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PET of EGFR antibody distribution in head and neck squamous cell carcinoma models.

ABSTRACT: UNLABELLED:Epidermal growth factor receptor (EGFR) is a well-characterized protooncogene that has been shown to promote tumor progression in solid cancers. Clinical results for EGFR targeting with specific monoclonal antibodies (mAbs) such as cetuximab and panitumumab are promising; however, most studies indicate that only a subgroup of patients receiving the mAbs benefit from the immunotherapy, independent of EGFR expression level. To understand the in vivo kinetics of antibody delivery and localization, we performed small-animal PET studies with (64)Cu-labeled panitumumab in xenografts derived from 3 cell lines of human head and neck squamous cell carcinoma (HNSCC). METHODS:Nude mice bearing HNSCC tumors with different levels of EGFR expression were imaged with small-animal PET using (64)Cu-1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA)-panitumumab. Antibody distribution in the tumors was confirmed by ex vivo immunostaining using panitumumab and fluorescein 5(6)-isothiocyanate (FITC) panitumumab. CD31 immunostaining and Evans blue assay were also performed to assess the tumor vascular density and permeability. RESULTS:Among these 3 tumor models, UM-SCC-22B tumors with the lowest EGFR protein expression showed the highest (64)Cu-DOTA-panitumumab accumulation, whereas SQB20 tumors with the highest EGFR expression showed the lowest (64)Cu-DOTA-panitumumab accumulation. Ex vivo staining demonstrated that SQB20 cells still had extremely high EGFR expression after forming tumors in nude mice, indicating that the low uptake of (64)Cu-DOTA-panitumumab in SQB20 tumors was not due to the loss of EGFR expression. The results from CD31 immunostaining and Evans blue permeability assay suggest that the low vessel density, poor vascular permeability, and binding site barrier are likely responsible for the overall low tumor uptake of the highly EGFR-expressing SQB20 tumors. CONCLUSION:The results from this study provide a possible explanation for the lack of an observed correlation between therapeutic efficacy of cetuximab and panitumumab and EGFR expression level as determined by immunohistochemistry or fluorescent in situ hybridization and may shed new light on the complications of anti-EGFR mAb therapy for HNSCC and other malignancies.

SUBMITTER: Niu G

PROVIDER: S-EPMC6435376 | biostudies-literature | 2009 Jul

REPOSITORIES: biostudies-literature

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PET of EGFR antibody distribution in head and neck squamous cell carcinoma models.

Niu Gang G Li Zibo Z Xie Jin J Le Quynh-Thu QT Chen Xiaoyuan X

Journal of nuclear medicine : official publication, Society of Nuclear Medicine 20090612 7

<h4>Unlabelled</h4>Epidermal growth factor receptor (EGFR) is a well-characterized protooncogene that has been shown to promote tumor progression in solid cancers. Clinical results for EGFR targeting with specific monoclonal antibodies (mAbs) such as cetuximab and panitumumab are promising; however, most studies indicate that only a subgroup of patients receiving the mAbs benefit from the immunotherapy, independent of EGFR expression level. To understand the in vivo kinetics of antibody delivery ...[more]

PMID: 19525473

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Project description:In head and neck squamous cell cancer, the human epidermal growth factor receptor 1 (EGFR) is the dominant signaling molecule among all members of the family. So far, cetuximab is the only approved anti-EGFR monoclonal antibody used for the treatment of head and neck squamous cell cancer, but despite the benefits of adding it to standard treatment regimens, attempts to define a predictive biomarker to stratify patients for cetuximab treatment have been unsuccessful. We hypothesized that imaging with EGFR-specific radioligands may facilitate noninvasive measurement of EGFR expression across the entire tumor burden and allow for dynamic monitoring of cetuximab-mediated changes in receptor expression. Methods: EGFR-specific Affibody molecule (ZEGFR:03115) was radiolabeled with 89Zr and 18F. The radioligands were characterized in vitro and in mice bearing subcutaneous tumors with varying levels of EGFR expression. The protein dose for imaging studies was assessed by injecting 89Zr-deferoxamine-ZEGFR:03115 (2.4-3.6 MBq, 2 μg) either together with or 30 min after increasing amounts of unlabeled ZEGFR:03115 (1, 5, 10, 15, and 20 μg). PET images were acquired at 3, 24, and 48 h after injection, and the image quantification data were correlated with the biodistribution results. The EGFR expression and biodistribution of the tracer were assessed ex vivo by immunohistochemistry, Western blot, and autoradiography. To downregulate the EGFR level, treatment with cetuximab was performed, and 18F-aluminium fluoride-NOTA-ZEGFR:03115 (12 μg, 1.5-2 MBq/mouse) was used to monitor receptor changes. Results: In vivo studies demonstrated that coinjecting 10 μg of nonlabeled molecules with 89Zr-deferoxamine-ZEGFR:03115 allows for clear tumor visualization 3 h after injection. The radioconjugate tumor accumulation was EGFR-specific, and PET imaging data showed a clear differentiation between xenografts with varying EGFR expression levels. A strong correlation was observed between PET analysis, ex vivo estimates of tracer concentration, and receptor expression in tumor tissues. Additionally, 18F-aluminium fluoride-NOTA-ZEGFR:03115 could measure receptor downregulation in response to EGFR inhibition. Conclusion: ZEGFR:03115-based radioconjugates can assess different levels of EGFR level in vivo and measure receptor expression changes in response to cetuximab, indicating a potential for assessment of adequate treatment dosing with anti-EGFR antibodies.

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PET of EGFR antibody distribution in head and neck squamous cell carcinoma models.

Publications

PET of EGFR antibody distribution in head and neck squamous cell carcinoma models.

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