title: Photochemically stimulated drug delivery increases the cytotoxicity and specificity of EGF-saporin.
abstract: Epidermal growth factor receptor (EGFR) targeting has become a major field in both cancer research and therapy. In the present study an EGF-saporin affinity toxin has been established and evaluated in two EGFR overexpressing cancer cell lines. The binding of saporin to EGF did not influence the ribosome-inactivating activity of saporin as measured by a luminescence based reticulocyte lysate assay. Control experiments, using untargeted saporin, EGFR-negative cell lines and competition with EGF and anti-EGFR antibody were used to document selective uptake of the affinity toxin. One limitation in administration of macromolecular-drugs is lysosomal degradation. Photochemical internalization (PCI) is a modality for cytosolic release of macromolecules based on photochemical rupture of endocytic membranes and subsequent drug release. It was shown that PCI increases the toxicity of EGF-saporin significantly in EGFR-positive cells. EGF binding to saporin enhanced the PCI-induced cytotoxicity in NuTu-19 cells about 1000-fold when the photochemical treatment alone killed 50% of the cells. In conclusion, PCI of EGF-saporin is a promising method for increasing the efficiency of protein toxin-based cancer therapies. PCI of targeting toxins also exert a triple tumour-selectivity; utilization of an affinity toxin, preferential accumulation of the photosensitizer in neoplastic lesions, and site-directed light activation.
authors.affiliation: Department of Radiation Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway. anettewe@medisin.uio.no
authors.forename: Anette
authors.initials: A
authors.lastname: Weyergang
authors.forename: Pål Kristian
authors.initials: PK
authors.lastname: Selbo
authors.forename: Kristian
authors.initials: K
authors.lastname: Berg
mesh_terms: D000818:Animals; D001710:Biotin / Q000737:chemistry; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004815:Epidermal Growth Factor / Q000737:chemistry / Q000494:pharmacology*; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D000922:Immunotoxins / Q000737:chemistry / Q000494:pharmacology*; D008856:Microscopy, Fluorescence; D011500:Protein Synthesis Inhibitors / Q000737:chemistry / Q000494:pharmacology; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism; D019809:Streptavidin / Q000737:chemistry; D013997:Time Factors
chemical_list: D000922:Immunotoxins; D011500:Protein Synthesis Inhibitors; D004815:Epidermal Growth Factor; D001710:Biotin; D019809:Streptavidin; D066246:ErbB Receptors