title: Targeted photodestruction of human colon cancer cells using charged 17.1A chlorin e6 immunoconjugates.
abstract: The goal of this study was to develop a strategy for the selective destruction of colorectal cancer cells. Towards this end, photoimmunoconjugates were prepared between the anti-colon cancer monoclonal antibody 17.1A and the photosensitizer (PS) chlorin(e6) (c(e6)). Polylysine linkers bearing several c(e6) molecules were covalently attached in a site-specific manner to partially reduced IgG molecules, which allowed photoimmunoconjugates to bear either cationic or anionic charges. The conjugates retained immunoreactivity as shown by enzyme-linked immunosorbent assays and by competition studies with native antibody. The overall charge on the photoimmunoconjugate was an important determinant of PS delivery. The cationic photoimmunoconjugate delivered 4 times more c(e6) to the cells than the anionic photoimmunoconjugate, and both 17.1A conjugates showed, in comparison to non-specific rabbit IgG conjugates, selectivity for antigen-positive target cells. Illumination with only 3 J cm(-2) of 666 nm light reduced the number of colony forming cells by more than 90% for the cationic 17.1A conjugate and by 73% for the anionic 17.1A conjugate after incubation with 1 microM c(e6) equivalent of the respective conjugates. By contrast, 1 microM free c(e6) gave only a 35% reduction in colonies. These data suggest photoimmunoconjugates may have applications in photoimmunotherapy where destruction of colorectal cancer cells is required.
authors.affiliation: Department of Dermatology, Massachusetts General Hospital, Harvard Medical School, Boston 02114, USA.
authors.forename: M
authors.initials: M
authors.lastname: Del Governatore
authors.forename: M R
authors.initials: MR
authors.lastname: Hamblin
authors.forename: E E
authors.initials: EE
authors.lastname: Piccinini
authors.forename: G
authors.initials: G
authors.lastname: Ugolini
authors.forename: T
authors.initials: T
authors.lastname: Hasan
mesh_terms: D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics / Q000627:therapeutic use*; D001667:Binding, Competitive; D002735:Chlorophyllides; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D019085:Fluorescent Antibody Technique, Direct; D019084:Fluorescent Antibody Technique, Indirect; D019073:HT29 Cells; D006801:Humans; D018796:Immunoconjugates / Q000493:pharmacokinetics / Q000627:therapeutic use*; D007074:Immunoglobulin G / Q000378:metabolism / Q000627:therapeutic use*; D008856:Microscopy, Fluorescence; D010778:Photochemotherapy / Q000379:methods*; D011166:Porphyrins / Q000493:pharmacokinetics / Q000627:therapeutic use*; D011838:Radiation-Sensitizing Agents / Q000493:pharmacokinetics / Q000627:therapeutic use*; D013696:Temperature
chemical_list: D000911:Antibodies, Monoclonal; D002735:Chlorophyllides; D018796:Immunoconjugates; D007074:Immunoglobulin G; D011166:Porphyrins; D011838:Radiation-Sensitizing Agents; C062985:phytochlorin