title: ImmunoPET of tissue factor expression in triple-negative breast cancer with a radiolabeled antibody Fab fragment.
abstract: OBJECTIVE
  To date, there is no effective therapy for triple-negative breast cancer (TNBC), which has a dismal clinical outcome. Upregulation of tissue factor (TF) expression leads to increased patient morbidity and mortality in many solid tumor types, including TNBC. Our goal was to employ the Fab fragment of ALT-836, a chimeric anti-human TF mAb, for PET imaging of TNBC, which can be used to guide future TNBC therapy.
  
  
  METHODS
  ALT-836-Fab was generated by enzymatic papain digestion. SDS-PAGE and FACS studies were performed to evaluate the integrity and TF binding affinity of ALT-836-Fab before NOTA conjugation and (64)Cu-labeling. Serial PET imaging and biodistribution studies were carried out to evaluate the tumor targeting efficacy and pharmacokinetics in the MDA-MB-231 TNBC model, which expresses high levels of TF on the tumor cells. Blocking studies, histological assessment, as well as RT-PCR were performed to confirm TF specificity of (64)Cu-NOTA-ALT-836-Fab.
  
  
  RESULTS
  ALT-836-Fab was produced with high purity, which exhibited superb TF binding affinity and specificity. Serial PET imaging revealed rapid and persistent tumor uptake of (64)Cu-NOTA-ALT-836-Fab (5.1 ± 0.5 %ID/g at 24 h post-injection; n = 4) and high tumor/muscle ratio (7.0 ± 1.2 at 24 h post-injection; n = 4), several-fold higher than that of the blocking group and tumor models that do not express significant level of TF, which was confirmed by biodistribution studies. TF specificity of the tracer was also validated by histology and RT-PCR.
  
  
  CONCLUSIONS
  (64)Cu-NOTA-ALT-836-Fab exhibited prominent tissue factor targeting efficiency in MDA-MB-231 TNBC model. The use of a Fab fragment led to fast tumor uptake and good tissue/muscle ratio, which may be translated into same-day immunoPET imaging in the clinical setting to improve TNBC patient management.
authors: Materials Science Program, University of Wisconsin, Madison, WI, USA.
authors: Sixiang
authors: S
authors: Shi
authors: Hao
authors: H
authors: Hong
authors: Hakan
authors: H
authors: Orbay
authors: Stephen A
authors: SA
authors: Graves
authors: Yunan
authors: Y
authors: Yang
authors: Jakob D
authors: JD
authors: Ohman
authors: Bai
authors: B
authors: Liu
authors: Robert J
authors: RJ
authors: Nickles
authors: Hing C
authors: HC
authors: Wong
authors: Weibo
authors: W
authors: Cai
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003301:Copper Radioisotopes / Q000737:chemistry; D005260:Female; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry / Q000276:immunology / Q000494:pharmacology*; D008325:Mammary Neoplasms, Experimental / Q000000981:diagnostic imaging*; D051379:Mice; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000493:pharmacokinetics*; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics*; D013925:Thromboplastin / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D014018:Tissue Distribution; D064726:Triple Negative Breast Neoplasms / Q000000981:diagnostic imaging*
chemical_list: C000606142:64Cu-NOTA-ALT-836-Fab; D003301:Copper Radioisotopes; D007140:Immunoglobulin Fab Fragments; D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; D013925:Thromboplastin