title: Monitoring Cell Death in Regorafenib-Treated Experimental Colon Carcinomas Using Annexin-Based Optical Fluorescence Imaging Validated by Perfusion MRI.
abstract: OBJECTIVE
  To investigate annexin-based optical fluorescence imaging (OI) for monitoring regorafenib-induced early cell death in experimental colon carcinomas in rats, validated by perfusion MRI and multiparametric immunohistochemistry.
  
  
  METHODS
  Subcutaneous human colon carcinomas (HT-29) in athymic rats (n = 16) were imaged before and after a one-week therapy with regorafenib (n = 8) or placebo (n = 8) using annexin-based OI and perfusion MRI at 3 Tesla. Optical signal-to-noise ratio (SNR) and MRI tumor perfusion parameters (plasma flow PF, mL/100mL/min; plasma volume PV, %) were assessed. On day 7, tumors underwent immunohistochemical analysis for tumor cell apoptosis (TUNEL), proliferation (Ki-67), and microvascular density (CD31).
  
  
  RESULTS
  Apoptosis-targeted OI demonstrated a tumor-specific probe accumulation with a significant increase of tumor SNR under therapy (mean Δ +7.78±2.95, control: -0.80±2.48, p = 0.021). MRI detected a significant reduction of tumor perfusion in the therapy group (mean ΔPF -8.17±2.32 mL/100 mL/min, control -0.11±3.36 mL/100 mL/min, p = 0.036). Immunohistochemistry showed significantly more apoptosis (TUNEL; 11392±1486 vs. 2921±334, p = 0.001), significantly less proliferation (Ki-67; 1754±184 vs. 2883±323, p = 0.012), and significantly lower microvascular density (CD31; 107±10 vs. 182±22, p = 0.006) in the therapy group.
  
  
  CONCLUSIONS
  Annexin-based OI allowed for the non-invasive monitoring of regorafenib-induced early cell death in experimental colon carcinomas, validated by perfusion MRI and multiparametric immunohistochemistry.
authors.affiliation: Institute for Clinical Radiology, Laboratory for Experimental Radiology, Ludwig-Maximilians-University Hospital Munich, München, Germany.
authors.forename: Philipp M
authors.initials: PM
authors.lastname: Kazmierczak
authors.affiliation: Institute for Clinical Radiology, Laboratory for Experimental Radiology, Ludwig-Maximilians-University Hospital Munich, München, Germany.
authors.forename: Egon
authors.initials: E
authors.lastname: Burian
authors.affiliation: Institute for Clinical Radiology, Laboratory for Experimental Radiology, Ludwig-Maximilians-University Hospital Munich, München, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Eschbach
authors.affiliation: Institute for Clinical Radiology, Laboratory for Experimental Radiology, Ludwig-Maximilians-University Hospital Munich, München, Germany.
authors.forename: Heidrun
authors.initials: H
authors.lastname: Hirner-Eppeneder
authors.affiliation: Institute for Clinical Radiology, Laboratory for Experimental Radiology, Ludwig-Maximilians-University Hospital Munich, München, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Moser
authors.affiliation: Institute for Clinical Radiology, Josef-Lissner-Laboratory for Biomedical Imaging, Ludwig-Maximilians-University Hospital Munich, München, Germany.
authors.forename: Lukas
authors.initials: L
authors.lastname: Havla
authors.affiliation: Department of Clinical Radiology, University Hospital Münster, Münster, Germany; Comprehensive Cancer Imaging Centre, Division of Imaging Sciences & Biomedical Engineering, King's College London, United Kingdom.
authors.forename: Michel
authors.initials: M
authors.lastname: Eisenblätter
authors.affiliation: Institute for Clinical Radiology, Laboratory for Experimental Radiology, Ludwig-Maximilians-University Hospital Munich, München, Germany.
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.affiliation: Institute for Clinical Radiology, Laboratory for Experimental Radiology, Ludwig-Maximilians-University Hospital Munich, München, Germany; Department of Diagnostic and Interventional Radiology, University Hospital Tübingen, Tübingen, Germany.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Nikolaou
authors.affiliation: Institute for Clinical Radiology, Laboratory for Experimental Radiology, Ludwig-Maximilians-University Hospital Munich, München, Germany.
authors.forename: Clemens C
authors.initials: CC
authors.lastname: Cyran
mesh_terms: D000818:Animals; D017302:Annexins / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects; D014408:Biomarkers, Tumor / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D019073:HT29 Cells; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D061848:Optical Imaging; D010671:Phenylurea Compounds / Q000627:therapeutic use* / Q000633:toxicity; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D011725:Pyridines / Q000627:therapeutic use* / Q000633:toxicity; D051381:Rats; D011923:Rats, Nude; D059629:Signal-To-Noise Ratio; D014183:Transplantation, Heterologous
chemical_list: D017302:Annexins; D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen; D010671:Phenylurea Compounds; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D011725:Pyridines; C559147:regorafenib