in the liver, as well as the qualitative determination of GPC3 expression via small-animal PET. The ability to clarify the identity of small liver lesions with an HCC-specific PET probe would provide clinicians with vital information that could significantly alter patient management, warranting further investigation for clinical translation.

SUBMITTER: Sham JG

PROVIDER: S-EPMC4116087 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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Glypican-3-targeted 89Zr PET imaging of hepatocellular carcinoma.

Sham Jonathan G JG Kievit Forrest M FM Grierson John R JR Miyaoka Robert S RS Yeh Matthew M MM Zhang Miqin M Yeung Raymond S RS Minoshima Satoshi S Park James O JO

Journal of nuclear medicine : official publication, Society of Nuclear Medicine 20140313 5

<h4>Unlabelled</h4>Hepatocellular carcinoma (HCC) is a devastating malignancy in which imperfect imaging plays a primary role in diagnosis. Glypican-3 (GPC3) is an HCC-specific cell surface proteoglycan overexpressed in most HCCs. This paper presents the use of (89)Zr-conjugated monoclonal antibody against GPC3 ((89)Zr-αGPC3) for intrahepatic tumor localization using PET.<h4>Methods</h4>Polymerase chain reaction confirmed relative GPC3 expression in cell lines. In vitro binding, in vivo biodistr ...[more]

PMID: 24627434

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Project description:UnlabelledHepatocellular carcinoma (HCC) is an increasingly lethal malignancy for which management is critically dependent on accurate imaging. Glypican-3 (GPC3) is a cell surface receptor overexpressed in most HCCs and provides a unique target for molecular diagnostics. The use of monoclonal antibodies (mAbs) that target GPC3 (αGPC3) in PET imaging has shown promise but comes with inherent limitations associated with mAbs such as long circulation times. This study used (89)Zr-conjugated F(ab')2 fragments directed against GPC3 ((89)Zr-αGPC3-F(ab')2) to evaluate the feasibility of the fragments as a diagnostic immuno-PET imaging probe.MethodsImmobilized ficin was used to digest αGPC3, creating αGPC3-F(ab')2 fragments subsequently conjugated to (89)Zr. In vivo biodistribution and PET studies were performed on GPC3-expressing HepG2 and GPC3-nonexpressing RH7777 orthotopic xenografts.ResultsReliable αGPC3-F(ab')2 production via immobilized ficin digestion was verified by high-performance liquid chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis. (89)Zr-αGPC3-F(ab')2 demonstrated F(ab')2-dependent, antigen-specific cell binding. HepG2 tumor uptake was higher than any other tissue, peaking at 100 ± 21 percentage injected dose per gram (%ID/g) 24 h after injection, a value 33- to 38-fold higher than GPC3-nonexpressing RH7777 tumors. The blood half-life of the (89)Zr-αGPC3-F(ab')2 conjugate was approximately 11 h, compared with approximately 115 h for historic mAb controls. This shorter half-life enabled clear tumor visualization on PET 4 h after administration, with a resultant peak tumor-to-liver contrast ratio of 23.3. Blocking antigen-expressing tumors with an excess of nonradiolabeled αGPC3 resulted in decreased tumor uptake similar to native liver. The kidneys exhibited high tissue uptake, peaking at 24 h with 83 ± 12 %ID/g. HepG2 tumors ranging from 1.5 to 7 mm were clearly visible on PET, whereas larger RH7777 tumors displayed signal lower than background liver tissue.ConclusionThis study demonstrates the feasibility of using (89)Zr-αGPC3-F(ab')2 for intrahepatic tumor localization with small-animal PET. Faster blood clearance and lower background liver uptake enable excellent signal-to-noise ratios at early time points. Increased renal uptake is similar to that as has been seen with clinical radioactive peptide imaging. (89)Zr-αGPC3-F(ab')2 addresses some of the shortcomings of whole-antibody immuno-PET probes. Further optimization is warranted to maximize probe sensitivity and specificity in the process of clinical translation.

Project description:PurposeHepatocellular 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.ProceduresNew 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.ResultsAl[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.ConclusionThe 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.

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Glypican-3-targeted 89Zr PET imaging of hepatocellular carcinoma.

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Glypican-3-targeted 89Zr PET imaging of hepatocellular carcinoma.

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