title: Development and characterization of novel photosensitizer : scFv conjugates for use in photodynamic therapy of cancer.
abstract: Photodynamic therapy (PDT) is becoming an evermore useful tool in oncology but is frequently limited by side-effects caused by a lack of targeting of the photosensitizer. This problem can often be circumvented by the conjugation of photosensitizers to tumour-specific monoclonal antibodies. An alternative is the use of single chain (sc) Fv fragments which, whilst retaining the same binding specificity, are more efficient at penetrating tumour masses because of their smaller size; and are more effectively cleared from the circulation because of the lack of an Fc domain. Here we describe the conjugation of two isothiocyanato porphyrins to colorectal tumour-specific scFv, derived from an antibody phage display library. The conjugation procedure was successfully optimized and the resulting immunoconjugates showed no loss of cell binding. In vitro assays against colorectal cell lines showed these conjugates had a selective photocytotoxic effect on cells. Annexin V and propidium iodide staining of treated cells confirmed cell death was mediated principally via an apoptotic pathway. This work suggests that scFv : porphyrin conjugates prepared using isothiocyanato porphyrins show promise for use as targeted PDT agents.
authors.affiliation: Postgraduate Medical Institute, University of Hull, Hull, UK.
authors.forename: Chrysovalanto
authors.initials: C
authors.lastname: Staneloudi
authors.forename: Karen A
authors.initials: KA
authors.lastname: Smith
authors.forename: Robert
authors.initials: R
authors.lastname: Hudson
authors.forename: Nela
authors.initials: N
authors.lastname: Malatesti
authors.forename: Huguette
authors.initials: H
authors.lastname: Savoie
authors.forename: Ross W
authors.initials: RW
authors.lastname: Boyle
authors.forename: John
authors.initials: J
authors.lastname: Greenman
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D018938:Caco-2 Cells; D049109:Cell Proliferation / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000473:pathology*; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D006801:Humans; D018796:Immunoconjugates / Q000494:pharmacology*; D007135:Immunoglobulin Variable Region / Q000378:metabolism / Q000494:pharmacology*; D019151:Peptide Library; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011166:Porphyrins / Q000494:pharmacology
chemical_list: D018796:Immunoconjugates; D007135:Immunoglobulin Variable Region; D019151:Peptide Library; D017319:Photosensitizing Agents; D011166:Porphyrins