title: Multi-modality therapeutics with potent anti-tumor effects: photochemical internalization enhances delivery of the fusion toxin scFvMEL/rGel.
abstract: BACKGROUND
  There is a need for drug delivery systems (DDS) that can enhance cytosolic delivery of anti-cancer drugs trapped in the endo-lysosomal compartments. Exposure of cells to specific photosensitizers followed by light exposure (photochemical internalization, PCI) results in transfer of agents from the endocytic compartment into the cytosol.
  
  
  RESULTS
  The recombinant single-chain fusion construct scFvMEL/rGel is composed of an antibody targeting the progenitor marker HMW-MAA/NG2/MGP/gp240 and the highly effective toxin gelonin (rGel). Here we demonstrate enhanced tumor cell selectivity, cytosolic delivery and anti-tumor activity by applying PCI of scFvMEL/rGel. PCI performed by light activation of cells co-incubated with scFvMEL/rGel and the endo-lysosomal targeting photosensitizers AlPcS(2a) or TPPS(2a) resulted in enhanced cytotoxic effects against antigen-positive cell lines, while no differences in cytotoxicity between the scFvMEL/rGel and rGel were observed in antigen-negative cells. Mice bearing well-developed melanoma (A-375) xenografts (50-100 mm(3)) were treated with PCI of scFvMEL/rGel. By 30 days after injection, approximately 100% of mice in the control groups had tumors>800 mm(3). In contrast, by day 40, 50% of mice in the PCI of scFvMEL/rGel combination group had tumors<800 mm(3) with no increase in tumor size up to 110 days. PCI of scFvMEL/rGel resulted in a synergistic effect (p<0.05) and complete regression (CR) in 33% of tumor-bearing mice (n = 12).
  
  
  CONCLUSIONS
  This is a unique demonstration that a non-invasive multi-modality approach combining a recombinant, targeted therapeutic such as scFvMEL/rGel and PCI act in concert to provide potent in vivo efficacy without sacrificing selectivity or enhancing toxicity. The present DDS warrants further evaluation of its clinical potential.
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway. selbo@rr-research.no
authors.forename: Pål K
authors.initials: PK
authors.lastname: Selbo
authors.forename: Michael G
authors.initials: MG
authors.lastname: Rosenblum
authors.forename: Lawrence H
authors.initials: LH
authors.lastname: Cheung
authors.forename: Wendy
authors.initials: W
authors.lastname: Zhang
authors.forename: Kristian
authors.initials: K
authors.lastname: Berg
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D045744:Cell Line, Tumor; D016503:Drug Delivery Systems; D005260:Female; D006801:Humans; D007128:Immunoglobulin Fragments / Q000008:administration & dosage*; D000922:Immunotoxins / Q000008:administration & dosage* / Q000627:therapeutic use; D051379:Mice; D008807:Mice, Inbred BALB C; D010777:Photochemistry; D011993:Recombinant Fusion Proteins / Q000008:administration & dosage* / Q000627:therapeutic use
chemical_list: D000970:Antineoplastic Agents; D007128:Immunoglobulin Fragments; D000922:Immunotoxins; D011993:Recombinant Fusion Proteins
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