title: Ratiometric activatable cell-penetrating peptides label pancreatic cancer, enabling fluorescence-guided surgery, which reduces metastases and recurrence in orthotopic mouse models.
abstract: BACKGROUND
  The aim of this study was to evaluate the efficacy of using matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9)-cleavable ratiometric activatable cell-penetrating peptides (RACPPs) conjugated to Cy5 and Cy7 fluorophores to accurately label pancreatic cancer for fluorescence-guided surgery (FGS) in an orthotopic mouse model.
  
  
  METHODS
  Orthotopic mouse models were established using MiaPaCa-2-GFP human pancreatic cancer cells. Two weeks after implantation, tumor-bearing mice were randomized to conventional white light reflectance (WLR) surgery or FGS. FGS was performed at far-red and infrared wavelengths with a customized fluorescence-dissecting microscope 2 h after injection of MMP-2 and MMP-9-cleavable RACPPs. Green fluorescence imaging of the GFP-labeled cancer cells was used to assess the effectiveness of surgical resection and monitor recurrence. At 8 weeks, mice were sacrificed to evaluate tumor burden and metastases.
  
  
  RESULTS
  Mice in the WLR group had larger primary tumors than mice in the FGS group at termination [1.72 g ± standard error (SE) 0.58 vs. 0.25 g ± SE 0.14; respectively, p = 0.026). Mean disease-free survival was significantly lengthened from 5.33 weeks in the WLR group to 7.38 weeks in the FGS group (p = 0.02). Recurrence rates were lower in the FGS group than in the WLR group (38 vs. 73 %; p = 0.049). This translated into lower local and distant recurrence rates for FGS compared to WLR (31 vs. 67 for local recurrence, respectively, and 25 vs. 60 % for distant recurrence, respectively). Metastatic tumor burden was significantly greater in the WLR group than in the FGS group (96.92 mm(2) ± SE 52.03 vs. 2.20 mm(2) ± SE 1.43; respectively, χ (2) = 5.455; p = 0.02).
  
  
  CONCLUSIONS
  RACPPs can accurately and effectively label pancreatic cancer for effective FGS, resulting in better postresection outcomes than for WLR surgery.
authors.affiliation: Department of Surgery, University of California San Diego, San Diego, CA, USA.
authors.forename: Cristina A
authors.initials: CA
authors.lastname: Metildi
authors.forename: Csilla N
authors.initials: CN
authors.lastname: Felsen
authors.forename: Elamprakash N
authors.initials: EN
authors.lastname: Savariar
authors.forename: Quyen T
authors.initials: QT
authors.lastname: Nguyen
authors.forename: Sharmeela
authors.initials: S
authors.lastname: Kaushal
authors.forename: Robert M
authors.initials: RM
authors.lastname: Hoffman
authors.forename: Roger Y
authors.initials: RY
authors.lastname: Tsien
authors.forename: Michael
authors.initials: M
authors.lastname: Bouvet
mesh_terms: D000818:Animals; D057846:Cell-Penetrating Peptides / Q000008:administration & dosage* / Q000378:metabolism; D005260:Female; D005453:Fluorescence; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D020778:Matrix Metalloproteinase 2 / Q000737:chemistry / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D008856:Microscopy, Fluorescence; D009362:Neoplasm Metastasis; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control*; D061848:Optical Imaging / Q000379:methods; D010190:Pancreatic Neoplasms / Q000473:pathology* / Q000601:surgery*; D025321:Surgery, Computer-Assisted; D047368:Tumor Burden
chemical_list: D057846:Cell-Penetrating Peptides; D049452:Green Fluorescent Proteins; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9