title: Early Prediction of Tumor Response to Treatment: Preclinical Validation of 99mTc-Duramycin.
abstract: Noninvasive imaging of cell death can provide an early indication of the efficacy of tumor treatment, aiding clinicians in distinguishing responding patients from nonresponding patients early on. (99m)Tc-duramycin is a SPECT tracer for cell death imaging. In this study, our aim was to validate the use of (99m)Tc-duramycin for imaging the early response of tumors to treatment.
  
  
  
  An in vitro binding assay was performed on COLO205 cells treated with 5-fluorouracil (3.1, 31, or 310 μM) and oxaliplatin (0.7 or 7 μM) or radiation (2 or 4.5 Gy). (99m)Tc-duramycin cell binding and the levels of cell death were evaluated after treatment. In vivo imaging was performed on 4 groups of CD1-deficient mice bearing COLO205 human colorectal cancer tumors. Each group included 6 tumors. The first group was given irinotecan (100 mg/kg), the second oxaliplatin (5 mg/kg), the third irinotecan (80 mg/kg) plus oxaliplatin (5 mg/kg), and the fourth vehicle (0.9% NaCl and 5% glucose). For radiotherapy studies, COLO205 tumors received 4.5 Gy, 2 fractions of 4.5 Gy in a 24-h interval, pretreatment with an 80 mg/kg dose of irinotecan combined with 2 fractions of 4.5 Gy in a 24-h interval, or no treatment (n = 5-6/group). Therapy response was evaluated by (99m)Tc-duramycin SPECT 24 h after the last dose of therapy. Blocking was used to confirm tracer specificity. Radiotracer uptake in the tumors was validated ex vivo using γ-counting, cleaved caspase-3, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) histology.
  
  
  
  Chemotherapy and radiotherapy increased (99m)Tc-duramycin binding to COLO205 cells in a concentration/dose- and time-dependent manner, which correlated well with cell death levels (P < 0.05) as analyzed by annexin V and caspase 3/7 activity. In vivo, (99m)Tc-duramycin uptake in COLO205 xenografts was increased 2.3- and 2.8-fold (P < 0.001) in mice treated with irinotecan and combination therapy, respectively. Blocking with unlabeled duramycin demonstrated specific binding of the radiotracer. After tumor irradiation with 4.5 Gy, (99m)Tc-duramycin uptake in tumors increased significantly (1.24 ± 0.07 vs. 0.57 ± 0.08 percentage injected dose per gram in the unirradiated tumors; P < 0.001). γ-counting of radioactivity in the tumors positively correlated with cleaved caspase-3 (r = 0.85, P < 0.001) and TUNEL (r = 0.81, P < 0.001) staining.
  
  
  
  We demonstrated that (99m)Tc-duramycin can be used to image induction of cell death early after chemotherapy and radiotherapy. It holds potential to be translated into clinical use for early assessment of treatment response.
authors.affiliation: Molecular Imaging Center Antwerp, University of Antwerp, Wilrijk, Belgium Department of Nuclear Medicine, University Hospital Antwerp, Edegem, Belgium leonie.wyffels@uza.be filipe.elvas@uantwerpen.be.
authors.forename: Filipe
authors.initials: F
authors.lastname: Elvas
authors.affiliation: Molecular Imaging Center Antwerp, University of Antwerp, Wilrijk, Belgium Department of Nuclear Medicine, University Hospital Antwerp, Edegem, Belgium.
authors.forename: Christel
authors.initials: C
authors.lastname: Vangestel
authors.affiliation: Molecular Targeting Technologies, Inc., West Chester, Pennsylvania; and.
authors.forename: Koon
authors.initials: K
authors.lastname: Pak
authors.affiliation: Laboratory of Pathology, General Hospital Sint-Augustinus, Antwerp, Belgium.
authors.forename: Peter
authors.initials: P
authors.lastname: Vermeulen
authors.affiliation: Molecular Targeting Technologies, Inc., West Chester, Pennsylvania; and.
authors.forename: Brian
authors.initials: B
authors.lastname: Gray
authors.affiliation: Molecular Imaging Center Antwerp, University of Antwerp, Wilrijk, Belgium Department of Nuclear Medicine, University Hospital Antwerp, Edegem, Belgium.
authors.forename: Sigrid
authors.initials: S
authors.lastname: Stroobants
authors.affiliation: Molecular Imaging Center Antwerp, University of Antwerp, Wilrijk, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Staelens
authors.affiliation: Molecular Imaging Center Antwerp, University of Antwerp, Wilrijk, Belgium Department of Nuclear Medicine, University Hospital Antwerp, Edegem, Belgium leonie.wyffels@uza.be filipe.elvas@uantwerpen.be.
authors.forename: Leonie
authors.initials: L
authors.lastname: Wyffels
mesh_terms: D000818:Animals; D001430:Bacteriocins / Q000378:metabolism; D001692:Biological Transport; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000378:metabolism; D005260:Female; D005472:Fluorouracil / Q000494:pharmacology / Q000627:therapeutic use; D006801:Humans; D051379:Mice; D009944:Organoplatinum Compounds / Q000494:pharmacology / Q000627:therapeutic use; D015609:Organotechnetium Compounds / Q000378:metabolism; D000077150:Oxaliplatin; D000072098:Single Photon Emission Computed Tomography Computed Tomography; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D001430:Bacteriocins; D009944:Organoplatinum Compounds; D015609:Organotechnetium Compounds; C578182:technetium 99m HYNIC-duramycin; D000077150:Oxaliplatin; D005472:Fluorouracil
keywords: 99mTc-duramycin; SPECT imaging; cell death; chemotherapy; radiotherapy