PET of EGFR with ⁶⁴Cu‐cetuximab‐F(ab′)₂ in mice with head and neck squamous cell carcinoma xenografts

Abstract

a Overexpression of the epidermal growth factor receptor (EGFR) is linked to an adverse outcome in various solid tumors. Cetuximab is an EGFR inhibitor, which in combination with radiotherapy improves locoregional control and survival in a subgroup of patients with head and neck squamous cell carcinomas (HNSCCs). The aim of this study was to develop and characterize an EGFR-directed PET tracer, 64 Cu-cetuximab-F(ab′) 2 , to determine the systemic accessibility of EGFR. Mice with HNSCC xenografts, UT-SCC-8 (n = 6) or UT-SCC-45 (n = 6), were imaged 24 h post injection with 64 Cu-NODAGA-cetuximab-F(ab′) 2 using PET/CT. One mouse for each tumor model was co-injected with excess unlabeled cetuximab 3 days before radiotracer injection to determine non-EGFR-mediated uptake. Ex vivo biodistribution of the tracer was determined and tumors were analyzed by autoradiography and immunohistochemistry. The SUV max of UT-SCC-8 tumors was higher than that of UT-SCC-45: 1.5 ± 1.0 and 0.8 ± 0.2 (p < 0.05), respectively. SUV max after in vivo blocking of EGFR with cetuximab was 0.4. Immunohistochemistry showed that UT-SCC-8 had a significantly higher EGFR expression than UT-SCC-45: 0.50 ± 0.19 versus 0.12 ± 0.08 (p < 0.005), respectively. Autoradiography indicated that 64 Cu-cetuximab-F(ab′) 2 uptake correlated with EGFR expression in both tumors: r = 0.86 ± 0.06 (UT-SCC-8) and 0.90 ± 0.06 (UT-SCC-45).64 Cu-cetuxmab-F(ab′) 2 is a promising PET tracer to determine expression of EGFR in vivo. Clinically, this tracer has the potential to be used to determine cetuximab targeting of tumors and possibly to non-invasively monitor the response to EGFR-inhibitor treatment.

Influence of composition of cysteine-containing peptide-based chelators on biodistribution of 99mTc-labeled anti-EGFR affibody molecules

“…The use of radionuclide molecular imaging of EGFR expression can overcome many of these problems (Pantaleo et al 2009). The unmet clinical need for sensitive detection of EGFR expression in disseminated malignancies has encouraged the development of radionuclide imaging probes based on monoclonal antibodies (Divgi et al 1991; Menke-van der Houven et al 2015; Makris et al 2015), antibody fragments (van Dijk et al 2016) and scaffold proteins (Kruziki et al 2016; Garousi et al 2017). One of the issues when imaging this particular target is the noticeable expression of EGFR in hepatocytes.…”

Feasibility of imaging of epidermal growth factor receptor expression with ZEGFR:2377 affibody molecule labeled with 99mTc using a peptide-based cysteine-containing chelator

“…However, all radiolabeled antibodies clear slowly from blood and non-specific compartments, which results in moderate contrast and requires several days between injection of the antibody and imaging. The use of smaller radiolabeled fragments of cetuximab as imaging agents increased appreciably the contrast of EGFR imaging and enabled shortening of the time between injection of the probe and the imaging session (29,30). A smaller size of the (Fab′) 2 -fragment contributed to both more rapid clearance and better tumor localization, which demonstrated advantages of a reduction of the imaging probe size for improved contrast.…”

Fully Automated Production and Characterization of 64Cu and Proof‐of‐Principle Small‐Animal PET Imaging Using 64Cu‐Labelled CA XII Targeting 6A10 Fab

“…Using chelator‐conjugated antibodies, 64 Cu has been investigated in studies against pancreatic cancer, malignant lymphoma, breast cancer, and carbonic anhydrase (CA) IX expressing malignant tissue . Antibody fragments (Fab and F(ab) 2 ), also radiolabelled with 64 Cu via chelators, have been used in studies against ovarian cancer, breast cancer, and head and neck cancer . Chelator molecules are further used to bind 64 Cu to peptides, such as RGD 2 ‐BBN heterotrimers against prostate cancer, and RGD peptides against gliomas .…”

“…[25] Antibody fragments (Fab and F(ab) 2 ), also radiolabelled with 64 Cu via chelators, have been used in studies against ovarian cancer, [26] breast cancer, [26,27] and heada nd neck cancer. [28] Chelator molecules are further used to bind 64 Cu to peptides, such as RGD 2 -BBN heterotrimers against prostatec ancer, [29] and RGD peptides against gliomas. [30] Chelator conjugating is even used to radiolabel nanoparticles [31] andl iposomes for breast cancer diagnosis.…”