title: Internalisation enhances photo-induced cytotoxicity of monoclonal antibody-phthalocyanine conjugates.
abstract: Immunophototherapy of cancer combines the specificity of a monoclonal antibody (MAb) to an overexpressed tumor marker with the phototoxic properties of the conjugated dye. To analyze the potential role of internalisation of the dye on photo-induced cytotoxicity, we compared two target antigens, carcinoembryonic antigen (CEA) that does not internalise and ErbB2 that does. Human ovarian carcinoma SKOv3 cells that express a high level of ErbB2 were transfected with the CEA cDNA. Using FACS analysis, the resulting cell line, SKOv3-CEA-1B9, demonstrated comparable levels of expression of the two target antigens. Aluminium tetrasulfophthalocyanine (AlPcS(4)) was covalently coupled to anti-CEA MAb 35A7, anti-ErbB2 MAb FSP77 and a non-specific MAb PX, via a five-carbon sulfonamide spacer chain (A(1)) at molar ratios ranging from 6 to 9 moles of AlPcS(4) per mole of MAb. The 35A7-(AlPcS(4)A(1))(8) conjugate induced 68% growth inhibition of the SKOv3-CEA-1B9 cell line after a 20 h incubation at 2.50 microg/ml (based on AlPcS(4)A(1) content) following light exposure. However, the FSP77-(AlPcS(4)A(1))(6) conjugate gave a 51% growth inhibition for an AlPcS(4)A(1) concentration as low as 0.04 microg/ml after the same incubation time and exposure to the same light dose. At a 1.25 microg/ml AlPcS(4)A(1) concentration, the FSP77-(AlPcS(4)A(1))(6) conjugate gave a 67% growth inhibition after an incubation time as short as 1 h, reaching a 96% inhibition after an 8 h incubation time. Using an unique cell line that expresses two different target antigens, we demonstrated a clear advantage of an internalising over a non-internalising MAb-dye conjugate in terms of phototoxic efficacy. In vivo evaluation of the photodynamic properties of the conjugates is in progress.
authors.affiliation: EA2989 Centre de Recherche en Cancérologie, CRLC Val d'Aurelle-Paul Lamarque, Montpellier, F-34298 cedex 5, France.
authors.forename: M
authors.initials: M
authors.lastname: Carcenac
authors.forename: M
authors.initials: M
authors.lastname: Dorvillius
authors.forename: V
authors.initials: V
authors.lastname: Garambois
authors.forename: F
authors.initials: F
authors.lastname: Glaussel
authors.forename: C
authors.initials: C
authors.lastname: Larroque
authors.forename: R
authors.initials: R
authors.lastname: Langlois
authors.forename: N E
authors.initials: NE
authors.lastname: Hynes
authors.forename: J E
authors.initials: JE
authors.lastname: van Lier
authors.forename: A
authors.initials: A
authors.lastname: Pèlegrin
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000493:pharmacokinetics*; D002272:Carcinoembryonic Antigen / Q000235:genetics / Q000276:immunology; D002455:Cell Division / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004705:Endocytosis; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007211:Indoles / Q000737:chemistry / Q000493:pharmacokinetics*; D008027:Light; D009942:Organometallic Compounds / Q000737:chemistry / Q000493:pharmacokinetics*; D010957:Plasmids / Q000235:genetics; D011838:Radiation-Sensitizing Agents / Q000737:chemistry / Q000493:pharmacokinetics*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000276:immunology; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D002272:Carcinoembryonic Antigen; D007211:Indoles; D009942:Organometallic Compounds; D011838:Radiation-Sensitizing Agents; D018719:Erb-b2 Receptor Tyrosine Kinases; C060570:aluminum phthalocyanine