TY - JOUR
T1 - Evaluation of 4-[18F]fluorobenzoyl-FALGEA-NH2 as a positron emission tomography tracer for epidermal growth factor receptor mutation variant III imaging in cancer
AU - Denholt, Charlotte Lund
AU - Binderup, Tina
AU - Stockhausen, Marie-Thérése
AU - Poulsen, Hans Skovgaard
AU - Spang-Thomsen, Mogens
AU - Hansen, Paul Robert
AU - Gillings, Nicholas Mathew
AU - Kjær, Andreas
N1 - Copyright © 2011 Elsevier Inc. All rights reserved.
PY - 2011/5
Y1 - 2011/5
N2 - Introduction: This study describes the radiosynthesis, in vitro and in vivo evaluation of the novel small peptide radioligand, 4-[18F]fluorobenzoyl-Phe-Ala-Leu-Gly-Glu-Ala-NH2, ([18F]FBA-FALGEA-NH2) as a positron emission tomography (PET) tracer for imaging of the cancer specific epidermal growth factor receptor (EGFR) variant III mutation, EGFRvIII. Methods: For affinity, stability and PET measurements, H-FALGEA-NH2 was radiolabelled using 4-[18F]fluorobenzoic acid ([18F]FBA). The binding affinity of ([18F]FBA)-FALGEA-NH2 was measured on EGFRvIII expressing cells, NR6M. Stability studies in vitro and in vivo were carried out in blood plasma from nude mice. PET investigations of [18F]FBA-FALGEA-NH2 were performed on a MicroPET scanner, using seven nude mice xenografted subcutaneously with human glioblastoma multiforme (GBM) tumours, expressing the EGFRvIII in its native form, and five nude mice xenografted subcutaneously with GBM tumours lacking EGFRvIII expression. Images of [18F]FDG were also obtained for comparison. The mice were injected with 5-10 MBq of the radiolabelled peptide or [18F]FDG. Furthermore, the gene expression of EGFRvIII in the tumours was determined using quantitative real-time PCR. Results: Radiolabelling and purification was achieved within 180 min, with overall radiochemical yields of 2.6-9.8% (decay-corrected) and an average specific radioactivity of 6.4 GBq/μmol. The binding affinity (Kd) of [18F]FBA-FALGEA-NH2 to EGFRvIII expressing cells was determined to be 23 nM. The radiolabelled peptide was moderately stable in the plasma from nude mice where 53% of the peptide was intact after 60 min of incubation in plasma but rapidly degraded in vivo, where no intact peptide was observed in plasma 5 min post-injection.The PET imaging showed that [18F]FBA-FALGEA-NH2 accumulated preferentially in the human GBM xenografts which expressed high amounts of the mutated receptor. The average tumour-to-muscle ratio (T/M) in the EGFRvIII tumours was 7.8 at 60 min post-injection, compared with 4.6 in the wild-type EGFR tumours. Furthermore, there was a strong correlation (R=0.86, P=007) between the expression of EGFRvIII in the tumours and the tracer uptake expressed as T/M. Conclusion: Our results indicate that, despite its rapid metabolism, [18F]FBA-FALGEA-NH2 binds preferentially to EGFRvIII in the tumours in vivo and is a promising lead for further development of EGFRvIII specific peptide radiopharmaceuticals.
AB - Introduction: This study describes the radiosynthesis, in vitro and in vivo evaluation of the novel small peptide radioligand, 4-[18F]fluorobenzoyl-Phe-Ala-Leu-Gly-Glu-Ala-NH2, ([18F]FBA-FALGEA-NH2) as a positron emission tomography (PET) tracer for imaging of the cancer specific epidermal growth factor receptor (EGFR) variant III mutation, EGFRvIII. Methods: For affinity, stability and PET measurements, H-FALGEA-NH2 was radiolabelled using 4-[18F]fluorobenzoic acid ([18F]FBA). The binding affinity of ([18F]FBA)-FALGEA-NH2 was measured on EGFRvIII expressing cells, NR6M. Stability studies in vitro and in vivo were carried out in blood plasma from nude mice. PET investigations of [18F]FBA-FALGEA-NH2 were performed on a MicroPET scanner, using seven nude mice xenografted subcutaneously with human glioblastoma multiforme (GBM) tumours, expressing the EGFRvIII in its native form, and five nude mice xenografted subcutaneously with GBM tumours lacking EGFRvIII expression. Images of [18F]FDG were also obtained for comparison. The mice were injected with 5-10 MBq of the radiolabelled peptide or [18F]FDG. Furthermore, the gene expression of EGFRvIII in the tumours was determined using quantitative real-time PCR. Results: Radiolabelling and purification was achieved within 180 min, with overall radiochemical yields of 2.6-9.8% (decay-corrected) and an average specific radioactivity of 6.4 GBq/μmol. The binding affinity (Kd) of [18F]FBA-FALGEA-NH2 to EGFRvIII expressing cells was determined to be 23 nM. The radiolabelled peptide was moderately stable in the plasma from nude mice where 53% of the peptide was intact after 60 min of incubation in plasma but rapidly degraded in vivo, where no intact peptide was observed in plasma 5 min post-injection.The PET imaging showed that [18F]FBA-FALGEA-NH2 accumulated preferentially in the human GBM xenografts which expressed high amounts of the mutated receptor. The average tumour-to-muscle ratio (T/M) in the EGFRvIII tumours was 7.8 at 60 min post-injection, compared with 4.6 in the wild-type EGFR tumours. Furthermore, there was a strong correlation (R=0.86, P=007) between the expression of EGFRvIII in the tumours and the tracer uptake expressed as T/M. Conclusion: Our results indicate that, despite its rapid metabolism, [18F]FBA-FALGEA-NH2 binds preferentially to EGFRvIII in the tumours in vivo and is a promising lead for further development of EGFRvIII specific peptide radiopharmaceuticals.
U2 - 10.1016/j.nucmedbio.2010.11.003
DO - 10.1016/j.nucmedbio.2010.11.003
M3 - Journal article
C2 - 21531288
SN - 0969-8051
VL - 38
SP - 509
EP - 515
JO - Nuclear Medicine and Biology
JF - Nuclear Medicine and Biology
IS - 4
ER -
