Depicting changes in tumor biology in response to cetuximab mono- or combination therapy by apoptosis and proliferation imaging using 18F-ICMT-11 and 3’-Deoxy-3’-[18F]Fluorothymidine (18F-FLT) PET

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Title: Depicting changes in tumor biology in response to cetuximab mono- or combination therapy by apoptosis and proliferation imaging using 18F-ICMT-11 and 3’-Deoxy-3’-[18F]Fluorothymidine (18F-FLT) PET
Authors: Heinzmann, K
Nguyen, Q-D
Honess, D
Smith, D-M
Stribbling, S
Brickute, D
Barnes, C
Griffiths, J
Aboagye, E
Item Type: Journal Article
Abstract: Imaging biomarkers must demonstrate their value in monitoring treatment. Two PET tracers, the caspase-3/7–specific isatin-5-sulfonamide 18F-ICMT-11 (18F-(S)-1-((1-(2-fluoroethyl)-1H-[1,2,3]-triazol-4-yl)methyl)-5-(2(2,4-difluoro-phenoxymethyl)-pyrrolidine-1-sulfonyl)isatin) and 18F-FLT (3′-deoxy-3′-18F-fluorothymidine), were used to detect early treatment-induced changes in tumor biology and determine whether any of these changes indicate a response to cetuximab, administered as monotherapy or combination therapy with gemcitabine. Methods: In mice bearing cetuximab-sensitive H1975 tumors (non–small lung cancer), the effects of single or repeated doses of the antiepidermal growth factor receptor antibody cetuximab (10 mg/kg on day 1 only or on days 1 and 2) or a single dose of gemcitabine (125 mg/kg on day 2) were investigated by 18F-ICMT-11 or 18F-FLT on day 3. Imaging was also performed after 2 doses of cetuximab (days 1 and 2) in mice bearing cetuximab-insensitive HCT116 tumors (colorectal cancer). For imaging–histology comparison, tumors were evaluated for proliferation (Ki-67 and thymidine kinase 1 [TK1]), cell death (cleaved caspase-3 and terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick-end labeling [TUNEL]), and target engagement (epidermal growth factor receptor expression) by immunohistochemistry, immunofluorescence, and immunoblotting, respectively. Tumor and plasma were analyzed for thymidine and gemcitabine metabolites by liquid chromatography–mass spectrometry. Results: Retention of both tracers was sensitive to cetuximab in H1975 tumors. 18F-ICMT-11 uptake and ex vivo cleaved caspase-3 staining notably increased in tumors treated with repeated doses of cetuximab (75%) and combination treatment (46%). Although a single dose of cetuximab was insufficient to induce apoptosis, it did affect proliferation. Significant reductions in tumor 18F-FLT uptake (44%–50%; P < 0.001) induced by cetuximab monotherapy and combination therapy were paralleled by a clear decrease in proliferation (Ki-67 decrease, 72%–95%; P < 0.0001), followed by a marked tumor growth delay. TK1 expression and tumor thymidine concentrations were profoundly reduced. Neither imaging tracer depicted the gemcitabine-induced tumor changes. However, cleaved caspase-3 and Ki-67 staining did not significantly differ after gemcitabine treatment whereas TK1 expression and thymidine concentrations increased. No cetuximab-induced modulation of the imaging tracers or other response markers was detected in the insensitive model of HCT116. Conclusion: 18F-ICMT-11 and 18F-FLT are valuable tools to assess cetuximab sensitivity depicting distinct and time-variant aspects of treatment response.
Issue Date: 1-Oct-2018
Date of Acceptance: 9-Apr-2018
ISSN: 1535-5667
Publisher: Society of Nuclear Medicine
Start Page: 1558
End Page: 1565
Journal / Book Title: Journal of Nuclear Medicine
Volume: 59
Issue: 10
Copyright Statement: ©2018 by the Society of Nuclear Medicine and Molecular Imaging. Creative Commons Attribution 4.0 InternationalLicense (CC BY) allows users to share and adapt with attribution, excludingmaterials credited to previous publications. License: Details:
Sponsor/Funder: Commission of the European Communities
Funder's Grant Number: 115151
Keywords: Science & Technology
Life Sciences & Biomedicine
Radiology, Nuclear Medicine & Medical Imaging
PET imaging
anti-EGFR-based therapy
Nuclear Medicine & Medical Imaging
1103 Clinical Sciences
Publication Status: Published
Online Publication Date: 2018-05-24
Appears in Collections:Division of Surgery
Division of Cancer
Faculty of Medicine

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